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WO2022017932A1 - Instrumented joint for robotic arm - Google Patents

Instrumented joint for robotic arm Download PDF

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Publication number
WO2022017932A1
WO2022017932A1 PCT/EP2021/069861 EP2021069861W WO2022017932A1 WO 2022017932 A1 WO2022017932 A1 WO 2022017932A1 EP 2021069861 W EP2021069861 W EP 2021069861W WO 2022017932 A1 WO2022017932 A1 WO 2022017932A1
Authority
WO
WIPO (PCT)
Prior art keywords
joint
robotic arm
articulation
guide system
parts
Prior art date
Application number
PCT/EP2021/069861
Other languages
French (fr)
Inventor
Jean-Paul Coron
Original Assignee
Coron Jean Paul
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Coron Jean Paul filed Critical Coron Jean Paul
Publication of WO2022017932A1 publication Critical patent/WO2022017932A1/en

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Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B25—HAND TOOLS; PORTABLE POWER-DRIVEN TOOLS; MANIPULATORS
    • B25J—MANIPULATORS; CHAMBERS PROVIDED WITH MANIPULATION DEVICES
    • B25J9/00—Programme-controlled manipulators
    • B25J9/10—Programme-controlled manipulators characterised by positioning means for manipulator elements
    • B25J9/12—Programme-controlled manipulators characterised by positioning means for manipulator elements electric
    • B25J9/126—Rotary actuators
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
    • F16C—SHAFTS; FLEXIBLE SHAFTS; ELEMENTS OR CRANKSHAFT MECHANISMS; ROTARY BODIES OTHER THAN GEARING ELEMENTS; BEARINGS
    • F16C19/00—Bearings with rolling contact, for exclusively rotary movement
    • F16C19/02—Bearings with rolling contact, for exclusively rotary movement with bearing balls essentially of the same size in one or more circular rows
    • F16C19/14—Bearings with rolling contact, for exclusively rotary movement with bearing balls essentially of the same size in one or more circular rows for both radial and axial load
    • F16C19/18—Bearings with rolling contact, for exclusively rotary movement with bearing balls essentially of the same size in one or more circular rows for both radial and axial load with two or more rows of balls
    • F16C19/181—Bearings with rolling contact, for exclusively rotary movement with bearing balls essentially of the same size in one or more circular rows for both radial and axial load with two or more rows of balls with angular contact
    • F16C19/183—Bearings with rolling contact, for exclusively rotary movement with bearing balls essentially of the same size in one or more circular rows for both radial and axial load with two or more rows of balls with angular contact with two rows at opposite angles
    • F16C19/184—Bearings with rolling contact, for exclusively rotary movement with bearing balls essentially of the same size in one or more circular rows for both radial and axial load with two or more rows of balls with angular contact with two rows at opposite angles in O-arrangement
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02K—DYNAMO-ELECTRIC MACHINES
    • H02K11/00—Structural association of dynamo-electric machines with electric components or with devices for shielding, monitoring or protection
    • H02K11/30—Structural association with control circuits or drive circuits
    • H02K11/33—Drive circuits, e.g. power electronics
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02K—DYNAMO-ELECTRIC MACHINES
    • H02K5/00—Casings; Enclosures; Supports
    • H02K5/04—Casings or enclosures characterised by the shape, form or construction thereof
    • H02K5/10—Casings or enclosures characterised by the shape, form or construction thereof with arrangements for protection from ingress, e.g. water or fingers
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02K—DYNAMO-ELECTRIC MACHINES
    • H02K7/00—Arrangements for handling mechanical energy structurally associated with dynamo-electric machines, e.g. structural association with mechanical driving motors or auxiliary dynamo-electric machines
    • H02K7/08—Structural association with bearings
    • H02K7/083—Structural association with bearings radially supporting the rotary shaft at both ends of the rotor
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02K—DYNAMO-ELECTRIC MACHINES
    • H02K7/00—Arrangements for handling mechanical energy structurally associated with dynamo-electric machines, e.g. structural association with mechanical driving motors or auxiliary dynamo-electric machines
    • H02K7/10—Structural association with clutches, brakes, gears, pulleys or mechanical starters
    • H02K7/102—Structural association with clutches, brakes, gears, pulleys or mechanical starters with friction brakes
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02K—DYNAMO-ELECTRIC MACHINES
    • H02K7/00—Arrangements for handling mechanical energy structurally associated with dynamo-electric machines, e.g. structural association with mechanical driving motors or auxiliary dynamo-electric machines
    • H02K7/10—Structural association with clutches, brakes, gears, pulleys or mechanical starters
    • H02K7/116—Structural association with clutches, brakes, gears, pulleys or mechanical starters with gears
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
    • F16C—SHAFTS; FLEXIBLE SHAFTS; ELEMENTS OR CRANKSHAFT MECHANISMS; ROTARY BODIES OTHER THAN GEARING ELEMENTS; BEARINGS
    • F16C2380/00—Electrical apparatus
    • F16C2380/26—Dynamo-electric machines or combinations therewith, e.g. electro-motors and generators

Definitions

  • the present invention relates to the field of articulated robotic arms, and more particularly to the field of instrumented and motorized joints of these arms.
  • One of the quantities to be measured in the field of articulated robotic arms is in particular the force to which the arm is subjected.
  • This effort can be for example the weight of a load that the arm would have grasped by means of a gripper arranged at its end.
  • This force can also come from the collision of a part of the articulated robotic arm with an element of its environment.
  • This element can be a mechanical element, fixed or mobile, present close to the installation of the articulated robotic arm, for example a second articulated arm which would perform other tasks.
  • This colliding element can also be a person, in particular in the specific case of “cobots”, which are robots intended to work in collaboration with a person, therefore in close proximity with the latter.
  • strain gauges known by other names such as “strain gauges” or “force sensor”. Indeed these deformation gauges, placed on the surface of a part subjected to a force, are able to measure the deformations that said part undergoes under load. By calculation, we are able to know what is the effort that said part undergoes. Nevertheless, these gauges must be placed judiciously on the part to give a measurement that is usable. Indeed, these gauges measure a deformation and this is not identical everywhere on the part, in particular according to its assembly, for example in an assembly: the deformation will be zero in the direction or directions blocked by this assembly. Obviously, at the level of an embedding connection blocking the six degrees of freedom, no deformation of the part is possible.
  • an instrumented joint for a robotic arm has been developed in accordance with that of the state of the art in that it includes:
  • the first part of the joint being extended in one piece, at its center, by a hollow cylindrical shape passing through, at its center, the second part, the first part is guided in rotation around a general axis of revolution of the articulation with respect to the second part thanks to a first guiding system,
  • the motor comprising a stator coupled to the first part, and a rotor coupled to a hollow central shaft of the reducer.
  • the joint comprises:
  • At least one strain gauge mounted on the first or the second part, and connected to an electronic card.
  • the first system for guiding in rotation between the first part and the second part is of any suitable type, such as a ball or roller bearing, or an angular contact bearing, the assembly of which makes it possible to obtain a rigidity greater than with radial contact bearings.
  • a ball or roller bearing or an angular contact bearing, the assembly of which makes it possible to obtain a rigidity greater than with radial contact bearings.
  • it may have internal clearance (axial or angular). This clearance can be limited by subjecting the first guidance system to a pre-load, but this should not be excessive since it could reduce the life of the first guidance system.
  • this first guidance system has its own rigidity which is not infinite, so the system deforms when the robotic arm is subjected to a load.
  • This load can be, for example, the weight of an object manipulated by the arm, or a dynamic force when the arm makes accelerations or decelerations in its movements.
  • This deformation is nevertheless located at the level of the assembly of the first guidance system, and is not measurable at its level because the size of the assembly is too great.
  • the proper functioning of the first guidance system generally requires the presence of lubricant which prevents the easy placement of strain gauges which are typically wired sensors, the wiring of these sensors preventing the proper sealing necessary to prevent the leakage of said lubricant.
  • the first guidance system between the first and the second part is generally located close to the first part, and is therefore not a judicious place to measure the forces to which the second part of the arm is subjected, because this place in is too far away.
  • Adding a second guidance system, which is hyperstatic relative to the first guidance system, makes it possible to significantly increase the rigidity of the rotational guidance of the first part relative to the second part.
  • this second guide system is swiveling, and is mounted between the two main hubs, respectively of the first part and of the second part, the assembly thus obtained therefore makes it possible to orient the deformation due to the loads at the level of the second part, rather than letting it occur at the level of the first guidance system.
  • the location of the deformation being thus controlled, it becomes possible to place the deformation gauges on a deformation zone of the first part or of the second part, so that they are effective in that their measurement makes it possible to to have information, in particular redundant, precise and undisturbed of the efforts to which the second part is subjected.
  • the strain gauge(s) As the second part is directly attached to the engine, it is very relevant to place the strain gauge(s) on it so that they give relevant information on the forces to which the arm is subjected.
  • the second guidance system is preferably offset relative to the first guidance system along the axis relative to the first guidance system.
