Design and Test of the Flat-Type Permanent Magnet Electromagnetic Suspension System
Shi Hongfu1, Deng Zigang2, Ke Zhihao2, Xiang Yuqing3, Zhang Weihua2
1. School of Information Science and Technology Southwest Jiaotong University Chengdu 610031 China; 2. State Key Laboratory Rail Transit Vehicle System Southwest Jiaotong University Chengdu 610031 China; 3. School of Mechanical Engineering Southwest Jiaotong University Chengdu 610031 China
Abstract：A flat-type permanent magnet electromagnetic suspension system (PM EDS) integrated with a car is proposed, and a proof-of-principle prototype, along with a 50-m long test guideway made of copper, is developed. Initially, a new topology structure is introduced, encompassing levitation magnets, guidance magnets, suspension frame, and a gap adjustment mechanism. In this design, the car utilizes car’s engine and run-up wheels to provide various initial speeds during take-off, thereby reducing the excessive cost associated with the linear motor. The levitation magnets are utilized to counteract the vehicle weight, while the guidance magnets enhance lateral stability. Furthermore, the PM EDS system undergoes experimental treatment under fixed parameters using a high-speed test rig with a diameter of 2500 mm and a maximum design speed of 600 km/h. Through equivalent experiments, the levitation, guidance, and drag forces are tested under increasing speeds ranging from 0 to 260 km/h. Reciprocating motions are used toconfirmthe vertical self-stability ability of PM EDS system. The results reveal that the levitation force is highly dependent on the levitation gap, and it is necessary to design a reasonable levitation gap according to the load demand. An excessive or too small levitation gap can trigger or exacerbate vertical instability. Subsequently, the entire system is designed and studied using three-dimensional finite element analysis (FEA), and its accuracy is verified by measurement results under identical parameters. Based on the levitation-weight-ratio (LWR) and the levitation-drag-ratio (LDR), the detailed parameters of the levitation magnets and the conductive plate are determined.Especially, as the thickness of the conductive plate increases, the levitation force initially increases then decreases, and ultimately stabilizes at a stationary value. The saturation thickness closely aligns with the skin depth dependent on the speed. The levitation force exhibits an initial increase followed by a stable value as the width of the conductive plate increases. The maximum levitation force increases by 39% compared to the initial width of the magnets when the conductive plate width matches that of the magnets. Additionally, a sample suspension frame is manufactured to connect the onboard magnets to the car and accommodate the test devices. The gap adjustment mechanism is fabricated to replace the previous shock absorber, providing ease in adjusting the installation height of the magnets. The specific screw pitch of 6 mm enables precise gap adjustment, where each complete rotation of the screw corresponds to a height increase or decrease of 6 mm. An integrated test system is constructed, which includes the installation of four HD cameras evenly positioned at the corners of the suspension frame to monitor the car wheels. Additionally, four laser displacement sensors are placed near each wheel to measure the variable levitation gap. A nine-axis sensor is mounted at the center of the vehicle body to record timely three-axis accelerations and deflection angles. Finally, the line test is conducted in two processes. During the first phase, only the levitation magnets are used to assess the guidance ability. In the other phase, both guidance and levitation magnets are employed to enhance lateral stability, while analyzing the levitation gaps, accelerations, and deflection angles within the speed range of 40 km/h to 70 km/h. The entire vehicle, weighing 1.5 t, is suspended freely in the air with gap=35 mm. The PM EDS system exhibits notable weak guidance ability, as confirmed by the guidance magnets limiting the maximum deflection angle to 10°. Therefore, the effectiveness of the guidance magnets is demonstrated. Furthermore, the measured levitation force aligned with the simulated results at a speed of 70 km/h and a gap of 35 mm.
石洪富, 邓自刚, 柯志昊, 向雨晴, 张卫华. 平板式永磁电动悬浮系统设计与实验研究[J]. 电工技术学报, 2024, 39(5): 1270-1283.
Shi Hongfu, Deng Zigang, Ke Zhihao, Xiang Yuqing, Zhang Weihua. Design and Test of the Flat-Type Permanent Magnet Electromagnetic Suspension System. Transactions of China Electrotechnical Society, 2024, 39(5): 1270-1283.
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2024, Vol. 39 
