# Design of a 120 W Electromagnetic Shock Absorber for Motorcycle Applications
## 1 Introduction  
In recent years, energy harvesting from ambient vibration has received significant attention, resulting in many publications [1, 2]. For example, there are many options, such as wind or earthquake-induced building vibration, wind or traffic-induced bridge vibration, and wave-excited offshore structures, for which the vibration and associated energy can be considerable [3, 4, 5, 6, 7, 8, 9, 10]. Passive damping techniques have been utilized to reduce vibration by dispersing kinetic energy into waste heat through various forms of dampers. Rather than dissipating the vibration energy as waste heat, an interesting research direction is to use vibration to harvest large-scale electric energy. A shock absorber, an energy-dissipating device, is used in parallel with a suspension spring to reduce the vibration excited by road irregularities, or during acceleration and braking. For many years, energy harvesting shock absorbers (EHSAs) have been considered and widely commercialized as the major energy recovery application in electric vehicles (EVs) [11, 12]. In the next few years, applications for energy harvesting from vehicle suspension systems are likely to become widespread due to their great potential for energy recovery. EHSAs are categorized according to their working principle, with piezoelectric and electromagnetic EHSAs, which are now the most common. On the one hand, the piezoelectric EHSA produces electrical energy using a piezoelectric substance. Since they can produce damping forces similar to those of conventional suspensions, they must be used in combination with a primary damper. This limits the ability of the technology to recover energy. However, the EHSA piezoelectric technique is not the most effective for recoveringlarge amounts of energy from suspensions [13]. Due to the lack of ability to generate forces, these EHSAs must operate in parallel with conventional suspensions. Therefore, it is restricted to the supply of external sensors or the operation of low-power electrical devices. In contrast, electromagnetic EHSAs have attracted the attention of researchers over the last two decades. This approach includes both linear and rotational electromagnetic EHSAs. Through electromagnetic induction, the linear electromagnetic damper transforms the kinetic energy of the vertical oscillations of the vehicle directly into electrical energy. The main difference between it and the rotary electromagnetic damper is that the latter requires a transmission system to transform the linear oscillating motion in the generator into a rotating motion. A hybrid suspension system based on a linear direct current (DC) generator was established in [14]. The aim of the study was the reduction of energy consumption in active suspensions. The goal of the study was to reduce energy usage in active suspensions. A linear electromagnetic energy harvesting shock absorber (EHSA) prototype for energy recovery employing a vehicle suspension system has already been created in [15]. Due to the coil and magnets utilized in the suspension, this system became heavy. Numerous linear electromagnetic actuators for energy recovery in large-scale vehicle damping systems are designed and optimized in [16]. They obtain up to 3.8 times the efficiency of the model described in [15] with this modification. This system could recover 2.8 W of electricity at a velocity of 0.11 m/s. The system is intended to provide up to 33 W of power at 0.25 m/s with a damping coefficient ranging from 1680 to 2142 Ns/m. Because of the heavy weight of a linear electro-magnetic EHSA, research [17; 18] has been conducted to optimize the relative speed between the magnetic field and the winding, therefore enhancing efficiency and lowering weight. The recovered power was approximately 16 W at 0.25 m/s and approximately 64 W at 0.50 m/s. [PERSON] and [PERSON] [19] developed optimal designs for an external permanent magnet tubular machine for harvesting energy from vehicle suspension systems, with maximum and average recoveries of 339.95 and 96.96 W, respectively.