  • the rigidity gained by the hyperstatic assembly is improved. It also emerges that the joint is more balanced, the first guidance system being placed, for example, plumb or close to the first part of the joint. Shifting the second guidance system therefore makes it possible to obtain an articulation that is better able to absorb the forces inherent in the use of the articulated robotic arm.
  • the first guide system is preferably a ball bearing. This solution has the advantage of being compact, in particular if it is a bearing with two rows of contact balls oblique.
  • the first guidance system can also be an assembly of several bearings, whether ball bearings or crossed rollers, with oblique and radial contacts.
  • the second guide system is preferably a ball bearing.
  • Other technical solutions can of course be considered, such as radial spherical bearings or spherical roller bearings.
  • a radial ball joint is an assembly of two rings including an outer ring with a concave and spherical inner face, and an inner ring with a complementary convex and spherical outer face. The two rings are mounted one inside the other so that the spherical faces cooperate together. To facilitate the assembly of one ring in the other, one of the rings can be in two parts, preferably the outer ring. Radial ball joints make it possible to obtain ball-and-socket guidance while having a small radial size.
  • the robotic arm joint also comprises means for measuring the angle between the first and second parts.
  • These measuring means are for example encoders, ideally an optical encoder and a magnetic encoder, each measuring the angular displacement of the rotor relative to the stator.
  • encoders which measure the angular position of the rotor relative to the stator in a redundant manner, but being based on different technologies, makes it possible to guarantee the reliability necessary for piloting and controlling the robotized system.
  • These encoders are connected to the electronic board so that the latter can process their signals.
  • the robotic arm joint also comprises means for braking the pivoting of the first part relative to the second part, such as a disc brake.
  • a brake compared to other position holding systems, for example based on indexing devices cooperating with a star, is that the brake does not have an indexed angular position, it is that is, it can lock at any angular position between the two parts of the articulated robotic arm.
  • the index devices are them, by definition, subject to angular positions which are those of the arms of the star used. Depending on the star used, there may therefore be a limited number of positions available.
  • this solution can allow the relative movement of the two parts over a residual angular range corresponding to the spacing between two successive arms of the star.
  • the arms of the spider and the index being subjected to shocks during emergency stops, the life of these systems is generally short because the parts deteriorate.
  • the kinetic energy to be dissipated during emergency stops occurs thermally, resulting from friction between the brake linings and the disc, which is less penalizing for the mechanics.
  • the use of a brake in the technical field of articulated robotic arms is therefore particularly sensible.
  • the joint is made up of two parts mounted as a pivot joint with respect to each other.
  • the second part comprises at least one cylindrical bearing surface (or respectively a bore) which fits during assembly of the joint in at least one cylindrical bore (or respectively a bearing surface) complementary to the first part , optionally via the first and second guidance systems, so that the first part can accommodate the second part.
  • the two parts are designed in a stepped manner, so that the assembly of the second part is prepared beforehand and as successful as possible, and that the second part can be mounted in the first part with the least difficulty. possible, by limiting the number of assembly operations.
  • the robotic arm joint is designed so that the electronic board of the joint is placed inside the joint itself.
  • the first and second parts of the joint are closed by covers, and the electronic card is directly accessible when an operator opens the cover. Thus, maintenance operations are facilitated.
  • the articulation further comprises a seal mounted between the first and second parts to provide sealing.
  • a seal mounted between the first and second parts to provide sealing.
  • the power, signal and control cables of the joint run entirely inside it, and through the hollow cylindrical shape. They are in contact only with static parts of the joint. This avoids any premature wear of the cables, which would be detrimental to the proper functioning of the joint.
  • Figure 1 shows a section of an instrumented joint for a motorized arm according to the invention.
  • Figure 2 illustrates the stepped design of the joint.
  • the instrumented robotic arm joint of the invention comprises a first part (1) and a second part (2).
  • Each of these parts (1, 2) comprises in particular a one-piece hub, respectively (24, 25) capable of receiving other parts of the joint.
  • the hub of the first part (1) is extended in one piece, in its center, by a hollow cylindrical shape (5a) crossing, in its center, the hub of the second part (2), in order to allow the passage of the cables (27) transmission of power, signal, and control, that is to say also the sensor signal, and allows the chaining of different joints, for example 6 in number for a 6-axis polar robot.
  • the parts (1, 2) are guided in rotation about an axis (5), which is in particular the axis of revolution of the hollow cylindrical shape (5a), via a first guiding system (6 ).
  • This guidance system (6) comprises a set of guidance devices, such as ball or roller bearings. In a preferred embodiment, it is a double row angular contact ball bearing. In fact, a bearing with two rows of angular contact ball bearings makes it possible to have radial guidance in rotation and axial guidance, and therefore a combined bearing, efficient with a reduced size.
  • the articulation also comprises a motor (4) and a reducer (3), intended to drive the second part (2) in relative rotation with respect to the first part (1).
  • the motor (4) comprises a stator (8) mounted on the first part (1), and a rotor (7) mounted on the second part (2).
  • the motor (4) is for example a synchronous motor intended to be driven in torque or in position.
  • the reducer (3) is an elliptical reducer, but it is entirely possible to replace it with an epicyclic reducer or with another type of suitable reducer.
  • the kinematic chain between the first part (1) and the second part (2) further comprises other hubs and guide devices intended to connect these said parts (1, 2), the stator (8) and the rotor (7) of the motor, the inlet and the outlet of the reducer, but these other hubs and guide devices will not be detailed here because they do not directly relate to the technical solution provided by the present invention.
  • a second swivel guide system (9) is mounted between the parts (1) and (2).
  • it is a self-aligning ball or roller bearing.
  • Other technical solutions can of course be considered, such as for example a radial ball joint comprising an inner ring, secured to the second part (2), and an outer ring, secured to the first part (1), each comprising a spherical face so that when the two rings are mounted one in the other, the spherical faces cooperate together.
  • Radial ball joints make it possible to obtain ball-and-socket guidance while having a small radial size. These solutions would make it possible to obtain the same result but they have a larger radial size.
  • This second guidance system (9) is mounted hyperstatically relative to the first system (6). It is said to be hyperstatic insofar as it constrains the assembly between the first part (1) and the second part (2) on degrees of freedom which are already blocked by the first guidance system (6). Indeed, the first guidance system (6) is a pivot, that is to say that it blocks the three possible translations as well as two rotations between the first part (1) and the second part (2).
  • the assembly of this second guide system (9), which also blocks the three possible translations between the two parts (1, 2), is done with more constraints than what is strictly necessary, and consequently induces greater rigidity. of assembly.
  • the second guide system (9) is swiveling, that is to say it allows the swiveling of the first part (1) with respect to the second part (2) along a main axis of rotation, and tilting along the two other axes orthonormal with respect to the main axis.
  • non-rotating rotational guidance i.e. allowing pivoting but not tilting, would have further increased the rigidity of the assembly, but the deformation under load would have occurred at the level of the internal clearances of the systems of guidance in a very limited way, and would have been difficult to measure with a gauge.
  • the second guidance system (9) does not absorb any torque and the forces are therefore transmitted to the second part (2), towards a judiciously chosen place of the assembly which deforms.
  • the deformation can be measured by means of one or more strain gauges (10), which are, in a preferred embodiment, placed on a hub (23) of the part (2) to make them easily accessible.
  • the radial axis of the ball joint sphere of the ball joint guide system (9) is centered on the axis (5) to avoid parasitic deformations. It could be envisaged to remove the second swivel guide (9), but a less rigid joint would be obtained, reducing the precision and repeatability of the deformation measurements.
  • the articulation also comprises optical (12) and magnetic (13) encoders making it possible to know the angular position between the two parts (1, 2).
  • the rigid general design, described above, allows the integration of these redundant encoders, and the presence of the hollow cylindrical shape (5a) makes it possible to chain several joints.
  • a magnetic encoder is generally based on a principle of magnetic field measurement, the latter being obtained by means of a permanent magnet located for example on the stator (8), while the antagonist part, in this example the rotor (7 ), is provided with a magnetic field sensor which is capable of measuring the field and then determining an absolute and unique position of the rotor (7) with respect to the stator (8).
  • An optical encoder generally comprises an encoder wheel mounted on the rotor (7). This wheel has patterns, which are detected by optical sensors located on the stator (8). Thus, the optical encoder is able to determine an absolute and unique position of the rotor (7) with respect to the stator (8).
  • the joint comprises two deflectors (1 ia, 11b) to encapsulate the power, signal and control supply cables so that they are not in contact with dynamic parts and eliminate wear.
  • the joint also includes braking means (14), which in a preferred embodiment is in the form of a disc brake, although other types of brakes may be used.
  • braking means (14) block the rotation between the stator (8) and the rotor (7) of the motor, and are intended to form a holding brake in position.
  • These braking means are used for example during emergency stops of the robotic arm, situations in which the safety rules may require that the robotic arm immediately stop all movement and remain in its position without using the motor of the articulation, the emergency stop possibly resulting for example from a failure of the engine control means or from a power supply failure.
