KR20160084030A - Hydraulic touch sensor for measuring a friction coefficient and a method for measuring the friction coefficient using the same - Google Patents

Abstract

The fluid tactile sensor includes a body portion, a touch pad portion, a measurement portion, an information processing portion, and a measurement portion. The body portion forms a storage space therein. The touch pad unit includes a touch pad fixed to an end of the body and being deformed according to the shape of the object in contact with the object. The measuring unit is fixed inside the storage space to photograph a deformed shape of the touch pad. The information processing unit extracts a deformed shape of the touch pad from the image photographed by the measurement unit, and receives information on the pressure applied to the touch pad. The measuring unit measures a slip index between the object and the touch pad based on information provided from the information processing unit.

Description

TECHNICAL FIELD [0001] The present invention relates to a fluid tactile sensor capable of measuring a sliding index and a sliding index measuring method using the same. [0002]

The present invention relates to a fluid tactile sensor capable of measuring a sliding index and a method of measuring a sliding index using the same. More particularly, the present invention relates to a fluid tactile sensor capable of measuring a sliding index at a contact portion between an object and a fluid tactile sensor And a method of measuring a slip index using the same.

In order to precisely control a robot or a manipulator, it is necessary to measure the slip index between the workpiece and the robot or the manipulator, and it is possible to control the optimum force for grasping the workpiece based on the measured slip index.

In general, a measurement sensor capable of measuring a six-axis force including a three-axis force and a three-axis moment is provided at an end of the robot or the manipulator, that is, an end effector. The external force is measured, The slip index between the workpiece and the robot or the manipulator is measured.

Korean Patent Application No. 10-2011-0036967 discloses a technology for measuring the six-axis force of the end of such a robot or a manipulator. In Korean Patent Application No. 10-2011-0036967, an arithmetic processing unit for performing a calculation of a six- And the like.

Korean Patent Application No. 10-2013-0046800 discloses a technique for measuring contact information by having a spherical surface and including a strain gauge therein.

As described above, techniques for using a strain gauge to measure the contact force at the end of a robot or a manipulator have been universally developed.

However, recently, in the development of robots for gripping objects, there has been an increasing technical demand for manufacturing grip parts of robots using soft flexible materials such as human fingers. Accordingly, while grasping objects with a flexible material, There is a demand for a slip-index measuring technique for a sliding surface.

Nevertheless, there is a technical limitation in applying a slip index measuring technique using a conventional strain gauge or the like to the manufacture of a grip portion of a flexible material.

SUMMARY OF THE INVENTION Accordingly, the present invention has been made in view of the above problems, and it is an object of the present invention to provide a fluid tactile sensor capable of more accurate sliding index measurement.

Another object of the present invention is to provide a method of measuring a slip index using the fluid tactile sensor.

According to an aspect of the present invention, there is provided a fluid tactile sensor including a body portion, a touch pad portion, a measurement portion, an information processing portion, and a measurement portion. The body portion forms a storage space therein. The touch pad unit includes a touch pad fixed to an end of the body and being deformed according to the shape of the object in contact with the object. The measuring unit is fixed inside the storage space to photograph a deformed shape of the touch pad. The information processing unit extracts a deformed shape of the touch pad from the image photographed by the measurement unit, and receives information on the pressure applied to the touch pad. The measuring unit measures a slip index between the object and the touch pad based on information provided from the information processing unit.

In one embodiment, a database storing slip index information for an optimal grasp according to a kind of objects, and a slip index measured by the measurement unit and an optimal slip index of the database, And a control unit for controlling the movement of the body part for gripping.

In one embodiment, the metering unit includes: a contact area measuring unit that measures a contact area of the object with respect to the touch pad from a deformed shape of the touch pad; And a vertical force measuring unit for measuring the vertical force applied to the touch pad by the contact of the object from the information about the pressure.

In one embodiment, the interior of the touch pad is filled with fluid, and the touch pad may protrude outward in a hemispherical shape.

