JP2000042956A - Trajectory generating method and device for force control robot - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a trajectory generating method and device for a force control robot capable of corresponding to automatic generation of a tool trajectory even in the case where a programmed trajectory of a tool and surface shape of a cast are different from each other. SOLUTION: A force control robot having a force control function successively executes a linear positioning command commanding linear movement to a pre-assigned final position P1 and a circular arc moving command commanding circular arc movement from a pre-assigned circular arc start position P1 to a circular arc final position P3 via a circular arc intermediate position P2. Here, an actual final position P1' of a tool T in the linear positioning command is corrected to the circular arc start position, based on this correction amount D, the circular arc intermediate position and the circular are final position are corrected, and a circular arc trajectory of the tool T is generated from these circular arc start position P1', circular arc intermediate position P2', and circular arc final position P3'.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a tool, for example,
The present invention relates to a trajectory generation method and apparatus for a force control robot having a force control function of correcting a trajectory of a tool such that a pressing force of a tool such as a grinder against a workpiece becomes a specified pressing force. More specifically, the present invention relates to a trajectory generation method and apparatus for a force control robot for continuously connecting the speeds of these trajectories when sequentially executing a linear positioning command and an arc movement command.

[0002]

2. Description of the Related Art In grinding operations such as deburring, grinding, and polishing, a force having a force control function for automatically correcting a tool trajectory so that a pressing force of a tool such as a grinder against a workpiece becomes a specified pressing force. A control robot is used.

FIG. 5 shows a program trajectory of a tool when a surface of a workpiece is machined by a force control robot having a force control function. In the figure, T is a tool such as a grinder. The tool T is initially positioned P (X, Y,
Z), it is first positioned at position P0 (X0, Y0, Z0), and then positioned at position P1 (X1, Y1, Z1), and then positioned at position Pn (Xn, Yn, Zn). Shall be.

First, a program for positioning the tool T from the position P (X, Y, Z) to the position P0 (X0, Y0, Z0) is as follows. MOVE P0 (positioning from the position P to the position P0 at the shortest distance) Next, the program for positioning the tool T from the position P0 (X0, Y0, Z0) to the position P1 (X1, Y1, Z1) by a linear trajectory is as follows. It is as follows. At this time, if it is necessary to perform machining while pressing the tool T against the workpiece W with a pressing force (f) of 2 kg, the following is performed. GMOVES P1, FORCE2.0 (force control 2k
g, linear positioning to the position P1) Similarly, while pressing the tool T against the work W with a pressing force of 2 kg, the position P is shifted from the position P1 (X1, Y1, Z1) to the position P.
The program for positioning to n (Xn, Yn, Zn) with a linear trajectory is as follows. GMOVES Pn, FORCE2.0 (force control 2k
g, linear positioning to position Pn)

When programmed in this manner, the tool T moves on a linear trajectory (moves to the positions P, P0, P1, and Pn) while being pressed against the work W with a pressing force of 2 kg. The surface is machined. For example, if the workpiece W is a casting and the tool T is a grinder, the grinder (tool T) is moved to the positions P, P0, P1, and Pn while being pressed against the surface of the workpiece W. Deburring can be performed.

An example of a machining program that summarizes the above is as follows. SPEED = 0.3 (Speed designation 0.3m / min) FORCE = 2.0 (Force control force designation) MOVE P0 (Positioning from position P to position P0 at shortest distance) GMOVES P1 (To position P1 while controlling force) GMOVES Pn (Linear positioning to position Pn while controlling force)

FIG. 6 shows a program trajectory of the tool when the trajectory of the tool T is a circular trajectory at the corner Wc of the workpiece W (see FIG. 4). Here, P1 is the arc start position of the arc trajectory P2 is the arc intermediate position of the arc trajectory P3 is the arc end position of the arc trajectory, and the program at that time is as follows. MOVE P0 (positioning from position P to position P0 at shortest distance) GMOVES P1 (linear positioning to position P1 while controlling force) GMOVEC P2, P3 (current position P1 at arc start position, P2 at arc intermediate position, P3 at arc) GMOVES Pn (Linear positioning to position Pn while controlling force) In addition, force control in a circular arc trajectory always controls the force in the direction perpendicular to the tangent or tangent to the tool position on the circular arc. ,
It is controlled so that the force always goes to the center.

