JPH06102310B2 - Robot motion control method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention uses an indirect interpolation method when an obstacle exists in the operation area or the operation area interferes with the operation areas of other robots. The present invention relates to a robot operation control method in which an avoidance path is set in the middle of an operation path and the avoidance path can be operated by a linear interpolation method.

[Conventional technology]

In the motion control of the robot so far, the whole motion path as a motion unit is set by one command, and when the motion route is set by one command, the route is calculated by only one trajectory interpolation method. Has become.

More specifically, when the robot is moved from one point to another point, the total path movement amount of each axis joint is calculated, and the movement amount is equally distributed to each axis to control the robot movement. If the control method is adopted, the robot can be operated at the highest speed within the range of the allowable control value that the servo motor can follow. That is, in the path from the start point to the end point of the movement, the movement amount (joint angular velocity) of each axis is accelerated at a constant acceleration and then moved at a constant velocity (allowable maximum velocity), and then decelerated at a constant acceleration. It has been done to reach the end point. The trajectory interpolation method for calculating the motion path in this manner is called a joint interpolation method, but various trajectory interpolation methods are arbitrarily selected and designated by a motion command in a general robot language.

Note that, as the publicly known documents concerning the robot language so far, for example, I.E. E-Computer Volume 14 Number 12 (1982.12) (IEEE COMPUTER V
OL.14 NO.12 (1982.12) paper “Composite Study of Robot Langages”
(A Comparative Study of Robot Languages).

[Problems to be solved by the invention]

However, with the joint interpolation method, it is difficult for the robot user to accurately predict how the robot's movement path will be. Therefore, for example, there are obstacles or the movement paths of multiple robots interfere with each other. In such a case, in the past, it was necessary to set the intermediate points in detail and subdivide the operation, or to specify a linear interpolation method that calculates a straight-line path that is easy to predict and to take an avoidance path. There is something. In such a case, the request for speeding up the operation must be sacrificed to some extent.

The purpose of the present invention is to have obstacles in its operating area,
Alternatively, when the operation area interferes with that of another robot, a robot operation control method capable of high-speed operation while setting an avoidance path is provided.

[Means for solving problems]

The above-mentioned purpose is that areas where obstacles exist or areas where interference with other robots is known in advance, so in order to avoid bypassing those areas, an avoidance path was set in the middle of the operation path by the joint interpolation method. This is achieved by operating the avoidance path by a linear interpolation method.

[Action]

For example, if the hand parts of the two robots are moved to substantially the same position by the joint interpolation method, the hand parts may come into contact immediately before the positions. Therefore, if the joint interpolation method is changed to the linear interpolation method midway, the contact can be easily avoided. When the trajectory interpolation is performed while adopting the joint interpolation method with a large ratio of the whole motion path, it is possible to speed up the motion.

〔Example〕

 Hereinafter, the present invention will be described with reference to FIGS.

First, for the purpose of clarifying the purpose of the present invention, a case where two robots simultaneously assemble parts in parallel will be described. FIG. 2 schematically shows the plane of the assembly site in that case. Each time the semi-finished product 2 is conveyed to a predetermined position by the belt conveyor 1 as shown in the drawing, the two robots 3 and 4 grip the parts (the ones in the magazine 5 are not shown) 7 from the magazines 5 and 6, respectively. The parts 7 are assembled at predetermined positions in the semi-finished product 2. Specifically, the parts 7 are assembled in the horizontal direction up to the assembling position after the parts 7 aligned in the magasins 5 and 6 are lifted upward while being held by the robots 3 and 4. It is transported and then lowered to assemble. In this case, the parts 7 in the magazines 5 and 6 are arranged so that the robots 3 and 4 can perform the assembling operation at a higher speed. The robots 3 and 4 are of the horizontal articulated type (scalar) and have the same configuration.
The hand 34 is supported by the robots 3 and 4 via the hand offset 37, the third shaft 33, the second arm 36, the second shaft 32, the first arm 35, and the first shaft 31 so as to be able to change the position within the space. It has become so. The mutual arrangement relationship between the magazines 5 and 6 and the robots 3 and 4 is designed to reduce the tact time.

