Integral admittance shaping: A unified framework for active exoskeleton control
| Autor: | Umashankar Nagarajan, Gabriel Aguirre-Ollinger, Ambarish Goswami |
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| Rok vydání: | 2016 |
| Předmět: |
0209 industrial biotechnology
Frequency response Admittance Computer science General Mathematics 0206 medical engineering Passivity 02 engineering and technology 020601 biomedical engineering Computer Science Applications Exoskeleton 020901 industrial engineering & automation Industrial Engineering & Automation Control and Systems Engineering Control theory Robustness (computer science) Torque Exoskeleton Device Reduction (mathematics) human activities Software Simulation |
| Popis: | Current strategies for lower-limb exoskeleton control include motion intent estimation, which is subject to inaccuracies in muscle torque estimation as well as modeling error. Approaches that rely on the phases of a uniform gait cycle have proven effective, but lack flexibility to aid other kinds of movement. This research aims at developing a more versatile control that can assist the lower limbs independently of the movement attempted. Our control strategy is based on modifying the dynamic response of the human limbs, specifically their mechanical admittance. Increasing the admittance makes the lower limbs more responsive to any muscle torque generated by the human user.We present Integral Admittance Shaping, a unified mathematical framework for: (a) determining the desired dynamic response of the coupled system formed by the human limb and the exoskeleton, and (b) synthesizing an exoskeleton controller capable of achieving said response.The present control formulation focuses on single degree-of-freedom exoskeleton devices providing performance augmentation. The algorithm generates a desired shape for the frequency response magnitude of the integral admittance (torque-to-angle relationship) of the coupled system. Simultaneously, it generates an optimal feedback controller capable of achieving the desired response while guaranteeing coupled stability and passivity. The potential effects of the exoskeleton's assistance are motion amplification for the same joint torque, and torque reduction for the same joint motion. The robustness of the derived exoskeleton controllers to parameter uncertainties is analyzed and discussed. Results from initial trials using the controller on an experimental exoskeleton are presented as well. A control method for lower-limb exoskeletons based on modifying the dynamic response of the legs.Active control renders the lower limbs more responsive to muscle torques generated by the human.Optimization method synthesizes a controller capable of generating the desired dynamic response.Optimization also ensures the stability and passivity of the coupled human limb exoskeleton.Control robustness to parameter uncertainties is analyzed and discussed. |
| Databáze: | OpenAIRE |
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