JPH0639066B2 - Control method for industrial robot - Google Patents

Description

The present invention relates to a method for controlling an industrial robot such as an articulated robot or a SCARA robot.

[Conventional technology]

It is difficult to determine the optimum angular acceleration during movement of each axis of an articulated robot used for transfer, assembly and the like. This is because the movement of each axis affects each other, so the required torque of each axis differs depending on the position of the start and end points of the arm movement, and it is extremely troublesome to analyze the required torque. This is because Therefore, in the conventional articulated robot, each acceleration of each axis is suppressed to a low level.

[Problems to be solved by the invention]

As described above, since the maximum value of the angular acceleration of each axis of the articulated robot is kept low, there is a problem that the movement time of the arm becomes long on average.

Therefore, an object of the present invention is to provide a method for controlling an industrial robot that does not require complicated motion analysis and shortens the moving time.

[Means for solving problems]

The present invention is a method for controlling an industrial robot having a plurality of axes for rotating a plurality of arms 2 and 6, respectively. In the method, the plurality of arms 2 and 6 are actually operated, and the torque of the plurality of axes is measured as a current value. Step 22, and the current values of the plurality of axes are all lower than the allowable current value, and the current value of any one of the plurality of axes is set to a value substantially equal to the allowable current value. This is a method of controlling an industrial robot, characterized in that the teaching data is corrected by steps 23, 24, 25, 26, 27 for changing the value of the angular acceleration.

[Action]

The shaft torque is proportional to the current value. Therefore, if the current value is increased within a range in which none of the current values related to the plurality of axes exceeds the allowable current value, the angular acceleration of each axis can be increased without the need for complicated motion analysis. . As a result, the traveling time can be shortened.

〔Example〕

 An embodiment of the present invention will be described below.

FIG. 1 shows an example of an industrial robot such as a SCARA type robot to which the present invention can be applied.

In this robot, a base portion of a first arm 2 is rotatably supported on a base portion 1, and a drive portion 5 composed of a servo motor 3 and a speed reducer 4 arranged on the base portion 1 causes a first arm to move. The second shaft is rotated. A second arm 6 is rotatably supported at the tip of the first arm 2. First arm 2
A shaft of the second arm 6 is rotated by a drive unit 9 including a servo motor 7 and a speed reducer 8 arranged on the tip of the.
The hand 10 is attached to the tip of the second arm 6. In the SCARA type robot, both the first arm 2 and the second arm 6 move on the (XY) plane.

As the servo motors 3 and 7, a DC servo motor or A
A C servo motor is used. FIG. 2 shows an example of the configuration of the servo circuits of the servomotors 3 and 7.

In FIG. 2, reference numeral 11 indicates a microcomputer.
The microcomputer 11 supplies a speed command 13 and a direction command 14 to a speed program circuit 12 according to a program for operation control. Speed program circuit 12
Forms an acceleration / deceleration curve based on a command from the microcomputer 11. The output signal of the speed program circuit 12 is supplied to the SERVOPACK 15. The speed signal from the speed detector 16 and the position signal from the position detector 17 are fed back and supplied to the servo pack 15.

In the servo pack 15, the servo motor 18 is controlled by the feedback detection signal so that the arm moves along a predetermined acceleration / deceleration curve. FIG. 3 shows an example of the acceleration / deceleration curve.

In FIG. 3, points A to B are constant acceleration sections, points B to C are constant velocity sections, and points C to D are constant acceleration sections. By this speed control from point A to point D, the axis is moved to the vicinity of the target point, and the positioning operation is switched from point D. Then, at the point E, the target position is reached. Therefore, the time from point A to point E is the travel time.

The configuration shown in FIG. 2 is provided for each of the servomotor 3 or the servomotor 7 of the industrial robot shown in FIG. In this case, of the axes of the arms 2 and 6, the speed of the other axis is adjusted to that of the other axis, so that the two axes are synchronized.

Further, teaching data is stored in the memory of the microcomputer 11. This teaching data relates to the order, position, and time of movement of the robot. The teaching data is read out, the position, speed, acceleration, etc. of each axis are calculated by the microcomputer 11, and the speed command 13 and the direction command 14 are output to the speed program circuit 12.

In this embodiment, the data relating to the angular acceleration of the teaching data is corrected by measuring the current value of the servo motor 18. The torque of the servomotor 18, that is, the shaft, is proportional to the current value. FIG. 4 is a flow chart showing the operation in the case of this correction.

First, the robot is actually operated (step 21).
At this time, the current value of each axis (current of the servo motor as the drive source of each axis) is measured (step 22). It is checked whether or not the current value of each axis is less than or equal to the allowable current value (that is, the maximum current value that can be used) (step 23). If the current value of each axis is equal to or less than the allowable current value, it is checked whether there is an axis having, for example, 95% or more of the allowable current value (step 24). If there is such an axis, the teaching cannot be completed because the angular acceleration cannot be further increased.

95% of the allowable current value when the current value of each axis is less than the allowable current value
When there is no axis above, the value of the allowable angular acceleration of each axis is improved by, for example, about 5% (step 25). The acceleration and velocity of each axis are determined so that each axis operates synchronously (step 26). If all the axes are not equal to or less than the permissible current value in step 23, the permissible angular acceleration value of each axis is decreased by, for example, 3% (step 27), and the process proceeds to step 26. Then, the process returns from step 26 to step 21, and the actual movement operation is executed. Hereinafter, the same operation as described above is repeated.

It should be noted that the judgment as to whether the current is less than or equal to the allowable current value is not limited to the method in which a person observes the measured value, but the detected current is converted into a voltage, and the detected voltage and the reference voltage (corresponding to the allowable current value However, the above correction operation may be automatically performed according to the result of this comparison.

[Advantages of the Invention] According to the present invention, the optimum angular acceleration of each arm of an articulated robot can be set without performing complicated motion analysis, and the movement time of the arm can be shortened.

[Brief description of drawings]

FIG. 1 is a front view of an example of an industrial robot to which the present invention can be applied, FIG. 2 is a block diagram of an example of a servo circuit to which the present invention can be applied, and FIG. 3 shows an acceleration / deceleration curve. A schematic diagram and FIG. 4 are flowcharts used for explaining the present invention. Description of main symbols in the drawings 2: First arm, 3, 7: Servo motor, 4, 8: Reducer, 6: Second arm.

Claims (1)

[Claims] 1. A method for controlling an industrial robot having a plurality of axes for respectively rotating a plurality of arms, wherein the plurality of arms are actually operated, the plurality of axis torques are measured as current values, and the measurement is performed. The current value is converted into a voltage, the voltage is compared with a reference voltage corresponding to the allowable current value, and based on the comparison result, all the current values of the plurality of axes are lower than the allowable current value, and The value of the angular acceleration of the plurality of axes is increased until the current value of any one of the plurality of axes becomes substantially equal to the allowable current value, and the teaching data is corrected with the angular acceleration. A method for controlling an industrial robot, which is characterized by performing.