Design of Multi-Degree-of-Freedom Mechanisms for Optimal Dynamic Performance

Design methods for selecting the actuator sizes and the link lengths of multi-degree-of-freedom mechanisms for minimum time motions along specified paths and between given end points are presented. The design problem is first formulated as a parameter optimization, using the actuator sizes and the link lengths as the design variables, and motion time along the path as the cost function. A more efficient method for obtaining near-optimal designs is then presented, based on the acceleration lines which have been shown to approximate the geometric shapes of time optimal paths [15]. Near-optimal designs are simply obtained by curve-fitting the acceleration lines to the desired path, or to the end points. Examples of the design of two and five-bar mechanisms demonstrate significant reductions in motion times for the optimal and the near-optimal designs, and significant savings in computation time for the approximate method.