FIG. 7 is a diagram for explaining a method of generating an arc trajectory. The arc trajectory is generated by a straight vertical bisector L1 connecting the arc start position P1 and the arc intermediate position P2.
The center C is the intersection of the vertical bisector L2 of the straight line connecting the arc intermediate position P2 and the arc end position P3, and the arc start position P1 (or the arc intermediate position P2 or the arc end position P3) from the center C. It is defined as a circle whose radius is the distance to. That is, a part of this circle is designated as a program as an arc trajectory. In addition, as a robot control program command, a command TA for designating work content is used.
SK, a command TCODE for designating the type of tool, the point of action of the tool during machining, that is,
There is a command TCP or the like for designating a part to be ground.
According to these program instructions, the pressing direction of the force control is determined by a control device using a microcomputer.

An example of a program in which the trajectory of the tool T is an arc trajectory at the corner of the workpiece W is as follows. TASK = GRIND (operation specifies grinding) TCODE = GRINDER (tool specifies grinder tool) TCP = TIP (tool action point is the tip of the tool) SPEED = 0.3 FORCE = 2.0 MOVE P0 (from position P) GMOVES P1 (Arc start position P1) GMOVEC P2, P3 (P2 is an arc middle position, P3 is an arc end position and P3 is an arc end position) GMOVES P4 (Line to position Pn with force control) Positioning)

[0010]

Conventionally, when such a program is used to position the tool T from the position P0 to the position P1 while force-controlling the work W, for example, as shown in FIG. In some cases, the actual final position of the tool T becomes P1 'due to automatic correction of the trajectory by force control. Therefore, the next arc trajectory is
The position P1 'is programmed as an arc start position, the arc intermediate position P2 is set as a via point, and the position P3 is programmed as an arc end position. As a result, the generated tool trajectory is as shown in FIG. That is, the actual tool trajectory following the straight trajectory, the arc trajectory, and the straight trajectory may be different from the shape specified by the program.

If the program trajectory of the tool T specified by the program does not match the surface shape of the work W, the program trajectory is automatically adjusted so that the pressing force of the tool T against the work W becomes the specified pressing force. This is a phenomenon that often occurs when the work W is a casting. Therefore, when the casting shape is different from the program trajectory of the tool, it is necessary to automatically correct and generate the tool trajectory, which has been a conventional problem.

An object of the present invention is to solve such a conventional problem and to automatically correct a tool trajectory even when a program trajectory of a tool programmed in advance and a surface shape of a workpiece such as a casting are different. An object of the present invention is to provide a method and an apparatus for generating a trajectory of a force control robot capable of performing generation.

[0013]

SUMMARY OF THE INVENTION A continuous trajectory generation method for a force control robot according to the present invention is a force control robot having a force control function for correcting the trajectory of a tool so that the pressing force of the tool against a workpiece becomes a specified pressing force. Is a linear positioning command that instructs the tool to move on a linear trajectory to a pre-specified final position while pressing the tool against the work with the specified pressing force, and is specified in advance while pressing the tool against the work with the specified pressing force. In order to sequentially execute the circular movement command for instructing to move on the circular orbit from the circular arc starting position to the circular final position via the circular intermediate position, the actual final position of the tool in the linear positioning command is determined by the circular moving command. In addition to correcting the arc start position, the arc intermediate position in the arc movement command based on the correction amount And correcting the arc end positions, these corrected arc start position, generates a circular arc track of the tool from the arc intermediate position and the arc end positions, it is characterized.