  • This device can also be used during maintenance operations in which it is necessary to access the internal parts of the joint, which means that the normal operation of the components, whether motor, reducer or other elements, cannot of course be considered.
  • An electronic card (15) is intended to collect and process information necessary for controlling and controlling the joint. This information can come from strain gauges (10), optical and magnetic encoders (12, 13) or braking means (14) for example. All these elements are therefore connected to the electronic card (15), via openings made in the hub (25) of the part (2) and which allow the passage of the necessary cables.
  • Ua electronic card also performs the motor controller function, while the solutions of the prior art tend to separate these two functions into two separate cards, and the controller is generally remote in an external electrical cabinet.
  • the electronic card of the invention acting as a controller, is therefore inside the joint itself.
  • the second part (2) is closed by a cover (18), and that the electronic card (15) is directly accessible when an operator opens this cover (18). This makes it easy to carry out maintenance operations on the electronics of the joint, without having to waste too much time dismantling.
  • a similar cover (17) is present on the part (1), this one finds its utility during the assembly of the robotic arm when it is necessary to pass the power and control cables of the joints of the arm through them.
  • the articulation also includes a seal (16) which seals the articulation, and its proximity to the guidance system (9) ensures its correct operation.
  • the covers (17, 18) are mounted without screws or other visible fasteners. The joint thus obtained is sealed, and devoid of bacterial retention zones.
  • the robotic arm equipped with such joints will therefore be very easy to clean and its use adapted to areas where hygiene is essential, such as the food industry or the medical sector, and can also be compatible with bacteriological and nuclear decontamination processes.
  • the bearing surfaces and bores (21, 22) of the parts (1, 2) are arranged in a stepped fashion so that the assembly or disassembly of the part (2) in the part (1) is find it easy.
  • many solutions of the prior art disclose parts of robotic arms which have many subsets.
  • the mounting of the second part in the first then needs to be done in several steps, the subassemblies of one part and the other then being mounted successively. This is problematic not only during the initial assembly of the joint, because the assembly time is thereby lengthened, but also during maintenance operations when it is necessary to intervene on a part located at the heart of the assembly.
  • the design of the present invention it is easy to mount modules of the first part (1) or of the second part (2) in advance, and to have short assembly times during the initial assembly of the joint. It is also easy to have low downtimes of the articulated robotic arm in the event of breakdown or maintenance, since it is possible to replace a defective part with a replacement module and to quickly restart the system including the robotic arm. Speak clearly.
  • the defective part can then be dismantled off-site to reach the parts to be maintained, without the system using the articulated robotic arm being stopped.
  • the joint assembly can also be tested before being integrated into the robot.

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  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Robotics (AREA)
  • Microelectronics & Electronic Packaging (AREA)
  • Manipulator (AREA)

Abstract

The invention relates to a joint for a robotic arm comprising: a first part (1) of the robotic arm and a second part (2) of the robotic arm, the first part (1) of the joint being extended in an integral manner, at the centre thereof, by a hollow cylindrical shape (5a) passing through, at its centre, the second part (2), the first part (1) is rotationally guided about a general axis (5) of revolution of the joint with respect to the second part (2) by virtue of a first guiding system (6); a motor (4) and a reducing gear (3) for rotating the second part (2) with respect to the first part (1); the motor (4) comprising a stator (8) coupled to the first part (1), and a rotor (7) coupled to a hollow central shaft of the reducing gear (26). According to the invention, the joint comprises: a second guide system (9), which is hyperstatic, capable of swivelling with respect to the first guide system (6) and guides at least the rotation of the first and second parts (1, 2) about the axis (5); at least one strain gauge (10) mounted on a deformation zone of the first part (1) or of the second part (2), and connected to an electronic board (15).

Description

Articulation instrumentée pour bras robotisé Domaine technique Instrumented joint for robotic arm Technical field
La présente invention concerne le domaine des bras robotisés articulés, et plus particulièrement le domaine des articulations instrumentées et motorisées de ces bras. The present invention relates to the field of articulated robotic arms, and more particularly to the field of instrumented and motorized joints of these arms.
Art antérieur Prior art
Il est connu des documents FR3065898 et W02015131904 de réaliser un bras robotisé articulé comprenant une première partie solidaire d’une première portion du bras robotisé, une seconde partie solidaire d’une seconde portion du bras robotisé, la première partie de l’articulation étant mobile en rotation par rapport à la deuxième partie au moyen d’un système de guidage, l’articulation comprenant en outre un moteur muni d’un rotor et d’un stator, et un réducteur, destinés à entraîner en rotation relative la deuxième partie par rapport à la première partie. It is known from documents FR3065898 and W02015131904 to produce an articulated robotic arm comprising a first part fixed to a first portion of the robotic arm, a second part fixed to a second portion of the robotic arm, the first part of the joint being mobile in rotation relative to the second part by means of a guide system, the articulation further comprising a motor provided with a rotor and a stator, and a reduction gear, intended to drive the second part in relative rotation by compared to the first part.
Dans le domaine de la robotique et en particulier des bras robotisés articulés, certaines autorités imposent que les mesures d’information nécessaires au pilotage et au contrôle du système robotisé soient faites de manière redondante, c’est-à-dire que la même grandeur est mesurée deux fois et idéalement par des moyens technologiques différents. Ce principe de sécurité bien connu permet de pallier la défaillance de l’un des systèmes de mesure, et d’éviter ainsi des accidents dont les conséquences pourraient être graves en termes humain ou matériel. In the field of robotics and in particular articulated robotic arms, some authorities require that the information measurements necessary for piloting and controlling the robotic system be made redundantly, that is to say that the same quantity is measured twice and ideally by different technological means. This well-known safety principle makes it possible to compensate for the failure of one of the measurement systems, and thus to avoid accidents whose consequences could be serious in human or material terms.
Une des grandeurs à mesurer dans le domaine des bras robotisés articulés est notamment l’effort auquel est soumis le bras. Cet effort peut être par exemple le poids d’une charge que le bras aurait saisie au moyen d’un préhenseur disposé à son extrémité. Mais cet effort peut également provenir de la collision d’une partie du bras robotisé articulé avec un élément de son environnement. Cet élément peut être un élément mécanique, fixe ou mobile, présent à proximité de l’installation du bras robotisé articulé, par exemple un deuxième bras articulé qui accomplirait d’autres tâches. Cet élément en collision peut également être une personne, notamment dans le cas particulier des « cobots », qui sont des robots destinés à travailler en collaboration avec une personne, donc à proximité immédiate avec celle-ci. On comprend bien dans ce contexte l’importance de la fiabilité des systèmes de mesure nécessaires au pilotage et au contrôle du système robotisé. Il est connu des réalisations précédentes de mesurer les appels de courant du moteur pour avoir une information sur les efforts auxquels celui-ci est soumis, et par déduction de trouver les efforts auxquels sont soumises les différentes parties du bras robotisé. En revanche, le moteur relie les deux parties du bras à travers une chaîne cinématique complexe, comprenant notamment le réducteur, et on ne sait donc pas si rinformation de l’effort reconstituée à partir de la mesure du courant est réellement l’effort auquel est soumis le bras ou si des efforts autres, dus par exemple à une mauvaise performance du réducteur, viennent polluer la mesure réalisée. One of the quantities to be measured in the field of articulated robotic arms is in particular the force to which the arm is subjected. This effort can be for example the weight of a load that the arm would have grasped by means of a gripper arranged at its end. But this force can also come from the collision of a part of the articulated robotic arm with an element of its environment. This element can be a mechanical element, fixed or mobile, present close to the installation of the articulated robotic arm, for example a second articulated arm which would perform other tasks. This colliding element can also be a person, in particular in the specific case of “cobots”, which are robots intended to work in collaboration with a person, therefore in close proximity with the latter. In this context, it is easy to understand the importance of the reliability of the measurement systems necessary for piloting and controlling the robotized system. It is known from previous embodiments to measure the current inrush of the motor to obtain information on the forces to which it is subjected, and by deduction to find the forces to which the different parts of the robotic arm are subjected. On the other hand, the motor connects the two parts of the arm through a complex kinematic chain, including in particular the reducer, and it is therefore not known whether the force information reconstituted from the current measurement is really the force at which it is subjected to the arm or if other forces, due for example to poor performance of the reducer, come to pollute the measurement carried out.
