Date of Award

2017

Degree Type

Thesis

Degree Name

Master of Science in Mechanical Engineering

Department

Washkewicz College of Engineering

First Advisor

Richter, Hanz

Subject Headings

Biomechanics, Biomedical Engineering, Engineering, Mechanical Engineering, Robotics

Abstract

Due to the rise of obesity, diabetes and cardiovascular disease, research in human performance and physical activity has received increased attention. Rowing machines are used for performance improvements through concentric exercises, however a combination of concentric and eccentric actions is known to improve the effectiveness of training. In this work, a conventional rowing machine was modified to include an electric motor and a robust impedance control system, enabling programmable impedance with concentric and eccentric capabilities. Eccentric exercises are known to contribute significantly to the efficacy of training and to diminish the detrimental effects of humans operating in microgravity for long periods. The powered machine was developed by replacing the conventional elements of the rowing machine such as the flywheel, fan and the one-way clutch with a torque-controlled motor and a belt transmission. Components were selected on the basis of forces and velocities encountered in the rowing exercise. The powered machine is capable of producing controlled forces during the return stroke, allowing eccentric exercise. Machine parameters such as the flywheel inertia, linear and quadratic damping and spring constants were estimated from a set of data obtained from real-time tests. Subsequently, a hybrid robust impedance controller was incorporated into the model. The controller incorporates two discrete states corresponding to the pull and return phases. Discrete states transitions are determined from a law driven by force sensing and the state of a virtual flywheel. The prototype and control system were tested in real-time, replicating the operation of the conventional rowing machine. Moreover, arbitrary impedances were programmed and a 1:1 eccentric/concentric power ratio was demonstrated.

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