## 1 Introduction
In [21], the IMC theory is used to design a current controller combining the support vector machine generalized inverse (SVMGI) for a permanent magnet synchronous motor (PMSM). Strong robustness and good dynamic performance are obtained. In [22], a novel decoupling control scheme consisting of an inverse system method and IMC is implemented on a PMSM. Compared with the conventional vector control scheme, the novel control method has better control accuracy and dynamic performance. In addition, the IMC is also applied in the induction motor driver system. In [23; 24], based on the IMC, two improved current controllers for the vector control are designed to optimize the current control performance of induction motor drives. The experimental results verify the effectiveness of both control methods. Similarly, IMC is also an eligible candidate to handle the SRMs with the characteristics of non-linearity. However, for the conventional IMC, the set-point tracking and interference suppression performance is often unable to be simultaneously satisfied by adjusting a single filter parameter. For this reason, a two-degree-of-freedom internal model control (2 DOF IMC) structure is proposed to deal with the aforementioned shortcoming, which can separate the set-point tracking response and external interference suppression characteristics of the system [25; 26]. However, such good robustness cannot be guaranteed by the invariable filter parameter of 2 DOF IMC for the SRM system. The reason is that the SRM system suffers from disturbance with time-varying characteristics, including model mismatch, parameter variation, and other unstructured dynamic uncertainties. Furthermore, different from other motors, the existence of the 0-axis current regulation increases the complexity of the controller design. Therefore, the 2 DOF IMC controller used for the SRM system needs to be further developed to achieve a more accurate current regulation. The purpose of this study is to develop a high-performance current control strategy for the SRM drive based on a 2 DOF IMC strategy. The main contributions and features of this paper are summarized as follows:1. A novel 2 DOF IMC controller is reported in this paper based on the SRM model in the rotating reference frame, which considers the coupling relationship between different axes. The proposed controller can provide good control performance by using only two adjustment parameters, and the good performance of the set-point tracking and disturbance rejection of the controller can be guaranteed simultaneously. 2. Secondly, an adaptive disturbance observer (ADO) is introduced to eliminate the time-variable disturbance. Furthermore, a stability analysis is carried out according to the Lyapunov theory, and a guideline in selecting the ADO gains is given. 3. Finally, the experimental results demonstrate that the proposed control system can provide good tracking and disturbance rejection performance. On this basis, the torque ripple can be effectively suppressed by such good current control performance. This paper is organized as follows. Section 1 introduces the SRM model in the three-phase and rotating reference frame. The control structure, design procedure, and ability analysis of the proposed 2 DOF IMC controller are also described in Section 1. Section 2 illustrates the design procedure of the ADO and the stability analysis. Section 3 presents the experimental results. Section 4 concludes this paper.