JPH03215178A - Protecting method for servo-motor - Google Patents

Abstract

PURPOSE:To enable a servo-motor to be protected without using special heaters or the like by applying artificial disturbance torque to said servo-motor for a fixed time when the temperature of the coil or magnet of the servo-motor is equal to or lower than a specified temperature, and by heightening the temperature of said magnet or said coil. CONSTITUTION:The temperature Temp of the magnet or coil of a servo-motor 10 is measured and is fed to a processor 1. By the processor 1, the temperature Temp is compared with a previously set specified-value, and when the temperature is lower than the value, then the output of artificial disturbance torque command Tg is generated, and position command Pc is turned OFF, and the integrating gain K1 of a feed forward loop is set to be 0. When the temperature is turned into a temperature equal to or higher than a constant temperature, then the artificial disturbance torque command Tg is turned OFF, and the output of the position command Pc is generated from the processor 1, and the integrating gain K1 of the feed forward loop is also returned to a normal value.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method for protecting a servo motor used at low temperatures, and particularly a method for protecting a servo motor for an industrial robot used at low temperatures such as in a freezer. Regarding.

[Conventional technology]

Industrial robots are widely used in a wide range of industrial fields as a powerful means of labor saving. These fields are increasingly being used not only under normal temperature conditions, but also under high or low temperatures.

Among these, industrial robots used at low temperatures, such as in freezers, have the problem of magnet demagnetization. That is, as the temperature decreases, the limit value of the demagnetizing current decreases, and demagnetization occurs due to the armature current of the servo motor, which is safe at room temperature.

In order to solve these problems, the following measures have been taken.

The first method is to provide a separate heater to raise the temperature of the servo motor so that the servo motor is always used at room temperature.

The second method is to use a magnet made of a material with good temperature characteristics of demagnetizing current value.

The third method is to limit the current value of the servo motor used at low temperatures to a safe value and use it at low torque.

[Problem to be solved by the invention]

However, the first method requires a heater for each servo motor, so it cannot be used in fields such as industrial robots that use many servo motors and require a simple structure, and the structure is complicated. , the cost burden is also large.

The second method requires a large number of servo motors, such as in industrial robots, and has a large cost burden.

In the third method, the generated torque is low, the operating speed is reduced,
Moreover, the payload of industrial robots also decreases.

The present invention has been made in view of these points, and an object of the present invention is to provide a servo motor protection method that protects the servo motor without using a special heater or the like.

Another object of the present invention is to provide a method for protecting a servo motor that does not limit the generated torque under normal operating conditions.

[Means to solve the problem]

In order to solve the above-mentioned problems, the present invention provides a method for protecting a servo motor of an industrial robot or the like used under low temperatures, in which the temperature of the coil or magnet of the servo motor is detected at a predetermined period, and the temperature is set to a predetermined value. When the temperature is below
Applying a pseudo disturbance torque to the servo motor for a certain period of time,
A method for protecting a servo motor is provided, the method comprising increasing the temperature of the magnet or the coil.

Further, in a method for protecting a servo motor of an industrial robot or the like used under low temperatures, the temperature of a coil or magnet of the servo motor is detected at a predetermined period, and when the temperature is below a predetermined temperature, the servo motor is Provided is a method for protecting a servo motor, which is characterized by limiting a torque command value to a servo motor.

[Effect]

Measures the temperature of the servo motor coil or magnet at regular intervals. When this temperature is below a predetermined temperature, a pseudo-disturbance command is given to the servo motor, current is passed through the coil, and the temperature of the coil and magnet is increased. After the temperature of the coil and magnet has risen, normal operation is performed.

In addition, the temperature of the coil or magnet is measured at regular intervals,
When the temperature is below a certain value, the command torque value, that is, the armature current is limited. This control is performed at regular intervals, so if the operating state continues, the temperature of the magnet and coil will rise.
After a certain period of time, the limit on the torque command value is lifted and the vehicle can be operated with normal torque. In other words, the torque is limited only at the start of operation, and during normal operation there is no torque limitation at low temperatures.

