Switchable parallel elastic actuators in monopod and quadruped applications

Abstract
Legged robotics have proven to be a viable approach to extending human reach to various terrains that are unfit for conventional wheeled locomotion. While advances have been made to further capacity of these robots through a variety of design approaches, there are still difficulties in bridging compromise between energetic efficiency and joint dexterity. Switchable Parallel Actuators (Sw-PEAs) have been proposed and developed in legged robotics to address this trade-off by providing the benefits of both control authority of the joint, and passive compliance, in a manner that is desired by the overall objective of the application. ☐ This thesis begins by building upon the Sw-PEA concept, by first discussing a two-link monopedal robot, SPEAR-II, which is the second design iteration of the robot SPEAR (Switchable Parallel Elastic Actuator Robot). A mathematical model of the monopod is created with a focus on understanding the internal system interactions to use for simulation and controller design. Parameter identification experiments are then conducted to improve the accuracy of the model by estimating previously unknown variables. Using the refined monopod model, a simple controller is tuned and implemented on the robot during hopping experiments. Lastly, a quadruped design is proposed using SPEAR-II as a legged template. A quadruped model is derived to perform analysis on key design parameters. Finally, the thesis concludes with results for the quadruped simulation as a feasibility study for the proposed design using the Sw-PEA.
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