# Simulation of Electromagnetic Generator as Biomechanical Energy Harvester
## 3 Results and Discussion
Figure 17 shows the RMS Power. The RMS power demonstrates the continuous output power that is able to be supplied by the generator. The minimum RMS power for the generator is 3.31 W with a 100-ohm load at 360 RPM and the maximum RMS power is 14.95 W with a 100-ohm load at 800 RPM. The overall outcome parameters that have been investigated are analyzed as a case study to summarize the achieved outcome. Figure 18 shows the conceptual image of knee biomechanical energy-harvesting device placement of this electromagnetic generator. Figure 11.3 Power generated at 800 RPM. Figure 11.4 Root mean square power. Case study 1: A male user with a 6-feet 2-inch height walked at 1.34 m/s pace for 30 min by wearing this energy harvester with a 250-mm shaft length. This case study is described in the following steps. 1. As per [PERSON] et al. [30], the average knee angle transition for one complete gait cycle is 122\({}^{\circ}\), which is equivalent to 61\({}^{\circ}\) per step. 2. As per [PERSON] et al. [31], a male user with a 6-feet 2-inch height would require 1330 steps to reach a 1-km distance if he walked at 1.34 m/s speed. 3. By using the values from steps (i) and (ii), the knee angle transition per second can be computed as: knee angle transition = (1.330 steps/meter) \(\times\) 1.34 m/s \(\times\) 61\({}^{\circ}\)/step = 108.83\({}^{\circ}\)/s
4. This knee angle transition can be further amplified by using an integrated gear train mechanism. A gear train with a 1:5:5 ratio is occupied for this computation with the assumption of minimal or neglectable friction. The amplified angle is 108.83\({}^{\circ}\)/s \(\times\) 25\({}^{\circ}\) = 2720.75\({}^{\circ}\)/s. 5. The amplified angle of 2720.75\({}^{\circ}\)/s is converted to associated revolutions per minute. (2720.75\({}^{\circ}\)/s/360\({}^{\circ}\)) \(\times\) 60 s = 453 RPM. 6. Based on the simulation results, the generator at a rotation speed of 450 RPM is able to generate RMS power of 6.93 W under a 10-ohm load and 5.09 W under a 100-ohm load. This output is based on single device or per leg. 7. By using Equation (5), the user needs to apply an input perpendicular force of 0.84 N at the shaft end to actuate the generator and the equivalent energy produced for a 30-min walk will be 6.92 Wh under a 10-ohm load and 5.08 Wh under a 100-ohm load. Case study 2: A female user with a 5-foot height runs at a 4.47 m/s pace for 30 min by wearing this energy harvester with a 150-mm shaft length. This case study is described in the following steps. 1. As per [PERSON] et al. [30], the average knee angle transition for one complete gait cycle is 122\({}^{\circ}\), which is equivalent to 61\({}^{\circ}\) per step. 2. As per [PERSON] et al. [31], a female user with a 5-foot height would require 706 steps to reach a 1-km distance if she runs at 4.47 m/s speed. 3. By using the values from steps (i) and (ii), the knee angle transition per second can be computed as knee angle transition = 192.49\({}^{\circ}\)/s. 4. This knee angle transition can be further amplified by using an integrated gear train mechanism. A gear train with a 1:5:5 ratio is occupied for this computation with the assumption of minimal or neglectable friction. The amplified angle is 4812.25\({}^{\circ}\)/s. Figure 11.5 Knee biomechanical energy harvester placement. (**a**) attached to thigh (**b**) attached to hip. * The associated revolution per minute is 802 RPM. * Based on the simulation results, the generator at a rotation speed of 800 RPM is able to generate RMS power of 11.2 W under a 10-ohm load and 14.95 W under a 100-ohm load. This output is based on single device or per leg. * By using Equation (5), the user needs to apply an input perpendicular force of 1.4 N at the shaft end to actuate the generator and the equivalent energy produced for a 30-min walk will be 11.2 Wh under a 10-ohm load and 14.96 Wh under a 100-ohm load.