〔Example〕

Hereinafter, one embodiment of the present invention will be described based on the drawings.

FIG. 4 is a block diagram of a servo motor control system for implementing the present invention. Normally, the processor 1 outputs a position command Pc. The adder 2 outputs a positional deviation Ep that is the difference between the position command Pc and the actual actual position P. Position deviation E
The speed command Vc is output by multiplying p by the position gain Kp3. Adder 4 outputs speed deviation EV, which is the difference between speed command Vc and actual speed V.

The adder 7 outputs a torque command Tc, which is the difference between the value obtained by multiplying the speed deviation Ev by the speed gain Kv5 and the value obtained by multiplying the speed deviation Ev by the feedforward gain K1 and integrating the result. Adder 8 outputs torque command T which is the sum of torque command Tc and simulated disturbance torque command Tg. Multiplying the torque command T by the torque constant Kt9 yields the current command value to the servo motor 10.

The servo motor 10 has a built-in pulse coder for position detection, and the actual speed V is determined from the pulse coder by the adder 4.
will be returned to. Further, the actual velocity V is integrated by an integrator 11 to determine the actual position P, which is fed back to the adder 2.

Also, the temperature T of the magnet or coil of the servo motor 10
e m p is measured and sent to processor 1. The processor compares this temperature T e m p with a predetermined value, and if it is lower than that, outputs a simulated disturbance torque command Tg, turns off the position command Pc, and further changes the integral gain K1 of the feedforward loop. Set to 0. This simulated disturbance torque Tg is 50 to 80% of the rated torque. Of course, these values are determined by the capacity of the servo motor, the temperature conditions used, the demagnetizing current of the servo motor, etc.

As a result, only the simulated disturbance torque Tg is applied to the servo motor 11, and there is no actual movement, but a constant current flows.
The current in the magnet and coil increases.

If the temperature exceeds a predetermined temperature, the simulated disturbance torque command T
g is turned off, the position command Pc is output from the processor 1, and the integral gain K1 of the feedforward loop is also returned to its normal value.

In addition, as another method, when the temperature T e m p of the magnet or coil of the servo motor 11 is lower than a predetermined temperature, the processor 1 provides a torque limiting circuit 12 as shown by the broken line, and reduces the torque to 10 T1. -Tl. As a result, at the start of operation, the temperature of the magnet and coil of the servo motor is low, so the torque can be suppressed, but after operation for a certain period of time, the temperature of the magnet and coil rises, and the servo motor can be operated with normal torque.

FIG. 1 is a flowchart of a first embodiment of the present invention. In the figure, the number following S indicates the step number.

[S1] Servo motor magnet or coil temperature T
e m p is measured and compared with a predetermined temperature Tx, and if it is smaller than Tx, the process proceeds to S2; otherwise, the process proceeds to S3.

[S2] Find the simulated disturbance torque Tg.

[S3] The simulated disturbance torque Tg is set to 0.

[S4] The simulated disturbance torque Tg is output to the adder 8 in FIG.

FIG. 2 is a flow chart of a second embodiment of the present invention. The difference from FIG. 1 is that the position command P
c and the integral gain K1 of the feedforward loop are set to zero. (S13) FIG. 3 is a flowchart of the third embodiment of the present invention.

[S21:] Measure the temperature T e m p of the magnet or coil of the servo motor, compare it with a predetermined temperature Tx, and set T
If it is smaller than x, proceed to S22; otherwise, proceed to S24.

[S22] Find the limit torque T1.

[S23:]} Set the limit range of torque to 10T1 to 1T1.

[S24:]} The torque limit range is the normal torque limit range.

[S25:l} Give the torque limit range to the torque limit circuit 12.

If such processing is repeated at regular intervals, the torque will be limited at the start of operation, but the servo motor 11 will be
If the temperature of the magnet and coil rises, the motor can be operated with normal torque. Moreover, this is done automatically within the robot controller.