According to another aspect of the present invention, there is provided a sliding index measuring method,

In one embodiment, the step of comparing the measured slip index with the previously stored optimal slip index may further include changing the contact force with the object for grasping the object.

In one embodiment, the step of measuring the normal force may include dividing the touch pad into a plurality of fine patterns, applying a force balance equation to each of the divided fine patterns, Calculating force in the vertical direction, calculating forces in the X, Y and Z axes at the respective fine surface areas from the left and right and upward and downward forces acting on the respective fine surface areas, And summing the forces in the Z-axis direction of the touch pad to calculate the normal force acting on the entire touch pad.

In one embodiment, in the step of calculating the left and right vertical force acting on each fine face,

식 (2)

Equation (2)

(F _l : leftward force acting on fine face, F _r : rightward force acting on fine face, F _u : upward force acting on fine face, F _d : downward force acting on fine face, p : Pressure acting on fine cotton, S: area of fine cotton)

The force equilibrium equation of the above equation (2) can be applied.

In one embodiment, measuring the slip index can be performed by dividing the measured vertical force by the measured contact area.

According to embodiments of the present invention, when an object comes into contact with a touch pad including a fluid, the sliding index between the touch pad and the object can be measured based on the deformed shape of the touch pad and the pressure applied to the touch pad Therefore, it is possible to omit a separate measuring sensor using a strain gauge or the like in the past, and it is possible to accurately measure the slip index with a relatively simple structure.

In addition, since the control for optimal gripping can be performed by comparing the measured slip index with the previously stored reference slip index, it is possible to grasp the object with the optimum force, and to prevent breakage or slip of the object.

Particularly, since the fluid tactile sensor includes a fluid inside the touch pad and the touch pad is formed of an elastic material, when the touch sensor is applied to a robot or a manipulator, a mechanism similar to a human gripping object This is possible.

Further, in the measurement of the vertical force, the touchpad is divided into minute facets, and then the normal force is calculated through a force acting on the minute facet through the equilibrium equations. Conventionally, The vertical force acting on the touch pad can be calculated without performing the displacement measurement of the side end portion through the marking.

That is, without measuring tension or force information acting on the end portion of the touch pad, only the information about the pressure applied to the entire touch pad, the shape and area of the touch pad, It is possible to calculate the vertical force applied to the surface.

1 is a schematic diagram showing a fluid tactile sensor capable of measuring a sliding index according to an embodiment of the present invention.
2 is a flowchart illustrating a method of measuring a slip index using the fluid tactile sensor of FIG.
Fig. 3 is a plan view showing a state in which the contact area measuring unit of Fig. 1 measures the contact area. Fig.
4 is a flowchart showing a vertical force measuring step in the vertical force measuring unit of FIG.
Fig. 5 is a schematic diagram showing a state in which a contact force acts when an object contacts the fluid tactile sensor of Fig. 1. Fig.
FIG. 6 is a schematic diagram showing a state in which the touch pad is divided into minute facets in FIG.
FIG. 7 is a schematic diagram for deriving the equilibrium equation at each fine surface in FIG.
Fig. 8 is a schematic diagram showing forces acting on the respective minute surface areas in Fig. 4 on the XY plane.
Fig. 9 is a schematic diagram showing forces acting on the respective minute surface areas of Fig. 4 on the XZ plane.

While the present invention has been described in connection with what is presently considered to be the most practical and preferred embodiment, it is to be understood that the invention is not limited to the disclosed embodiments. It is to be understood, however, that the invention is not intended to be limited to the particular forms disclosed, but on the contrary, is intended to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the invention. Like reference numerals are used for like elements in describing each drawing. The terms first, second, etc. may be used to describe various components, but the components should not be limited by the terms.

The terms are used only for the purpose of distinguishing one component from another. The terminology used in this application is used only to describe a specific embodiment and is not intended to limit the invention. The singular expressions include plural expressions unless the context clearly dictates otherwise.

