Design and control of series elastic actuators for disturbance rejection
- Control abstractions allow robotic control systems to be built up layer upon layer. Each subsystem is considered independent, enforcing modularity, hierarchy, and clarity. At the foundation lie actuators, the source of force and motion. Ideally, actuators produce precisely the force or motion commanded, with no knowledge of the control layer above. But in reality, joints with elasticity couple the robot link dynamics to the actuator dynamics. In this thesis, we present the design and control of series elastic actuators (SEA) for disturbance rejection, in order to better realize uncoupled behavior. This thesis is presented in five parts. First, we introduce the concept of SEA, and show the importance of disturbance rejection for actuator abstraction. Current design and control practices have shortcomings with regard to multi-joint robotic systems. In order to treat actuators as ideal sources of commanded torque, we consider both the force response and disturbance response. Second, we review existing SEA controller design for torque control, and present a modification which simplifies control parameter tuning by reshaping the system's dynamics. The controller is validated on an experimental setup. Third, we describe the relevance and implications of disturbance rejection of SEA under closed-loop control. A new design and control methodology based on disturbance rejection is presented. One application of this methodology is ensuring hybrid actuation design and control synergy. Fourth, we present new mathematical models for reactive SEA dynamics, and an accompanying controller design. Reactive SEAs can produce higher bandwidth torque and can be easier to build. Four configuration of reactive SEA are compared to traditional SEA, in force response, disturbance response, and force measurement. The proposed controller reshapes the dynamics, similar to that proposed for traditional SEA. The methods proposed throughout this thesis for design and control of SEA provide tools for shaping SEA's interaction with external forces, and characterizing each actuators' behavior as an independent subsystem.
|Type of resource
|electronic; electronic resource; remote
|1 online resource.
|Stanford University, Department of Mechanical Engineering.
|Statement of responsibility
|Submitted to the Department of Mechanical Engineering.
|Thesis (Engineering)--Stanford University, 2017.
- © 2017 by Brian Daniel Soe
- This work is licensed under a Creative Commons Attribution Non Commercial 3.0 Unported license (CC BY-NC).
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