A Grey Wolf Algorithm Based Super Twisted Sliding Mode Controller for an Electric Load Simulator for Testing Actuators of Aircraft Elevator

Abstract

The use of an Electric Load Simulator (ELS) is crucial for applying aerodynamic load to an actuation system for testing and qualification of the actuation system. Large extra torque is produced on the load simulator by the movement of the under-tested actuator, friction torque disturbance, and unknown disturbance. The response time and accuracy of the ELS are impacted by this large extra torque, which in turn affects the testing and verification of the actuators of aircraft elevators. By using conventional control techniques, it is challenging to compensate for and suppress the extra torque produced. The mathematical model of ELS is represented using state space and transfer functions. Nonlinear friction torque disturbance is modeled using the LuGre friction model. Super twisted sliding mode controller (STSMC) is used for this system and the parameters of the controller are tuned using the Grey wolf optimization (GWO) algorithm. The GWO tuned PID (GWO-PID) and the Ziegler Nichols tuned PID (ZN-PID) controllers are used for the comparison of the proposed controller. The controller’s performance evaluation is done using MATLAB/Simulink. At 1 Hz loading frequency and for reference sine input, GWO-STSMC improved the suppression of the residual torque by 59.31% as compared with ZN-PID and by 22.43% as compared with GWO-PID. The GWO-STSMC also has better performance than GWO PID and ZN-PID controllers as loading frequency increased. The GWO-STSMC controller also has better performance than ZN-PID and GWO-PID in terms of time domain specification. It has a rise time of 0.08sec, a settling time of 0.78sec, and an overshoot of 4.24%. According to the results, the tracking performance of GWO-STSMC is better than ZN-PID and GWO-PID as the loading frequency increases. GWO-STSMC has a better ability to suppress the large extra torque produced in ELS. For the random reference input, GWO-STSMC outperforms both ZN-PID and GWO-PID controllers.