In the present application, the term "comprises" or "comprising ", etc. is intended to specify that there is a stated feature, figure, step, operation, component, But do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, parts, or combinations thereof.

Unless defined otherwise, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Terms such as those defined in commonly used dictionaries are to be interpreted as having a meaning consistent with the contextual meaning of the related art and are to be interpreted as either ideal or overly formal in the sense of the present application Do not.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

1 is a schematic diagram showing a fluid tactile sensor capable of measuring a sliding index according to an embodiment of the present invention. 2 is a flowchart illustrating a method of measuring a slip index using the fluid tactile sensor of FIG. Fig. 3 is a plan view showing a state in which the contact area measuring unit of Fig. 1 measures the contact area. Fig.

1 and 2, the fluid tactile sensor 10 according to the present embodiment includes a body part 100, a touch pad part 110, a measuring part 130, an information processing part 140, a measuring part 150 A control unit 160, and a data base 170.

The body part 100 corresponds to, for example, the end of a finger or a manipulator of the robot, and can be used for grasping the object 1.

A storage space 101 is formed in the body part 100 and the measurement part 130 is positioned inside the storage space 1. [

The touch pad unit 110 includes a plate portion 111 and a touch pad 112 and is fixed to a lower portion of the body portion 100. The plate portion 111 separates the storage space 1 of the body portion 100 from the touch pad 112 and a fluid is sealed inside the touch pad 112.

Since the touch pad 112 is formed of a material having a predetermined elastic force and the fluid is sealed inside the touch pad 112, the shape of the touch pad 112 is deformed when the object 1 contacts the outer surface.

Particularly, since the interior of the touch pad 112 is filled with a fluid and protrudes outward in a hemispherical shape, the touch pad 112 is pressed in the outward direction by the fluid. Accordingly, when the object 1 contacts the outer surface and the fluid receives a pressure larger than the pressure externally applied, the shape of the touch pad 112 is deformed.

The measurement unit 130 photographs the deformed shape of the touch pad 112. For this purpose, a pair of cameras 131 and 132 are arranged to face the touch pad 112. [ In this case, the measuring unit 130 may include only one camera, or may photograph a deformed shape of the touch pad 112 in a stereo manner when the camera includes a pair of cameras.

The information about the deformed shape of the touch pad captured by the measuring unit 130 is provided to the information processing unit 140 so that the sensed data is processed to extract the deformed shape of the touch pad.

The plate part 111 forms a boundary between the body part 100 and the touch pad 112 so that the touch pad 112 comes into contact with the object 1 and contacts the object 1 When a predetermined pressure is applied, the pressure applied to the touch pad 112 is measured. For this purpose, the plate portion 111 may be provided with a separate pressure measuring sensor.

Information about the pressure applied to the touch pad 112 measured by the plate portion 111 is provided to the information processing unit 140 so that the information processing unit 140 extracts accurate pressure information.

That is, the information processing unit 140 processes the information about the deformed shape of the touch pad 112 measured by the measuring unit 130 and the information about the pressure measured by the plate unit 111, Information on the shape and pressure of the processed touch pad is inputted to the measuring unit 150 (step S10).

The measuring unit 150 includes a contact area measuring unit 151 and a vertical force measuring unit 152 and measures a contact area and a vertical force based on the information about the shape and pressure of the touch pad input from the information processing unit 140 (Steps S20 and S30).

3, when the object 1 touches the touch pad 112, when the measurement unit 130 photographs the deformed shape of the touch pad 112, The area S in which the object 1 and the touch pad 112 are in contact with each other is deformed and displayed.

Accordingly, the contact area measuring unit 151 receives the processed image data from the information processing unit 140 as shown in FIG. 3, and measures the area of the contact area S (step S20).

The vertical force measuring unit 152 measures the vertical force applied to the touch pad 112 by the contact of the object 1 based on information about the shape and pressure of the touch pad from the information processing unit 140 (Step S30). In this case, a specific method of measuring the vertical force by the vertical force measuring unit 152 will be described with reference to FIGS. 4 to 9 described later.