According to such a configuration, for example, when the trajectory of the tool specified in the linear positioning command does not match the surface shape of the work, the pressing force of the tool against the work is set to the specified pressing force. The trajectory is automatically corrected, but the actual final position of the tool is corrected to the arc start position in the circular movement command, and the intermediate position of the circular arc and the final arc position in the circular movement command are corrected based on the correction amount. Since the arc trajectory of the tool is generated from the corrected arc start position, arc intermediate position, and arc end position, it is possible to generate a trajectory having substantially the same shape as the trajectory specified in advance in the arc movement command. Therefore, when sequentially executing the linear positioning command and the circular movement command, the speeds of these trajectories can be continuously connected, and the processing is performed while moving the tool under the specified pressing force according to the surface shape of the workpiece. Therefore, high-precision processing can be expected.

In the above, when generating the arc trajectory, a perpendicular bisector of a straight line connecting the arc start position and the arc middle position and a vertical bisector of a straight line connecting the arc middle position and the arc end position are used. It is desirable that a part of a circle centered on the intersection with the line and whose radius is the distance from the center to the arc start position be generated as an arc trajectory.

Further, in the continuous trajectory generating apparatus for a force control robot according to the present invention, the force control robot having a force control function for correcting the tool trajectory so that the pressing force of the tool against the workpiece becomes the specified pressing force, comprises: A linear positioning command for instructing the robot to move on a linear trajectory to a pre-specified final position while pressing the workpiece with a specified pressing force,
When sequentially executing an arc movement command for instructing a tool to move on a circular orbit from a predetermined arc start position to a final arc position via a circular arc intermediate position while pressing a tool against a workpiece with a specified pressing force, A trajectory generation device that automatically generates a trajectory of a tool, comprising: means for correcting an actual final position of the tool in the linear positioning command to an arc start position in the circular movement command; and Means for correcting an arc intermediate position and an arc end position in a movement command, and means for generating an arc trajectory of a tool from these corrected arc start position, arc intermediate position and arc end position. I do.

According to such a configuration, even if the trajectory is corrected by force control, the actual final position of the tool is corrected to the arc start position in the circular movement command, and the circular movement command based on the correction amount. Are corrected, and the arc trajectory of the tool is generated from the corrected arc start position, arc intermediate position and arc end position, so that the trajectory is substantially the same as the trajectory specified in advance in the arc movement command. Trajectories of shapes can be generated. Therefore, when sequentially executing the linear positioning command and the circular movement command, the speeds of these trajectories can be continuously connected, and the processing is performed while moving the tool under the specified pressing force according to the surface shape of the workpiece. Therefore, high-precision processing can be expected.

In the above, the means for generating the arc trajectory includes a vertical bisector of a straight line connecting the arc start position and the arc middle position, and a vertical bisector of a straight line connecting the arc middle position and the arc end position. It is desirable that a part of a circle centered on the intersection with the line and whose radius is the distance from the center to the arc start position be generated as an arc trajectory.

[0019]

Embodiments of the present invention will be described below with reference to the drawings. In the following description, the same components as those in FIGS. 5 to 8 described above are denoted by the same reference numerals, and description thereof will be omitted or simplified.

(Trajectory Generation Method) FIG. 1 shows an example of a trajectory generation method according to the present invention. Here, for convenience,
The description will be made on the XY plane. This is a straight line that instructs the force control robot having the force control function to move along the linear trajectory to the previously specified final position P1 while pressing the tool T against the work W with the specified pressing force, as in FIG. A positioning command, an arc movement command for instructing the tool T to move on a circular orbit from a predetermined arc start position P1 to a circular end position P3 via a circular arc intermediate position P2 while pressing the tool T against a workpiece W with a specified pressing force. And a linear positioning command for sequentially instructing the tool T to move on a linear trajectory to a predetermined final position Pn while pressing the tool T against the workpiece W with a specified pressing force.

