JPS62150405A - Industrial robot controller - Google Patents

Abstract

PURPOSE:To improve the safety and reliability of a robot by detecting by itself a backlash of a drive system based on position information of a position detector and setting an optimum compensation at each occasion. CONSTITUTION:An industrial robot is provided with a drive system 14 to the 2nd joint 2 between a base 12 and the 1st arm 13 and the attitude of the 2nd joint 2 is kept constant by providing a joint fixing jig 15 between the base 12 and the 1st arm 13. The robot is controlled by a controller comprising a microcomputer consisting of a CPU, a ROM, a RAM and a keyboard or the like, and the controller executes a processing relating to the detection of backlash. In order to apply self-detection to the backlash, the joint 2 is fixed and a bipolar current command is given to the drive system 14 to obtain a rotary angular position for the case thereby calculating the backlash of the drive system 14 from the difference. Thus,the control of the robot is executed with high accuracy by using the result as a controlled variable.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field of the Invention The present invention relates to an industrial robot control device having a function of measuring the amount of backlash in a drive system.

<Background of the Invention> For example, in an articulated industrial robot, a DC servo motor having a gear reduction mechanism capable of forward and reverse rotation is usually used as a drive system for rotating each joint. In the case of this type of configuration, in order to improve the safety and reliability of the robot, it is desirable to detect the amount of backlash in the drive system as necessary to check the lifespan and maintenance cycle of the robot. However, conventional industrial robots do not have the ability to self-detect these, so for example, as shown in Figure 6,
After fixing the motor shaft of the DC servo motor that rotationally drives the robot joint 31 and finding the rattling of the output shaft of the gear reduction mechanism from the displacement δ of the arm 32, calculate the following The hacklash Lt BL L is calculated.

δ BL-jan-’□・・・・■ ! However, l is the length of the arm 32.

However, in this method, a special measuring instrument 3 such as a dial gauge or a three-dimensional measuring device is required to determine the displacement of the arm 32.
3 and a special jig 34 for setting the same, the measurement is expensive and inefficient, and it is extremely difficult for the user to measure it.

<Object of the invention> This invention is intended to solve the above problems,
The purpose of the present invention is to provide a new industrial robot control device having a function of self-detecting the amount of hacklash in a drive system.

<Structure and Effects of the Invention> In order to achieve the above object, the industrial robot control device of the present invention includes a drive system for driving the robot joints in forward and reverse rotation, and a rotation angle position of this drive system that is detected. a position detection device such as a low-resolution encoder that outputs position information; a drive control means that applies predetermined positive and negative current command values to the drive system with the robot joints fixed; and each of the positive and negative current command values Determining the rotational angular position of the drive system at a given time from the output information of the position detection device,
It was decided to provide a measuring means for calculating the backlash amount of the drive system from the difference.

According to this invention, the amount of backlash in the drive system can be self-detected based on the position information output by the position detection device, so the compensation value is optimized each time for the amount of backlash that changes with the number of robot operations and time. can be set, enabling efficient control. In addition, the increase in the amount of hacklash can be used as a guideline for maintenance such as when to adjust backlash, improving the safety and reliability of the robot. Furthermore, since no special detector or jig is required to detect the amount of backlash, the measurement cost is reduced and the efficiency of the measurement work is improved. Moreover, since the amount of hacklash can be detected on the user side, accurate and reliable self-diagnosis is possible, and the safety and reliability of the robot can be significantly improved, achieving the remarkable effects of achieving the purpose of the invention.

<Description of Embodiment> FIG. 3 shows a schematic configuration of an industrial robot according to an embodiment of the present invention. It consists of a control device (shown in FIG. 4) that controls a series of operations.

This robot body R[3 has 6 degrees of freedom, and 6
Each of the joints 1 to 6 has rotational degrees of freedom of θ1 to θ6 (in this specification, in addition to the original rotation, the turning degrees of freedom are also referred to as "rotational degrees of freedom"). These joints 1-6 are independently driven by DC servo motors M1-M6 (shown in FIG. 4) each having a gear reduction mechanism, thereby causing the rotation shafts of each joint 1-6 to rotate in forward and reverse directions.

