JP2852772B2 - Robot acceleration / deceleration control method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial application field) The present invention performs acceleration / deceleration by sending a speed command to a servo system for driving a robot at predetermined unit time intervals when the robot moves from point to point. The present invention relates to an acceleration / deceleration control method for a robot.

(Conventional technology) Conventionally, acceleration / deceleration control includes a constant time method in which the acceleration / deceleration time is fixed and the peak speed is adjusted in accordance with the moving distance from point to point, and the acceleration / deceleration time is controlled by setting the acceleration constant. There is a constant acceleration method that adjusts according to

The constant time method takes more time than necessary in a section where the moving distance is short. Therefore, recently, acceleration and deceleration are often performed by the constant acceleration method.

In the constant acceleration method, a moving distance when accelerating at a predetermined constant acceleration and decelerating so that the peak speed becomes a predetermined upper limit speed is Ls, and a moving distance from point to point is L, and L>
In the case of Ls, the vehicle is accelerated to the upper limit speed, then moves at a predetermined distance (L-Ls) at this speed and then decelerates. Then, it slows down at L / 2 in the latter half.

FIG. 5 shows the target pattern of the acceleration / deceleration control in the case of L ≦ Ls by a dotted line. Since the speed command is output at unit time intervals as shown by the solid line in FIG.
May not match the output time of the speed command,
In this case, deceleration is started at the time of output of the speed command immediately before Ts, and the moving distance is insufficient if this is the case. Processing is performed.

(Problems to be Solved by the Invention) In the above, when the movement time from point to point is prolonged due to the creep processing, and the robot is moved to many points,
The accumulated time required for the creep processing becomes so long as to be negligible, which is a problem in improving efficiency.

In view of the above, an object of the present invention is to provide a control method for accelerating and decelerating a robot so that the robot can move to a target point without performing creep processing.

(Means for Solving the Problems) In order to achieve the above object, according to the present invention, when a robot moves from point to point, a speed command is sent to a servo system for driving the robot at predetermined unit time intervals to accelerate or decelerate. In what is performed, the moving distance when accelerating at a predetermined constant acceleration and decelerating so that the peak speed becomes the predetermined upper limit speed is the standard distance, the actual moving distance from point to point is the actual distance, and the actual distance is When shorter than the standard distance, the time required to accelerate from the stop state at the predetermined constant acceleration and move by half the actual distance and the speed at that time are obtained, and these are set as the target time and the target peak speed, respectively. The target time is fractionally processed so as to be an integral multiple of the unit time and set to the real time of each of acceleration and deceleration, and the product of the target time and the target peak speed is divided by the real time. Real value As the peak speed, a speed command for accelerating and decelerating the actual peak speed by real-time acceleration and deceleration is issued.

(Operation) The moving distance when accelerating and decelerating at the target peak speed during acceleration and deceleration at the target time is equal to the product of the target time and the target peak speed, which is equal to the moving distance from point to point.

The target time is rounded and replaced with an integral multiple of the unit time, and this time, that is, real-time acceleration and deceleration is performed by
The point is to start deceleration at the output time of the speed command immediately before Ts, which is the target time.The actual acceleration / deceleration peak speed, that is, the actual peak speed, is the product of the target time and the target peak speed in real time. If the acceleration and deceleration of the actual peak speed are performed by real-time acceleration and deceleration to set the divided value, the moving distance is equal to the product of the target speed and the target peak speed, that is, the moving distance from point to point, The robot can be accurately moved and stopped at the target point only by acceleration / deceleration.

(Embodiment) Referring to FIG. 1, (1) is a sequencer, (2) is a robot controller composed of a microcomputer, and a few msec from the robot controller (2) by a start signal from the sequencer (1). A speed command is sent to the servo circuit (3) at intervals of the unit time t, and the servomotor (4) for driving the robot is driven at the command speed so that the robot moves from a point where teaching has been performed in advance to a point.