Il est également connu d’utiliser des jauges de déformation connues sous d’autres noms tels que « jauges de contraintes » ou « capteur d’effort ». En effet ces jauges de déformation, placées à la surface d’une pièce soumise à un effort, sont capables de mesurer les déformations que subit ladite pièce mise sous charge. Par calcul, on est capable de savoir quel est l’effort que subit ladite pièce. Néanmoins, il faut que ces jauges soient placées judicieusement sur la pièce pour donner une mesure qui soit exploitable. En effet, ces jauges mesurent une déformation et celle-ci n’est pas identique partout sur la pièce, notamment en fonction de son montage, par exemple dans un assemblage : la déformation sera nulle dans la ou les directions bloquées par ce montage. De façon évidente, au niveau d’une liaison encastrement bloquant les six degrés de liberté, aucune déformation de la pièce n’est possible. Au niveau d’une liaison pivot autorisant une rotation, la déformation ne sera possible que dans la direction de la rotation autorisée par le pivot, mais sera nulle dans les directions des trois translations et des deux rotations bloquées par cette liaison pivot. Les jauges de déformation ne sont donc pas toujours exploitables dans un assemblage, s’il n’est pas possible de placer ces jauges à un endroit pertinent au vu des efforts à mesurer. It is also known to use strain gauges known by other names such as "strain gauges" or "force sensor". Indeed these deformation gauges, placed on the surface of a part subjected to a force, are able to measure the deformations that said part undergoes under load. By calculation, we are able to know what is the effort that said part undergoes. Nevertheless, these gauges must be placed judiciously on the part to give a measurement that is usable. Indeed, these gauges measure a deformation and this is not identical everywhere on the part, in particular according to its assembly, for example in an assembly: the deformation will be zero in the direction or directions blocked by this assembly. Obviously, at the level of an embedding connection blocking the six degrees of freedom, no deformation of the part is possible. At the level of a pivot connection authorizing a rotation, the deformation will only be possible in the direction of the rotation authorized by the pivot, but will be zero in the directions of the three translations and the two rotations blocked by this pivot connection. Strain gauges are therefore not always usable in an assembly, if it is not possible to place these gauges in a relevant place in view of the forces to be measured.
Il est également connu les documents KR101194313, US5327790 et US2020/108514 qui divulguent un deuxième système de guidage pour éviter les forces sur le capteur dans les autres directions non rotatives autour d’axe central, et le document US2011/239788 qui évoque le problème de centrage entre deux systèmes de guidage dans une articulation d’un robot, mais qui propose un découplage flexible comme solution. It is also known the documents KR101194313, US5327790 and US2020/108514 which disclose a second guidance system to avoid the forces on the sensor in the other non-rotating directions around the central axis, and the document US2011/239788 which evokes the problem of centering between two guidance systems in a joint of a robot, but which offers flexible decoupling as a solution.
Exposé de l’invention Disclosure of Invention
L’invention a donc pour but de fournir une articulation instrumentée pour bras robotisé pour mesurer efficacement les efforts auxquels sont soumis ce bras, en complément d’une mesure redondante d’appel de courant. Un autre but de l’invention est de fournir une telle articulation dont la conception, le montage et la maintenance sont facilités. The object of the invention is therefore to provide an instrumented joint for a robotic arm to effectively measure the forces to which this arm is subjected, in addition to a redundant current inrush measurement. Another object of the invention is to provide such a joint whose design, assembly and maintenance are facilitated.
A cet effet, il a été mis au point une articulation instrumentée pour bras robotisé conforme à celle de l’état de la technique en ce qu’elle comprend : For this purpose, an instrumented joint for a robotic arm has been developed in accordance with that of the state of the art in that it includes:
- une première partie du bras robotisé et une seconde partie du bras robotisé, la première partie de l’articulation étant prolongée de manière monobloc, en son centre, par une forme cylindrique creuse traversant, en son centre, la deuxième partie, la première partie est guidée en rotation autour d’un axe général de révolution de l’articulation par rapport à la deuxième partie grâce à un premier système de guidage, - a first part of the robotic arm and a second part of the robotic arm, the first part of the joint being extended in one piece, at its center, by a hollow cylindrical shape passing through, at its center, the second part, the first part is guided in rotation around a general axis of revolution of the articulation with respect to the second part thanks to a first guiding system,
- un moteur et un réducteur, destinés à entraîner en rotation relative la deuxième partie par rapport à la première partie, - a motor and a reducer, intended to drive the second part in relative rotation with respect to the first part,
- le moteur comprenant un stator accouplé à la première partie, et un rotor accouplé à un arbre central creux du réducteur. - the motor comprising a stator coupled to the first part, and a rotor coupled to a hollow central shaft of the reducer.
Selon l’invention, l’articulation comprend : According to the invention, the joint comprises:
- un deuxième système de guidage hyperstatique et rotulant par rapport au premier système de guidage, et guidant au moins la rotation des première et deuxième parties autour de l’axe, - a second hyperstatic and rotulant guidance system with respect to the first guidance system, and guiding at least the rotation of the first and second parts around the axis,
- au moins une jauge de déformation montée sur la première ou la deuxième partie, et reliée à une carte électronique. - At least one strain gauge mounted on the first or the second part, and connected to an electronic card.
Le premier système de guidage en rotation entre la première partie et la deuxième partie, est de tout type approprié, tel qu’un roulement, à billes ou à rouleaux, ou un roulement à contact oblique dont l’assemblage permet d’obtenir une rigidité plus importante qu’avec des roulements à contact radial. Comme tout système de guidage, il peut comporter un jeu interne (axial ou angulaire). Ce jeu peut être limité en soumettant le premier système de guidage à une pré-charge, mais celle-ci ne doit pas être excessive car elle pourrait réduire la durée de vie du premier système de guidage. The first system for guiding in rotation between the first part and the second part is of any suitable type, such as a ball or roller bearing, or an angular contact bearing, the assembly of which makes it possible to obtain a rigidity greater than with radial contact bearings. Like any guidance system, it may have internal clearance (axial or angular). This clearance can be limited by subjecting the first guidance system to a pre-load, but this should not be excessive since it could reduce the life of the first guidance system.
Par ailleurs, ce premier système de guidage a sa rigidité qui lui est propre et qui n’est pas infinie, aussi le système se déforme lorsque le bras robotisé est soumis à une charge. Cette charge peut être par exemple le poids d’un objet que manipule le bras, ou un effort dynamique lorsque le bras fait des accélérations ou des décélérations dans ses mouvements. Moreover, this first guidance system has its own rigidity which is not infinite, so the system deforms when the robotic arm is subjected to a load. This load can be, for example, the weight of an object manipulated by the arm, or a dynamic force when the arm makes accelerations or decelerations in its movements.
Cette déformation est néanmoins située au niveau de l’assemblage du premier système de guidage, et n’est pas mesurable à son niveau car l’encombrement de l’assemblage est trop important. De plus, le bon fonctionnement du premier système de guidage nécessite généralement la présence de lubrifiant qui empêche de placer facilement des jauges de déformation qui sont typiquement des capteurs filaires, le câblage de ces capteurs empêchant la bonne étanchéité nécessaire pour éviter la fuite dudit lubrifiant. Enfin, le premier système de guidage entre la première et la deuxième partie est généralement située à proximité de la première partie, et n’est donc pas un endroit judicieux pour mesurer les efforts auxquels est soumise la deuxième partie du bras, car cet endroit en est trop éloigné. This deformation is nevertheless located at the level of the assembly of the first guidance system, and is not measurable at its level because the size of the assembly is too great. What's more, the proper functioning of the first guidance system generally requires the presence of lubricant which prevents the easy placement of strain gauges which are typically wired sensors, the wiring of these sensors preventing the proper sealing necessary to prevent the leakage of said lubricant. Finally, the first guidance system between the first and the second part is generally located close to the first part, and is therefore not a judicious place to measure the forces to which the second part of the arm is subjected, because this place in is too far away.
Rajouter un deuxième de système de guidage, qui est hyperstatique par rapport au premier système de guidage, permet d’augmenter significativement la rigidité du guidage en rotation de la première partie par rapport à la deuxième partie. Adding a second guidance system, which is hyperstatic relative to the first guidance system, makes it possible to significantly increase the rigidity of the rotational guidance of the first part relative to the second part.
Par ailleurs, étant donné que ce deuxième système de guidage est rotulant, et est monté entre les deux moyeux principaux, respectivement de la première partie et de la deuxième partie, l’assemblage ainsi obtenu permet donc d’orienter la déformation due aux charges au niveau de la deuxième partie, plutôt que de la laisser survenir au niveau du premier système de guidage. Le lieu de la déformation étant ainsi maîtrisé, il devient possible de placer les jauges de déformation sur une zone de déformation de la première partie ou de la deuxième partie, de façon à ce qu’elles soient efficaces en ce que leur mesure permet d’avoir une information, notamment redondante, précise et non perturbée des efforts auxquels est soumise la deuxième partie. Furthermore, given that this second guide system is swiveling, and is mounted between the two main hubs, respectively of the first part and of the second part, the assembly thus obtained therefore makes it possible to orient the deformation due to the loads at the level of the second part, rather than letting it occur at the level of the first guidance system. The location of the deformation being thus controlled, it becomes possible to place the deformation gauges on a deformation zone of the first part or of the second part, so that they are effective in that their measurement makes it possible to to have information, in particular redundant, precise and undisturbed of the efforts to which the second part is subjected.
La deuxième partie étant directement solidaire avec le moteur, il est tout à fait pertinent de placer la ou les jauges de déformation dessus afin qu’elles donnent une information pertinente des efforts auxquels est soumis le bras. As the second part is directly attached to the engine, it is very relevant to place the strain gauge(s) on it so that they give relevant information on the forces to which the arm is subjected.
