JP3348425B2 - Industrial robot control device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control device 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, JP-A-64-20990 discloses a technique for detecting the temperature of a servomotor for driving a robot and automatically increasing or decreasing the operation speed of the robot.

[0003]

However, although the temperature of the servomotor itself actually matters, the ambient temperature before the start of operation may have a greater effect on the operation of the robot. That is, the friction torque of the reduction gear, the ball screw, the motor, and the like used in the drive system of the robot manipulator increases as the temperature decreases due to the effect of the change in the viscosity of the grease or oil used as the lubricant.
As a result, the required torque of the motor at the time of acceleration / deceleration increases due to the increase of the friction torque at a low temperature, and the required torque exceeds the maximum value of the motor-generated torque in a predetermined acceleration / deceleration time, so that the operation according to the command cannot be performed. , An alarm occurs and the robot stops. In addition, even at a constant speed, the required torque increases similarly at a high speed, 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 were changed to cope with the problem.
As a method for solving such a problem, there is a plan to select a motor that can generate a necessary maximum torque even when the peripheral temperature decreases and the friction torque increases. Weight, size, and economy are issues. In this method, in the case of a robot, a motor becomes a load, and it may be difficult to increase the motor frame and increase the weight due to the mechanism configuration of the robot, and it may not be simply a solution. Therefore, an object of the present invention is to provide an industrial robot control device that automatically corrects a motor operation according to the ambient temperature of the robot.

[0004]

According to the present invention, there is provided a temperature sensor for measuring an ambient temperature of a robot before operation is started, and when the ambient temperature measured by the temperature sensor is lower than a reference value ,
The motor that drives the robot according to the difference between the ambient temperature and the reference value
Means to reduce the acceleration / deceleration or speed of the motor.
After the operation, the motor torque is monitored and the value changes.
Compared with the reference value corresponding to the additional acceleration / deceleration or speed
When the size becomes smaller, return to the operation with the initially set working conditions
Means are provided.

[0005]

After turning on the power to the robot controller, the temperature around the robot manipulator is measured by the temperature sensor, and the result is compared with a reference value of the ambient temperature. If the ambient temperature is higher than the reference value, the operation is continued at the set operation condition speed. When it is lower than the reference value, the change width of the acceleration / deceleration time and the set speed is determined according to the magnitude of the difference from the reference value, and the operation is started at that value. If changed and operated, grease,
Since the oil temperature rises and the friction torque decreases, always monitor the motor generated torque after starting, and make it smaller than the generated torque reference value due to the temperature difference when this torque is changed. If it does, return to normal working conditions and continue operation.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be specifically described below with reference to embodiments. 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 to which the servomotor 12 is attached. 10a indicates that the temperature sensor is
b shows the case where the temperature sensor is attached to the robot mechanism, and 10c shows the case where the temperature sensor is attached to each axis of the servomotor or one of the axes. However, in any case, it is necessary to mount so that the ambient temperature can be measured instead of the temperature of the mounted portion. The control device 20 has a central processing unit (hereinafter referred to as a CPU) 1, and a memory 2 composed of a ROM, a memory 3 composed of a RAM, an axis control unit input / output interface 8 and the like are connected to the CPU 1 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 controller 6. The I / O interface 8 has an I / O for turning the servo amplifier 7 on and off.
An O signal circuit is provided. The temperature around the robot is measured by temperature sensors 10a, 10b, and 10c such as thermistors, and the measured values are converted into digital signals by an A / D converter 11 and input to the central processing unit 1 through an input / output interface 8. Next, this embodiment will be described with reference to the flowchart of FIG. When the power of the robot controller is turned on (step 100), the temperature around the robot is measured (step 110). The measured ambient temperature is compared with a reference value (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 temperature,
It is determined by the operating posture of the robot. Next, the change of the set speed is determined in the same manner as the change of the acceleration / deceleration time. A reference torque for returning to the normal operation is determined (step 130). Commands for the acceleration / deceleration time and the set speed after the setting change are given to the motor (step 140). At the same time, the contents of the change are displayed on a display device such as a CRT (step 150). Monitoring of the generated torque starts at a certain sampling time at the same time as the motor starts (step 1).
60). A comparison is made for each sampling time with the reference torque for returning to the normal operation determined at the time of setting change (step 170). If it is larger than the reference value, the operation is continued and operated in the changed state (step 140). If it is smaller than the reference value, the setting is returned to the change, and the display of the change is stopped at the same time as the operation is continued (step 180). If the peripheral temperature is higher than the reference value, the operation is performed at the set speed (step 180). When the power is turned on, the above loop is always 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, torque shortage due to an increase in friction torque does not occur. Start operation can be performed without stopping. In addition, when the friction torque decreases after the operation, the speed automatically returns to the initial set speed. Therefore, it is possible to cope with the increase in the friction torque at a low temperature without bothering the operator and increasing the motor frame.

[Brief description of the drawings]

FIG. 1 is a block diagram of an industrial robot embodying 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 an acceleration / deceleration time and a steady speed command of the present embodiment are changed.

FIG. 4 is an explanatory diagram showing an example of a 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 (1)

(57) [Claims] 1. A temperature sensor for measuring an ambient temperature of a robot before the start of operation, and, if the ambient temperature measured by the temperature sensor is lower than a reference value, the temperature sensor measures a difference between the ambient temperature and the reference value.
The acceleration / deceleration or speed of the motor that drives the robot.
In addition to providing a means for lowering the motor,
Monitor the torque and change the value to the changed acceleration / deceleration or speed.
If the value is smaller than the corresponding reference value,
Characterized by the provision of means for returning to operation under the specified working conditions.
Control device for industrial robots .