Now, if the path for gripping the component 7 and conveying it to the assembly position 9 on the semi-finished product 2 is calculated by the joint interpolation method,
The route becomes like the one-dot chain line display. The * mark indicates the position where the component 7 is gripped, but if such a route is taken, the hands of the robots 3 and 4 may possibly come into contact with each other along the route reaching the mounting position 9 depending on the case. It is a thing. In order to avoid this contact, a straight detour route should be taken before the mounting position 9.

As shown in FIG. 1, the interpolation method is switched at a point P3 which is in the middle of the operation path from the component gripping point P1 to the assembly position P2, and the point P3
From the assembly position P2 to the assembly position P2, the parts are conveyed by a linear interpolation route without being temporarily stopped at the point P3.

When the parts are conveyed in this way, it is possible to avoid the contact of the hand while utilizing the joint interpolation method that allows high-speed operation. Since the position of the point P3 differs depending on the gripping position of the component, it is generally difficult to support that position from the outside according to the gripping position. It has been decided. When setting the boundary line (generally a three-dimensional boundary) with the obstacle area or other robot operation area from the outside with a margin, it is necessary to judge whether the operation path exceeds the boundary line in interpolation calculation. Thus, the point P3 can be obtained.

Here, an example of a robot language operation command for performing such an operation is as follows.

In this example, two operation instructions are shown, but the points included in the instructions
P1 is the position where the part is grasped and lifted right above,
P2 represents just above the assembly position of the parts. The first MOVE command represents an operation of lifting the part from the gripped position to a point P1 right above, and the first parameter I specifies that the part is moved by the linear interpolation method. Further, in the second MOVE command, the first parameter C sets the complex interpolation method, the second parameter P2 sets the end point of the operation, and the third parameter P4 sets the boundary line for designating the interpolation method switching point. It has become a thing. This boundary line represents a straight line passing through the points P2 and P4. That is, this MOVE command defines the operation from point P1 to point P2, and the operation path is calculated by interpolating from point P1 assuming that the entire path is calculated by the joint interpolation method. Is to switch the interpolation method when the boundary line specified by the parameter (P2, P4) of the instruction is exceeded, and the subsequent paths are calculated by the linear interpolation method.

The hardware configuration for realizing the above functions will be described. FIG. 3 shows a schematic configuration of the robot controller. According to this, the robot language command is input to the robot controller 300 before the operation panel 301, converted into the storage format by the CPU 302, and then stored in the memory 30.
It will be remembered in 3. By the way, when the operation is performed, the CPU 302 sequentially reads the language commands stored in the memory 303 by inputting the start command from the operation panel 301, interprets the read commands, preprocesses, and commands. Instructions that undergo execution branching or the like but require post-processing are sequentially stored in the common memory 304 together with necessary data. CPU 305 is common memory 304
When the instructions are stored in, the instructions are sequentially read and post-processing is executed. For example, the above-mentioned MOVE instruction is interpreted by the CPU 302, but the position information of the point indicated by the parameter is read from the memory 303 and the common memory 3
It is stored in 04 together with the instruction. In some cases, this position information is calculated by calculation based on teaching data. The CPU 305 reads the MOVE command and position information from the common memory 304 and executes the actual operation. As the processing, the trajectory interpolation processing task calculates the operation path and the specified sampling time (for example, 40
(msec) The position of the target point on the path is obtained, the angle value of each joint and the motor encoder value for positioning the robot at this position are calculated, and then stored in the common memory 304. There is. The servo processing task reads this target point data one by one at a specified sampling time, sets a control value for moving the robot to this target position, and drives the servo motor 309 via the servo amplifier 307 and the power amplifier 308. It will be. CPU
302, 305 may be configured as a single one. Also,
Reference numerals 306, 310 and 311 in the figure respectively denote a counter for feedback control, a tacho generator and a pulse encoder.

Now, the CPU 305 performs a complex interpolation process as the trajectory interpolation process, and FIG. 4 shows a schematic flow of the process.

