JPH0146276B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method and device for controlling the tracing motion of working machines such as industrial robots, and in particular, the present invention relates to a method and device for controlling the tracing motion of working machines such as industrial robots, and in particular, when the object to be traced has a portion with a small radius of curvature. The present invention relates to a tracing operation control method and apparatus suitable for performing smooth tracing operations.

[Prior Art] The conventional tracing motion control method operates a working machine in a certain basic motion direction,
A common method has been to use a sensor to detect the unevenness of an object in a direction perpendicular to the unevenness, and to drive a working tool attached to the sensor or a working machine depending on the shape of the unevenness. In this method, the sensor or the working tool is driven in a direction perpendicular to the basic direction of movement, depending on the shape of the object. Therefore, if the shape of the object includes a portion that is perpendicular or nearly perpendicular to the basic motion direction, the tracing motion will not proceed. Another drawback is that the posture of the sensor or power tool relative to the object and the speed of movement along the object cannot be kept constant. This drawback appears, for example, in a welding robot as a problem in that uniform welding cannot be performed.

As a method to solve these problems, the applicant has already proposed Japanese Patent Application Laid-Open Nos. 55-188376 and 58
−34781 etc. are proposed. In these methods,
The basic idea was to focus on information on the tangential direction of the object obtained as a result of sensor detection, and to follow the changing tangential direction to ensure that the basic movement direction of the movement remains consistent.

[Problems to be Solved by the Invention] However, in these methods, the shape of the surface of the object is approximated as a polygonal line, and the length of each polygonal line is constant regardless of the curvature of the target object.
Therefore, curvature detection is performed every fixed distance of movement both in areas where the change in the tangential direction of the object surface is large, that is, the radius of curvature is small, and in areas where the change in the tangential direction is small. In areas where the direction of the tangent changes rapidly, the error in the tracing operation itself may become large, or in extreme cases, the error may go out of the range that can be detected by the sensor during the tracing operation, and the tracing operation may not proceed. There were drawbacks such as interference with the

SUMMARY OF THE INVENTION An object of the present invention is to provide a profiling operation control method and apparatus that can smoothly continue the profiling operation even if the amount of change in the tangential direction of the object, that is, the radius of curvature, changes significantly during the profiling operation.

[Means for Solving the Problems] In order to achieve the above object, the present invention uses a sensor attached to the tip of a moving object to detect the relative distance to the object to specify a tangent in a specified plane near the object. The tangent in the specified plane is calculated based on the relative distance between the sensor and the object and the position of the moving body in the three-dimensional space, and the set movement is performed on the extension of this tangent in the specified direction. In a tracing control method in which the next operation target point is set at a point separated by a distance, and the sensor is moved toward the operation target point, the relative distance between the sensor and the object is constantly monitored, and the sensor is moved only by the set movement distance. A tracing control method is proposed in which the tangent is recalculated and a new target motion point is set each time a remote target point is reached or the relative distance between the sensor and the object exceeds a predetermined value.

A plurality of the sensors are provided in a plane that intersects with the designated plane, and based on the output of the sensor, the normal direction of the three-dimensional object in the intersecting plane is calculated, and a point on the three-dimensional object is calculated. It is also possible to determine the normal line of the tangential plane at and regulate the direction of the sensor so that it is within a certain angle with respect to the normal line.

The sensor does not need to be oriented exactly in the direction normal to the tangent line, and may be moved while maintaining a constant angle within a range that does not cause an error of more than a predetermined value in distance measurement.

The present invention also provides a driving means for moving a sensor attached to the tip of a moving body to detect a relative distance to a target object by a set travel distance in a tangential direction near the target object, and a relative distance between the sensor and the target object. and a first step that calculates the position of the object and the tangent in the specified plane at the position of the object based on the position of the moving object in the three-dimensional space and outputs the target point of operation to the driving means.
a calculation means; the position of the object is determined each time the tip of the moving body reaches a target point of operation separated by the set movement distance or the relative distance between the sensor and the object exceeds a predetermined value during the movement; The present invention proposes a profiling control device including: and a second calculation means for outputting a command to the first calculation means to recalculate the tangent line at that position and to newly set an operation target point.