At this time, the tool T specified by the program
If the program trajectory does not match the surface shape of the workpiece W, the program trajectory is automatically corrected so that the pressing force of the tool T against the workpiece W becomes the specified pressing force. The actual final position of T is P1 '. Here, the actual final position P1 'of the tool T in the linear positioning command is corrected to the arc start position in the circular movement command. That is, the arc start position P1 specified in the arc movement command is corrected to P1 '. Next, based on the correction amount (difference between P1 and P1 ': force correction amount D), the arc intermediate position P2 and the arc final position P3 in the arc movement command are corrected. That is, the correction amount (force correction amount D) is added to the force correction direction of the previous block with respect to the arc intermediate position P2 and the arc end position P3 in the arc movement command, and the arc start position and the arc end position are P2 ′, Correct to P3 '. Finally, an arc trajectory of the tool T is generated from the corrected arc start position P1 ', arc intermediate position P2', and arc end position P3 '. This can be performed by the method described with reference to FIG.

As a result, it is possible to generate a trajectory having the same shape as the arc defined by the program at the beginning. Therefore, in order to sequentially execute the linear positioning command, the circular movement command, and the linear positioning command, the speeds of these orbits can be continuously connected, and the workpiece W
Since the machining can be performed while moving the tool T under the specified pressing force according to the surface shape of the above, high-precision machining can be expected.

(Trajectory Generation Apparatus) FIG. 2 shows an example of a trajectory generation apparatus according to the present invention. In the figure, a tool (a grinder or the like) T of the force control robot is driven to rotate by a drive motor 11 and is positioned at an arbitrary position by a servomotor 12 for each axis control axis. The position of the tool T is determined by a position detector 13 added to the servomotor 12.
And the like, and input to the control device 20. Further, a force sensor 14 is attached to the tool T, whereby a force (normally, a force in six axial directions) and a moment of the tool T are detected and input to the control device 20. In addition, as the force sensor 14, a strain gauge, a semiconductor pressure-sensitive sensor, or the like can be used.

The control device 20 includes an arithmetic control unit (CP)
U) 21, interface 22, control memory 23, temporary storage memory 24, and bus 2 for connecting these
5 and the like. The interface 22 is connected with the drive motor 11, the servomotor 12 for each axis control axis, the position detector 13, and the like, and also with the keyboard 15 and the program input means 17 such as the network 16. In the control memory 23,
The machining program input from the program input means 17 is stored. As shown in FIG. 3, the temporary storage memory 24 stores the positions P0, P
Areas E0 to E for storing position coordinates of 1, P2 and P3
3. An area EA for storing the position coordinates of the current position Pa of the tool T given by the position detector 13, and an area for storing force control direction parameters (0: no force control, 1: X + direction, 2: X- direction). EB and the like are provided.

The arithmetic control unit 21 performs the following processing when performing the tool movement shown in FIG. First, the position coordinates of the positions P0, P1, P2, and P3 specified by the program are stored in the areas E0 to E3 of the temporary storage memory 24, and a linear positioning command (from position P0 to position A linear position determination to the position P1), an arc movement command (the position P3 from the position P1 via the position P2)
Circular movement), linear positioning command (from position P3 to position P)
n). During this time, the coordinates of the current position Pa of the tool T given from the position detector 13 are updated and stored in the area EA of the temporary storage memory 24.

After the linear positioning (determining the linear position from the position P0 to the position P1), the coordinates (XPa, YPa, ZPa) of the current position Pa, in this case, the actual position of the tool T in the linear positioning command. The coordinates (X1 ', Y1', Z1 ') of the final position P1' are set as the arc start position, and the final position P1 'and the arc start position P in the arc movement command are set.
The difference from 1 (force correction amount D) is obtained. Next, according to the force control direction parameter of the temporary storage memory 24, the force correction amount D is used as the coordinates (X2, Y2, Z2) and (X2) of the arc intermediate position P2 and the arc final position P3 in the arc movement command.
3, Y3, Z3), and the arc intermediate position and the arc final position are defined as P2 ′, P3 ′,
An arc trajectory of the tool T is generated from the corrected arc start position P1 ', arc intermediate position P2', and arc end position P3 '. This generation can be performed by the method described with reference to FIG.

Further, the next trajectory moves from the position P3 'to the position P
In order to continue to n, a position from a new arc final position P3 'is generated with reference to the data in the program designated area. Then, using the newly generated orbit data,
The servo motor 12 is driven via the interface 22. Further, position feedback data is detected from the position detector 13, and a new trajectory is controlled while rotating the tool T.

