JPH06315880A - Elbow rotating method for seven-axis multi-joint robot manipulator - Google Patents

Abstract

PURPOSE:To readily evade an obstacle and expand the action range allowable at a control point by calculating the joint angle rotating an elbow with the position and attitude of the tip control point kept unchanged according to the prescribed calculation procedures, and allowing such rotation of the elbow. CONSTITUTION:In a seven-axis multi-joint robot manipulator, a rotary shaft connecting the point of a shoulder and a control point is assumed, and a pseudo six-axis robot manipulator for the first axis through the sixth axis with the seventh axis fixed is imagined. The axial angle for rotating the pseudo manipulator around the rotary shaft by a fine angle is obtained by the calculation of inverse transformation, and the fine change of only the attitude at the control point generated by the rotation is corrected. A six-axis robot manipulator for six axes from the tip except for the first axis is assumed, the calculation of inverse transformation is made for matching the attitude at the control point after the elbow is rotated with the initial attitude at the control point to obtain the angles of six axes at the tip, and the joint angle for rotating the elbow by the fine angle is obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for rotating an elbow of a 7-axis articulated robot manipulator in space, deep sea, nuclear power plant or general industry.

[0002]

2. Description of the Related Art A 7-axis articulated robot manipulator (see FIG. 4), which is similar to a human arm by adding an additional axis to the conventional 6-axis articulated robot manipulator, is used to control the position of the tip at the control point during work It is possible to rotate only the elbow part without changing the posture.

[0003]

However, unlike the 6-axis articulated robot manipulator, since there is a redundant axis, the angle of the angular joint axis is not uniquely determined even if the position / orientation at the control point of the tip is determined. It is necessary to devise the control method. The present applicant has previously filed Japanese Patent Application No. 3-286665,
Although Japanese Patent Application No. 4-70325, Japanese Patent Application No. 4-110773, etc. are proposed, there are problems such as complicated arithmetic operations.
Therefore, it is an object of the present invention to provide an efficient method of rotating an elbow while maintaining the position and orientation of the tip control point.

[0004]

The elbow of a 7-axis articulated robot manipulator is rotated as follows. (1) A control point that can be placed at the tip of the manipulator and a shoulder line of the manipulator are selected as rotation axes. (2) Consider the 7-axis articulated robot manipulator as a 6-axis robot manipulator by fixing 7 axes. (3) The 6-axis robot manipulator is rotated around the previous rotation axis by a small angle. For this purpose, the calculation is performed by the inverse transformation of the shaft angle. (4) Since this rotation causes a slight change in only the posture at the control point, this is corrected. (5) Assume a 6-axis robot manipulator by taking 6 axes from the tip excluding the first axis. (6) The angle of the tip 6 axes is calculated by performing the inverse transformation for adjusting the posture of the control point after the elbow rotation to the posture at the first control point. (7) With the above, the joint angle for rotating the elbow by a small angle is obtained. (8) Returning to (2) and repeating this calculation, the axis angle at which the elbow rotates further stops.

[0005]

With the above method, the elbow rotation of the 7-axis articulated robot manipulator can be performed while keeping the original position and orientation at the control point.

[0006]

EXAMPLES Examples of the present invention will be described in detail below. 7
The angle of the first joint of the axis-joint type robot manipulator is { ⁰ q _i } and the relationship between the minute position / orientation change of the tip control point and the minute angle of each axis is expressed as follows.

[0007]

[Equation 1]

However, Δr: a minute position change at a control point in the working space Δω: a minute attitude change at a control point in the working space z _i : a rotational axis direction vector of the i-axis in the DH model h _i : i-axis in the DH model Vector from rotation axis position to control point Δq: Minute rotation angle vector of robot manipulator [Δq ₁ Δq ₂ ... Δq ₇ ] ^T

A unit rotation axis vector k from the shoulder position of the robot manipulator to the control point is set (see FIG. 1). Consider rotation about this axis by Δθ. Since the control point position does not change and only the posture changes, this change is shown as follows. [Δr ^T Δω ^T ] ^T = [0 ^T [Δθ * k] ^T ] ^T (2) Note that [Δr ^T Δω ^T ] ^T = [0 ^T 0 ^T ] ^T is substituted into the left side of the equation (1). Finding a solution that rotates the elbow was the method of Japanese Patent Application No. 4-70325. The method of the present invention decomposes equation (1) as follows.

[0010]

[Equation 2]

However, q ₇ is fixed. The vector Δq is [Δq
_1, Δq _2, ..., a [Delta] q _6] ^T (see FIG. 2).

