Cooperative Research on the Vibration and High-Speed Controls of Flexible Robot Arm

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The present project was pursued for the past three years under the collaboration of Tohoku University, Japan and Chonbuk National University, Korea to construct effective control schemes to accomplish high-speed positioning of light-weight robotic manipulators with heavy payload at the tip, taking into account the flexibility of the manipulator links. The details of the project are as follows.1. A simple scheme of tip sensing and base torquing was studied in detail, where the position feedback was measured at the ends of each links by gap sensors fixed in space. The measurement was then used together with the estimated endpoint velocity as a basis for applying control torque to the other end of the link. To this end, governing equations of the system that takes into account the flexibility of the links were constructed and the simulation results were obtained to find the optimum PD feedback gains of the controller.2. Several prototype manipulators and the controllers were constructed at both Tohoku University and Chonbuk National University to see the effectiveness of the control scheme proposed here. It was found that the simple control scheme works well for the set-point of the single-link and multi-link flexible manipulators.3. Inverse dynamics of the flexible manipulator was examined, in which the arm base was translated in the lateral direction so that the arm-tip realizes a prescribed motion. This is an open-loop control scheme, much easier than the closed-loop PD control. Theoretical calculation and the corresponding experimental results showed that the open-loop control again works well for the point-to-point control of the flexible arm system.