Le deuxième système de guidage est de préférence déporté par rapport au premier système de guidage le long de l’axe par rapport au premier système de guidage. Ainsi, la rigidité gagnée par l’assemblage hyperstatique s’en trouve améliorée. Il ressort également que l’articulation est plus équilibrée, le premier système de guidage étant lui placé, par exemple, à l’aplomb ou à proximité de la première partie de l’articulation. Décaler le deuxième système de guidage permet donc d’obtenir une articulation plus à même d’encaisser les efforts inhérents à Lutilisation du bras robotisé articulé. The second guidance system is preferably offset relative to the first guidance system along the axis relative to the first guidance system. Thus, the rigidity gained by the hyperstatic assembly is improved. It also emerges that the joint is more balanced, the first guidance system being placed, for example, plumb or close to the first part of the joint. Shifting the second guidance system therefore makes it possible to obtain an articulation that is better able to absorb the forces inherent in the use of the articulated robotic arm.
Le premier système de guidage est de préférence un roulement à billes. Cette solution présente l’avantage d’être compacte, en particulier s’il s’agit d’un roulement à deux rangées de billes à contact oblique. Le premier système de guidage peut également être un assemblage de plusieurs roulements, qu’ils soient à billes ou à rouleaux croisés, avec des contacts obliques et radiaux. The first guide system is preferably a ball bearing. This solution has the advantage of being compact, in particular if it is a bearing with two rows of contact balls oblique. The first guidance system can also be an assembly of several bearings, whether ball bearings or crossed rollers, with oblique and radial contacts.
Le deuxième système de guidage est de préférence un roulement à billes. D’autres solutions techniques peuvent bien sûr être envisagées, comme par exemple des à rotules radiales ou des roulements à rouleaux sphériques. Une rotule radiale est un assemblage de deux bagues dont une bague extérieure avec une face interne de forme concave et sphérique, et une bague intérieure avec une face externe de forme convexe et sphérique complémentaire. Les deux bagues sont montées l’une dans l’autre de sorte que les faces sphériques coopèrent ensemble. Pour faciliter le montage d’une bague dans l’autre, l’une des bagues peut être en deux parties, de préférence la bague externe. Les rotules radiales permettent d’obtenir un guidage rotulant tout en ayant un encombrement radial faible. The second guide system is preferably a ball bearing. Other technical solutions can of course be considered, such as radial spherical bearings or spherical roller bearings. A radial ball joint is an assembly of two rings including an outer ring with a concave and spherical inner face, and an inner ring with a complementary convex and spherical outer face. The two rings are mounted one inside the other so that the spherical faces cooperate together. To facilitate the assembly of one ring in the other, one of the rings can be in two parts, preferably the outer ring. Radial ball joints make it possible to obtain ball-and-socket guidance while having a small radial size.
De préférence, l’articulation de bras robotisé comprend également des moyens de mesure de l’angle entre les première et deuxième parties. Ces moyens de mesure sont par exemple des codeurs, idéalement un codeur optique et un codeur magnétique, mesurant chacun le déplacement angulaire du rotor par rapport au stator. Utiliser ces deux types de codeurs, qui mesurent de manière redondante la position angulaire du rotor par rapport au stator, mais en étant basés sur des technologies différentes, permet de garantir la fiabilité nécessaire au pilotage et au contrôle du système robotisé. Ces codeurs sont reliés à la carte électronique afin que celle-ci puisse traiter leurs signaux. Preferably, the robotic arm joint also comprises means for measuring the angle between the first and second parts. These measuring means are for example encoders, ideally an optical encoder and a magnetic encoder, each measuring the angular displacement of the rotor relative to the stator. Using these two types of encoders, which measure the angular position of the rotor relative to the stator in a redundant manner, but being based on different technologies, makes it possible to guarantee the reliability necessary for piloting and controlling the robotized system. These encoders are connected to the electronic board so that the latter can process their signals.
De préférence, l’articulation de bras robotisé comprend également des moyens de freinage du pivotement de la première partie par rapport à la deuxième partie, tel qu’un frein à disque. L’avantage d’utiliser un frein par rapport à d’autres systèmes de maintien en position, par exemple basés sur des dispositifs d’indexage coopérant avec une étoile, est que le frein n’a pas de position angulaire indexée, c’est-à-dire qu’il peut se bloquer à n’importe quelle position angulaire entre les deux parties du bras robotisé articulé. Les dispositifs à index sont eux, par définition, soumis à des positions angulaires qui sont celles des bras de l’étoile utilisée. En fonction de l’étoile utilisée, il peut donc y avoir un nombre limité de positions disponibles. De plus, en fonction de l’assemblage entre l’étoile et l’index, cette solution peut autoriser le mouvement relatif des deux parties sur une plage angulaire résiduelle correspondant à l’écartement entre deux bras successifs de l’étoile. Enfin, les bras de l’étoile et l’index étant soumis à des chocs lors d’arrêts d’urgence, la durée de vie de ces systèmes est généralement faible car les pièces se détériorent. Avec Eutilisation d’un frein, l’énergie cinétique à dissiper lors d’arrêts d’urgence se fait de façon thermique, résultant des frottements entre les garnitures du frein et le disque, ce qui est moins pénalisant pour la mécanique. L’utilisation d’un frein dans le domaine technique des bras robotisés articulés est donc particulièrement judicieux. Preferably, the robotic arm joint also comprises means for braking the pivoting of the first part relative to the second part, such as a disc brake. The advantage of using a brake compared to other position holding systems, for example based on indexing devices cooperating with a star, is that the brake does not have an indexed angular position, it is that is, it can lock at any angular position between the two parts of the articulated robotic arm. The index devices are them, by definition, subject to angular positions which are those of the arms of the star used. Depending on the star used, there may therefore be a limited number of positions available. Moreover, depending on the assembly between the star and the index, this solution can allow the relative movement of the two parts over a residual angular range corresponding to the spacing between two successive arms of the star. Finally, the arms of the spider and the index being subjected to shocks during emergency stops, the life of these systems is generally short because the parts deteriorate. With the use of a brake, the kinetic energy to be dissipated during emergency stops occurs thermally, resulting from friction between the brake linings and the disc, which is less penalizing for the mechanics. The use of a brake in the technical field of articulated robotic arms is therefore particularly sensible.
L’articulation est composée de deux parties montées en articulation pivot l’une par rapport à l’autre. Selon une forme de réalisation particulière, la deuxième partie comporte au moins une portée cylindrique (ou respectivement un alésage) venant s’emboîter lors du montage de l’articulation dans au moins un alésage cylindrique (ou respectivement une portée) complémentaire de la première partie, éventuellement via les premier et deuxième systèmes de guidage, de façon à ce que la première partie puisse accueillir la deuxième partie. De manière avantageuse, les deux parties sont conçues de façon étagée, de telle sorte que l’assemblage de la deuxième partie soit préparé préalablement et le plus aboutit possible, et que la deuxième partie puisse être montée dans la première partie avec le moins de difficultés possibles, en limitant le nombre d’opérations de montage. The joint is made up of two parts mounted as a pivot joint with respect to each other. According to a particular embodiment, the second part comprises at least one cylindrical bearing surface (or respectively a bore) which fits during assembly of the joint in at least one cylindrical bore (or respectively a bearing surface) complementary to the first part , optionally via the first and second guidance systems, so that the first part can accommodate the second part. Advantageously, the two parts are designed in a stepped manner, so that the assembly of the second part is prepared beforehand and as successful as possible, and that the second part can be mounted in the first part with the least difficulty. possible, by limiting the number of assembly operations.
L’articulation de bras robotisé est conçue de façon à ce que la carte électronique de l’articulation soit placée à l’intérieur même de l’articulation. The robotic arm joint is designed so that the electronic board of the joint is placed inside the joint itself.
Les première et deuxième parties de l’articulation sont fermées par des capots, et la carte électronique est directement accessible lorsqu’un opérateur ouvre le capot. Ainsi, les opérations de maintenance sont facilitées. The first and second parts of the joint are closed by covers, and the electronic card is directly accessible when an operator opens the cover. Thus, maintenance operations are facilitated.
L’articulation comprend par ailleurs un joint monté entre les première et deuxième parties pour assurer l’étanchéité. Ainsi étanche, l’articulation peut être nettoyée efficacement, et être ainsi compatible avec les exigences des applications alimentaires ou nucléaires par exemple. The articulation further comprises a seal mounted between the first and second parts to provide sealing. Thus sealed, the joint can be cleaned effectively, and thus be compatible with the requirements of food or nuclear applications for example.
Les câbles de puissance, signal, et pilotage, de l’articulation cheminent intégralement à l’intérieur de celle-ci, et au travers de la forme cylindrique creuse. Ils sont en contact uniquement avec des pièces statiques de l’articulation. Ceci permet d’éviter tout usure prématurée des câbles, qui serait néfaste pour le bon fonctionnement de l’articulation. The power, signal and control cables of the joint run entirely inside it, and through the hollow cylindrical shape. They are in contact only with static parts of the joint. This avoids any premature wear of the cables, which would be detrimental to the proper functioning of the joint.
