JPS59219185A - Controller for industrial robot - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to a control device for an industrial robot, and more specifically, to improve control accuracy in a control device for an industrial robot that does not have a measuring device at the tip of a robot arm. This relates to improvements to improve

[Background of the invention]

In conventional industrial robot control devices, a measuring device is installed at the tip of the robot arm, and there is generally no means for feeding back the output information of this measuring device to improve the control accuracy of the robot arm. . The reason for this is that the movable range of the robot arm is a large three-dimensional area, which is difficult to measure due to the relationship with the workpiece.

FIG. 1 is a block diagram showing an example of the conventional industrial robot control device described above, and includes a movement command generation unit 1 for outputting movement commands for moving the robot, and a movement command generation unit 1 for outputting movement commands for moving the robot, and for moving the robot in response to movement commands. Motor 2 that generates power of
The robot body 4 is comprised of a drive unit 6 that receives the power generated by the motor 2 and drives the robot body 4, and the robot body 4. Although not shown, the motor 2 is equipped with a pulse encoder, tachometer generator, etc. at the rotation &Ah, so that the rotational position and rotational speed of the motor 2 are fed back to the movement command generation section 1. There is. Also 1. The short drive 5 is composed of a speed reduction mechanism such as a harmonic drive.

In the conventional industrial robot control device as shown in Part 1 (1), the motor 21 is actually controlled. The movement error requirements of the robot arm tip due to vibrations and deflections of the mechanical system cannot be incorporated into the control elements, and no matter how much the control accuracy of the motor 2 is improved, there is a limit to improving the control accuracy of the robot arm tip. There was a drawback.

[Purpose of the invention]

The present invention was made in view of the above-mentioned drawbacks of the prior art, and improves a control device for an industrial robot in which a measuring device is not provided at the tip of the robot arm. The purpose of this invention is to provide an industrial robot control device that improves the control precision of the arm tip.

[Summary of the invention]

The industrial robot control device of the present invention includes a movement command generation unit that creates a movement command for the robot, a motor that is servo-controlled by the movement command, and a deceleration mechanism that transmits the power generated by the motor to the robot. In an industrial robot equipped with a drive unit, means for detecting a rotation angle of a motor and a rotation angle of a shaft of the drive unit, and a means for detecting both rotation angles and detecting a torsion angle of both rotation angles. means and
The present invention is characterized by comprising means for feedback-controlling the movement command generation section based on the detected torsion angle and outputting an optimal movement command.

FIG. 2 is a block diagram showing the main features of the feeding control device 1 for an industrial robot according to the present invention. 5, input the torsion angle signal θ corresponding to the detected torsion angle.
3, a correction control section 6 that performs feedback control on the movement command generation section 1 is provided. Here, the rotation angle signal θ1 is detected by a detector such as a pulse encoder conventionally provided on the motor 2, and the rotation angle signal θ2 is detected by a detector provided on the shaft of the drive unit 3 according to the present invention. .

In general, the load torque-shaft torsion angle characteristic of the drive unit B, which is composed of a gear mechanism such as a harmonic drive, is determined by the third
The result will be as shown in the figure. Here, as shown in the figure, the horizontal axis is the load torque seen from the drive shaft, and the vertical axis is the torsion angle. In addition, in FIG. 3, region a is a region where the load shaft does not easily rotate even if torque is applied to the drive shaft of the drive unit 6 (the torsion base is large compared to the self-defense torque), and this is a so-called lost motion. When the robot accelerates or decelerates, the speed must be increased when the motion is within area a compared to when it is within area a, otherwise the acceleration time will become unnecessarily long, which will hinder the robot's high-speed movement. Come. Although predictive control is possible with conventional industrial robot control devices, optimal control cannot be achieved because the command values are set with safety in mind due to the limited capacity of the servo system. Further, during deceleration, deceleration will not be performed smoothly unless the speed is reduced to a greater extent when the vehicle is within region a than when it is within region A. This means that if it can be determined that the vehicle is within region a, acceleration and deceleration can be performed efficiently.

If we can go a step further and know the torsion angle, for example, if the robot is mechanically vibrating near a standstill, conventional industrial robot control devices cannot detect this mechanical disturbance. However, by detecting the torsion angle, it is possible to measure not only the presence or absence of mechanical vibration, but also the amplitude and period, making it possible to create a speed command that quickly dampens vibration and stop mechanical vibration. This principle can also be applied during robot operation, so it is also effective against mechanical vibrations during operation.

The mechanical vibration analysis described above will be explained in detail. FIG. 4 shows the direction detection unit 5i of the torsion angle detection unit 5 shown in the second FQK.
', l It is composed of WR9, 10 and up/down counter 11, and [ is 1 rotation angle and drive sound 1 (
The rotation angles of the three axes are detected by pulse encoders 7.8 provided on the respective axes. Pulse encoder 7
．． The outputs of 8 are input to direction determining units 9 and 10, respectively, and the direction determining units 9 and 10 generate a pulse at the output terminal U if the rotation is on the + side, and generate a pulse at the output terminal U if the rotation is on the negative side. It is composed of The output of each direction discrimination sound 1s';+, 1o is input to an up/down counter 11.

