JPH07136961A - Industrial robot control device - Google Patents

Abstract

PURPOSE:To automatically correct the action of a motor according to the ambient temperature of a robot by lowering the acceleration/deceleration or speed of a motor for driving a robot in the case of the ambient temperature of the robot before the start of operation being lower than the reference value. CONSTITUTION:When the power supply of a robot control device 20 is turned on, the ambient temperature of a robot is measured by temperature sensors 10a, 10b, 10c. When the measured value is lower than the reference value, the temperature is calculated. The accelerating/decelerating time to be changed is determined by the degree of difference between the measured temperature and the reference value temperature and also by the acting attitude of the robot. The change of the set speed is then determined in the same way as the change of the accelerating/decelerating time. Reference torque to return to normal action is also determined. The commands of the accelerating/ decelerating time and set speed after the change of setting are supplied to a motor 12. At the same time, the contents of change is displayed on a display device such as a CRT. Simultaneously with motor starting, sampling time is started wherein generated torque is monitored.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a controller for an industrial robot.

[0002]

2. Description of the Related Art Conventionally, as shown in FIG. 4, acceleration / deceleration time and operation speed are commanded in a fixed pattern. On the other hand, Japanese Unexamined Patent Publication No. Sho 64-20990 discloses a technique of detecting the temperature of a servo motor that drives a robot and automatically increasing or decreasing the operating speed of the robot.

[0003]

However, although the temperature of the servo motor itself actually becomes a problem, there are cases where the ambient temperature before the start of operation has a greater influence on the robot operation. That is, the friction torque of the speed reducer, the ball screw, the motor, etc. used in the drive system of the robot manipulator increases as the temperature decreases due to the influence of the change in the viscosity of the grease and oil used as the lubricant.
As a result, the increase in the friction torque at low temperature increases the motor required torque during acceleration / deceleration, and the required torque exceeds the maximum value of the motor-generated torque during the predetermined acceleration / deceleration time, making it impossible to operate as instructed. , An alarm will be generated and the robot will stop. Further, even at a constant speed, especially at a high speed, the required torque increases, an overload alarm occurs, and the robot stops.
In particular, this problem occurs in winter and low temperature applications, and as a result, the operating speed and the acceleration / deceleration time have been changed to cope with the problem.
As a method of solving such a problem, there is a plan to select a motor that can generate a necessary maximum torque even if the peripheral temperature decreases and the friction torque increases, but this method increases the motor frame, Weight, size, and economy are issues. In this method, in the case of a robot, the motor becomes a load, and it may be difficult to increase the motor frame and weight due to the robot's mechanical structure, and it may not be a simple solution. Therefore, an object of the present invention is to provide a control device for an industrial robot that automatically corrects the motor operation according to the ambient temperature of the robot.

[0004]

The present invention relates to a temperature sensor for measuring the ambient temperature of a robot before the start of operation, and a motor for driving the robot when the ambient temperature measured by the temperature sensor is lower than a reference value. And means for reducing the acceleration / deceleration or the speed.

[0005]

After the power is turned on to the robot controller, the temperature around the robot manipulator is measured by the temperature sensor, and the result is compared with the reference value of the ambient temperature. When the ambient temperature is higher than the reference value, the system is operated at the set work condition speed as it is. If it is lower than the reference value, the acceleration / deceleration time and the change range of the set speed are determined by the magnitude of the difference from the reference value, and the operation is started at that value. If changed and operated, grease will continue,
Since the oil temperature rises and the friction torque decreases, always monitor the motor generated torque after the start and compare it with the generated torque reference value due to the temperature difference when this torque is changed. If this happens, return to normal working conditions and continue operation.

