# Research on Inertial Force Attenuation Structure and Semi-Active Control of Regenerative Suspension
## 2 The Structure and Working Principle of Energy-Regenerative Shock Absorbers  
The structural principle of the energy-regenerative suspension damper used in this article is shown in Figure 2a. The actuator consists of a gear rack, a box, a planetary reducer, an electric motor, an upper mounting seat, a cylinder, a lower mounting seat, etc. The prototype of the shock absorber is shown in Figure 2b. In application, the energy-regenerative shock absorber in Figure 2 is connected in parallel with the steel coil spring to form an energy-regenerative suspension. The configuration and working principle of the energy-regenerative suspension are shown in Figure 3. During vehicle operation, the road surface stimulates the vertical movement of the wheels. The vertical motion of the wheels is transmitted to the motor through the rack and pinion and planetary transmission, which is dragged to convert the mechanical energy of suspension vibration into electrical energy. The alternating current generated by the motor enters the three-phase rectifier bridge through the three-phase windings ua, ub, and UC of the motor, and becomes a direct current after rectification. The electrical energy of the motor ultimately enters the energy-consuming or absorbing module. In the energy-consuming or absorbing module, Dr and Dp are electronic switches, Rr is a resistor, Cr is the consuming mode control line, and Cp is the absorbing mode control line. The suspension controller can achieve two control modes of energy-regenerative suspension, namely energy-consuming mode and energy-absorbing mode. In energy-consuming mode, the suspension controller controls the electronic switch Dr to adjust the power consumption of the resistor Rr, forming the electromagnetic force that hinders the relative movement of the wheel and the sprung mass. In energy-absorbing mode, the suspension controller controls the electronic switch Dp to regulate the ability to absorb electrical energy, forming the electromagnetic force that hinders the relative movement of the wheel and the sprung mass. The electrical energy is stabilized within the range that the battery can charge through the voltage stabilization module, and finally, the electrical energy is charged into the battery, achieving the absorption of suspension vibration energy. Figure 2: (a) Structural principle of shock absorber; (b) shock absorber prototype. The symbols in the configuration are defined as follows: \(m_{s}\) is sprung mass, \(m_{u}\) is unsprung mass, \(m_{r}\) is equivalent inertial mass, \(k_{s}\) is suspension spring stiffness, \(k_{u}\) is wheel stiffness, \(c_{s}\) is suspension damping coefficient, \(c_{u}\) is wheel damping coefficient, \(z_{s}\) is sprung mass displacement, \(z_{u}\) is unsprung mass displacement, \(z_{r}\) is road excitation displacement. The moment of inertia \(J\) in a rotational inertial frame is similar to the inertial mass \(m\) in a translational inertial frame, both of which hinder the motion of an object. Inertial mass \(m\) hinders the translational motion of an object, while the moment of inertia \(J\) hinders the rotational motion of an object. To facilitate the analysis of the performance of the energy-regenerative suspension, it is necessary to convert the moment of inertia \(J\) in the shock absorber into an inertial mass \(m\). For a rotation radius of \(r\), the moment of inertia with uniform mass distribution is \(J\), the relationship between the moment of inertia \(J\) and the equivalent inertial mass \(m_{r}\) in a translational inertial frame is Equation (1):  
\[m_{r}=J/r^{2} \tag{1}\]  
To better convert the mechanical energy of suspension vibration into electrical energy, it is necessary to increase the speed of the motor as much as possible so that the electromagnetic damping force is sufficiently large.