A methodology for designing a parallel, passive-assist device to augment an active system using energy minimization based on a known maneuver is presented. Implementation of the passive-assist device can result in an improvement in system performance with respect to efficiency, reliability, and/or utility. In previous work we demonstrated this concept experimentally on a single link robot arm augmented with a torsional spring. Here we show that the concept can effectively be applied to more complicated machines performing known periodic motions by simulating a 3-link manipulator arm. The arm can be decoupled prior to optimization using inverse dynamics — greatly simplifying the optimization problem. The addition of optimized springs results in a system-wide decrease in energy consumption of 70.9%. Finally, we consider a distribution of possible maneuvers and use the concepts of robust design to find springs that increase the guaranteed energy savings at a 90% confidence level.

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