According to this, in process 401, MOVE operation start point (previous operation end point)
And the distance between the end points given by the parameters is found along the route. That is, the movement amount when joint interpolation is performed on all the routes is calculated. In this case, the operating angle of each joint axis is also calculated. The maximum movement amount in joint interpolation represents the maximum movement angle by comparing the movement angles of the joint axes. By this post-processing 402, the equation of the boundary straight line connecting the end point of the second parameter and the intermediate point of the third parameter is obtained, and this straight line represents the straight line on the XY plane of the robot coordinate system. Therefore, a plane is formed in the Z direction (vertical direction) (vertical boundary surface). Further, in the process 403, the specified sampling time (for example, 4
After the velocity target value of the robot (representative position of the hand) is calculated for each 0 msec), the joint coordinate value of the next target point on the route is calculated by the process 404. In process 405, the joint coordinate value (angle value) of the target point is converted into the encoder value of the servo motor and the coordinate value of the orthogonal coordinate system. In process 406, it is determined whether or not the Cartesian coordinate value of the target point exceeds the boundary line. If not, the target point data (encoder value of each joint (axis) at the target point) is stored in the memory. After being stored, the processes 403 to 406 are performed. Further, if it exceeds the boundary line, the previous target point is set as the interpolation switching point by the process 408, and the linear distance between the target point and the end point is the maximum movement amount (the maximum movement amount in the linear interpolation is the orthogonal coordinate. The linear interpolation is carried out as a linear distance in the system. Calculation of the velocity target value on the linear operation in process 409, calculation of the orthogonal coordinate system coordinate value of the next target point in process 410, joint system coordinate value of the orthogonal system coordinate value of the target point in process 411, servo motor encoder Convert to value, process
After the target point data is sequentially stored in the memory at 412, the end of the linear interpolation process is determined by the process 413. If it is determined that the processing has ended, the series of processing ends, but if it has not ended, processing 409 to 413
Is to be carried out again.

〔The invention's effect〕

As described above, according to the present invention, when there is an obstacle in the operation area or when the operation area interferes with that of another robot, the robot can operate at high speed while setting the avoidance path during operation. There is an effect that can be operated.

[Brief description of drawings]

FIG. 1 is a diagram for explaining the principle of robot operation control according to the present invention, and FIG. 2 is a diagram schematically showing a plane of a part assembly site by two robots to which the present invention is applicable. 3, FIG. 3 is a diagram showing an outline of a hardware configuration of a robot control device according to the present invention, and FIG. 4 is a diagram showing a flow of a complex interpolation process according to the present invention. P1 ... Parts gripping point, P2 ... Parts assembly point, P3 ... Interpolation method switching point, P4 ... Boundary setting point, 2 ... Semi-finished product, 5 ... Magazine (for parts array).

Front page continuation (72) Inventor Hiroro Furuichi, 292 Yoshida-cho, Totsuka-ku, Yokohama, Kanagawa Pref., Institute of Industrial Science, Hitachi, Ltd. (56) Reference JP-A-58-37701 (JP, A) JP-A-58 -10483 (JP, A) JP-A-60-138611 (JP, A) JP-A-61-199111 (JP, A) JP-A-61-147307 (JP, A)

Claims (1)

[Claims] 1. A robot operation control method in the case where an obstacle or an operation area of another robot exists in the operation path for moving a robot hand to one operation end target point (end point). A vertical boundary surface that separates the motion path for moving the hand of the robot from the obstacle or the motion area of another robot is connected to the target point for ending the motion and the point obtained by teaching the robot hand at an appropriate boundary position. It is preset as a vertical plane including the boundary line, and when the robot operates, the above-mentioned start point is set in the area where the representative position of the robot's hand on the operation path from the start point to the above operation end target point does not exceed the vertical boundary surface. The robot is controlled according to the joint interpolation method that controls each axis of the robot independently. Each time the target point is calculated as an interpolation point, it is determined whether or not the representative position of the robot hand at the interpolation point exceeds the vertical boundary surface, and if an interpolation point that exceeds the vertical boundary surface is found. , A linear interpolation method in which the robot hand does not stop on a straight line connecting the interpolation point immediately before the interpolation point and the operation end target point is switched to the linear interpolation method, and according to the linear interpolation method, A robot operation control method, characterized in that the operation of a robot hand is controlled up to the operation end target point.