Electricity: motive power systems – Motor-reversing – Armature or primary circuit control
Patent
1992-04-20
1993-06-22
MacDonald, Allen R.
Electricity: motive power systems
Motor-reversing
Armature or primary circuit control
395 87, 31856815, G05B 1942, G06F 1546
Patent
active
052221989
DESCRIPTION:
BRIEF SUMMARY
FIELD OF ART
The present invention relates to a control method and apparatus including multiple rotating operations of at least one axis of a multiple axes (e.g. six axes) joint type robot.
BACKGROUND OF THE INVENTION
A six axes joint type robot including three basic axes and three wrist axes is structured by the following six axes as shown in FIG. 6: to have the degree of freedom around the perpendicular (Z.sub.0 axis) degree of freedom around the Z.sub.1 axis perpendicular to the Z.sub.0 axis degree of freedom around the Z.sub.2 axis parallel to the Z.sub.1 axis degree of freedom around the Z.sub.3 axis perpendicular to the Z.sub.2 axis degree of freedom around the Z.sub.4 axis perpendicular to the Z.sub.3 axis degree of freedom around the Z.sub.5 axis perpendicular to the Z.sub.4 axis
The 1st axis 2 to 3rd axis 4 are called the three basic axes, while the 4th axis 5 to 6th axis 7 are called the three wrist axes.
As described above, each joint has one degree of freedom and the robot as a whole has six degrees of freedom.
In such a six joint type robot, each axis has a restricted operating range within .+-.180 degrees from the structural reason thereof.
Recently, there has been a demand for the expansion of the operating range of robots. For this purpose, the structure of robots has been modified to provide the axes for realizing rotation of .+-.180 degrees or more. Thereby, the operating range can be expanded up to the range under .+-.360 degrees with improvement of the control method.
Such improved control method will be explained in the sequence of the flowchart shown in FIG. 4 with a calculation example of link angle (angle of each axis in the joint coordinates system) of the wrist joint (the 6th axis 7 in FIG. 3).
In the case of realizing linear interpolating operation by the 6 axes joint type robot shown in FIG. 3, the robot is operated by converting the rectangular coordinate data (position data and posture data) into each joint coordinate data (reverse conversion) in every one unit clock (one sampling period) to obtain a command value of each axis in the joint coordinate system and by giving such command values to each drive axis.
An example of such reverse conversion is described in the Japanese Laid-open Patent No. 62-193786. Namely in the reverse conversion, the command values of link angles .theta..sub.1 -.theta..sub.6 are obtained by the first step for calculating the link angles .theta..sub.1, .theta..sub.2, .theta..sub.3 of three basic axes from the position data P.sub.x, P.sub.y, P.sub.z, the second step for calculating the link angles .theta..sub.4, .theta..sub.5, .theta..sub.6 of the wrist joints from the posture data A.sub.x, A.sub.y, A.sub.z (vectors of direction in which the robot hand comes near to an object), O.sub.x, O.sub.y, O.sub.Z (vectors for designating the direction of robot hand) and N.sub.x, N.sub.y, N.sub.z (vectors of tangent direction for designating three vectors to retake the right hand system) and the link angles .theta..sub.1, .theta..sub.2, .theta..sub.3 of three basic axes obtained in the first step, and the third step for calculating again the link angles of three basic axes from the above position data and the link angles obtained in the second step.
Step 40 in FIG. 4 indicates a step for obtaining the link angle of the 6th axis (link angle at the next position where the control point of the robot is to be moved to as a target) through the reverse conversion by the procedures explained above. In this case, the link angle of the obtained target value is defined as ANS. In step 40 of FIG. 4, x can be calculated from the formula
Here, the link angle of the target value ANS can be obtained from the position data and posture data, according to the reverse conversion method described above. This link angle is defined as a value uniquely within the range of -180.degree.-+180.degree. by obtaining a value of tan.sup.-1 x considering the signs of sin .theta..sub.6 and cos .theta..sub.6. However, the sign of angle which indicates the position is defined as + for clockwi
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Gosho Satoshi
Yamamoto Minoru
Davis George
Kabushiki Kaisha Yaskawa Denki Seisakusho
MacDonald Allen R.
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