JPS6231406A - Positioning controller for articulated robot - Google Patents

Abstract

PURPOSE:To cope automatically with the change of the inertia of moment caused by the change of the weight of a work and the change of the posture of a robot, by performing in real time the estimation of the work weight, the correction of the moment of inertia and the calculation of the starting point of deceleration and a speed command when a shift of the robot is started. CONSTITUTION:The 1st arithmetic means 4 of a controller calculates the moment of inertia for axis conversion of each motor when a work 2 is not held. While the 2nd arithmetic means 7 calculates the weight of the work 2. At the same time, the acceleration of a motor 3 which drives each joint of a multi-joint robot 1 is detected by an acceleration detecting means 5. Then the torque of the motor 3 is detected by a torque detecting means 6. In addition, the 3rd arithmetic means 8 corrects each moment of inertia of a target shift point based on the moment of inertia of the target shift point of the means 4 and the work weight given from the means 7. The 4th arithmetic means 8 calculates the moment of inertia corrected by the means 8 and the torque detected by the means 6. Then the optimum deceleration is added to the 5th arithmetic means 12. The motor 3 is controlled with the outputs of a speed detecting means 10, a remaining shift amount detecting means 11 and the means 12.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a positioning control device for an industrial robot having a multi-joint mechanism.

BACKGROUND OF THE INVENTION In recent years, industrial robots have become popular as a means of automating production, and higher speed and higher precision are desired.

Generally, when controlling the positioning of an articulated robot, when the maximum torque generated by the motor that drives the robot is set to T and the maximum speed is set to 1, the following method is used to move the robot to the target point in the shortest time. be. The motor speed is linearly ramped up to 1 at Tm, and after the speed reaches ω, ω. -T when approaching the target point. Apply torque in the opposite direction to raise the speed linearly to zero, so that the target point is reached exactly when the speed reaches zero.

FIG. 2a shows the time-speed characteristic, b shows the time-torque characteristic, and C shows the time-travel characteristic in the above case.

Here, the slopes of the rise and fall of the speed in Figure 2 a indicate acceleration and deceleration, which are approximated by dividing the torque generated by the motor by the moment of inertia converted to the motor shaft. Acceleration/deceleration will change in inverse proportion. When considering the control of an actual articulated robot, the moment of inertia changes due to changes in the weight of the gripped workpiece and changes in the robot's posture. In the past, a number of speed commands were prepared, and the operator selected one from among them according to the task.

Problems to be Solved by the Invention However, with the above configuration, if the speed command is set assuming the maximum moment of inertia, movement in an area with a small moment of inertia will not be the shortest time. However, there are problems in that it requires specialized knowledge and selection time for the operator to select the optimum speed command for the work from among several speed commands.

In view of the above problems, the present invention provides a positioning control device for an articulated robot that automatically adapts to changes in the moment of inertia and sets an optimal speed command and deceleration start point.

Means for Solving the Problems In order to solve the above problems, the positioning control device for an articulated robot of the present invention includes means for calculating the weight of a workpiece;
The apparatus includes means for correcting the moment of inertia of each joint at the movement target point, and means for calculating the deceleration start point and speed command curve of the motor that drives each joint.

Operation The present invention has the above-described configuration to estimate the weight of the workpiece at the start of movement, correct the moment of inertia near the movement target point,
Since the calculation of the deceleration start point and speed command is performed in real time, it automatically adapts to changes in the moment of inertia due to changes in workpiece weight and robot posture, and sets the optimal speed command and deceleration start point. becomes.

Embodiment Hereinafter, a positioning control device for an articulated robot according to an embodiment of the present invention will be described with reference to the drawings.

FIG. 1 shows an overall block diagram of an articulated robot according to an embodiment of the present invention. In FIG. 1, 4 is a first calculating means for calculating the moment of inertia converted to each motor axis when no workpiece is gripped, 7 is a second calculating means for calculating the weight of the workpiece, and 8 is a moving target point. A third calculating means corrects each moment of inertia, a fourth calculating means 9 calculates the optimum deceleration of the motor, and a fifth calculating means 12 calculates a speed command.

Here, we will explain the operation of a robot with a two-axis configuration as shown in FIG. 3, paying particular attention to its one-axis motor. The moment of inertia calculated by the first calculation means 4 when converting to the motor shaft when no workpiece is gripped at the movement start point is JA, and the distance between the workpiece gripping part and the motor axis at the movement start point is rA% Load weight Let be ML.

First, the motor drive means 13 linearly ramps up the motor speed at the maximum torque generated by the motor 3.

At this time, acceleration detection means 5. When the acceleration and torque obtained from the torque detection means 6 are respectively αA+''m, the following relational expression holds true.

