JPH03152605A - Acceleration/deceleration control method for robot - Google Patents

Abstract

PURPOSE:To precisely transfer a robot to a target position by storing previously an acceleration/deceleration pattern as a table of position data and controlling the acceleration/deceleration based on the position data. CONSTITUTION:A standard pattern of acceleration/deceleration is stored as a table to show the position changes to the time. This table is produced with use of a personal computer, and the address numbers of start and end points of a position conversion pattern are sampled at a prescribed interval. A robot controller performs the control operations of a time axis and a position axis in accordance with the data on the table and the actual acceleration/ deceleration. Thus the robot controller obtains the position change data in response to the actual acceleration/deceleration and computes the speed command value from the position change data to control the acceleration/ deceleration. In such a constitution, various kinds of acceleration/deceleration can be controlled via a common table and therefore the storage capacity can be reduced. Then no cumulative error is produced for the fractions that are neglected at operation of the transferred distance of a robot. At the same time, the accurate control is attained for the acceleration/deceleration and the position precision of the robot is improved in terms of the moving locus of the robot.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a robot acceleration/deceleration control method that controls acceleration/deceleration by sending a speed command to a servo system that drives the robot.

(Prior art) Conventionally, as this type of control method, Japanese Patent Application Laid-Open No. 81-2844
According to Publication No. 07, a standard acceleration/deceleration pattern is stored using relative values of time and speed as parameters, and this acceleration/deceleration pattern is subjected to adjustment calculations in the time axis direction that match the actual acceleration/deceleration times. It is known that acceleration/deceleration control is performed by performing adjustment calculations in the speed axis direction in accordance with a target speed, and compressing and expanding a standard acceleration/deceleration pattern in accordance with actual acceleration/deceleration.

(Problem to be Solved by the Invention) When performing adjustment calculations in the time axis direction or speed axis direction as described above, the calculation result is produced by ignoring fractions that cannot be handled as data in digital processing by a computer, and based on this, the calculation result is ignored. Acceleration/deceleration control must be performed.

In this case, even if the speed itself reaches the target speed due to acceleration and deceleration, an error occurs in the moving distance due to the accumulation of ignored fractions, and the positional accuracy regarding the robot's moving trajectory deteriorates.

In view of the above points, it is an object of the present invention to provide a control method that can improve position accuracy by performing acceleration/deceleration control based on position data.

(Means for Solving the Problems) In order to achieve the above object, the present invention provides a method for controlling acceleration/deceleration by sending speed commands to a servo system that drives a robot, based on a standard acceleration/deceleration pattern. Find the position change pattern for , sample the position data from the starting point to the end point of this change pattern at regular intervals in the time axis direction, store the acceleration/deceleration pattern as a table of these position data, and apply the data to this table data. , performs adjustment calculations in the time axis direction to match the actual acceleration/deceleration time, and performs adjustment calculations in the position axis direction to match the target position, and from the position change data corresponding to the actual acceleration/deceleration determined by these calculations. The speed command value is calculated and output to the servo system.

(Function) Since the acceleration/deceleration pattern is stored as a table of position data, acceleration/deceleration control is performed so that the position becomes a predetermined value as a result, and fractions are ignored in adjustment calculations in the time axis direction and position axis direction. Even if the calculation result is output and acceleration/deceleration control is performed based on the result, there will be no cumulative error due to ignored fractions in the robot's travel distance, the robot will move accurately to the target position, and the position accuracy regarding the robot's travel trajectory will be improved. will improve.

(Example) FIG. 1 shows changes in speed when the robot moves from point to point. In the figure, A is an acceleration section, B is a constant speed section, and C is a deceleration section.The speed of the constant speed section and the travel distance and time of the acceleration/deceleration section are determined based on the travel distance between two points and the required travel time. is determined.

In this embodiment, the standard acceleration/deceleration pattern is a sine curve, and the position change pattern with respect to time corresponding to this pattern is as shown in the second diagram, and the position data from the start point to the end point of this change pattern is sampled at regular intervals in the time axis direction, and an address number n according to the flow of time is attached to these position data to create a table, which is stored in the memory of the robot controller.

