A novel integrated nonlinear approach for an electric power steering system based on multiple object control

Purpose An integrated nonlinear control solution is introduced in this paper to improve the performance of an electric power steering (EPS) system. Design/methodology/approach This algorithm is established based on combining two robust nonlinear control techniques: sliding mode control (SMC) and backstepping control (BSC). The phase difference phenomenon is improved by adjusting the input of the BSC technique based on a proportional-integral (PI) controller, whose parameters are optimally calculated by a genetic algorithm (GA). This new combination produces a robustly stable algorithm called SMC-BSC-PI-GA with control signals chosen to satisfy the Lyapunov stability condition. Findings The algorithm’s performance is evaluated by simulation, which is performed in the MATLAB–Simulink interface for two specific cases. Based on the paper findings, the controlled objects, steering column angle (SCA) and steering motor angle (SMA), obtained from the SMC-BSC-PI-GA algorithm, follow the reference value with negligible error (approximately zero in some cases). The energy consumption efficiency of this controller is improved, while the phase difference phenomenon is wholly eliminated, and the influence of chattering is negligible. Controller performance is guaranteed in all investigated cases, even when speed and driver torque change. Originality/value This integrated nonlinear algorithm can decline systematic errors (for controlled objects), reduce energy consumption and eliminate the influence of disturbances, which are the problems that exist for other algorithms.