JPH04271407A - Robot control method - Google Patents

Abstract

PURPOSE:To easily generate a smooth continuous locus at the time of generating the continuous operation locus of an operation and the next operation. CONSTITUTION:First, vVf+1 is obtained. Next, a circle having a point A as the center and a radius ¦vVf+1¦ and a circle having a point B as the center and a radius ¦vVb¦ are drawn. Intersections C and D between two circles are obtained which satisfy condition ¦vVf¦-¦vV'f+1¦<=alphaT and are operation points just after synthesis. Thereafter, a limit value theta/2 of the angle of displacement formed by vVf+1 and vV'f+1 is obtained by the function ¦vVf¦. However, it is so determined that theta<=acute angleCAD is true. An arc C'D' which has the point A as the center and a center angle theta is obtained in an arc CD of the circle B. Thus, acute angleC'BD'/2 is the angle of displacement for allowable synthesis.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of controlling a robot, and more particularly to a method of controlling a robot that controls the tip of a robot arm having multiple degrees of freedom.

0002

[Prior Art] Generally, in order to speed up robot operation by eliminating unnecessary stopping operations during robot operation,
It is necessary to connect two motions, one motion and the next motion, continuously and smoothly without stopping. In order to realize such continuous motion, conventionally, a continuous motion trajectory has been generated by adopting a method in which when one motion starts decelerating, the next motion starts accelerating.

0003

However, in such a method, depending on the displacement angle of the two movements to be combined, a component is generated that makes the velocity direction opposite to the positive and negative directions. For this reason, the acceleration and deceleration values at the joints of motions may become excessive, resulting in the disadvantage that unreasonable force is applied to the hands of the robot arm.

[0004] This drawback will be specifically explained using FIGS. 4 and 5. FIG. 4 shows two combined motions A and B and their displacement angles. The more acute the displacement angle, the more oppositely positive and negative components occur in the velocity direction. The positive and negative components are at their maximum when the displacement angle is 0°. A, B at that time
Figure 5 shows the acceleration/deceleration pattern when the two movements are combined.
Shown below. As shown by the broken line in Figure 5, excessive acceleration and
Since a deceleration value occurs, a smooth connection cannot be achieved.

[0005] The present invention has been made in view of the above-mentioned circumstances, and its purpose is to create a smooth trajectory of two consecutive motions, one motion and the next motion. The object of the present invention is to provide a robot control method that can easily generate continuous trajectories.

[0006]

[Means for Solving the Problems and Their Effects] When operating a robot, the present invention generates a trajectory to be operated between a current position and a target position using an appropriate acceleration/deceleration pattern, and A control method for a robot that controls a robot, in which a velocity vector immediately before the start of the continuous motion and a velocity vector immediately after the start of the continuous motion are generated when generating a continuous motion trajectory of two motions, one motion and the next motion. , the magnitude of the displacement angle created by the velocity vector immediately before the same start and the velocity vector immediately after the same start, and the size of the velocity vector just before the same start, determine when the two movements are combined. This is a method of controlling a robot.

[0007] In other words, this robot control method is based on the difference in magnitude between the velocity vectors that occur immediately before and after the synthesis, respectively, when synthesizing two movements: a certain movement and the next movement that follows it. The purpose is to determine the timing to combine the two movements based on the magnitude of the displacement angle created by these two velocity vectors and the magnitude of the velocity vector that occurs immediately before the combination, and to smooth the connection between the two movements. be.

[0008] The robot control method according to the present invention includes 2
By using velocity vectors in the synthesis of two motions, it is possible to generate smooth continuous motion trajectories. Then, the robot can perform continuous operations smoothly.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be explained in detail below based on one embodiment shown in the drawings. Note that this invention is not limited to this.

FIGS. 1 to 3 all illustrate methods for determining composable displacement angles. From FIG. 1 to FIG. 3, the velocity vector vVf that occurs immediately before synthesis becomes larger. The explanation will be continued below using FIG. 1.

Point A in FIG. 1 represents a deceleration start point at which deceleration of a certain action (referred to as action A) begins. Point B
represents the next point following operation A when no synthesis is performed. If vAB=vVf+1, |vVf+1
|=|vVf|-αT (where α is the acceleration and T is the control period). Note that acceleration and deceleration were performed here with the acceleration α constant.

