## 1 Introduction  
Recently, with the development of technology and popularization of electric vehicles (EVs), interest in autonomous vehicles has increased [1; 2; 3; 4; 5; 6]. Autonomous vehicle technology has many advantages, such as reducing traffic accidents, establishing a more efficient transportation system, greatly reducing social costs caused by traffic accidents or traffic congestion, and reducing car-related crime; thus, autonomous vehicles can become the mainstream transportation method in the future. Accordingly, several studies have been conducted on autonomous vehicles. However, accidents involving autonomous vehicles occur frequently because the technology is still developing [2; 3]. For autonomous vehicles, there is no driver intervention; therefore, it is necessary to secure vehicle safety technology in case of an emergency. Accordingly, the importance of fail safety and redundant systems in automobiles is increasing. Recently, various redundant systems that use two motors have been studied to ensure the safety of autonomous vehicles [7; 8; 9]. Studies on redundant systems include a redundant steering system driven by connecting two motors to one axis [7]; a redundant driving system of an EV containing two motors, two batteries, and a dual inverter [8]; and two motors and redundant robot systems comprising two gearboxes [9]. A system using a DWM with one motor was developed [10; 11; 12]. DWMs are applied in various fields, such as electronic brake systems [10], aerospace fields [11], and electric power steering systems [12]. An advantage is that a redundant system can be implemented with one motor by applying a double-winding structure to one motor. However, in the case of a DWM that separates one motor into two, additional overheating problems may occur owing to increased current consumption because half of the motor must be driven in case of a failure. To solve this problem, a compensation method for the increase in current consumption in the faulty mode has been proposed, which involves increasing the stacking length of the DWM [13]. However, this has a problem in that the output power of the motor and the response performance of the IEB system deteriorate under the same current usage condition because resistance and BEMF increase as the stacking length increases. To simultaneously solve the overheating problem in the faulty mode and the output performance degradation in the normal mode of the DWM, it is necessary to investigate a new alternative that only changes the winding connection state for each operation mode without changing the motor design specifications. As a representative method of changing the winding connection state for each operation mode without changing the motor design, there is a winding switching (WS) [14; 15; 16; 17; 18; 19; 20]. [PERSON] et al. [14; 15] proposed a cumulative/differential WS method to obtain a constant power speed range using a three-phase single inverter. [PERSON] et al. [16] designed two modes of operation for a PMVM to improve efficiency and wide-speed-range operation using WS. In mode-one, high torque was achieved with the stator winding connected in a wye configuration. In mode-two, a wide speed range was achieved with the stator winding connected in a wye-delta configuration. [PERSON] et al. [17; 18] proposed a novel winding scheme using WS to generate an additional sub-harmonic magnetomotive force (SH-MMF) component for the brushless operation of a wound-field synchronous machine. [PERSON] and [PERSON] et al. [19] designed a dual-mode brushless wound rotor synchronous machine (DBL-WRSM) for a high starting torque using WS to achieve a higher starting torque than a conventional brushless wound rotor synchronous machine (BL-WRSM). [PERSON] et al. [20] proposed a design method for a wound field synchronous motor (WFSM) employing a dual-stator winding and winding connection change circuit. Accordingly, WS can be used to change the winding state, which can change the number of parallel circuits or change the delta connection to the Y connection.