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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Dynamical Adaptive Backstepping-Sliding Mode Control for servo-pneumatic positioning applications: controller design and experimental evaluation

Abd. Rahman, Ramhuzaini 24 February 2016 (has links)
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

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