A Study of Operation Algorithm of a Redundant Manipulator with Tilted Rotary Joints
- Paper number
IAC-05-E2.P.04
- Author
Mr. Taichi Watanabe, Keio University, Japan
- Year
2005
- Abstract
In recent years, space robots are in practical use and various manipulators are being operated on the International Space Station. However, most of the ISS tasks are just carrying a large payload from one point to another. Any precise work so far done by Astronauts, and the robotic work is yet to be explored. This paper deals with a redundant manipulator which has tilted axes by 45 degrees relative to the arm’s axis. This type of manipulator is uncommon, and the study has not been performed yet. This type of robot has a drawback that the kinematics for this manipulator is complicated and that it has numberless singular points. On the other hand, this manipulator should be capable of special motions which cannot be executed by commonly used PUMA type manipulators. So this study aims at developing operation algorithms for avoiding these singular points, and identifying special motions of this manipulator.
National Aerospace Laboratory (NAL, and present JAXA) developed a 7-DOFs redundant manipulator with tilted rotary joints, called NAL-Arm. The previous NAL-Arm system had a lot of problems, so the system has been improved last year as follows. First, it can change the rotating speed of the joint continuously. Second, the limits of joint angles is 3 to 20 times compared with before and it can take arbitrary theoretical posture.
To generate end point trajectories avoiding singular points, in this study, general inverse kinematics method using pseudo inverse matrices is used as a means for judging whether a trajectory cross singular point or not. 2 types of method has been devised to generate trajectories which is not judged yet. The first is generating elemental function curves one after another. The second is updating a B-spline curve gradually. And using “self motion” has been added as sub method. The method integrated with these success generating avoiding singular point trajectories keeping end point position and attitude at probability of 95.8
In general, NAL-Arm takes the complex arm posture, but it has been found that NAL-Arm can move while whole of the arm is restrained to one plane, by using movable miniature. And further analysis found that NAL-Arm have 9 types of restrained motion to one plane and all of these have 2-DOFs. Then this has been integrated with kinematics of NAL-Arm and the 2-DOFs inverse kinematics system restrained to one plane was achieved.
By this study, a practicable and dependable NAL-Arm experimental system has been developed, the motion algorithm of avoiding singular point has been devised and verified, and the operation algorithm restrained to one plane has been achieved.
- Abstract document
- Manuscript document
IAC-05-E2.P.04.pdf (🔒 authorized access only).
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