JPH03164813A - Acceleration/deceleration control method for robot or the like - Google Patents

Abstract

PURPOSE:To reduce the oscillation of a control object at the time of deceleration and stop by controlling acceleration/deceleration in accordance with a prescibed acceleration/deceleration pattern selected in accordance with relations between the natural oscillation period of the control object and a set time. CONSTITUTION:Position data of plural target positions where a robot is moved in order and plural kinds of acceleration/deceleration patterns, for example, acceleration/ deceleration patterns to fix the acceleration and acceleration/deceleration patterns to change the acceleration like sine waves are stored in the memory of a robot controller 2, and the robot controller 2 calculates the distance of movement L and an acceleration/deceleration time T (the time from the start of acceleration to the end of deceleration) based on the data of the present stop position detected by an encoder 5 and the next target position and selects an acceleration/deceleration pattern in accordance with the acceleration/deceleration time T and compresses or expands the selected acceleration/deceleration pattern in directions of the time base and the speed base for the purpose of moving the robot for the length L in the acceleration/ deceleration time T and outputs a speed command according with the processed acceleration/deceleration pattern to accelerate/decelerate the robot. Thus, the oscillation of the control object is reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an acceleration/deceleration control method for a robot, etc., in which a controlled object, such as a robot arm, is accelerated or decelerated to move to a target position.

(Prior art) When moving a controlled object to a target position by accelerating it in the first half and decelerating it in the second half, an excitation force with one cycle from the start of acceleration to the end of deceleration acts on the controlled object, causing it to vibrate and decelerate. Positioning accuracy when stopped becomes poor.

Conventionally, according to Japanese Patent Publication No. 60-29121, when accelerating or decelerating at a constant acceleration, each time of acceleration and deceleration is set to a time that is an integral multiple of the natural vibration period of the controlled object, and the end point of acceleration or deceleration is set. A device designed to prevent vibrations is known, but in this device, if the natural vibration period of the controlled object is, for example, 1001 seconds, the acceleration/deceleration time is 25 seconds.
Even if it can be set to 0asec, it must be set to 300m5ec, and in a welding robot that moves to a large number of dot positions in one cycle of operation, the cycle time becomes significantly longer and efficiency deteriorates.

(Problems to be Solved by the Invention) The present invention provides an acceleration/deceleration system that can reduce the vibration of a controlled object during deceleration and stop even if the acceleration/deceleration time is set independently of the natural vibration period of the controlled object. Its purpose is to provide a control method.

(Means for Solving the Problems) In order to achieve the above object, the present invention moves a controlled object to a target position by accelerating and decelerating a set time determined according to the moving distance. Acceleration/deceleration is performed according to a predetermined acceleration/deceleration pattern selected from the acceleration/deceleration patterns according to the relationship between the natural vibration period of the controlled object and the set time.

(Function) When comparing an acceleration/deceleration pattern, for example, a pattern in which the acceleration is constant and a pattern in which the acceleration changes in a sinusoidal manner, the magnitude of the vibration that remains at the time of deceleration and stop is determined by the acceleration/deceleration setting time T and the controlled object. The ratio of the natural vibration period of ■ o (T/
T. ), when T/T is small, the constant acceleration pattern is smaller, and T/T. When becomes large, the sine wave pattern becomes smaller.

Therefore, when moving the controlled object sequentially through multiple movement sections, it is possible to select the acceleration/deceleration pattern that reduces vibration based on the acceleration/deceleration setting time determined according to the movement distance of each movement section. , vibration of the controlled object during deceleration and stop can be reduced.

(Example) Referring to FIG. 1, (1) is a sequencer, (2) is a robot controller consisting of a microcomputer, and a servo circuit (3) is connected to the robot controller (2) by a start signal from sequence (1). ) outputs a speed command at a time interval of about 5 (3e), and outputs a speed command to the servo motor (4).
The first half is accelerated operation, the second half is decelerated operation, and the motor (4
) to move a controlled object such as a robot arm to a target position.