FIG. 5 is a schematic block diagram of a robot control device for implementing the present invention. The robot control device has a processor board 31, and the processor board 31 includes a processor 3 1 a, ROM 3 l b, and RAM 3 1 c.
There is. The processor 31a controls the entire robot control device 30 according to a system program stored in the ROM 3lb. The program for protecting the servo motor described above is also included in this system program. Processor 31a corresponds to processor 1 in FIG.

Various data are stored in the RAM 31c, including a predetermined temperature Tx. A part of the RAM 31c is configured as a non-volatile memory, and operating programs and the like are stored in the non-volatile memory portion. processor board 3
1 is coupled to bus 39.

Digital servo control circuit 32 is coupled to bus 39;
In response to a command from the processor board 31, the servo motors 51, 52, 53, 5 are activated via the servo amplifier 33.
4, 55 and 56. These servo motors are built into the robot 1 and operate each axis of the robot 1. Note that the temperature of each servo motor 51 to 56 is sent to the processor 31a via the servo amplifier 33 and the digital servo control circuit 32. Most of the controls other than temperature control in the servo control system shown in FIG. 4 are performed by this digital servo control circuit 32.

The serial port 34 is coupled to a bus 39 and connected to a teaching board 57 with a display and other RS232 equipment 58. The teaching operation panel with display is used for manual input of various data. Further, a CRT 36a is connected to the serial port, and the position of each axis is displayed on the CRT 36.

A simulation panel 36b is connected to the digital I/035. In addition, digital I/035 and analog I/
Data etc. are output via 037. Further, the large capacity memory 38 stores teaching data, data other than those currently in use, and the like.

In the above explanation, the servo motor protection method has been explained for robots, but it goes without saying that the method can be similarly applied to servo motors used in other devices.

〔Effect of the invention〕

As explained above, in the present invention, the temperature of the magnet, etc. of the servo motor is measured and a simulated disturbance torque is applied, so that the temperature of the magnet, etc. can be increased simply by controlling the servo motor control system. There is no need for a special heater or the like, and there is no need to use a magnet made of a particularly expensive material.

Furthermore, since the torque is limited only while the temperature of the magnet etc. is low, the machine can be operated with normal torque after a certain period of time.

[Brief explanation of drawings]

FIG. 1 is a flowchart of a first embodiment of the present invention, FIG. 2 is a flowchart of a second embodiment of the present invention, FIG. 3 is a flowchart of a third embodiment of the present invention, and FIG. 4 is a flowchart of a third embodiment of the present invention. A block diagram of a servo motor control system for carrying out the invention. FIG. 5 is a schematic block diagram of a robot control device for carrying out the invention. 1 - Processor 3 -- Position gain (Kp) 5゛ ゜ Speed gain (Kv) 6-゛'゛ Integral gain (k1) 9゜・゜゛・ Torque constant (Kt) 11 - Servo motor 3 1 a-1-Processor 51 to 56 - Servo motor Tg - - - - - - Simulated disturbance torque Temp - Temperature of magnet or coil T1
(1) Limit torque

Claims (4)

[Claims] (1) In a method for protecting servo motors of industrial robots, etc. used at low temperatures, the temperature of the coil or magnet of the servo motor is detected at a predetermined period, and when the temperature is below a predetermined temperature, the temperature is detected for a certain period of time. A method for protecting a servo motor, the method comprising: applying a pseudo-disturbance torque to the servo motor to increase the temperature of the magnet or the coil. (2) The servo motor protection method according to claim 1, characterized in that when applying the pseudo disturbance torque, the position command and feedforward integral gain of the control system of the servo motor are set to zero. (3) The servo motor protection method according to claim 1, wherein the pseudo disturbance torque is a sine wave of a predetermined frequency. (4) In a method for protecting a servo motor of an industrial robot or the like used under low temperatures, the temperature of the coil or magnet of the servo motor is detected at a predetermined period, and when the temperature is below a predetermined temperature, the servo motor is A servo motor protection method characterized by limiting a torque command value to the motor.