Next, at point B, if acceleration of the next motion following motion A (referred to as motion B) is started, the magnitude of the velocity vector vVb is |vVb|=αT.

[0013] Here, radius R (=|vVf
+1 |) and a circle with radius r (= | vVb
｜) Draw a circle for each. Let C and D be the intersection points of these two circles. At this time, if the velocity vector immediately after the synthesis is vV'f+1, it is necessary to satisfy the condition |vVf|-|vV'f+1|≦αT in order to avoid excessive acceleration/deceleration values. In FIG. 1, this means that the operating point immediately after synthesis only needs to be located on the arc CD that is farther from point A among the arcs in the circle with radius r.

Furthermore, the velocity vector vVf immediately before synthesis
The limit value of Δθ/2, which is the displacement angle between vVf+1 and vV'f+1, is determined by the magnitude of . In other words,
Δθ is determined by a function of |vVf|, and |v
It is considered that the larger Vf|, the smaller Δθ becomes.

Therefore, Δ determined within the range of ∠CAD
Due to θ, it is sufficient that the operating point immediately after synthesis is on the arc C'D' in FIG. That is, ∠C'B D'/2
is the composable displacement angle of the two movements. And action A
Find the displacement angle for each control cycle after the deceleration start point of
The time when the displacement angle of the two movements A and B becomes larger than ∠C'B D'/2 is determined as the starting point for combining the two movements.

The above determination procedure can be summarized as follows. ■ Find vVf+1. ■ Draw a circle centered on point A with radius |vVf+1| and a circle centered on point B with radius |vVb|. And |vVf|
Find the intersections C and D of the two circles, which are the operation points immediately after synthesis and satisfy the condition -|vV'f+1|≦αT. ■
The limit value Δθ/2 of the displacement angle formed by vVf+1 and vV'f+1 is found from the function G (|vVf|). However, it is determined so that Δθ≦∠CAD. ■Point A
An arc C'D' having a central angle Δθ is found within the arc CD of the circle B, with . ■ Here, ∠C'B D'/
2 is the composable displacement angle.

[0017] Length of arc C'D' in Fig. 1 < Fig. 2
Length of arc C'D' in < Arc C' in FIG.
The length will be D'. This is |vVf|> in FIG.
|vVf| in FIG. 2> |vVf| in FIG. 3
This is because. In addition, Fig. 3 shows the arc CD in circle B.
= arc C'D' is shown.

[0018]

[Effects of the Invention] According to the robot control method according to the present invention, as described above, it is possible to easily generate a continuous trajectory that smoothly connects two movements: one movement and the next movement that follows it. This allows the robot to perform continuous movements smoothly.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram illustrating how to obtain a composable displacement angle of two movements, that is, a certain movement and the next movement that follows it, in an embodiment of the present invention.

FIG. 2 is an explanatory diagram illustrating how to obtain the composable displacement angle of two motions when the velocity vector immediately before composition is larger than that in FIG. 1;

FIG. 3 is an explanatory diagram illustrating how to obtain the composable displacement angle of two motions when the velocity vector immediately before composition is larger than that in FIG. 2;

FIG. 4 is an explanatory diagram illustrating how to obtain a composite trajectory of two operations and its displacement angle in a conventional control method.

FIG. 5 is an explanatory diagram of a composite acceleration/deceleration pattern indicating that an excessive acceleration/deceleration value occurs at a motion connection portion in a conventional control method.

[Explanation of symbols]

vVf Velocity vector immediately before synthesis vVf
+1 Uncombined velocity vector vVb in the next control cycle of vVf Velocity vector of the next operation vV'
Velocity vector immediately after synthesis obtained from f+1 vVf+1 + vVb

Claims (1)

[Claims] [Claim 1] A method for controlling a robot, which generates a trajectory to be operated between a current position and a target position using an appropriate acceleration/deceleration pattern when operating the robot, and controls the trajectory. , when generating a continuous motion trajectory of two motions, one motion and the next motion, the difference in magnitude between the velocity vector immediately before the start of the continuous motion and the velocity vector immediately after the start of the continuous motion, Depending on the magnitude of the displacement angle created by the velocity vector and the velocity vector immediately after the same start, and the magnitude of the velocity vector immediately before the same start,
A robot control method that determines when to combine two movements.