Motion planning for flexible manipulators




Pond, Christopher Burke

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As robotic manipulators become more prevalent, particularly in hazardous environments or for repetitive tasks, demand continues for increased performance and decreased cost. In some applications, both can be achieved by reducing the weight of the manipulator. However, reduced weight often leads to significant structural flexibility and vibration which, for most tasks, is generally regarded as detrimental to performance. Although there has been a great deal of research in the area of controlling flexible manipulators to follow a desired trajectory, much less work has been directed towards choosing the trajectory itself. The objective of this work is to optimize point-to-point motions in joint space to reduce vibration. This problem is formulated as one of functional optimization and the applicable methods of solution are reviewed. An indirect method is chosen that allows modular software development by preserving the integrity of existing nonlinear dynamics models. Numerical results are compared with trajectories generated by other means and show a significant reduction in vibration possible by optimization, particularly for varying joint paths. Finally, the effectiveness of the trajectory optimization scheme is further evaluated for high-speed, large-angle motions of an experimental nonplanar two-link flexible manipulator. Such results are lacking in the literature, but are very important for assessing the utility of trajectory optimization in the presence of modelling and tracking errors. Again, significant reductions in vibration are demonstrated by using the global optimization approach for trajectory generation.



Machinery, Kinematics of, Manipulators (Mechanism), Robotics