FIG. 4 shows a schematic configuration of an industrial robot control device.

In the illustrated example, the CPU 7 constitutes a microcomputer together with the ROM 8 and RAM 9, as well as the keyboard 10 and CRTII, and is capable of processing command analysis, current command value calculation, etc.
Executes various calculations and processes such as calculating the amount of backlash. The ROM 8 stores programs for controlling the robot, and the RAM 9 stores calculation results and other data.

The output of CPU7 (current command value) is output from servo amplifiers A1 to A.
6, and these servo amplifiers A1 to A,
amplifies each output value from the CPU 7 and provides it to each of the servo motors M to Mb. Encoder E1
~Eh is an incremental type rotary encoder attached to each of the servo motors M and ~M6, which detects the rotation angle of each motor and provides it to the CPU 7. Each encoder E, ~E, of this incremental type is A
Output pulses according to the rotation angle as phase and B phase outputs (
For example, 1000 pulses per revolution) are output, and a reference signal (for example, 1 pulse per revolution) that provides a reference position of rotation is output as a Z-phase output.

In the industrial robot having the above configuration, FIG. 1 shows a situation in which the amount of backlash of the drive system 14 of the second joint 2 between the base 12 and the first arm 13 is measured.

A joint fixing device 15 is disposed between the base portion 12 and the first arm 13, and this joint fixing device 15 holds the second joint portion 2 in a constant posture.

The joint fixing device 15 can be of any shape or structure as long as it can fix the robot joint, but the illustrated example allows the first arm 13 to be freely moved at any position within the entire operating angle and degree range. It is constructed so that it can be fixed. That is, the joint fixing device 15 of this embodiment is similar to that shown in FIGS. 1 and 2.
As shown in the figure, ゛ has a circular arc shape of W' 180 degrees, and a bolt 16 is installed at the center of the width of the plate surface over the entire arc length.
An arcuate groove 20 for engaging the parts 1 to 19 is opened.

Thus, the base portion 12 and the first arm 13 are each provided with two screw holes (not shown) at concentric positions, and the first arm 13 is set in a desired posture with respect to the base portion 12. Next, in this state, as shown in FIG. 2, screw the two bolts 16 and 17 through the arc groove 20 of the joint fixing device 15 into the screw hole of the base portion 12 to connect the base portion 12 and the joint fixing device 15. Fix and add 2 more poles)18.
19, similarly connect the first arm 13 and the joint fixing device 15.
and thereby fix the base portion 12 and the first arm 13.
In other words, the second joint portion 2 is completely fixed.

After completing the fixing work, the amount of backlash of the drive system 14 at the second joint portion 2 is detected by sequentially executing the steps shown in FIG.

In addition, in this backlash amount detection processing, the CPU 7 functions as a control means for driving and stopping the servo motor M2, setting the rotation direction, etc., and also performs various calculations related to backlash amount detection. Execute processing. Further, the ROM 8 stores a program for executing backlash amount detection processing, and also stores a program for executing backlash amount detection processing.
AM9 stores various data and is also used as a work area.

At the start point in FIG. 5, when a bank crash measurement command is first input from the keyboard 10, the CPU 7 in step 1 (indicated by rsTIJ in the figure) generates a current of about 10% of the maximum output torque of the servo motor M2. A command value 11 is given to the servo amplifier A2 to apply a driving force to the servo motor M2. As a result, the motor M2 is rotated by an appropriate angle, and the encoder E,
Location information will be output. This position information is input to the CPU 7 in the next step 2, and the CPU 7 then controls the servo motor M! The rotation angle position 1 is read and this read data is stored in the RAM 9. Next, CPU7
In step 3, a current command value It much smaller than the current command value I (for example, about 3% of the motor maximum output torque) is applied to the servo amplifier A2 to reduce the driving force to the servo motor M2.