[Function] In the present invention, when the sensor is moved in the tangential direction of the object surface by the reference sampling distance, if the relative distance between the sensor and the object exceeds a predetermined value during the movement, the reference sampling distance is Regardless of the situation, the position of the object and the tangent at that position are recalculated and a new target point is set. Even at corners where the amount of change is large, that is, the radius of curvature is small, stable and accurate tracing control is always possible.

In addition, a plurality of sensors are arranged within a cross section in a direction intersecting (for example, orthogonal to) the designated plane of this tracing operation, and within this cross section, the cross section of the three-dimensional object is determined based on the difference in the outputs of these sensors. By restricting the direction of the sensor in the normal direction, the tracing operation of the three-dimensional object, which also has a curved surface in the cross-sectional direction, can be performed more accurately.

[Example] Next, an example of the present invention will be described with reference to the drawings.

FIG. 1 is a diagram showing the cross-sectional shape of one of the objects W to be subjected to the tracing operation of the present invention. In this case, the radius of curvature is small at both ends and large at the center. As an object of such a shape, the second
There are runner blades for water turbines as shown in the figure.
Along the surface of this type of object, shape measurement work,
It is possible to perform painting work, grinding work, etc. As a representative example of a working machine that performs such various tasks, an industrial robot shown in FIG. 3 will be described here.

In FIG. 3, the robot 1 moves horizontally above the first column 3 using the hydraulic cylinder 2.
A first moving body 4 that reciprocates in the axial direction, and a second moving body that moves in the vertical direction, that is, in the Z-axis direction, by a hydraulic cylinder 6 along a second column 5 that is provided upright above the first moving body 4. 7, a third movable body 9 that is attached to the second movable body 7 and reciprocates in the horizontal direction perpendicular to the X axis, that is, the Y direction by a hydraulic cylinder 8, and a vertical axis that is fixed to the tip of the third movable body 9, that is, SW. Swing wrist block 1 that rotates around the axis
0, and a bending shaft 11 which is fixed to the swing wrist block 10 and rotates around the horizontal axis, that is, the BD axis.
It is equipped with The bending shaft 11 is equipped with a sensor 12 for detecting the proximity distance to the workpiece.
and 13 are attached via a sensor mounting plate 14. The two sensors 12 and 13 are arranged so that their main axes 121 and 131 are parallel to each other, and the sensor main axis 1
When the bending shaft 11 is rotated so that the bending shafts 21 and 131 are horizontal, they are arranged at positions separated by a distance Ld so that they are located above and below each other within the same vertical plane. The sensors 12 and 13 are shown to magnetically detect the proximity distance to the object using eddy currents.

FIG. 4 is a block diagram of the control system of the robot 1. In the figure, position commands from a control computer 15 consisting of a microcomputer or the like are distributed to predetermined axes at an interface 16 and sent to positioning devices 17 to 21 for each axis.
Furthermore, for example, the position command sent to the X-axis positioning device 17 is calculated by a subtraction circuit 171 to calculate the difference between the position command and the current position of the robot X-axis sent from the position detector 174, and the result is sent to the servo circuit 172. . The output of the servo circuit 172 is transmitted to the robot main body X-axis mechanism 173 including the servo valve, cylinder 2, etc.
drive. The position is fed back by the position detector 174 and is also fed back to the computer 1.
5 can be loaded. In addition, the sensor 12,
The proximity distance information obtained from the sensor 13 is taken into the computer 15 via the sensor interface 22.

FIG. 5 is a diagram showing details of the sensor interface 22. The signals of sensors 12 and 13 are
The signal is linearized and amplified by sense amplifiers 122 and 132. Further, the output of the sense amplifier 122 is sent to the comparison circuit 201 along with the output from the reference signal generation circuit 181. The outputs of the sense amplifiers 122 and 132 are both sent to the comparator circuit 200, and the output is sent to the comparator circuit 200 via the absolute value calculation circuit 190.
It is sent to the comparison circuit 202 together with the output of the reference signal generation circuit 182. Furthermore, the comparison circuit 201,
The output of 202 is taken into the computer 15.

