# Research on Inertial Force Attenuation Structure and Semi-Active Control of Regenerative Suspension
## 5 The Verification of HVRS Suspension Characteristics  
### Damping Force and Control of Energy-Regenerative Shock Absorber  
There are two schemes for the damping control of energy-regenerative suspension. One is to adjust the damping coefficient by controlling the values of different dissipation resistances; the vibration energy of the suspension is ultimately dissipated through the heat generated by the resistance. The second is to adjust the damping coefficient by controlling the value of the recovered electrical energy, but the adjustment effect of the damping coefficient is related to the state of energy storage devices such as supercapacitors and batteries, and there are unstable factors. In order to study more accurately the beneficial effects of the new configuration on the energy feedback suspension, this paper adopts the scheme of controlling the dissipation resistance to achieve damping coefficient adjustment.  
The damping control principle of the energy-regenerative shock absorber is shown in Figure 8. This paper adopts the mode of controlling electrical energy dissipation to control the load resistance \(R_{r}\), thereby achieving the adjustment of damping force. The suspension controller sends a PWM control signal to the electronic switch Dr through the control line Cr, and the duty cycle of the PWM signal determines the conduction time of the load resistance \(R_{r}\). The duty cycle of PWM is set to \(d_{u}\), and the value range of du is from 0% to 100%. When \(d_{u}=0\%\), the load circuit of the energy feedback damper is equivalent to being disconnected, and the dissipation resistance \(R_{d}\) is infinite. When \(d_{u}=100\%\), the dissipation resistance of the energy regenerative damper is \(R_{r}\). Therefore, the calculation formula for the dissipation resistance value \(R_{d}\) of the shock absorber under PWM control is Equation (25).  
\[R_{d}=R_{r}/d_{u}\;\;d_{u}\in(0,1] \tag{25}\]  
According to paper [12; 30; 12], the damping coefficient of the energy-regenerative damper can be obtained as Equation (26), where \(k_{e}\) is the back electromotive voltage constant, \(k_{t}\) is the torque constant, and \(R_{m}\) is the internal resistance of the motor.  
\[c_{s}=\frac{30k_{e}k_{t}i_{r}^{2}}{\pi r_{S}^{2}(R_{d}+R_{m})} \tag{26}\]  
Using the parameters in Table 4, according to Equations (25) and (26), the variation curve of the dissipation resistance when the PWM duty cycle changes is shown in Figure 9a, and the variation curve of the suspension damping coefficient is shown in Figure 9b.  
Figure 8: Damping control principle of energy-regenerative shock absorber.  
From Figure 9a, it can be seen that the PWM duty cycle \(d_{u}\) can adjust the dissipation resistance of the shock absorber, which is the basis for achieving semi-active suspension control. The variation of dissipation resistance is not linear with the variation of the PWM duty cycle. When the duty cycle is less than 20%, a small change in the duty cycle will cause a significant change in the dissipation resistance value.  
From Figure 9b, it can be seen that the PWM duty cycle can adjust the damping coefficient of the suspension, and it essentially changes linearly, which is very beneficial for the control of the semi-active suspension. By adjusting the PWM duty cycle \(d_{u}\), the damping coefficient can be quickly adjusted to the desired value.