JPH1058361A - Control device of manipulator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To change an arbitrary joint to an arbitrary angle, and to enable position-attitude determining operation while an obstacle is avoided by providing a means for changing the angle of each joint arbitrarily while the tip position/ attitude are kept in manipulator having degrees of freedom of redundancy. SOLUTION: An output Tr of a target tip position/attitude setting means 1 and an output Tp from the current forward end position detecting means 2 are input to a comparator 2 to obtain a tip position/attitude deviation Ep. A position /attitude gain amplifying means 4 amplifies the deviation Ep of the comparator 3 to output a tip position /attitude speed Vp. An angle converting Jacobian matrix operating means 6 inputs a detected angle πd from an angle detector and computes an angle converting Jacobian matrix J. A joint angle converting means 5 inputs an amplified value Vp and the Jacobian matrix J, and the range of evaluation function δ 0 can be varied to an arbitrary shaft specified from the outside by each shaft evaluation function varying means 10. Accordingly, the joint can be changed in the angle while keeping the position/attitude of the tip.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a manipulator control device having a redundancy degree of freedom.

[0002]

2. Description of the Related Art A conventional manipulator control device having a redundancy degree of freedom will be described with reference to FIGS. FIG. 4A shows an operation sequence for determining the tip position / posture of the manipulator, and compares the output [Tr] of the target tip position / posture setting means 1 with the output [Tp] of the current tip position / posture detection means 2. Input to the detector 3 to determine the tip position / posture deviation [Ep].

The current tip position / posture detecting means 2 inputs a detection angle [θd] from an angle detector (not shown) for detecting the angle of each axis, and calculates the current tip position / posture, ie, [Tp], based on this. To detect. The position / posture gain amplifying means 4 inputs and amplifies the deviation [Ep] of the comparator 3 and outputs a tip position / posture velocity [Vp]. The Jacobian matrix calculating means 6 for angle conversion receives the detected angle [θd] from the angle detector and calculates the Jacobian matrix for angle conversion [J].

[0004] The joint angle conversion means 5 calculates the amplified value [Vp].
Then, the Jacobian matrix [J] is input and converted into a joint angle [θ] based on the equation (1) shown in FIG. Summation means 7
Receives the converted joint angle [θ], inputs all the axes, and calculates the sum of the joint angles [θc] of each axis. Output.

Here, equation (1) is the sum of the first and second terms. The first term is called a Jacobian, which is a mathematically well-known term and has a redundant degree of freedom. Is the term for which there is an infinite solution from. On the other hand, the second term is a certain evaluation function (δθ)
Is a term that has the function of determining the joint angle as one according to
The evaluation function works to position the joint in the middle of the range in which the evaluation function is defined as much as possible. As shown in FIG. 4B, the range of the evaluation function is fixed to the movable range of each joint hardware. . FIG. 5 shows a conventional seven axes (# 1 to # 1).
It is a perspective view of the manipulator which has a redundant degree of freedom of 7).

[0006]

As described above, when trying to determine the position and posture of the distal end of the manipulator according to the conventional technique, the joints are always determined at almost the same angle. Therefore, as a manipulator, the shape of the arm is always substantially fixed, and an operation utilizing the degree of redundancy such as a position / posture determination operation avoiding an obstacle cannot be performed.

Accordingly, the present invention has a function of determining the position and orientation of the tip and arbitrarily changing the shape of the arm while maintaining the position and orientation of the tip, that is, a function of changing an arbitrary joint to an arbitrary angle. An object of the present invention is to provide a manipulator control device having the same.

[0008]

According to a first aspect of the present invention, there is provided a control device for a manipulator having a redundant degree of freedom, wherein when the manipulator has a redundant degree of freedom, a position of a tip of the manipulator may be reduced. A manipulator control device including means for arbitrarily changing the angle of each joint while maintaining a posture.

According to the first aspect of the present invention, the shape of the manipulator can be freely changed while determining the position and orientation of the tip of the manipulator having the redundancy degree of freedom. It is possible to work in narrow places that cannot be achieved with an industrial robot having six axes or less.

