JPH0490007A - Conveyor following-up method for industrial robot - Google Patents

Abstract

PURPOSE:To keep the relative position precision between a conveyor and a robot with an inexpensive constitution regardless of the fluctuation of the conveyor speed by performing operation for shifting robot position data of the robot before reproducing operation and determining the reproducing speed of the robot based on the present position of the conveyor and stored data. CONSTITUTION:The position of a conveyor 3 is each step to which it will be moved at a speed as the reference speed is obtained based on this speed and a required time in each step for reproducing to preliminarily store position data of a robot 1 and the conveyor 3 in each step. The present position and the movement speed of the conveyor 3 are obtained at the time of reproducing, and the reproducing time required for arrival of the conveyor 3 at the position determined by position data is calculated in accordance with these obtained values and position data of the conveyor 3, and the movement speed of the robot 1 is so controlled that this reproducing time is equal to the time required for reproducing of the robot in the step. Thus, the precision of the relative position between the conveyor 3 and the robot 1 is kept regardless of the fluctuation of the movement speed of the conveyor 3, and a controller is made inexpensive.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a conveyor tracking method for an industrial robot that performs work by following a workpiece conveyed by a continuously moving conveyor.

[Prior Art] Conventionally, in a robot such as a painting robot that works on a workpiece that is conveyed by a continuously moving conveyor, the position data of the robot and the conveyor is transmitted while the conveyor is stopped during teaching. It is characterized by being stored as step data and being played back in time with the movement of the conveyor. Here, the tracking method during playback is as follows:
There are three main methods:

(A): 7 By fixing the speed of the conveyor and giving the robot parameters, find the conveyor position for each step, and calculate the robot's position by the difference between the conveyor position and the conveyor position obtained at the time of teaching. Shift and correct position data and store.

In this case, at the time of reproduction, only the above position data is reproduced.

(B) The position data of the robot is shifted in accordance with a preset conveyor speed, and the shifted position data is reproduced at the time of reproduction. The method up to this point is the same as method (A), but in addition, during playback, the actual speed of the conveyor is detected and the speed of the robot is changed according to that value, thereby improving the relative position accuracy between the conveyor and the robot. That's what it's like. In this case, the robot's playback speed can be found as follows.

(C) Unlike the methods (A) and (B) above, the position data of the robot is not shifted, but the position data of each step is shifted and regenerated during the regeneration operation. Therefore, during regeneration operation, the position of the conveyor is always detected, the difference between the conveyor position data and the conveyor position data obtained during teaching is determined as the shift amount, and the robot position data is shifted based on this shift amount. to play. Note that if the current conveyor position is used as data for calculating the shift amount, there will be a delay during playback, so the shift amount may be determined by estimating the conveyor position at the time of step playback from the conveyor speed.

[Problems to be Solved by the Invention] By the way, the speed of the conveyor that conveys the work to be worked on is not always constant; for example, it may constantly fluctuate due to changes in production volume, variations in the structure of the conveyor, etc. Conceivable. Therefore, in a system that does not operate in accordance with the movement of the conveyor during regeneration, as in method (A) described above, a tracking error always occurs. Furthermore, if the speed of the conveyor is artificially changed in response to changes in production volume, etc., it is necessary to create the data again.

Although the method (B) takes into consideration the problem of (A), it still has a factor that causes a tracking error. in general,
Servo control is controlled by a computer, and the actual speed is controlled by managing the amount of movement at regular intervals.

This situation is shown in FIG. If the movement stroke of a certain step is represented by Δt, which is the cycle of 81 servo control, then the playback time T of the step is divided by Δt, divided into n parts, and the axis of the robot is moved by interpolating S/n for each cycle. Therefore, the speed of the robot axis is determined by the value of S/n, and the time T required to reproduce a step is determined by the value of n.

On the other hand, the robot's playback speed formula is as described above, and this can be rewritten as follows, where the playback time determined at the time of teaching is taken as the step playback time at TO1 playback. Therefore, if we set TO-no・Δt and T-n・Δt, we get the following. Here, n and no are integers. However, the ratio of ecstatic conveyors is generally not an integer. Therefore, the fraction of the calculated value of n appears as an error in the reproduction time T, in other words, the difference between the speed required for the robot to follow and the actual speed. This directly results in misalignment between the conveyor and the robot. Therefore, with this method, relative positional accuracy between the conveyor and the robot cannot be maintained.

In method (C), calculation errors can be eliminated, but since complex calculations are processed while the robot is moving, the load on the computer increases. For this reason, the control device becomes expensive, and there is a limit to the computer load when reducing T shown in Figure 3, and as a result, there is a limit to the tracking ability when the conveyor speed increases. .

The present invention has been made in view of the above-mentioned points, and provides a high-precision conveyor tracking method for an industrial robot that can maintain relative positional accuracy between the conveyor and the robot even when the speed of the conveyor fluctuates, with an inexpensive configuration. The purpose is to provide

[Means and Effects for Solving the Problems] That is, the present invention is applicable to industrial applications in which the playback speed is changed in accordance with the movement of a continuously moving conveyor, and work is performed by following the workpiece conveyed by the conveyor. In the method for following a conveyor of a robot, position data of the robot and the conveyor is stored in advance for each step, and the current position and moving speed of the conveyor are determined at the time of reproduction;
From these values and the position data of the conveyor, calculate the playback time until the conveyor reaches the position determined by the position data, and make this playback time the time required for the robot to play the step in question. The present invention is characterized in that the moving speed of the robot is controlled.

