JPH06246674A - Method for detecting brake abnormality of industrical robot - Google Patents

Abstract

PURPOSE:To accurately diagnose abnormality by detecting a coasting distance, when a robot is emergency stopped, and judging a brake in abnormality, when this distance exceeds a reference distance, in the case of providing the electromagnetic brake in a drive motor of each axis. CONSTITUTION:An industrial robot, having a robot mechanism part 6 additionally provided with a servomotor, brake and a rotational speed detector 10, is driven to be controlled by a control unit 20. In the control unit 20, when an emergency stop command is turned on at the time of operation, the servomotor is stopped simultaneously transferred to stopping action of applying the brake. A coasting distance is started to be measured simultaneously with an emergency stop on-signal, and also a reference coasting distance is calculated, based on a rotational speed and attitude information during operation. The measured coasting distance is compared with the reference coasting distance, and in the case that the measured coasting distance is larger than the reference coasting distance, the brake is judged abnormal, to turn off a servo power supply to further perform an alarm process.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a brake abnormality detection method for an industrial robot having an electromagnetic brake in a drive motor for each axis.

[0002]

2. Description of the Related Art An electromagnetic brake that holds each axis of a robot is selected according to a robot-specific load capacity, a distance from a rotation center of the load capacity, a reduction ratio, efficiency, a safety factor, and the like. When actually installing and operating the selected electromagnetic brake, if the safety factor is low, the braking torque will decrease due to variations in the friction plate of the electromagnetic brake, aging, etc. Run). On the other hand, when a sufficient safety factor is taken, there is a problem that the braking torque at the time of stopping causes an excessive force to be applied to the frictional joint portion of the arm and the arm is displaced. Also, if a sufficient safety factor is taken, the brake will be large, and there will be problems with the size and economy of the drive system. Therefore, even if an optimum brake is selected in consideration of the above problems, the braking torque may decrease and the arm may drop due to variations in the friction plate, aging, and the like.

[0003]

In the current system,
There is no control method for the braking torque that causes the arm to fall, and there is a possibility that the arm may suddenly fall, which is a problem in terms of safety, damage to processed products, and reduction in production. Therefore, an object of the present invention is to provide a brake abnormality detection method in order to improve safety and reliability.

[0004]

According to a first aspect of the present invention, an emergency stop of the industrial robot is performed, a coasting distance until a stop is generated after a stop signal is generated, and the detected distance is preset. When the reference distance is exceeded, a brake abnormality signal is issued. A second aspect of the invention is, when the power is turned on, a reference value of the braking torque (torque required for holding x
Safety factor) is generated, and whether the motor is rotated or not is detected by a rotation detector or the like attached to the servomotor, and when the motor is rotated, a brake abnormality signal is issued.

[0005]

In the first aspect of the invention, the braking torque is estimated by comparing the coasting distance after the emergency stop signal is generated with the reference coasting distance. The reference coasting distance depends on the motor operating speed when the stop command is issued, the posture of the robot, or the weight of the workpiece actually gripped. It is better to change and compare. In the second aspect of the invention, it is always determined whether or not there is a brake abnormality when the power is turned on. In addition, depending on the brake abnormality signal,
Of course, it is possible to issue an alarm to the operator and stop the robot operation.

[0006]

EXAMPLES The present invention will be specifically described below with reference to 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, and 8 is a robot mechanism unit to which the servo motor 6 and the brake 7 are attached. The control device 20 has a central processing unit (hereinafter referred to as CPU) 1, and the CPU 1 has a memory 2 including a ROM,
A memory 3 including a RAM, an axis control unit 4, an input / output interface 9, and the like are connected by a data bus 12. A servo amplifier 5 for driving a servo motor 6 for each axis of the robot is connected to the axis controller 4. Also, the servo motor 6
The detection signal of the rotation detector 10 attached to is also fed back. The input / output interface 9 is provided with an I / O signal circuit for turning on / off the servo amplifier 5 and turning on / off the brake 7 attached to the robot mechanism section 8.

Next, an embodiment of the first invention will be described with reference to the flowchart of FIG. The robot power supply and the servo power supply are turned on, and the robot operation (200) such as jog operation or execution of an operation program is started. When the emergency stop command is turned on during operation (step 210), a dynamic brake is applied to the drive motor of each axis and a braking torque is generated by turning off the brake power supply to start the stop operation. At the same time as the emergency stop ON signal, coasting distance measurement (step 220) is started. Next, the reference coasting distance is calculated from the rotational speed and attitude information during driving (step 230). As shown in the explanatory view in FIG. 3, the area of the hatched portion of the graph with the rotation speed as the vertical axis and the time as the horizontal axis corresponds to the coasting distance. This distance is the number of detection pulses of the rotation detector 10 attached to the motor. In this calculation, it is better to consider the value for the dynamic brake. On the other hand, it is also conceivable to determine this reference coasting distance with a parameter and compare only when the rotation speed is a certain value or more. The reference coasting distance is determined with the above contents (step 240). The determined reference coasting distance and the measured coasting distance (the number of pulses, etc.) are compared (step 25).
0). If it is larger than the reference coasting distance, the servo power is turned off (step 260), and alarm processing and operation stop are started (270). When the coasting distance is small, the operation proceeds to the next step operation (280).

Next, the operation of the second embodiment of the invention will be described with reference to the flowchart of FIG. The robot power is turned on and the servo power is turned on (step 110). A command for generating a reference torque is turned on to each axis motor (step 130), and a reference torque is generated (step 140). The time to generate can be changed by parameter setting or the like (see FIG. 5). Check for motor rotation (step 15)
0). When the motor brake is rotated by the reference torque, the servo power is turned off (step 160), and alarm processing or operation stop processing (step 170) is performed. After the measurement, if the torque exceeds the reference torque and rotation is not recognized, the next step operation (step 180)
Go to.

[0009]

As described above, according to the present invention, it is possible to detect the abnormality of the brake by measuring the coasting distance of the brake attached to the robot, which reduces the braking torque. Based on this, it is possible to prevent the robot arm from falling accidents in advance, which can greatly contribute to the improvement of safety and reliability.

[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 first embodiment of the present invention.

FIG. 3 is an explanatory diagram of a coasting distance according to the first embodiment of the present invention.

FIG. 4 is a flowchart showing the operation of the second embodiment of the present invention.

FIG. 5 is an explanatory diagram of a reference torque according to the second embodiment of the present invention.

[Explanation of symbols]

 1 CPU 2 Memory (ROM) 3 Memory (RAM) 4 Axis Controller 5 Servo Amplifier 6 Servo Motor 7 Brake 8 Robot Mechanism 9 Input / Output Interface 10 Rotation Detector 20 Robot Controller

Claims (3)

[Claims] 1. An industrial robot having an electromagnetic brake in a drive motor for each axis, wherein the industrial robot is emergency stopped, and after a stop signal is generated,
A method for detecting a brake abnormality of an industrial robot, which detects a coasting distance until the vehicle stops, and issues a brake abnormality signal when the detected distance exceeds a preset reference distance. 2. The reference distance is changed according to the rotational speed of the drive motor before the generation of the stop signal or the operating posture of the industrial robot.
Brake abnormality detection method for the industrial robot described. 3. In an industrial robot having an electromagnetic brake in a drive motor for each axis, the drive motor for each axis of the robot is kept safe with a torque required to hold it while the brake for each axis is activated when the power is turned on. A brake abnormality detection method for an industrial robot, wherein a torque corresponding to a reference value of braking torque multiplied by a rate is generated, and a brake abnormality signal is generated when the motor rotates more than the reference value.