The memory of the robot controller (2) stores position data of a plurality of target positions to which the robot should be sequentially moved, and a plurality of types of acceleration/deceleration patterns, such as the acceleration/deceleration pattern with constant acceleration shown in FIG. The robot controller (or encoder (5)) stores an acceleration/deceleration pattern in which the acceleration changes in a sinusoidal manner as shown in Figure 2(b).
The travel distance and the corresponding acceleration/deceleration time T (time from the start of acceleration to the end of deceleration) are calculated from the data of the current stop position and the next target position detected by Accordingly, as described later, an acceleration/deceleration pattern is selected, and the selected acceleration/deceleration pattern is compressed and expanded in the time axis direction and velocity axis direction so that the object moves by the distance by acceleration/deceleration of time T. It functions to perform acceleration/deceleration by outputting a speed command according to an acceleration/deceleration pattern.

Here, the natural vibration period T0 of the controlled object and the acceleration/deceleration time T
When the ratio between n (-T/Tn) and the change in the vibration waveform of the controlled object due to the change in n were investigated using computer simulation, it was found that in the constant acceleration pattern, Figure 3 (a)
) (b) (c) (d), and the sine wave pattern was as shown in Fig. 4 (a) (b) (c) (d).

The thick lines in the figure indicate acceleration, and the absolute values of acceleration in the image pattern are set so that the moving distances are equal to each other. However, it depends on the type of robot. is approximately 50~
200m5ec s Acceleration/deceleration time is 100~400m5e
c, and n ranges from 0.5 to 8.

As can be seen by comparing Figures 3 and 4, the amplitude of the # object remaining during deceleration and stop is generally smaller in the constant acceleration pattern when n is 2.4 or less, and when n is 2.8 Above that, the sine wave pattern becomes smaller.

Therefore, when the acceleration/deceleration time T is 2.5XTo or less, the constant acceleration pattern is selected, and when it is longer than that, the sine wave pattern is selected.

In addition, although the vibration is attenuated gently in Figures 3 and 4,
In reality, vibrations are attenuated to a greater extent due to friction and the like.

In the above, we have explained the case where the acceleration/deceleration pattern is a type 2a pattern consisting of a constant acceleration pattern and a sine wave pattern. If these are used very carefully, vibrations during deceleration and stop can be further reduced.

(Effects of the Invention) As is clear from the above description, according to the present invention, even if the acceleration/deceleration time is set as short as possible depending on the travel distance,
Based on the relationship between the acceleration/deceleration time and the natural vibration period of the controlled object, it is possible to select an acceleration/deceleration pattern from among multiple acceleration/deceleration patterns that reduces the vibration of the controlled object when it decelerates and stops. This has the effect of preventing deterioration of positioning accuracy due to vibration of objects and improving efficiency.

[Brief explanation of the drawing]

Figure 1 is a block circuit diagram of the control system of the robot used to implement the present invention, Figures 2 (a) and (b) are diagrams showing acceleration and deceleration patterns, respectively, and Figure 3 (a), (b), and (C). (d)
and Figure 4 (a), (b), (c), and (d) are lines obtained for each acceleration/deceleration pattern of changes in the vibration waveform of the controlled object due to changes in the ratio of the acceleration/deceleration time and the natural vibration period of the controlled object. It is a diagram. Figure 1 (5 Figure 2 8 Hitoshi Tsuboma)

Claims (1)

[Claims] In a device that moves a controlled object to a target position by accelerating and decelerating a set time determined according to a moving distance, the relationship between the natural vibration period of the controlled object and the set time from among a plurality of different acceleration/deceleration patterns. 1. A method for controlling acceleration/deceleration of a robot, etc., characterized in that acceleration/deceleration is performed according to a predetermined acceleration/deceleration pattern selected in accordance with a predetermined acceleration/deceleration pattern.