Next, an example of the tracing operation control method according to the present invention will be explained with reference to FIGS. 6 to 9. FIG. 6 is a diagram showing a tracing operation in the horizontal cross-sectional direction according to the present invention, and FIGS. 7 and 8 are diagrams showing an example of a method for positioning the sensor in the vertical cross-sectional direction of the object shown in FIG.

The basic idea of the present invention will be explained with reference to FIG. It should be noted that the relative distance Ss between the robot 1 and the object to be adjusted initially is a value approximately halfway between the upper limit Smax and lower limit Smin of the detectable distance range of the sensor 12, and in the following explanation, this will be referred to as the standard detection distance. That's what it means.

First, robot 1 is positioned at the starting point _Q0 . To do this, the sensors 12 and 13 are oriented substantially perpendicularly to the surface of the object W, and the sensors 12 and 13 are
13 until both outputs reach the standard detection distance Ss.
Each axis of the robot 1 including the wrist bending axis is driven.

Here, the position of the point on the object W is determined by the sensor 12
It can be calculated from the detection distance and the position of the sensor itself. Further, the inclination of the object W in the vertical cross section is approximately determined based on the positions of two points on the object W obtained from the sensors 12 and 13 as the inclination of a straight line connecting these points.

In the tracing operation, the sensor 12
The robot 1 is started by moving in a direction perpendicular to the main axis 121 of the robot 1 toward a point _R1 located a predetermined reference sampling distance _L0 . The tracing operation is performed at point Q ₀
This is done smoothly and at a uniform speed by performing linear interpolation between and the point _R1 . During this operation, the outputs of the sensors 12 and 13 change moment by moment depending on the shape of the object W. If the outputs of the sensors 12 and 13 change significantly by the time the robot 1 reaches point _R1 , and the outputs of the comparison circuits 201 and 202 in FIG.
Find the position of point _Q1 on the object W based on the output data. Furthermore, if the outputs of the sensors 12 and 13 do not change significantly and the outputs of the comparison circuits 201 and 202 do not change by the time point _R1 is reached,
As shown in Figure 9, upon reaching point _R1 ,
Find the position Q ₁ on the object W.

In any of these cases, a straight line connecting point Q ₀ and point Q ₁ is an approximate tangent at point Q ₁ . Also,
Similarly, by using the two output data of the sensors 12 and 13, it is possible to obtain an approximate tangent in the vertical section at the point _Q1 . Therefore,
On the extension of the straight line connecting point Q ₀ and point Q ₁ , point R ₂ , which is separated from point Q ₁ by reference sampling distance L ₀ , can be determined as the operation target point.

The tracing operation continues as the robot 1 moves from point _Q1 to point _R2 , as shown in FIGS. 6 and 9. Even during this operation, the outputs of the comparison circuits 201 and 202 are monitored, and the position of point Q ₂ on the object W is determined when either output changes or when the operation target point R ₂ is reached. , further calculate the approximate tangent direction or tangent plane within the specified plane at point Q ₂ , and similarly calculate the point
On the straight line connecting Q ₁ and point Q ₂ , set point R ₃ at a reference sampling distance L ₀ from point Q ₂ as the operation target point,
Continue moving towards this point.

The amount of change in the attitude of the sensor main shafts 121, 131 from the position where point Qi was detected to point Ri+1 is such that the amount of change in the horizontal plane corresponds to the swing axis rotation angle ΔSW of the robot 1, and the amount of change in the vertical plane corresponds to the rotation angle ΔSW of the swing axis of the robot 1. The amount of change also corresponds to the bending axis rotation angle ΔBD. Therefore, the swing axis rotation angle ΔSW at point Ri+1 is such that the sensor main axis 121 is aligned with the straight line QiRi+1.
Similarly, the bending axis rotation angle ΔBD can be determined as the rotation amount for driving the sensor shaft 121 to be perpendicular to the tangent in the vertical section at point Qi. Note that due to the structure of the robot 1, when the wrist swing axis or bending axis is operated, the hand position P targeted by the sensor changes. By correcting and driving the Y and Z axes, control is performed so that the hand position P does not change.

