JPS62140786A - 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 Technical Field of the Invention The present invention relates to an industrial robot control device having a function of measuring dynamic friction torque and 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 rotational drive source for 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 dynamic friction torque and backlash amount of the drive system as necessary to check the lifespan and maintenance cycle of the robot. However, with conventional industrial robots,
Since there is no self-detection function for these, the user side must use, for example, a tertiary light meter, ammeter, torque meter, etc.
It is necessary to prepare measuring instruments such as dial gauges and special jigs to carry out measurement work, which is expensive.
It was also inefficient.

<Object of the invention> This invention is intended to solve the above problems,
The purpose of this invention is to provide a new industrial robot control device that has a function that can self-detect the dynamic friction torque and amount of backlash in the drive system.

<Structure and Effects of the Invention> In order to achieve the above object, the industrial i-robot of the present invention includes: a drive source for driving the rotating shaft of the robot joint in forward and reverse rotation; and detecting the rotational angular position of the rotating shaft. position detection means for outputting position information based on the current command value and position information; drive control means for outputting a current command value for operating the drive source at a predetermined speed during calibration; +
It was decided to include a measuring means for measuring the friction torque and the amount of backlash.

According to this invention, since the dynamic friction torque and backlash amount of the drive system are self-detected using the current command value and position information, the dynamic friction torque and backlash amount that change with the number of robot operations and time can be detected each time. The optimum compensation value can be set, allowing efficient control. In addition, by detecting a sudden increase in dynamic friction torque, it is possible to determine the lifespan of the robot or abnormalities, and the amount of increase in backlash can be used as a guideline for maintenance such as when to adjust backlash, thereby improving robot safety. and reliability can be ditto.

Furthermore, since no special detector or jig is required to detect the dynamic friction torque and backlash amount, the measurement cost is low and the efficiency of the measurement work is improved. Moreover, since dynamic friction torque and backlash amount are detected during calibration, which is performed every time the robot starts operating, accurate and reliable self-diagnosis is possible, greatly improving the safety and reliability of the robot. etc., it achieves the remarkable effect of achieving the purpose of the invention.

<Description of Embodiment> Fig. 1 shows a schematic configuration of an industrial robot according to an embodiment of the present invention. It is composed of a control device (shown in FIG. 2) that controls a series of operations.

This robot body RB has six degrees of freedom, and six joints 1 to 6 have rotational degrees of freedom of θ1 to θ6 (in this specification, in addition to the original rotation, the rotational degrees of freedom are also (referred to as the "rotational degree of freedom"). These joints 1-6 are each independently driven by DC servo motors M1-M6 (shown in FIG. 2) each having a gear reduction mechanism, so that the rotating shafts of each joint 1-6 are rotated in forward and reverse directions.

Figure 2 shows the industrial robot system 1-system? The schematic configuration of the I[l device is shown.

In the illustrated example, the CPU 7 constitutes a computer together with the ROM 8 and RAM 9, as well as the keyboard 10 and CRTII, and executes various calculations and processes such as command analysis, current command value calculation, and calculation of dynamic friction torque and backlash amount.

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.
, and these servo amplifiers A1 to A6
amplifies each output value from the CPU 7 and provides it to each of the servo motors M1 to M. Encoder E
l-E b C. An incremental rotary encoder attached to each of the servo motors M1 to M6, which detects the rotation angle of each motor and provides it to the CPU 7. Each of these incremental type encoders E1~
E6 outputs output pulses (for example, 1000 pulses per rotation) according to the rotation angle as A-phase and B-phase outputs, and a reference signal (for example, 1 pulse per rotation) that provides the reference position of rotation as a Z-phase output. Output.

Mechanical stoppers (not shown) for defining the rotational angle range of the rotational shaft are provided in each of the joints 1 to 6, corresponding to each end position of the rotational shaft in the positive and negative rotational directions.