Thereafter, the measuring unit 150 measures a slip index between the object 1 and the touch pad 112 based on the measurement result of the contact area and the vertical force (step S40).

In this case, the slip index may be defined as a value obtained by dividing the contact area by the vertical force.

In this way, the information about the slip index measured by the measuring unit 150 is provided to the controller 160. When the object 1 touches the touch pad 112, And obtains information on the actual slip of the vehicle.

Meanwhile, in the present embodiment, slip index information for optimal grip according to the type of objects can be stored in the database 170. That is, the object 1 can be variously classified according to the material, the shape, and the like, and the optimal slip index information for optimal gripping can be stored in the database 170 according to the type of each object.

For example, the optimum slip index information can be stored according to materials such as a glass-made cup, a paper-made cup, and a rubber-made cup, and optimal slip index information can be stored depending on the size or shape have.

Therefore, when the optimal slip index information for gripping is received from the database 170 according to the type of the object 1 to be gripped or the like, the control unit 160 controls the measuring unit 150 And controls or changes the contact force with the object 1 (S50).

That is, the controller 160 controls the contact state with the object 1 so that the optimal slip index provided in the database 170 is equal to the actually measured slip index. Accordingly, the fluid tactile sensor 10 can grasp the object 1 with an optimal force.

For example, the control unit 160 may move the body 100 toward or away from the object 1 so that the contact area with the object 1 or the vertical force So as to maintain an optimal slip index.

Hereinafter, a method of calculating the total resultant force of the normal force acting on the touch pad 112, that is, the force acting in the Z direction, by the vertical force measuring unit 152 will be described in detail.

4 is a flowchart showing a vertical force measuring step in the vertical force measuring unit of FIG. Fig. 5 is a schematic diagram showing a state in which a contact force acts when an object contacts the fluid tactile sensor of Fig. 1. Fig. FIG. 6 is a schematic diagram showing a state in which the touch pad is divided into minute facets in FIG. FIG. 7 is a schematic diagram for deriving the equilibrium equation at each fine surface in FIG. Fig. 8 is a schematic diagram showing forces acting on the respective minute surface areas in Fig. 4 on the XY plane. Fig. 9 is a schematic diagram showing forces acting on the respective minute surface areas of Fig. 4 on the XZ plane.

4 and 5, for the measurement of the vertical force, a horizontal base of the touch pad 112, that is, a portion contacting the plate portion 111, The sum of the pressure p applied to the bottom of the touch pad by the fluid and the force applied to the corner of the touch pad 112 by the touch pad 112 is equal to the sum of the pressure applied to the bottom of the touch pad 112 Is defined as an applied force (F _base ), which can be expressed as a force balance equation as shown in the following equation (1).

식 (1)

Equation (1)

4 and 6, in step S30, the touch pad 112 is divided into minute areas as shown in FIG. 6 (step S31). In this case, when the touch pad 112 is divided into m lines in the Z-axis direction, forces (F ₁ , F ₂ , F ₃ ,. (F _m-2 , F _m-1 , and F _m ), the sum of the Z-axis directions acting on the touch pad 112, that is, the normal force, can be calculated.

An arbitrary minute surface area of the touch pad 112 thus divided is shown in FIG.

Referring to FIGS. 4 and 7, F _r , F _l , F _u and F _d are respectively calculated by applying a force equilibrium equation to each of the fine patterns (step S 32).

In this case, F _r , F _l , F _u , and F _d are forces in the right direction, force in the left direction, force in the upper direction, Direction, the area of the fine pattern area is represented by S, and the pressure acting on the fine pattern area is represented by P.

That is, when the force equilibrium equation of the following equation (1) is applied to the micro face, it is described as the following equation (2).

식 (2)

Equation (2)

Fig. 8 is a diagram showing a micro pattern on an arbitrary XY plane. When the force equilibrium equation is described on an XY plane with respect to the arbitrary fine pattern, the equation (2) can be expressed by the following equations (3) and Can be expressed.