Here, the function of comparison circuits 201 and 202 will be explained in detail. First, the comparison circuit 201 receives the output signal of the sensor 12, that is, the object W.
and the sensor 12, and if they are too close and the distance is less than the set lower limit Snear, or if they are too far apart and the distance is the set upper limit
This is a circuit for determining when the value exceeds Sfar. Here, it goes without saying that each numerical value should be determined so that the relationship Smin<Snear<Ss<Sfar<Smax is established. Therefore, the comparison circuit 201 determines that the difference between the direction of the profiling motion on the object W and the tangential direction of the actual surface of the object W has become large to some extent, and the relative distance between the sensor and the object has exceeded a predetermined value. This is a circuit that determines. Also,
The comparison circuit 202 calculates the difference between the outputs of the sensors 12 and 13, that is, the direction of the main axis of the two sensors, and the object W.
A circuit that gives a quantity corresponding to the difference from the tangential direction in the vertical section of the surface and determines when the difference ΔS between the outputs S ₁₂ and S ₁₃ of both sensors becomes larger than a predetermined threshold ΔS ₀ . It is.

From the above, these comparison circuits 201, 20
2, it is possible to determine whether or not the tangential direction of the object W that is assumed based on the sensor detection results in the actual tracing operation is different from the actual tangential direction of the object W. Compared to the conventional tracing motion control method, the tracing motion of a portion of the object with a small radius of curvature can be executed with less error and with higher precision.

Even if the outputs of the comparison circuits 201 and 202 do not change, calculating a new tangent line every time the reference sampling distance L ₀ is moved makes it possible to perform fine-grained calculations even in parts with a large radius of curvature, that is, with a gentle shape of the object. The tangent approximation helps to perform highly accurate tracing operations.

However, in the conventional example, if the tangent line was constantly calculated for each minute sampling distance, the measurement errors of the sensor would accumulate and greatly affect the accuracy of the tangent calculation, making it impossible to perform stable tracing operations.
With the method of the present invention, stable tracing control is always possible in areas where the radius of curvature is large or small.

In addition, in the above embodiment, two sensors are provided,
Although an example of tracing in the horizontal direction has been shown, the tracing operation is not limited to a horizontal plane, and the present invention is applicable to tracing operations performed in any plane or curved surface. . However, within the plane or curved surface on which the tracing operation is performed, 2
The sensors must be arranged so that two sensors are not included at the same time.

Further, although the present invention has been explained using a robot with an orthogonal coordinate system as an example, it is clear that the present invention can be applied to a robot having an arbitrary configuration such as an articulated type, or a working machine such as a traveling trolley.

Furthermore, the functions of the tracing operation described in the embodiments of the present invention include two functions: tangent detection within the tracing operation plane and tangent detection in a plane different from the tracing operation plane (in the vertical plane in the above embodiment). However, among these, it is also possible to implement only the function of detecting tangents within the tracing operation plane.

The sensors 12 and 13 are not only the proximity distance sensor shown in this embodiment, but also a stylus type sensor with a potentiometer or the like biased by a spring, an ultrasonic type distance sensor, a distance sensor using a laser beam, etc.
Furthermore, it is also possible to adopt a sensor method that detects distance through image processing using a television camera and spot light.

In the above embodiment, an example was shown in which the sensor output signal comparison circuit and the like were configured with a specific electronic circuit, but it is also possible to execute such signal processing calculations in the form of software in the computer 15. .

Although the working tools are not shown here, for example, a coating elastic body, a welding torch, a grinder, and other working tools are arranged at the hand of the robot, and the working point positions of these tools are made to match the position P of the hand of the robot 1. Alternatively, by arranging the tool so as to maintain a constant positional relationship with the hand position and calculating and controlling the tool work point position by regarding it as the hand position of the robot 1, tracing work using the power tool becomes possible.

