Configuration And Control Method Of Active Suspension For Lunar Mobile Laboratory

The surface of the moon is uneven,and the moving system on the surface of the moon is strongly impacted.Due to the low gravity acceleration of the moon,the moving system is easier to get off the ground than the ground vehicle.When the wheels are completely off the ground,the whole manned lunar rover will fly from the surface of the moon,and the lunar rover will lose its handling stability,resulting in safety risks such as steering wheel failure and roll-over.As the object of the lunar mobile laboratory is the astronauts,the safety requirements of the lunar rover should be put in the first place,so it is urgent to control the wheels not to leave the ground in the process of driving.Through researching,it is known that the active suspension of ground vehicle can control the acceleration of vehicle body through the actuator providing the active force.According to the principle of force and reaction force,the active suspension not only provides the active force to the vehicle body,but also provides the active force to wheels.Therefore,it is feasible to introduce the active suspension of the ground vehicle to solve the problem of the lunar rover.In order to design an active suspension with reasonable configuration and closed-loop control,this paper needs to study from four aspects: model simplification,configuration and parameter design,control method and dynamic simulation analysis.Firstly,the preliminary design of passive suspension for lunar mobile laboratory is clarified,and the single wheel passive suspension model is simplified to a two mass two degree of freedom vibration model,and its leverage ratio,equivalent spring stiffness and equivalent damping coefficient are calculated.According to the dual mass vibration model,the dynamic equations are listed.Finally,the statics and kinematics of the simplified model are verified,and the range of lever ratio of single wheel passive suspension is solved.Secondly,the actuators and dampers of the active suspension are connected in series or in parallel.The energy consumption is compared respectively.Finally,the series type is selected as the active suspension configuration.According to the solid model of single wheel passive suspension,the model is established in the simulation dynamic software Recur Dyn.Considering the influence of natural frequency on the acceleration of vehicle body,and the influence of damping ratio of shock absorber on the acceleration of vehicle body and the wheel off the ground,the damping parameters of vehicle body considering the ride comfort and handling stability are determined.And then according to the simplified model of single wheel passive suspension of lunar mobile laboratory,the dynamic equations of off ground and non-off ground are listed respectively.According to the equations,the off ground conditions of single wheel passive suspension can be obtained.Through theoretical derivation,two kinds of characteristics can be obtained,and two control strategies are designed based on the two characteristics.By comparing the advantages and disadvantages of the two,it can be determined that the final control strategy is to achieve the goal of zero body acceleration by controlling the linear speed of the electric cylinder,so as to control of the wheels not leaving the lunar surface with PD controller.The active suspension with or without shock absorber is discussed,and the necessity of shock absorber in controlling body acceleration in active suspension is clarified.Finally,the control system model is established in the dynamics simulation software Recur Dyn,and the parameters of PD control are adjusted.Set three kinds of excitation of single wheel passive suspension off the ground,the conclusion is that the active suspension is not off the ground.Therefore,the correctness of active suspension configuration and control method can be verified.It combined with the fuzzy control principle to optimize the design of PD controller.The optimized controller is helpful to improve the ride comfort of the car body.