## 1 Introduction  
Switched reluctance motors (SRMs) have received much attention due to the robust structure, large start-up torque, and high reliability under harsh environments, and have been employed in electric vehicles, wind power generation, the textile industry, etc. [1, 2, 3]. However, the torque ripple caused by the inherent structure and power supply mode limits its wide application in the industrial field [4, 5]. Some advanced control strategies such as torque sharing functions (TSFs) [6, 7], direct torque control (DTC) [8, 9], direct instantaneous torque control (DITC) [10, 11], and model predictive control (MPC) [12] are effective in reducing the torque ripple. In these strategies, improving the tracking accuracy of the controller is regarded as an effective method of suppressing the torque ripple [13]. However, during the implementation of these methods, there are still some problems that need to be overcome. On one hand, the precision torque model is difficult to obtain, which directly affects the performance of torque ripple suppression. On the other hand, these techniques need to simultaneously optimize the turn-on angle, turn-off angle, and chopping level, which undoubtedly increases the difficulties of the parameter tuning. Different from these methods, unipolar current vector control (CVC) is a preferable scheme with satisfactory torque performance and can avoid complex torque model identification [14, 15]. Such advantages are drawing increasing attention from the electric machinery community [16; 17]. In [14], the current vector control strategy based on a hysteresis controller is applied in SRM to achieve the \(dq0\)-axes current regulation. On this basis, the maximum torque per ampere (MTPA) control scheme is adopted to further reduce negative torque. Similarly, in [15], the hysteresis controller is also adopted in the current loop based on the current vector control. The difference is that the hysteresis controllers are used to determine the voltage space vector applied in the next control period. In addition, to further suppress the torque ripple, a third harmonic current is injected into the reference zero-sequence current. The effectiveness of this method has been verified by experimental results. However, due to variable switching frequencies, the hysteresis controller leads to high electromagnetic interference and current ripple [5]. In [16], based on vector control, a conventional PI controller with a fixed switching frequency is used to track the reference current in the rotating reference frame. Moreover, in this method, the regulation range of the rotor speed is extended by using a space vector modulation (SVM) technology. Although a PI controller can provide a fixed switching frequency and zero steady-state error, it is still difficult to achieve a satisfactory control effect. The main reason is that there is a highly coupled relationship between different inputs of the SRM's driver in the rotating reference frame. In addition, the disturbance suppression performance of the system cannot be guaranteed by using a conventional PI controller. In [17], considering the coupling relationship, an improved current regulation scheme is proposed, which consists of a PI, decoupling, and a feed-forward controller. According to the motor model in the rotating reference frame, the values of the transient and coupling terms are compensated in the control system to enhance the control performance. Despite the good tracking performance that can be obtained by using this method when the parameters of the model are accurate, thanks to the non-linear characteristic of the SRM caused by magnetic saturation and mutual inductance, the SRM is difficult to be precisely described by the analytical expression in the rotating reference frame. As a controller with good robustness and no requirement for an accurate model, internal model control (IMC) has been widely applied to the motor driving system [18; 19; 20].