By the way, under the condition of step 1 where the large current command value 11 is given, in addition to the backlash of the gear reduction mechanism, the elastic force of the drive system affects the rotational displacement of the servo motor M2. It's a big thing. Therefore, by reducing the current command value in step 3, the torsional displacement due to the elastic force of the drive system can be eliminated. As a result, the servo motor Mt moves backward by a slight angle, and position information corresponding to the rotation angle position is outputted from the encoder E2. and CPU
7 is the next step 4, manually input this location information,
Read the motor position 2 and send this read data to RA.
Store in M9. Further, in step 5, the CPU 7 sets the current command value to the motor M2 to zero to completely eliminate the influence of the elastic force of the drive system, and in the next step 6, changes the current position L3 of the servo motor M2 to the encoder E2. The information is read from the output information and stored in the RAM 9.

Next, in step 7, the CPU 7 gives a negative current command value (-T,) of about 10% of the maximum output torque to the servo amplifier A2 to apply a driving force in the opposite direction to the previous one on the servo motor M2. . As a result, the motor Mt is rotated in the opposite direction by an angle corresponding to the sum of the backlash amount of the gear reduction mechanism and the torsional displacement due to the elastic force of the drive system, and the motor Mt is rotated to a position corresponding to the rotation angle position. Information is output from encoder E2. In the next step 8, the CPU 7 inputs this position information and determines the motor position 4.
is read and this read data is stored in the RAM 9.

Furthermore, for the same reason as above, the CPU 7 gives a negative current command value <Iz) of approximately 3% of the motor maximum output torque to the servo amplifier A2 to reduce the driving force to the servo motor M2, and at this time. The CPU 7 reads the motor position HLs from the output information of the encoder E2 (step 9.10), and further, in step 11, the CPU 7 sets the current command value to the motor M2 to zero to completely eliminate the influence of the elastic force of the drive system. , In the next step 12, the position of the motor M2 at that time is read from the output information of the encoder E2.

Thus, in step 13, the CPU 7 controls the motor M.
2 position, iL, calculate the difference (t, 6-L3),
The calculation result is displayed on CR'f"11. In this case, each 1ft, +~Lb of motor M!
If displayed in conjunction with II, the influence of the elastic force of the drive system can also be understood.

Assuming that the value of the difference (L, -L3) is "10" as the result of the above calculation, if the resolution E of the encoder E2 is 100 OP/r and the reduction ratio i is 50, then the second joint 2 is The wobbling angle, that is, the backlash IBL of the drive system 14 can be obtained by the following calculation.

= 0.072° = 4 minutes 19.2 seconds Even if the amount of backlash is measured at only one location, it is possible to obtain a guideline for maintenance such as adjustment timing. If the amount of bank crash at multiple locations is measured by executing the procedure shown in the figure, and this is used as the control amount, the robot can be controlled with higher precision.

Moreover, although the procedure for measuring the amount of backlash for the second joint portion 2 has been described above, it is of course possible to measure the amount of backlash for other joint portions by the same procedure.

[Brief explanation of drawings]

Fig. 1 is a perspective view of the industrial robot showing the backlash measurement state, Fig. 2 is an enlarged rear view of the main parts showing the joint fixation state, and Fig. 3 is an explanatory diagram showing the overall configuration of the industrial robot.
FIG. 4 is a block diagram showing the circuit configuration of an industrial robot control device, FIG. 5 is a flow chart showing a backlash measurement procedure, and FIG. 6 is a front view showing a conventional buff crash measurement method. 1-6...joint part 7...cpuM1-M
6...Servo motors E1 to E,...Encoder 14...Drive system 15...Joint fixing device patent Applicant: Tateishi Electric Co., Ltd.

Claims (1)

[Scope of Claims] 1. A drive system for driving the robot joint in forward and reverse rotation, a position detection device that detects the rotational angular position of the drive system and outputs position information, and a state in which the robot joint is fixed. a drive control means for giving predetermined positive and negative current command values to the drive system; and determining the rotational angular position of the drive system when each of the positive and negative current command values is given from the output information of the position detection device;
An industrial robot control device comprising measuring means for calculating the amount of backlash in a drive system from the difference. 2. The industrial robot control device according to claim 1, wherein the drive system includes a DC servo motor having a gear reduction mechanism. 3. The industrial robot control device according to claim 1, wherein the position detection device is a rotary encoder. 4. The industrial robot control device according to claim 1, wherein the drive control means and the measurement means are microcomputers.