STUDY ON OPTIMAL PATH AND OPERATING TIME FOR DRIVING A MANIPULATOR WITH SAVING ENERGY

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It is important to save the dissipated energy even of manipulators for improving the environment of the earth which is warmed up by CO_2 gas emitted from thermal power plants. Hence, this project is studied about an optimal path and operating time which minimize the dissipated energy in PTP motions of a vertically articulated manipulators. A globally optimal path is roughly estimated so that the heavier link is accelerated toward gravitational direction and decelerated toward anti-gravitation. This proposed path is used as a starting function of the iteration method solving a non-linear two-point boundary-value problem. The simulation results show that a proposed optimal path can reduce the dissipated energy to 1/14〜1/30 compared with conventional path when the operating time is selected so as to be optimal.In order to implement the simulation results, two-link manipulator driven by two direct drive motors is improved so that the first and second links can be rotated over 360 degree, and the parameters such as inertias and Coulomb friction forces of the links are identified. When the manipulator are commanded to be optimal velocity function obtained by the simulations via a digital signal processor, the path from the experimental result are verified without error. The dissipated energy is measured at input of servo-driver. The measured energy is a little larger than the energy of the simulation result. A little difference is due to the conversion loss of the servo-driver implemented by three-phase inverter.