In this case, (i, j) cell is a corresponding micro-scale to which the equilibrium equations are applied, and (i, j + 1) do. Accordingly, θ _{xy (i, j)} is the XY plane corresponding smile myeonso (i, j) of one end of the cell is defined as a tangential direction and the X axis and the _{angle, θ xy (i, j +} 1) are XY on the Is defined as the angle formed by the tangential direction of one end of the (i, j + 1) cell adjacent to the (i, j) cell on the plane and the X axis.

식 (3)

Equation (3)

식 (4)

Equation (4)

Fig. 9 is a diagram showing a micro pattern on an arbitrary XZ plane. When a force equilibrium equation is described on an XZ plane with respect to the arbitrary fine pattern, the above equation (2) can be expressed by the following equation (5) .

Similarly, θ _{z (i, j)} is defined as an angle formed by the tangential direction of one end of the corresponding fine surface (i, j) cell on the XZ plane and the X axis _, Is defined as the angle formed by the tangential direction of one end of the (i, j + 1) cell adjacent to the (i, j) cell of the phase and the X axis.

식 (5)

Equation (5)

Expressions (6), (7), and (8) below are expressed more specifically as the X-axis, Y-axis, and Z- .

식 (6)

Equation (6)

식 (7)

Equation (7)

식 (8)

Equation (8)

In this case, S _x corresponds to the area in the X-axis direction of the corresponding micro face, S _y corresponds to the area in the Y-axis direction of the corresponding micro face, and S _z corresponds to the area in the Z axis direction of the corresponding micro face.

(9), and if the corresponding fine pattern is in the third and fourth quadrants in the XY plane, the equation (6) .

식 (9)

Equation (9)

식 (10)

Equation (10)

Equation (7) can be expressed as Equation (11) if the corresponding fine surface is in the first and fourth quadrants in the XY plane, and Equation (12) is obtained if the corresponding fine surface is in the second and third quadrants in the XY plane. Is modified.

식 (11)

Equation (11)

식 (12)

Equation (12)

Further, the component in the Z-axis direction at the corresponding fine surface of the equation (8) is corrected to the equation (13) in consideration of the directionality, and further, F _r , F _l , F _u , F _d Lt; / RTI >

식 (13)

Equation (13)

식 (14)

Equation (14)

As described above, F _r , F _l , F _u , and F _d in the corresponding small surface area (i, j) cell can be calculated using the above equations (9) to (14). That is, it is possible to calculate all of the forces in the four directions acting on the fine surface.

After calculating the forces F _r , F _l , F _u , and F _d in the four directions acting on the fine surface as described above, the force F _r , F _l , F _u , F F _x , F _y , and F _z obtained by converting _ds into the X-axis, Y-axis, and Z-axis directions are calculated for the corresponding small facet (step S33).

Thereafter, all of the forces F _z in the Z-axis direction calculated at the respective fine face areas are summed (step S34), and the force acting on the touch pad 112 in the Z-axis direction, that is, the vertical force can be measured.

As described above, in this embodiment, a marker such as an edge marker is used for the touch pad 112 to measure the displacement of the side surface of the touch pad 112, or information about the force acting on the side surface of the touch pad 112 By dividing the touch pad 112 into a plurality of minute areas on the basis of the information about the deformed shape of the touch pad 112 and the pressure applied to the touch pad 112 without inputting the touch, The vertical force acting on the pad 112 can be calculated.

In this way, based on the information on the calculated vertical force, the measuring unit 150 measures the slip index and provides the related information to the controller 160. [

According to this embodiment, when the object comes into contact with the touch pad including the fluid, the sliding index between the touch pad and the object can be measured based on the deformed shape of the touch pad and the pressure applied to the touch pad Therefore, it is possible to omit a separate measuring sensor using a strain gauge or the like in the past, and it is possible to accurately measure the slip index with a relatively simple structure.