4. Assuming that the motor 2 is rotated by two pulses of the pulse encoder 7 toward the + side, the direction determining section 9 outputs two pulses from the output terminal U, and the up/down counter 11 is incremented by two. Here, when the drive section 3 follows and rotates, the shaft of the drive section 6 also rotates to the + side by the amount of two pulses output from the pulse encoder 8, and due to this force, the direction determination section 10 outputs two pulses from the output terminal. do. As a result,
The up-down counter 11, which had been incremented by two, is decremented by two and eventually returns to its original state.

If the load torque of the drive section 6 is large, two pulses will be output from the pulse encoder 8, and as a result, the incremented amount will remain in the up/down counter 11. This remaining value corresponds to the twist angle, which is the sixth
As shown in the figure, it is proportional to the load torque.

Therefore, the output of the up/down counter 11 is proportional to the load torque, and this value is
angle and the rotation angle of the shaft of the drive unit 3 (proportional to the load torque).

). Therefore, by sampling the output of the up/down counter 11 at an appropriate sampling period, the time change in the mechanical vibration of the robot arm can be measured.
For example, it is possible to detect the group shown in Figure 5≠; by analyzing this detection result, the amplitude, period, and damping rate of the paddle machine vibration can be determined, and by these, it is possible to quickly dampen the machine vibration. According to the present invention, the negative (af) torque of the robot arm can be easily determined, and it is possible to directly use this to control the torque of the robot arm. You can do @l. Torque control fill is essential for assembly robots, etc., and by monitoring the up/down counter 11, it becomes possible for the movement command generation unit 11 to calculate a movement command that outputs a predetermined torque to the robot arm. .

[Embodiments of the invention]

FIG. 6 is a block diagram showing one embodiment of the present invention. In FIG. 6, a movement command creation unit 1 is composed of a microprocessor, etc., and creates a movement command based on robot position # information taught in advance and position feedback from the motor 2, and outputs it to a movement command latch 12. The command latch 12 is composed of an up/down counter as a preset circuit, and is configured so that its content (movement command) can be corrected by the output of the correction generator 15. The output of the movement command latch 12 is 'b
/ Converted to an analog quantity by the A converter 13,
The signal is amplified by the servo amplifier 14 and drives the motor 2. Here, the D/A converter 16 and the servo amplifier 14 may be unnecessary depending on the control method of the motor 2.

The relative displacement between the motor 2 and a pulse encoder (not shown) installed in the drive section 3 becomes a count value of an up/down counter 110, which is output to the correction control section 16.

In the correction control section 16, the movement command generation section 1
Based on information indicating the state of the movement command (robot stopped, accelerating, decelerating, etc.) output from the correction generator section 1, the necessity of correction and the amount of correction are determined.
5.

The correction generator unit 15 outputs a pulse corresponding to the correction amount to the transfer 1 command latch 12 which is constituted by an up/down counter. As a result, movement command latch 1
The contents of 2 are counted up or down as appropriate, and the movement command is appropriately corrected.

The above correction amount is determined by the correction control unit 16 so that the acceleration/deceleration time is minimized when controlling the speed of the robot optimally. In addition, when a constant torque characteristic is required for the robot arm in an assembly robot, a corresponding correction amount is determined by the correction control section 16, and if a colleague wants to dampen the vibration of the robot arm, the correction amount corresponding to this is determined by the correction control section 16. The corresponding correction amount must then be determined.

From the above explanation, it is clear that according to this embodiment,
It enables reduction of acceleration/deceleration time, torque control, and damping control of mechanical vibration of the robot arm, greatly improving the controllability of industrial robots.

[Effects of IL14] According to ``Kinoto 1jt'', even in the control device of an industrial robot with or without a measuring device at the tip of the robot arm, by using the torsion angle of a gear mechanism such as a harmonic drive. It is possible to reduce the acceleration/deceleration time, to perform agile control to eliminate mechanical vibration when the robot arm is stopped or in motion, and to perform constant torque control of the robot arm, which is essential for the silk-making robot IC. Moreover, it can be realized by simply adding jEQ quality to the conventional damping j device of industrial robots, and the cost is also low.

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing the control device of a conventional industrial robot; Fig. 2 is a block diagram showing the main points of the control device of the industrial robot of the present invention; The figure is a block diagram showing a specific example of the torsion angle detection section shown in No. 21-1, FIG. 5 is a diagram showing an example of time change of torsion angle (relative displacement) when the robot arm is vibrating, and FIG.
The figure is a block diagram showing one embodiment of the industrial robot control device of the present invention. 1...Movement command generation unit, 2...
・Motor, ro...drive area 5.411. robot body,
5...Twisted square stopper w city, 6...Supplementary JEfljlJ Gobe, 7. a...Pulse encoder, 9,1°...
・Direction determination unit, 11-mount up/down counter, 15...
・Correction Generator Department, 16... Ura Masa Control Department Agent Patent Attorney Akio Takahashi 1st
Figure 2 RO6 s Figure 3 Figure A Figure 5 Figure 6

Claims (1)

[Claims] a movement command generation unit that creates movement commands for the robot; a motor that is servo-controlled by this movement command;
In an industrial robot equipped with a drive section having a deceleration mechanism for transmitting the power generated by the motor to the robot, means for detecting the rotation angle of the motor and the rotation angle of the shaft of the drive section, and comparing both rotation angles. and a means for performing feedback control on a movement command generation section based on the detected torsion angle to output an optimal movement command. Industrial robot control device.