[Effects of the Invention] According to the present invention, even when the surface shape of the object changes in a complex manner and the curvature changes significantly in some parts, the tangent line can be approximated by a line segment with a length corresponding to the curvature. Therefore, not only is stable tracing operation possible in areas with a large radius of curvature, but also highly accurate tracing operation is possible even in areas where the radius of curvature is small, that is, the direction of the tangent changes rapidly, and the shape of the object can be adjusted. Stable and smooth tracing control is possible regardless of the

Furthermore, since the output of the sensor, that is, the distance between the object and the sensor is constantly monitored, the sensor never loses sight of the object or the sensor interferes with the object.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing an example of an object to be subjected to the tracing operation of the present invention, FIG. 2 is a view showing the external appearance of an example of the object, and FIG. 3 is an example of a working machine to which the present invention is applied. A perspective view of the robot; FIG. 4 is a block diagram showing the control circuit of the profiling control device of the present invention;
Fig. 5 is a circuit diagram of a sensor constituting the profiling control device of the present invention, Fig. 6 is a diagram showing the principle of profiling operation of the present invention in a portion where the radius of curvature becomes small, and Figs. FIG. 9 is a diagram illustrating the operation of controlling the inclination in the direction intersecting the profiling plane, and is a diagram illustrating the profiling operation of the present invention in a portion with a large radius of curvature. W...object, P...position of hand, 1...robot,
2... Hydraulic cylinder, 3... First column, 4... First moving body, 5... Second column, 6... Hydraulic cylinder, 7...
Second moving body, 8... Hydraulic cylinder, 9... Third moving body, 10... Wrist block, 11... Bending shaft, 12, 13... Sensor, 14... Sensor mounting plate,
15...Calculator, 16...Interface, 17~
21... Positioning device, 22... Sensor interface, 121, 131... Sensor main axis line, 12
2,132...Sense amplifier, 171...Subtraction circuit,
172... Servo circuit, 173... Robot body X-axis mechanism, 174... Position detector, 181, 182... Reference signal generation circuit, 190... Absolute value calculation circuit, 20
0, 201, 202... Comparison circuit.

Claims (1)

[Claims] 1. A sensor attached to the tip of a moving body that detects the relative distance to the object surface is moved in a specified direction along a tangent to the object surface within a specified plane by a set moving distance, and the sensor The position of the object surface is determined based on the relative distance to the object surface and the position of the moving body in the three-dimensional space, and the position of the object surface is determined from the position of the object surface corresponding to both ends of the moving distance along the tangent. Tracing control that recalculates the tangent in the specified plane, sets the next operation target point at a point separated by the set movement distance on the extension of the tangent in the specified direction, and moves the sensor toward the operation target point. In the method, the relative distance between the sensor and the object surface is constantly monitored, and each time the operation target point that is separated by the set movement distance is reached or the relative distance between the sensor and the object surface exceeds a predetermined value. A tracing control method characterized by recalculating the tangent line and setting a new target point of operation. 2. In the tracing control method as set forth in claim 1, a plurality of the sensors are provided in a plane that intersects with the designated plane, and based on the outputs of the sensors, the curve of the surface of a three-dimensional object in the intersecting plane is determined. A tracing control method comprising calculating a line direction and regulating the direction of the sensor so that it is within a certain angle with respect to the normal to the surface of the three-dimensional object. 3. The tracing control method according to claim 1, characterized in that the attitude of the sensor is regulated to be at a constant angle with respect to the tangent in the specified plane. 4. A sensor attached to the tip of a moving object to detect the relative distance to the object surface, and controlling the moving object to move the sensor along a tangent to the object surface within a specified plane toward an operation target point. a control means for determining the position of the object surface corresponding to the position based on the relative distance between the sensor and the object surface and the position of the moving object in the three-dimensional space, and determining the position of the object surface corresponding to the position, corresponding to both ends of the movement distance along the tangent line; Find the tangent to the object surface within the specified plane from the position of the object surface to be moved, set a point on the extension of the tangent in the specified direction and separated by a set travel distance as the next operation target point, and output it to the control means. a first calculating means that calculates the amount of time each time the tip of the movable body reaches an operation target point separated by the set travel distance or the relative distance between the sensor and the object surface exceeds a predetermined value during the movement; A profiling control device comprising: second calculation means for outputting a command to the first calculation means to recalculate the position of the object surface and the tangent to the object surface and to newly set an operation target point.