Optimum control of flexible robot arms on fixed paths
Book, Wayne John
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Productivity of the industrial robots are directly related to the speed of the task execution. The speed of the robots can be drastically improved by using better control algorithms and reducing the weight of the manipulator. The speed of a robotic manipulator is constrained by manipulator dynamics and actuator capabilities. Increasing the size of the actuators is not a solution since that will increase the weight of the the overall system leading ·to a relatively heavier system. The more realistic approach to the problem is to find the optimum control solution for a manipulator to follow a pre-defined path in minimum time, with limited actuator capabilities. In terms of the dynamic constraints, the weight of the arms may be the most important factor. If a light-weight arm structure is used, actuators will be able to afford higher speeds during the task execution than they would for rigid arm structure. On the other hand using flexible-arms has a major draw-back which is the flexible vibrations, while increasing the speed. This paper presents the minimum time control solution of a two link flexible arm with actuator constraints. We solved the minimum time problem with no constraints on the flexible modes and show· the time improvement due to the use of light-weight arms. The objective is to modify the trajectory, such that flexible vibrations are bounded while changing the solution from the previous one as little as possible. Practical ways of trajectory modifications for flexible arms are discussed.