## 5 Movement Control Algorithm Verification Using Eccentricity
### Experimental Setup and Validation  
In the same way as system modeling using MATLAB Simulink, the system is configured as a 24 pole 72 slot 4C1M as shown in Figure 17 so that the system can be controlled by one PC [20].  
As shown in Figure 18a, a sensor base is installed in the center of the stator, and a gap sensor and a non-contact encoder sensor are placed. Finally, each inverter and controller were connected to the four divided stators and attached to the system to make an actual magnetic levitation system. Figure 19 shows the final fabricated magnetic levitation system.  
Figure 16: X-Y axis movement control output using magnetic levitation system algorithm: (**a**) X-axis movement control simulation result waveform of magnetic levitation system; (**b**) Y-axis movement control simulation result waveform of magnetic levitation system.  
Figure 17: Maglev system consisting of 4 controllers and \(1\) motor (4C1M).  
The specifications of the 4 encoders and 4 gap sensors used in the experiment are shown in Table 1. The non-contact encoder sensor used in the experiment is a MicroE Mercury 3000 incremental encoder (MicroE Systems, Bedford, Massachusetts, United States). It is a high-precision position sensor that outputs 8192 pulses per rotation and can be used with high resolution. Additionally, the ODSL9/d26-100-s12 laser sensor ([PERSON], electronic, Unterstadion, Germany) was used as the gap sensor. It is a laser sensor with a detection distance of 50-100 m and a resolution of 0.01 mm. The sensing height of the non-contact encoder is limited to a maximum of 2.55 mm. In addition, the X-Y axis movement limit has a limit of 0.2 mm in the positive and negative directions. Experiments were conducted to enable precise control within the limits of this sensor specification.  
\begin{table}
\begin{tabular}{c c c} \hline \hline
**Type** & **Product Name** & **Resolution** \\ \hline Non-contact encoder & MicroE Mercury 3000 & 8192(*fold) pulse/rotation \\ laser sensor & ODSL9/d26-100-s12 & 0.01 mm 1 \\ \hline \hline \end{tabular} \({}^{\dagger}\) Detection distance 50-100 mm.  
\end{table}
Table 1: Specifications of the sensor used in the experiment.  
Figure 19: Manufactured shaft- and bearing-less magnetic levitation system test model: (**a**) top of the test maglev system; (**b**) side view of a test maglev system with 4 inverters attached.  
Figure 18: Stator and rotor of magnetic levitation system designed for testing: (**a**) sensor base with magnetic levitation system stator and non-contact encoder sensor; (**b**) rotor with non-contact encoder scale of magnetic levitation system.  
Using this experimental equipment, it can be confirmed that the average speed of each part reaches 50 rpm according to the speed command of the magnetic levitation motor as shown in Figure 20, and the \(i_{q}\) current command is also well converged.  
Looking at the output waveforms in Figures 21 and 22, it was confirmed that the movement control using eccentricity was also output consistently according to the 0.1 mm control command.  
Finally, Figure 23 shows the three-phase current waveform applied to the stator Part A to control the rotation of the 1.33 kg magnetic levitation system rotor used in the test by 0.2 mm and 50 rpm rotation and 0.1 mm X-Y axis movement. It can be seen that the current applied for rotation, floatation, and movement control is approximately 13 A each.  
Figure 21: X-axis movement control command and output waveform (0.1 mm command).  
Figure 22: Y-axis movement control command and output waveform (0.1 mm command).