[0006]

Embodiments will be specifically described below with reference to embodiments of the present invention. FIG. 1 is a block diagram of an industrial robot embodying the present invention. In the figure, 20 is a robot controller, 40
Is a robot mechanism unit to which the servo motor 12 is attached. In 10a, the temperature sensor is used in the robot controller.
Reference numeral b shows the case where the temperature sensor is attached to the robot mechanism portion, and reference numeral 10c shows the case where the temperature sensor is attached to each axis of the servomotor or any one of them. However, in any case, it is necessary to mount the sensor so that the ambient temperature can be measured instead of the temperature of the mounted part. The control device 20 has a central processing unit (hereinafter referred to as CPU) 1, and the CPU 1 is connected to a memory 2 formed of a ROM, a memory 3 formed of a RAM, an axis control unit input / output interface 8 and the like via a data bus 9. A servo amplifier 7 that drives a servo motor 12 for each axis of the robot is connected to the axis control unit 6. The I / O interface 8 turns on / off the servo amplifier 7
It has an O signal circuit. The temperature around the robot is measured by temperature sensors 10a, 10b, 10c such as thermistors, and the measured values are converted into digital signals by the A / D converter 11 and input to the central processing unit 1 through the input / output interface 8. Next, this embodiment will be described with reference to the flowchart of FIG. When the robot controller power is turned on (step 100), the temperature around the robot is measured (step 110). The measured ambient temperature and the reference value are compared (step 120). If the measured value is lower than the reference value, calculate the temperature. Depending on the magnitude of the difference between the measured temperature and the reference value temperature, the acceleration / deceleration time to be changed is
It is also determined by the operating posture of the robot. The change in the speed set next is determined in the same manner as the change in the acceleration / deceleration time. Further, the reference torque for returning to the normal operation is determined (step 130). The command of the acceleration / deceleration time after the setting change and the set speed is given to the motor (step 140). At the same time, the changed contents are displayed on a display device such as a CRT (step 150). When the motor starts, the generated torque is monitored and starts at a sampling time (step 1
60). The reference torque for returning to the normal operation determined when the setting is changed is compared for each sampling time (step 170). If it is larger than the reference value, the operation is continued in the changed state as it is (step 140). If the value is smaller than the reference value, the setting is changed back to continue the operation and the display of the change is stopped (step 180). If the ambient temperature is higher than the reference value, the operation is continued at the set speed (step 180). When the power is turned on, the above loop is constantly repeated.

[0007]

As described above, when the ambient temperature before the start of operation is lower than the reference value, by changing the acceleration / deceleration time and the set speed, the torque shortage due to the increase in friction torque does not occur. Start-up operation can be performed without stopping. Further, when the friction torque decreases after the operation, the initial setting speed is automatically returned, so that it is possible to cope with the increase in the friction torque at low temperature without bothering the operator and without increasing the motor frame.

[Brief description of drawings]

FIG. 1 is a block diagram of an industrial robot that implements the present invention.

FIG. 2 is a flowchart showing the operation of the embodiment of the present invention.

FIG. 3 is an explanatory diagram for comparison with a conventional method when the acceleration / deceleration time and the steady speed command of this embodiment are changed.

FIG. 4 is an explanatory diagram showing an example of conventional acceleration / deceleration time and steady speed command.

[Explanation of symbols]

 1 CPU 2 Memory (ROM) 3 Memory (RAM) 4 Operation Panel 5 Teach Box 6 Axis Controller 7 Servo Amplifier 8 Input / Output Interface 9 Data Bus 10a, 10b, 10c Temperature Sensor 11 A / C Converter 12 Servo Motor 20 Robot Control Device 40 Robot mechanism 41 Work jig

Claims (3)

[Claims] 1. A temperature sensor for measuring the ambient temperature of a robot before the start of operation, and a means for lowering the acceleration / deceleration or the speed of a motor for driving the robot when the ambient temperature measured by the temperature sensor is lower than a reference value. An industrial robot control device comprising: 2. The control device for an industrial robot according to claim 1, wherein the acceleration / deceleration or the change range of the speed is automatically set according to the difference between the detected temperature and the reference temperature. 3. The motor torque is monitored after the operation,
The industrial robot controller according to claim 1, further comprising means for returning the operation to the initially set working condition when the value becomes smaller than the changed acceleration / deceleration or the reference value corresponding to the speed.