[0010]

Embodiments of the present invention will be described below with reference to the block diagram of FIG. The difference from the conventional example of FIG. 4 is that each axis evaluation function changing means 10 is newly added to the joint angle converting means 5. Each axis evaluation function changing means 10 changes the range of the evaluation function (δθ) of the second term of the equation (1) with respect to an arbitrary axis specified from the outside while leaving the Jacobian of the first term of the equation (1) as it is. It is made possible.

[0011] With this configuration, in the manipulator controlled to the tip position / posture of a certain target, an evaluation function having a certain width with the current position of a certain specified joint as a center is defined, and the center thereof is defined. Redefining the evaluation function with the same width while gradually shifting the position from the current position to the direction in which you want to move, the joint has the function of trying to move the joint as much as possible to the center of the width of the evaluation function. The angle is changed from the outside to the specified direction,
By the operation of the first term, the tip position and posture of the manipulator are maintained.

Hereinafter, this will be described in detail with reference to FIGS. 2 and 3. Here, an example in which the present invention is applied to a redundant manipulator having the joint configuration shown in FIG. 5 will be described. FIG. 2 shows a control flow of the manipulator control device of the present invention. In step 1, an evaluation function of width 2α is defined around the current joint angle.

Next, in step 2, when the moving direction and the moving amount of the joint to be moved are designated from the outside, the target joint position is calculated based on the sum with the current joint position. Here, the current value should immediately change following the target position.
Since a time delay usually occurs, if the evaluation function having the width 2α is redefined around the target position, the current position may fall outside the range of the evaluation function, and a solution may not be obtained.

In order to avoid this, an evaluation function having a width 2β is redefined around the target position, with β being the larger of the distance between the two range ends defined in step 1 and the target position.
At this time, the current position always exists in the evaluation function, and the joint will always move toward the center of the evaluation function due to the control function, so the joint angle must move in the direction specified from the outside. become.

When the evaluation function is continuously redefined from the moved joint position, the redefined range of the evaluation function, and the target joint position, β approaches α, and finally, step
As shown in 3, the evaluation function is defined by a width of 2α centering on the target position, and as a result, the joint angle moves until it substantially matches the target joint angle.

In the manipulator, the evaluation function change is applied to the third axis. The movable range of the third axis is ±
180 °, and 45 ° is employed as α. When the target angle is set so that the angle of the third axis is moved in the positive direction while maintaining the tip position and posture of the manipulator, the third axis moves in the indicated direction. As a result, the shape of the manipulator changes in the direction of the arrow in FIG. 3 while maintaining the tip position and posture.

According to the embodiment described above, the shape of the manipulator can be freely changed while determining the position and orientation of the tip of the manipulator having a redundant degree of freedom. Since the following industrial robots enable work in narrow places that cannot be done by robots, robots can perform work that had to rely on humans instead, and humans are said to be "dangerous, dirty and tight" so-called 3
It is possible to release from K work.

[0018]

According to the present invention, the position and orientation of the tip are determined, and at the same time, the shape of the arm is arbitrarily changed while maintaining the position and orientation of the tip, that is, any joint is changed to an arbitrary angle. A manipulator control device having a function can be provided.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating an embodiment of a manipulator control device according to the present invention.

FIG. 2 is an operation flowchart for explaining the operation of FIG. 1;

FIG. 3 is a diagram for explaining the operation of the manipulator having a redundant axis according to the present invention.

FIG. 4 is a mechanical diagram of a manipulator having a redundant axis, which is an object of the present invention.

FIG. 5 is a diagram illustrating an example of a conventional manipulator control device.

[Explanation of symbols]

 1: Target tip position / posture setting means 2: Current tip position / posture detecting means 3: Comparator 4: Position / posture gain amplifying means 5 ... Joint angle converting means 6 ... Jacobi matrix calculating means for angle conversion 10 ... Each axis evaluation function Change means

Claims (1)

[Claims] 1. A control device for a manipulator having redundant degrees of freedom, wherein the manipulator includes means for arbitrarily changing the angle of each joint while maintaining the tip position / posture when the manipulator has redundant degrees of freedom. Control device.