## 5 Calculation Results and Discussion
### Increase in Magnetic Field  
Based on experimental tests and numerical calculations, the highest torque value was obtained at 12 Nm from the experimental process using a reference-based design. In reality, the braking requirement can be defined by using the braking torque in order to reduce the vehicle speed. In this case, the braking torque is calculated as the torque required to reduce the vehicle speed from 17 to 5.6 m/s, and it is 52.1 Nm. Therefore, the use of the ECB can reduce 23% of the braking torque required by the braking system. It is considered that there are several ways to improve the performance of the ECB and still retain the compactness of the system, including the number of coil windings, the number of electromagnets, and the electric current; therefore, the ECB can be applied for light vehicles including motorcycles. The influences of these parameters are analyzed and shown in this sub-section. The numerical simulation for analyzing these parameters was conducted under the conditions of an air gap and rotation speed of 1 mm and 450 rpm, respectively. The magnetic field is generated by using a coil that is powered by an electric current. The amount of magnetic flux produced by a coil depends on the amount of electric current given. Therefore, the amount of required torque can be regulated by changing the amount of electric current. Figure 8 shows the correlation of the number of coil windings and the generated braking torque. An increase in coil windings results in a higher braking torque. However, this increase in coil windings also resulted in a larger system size. In addition, Figure 9 shows the correlation of electric current and generated braking torque. Similar to the effect of the number of coil windings, a high electric current also leads to a higher braking torque. Unfortunately, a higher electric current potentially causes an increase in heat during braking, leading to a risk of overheating. Both the number of coil windings and the electric current clearly influence the braking torque [30], and it is important to set optimum values for each braking system. The number of electromagnets is also considered to potentially improve the braking performance. In this study, difference numbers of electromagnets were analyzed, starting from one to four electromagnets. Figure 10 shows the configuration of the magnet used during numerical calculation. Figure 10 shows the correlation between the number of electromagnets and the generated braking torque. It is clear that the increase in the number of magnet significantly improves the braking torque. Figure 11 shows the obtained contours of the magnetic field for two- and four-magnet configurations. By increasing the number of electromagnets, the distribution of the magnetic field throughout the disc brake becomes larger. By increasing the number of electromagnets, the size of each braking unit can be kept small and compact, while fulfilling the required braking torque. Figure 9: Effect of electric current on the braking torque (where the number of coil windings is fixed at 360). It is important to note that the increase in the number of electromagnets should avoid any interaction risk of the magnetic field generated by each magnet. In addition, it is necessary to consider the space left for the installation of conventional braking systems. As shown in Figure 12, although using four electromagnets, the interaction of the magnetic field among the poles can be avoided. The interactions of the magnetic field can result in magnetic field leakage. The use of four electromagnets can generate a 48.8-Nm braking torque. In addition, reducing the vehicle's speed from 60 to 20 km/h requires 52.1 Nm (a vehicle weight of 100 kg). The use of the ECB with this design can reduce 93.66% of the braking torque required by the braking system compared to without an ECB. By flowing an electric current of 30 A, setting the number of coil windings to 540, and using two electromagnets, a higher braking torque than is required can be generated.