L’invention et son fonctionnement seront mieux compris à la lecture de la description détaillée et des figures ci-après. The invention and its operation will be better understood on reading the detailed description and the figures below.
Brève description des dessins [Fig. 1] La figure 1 montre une coupe d’une articulation instrumentée pour bras motorisé selon l’invention. Brief description of the drawings [Fig. 1] Figure 1 shows a section of an instrumented joint for a motorized arm according to the invention.
[Fig. 2] La figure 2 illustre la conception étagée de l’articulation. [Fig. 2] Figure 2 illustrates the stepped design of the joint.
Description détaillée de l’invention Detailed description of the invention
L’articulation instrumentée de bras robotisé de l’invention comprend une première partie (1) et une deuxième partie (2). Chacune de ces parties (1, 2) comprend notamment un moyeu monobloc, respectivement (24, 25) apte à recevoir d’autres pièces de l’articulation. Le moyeu de la première partie (1) est prolongé de manière monobloc, en son centre, par une forme cylindrique creuse (5a) traversant, en son centre, le moyeu de la deuxième partie (2), afin de permettre le passage des câbles (27) de transmission de puissance, signal, et pilotage, c’est-à-dire également le signal de capteurs, et permet le chaînage de différentes articulations, par exemple au nombre de 6 pour un robot polaire 6- axes. Les parties (1, 2) sont guidées en rotation autour d’un axe (5), qui est notamment l’axe de révolution de la forme cylindrique creuse (5a), par l’intermédiaire d’un premier système de guidage (6). Ce système de guidage (6) comprend un ensemble de dispositifs de guidage, tels que des roulements à billes ou à rouleaux. Dans un mode de réalisation préféré, il s’agit d’un roulement à deux rangées de billes à contact oblique. En effet un roulement à deux rangées de billes à contact oblique permet d’avoir un guidage radial en rotation et un guidage axial, et donc un roulement combiné, performant avec un encombrement réduit. The instrumented robotic arm joint of the invention comprises a first part (1) and a second part (2). Each of these parts (1, 2) comprises in particular a one-piece hub, respectively (24, 25) capable of receiving other parts of the joint. The hub of the first part (1) is extended in one piece, in its center, by a hollow cylindrical shape (5a) crossing, in its center, the hub of the second part (2), in order to allow the passage of the cables (27) transmission of power, signal, and control, that is to say also the sensor signal, and allows the chaining of different joints, for example 6 in number for a 6-axis polar robot. The parts (1, 2) are guided in rotation about an axis (5), which is in particular the axis of revolution of the hollow cylindrical shape (5a), via a first guiding system (6 ). This guidance system (6) comprises a set of guidance devices, such as ball or roller bearings. In a preferred embodiment, it is a double row angular contact ball bearing. In fact, a bearing with two rows of angular contact ball bearings makes it possible to have radial guidance in rotation and axial guidance, and therefore a combined bearing, efficient with a reduced size.
L’articulation comprend également un moteur (4) et un réducteur (3), destinés à entraîner en rotation relative la deuxième partie (2) par rapport à la première partie (1). Le moteur (4) comprend un stator (8) monté sur la première partie (1), et un rotor (7) monté sur la deuxième partie (2). Le moteur (4) est par exemple un moteur synchrone destiné à être piloté en couple ou en position. Dans le mode de réalisation présenté, le réducteur (3) est un réducteur elliptique, mais il est tout à fait possible de le remplacer par un réducteur épicycloïdal ou par un autre type de réducteur adapté. The articulation also comprises a motor (4) and a reducer (3), intended to drive the second part (2) in relative rotation with respect to the first part (1). The motor (4) comprises a stator (8) mounted on the first part (1), and a rotor (7) mounted on the second part (2). The motor (4) is for example a synchronous motor intended to be driven in torque or in position. In the embodiment presented, the reducer (3) is an elliptical reducer, but it is entirely possible to replace it with an epicyclic reducer or with another type of suitable reducer.
La chaîne cinématique entre la première partie (1) et la deuxième partie (2) comprend en outre d’autres moyeux et dispositifs de guidage destinés à relier entre eux ces dites parties (1, 2), le stator (8) et le rotor (7) du moteur, l’entrée et la sortie du réducteur, mais ces autres moyeux et dispositifs de guidages ne seront pas plus détaillés ici car ils ne concernent pas directement la solution technique apportée par la présente invention. The kinematic chain between the first part (1) and the second part (2) further comprises other hubs and guide devices intended to connect these said parts (1, 2), the stator (8) and the rotor (7) of the motor, the inlet and the outlet of the reducer, but these other hubs and guide devices will not be detailed here because they do not directly relate to the technical solution provided by the present invention.
Un deuxième système de guidage rotulant (9) est monté entre les parties (1) et (2). Dans un mode de réalisation préféré, il s’agit d’un roulement à rotule sur billes ou à rouleaux. D’autres solutions techniques peuvent bien sûr être envisagées, comme par exemple une rotule radiale comprenant une bague interne, assujettie à la deuxième partie (2), et une bague externe, assujettie à la première partie (1), chacune comprenant une face sphérique de sorte que lorsque les deux bagues sont montées l’une dans l’autre, les faces sphériques coopèrent ensembles. Les rotules radiales permettent d’obtenir un guidage rotulant tout en ayant un encombrement radial faible. Ces solutions permettraient d’obtenir le même résultat mais elles présentent un encombrement radial plus important. A second swivel guide system (9) is mounted between the parts (1) and (2). In a preferred embodiment, it is a self-aligning ball or roller bearing. Other technical solutions can of course be considered, such as for example a radial ball joint comprising an inner ring, secured to the second part (2), and an outer ring, secured to the first part (1), each comprising a spherical face so that when the two rings are mounted one in the other, the spherical faces cooperate together. Radial ball joints make it possible to obtain ball-and-socket guidance while having a small radial size. These solutions would make it possible to obtain the same result but they have a larger radial size.
Ce deuxième système de guidage (9) est monté de façon hyperstatique par rapport au premier système (6). Il est dit hyperstatique dans la mesure où il vient contraindre l’assemblage entre la première partie (1) et la deuxième partie (2) sur des degrés de liberté qui sont déjà bloqués par le premier système de guidage (6). En effet, le premier système de guidage (6) est un pivot, c’est-à-dire qu’il bloque les trois translations possibles ainsi que deux rotations entre la première partie (1) et la deuxième partie (2). Le montage de ce deuxième système de guidage (9), qui vient également bloquer les trois translations possibles entre les deux parties (1, 2), se fait avec plus de contraintes que ce qui est strictement nécessaire, et induit par conséquent une rigidité supérieure de l’assemblage. This second guidance system (9) is mounted hyperstatically relative to the first system (6). It is said to be hyperstatic insofar as it constrains the assembly between the first part (1) and the second part (2) on degrees of freedom which are already blocked by the first guidance system (6). Indeed, the first guidance system (6) is a pivot, that is to say that it blocks the three possible translations as well as two rotations between the first part (1) and the second part (2). The assembly of this second guide system (9), which also blocks the three possible translations between the two parts (1, 2), is done with more constraints than what is strictly necessary, and consequently induces greater rigidity. of assembly.
En particulier, le deuxième système de guidage (9) est rotulant, c’est-à-dire qu’il autorise le rotulement de la première partie (1) par rapport à la deuxième partie (2) selon un axe de rotation principal, et le basculement selon les deux autres axes orthonormés par rapport à l’axe principal. Utiliser un guidage en rotation non-rotulant, c’est-à-dire autorisant le pivotement mais pas de basculement, aurait encore augmenté la rigidité de l’assemblage, mais la déformation sous charge se serait produite au niveau des jeux internes des systèmes de guidage de façon très limitée, et aurait été difficilement mesurable par une jauge. En autorisant le basculement de la première partie (1) par rapport à la deuxième partie (2), le deuxième système de guidage (9) n’encaisse pas de couple et les efforts sont donc transmis à la deuxième partie (2), vers un endroit judicieusement choisi de l’assemblage qui se déforme. La déformation peut être mesurée par l’intermédiaire d’une ou plusieurs jauges de déformation (10), qui sont, dans un mode de réalisation préféré, placées sur un moyeu (23) de la partie (2) pour les rendre facilement accessibles. En l’occurrence, l’axe radial de la sphère de rotule du système de guidage rotulant (9) est centré sur l’axe (5) pour éviter les déformations parasites. Il pourrait être envisagé de supprimer le deuxième de guidage (9) rotulant, mais l’on obtiendrait une articulation moins rigide, diminuant la précision et la répétabilité des mesures de déformation. In particular, the second guide system (9) is swiveling, that is to say it allows the swiveling of the first part (1) with respect to the second part (2) along a main axis of rotation, and tilting along the two other axes orthonormal with respect to the main axis. Using non-rotating rotational guidance, i.e. allowing pivoting but not tilting, would have further increased the rigidity of the assembly, but the deformation under load would have occurred at the level of the internal clearances of the systems of guidance in a very limited way, and would have been difficult to measure with a gauge. By authorizing the tilting of the first part (1) with respect to the second part (2), the second guidance system (9) does not absorb any torque and the forces are therefore transmitted to the second part (2), towards a judiciously chosen place of the assembly which deforms. The deformation can be measured by means of one or more strain gauges (10), which are, in a preferred embodiment, placed on a hub (23) of the part (2) to make them easily accessible. In this case, the radial axis of the ball joint sphere of the ball joint guide system (9) is centered on the axis (5) to avoid parasitic deformations. It could be envisaged to remove the second swivel guide (9), but a less rigid joint would be obtained, reducing the precision and repeatability of the deformation measurements.
