Servo control of pneumatic actuators is difficult due to the high compressibility and non-linear flow of air. Friction as well as uncertainties in the parameters and model character-izing dynamics of the pneumatic systems further contribute to control challenges. These drawbacks cause stick-slip motion, larger tracking error and limit cycles, which degrades the control performances. Selection of a controller that satisfies requirements of the per-forming tasks is thus crucial in servo-pneumatic applications. This thesis focuses on the design and experimental evaluation of a model-based, nonlinear controller known as Dy-namical Adaptive Backstepping-Sliding Mode Control (DAB-SMC). Originally designed for chemical process control and applied only in simulations, the DAB-SMC is adopted in this thesis and applied to the new area of servo-pneumatic control of a single-rod, double acting pneumatic cylinder and antagonistic pneumatic artificial muscles (PAMs). The con-troller is further enhanced by augmenting it with LuGre-based friction observers to com-pensate the adverse frictional effect presents in both actuators. Unlike other research works, the actuators are subject to a varying load that influences control operations in two different modes: motion assisting or resisting. The implementation of DAB-SMC for such servo-pneumatic control application is novel. The mass flow rates of compressed air into and out of the actuators are regulated using one of the following valve configurations: a 5/3-way proportional directional valve, two 3/2-way or four 2/2-way Pulse Width Modu-lation (PWM)-controlled valves. Over the entire range of experiments which involve vari-ous operating conditions, the DAB-SMC is observed to track and regulate the reference input trajectories successfully and in a stable manner. Average root mean square error (RMSE) values of tracking for cylinder and PAMs when the compressed air is regulated using the 5/3-way proportional valve are 1.73mm and 0.10°, respectively. In case of regu-lation, the average steady-state error (SSE) values are 0.71mm and 0.04°, respectively. The DAB-SMC exhibits better control performance than the standard PID and classical SMC by at least 33%. The DAB-SMC also demonstrates robustness for up to 78% in un-certainty of load parameter. When the control valve is replaced by the PWM-controlled valves of 3/2-way and 2/2-way configurations, performance is slightly compromised. / May 2016
| Identifer | oai:union.ndltd.org:MANITOBA/oai:mspace.lib.umanitoba.ca:1993/31136 |
| Date | 24 February 2016 |
| Creators | Abd. Rahman, Ramhuzaini |
| Contributors | Sepehri, Nariman (Mechanical Engineering), Balakrishnan, Subramaniam (Mechanical Engineering Annakkage, Udaya (Electrical and Computer Engineering) Surgenor, Brian (Queen's University) |
| Source Sets | University of Manitoba Canada |
| Detected Language | English |
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