FIG. 3 shows the rotation angle range of the rotary shaft 12 for the first joint 1, the arrangement positions S of the mechanical stoppers at both ends,
, S2, and in the illustrated example, the origin P is set at an intermediate position of the rotation angle range (the same applies to other joints). In addition, in the figure, Z, ~Z, is the rotation axis 12
It shows the angular position at which encoder E outputs the Z-phase output (reference signal) when the encoder E rotates.

The positioning (calibration) of the above origin PL (however, 1 = L2..., 6) is performed using the encoders E1 to E,
Calibration is performed after the power is turned on using the A-phase or B-phase output and Z-phase output of the ,I? It is configured to measure rubbing torque and backlash.

Figure 4 shows the specific steps and order.
The calibration for the joint part 1 and the accompanying processing (the same applies to the second to sixth joint parts 2 to 6) are carried out by the fourth
This will be explained based on the diagram.

Note that in this calibration, the CPU 7
In addition to functioning as a detection means for detecting that the robot joints 1 to 6 have come into contact with the mechanical stopper, and a control means for driving and stopping the motors M1 to M, and setting the rotation direction, Executes various calculations and processes related to calibration and measurement of dynamic friction torque and backlash amount. Further, the ROM 8 is used to store programs for executing calibration and the like, and the RAM 9 is used as a work area in addition to storing various data.

In step 1 of FIG. 4 (indicated by rsTlj in the figure), when a command to execute calibration is input from the keyboard 10, the CPU 7 controls the servo motors M,
Drive J to rotate the first joint 10 rotation shaft 12 at a constant speed in the positive and concave directions (see Figure 3) (Step 2)
.

In this operation, as shown in Fig. 2, the output pulse (human phase or B phase output) of the encoder El is input into the CPU, the CPU 7 executes calculations for the servo system for position control, and the current is the result of the calculation. A command value is commanded to the servo amplifier A1 to rotationally drive the motor M1.

In the next step 3, the current command value when the servo motor M1 rotates at a constant speed is stored in the storage area of the RAM 9 or the CPU 7 as the dynamic friction torque of the drive system.

By the way, in general, the torque T of a certain rotational drive system is given by the following equation 0, where J is the inertia, C is the viscous braking coefficient, and TF is the dynamic friction torque.

T=Jθ+Cδ+TF...■ However, SA is the angular velocity and θ is the angular acceleration.

On the other hand, the torque T, generated by the motor. If the motor torque constant is , and the motor current value is 1, then T. −to,
I...■ becomes.

From the above formula 00, if we set T KO = Jθ + Cθ + TF””■, when the rotating shaft is driven at low speed and constant speed control, θ-0. The value becomes θ-0, and 《gino》2 is established.

T... =TF = Kt I...■This 0
As is clear from the equation, the dynamic friction torque 'FF is proportional to the current command value (corresponding to ■ in equation 0), and in the case of this example, this current command value ■ is expressed as The torque is stored in the RAM 9 or the storage area in the CPU 7 (step 3).

In step 4, the CPU 7 determines whether or not the stored current command value is smaller than a predetermined reference value set in advance.

For example, if there is surface pressure fatigue on the gears in the gear reduction mechanism, or if there is an abnormality in friction torque due to too much backlash, the determination in step 4 will be "No".
In step 13, the abnormality is displayed on the RTll or the like to notify the staff, and in the next step 14, the operation of the robot is forcibly stopped.

If the current command value is smaller than the reference value and the determination in step 4 is "YES", the CPU calculates a dynamic friction compensation value from this current command value and automatically sets it.

In this way, the rotational shafts 12 of the first joints 1 rotate by appropriate angles, and when the joints 1 come into contact with the mechanical stopper, the rotational movement of the joints is stopped. This contact with the mechanical stopper can be detected by a method of determining whether the current speed of the joint 1 is zero, a method of determining whether the current value of the motor Ml is greater than a certain reference value, etc. When the CPU 7 detects that the part 1 has come into contact with the mechanism 1-flange, the determination in step 6 becomes "YIES" and the process proceeds to step 7. In this step 7, the CPU 1 controls the joint part 1 based on the number of output pulses output by the encoder E.
The position information e of the rotating shaft 12 at the time when the rotary shaft 12 contacts the mechanical stopper is obtained and stored. Next, in step 8, the CPU 7 reversely drives the motor M1 to rotate the rotary shaft 12 in a negative rotation direction (opposite direction) at a low and constant speed. This will result in step 7, "Did the motor reverse?" ]
The determination becomes "YBS", and then the CPU 7 detects the point in time when the current command value increases rapidly, that is, the point in time when the rotational force of the motor M1 is transmitted to the rotating shaft 12 of the first joint part 1, and The position information e2 of the rotating shaft 12 is sent to the encoder E.
It is determined from the number of output pulses of .