L’articulation comprend par ailleurs des codeurs optique (12) et magnétique (13) permettant de connaître la position angulaire entre les deux parties (1, 2). La conception générale rigide, décrite ci- avant, permet l’intégration de ces codeurs redondants, et la présence de la forme cylindrique creuse (5a) permet de chaîner plusieurs articulations. Un codeur magnétique est généralement basé sur un principe de mesure de champ magnétique, celui- ci étant obtenu au moyen d’un aimant permanent situé par exemple sur le stator (8), tandis que la partie antagoniste, dans cet exemple le rotor (7), est munie d’un capteur de champ magnétique qui est capable de mesurer le champ et de déterminer ensuite une position absolue et unique du rotor (7) par rapport au stator (8). Un codeur optique comprend généralement une roue codeuse montée sur le rotor (7). Cette roue comporte des motifs, qui sont détectés par des capteurs optiques situés sur le stator (8). Ainsi, le codeur optique est capable de déterminer une position absolue et unique du rotor (7) par rapport au stator (8). The articulation also comprises optical (12) and magnetic (13) encoders making it possible to know the angular position between the two parts (1, 2). The rigid general design, described above, allows the integration of these redundant encoders, and the presence of the hollow cylindrical shape (5a) makes it possible to chain several joints. A magnetic encoder is generally based on a principle of magnetic field measurement, the latter being obtained by means of a permanent magnet located for example on the stator (8), while the antagonist part, in this example the rotor (7 ), is provided with a magnetic field sensor which is capable of measuring the field and then determining an absolute and unique position of the rotor (7) with respect to the stator (8). An optical encoder generally comprises an encoder wheel mounted on the rotor (7). This wheel has patterns, which are detected by optical sensors located on the stator (8). Thus, the optical encoder is able to determine an absolute and unique position of the rotor (7) with respect to the stator (8).
De préférence, l’articulation comprend deux déflecteurs (l ia, 11b) pour encapsuler les câbles d’alimentation en puissance, signal et pilotage pour que ceux-ci ne soient pas en contact avec des parties dynamiques et supprimer l’usure. Preferably, the joint comprises two deflectors (1 ia, 11b) to encapsulate the power, signal and control supply cables so that they are not in contact with dynamic parts and eliminate wear.
U’ articulation comprend également des moyens de freinage (14), qui est dans un mode de réalisation préféré se présentent sous la forme d’un frein à disque, bien que d’autres types de freins puissent être utilisés. Ces moyens de freinage (14) viennent bloquer la rotation entre le stator (8) et le rotor (7) du moteur, et sont destinés à former un frein de maintien en position. Ces moyens de freinage sont amenés à être utilisés par exemple lors d’arrêts d’urgence du bras robotisé, situations dans lesquelles les règles de sécurité peuvent exiger que le bras robotisé arrête immédiatement tout mouvement et reste dans sa position sans utiliser le moteur de l’articulation, l’arrêt d’urgence pouvant être par exemple consécutif à une défaillance des moyens de pilotage du moteur ou à une défaillance d’alimentation en énergie. Ce dispositif peut également être utilisé lors d’opérations de maintenance au cours desquelles il est nécessaire d’accéder aux parties intérieures de l’articulation ce qui signifie que le fonctionnement normal des composants, qu’il s’agisse du moteur, du réducteur ou d’autres éléments, ne peut bien entendu pas être envisagé. U’utilisation d’un frein, en particulier s’il s’agit d’un frein à manque de courant permet donc de bloquer le mouvement du bras pendant l’intervention. The joint also includes braking means (14), which in a preferred embodiment is in the form of a disc brake, although other types of brakes may be used. These braking means (14) block the rotation between the stator (8) and the rotor (7) of the motor, and are intended to form a holding brake in position. These braking means are used for example during emergency stops of the robotic arm, situations in which the safety rules may require that the robotic arm immediately stop all movement and remain in its position without using the motor of the articulation, the emergency stop possibly resulting for example from a failure of the engine control means or from a power supply failure. This device can also be used during maintenance operations in which it is necessary to access the internal parts of the joint, which means that the normal operation of the components, whether motor, reducer or other elements, cannot of course be considered. The use of a brake, in particular if it is a power failure brake, therefore makes it possible to block the movement of the arm during the intervention.
Une carte électronique (15) est destinée à collecter et traiter des informations nécessaires au contrôle et au pilotage de l’articulation. Ces informations peuvent provenir des jauges de déformation (10), des codeurs optique et magnétique (12, 13) ou des moyens de freinage (14) par exemple. Tous ces éléments sont donc reliés à la carte électronique (15), via des ouvertures pratiquées dans le moyeu (25) de la partie (2) et qui permettent le passage des câbles nécessaires. An electronic card (15) is intended to collect and process information necessary for controlling and controlling the joint. This information can come from strain gauges (10), optical and magnetic encoders (12, 13) or braking means (14) for example. All these elements are therefore connected to the electronic card (15), via openings made in the hub (25) of the part (2) and which allow the passage of the necessary cables.
Ua carte électronique (15) assure aussi la fonction de contrôleur du moteur, alors que les solutions de l’art antérieur ont tendance à séparer ces deux fonctions en deux cartes séparées, et le contrôleur est généralement déporté dans une armoire électrique externe. A l’inverse, la carte électronique de l’invention, faisant office de contrôleur, est donc à l’intérieur même de l’articulation. Il découle de cette disposition astucieuse plusieurs avantages : premièrement les temps de communication entre le moteur et la carte électronique sont réduits du fait de leur proximité. Ce gain de temps permet une réactivité améliorée du système. De plus, le câblage du dispositif s’en trouve simplifié puisqu’il n’y a pas à prévoir au sein du bras et de ses différentes articulations le câblage aller et retour de chaque moteur vers une armoire externe. Enfin, le câblage entre les moteurs et cartes électroniques des différentes articulations d’un bras robotisé articulé ne passant pas à travers chaque articulation du bras en direction de l’armoire, ces câbles ne passent pas à proximité d’autres moteurs ou de câbles de puissance et ne sont donc pas exposés à des perturbations électromagnétiques qui pourraient être gênantes pour le bon fonctionnement du bras robotisé articulé. Ua electronic card (15) also performs the motor controller function, while the solutions of the prior art tend to separate these two functions into two separate cards, and the controller is generally remote in an external electrical cabinet. Conversely, the electronic card of the invention, acting as a controller, is therefore inside the joint itself. Several advantages result from this clever arrangement: firstly, the communication times between the motor and the electronic card are reduced due to their proximity. This time saving allows an improved reactivity of the system. In addition, the wiring of the device is thereby simplified since there is no need to provide within the arm and its various joints the outward and return wiring of each motor to an external cabinet. Finally, the wiring between the motors and electronic cards of the different joints of an articulated robotic arm does not pass through each joint of the arm in the direction of the cabinet, these cables do not pass close to other motors or cables of power and are therefore not exposed to electromagnetic disturbances which could interfere with the proper functioning of the articulated robotic arm.
Il faut remarquer que la deuxième partie (2) est fermée par un capot (18), et que la carte électronique (15) est directement accessible lorsqu’un opérateur ouvre ce capot (18). Cela permet de réaliser facilement des opérations de maintenance sur l’électronique de l’articulation, sans avoir à perdre trop de temps en démontage. It should be noted that the second part (2) is closed by a cover (18), and that the electronic card (15) is directly accessible when an operator opens this cover (18). This makes it easy to carry out maintenance operations on the electronics of the joint, without having to waste too much time dismantling.
Un capot similaire (17) est présent sur la partie (1), celui-ci trouve son utilité lors du montage du bras robotisé lorsqu’il faut faire passer les câbles de puissance et de commande des articulations du bras à travers celles-ci. A similar cover (17) is present on the part (1), this one finds its utility during the assembly of the robotic arm when it is necessary to pass the power and control cables of the joints of the arm through them.
Ces capots assurent l’étanchéité de l’intérieur, avec des joints toriques, sans vis, ni zone de rétention des bactéries. These covers seal from the inside, with O-rings, without screws or bacteria retention areas.
