Research on Adhesion Utilization Control Strategy for Permanent Magnet Direct Drive of Rail Transit Train

Despite the absence of a transmission gear structure and large given motor torque, under wheelset slip-slide conditions, rail transit train with permanent magnet direct drive system exhibits more severe fluctuations in adhesion output torque compared with the train with asynchronous traction system, which reduce the utilization rate of wheel-rail adhesion and negatively impact riding comfort. This paper presents a rail self-adaptive adhesion control strategy. Input conditions that can best reflect the current wheel-rail adhesion state are assigned for judgments based on fuzzy rules. Generated adjustment factors are then utilized to adjust in real time detection thresholds for creep velocity, acceleration and deceleration, aligning with the current rail adhesion state. This approach enables more timely and accurate detection of slip-slide conditions, allowing for timely unloading of adhesion output torque to prevent severe slip-slide events, which can adversely affect the output torque effect and fluctuation amplitude. At the torque recovery stage, the recovery slope is adjusted according to calculated adhesion torque set values, to mitigate fluctuation amplitude. In practical applications of the proposed control strategy of adhesion utilization, the adhesion utilization rate increased by nearly 7%, and the maximum fluctuation range of adhesion output torque reduced from about 46% to about 20%. These improvements indicate enhanced traction force level in slip-slide states and better dynamics indexes of train such as smoothness and riding comfort.