# Development of a Conveyor Cart with Magnetic Levitation Mechanism Based on Multi Control Strategies
## 2 Mechanical Structure of Magnetic Levitation Conveyor  
Figure 1 illustrates the mechanical structure of the Maglev unit, while Figure 1a provides a schematic representation of the core unit responsible for generating the magnetic levitation force. The core unit was designed with a configuration where a permanent magnet was positioned between the two cores (manufactured by SUY1), with a coil wound around the core's protrusion. Each coil consisted of 670 turns, and two coils were connected in series. Figure 1b elucidates the operational principle of the core unit. Due to the permanent magnet's magnetization along the z axis, it established a bias magnetic flux path, as indicated by the black arrow within it. The bias magnetic flux traveled from the permanent magnet to the right core, passed through the air gap, and entered the guide rail. Subsequently, the magnetic flux that entered the left core through the air gap returned to the permanent magnet. This magnetic path created an attractive force between the core and the rail, thereby providing support for the transport device. By applying a control current to the electromagnet, the strength of the bias flux could be adjusted. When a forward control current was applied, it generated a control magnetic flux in the same direction as the bias magnetic flux, consequently increasing the magnetic flux density in the air gap between the core and the rail, thereby boosting the levitation force. Conversely, when a reverse control current was applied, a control magnetic flux opposing the bias magnetic flux was generated, leading to a reduction in the magnetic flux density in the air gap and subsequently decreasing the levitation force. The core unit's support force was fine-tuned according to this principle. Figure 1: Maglev unit 3D mechanical structure and HEMS magnetic flux path. (**a**) Maglev unit 3D mechanical structure. (**b**) HEMS magnetic flux path. As depicted in Figure 2, we conducted a magnetic field analysis to elucidate the bearing capacity characteristics of the core unit. For this purpose, we employed the finite element method magnetic field analysis software JMAG-Designer ver.20.0 (provided by Japan JSOL corporation Tokyo head office). Magnetic levitation force simulations were carried out using JMAG-Designer Ver.21.0.01 zs prior to the physical measurements. JMAG is a specialized simulation software widely used for the development and design of electrical devices. It was originally released in 1983 as a tool to support the design of various devices, including motors, actuators, circuit components, and antennas [8]. Figure 2a illustrates the model used for the magnetic field analysis, and Table 1 presents the analysis conditions. In this analysis, we displaced the core unit by \(\pm\)2.0 mm in the y direction, with the center point corresponding to a 4 mm air gap between the guide rail and the core. The control current was set to three different levels: 3 A, 0 A, and 3 A. Figure 2b presents the results of the analysis. When the control current was set to 0 A, utilizing only the bias levitation force generated by the permanent magnet, the levitation force per magnetic levitation unit ranged from 633 N to 952 N as the air gap varied from 2.0 mm to 6.0 mm. Furthermore, it is observed that, by adjusting the control current from 3 A to \(-\)3 A, a levitation force ranging from 476 N to 1054 N could be achieved. Figure 2b clearly demonstrates the core unit's capability to generate variable levitation forces based on changes in both the air gap and control current. An experimental apparatus was fabricated based on the results of the magnetic field analysis to realize magnetic levitation. Figure 3a presented a photograph of the manufactured magnetic levitation unit. The magnetic levitation unit consisted of a core unit, an eddy current displacement sensor, a touchdown wheel, and a side wheel, all attached to the bracket.