In addition, since the control for optimal gripping can be performed by comparing the measured slip index with the previously stored reference slip index, it is possible to grasp the object with the optimum force, and to prevent breakage or slip of the object.

Particularly, since the fluid tactile sensor includes a fluid inside the touch pad and the touch pad is formed of an elastic material, when the touch sensor is applied to a robot or a manipulator, a mechanism similar to a human gripping object This is possible.

Further, in the measurement of the vertical force, the touchpad is divided into minute facets, and then the normal force is calculated through a force acting on the minute facet through the equilibrium equations. Conventionally, The vertical force acting on the touch pad can be calculated without performing the displacement measurement of the side end portion through the marking.

That is, without measuring tension or force information acting on the end portion of the touch pad, only the information about the pressure applied to the entire touch pad, the shape and area of the touch pad, It is possible to calculate the vertical force applied to the surface.

It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit or scope of the present invention as defined by the following claims. It can be understood that it is possible.

The fluid tactile sensor capable of measuring the slip index according to the present invention and the slip index measuring method using the fluid tactile sensor have industrial applicability that can be used for robots that hold objects with their fingers.

10: fluid tactile sensor 1: object
100: body part 110: touch pad part
111: plate portion 112: touch pad
130: measuring unit 140: image processing unit
150: Calculator 151: Information input unit
152:

Claims (9)

A body portion forming a storage space therein;
A touch pad portion fixed to an end of the body portion and including a touch pad which is in contact with an object and is deformed according to the shape of the object;
A measurement unit fixed inside the storage space to capture a deformed shape of the touch pad;
An information processing unit for extracting a deformed shape of the touch pad from the image photographed by the measuring unit and inputting information about a pressure applied to the touch pad; And
And a measuring unit for measuring a slip index between the object and the touch pad based on information provided from the information processing unit. The method according to claim 1,
A database storing slip index information for optimal grasping according to the types of objects; And
And a control unit for comparing the slip index measured by the measuring unit and the optimal slip index of the database to control the movement of the body for gripping the object. The apparatus according to claim 1,
A contact area measuring unit for measuring a contact area of the object with the touch pad from a deformed shape of the touch pad; And
And a vertical force measuring unit for measuring the vertical force applied to the touch pad by the contact of the object, based on the information about the deformed shape of the touch pad and the pressure applied to the touch pad. The method according to claim 1,
Wherein a fluid is filled in the inside of the touch pad, and the touch pad protrudes outward in a hemispherical shape. Inputting information about a shape of a touch pad deformed in contact with an object and a pressure applied to the touch pad in contact with the object;
Measuring a contact area where the object contacts the touch pad based on information about the shape of the touch pad;
Measuring a vertical force applied to the touch pad by the contact of the object based on the shape of the touch pad and the pressure applied to the touch pad; And
Measuring a slip index between the object and the touch pad based on the contact area and the vertical force. 6. The method of claim 5,
And comparing the measured slip index with a previously stored optimal slip index to change the contact force with the object for grasping the object. 7. The method of claim 6, wherein the measuring the vertical force comprises:
Dividing the touch pad into minute facets;
A force balance equation is applied to each of the subdivided areas to thereby calculate left and right and upward and downward forces acting on the respective minute facets;
Calculating force in the X, Y, and Z axial directions at the respective fine surface areas from the lateral force and the vertical force acting on each of the fine surface areas; And
Calculating a vertical force acting on the entirety of the touch pad by summing the forces in the Z-axis direction at the respective fine surface areas. 8. The method according to claim 7, wherein, in the step of calculating left and right and upward and downward forces acting on the respective minute facets,

Equation (2)
(F _l : leftward force acting on fine face, F _r : rightward force acting on fine face, F _u : upward force acting on fine face, F _d : downward force acting on fine face, p : Pressure acting on fine cotton, S: area of fine cotton)
Wherein the force equilibrium equation of the formula (2) is applied. 7. The method of claim 6, wherein measuring the slip index comprises:
And measuring the vertical force by dividing the measured vertical force by the measured contact area.

Images