L’articulation comprend également un joint (16) qui assure l’étanchéité de l’articulation, et sa proximité avec le système de guidage (9) assure son bon fonctionnement. Les capots (17, 18) sont montés sans vis ou autres éléments de fixation apparents. L’articulation ainsi obtenue est étanche, et dépourvue de zones de rétention de bactéries. Le bras robotisé muni de telles articulations sera donc très facilement nettoyable et son utilisation adaptée aux domaines où l’hygiène est primordiale, tels que l’agroalimentaire ou le médical, et peut également être compatible avec des procédés de décontamination bactériologique et nucléaire. The articulation also includes a seal (16) which seals the articulation, and its proximity to the guidance system (9) ensures its correct operation. The covers (17, 18) are mounted without screws or other visible fasteners. The joint thus obtained is sealed, and devoid of bacterial retention zones. The robotic arm equipped with such joints will therefore be very easy to clean and its use adapted to areas where hygiene is essential, such as the food industry or the medical sector, and can also be compatible with bacteriological and nuclear decontamination processes.
Comme illustré sur la figure 2, les portées et les alésages (21, 22) des parties (1, 2) sont disposées de façon étagée afin que le montage ou le démontage de la partie (2) dans la partie (1) s’en trouve facilité. En effet, beaucoup de solutions de l’art antérieur divulguent des parties de bras robotisés qui comportent de nombreux sous-ensembles. Le montage de la deuxième partie dans la première nécessite alors d’être fait en plusieurs étapes, les sous-ensembles d’une partie et de l’autre étant alors montés successivement. Ceci est problématique non seulement lors du montage initial de l’articulation, car la durée de montage s’en trouve rallongée, mais également lors des opérations de maintenance lorsqu’il faut intervenir sur une pièce située au cœur de l’assemblage. As illustrated in Figure 2, the bearing surfaces and bores (21, 22) of the parts (1, 2) are arranged in a stepped fashion so that the assembly or disassembly of the part (2) in the part (1) is find it easy. Indeed, many solutions of the prior art disclose parts of robotic arms which have many subsets. The mounting of the second part in the first then needs to be done in several steps, the subassemblies of one part and the other then being mounted successively. This is problematic not only during the initial assembly of the joint, because the assembly time is thereby lengthened, but also during maintenance operations when it is necessary to intervene on a part located at the heart of the assembly.
Avec la conception de la présente invention il est facile de monter en avance des modules de la première partie (1) ou de la deuxième partie (2), et d’avoir des durées de montage faibles lors du montage initial de l’articulation. Il est également facile d’avoir des durées d’immobilisation du bras robotisé articulé faibles en cas de panne ou de maintenance, puisqu’il est possible de remplacer une partie défectueuse par un module de remplacement et de redémarrer rapidement le système comprenant le bras robotisé articulé. La partie défectueuse peut ensuite être démontée hors-site pour atteindre les pièces à maintenir, sans que le système utilisant le bras robotisé articulé soit à l’arrêt. L’assemblage de l’articulation peut également être testé avant d’être intégré dans le robot. With the design of the present invention, it is easy to mount modules of the first part (1) or of the second part (2) in advance, and to have short assembly times during the initial assembly of the joint. It is also easy to have low downtimes of the articulated robotic arm in the event of breakdown or maintenance, since it is possible to replace a defective part with a replacement module and to quickly restart the system including the robotic arm. Speak clearly. The defective part can then be dismantled off-site to reach the parts to be maintained, without the system using the articulated robotic arm being stopped. The joint assembly can also be tested before being integrated into the robot.

Claims

Revendications Claims
1. Articulation instrumentée pour bras robotisé comprenant : 1. Instrumented joint for robotic arm comprising:
- une première partie (1) du bras robotisé et une seconde partie (2) du bras robotisé, la première partie- a first part (1) of the robotic arm and a second part (2) of the robotic arm, the first part
(1) de l’articulation étant prolongée de manière monobloc, en son centre, par une forme cylindrique creuse (5a) traversant, en son centre, la deuxième partie (2), la première partie (1) est guidée en rotation autour d’un axe (5) général de révolution de l’articulation par rapport à la deuxième partie(1) of the joint being extended in a single piece, in its center, by a hollow cylindrical shape (5a) passing through, in its center, the second part (2), the first part (1) is guided in rotation around a general axis (5) of revolution of the joint with respect to the second part
(2) grâce à un premier système de guidage (6), (2) thanks to a first guidance system (6),
- un moteur (4) et un réducteur (3) destinés à entraîner en rotation relative la deuxième partie (2) par rapport à la première partie (1), - a motor (4) and a reducer (3) intended to drive the second part (2) in relative rotation with respect to the first part (1),
- le moteur (4) comprenant un stator (8) accouplé à la première partie (1), et un rotor (7) accouplé à un arbre central creux du réducteur (26), caractérisée en ce que l’articulation comprend : - the motor (4) comprising a stator (8) coupled to the first part (1), and a rotor (7) coupled to a hollow central shaft of the reducer (26), characterized in that the joint comprises:
- un deuxième système de guidage (9) hyperstatique et rotulant par rapport au premier système de guidage (6), et guidant au moins la rotation des première et deuxième parties (1, 2) autour de l’axe- a second guide system (9) hyperstatic and swiveling relative to the first guide system (6), and guiding at least the rotation of the first and second parts (1, 2) around the axis
(5), (5),
- au moins une jauge de déformation (10) montée sur une zone de déformation de la première partie (1) ou de la deuxième partie (2), et reliée à une carte électronique (15). - at least one strain gauge (10) mounted on a deformation zone of the first part (1) or of the second part (2), and connected to an electronic card (15).
2. Articulation selon la revendication 1, caractérisée en ce que le deuxième système de guidage (9) est déporté le long de l’axe (5) par rapport au premier système de guidage (6). 2. Articulation according to claim 1, characterized in that the second guide system (9) is offset along the axis (5) relative to the first guide system (6).
3. Articulation selon la revendication 1, caractérisée en ce que le premier système de guidage (6) est un roulement à billes. 3. Articulation according to claim 1, characterized in that the first guide system (6) is a ball bearing.
4. Articulation selon la revendication 1, caractérisée en ce que le deuxième système de guidage (9) rotulant est un roulement à billes. 4. Articulation according to claim 1, characterized in that the second guide system (9) swiveling is a ball bearing.
5. Articulation selon la revendication 1, caractérisée en ce qu’elle comprend un codeur magnétique5. Articulation according to claim 1, characterized in that it comprises a magnetic encoder
(13) et un codeur optique (12) mesurant chacun le déplacement angulaire du rotor (7) par rapport au stator (8), les codeurs étant reliés à la carte électronique (15). (13) and an optical encoder (12) each measuring the angular displacement of the rotor (7) relative to the stator (8), the encoders being connected to the electronic card (15).
6. Articulation selon la revendication 1, caractérisée en ce qu’elle comprend des moyens de freinage6. Articulation according to claim 1, characterized in that it comprises braking means
(14) du pivotement de la première partie (1) par rapport à la deuxième partie (2), tel qu’un frein à disque. 7. Articulation selon la revendication 1, caractérisée en ce que la deuxième partie (2) comporte au moins une portée cylindrique (21) venant s’emboîter lors du montage de l’articulation dans au moins un alésage cylindrique complémentaire (22) de la première partie (1). (14) of the pivoting of the first part (1) relative to the second part (2), such as a disc brake. 7. Articulation according to claim 1, characterized in that the second part (2) comprises at least one cylindrical bearing surface (21) which fits during assembly of the articulation in at least one complementary cylindrical bore (22) of the first part (1).
8. Articulation selon les revendications 1 et 5, caractérisée en ce que la carte électroniques (15) du bras motorisé d’un robot est placée à l’intérieur de l’articulation. 8. Joint according to claims 1 and 5, characterized in that the electronic card (15) of the motorized arm of a robot is placed inside the joint.
9. Articulation selon la revendication 8, caractérisée en ce que les première et deuxième parties (1, 2) sont fermées par des capots (17, 18), et la carte électronique ( 15) est directement accessible lorsqu’un opérateur ouvre le capot (18). 9. Articulation according to claim 8, characterized in that the first and second parts (1, 2) are closed by covers (17, 18), and the electronic card (15) is directly accessible when an operator opens the cover. (18).
10. Articulation selon la revendication 8, caractérisée en ce qu’elle comprend un joint (16) monté entre les première et deuxième parties (1, 2) pour assurer l’étanchéité. 10. Articulation according to claim 8, characterized in that it comprises a seal (16) mounted between the first and second parts (1, 2) to provide sealing.
11. Articulation selon la revendication 1, caractérisée en ce qu’elle comprend des câbles (27) de puissance, signal, et pilotage, cheminant intégralement à l’intérieur de l’articulation et au travers de la forme cylindrique creuse (5a), en étant en contact uniquement avec des pièces statiques de l’articulation. 11. Articulation according to claim 1, characterized in that it comprises power, signal and control cables (27), running entirely inside the articulation and through the hollow cylindrical shape (5a), by being in contact only with static parts of the joint.
PCT/EP2021/069861 2020-07-23 2021-07-15 Instrumented joint for robotic arm WO2022017932A1 (en)

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CN114918921A (en) * 2022-06-08 2022-08-19 苏州艾利特机器人有限公司 Redundant force sensor who detects and robot
CN114918921B (en) * 2022-06-08 2024-01-26 苏州艾利特机器人有限公司 Redundant force sensor and robot that detects

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