| Drivers of commercial vehicles need to work for long hours in the cab,and are greatly affected by vehicle vibrations.Commercial vehicles usually use passive suspensions that have poor vibration reduction effects,which has led to many drivers suffering from related occupational diseases.Passive suspensions cannot simultaneously balance comfort and handling stability,and once the suspension parameters are determined,they cannot maintain good performance under different road conditions and speeds.Compared with semi-active suspensions that can only generate forces opposite to the speed direction to consume vibration energy as negative work,active suspensions can generate active forces that can do positive work as well as negative work,which can better improve ride comfort.The idea behind this article comes from electromechanical analogy.The concepts of mass,spring,and damping in mechanics have the same mathematical expressions as those of inductance,capacitance,and resistance in electrical circuits.Therefore,these quantities are also named using the concept of impedance in electrical circuits.Impedance is a property of a system that reflects the relationship between environmental forces and the system’s motion.Impedance control involves giving a virtual impedance to the contact between the system and the external environment,and the parameters in the control algorithm have practical physical meanings.After impedance control was proposed in the 1980 s,it was widely used in robotic arms,but there have been few studies on applying impedance control to suspensions.Compared with other control algorithms that change the damping of the suspension system,impedance control can also change the equivalent mass and stiffness of the suspension system.Therefore,applying impedance control to commercial vehicle seat suspensions is a meaningful work.This article is divided into three parts: the development of an active seat suspension model,road excitation,and impedance control algorithm,and the verification of a scaled suspension experiment.The main contents and conclusions are as follows:First,a random road surface,a convex road surface,and a sweeping sinusoidal road surface are established as road excitations,and the commercial vehicle model is simplified into a six-degree-of-freedom model.The input displacement of the driver’s cabin under different road excitations is then plotted.Next,considering the damping force change caused by the vertical vibration of the seat,the equivalent damping force of the damper is derived.The shear-type seat structure is analyzed,and the relationship between the vertical force of the suspension and the output torque of the motor is established through the conversion of the motor’s rotational motion into the vertical motion of the seat.The rotational motor model is established based on the loop voltage balance equation.The working mode of the motor is analyzed,and a scheme for semi-active suspension control under the short-circuit braking motor working mode is proposed.The stiffness and damping parameter ranges of the suspension are obtained by analyzing the frequency domain characteristics of the seat suspension,which improves the efficiency of parameter selection in impedance control.Subsequently,the control strategies of impedance control,including force-based impedance control and position-based impedance control,are introduced.Active impedance controller,semi-active impedance controller,and variable impedance controller are designed.The function of impedance parameters and suspension motion states are designed according to the influence of impedance parameters on suspension performance indicators.Particle swarm optimization algorithm is used to optimize the impedance parameters.Considering the change of mass on the seat suspension spring,recursive least-squares method is used to estimate the mass on the spring.Then,the simulation results of impedance control,variable impedance control,LQR control suspension,and passive suspension in time and frequency domains are compared.Finally,a scaled suspension test rig was built,including an excitation motor power supply and control system,a test rig,and an actuator motor power supply and control system,to verify the different impedance characteristics of the suspension under random and sinusoidal road excitation,respectively. |
