Multi-objective Fractional Order PID Controller Optimization for Kid's Rehabilitation Exoskeleton

(1) * Intissar Zaway Mail (University of Sfax, Tunisia)
(2) Rim Jallouli-Khlif Mail (University of Sfax, Tunisia)
(3) Boutheina Maaleja Mail (University of Sfax, Tunisia)
(4) Hanene Medhaffar Mail (University of Sfax, Tunisia)
(5) Nabil Derbela Mail (University of Sfax, Tunisia)
*corresponding author


Fractional order Controllers have been used in several industrial cases to achieve better performance of the systems. This paper proposes a Fractional Order Proportional Integral Derivative (FOPID) controller. It is synthesized using Oustaloup approximation, and its parameters are tuned using the Genetic Algorithm (GA) optimization method. The aim is to minimize the error, the energy and the startup torques using two objective functions to improve the control performances and the robustness. The validity of the proposed controller is shown via simulation by controlling a two-link exoskeleton for children's gait rehabilitation, and the results are compared to an Integer order PID (IOPID) controller. Simulation results clearly indicate the superiority of the optimized FOPID in terms of trajectory tracking and the used torques. Moreover, the FOPID controller is tested with parameter uncertainties. Its robustness is proven against thigh and shank masses variation. Both controllers are simulated under the same frequency conditions using Simulink MATLAB R2018a.


Rehabilitation Robot; Fractional order PID Controller; PID Controller; Optimization; Genetic Algorithm;Robustness



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International Journal of Robotics and Control Systems
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