FIG. 5 shows the change characteristics of the current command value with respect to time t.

In the figure, A indicates the time period during which the rotating shaft 12 is rotating toward the mechanical stopper, and tl indicates the time point when the joint portion 1 hits the mechanical stopper. The next time period B means a time period in which the joint portion 1 is in contact with the mechanical stopper, and in this time period B, the current command value is significantly large. Time t7 indicates the point in time when the joint 1 slips ^1 from the mechanical stopper and starts rotating in the opposite direction. In the next time period C, the backlash range of the gear reduction mechanism is 10
In this case, the rotational force that drives only the motor shaft is sufficient, and the current command value takes a small value. At time t3, the rotational force of motor M is transmitted to joint 1, and from then on a large current command value is required due to the friction torque and inertia of the shafts of the drive system other than motor 1 (time period D).
).

Returning to FIG. 4, in the next step 11, 11″li
Location information? h eI + e2 difference je, -e21 as h
7, and it is determined whether this is smaller than a predetermined reference value. And if that elf definition is ”)
4Q", the operator is notified in step 13 that the robot has an abnormality, and the operation of the robot is stopped in the following step 14. On the other hand, if step 11 is "YES", Proceeding to step 12, the calibration process is continued.That is, as the rotary shaft 12 rotates, the CPU 7 counts the number of output pulses of the encoder E, and also counts the number of output pulses of the encoder E.
, waits for a reference signal (Z-phase output) of one pulse per rotation to be sent.

When the encoder E receives the first reference signal, the CPU 7 generates information indicating the output position Z1 of the first reference signal with respect to the origin P1 (A phase or B phase of the encoder E+).
R as the current position information (value converted to phase output count value)
The calibration is completed by writing to a predetermined area of AM9 and stopping the rotation of motor M.

[Brief explanation of drawings]

FIG. 1 is a diagram showing a schematic configuration of an industrial robot according to an embodiment of the present invention, FIG. 2 is a block diagram showing an example of a circuit configuration of an industrial robot control device, and FIG. 3 is a rotation angle range of a joint part. FIG. 4 is a flowchart showing the calibration control operation, and FIG. 5 is a diagram showing the change characteristics of the current command value over time. 1 to 6...Joint 7...CPU M1 to M6...Servo motor E, ~E,...Encoder patent Applicant Tateishi Electric Co., Ltd. Agent Patent attorney Mitsuru Suzuki Yama - → + ノ ) Z correction,, l-6 separate kansei theory 7 chosun lL +B port %Izu, kui lower 9 show 4 flow -F-fu + s l:Zl den 54'L talent 4≧4JL・Changei Otsu 4 Existence・TojijiDSrノ3 5r/〃

Claims (4)

[Claims] (1) A drive source for driving the rotary shaft of the robot joint in forward and reverse rotation; a position detection means for detecting the rotational angular position of the rotary shaft and outputting position information; and a drive source for driving the drive source at a predetermined speed during calibration. An industrial robot control comprising: a drive control means that outputs a current command value for operating the robot; and a measurement means that measures the dynamic friction torque and backlash amount of the drive system based on the current command value and position information. Device. (2) The industrial robot control device according to claim 1, wherein the drive source is a DC servo motor having a gear reduction mechanism. (3) The industrial robot control device according to claim 1, wherein the position detection means is a rotary encoder. (4) The industrial robot control device according to claim 1, wherein the drive control means and the measurement means are computers.