αA=T-/(JA+MLXrA) """
(1) Based on the above formula, the moment of inertia converted to the motor shaft when the workpiece weight is not gripped at the movement target point calculated by the first calculation means 4 is determined by the second calculation means 7. When JB is JB and the distance between the work gripping part and the motor axis at the movement target point is rB, the corrected moment of inertia Jc calculated by the third calculation means 8 is T c = I B + ML X r B2... ...
(3) becomes.

Next, the optimum deceleration calculated by the fourth calculation means 9 is the maximum deceleration αB obtained by dividing IC by the maximum generated torque Tm, as shown in the following formula.

αB=Tm/Jc=Tm/(JB+MLxrB2),
,,,,I) Since the above deceleration αB is the maximum deceleration that can be achieved near the moving target point, deceleration at αB will complete the deceleration in the shortest possible time.

The maximum speed of the motor is ω, and the remaining travel amount calculation means 11
Assuming that the remaining movement amount obtained from the above is θ, the speed command ωC for decelerating at the deceleration αB and making the speed also zero when the remaining movement amount θ is zero is as follows. Here ωC=ω. The value of θ, that is, the deceleration starting point θC, is derived, and the speed command and deceleration starting point of equations (5) + (6) are calculated by the fifth calculation means 12. FIG. 4 shows the relationship between θ and speed command ωC.

The motor drive means 13 controls the drive of the motor so that the polarization between the speed command calculated by the fifth calculation means 12 and the actual motor speed detected by the speed detection means 10 becomes zero. Performs robot positioning control.

FIG. 5 shows (a) time-speed characteristics, (b) time-torque characteristics, and (C) time-travel characteristics in this example.

Effects of the Invention As described above, the present invention includes a first calculating means for calculating the moment of inertia converted to each motor axis when no workpiece is gripped, a second calculating means for calculating the weight of the workpiece, and a moving target point. By providing a third calculation means for correcting each moment of inertia in , a fourth calculation means for calculating the optimum deceleration, and a fifth calculation means for calculating the speed command and deceleration start point, The optimum deceleration command and deceleration start point are automatically adjusted to the changes, and positioning control can be performed.

[Brief explanation of drawings]

FIG. 1 is an overall block diagram of a positioning control device for an articulated robot according to an embodiment of the present invention, and FIGS. 2(a) to (C)
) is a diagram showing the time-velocity characteristic 2 hours-torque characteristic and time-travel characteristic during the shortest time positioning control, FIG. 3 is a configuration diagram of the articulated robot in this embodiment, and FIG. 4 is the diagram in this embodiment Remaining travel amount vs. speed command characteristic diagram in Figure 5 (
a) to (C) are diagrams showing time-speed characteristics, time-torque characteristics, and time-travel characteristics in this example. DESCRIPTION OF SYMBOLS 1...Multi-joint robot, 2...Workpiece, 3...Motor, 4...First calculation means, 5...Acceleration Detection means, 6...Torque detection means, 7...Second calculation means, 8...
...Third calculating means, 9... Fourth calculating means, 10... Speed detection means, 11...
Remaining movement amount detection means, 12...fifth calculation means, 13...motor drive means. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
Figure' --- Data 74 * n &'-i>2-m- Work Figure 2 Figure 3 Figure 4 r Figure 5

Claims (1)

[Claims] In a positioning control device that drives and controls the motors that drive each joint of a robot with a multi-joint mechanism according to a speed command given to it, a first device calculates the moment of inertia converted to each motor axis when a workpiece is not gripped. calculation means;
an acceleration detection means for detecting the acceleration of a motor that drives each joint; a torque detection means for detecting the torque of a motor that drives each joint; and a moment of inertia at a movement start point obtained from the first calculation means; , second calculation means for calculating the weight of the workpiece from the acceleration obtained from the acceleration detection means and the torque obtained from the torque detection means when the workpiece is gripped and started to move; and a moving target obtained from the first calculation means. third calculation means for correcting each moment of inertia at the moving target point from the moment of inertia at the point and the workpiece weight obtained from the second calculation means; and the torque obtained from the torque detection means and the third calculation means. a fourth calculation means for calculating an optimal deceleration of the motor driving each joint from the obtained corrected moment of inertia; a speed detection means for detecting the speed of the motor driving each joint; remaining movement amount calculation means for calculating the remaining movement amount from the current point and the movement target point of the motor driving the motor; the speed obtained from the speed detection means, the deceleration obtained from the fourth calculation means, and the remaining movement amount. A positioning control device for an articulated robot, comprising a fifth calculation means for calculating a speed command and a deceleration start point from the remaining movement amount of the motor obtained by the calculation means.