Yasser Mahmoud Alsayed, Ahmed Ali Abouelsoud, and Ahmed M.R. Fath El Bab
Shear strain, SMA helical spring actuator, hybrid sliding mode controller, fuzzy logic auto tuner, remote palpation system, tactile display
This paper presents a novel design and implementation method to the shape memory alloy (SMA) helical spring actuator modelling. The proposed approach is based on shear-strain-driven method. The main advantage of this approach is the ability to remove the problem of the algebraic loop due to the implementation method that followed when the SMA material constitutive equations and the SMA actuator dynamics are coupled through differentiation of algebraic constitutive equations which is the major cause of controllability losing. Using the proposed approach, a new hybrid sliding mode adaptive proportional integral controller is designed to control the position of the SMA actuator. The auto-tuning of the proposed controller parameters is performed through the fuzzy logic algorithm. The proposed SMA actuator position control system is used to represent the shape/height of an organ and it is used as a tactile element in a tactile display device. Simulation results of the proposed model show the ability of the implementation method to describe the hysteresis characteristics and the SMA behavior when subjected to complex thermo-mechanical loading. Simulation results of the SMA actuator closed loop system show the efficacy of proposed controller and its ability to overcome the drawbacks of overshoot and steady-state error of controllers in literature and increases the actuator cycle rate through reducing the actuation time. The advantages of the proposed implementation model and controller are confirmed by the practical results.
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