[0012]

[Equation 3]

However, q ₁ is fixed. The vector Δq is [Δq
₂ , Δq ₃ , ..., Δq ₇ ] ^T (see FIG. 3).
In equation (4), the value of equation (2) is added to obtain the value of Δq ₁ . A new q is obtained with Δq ₇ = 0. q _i = q _i + Δq _i (i = 1, 2, ..., 7) (5) {z _i } and {h _i } are obtained using this value. And it substitutes in Formula (4). Therefore, the following formula is newly calculated. [Δr ^T Δω ^T ] ^T = [0 ^T − [Δθ * k] ^T ] ^T (6) This means that the posture change at the control point is restored by the elbow rotation. Δq _i is obtained by substituting (6) into (4) and solving this equation. ¹ q ⁱ is calculated with Δq _i = 0. ¹ q ⁱ = q _i + Δq _i (i = 1,2, ..., 7) (7) The { ¹ q ⁱ } obtained by the above calculation is obtained when the manipulator is rotated about the rotation axis k by the angle Δθ. This is the joint angle. If this is repeated, the elbow of the manipulator will rotate as much as possible while maintaining the original position and posture at the control point.

Solving the equation (3) or (4) is solving a simultaneous equation of six elements. When the form of the robot manipulator enters the singularity state, the matrix may degenerate and become unsolvable. In this case, it may be necessary to sacrifice the position or orientation of the control point to some extent to obtain a solution. Therefore, it is necessary to confirm in advance that such an operation is possible with a simulator. In the above description, the joints of the 7-axis articulated robot manipulator are described only as the rotation axes, but it goes without saying that the same reasoning is possible even when the slide axes are included in the center. However, in this case, it goes without saying that there are many restrictions that mechanically make elbow rotation impossible, and in many cases, the human arm type 7-axis articulated robot manipulator does not employ a slide shaft.

[0015]

As described above, according to the present invention,
The elbow rotation of the 7-axis articulated robot manipulator has the effect of widening the range of motion that can be taken at the control point by avoiding obstacles or rotating the elbow joint in some cases.

[Brief description of drawings]

FIG. 1 is a control point of a 7-axis articulated robot manipulator,
Diagram showing shoulder points and elbow rotation axis vector k

FIG. 2 is a diagram showing vectors h _i and z _i when the 7th axis is fixed.

FIG. 3 is a diagram showing vectors h _i and z _i when the first axis is fixed.

FIG. 4 is a diagram showing an example of a 7-axis articulated robot manipulator.

[Equation 2]

[Equation 2]

Claims (2)

[Claims] 1. In a 7-axis articulated robot manipulator, a rotation axis connecting the shoulder point of the manipulator and the control point is assumed, and the 7-axis of the 7-axis articulated robot manipulator is fixed and the first The pseudo 6-axis robot manipulator taking 6 axes from the axis is hypothesized, and the axis angle for rotating the pseudo 6-axis robot manipulator by a minute angle around the rotation axis is obtained by the calculation of the inverse transformation, and the control point is obtained by this rotation. Since there is a deviation in the posture at, the 6-axis from the tip excluding the first axis is corrected and the pseudo 6-axis robot manipulator is virtualized, and the posture at the first control point is changed to the control point after elbow rotation. By performing the inverse transformation calculation to match the posture, the angles of the 6 axes of the tip are calculated, and the axis angles of the 7 axes calculated above are used as the command axis angles to rotate around the rotation axis. An elbow rotation method for a 7-axis articulated robot manipulator characterized in that the elbow portion of the manipulator is rotated by a minute angle without changing the position / orientation at the tip control point. 2. In a 7-axis articulated robot manipulator, a rotation axis (k) connecting a shoulder point of the manipulator and the control point without changing the position / orientation at the tip control point.
A small angle (Δθ) around the elbow part of the manipulator around
The minimum joint angle is { ⁰ q
_i }, first, the Jacobian equation of a pseudo 6-axis robot manipulator with the 7th axis fixed [0 ^T [Δθ * k] ^T ] ^T = J _B * [Δq ₁ Δq ₂ ...
Δq ₆ ] ^T is solved and each joint minute angle (Δq
_i i = 1, 2, ..., 6; Δq ₇ = 0) is obtained, and then the angle of each joint is obtained by q _i = q _i + Δq _i (i = 1, 2, ..., 7), and this angle is calculated. By using the Jacobian equation [0 ^T − [Δθ * k] ^T ] ^T = J _F * [Δq ₂ Δ of a pseudo 6-axis robot manipulator consisting of 6 axes of the tip of the manipulator.
q _3. ． ． Δq ₇ ] ^T is solved and each joint minute angle of the manipulator (Δq
₁ i = 2, 3, ..., 7; Δq ₁ = 0) is obtained, and the final joint angle { ¹ q _i } is set as ¹ q _i = q _i + Δq _i (i = 1, 2, ..., 7). Calculate, Δθ
Elbow rotation of a 7-axis articulated robot manipulator characterized by performing elbow rotation by adding a small angle { ¹ q _i − ⁰ q _i } to the initial joint angle { ⁰ q _i } to realize the rotation of Method.