The table is created using a personal computer, and the actual number of samples is very large, but to simplify the explanation, the address numbers n of the starting point and ending point of the position change pattern are set to 0 and 10, respectively. The following explanation assumes that 11 pieces of position data were sampled and data as shown in the table below was created.

Note that the sampling interval of the position data is set to match the cycle time required for the robot controller to issue one speed command to the next speed command, which is, for example, 301 seconds.

Here, the acceleration control is performed such that the acceleration time is 210 ssec.
Considering the case where the movement distance in the acceleration section (target position) is 100, first an adjustment calculation is performed to compress the length of the table data in the time axis direction to 210 m5ec, and then the length in the position axis direction is reduced to 100 m. Perform adjustment calculations to compress the data into .

To explain this in more detail with reference to Figure 3, when performing adjustment calculations in the time axis direction, the number of speed commands to be performed within the acceleration time is determined, and based on this number of times, the final address number is specified from the table at equal intervals. Pick up the location data up to (■). In the example, the number of speed commands is 210/30, which is 7 times, the interval between address numbers to be picked up is 10/7, and the address number nl to be picked up is 101/30, with the picking order being i.
It becomes 9.

If this address number n+ has a fraction below the decimal point, interpolation calculation is performed using the position data of the address number obtained by taking the fraction and the position data of the next larger address number (■). For example, the address number of i-1 is 1.4,
The corresponding position data d is calculated by using the value 13 of the first position data and the value 51 of the second position data, d - (
51-13) Calculate by Xo, 4 +13, and round down to d-28.

When calculating the adjustment in the position axis direction, the value obtained by dividing the moving distance by the position data of the final address number, that is, 10 in the embodiment
071280 is multiplied by the picked-up position data, and the decimal places are rounded down to obtain the actual position data (■).

In this way, data matching the actual time and position during acceleration is created, and the speed command value is calculated from the deviation between the preceding and succeeding actual position data in the pick-up order. output to the robot's servo system (■).

In the example, the above calculation results are summarized as shown in the table below.

Although fractions below the decimal point are ignored in the above calculation, since the acceleration control is performed based on the position data, the moving distance due to acceleration is accurately controlled to the target value.

In reality, after the adjustment calculation in the position axis direction, the actual position data is converted into data of the actual position of the servo system, and then the speed command value is calculated.

Although acceleration control has been described above, deceleration control can also be similarly performed using a data table of position changes according to a required deceleration pattern (which may be different from the acceleration pattern).

(Effects of the Invention) As is clear from the above description, according to the present invention, a standard acceleration/deceleration pattern is stored as a table of position data representing changes in position with respect to time, and this table data is used to store actual A device that performs adjustment calculations in the time axis direction and position axis direction according to acceleration/deceleration to obtain position change data corresponding to actual acceleration/deceleration, and then calculates a speed command value from this position change data to control acceleration/deceleration. Since various accelerations and decelerations with different times and target positions can be controlled using common table data, storage capacity is small.Moreover, since acceleration and deceleration are controlled based on position data, calculations can be made on the robot's travel distance. Accumulated errors due to fractions ignored in the process do not occur, and the robot can accurately accelerate or decelerate to reach the target position, which has the effect of improving the positional accuracy of the robot's movement trajectory.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing an acceleration/deceleration pattern, FIG. 2 is a diagram showing a position change pattern with respect to time based on a standard acceleration pattern, and FIG. 3 is a flowchart showing a processing program for acceleration/deceleration control according to the present invention. It is. 34-

Claims (1)

[Claims] In the method of controlling acceleration/deceleration by sending speed commands to the servo system that drives the robot, a position change pattern with respect to time is determined based on a standard acceleration/deceleration pattern, and position data from the start point to the end point of this change pattern is calculated over time. Acceleration/deceleration patterns are sampled at regular intervals in the axial direction and stored as a table of position data. Adjustment calculations are performed on this table data in the time axis direction in accordance with the actual acceleration/deceleration time, and the target position is calculated. A robot characterized in that it performs adjustment calculations in the position axis direction according to the calculations, calculates a speed command value from position change data corresponding to the actual acceleration/deceleration determined by these calculations, and outputs it to a servo system. acceleration/deceleration control method.