Closed-loop Real-time Control of a Novel Linear Magnetostrictive Actuator
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This thesis presents the design of various closed-loop real-time control of a novel linear magnetostrictive actuator. The novel linear magnetostrictive actuator which uses Terfenol-D as the magnetostrictive material was developed by Sadighi. It solves the problem of power consumption in a conventional magnetostrictive actuator. However, the control system of this magnetostrictive actuator cannot control the current in the coils, which limits the performances of the real-time position control. In the closed-loop real-time control system proposed in this thesis, the controller is designed depending on the change of current. The closed-loop real-time control design focused on the position control of the active element in the novel linear magnetostrictive actuator. The closed-loop position-control system of the linear magnetostrictive actuator was successfully designed by implementing a closed-loop current-control system as an inner loop of the entire control system. This design offers the flexibility to design various position controllers in the closed-loop position-control system. The closed-loop current-control design uses pulse-width modulation (PWM) signal to change the current in the coils of the novel linear magnetostrictive actuator. By changing the duty ratio of the PWM signal, the current in the coils can be changed from zero to its maximum value. With a current controller using an integrator with a gain of 10, the current can be controlled with high response time and an error of /- 0.01 A. The position-controller design was successfully conducted by using four different approaches. First, a proportional-integral-derivative (PID) controller which was designed by relay-auto tuning method with experiments exhibited a position error of ±1 μm with a 5 μm peak-to-peak position noise. Second, a PID controller which was designed by root-locus can control the position with a position error of /- 3-4 μm with a 5 μm peak-to-peak position noise. Third, a linear variable velocity controller exhibited a position error of /-5 μm with a 5 mu m peak-to-peak position noise. Then, the sliding mode control (SMC) exhibited a position error of /-5 μm with a 5 μm peak-to-peak position noise.
Chen, Chien-Fan (2010). Closed-loop Real-time Control of a Novel Linear Magnetostrictive Actuator. Master's thesis, Texas A&M University. Available electronically from