The memory in the robot controller (2) stores a position data table of each moving point of the taught robot and a data table of the standard acceleration pattern shown in FIG. When moving to a point, the robot controller (2) first performs an operation plan calculation, and outputs a speed command according to the operation plan.

The standard acceleration pattern is a pattern when the robot is accelerated from a stopped state to a predetermined upper limit speed Vm at a predetermined constant acceleration, and is stored in the memory as speed data for each unit time t. This pattern is Vm when time is reversed
From this, a deceleration pattern when decelerating at the above acceleration is obtained.
The processing procedure of the operation plan calculation is as shown in FIG. 2. In the first step, the position data of the current point detected by the encoder (5) of the servomotor (4) and the next point read from the position data table are read. The travel distance (actual distance) L from the current point to the next point is calculated using the position data of
The moving distance (standard distance) Ls when decelerating after accelerating to Vm is obtained by multiplying the upper limit speed Vm by the time Tm at which the upper limit speed Vm is reached,
The actual distance L and the standard distance Ls are compared in the step (1).

In the case of L> Ls, it is necessary to accelerate to Vm, then move at a constant speed at Vm for a predetermined time, and then decelerate. When L> Ls,
Calculate the distance Lc (= L−Ls) of moving at a constant speed in the step, and calculate the time Tc (= Lc / V) of moving at a constant speed in the step
m), and acceleration, constant speed movement, and deceleration are performed based on the calculation result.

In the case of L ≦ Ls, the process proceeds from the step to the step (a), the time (target time) Ts required for accelerating according to the standard acceleration pattern and moving by half of the actual distance, and the speed (target peak speed) Vs at that time. Is given by In the next step, the actual time Tn of acceleration and deceleration is determined by performing a fraction process on the target time Ts so as to be an integral multiple of the unit time t. Specifically, the real time Tn is calculated by multiplying the value obtained by dividing the target time Ts by the unit time t and rounding down the decimal point or less to the unit time t.

In the next step, the actual acceleration / deceleration peak speed (actual peak speed) Vn is calculated by the following equation. Is calculated by Then, a speed command is output as shown by a solid line in FIG. 4 so that acceleration and deceleration of Vn by acceleration and deceleration for the time Tn, that is, acceleration and deceleration in a dashed line pattern in FIG.

The distance traveled by this acceleration / deceleration is Vn × Tn, which is equal to Vs × Ts.
Just move and stop at the next point.

(Effects of the Invention) As is apparent from the above description, according to the present invention, the robot can be moved to the target point without performing creep processing only by acceleration / deceleration, and a loss time such as creep processing does not occur. It has the effect of improving work efficiency.

[Brief description of the drawings]

FIG. 1 is a block diagram of a control device used for carrying out the method of the present invention, FIG. 2 is a flowchart showing a processing procedure of an operation plan calculation according to the present invention, FIG. 3 is a diagram showing a standard acceleration pattern, and FIG. Is a diagram showing output characteristics of a speed command according to the present invention, and FIG. 5 is a diagram showing output characteristics of a conventional speed command. (2) Robot controller (3) Servo circuit (4) Servo motor Vm Upper limit speed, Ts Target time Vs Target peak speed Tn Real time Vn Actual peak speed

Claims (1)

(57) [Claims] When a robot moves from point to point, a speed command is sent to a servo system for driving the robot at predetermined unit time intervals to perform acceleration / deceleration, so that a peak speed becomes a predetermined upper limit speed. The moving distance when accelerating and decelerating at a predetermined constant acceleration is the standard distance, the actual moving distance from point to point is the actual distance, and when the actual distance is shorter than the standard distance, the predetermined constant The time required to move by half of the actual distance by accelerating with acceleration and the speed at that time are obtained, and these are set as a target time and a target peak speed, respectively, so that the target time is an integral multiple of the unit time. In addition to setting the actual time for acceleration and deceleration to the real time, the product of the target time and the target peak speed is divided by the real time to obtain this value as the actual peak speed. Actual peak speed Deceleration control method for a robot is characterized in that so as to issue a speed command to perform minute deceleration.