In the above-described embodiment, the tool T is moved along a shape having a so-called protruding corner where two intersecting surfaces of the work W are located outside.
As shown in FIG. 4, the present invention can be similarly applied to a case where the tool T is moved along a shape having a so-called corner where two intersecting surfaces of the workpiece W are located inside.

[0029]

According to the method and apparatus for generating a trajectory of a force control robot according to the present invention, since the above-described configuration is employed, even when the program trajectory of a tool programmed in advance and the surface shape of a workpiece such as a casting are different. Automatic correction and generation of tool trajectories are possible.

[Brief description of the drawings]

FIG. 1 is a diagram for explaining a trajectory of a tool in an embodiment of a trajectory generation method of the present invention.

FIG. 2 is a block diagram illustrating a trajectory generation device according to the present invention.

FIG. 3 is a diagram showing contents of a temporary storage memory shown in FIG. 2;

FIG. 4 is a diagram showing an example in which the trajectory generation method of the present invention is applied to different works.

FIG. 5 is a view for explaining a trajectory of a conventional tool.

FIG. 6 is a view showing a tool trajectory when a tool trajectory is designated as a circular arc in a corner portion of a work in FIG. 5;

FIG. 7 is a diagram for explaining a method of generating an arc trajectory of a tool.

FIG. 8 is a diagram for explaining a state in which a trajectory of a tool is corrected by force control.

[Explanation of symbols]

 T tool W work

Claims (4)

[Claims] 1. A force control robot having a force control function for correcting a tool trajectory so that a pressing force of a tool against a work becomes a specified pressing force, wherein the force control robot is configured to press a tool against a work with a specified pressing force beforehand. And a linear positioning command that instructs the tool to move to the final position along a linear trajectory, and an arc from a pre-specified arc start position to an arc end position via an arc intermediate position while pressing the tool against the workpiece with the specified pressing force When sequentially executing an arc movement command for instructing movement on a track, the actual final position of the tool in the linear positioning command is corrected to an arc start position in the arc movement command, and the arc movement is performed based on the correction amount. The middle position of the circular arc and the final position of the circular arc in the command are corrected, and the corrected circular start position , To produce a circular arc track of the tool from the arc intermediate position and the arc end positions, trajectory generation method of force control robot, characterized in that. 2. The trajectory generation method for a force control robot according to claim 1, wherein in generating the arc trajectory, a vertical bisector of a straight line connecting the arc start position and the arc intermediate position, and the arc Generating a part of a circle centered on the intersection of the straight line connecting the intermediate position and the end position of the arc with the perpendicular bisector, and having a radius equal to the distance from the center to the start position of the arc as an arc trajectory; Trajectory generation method for a force control robot. 3. A force control robot having a force control function for correcting a trajectory of a tool so that a pressing force of the tool against a work becomes a specified pressing force, wherein the force control robot is configured to press a tool against a work with a specified pressing force beforehand. And a linear positioning command that instructs the tool to move to the final position along a linear trajectory, and an arc from a pre-specified arc start position to an arc end position via an arc intermediate position while pressing the tool against the workpiece with the specified pressing force A trajectory generating device that automatically generates a trajectory of a tool when sequentially executing an arc movement command for commanding to move on a trajectory, wherein the actual final position of the tool in the linear positioning command is determined by an arc in the arc movement command. Means for correcting to a start position, an arc intermediate position and an arc in the arc movement command based on the correction amount. A trajectory generator for a force control robot, comprising: means for correcting a final position; and means for generating an arc trajectory of a tool from the corrected arc start position, arc intermediate position, and arc end position. . 4. The trajectory generation device for a force control robot according to claim 3, wherein the means for generating the circular trajectory includes a vertical bisector of a straight line connecting the circular arc start position and the circular arc intermediate position, and the circular arc. Generating a part of a circle centered on the intersection of the straight line connecting the intermediate position and the end position of the arc with the perpendicular bisector, and having a radius equal to the distance from the center to the start position of the arc as an arc trajectory; Trajectory generator for force control robot.