As a result, even if the moving speed of the conveyor changes, the relative position accuracy between the conveyor and the robot can be maintained, and a highly accurate robot system can be realized.

[Example] Hereinafter, a method for following a conveyor for an industrial robot according to an example of the present invention will be described with reference to the drawings.

First, the conveyor following method of the present invention will be explained with reference to FIG.

In the present invention, the following improvements are made to the method (B) described above, thereby improving the tracking accuracy without increasing the price. That is, the playback time T of the step
It is characterized by defining... (1) as follows. Here, Tf is the reproduction time of the previous step. Referring to FIG. 2, CDD, CDI, CD2. CD3... is conveyor position data stored in advance for each step, Co, C1, C2... is actual conveyor position data at the end of each step, To, Tl, T2... is This is the step playback time. Here, according to the above equation (1), the reproduction time TI of the second step is determined as follows. As a result, assuming that the conveyor moves at the same speed as in the previous step, the speed of the robot (-reproduction time) is controlled so that the relative relationship between the conveyor and the robot matches at the end of the second step. FIG. 2 shows a state in which the speed of the conveyor has changed again, and in the third step, it is determined that the reproducing time is shortened.

Next, a detailed explanation will be given with reference to FIG.

FIG. 1 is a diagram showing the system configuration of an industrial robot that performs work on workpieces conveyed by a continuous conveyor.

A control device 8 is connected to the robot body 1. In this control device 8, 13 is a reversible counter or A/D converter that obtains position data for each axis of the robot, 14 is an amplifier that supplies power to the motor according to the deviation between the position data and the target position, and 10 11 is a storage device, 12 is an operation panel, and 15 is a calculation unit.

9 is a reversible counter for detecting the position of the conveyor 3, which counts the pulses generated by the encoder 6;
It is reset by the sensor 7 that detects the workpiece 16.

This sensor 7 is also used as a start signal for the robot during regeneration operation. 5 is a conveyor drive motor, and 4 is a motor control panel.

During teaching, the conveyor 3 is stopped at an arbitrary position and the teaching work is performed, and the value of the reversible counter 13 is stored as the position data of the robot body 1, and the value of the reversible counter 9 is simultaneously stored in the storage device 11 as the position data of the conveyor 3. do.

In such a configuration, first, after creating data such as the moving position, order, speed, etc. of the robot body 1, the speed of the conveyor 3, which is the standard input in the parameters, and the time required for each step during playback are used to determine the speed of the conveyor 3. The position of the conveyor 3 at each step when the conveyor 3 moves at the above speed is determined, and the position of the robot body 1 is determined so as not to destroy the relative relationship between the conveyor 3 and the robot body 1 obtained at the time of teaching. As a result, the position data of the robot body 1 and the conveyor 3 for each step is corrected and stored.

Note that these series of processes are performed through the operation panel 12 according to procedures whose descriptions are omitted. The corrected data is calculated by the central processing unit 10 and the arithmetic unit 15 and then stored in the storage device 11.

During playback, the current position of the conveyor 3 is detected by the encoder 6, and the playback time up to the next step is determined from this data and the position data for each step obtained from the reference moving speed of the conveyor 3, and the playback time is determined by the robot. The moving speed of the robot body 1 is determined so that the time required for regeneration of the robot body 1 is achieved.

Thereby, the relative position accuracy between the conveyor 3 and the robot body 1 can be maintained.

[Effects of the Invention] As described above, the present invention provides the following effects.

(1) Since complex calculations for shifting the robot's position data are performed before the regeneration operation, high processing speed is not required. Therefore, the control device becomes inexpensive. Furthermore, the speed of the conveyor becomes faster than the parameter speed at the time of teaching, so that it can be handled.

(2) During regeneration operation, the robot's regeneration speed (-regeneration time) is always determined from the current position of the conveyor and the stored data, so even if the conveyor speed changes, the relative position between the conveyor and the robot remains unchanged. Stays in place.

[Brief explanation of the drawing]

Fig. 1 is a diagram showing the configuration of a robot system according to an embodiment of the present invention, Fig. 2 is a diagram for explaining the conveyor following method of the present invention, and Fig. 3 is a diagram for explaining the conventional conveyor following method. This is a diagram. DESCRIPTION OF SYMBOLS 1... Robot body, 3... Conveyor, 8... Control device, 10... Central processing unit, 11... Storage device,] 2... Operation panel. Applicant's representative Patent attorney Takehiko Suzue Figure 1 Figure 2 Procedural amendments dated 2.11/1998

Claims (1)

[Claims] In a conveyor following method for an industrial robot, the playback speed is changed in accordance with the movement of a continuously moving conveyor, and the work is performed by following a workpiece conveyed by the conveyor. has position data of the robot and the conveyor stored in the robot, calculates the current position and moving speed of the conveyor at the time of playback, and determines that the conveyor is determined by the position data from these values and the position data of the conveyor. Calculate the playback time until reaching the position,
A method of following a conveyor for an industrial robot, characterized in that the moving speed of the robot is controlled so that the regeneration time is the time required for the robot to regenerate the step.