Date of Award

Spring 2012

Degree Type

Thesis

Degree Name

Master of Science in Mechanical Engineering (MSME)

Department

Mechanical Engineering

Supervisor

Gary M. Bone

Language

English

Abstract

This thesis presents the development of a novel hybrid pneumatic-electric actuator which combines the advantages of both pneumatic and electrical actuator.

The hybrid actuator consists of a pneumatic cylinder and a DC motor. They are connected in parallel using gears. The components are sized to provide the torque required to rotate a single-link robot arm vertically upwards. On/off solenoid valves are used rather than servo valves to keep the hardware cost low.

A mathematical model of the nonlinear actuator dynamics is derived using a combination of physical laws and empirical curve fitting. The dynamics of the mechanical, electrical and pneumatic elements are included. Then a novel discrete-valued model-predictive control plus integral compensator algorithm is created for controlling the position of the pneumatic cylinder using the on/off valves. The control algorithm for the hybrid actuator is completed by using a conventional PD algorithm to control the electric motor.

Experiments shows the hybrid actuator outperform pneumatic actuator in every aspect. Conversely, the DC motor added a faster acting and finer quantized force to the pneumatic cylinder force, which greatly improved the dynamic position control performance of the hybrid actuator. In experiments, the mean root-mean-square error and the maximum absolute error improved by 84% and 77%, respectively.

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