| The damping force of a traditional hydro-electric and regenerative shock absorber can not be adjusted according to work condition,which limits dynamics of the suspension system.In this paper,a DC-DC converter was added into energy regeneration circuit of the hydro-electric and regenerative suspension so that the controller can change damping force of the shock absorber by adjusting switch signal duty ratio of the MOS pipe,and the suspension can obtain a semi-active control.Besides,the designed semi-active suspension can change its work modes according to road frequency,so that the suspension can meet the dynamics demands of different work modes while recycling energy.Research contents of the thesis paper are listed as follow:Firstly,a mathematic model of the suspension was built.According to analysis of the regenerative circuit,it was proposed that damping force of the regeneration shock absorber can be adjusted by changing switch signal duty ratio of the MOS pipe.As a result,the actual damping force can track the ideal damping force and a semi-active control of the suspension could be obtained.The road-frequency adaptive semi-active control strategy of the hydro-electric and regenerative suspension was designed.Work modes of the suspension were defined based on road frequency,and the double-ring hybrid controller was designed which consisted of a skyhook-groundhook controller and a fuzzy PID controller.The skyhook-groundhook controller could compute the ideal damping force according to the vehicle state variables while the fuzzy PID controller output a switch signal duty ratio to the MOS pipe according the difference value between the ideal damping force and the actual damping force,and the semi-active control was obtained.Then,work modes of the semi-active suspension were defined based on road-frequency,and the double-ring hybrid controller was designed.The inner ring was a skyhook-groundhook controller which computed the ideal damping force.Optimal skyhook damping coefficient and groundhook damping coefficient were obtained base on the optimized LQG active controller so that the ideal damping force could be obtained.What is more,a kalman filter of the semi-active suspension was designed which provided state variables,i.e.vehicle body velocity and wheel velocity,for the skyhook-groundhookcontroller.In addition,the road frequency was estimated with the first-order zero-crossing detection method,so that the semi-active suspension could switch its work mode according to the frequency.The fuzzy PID damping force tracking controller of the semi-active suspension was designed,and the difference value between the ideal damping force and the actual damping force was input into the fuzzy PID controller so that the controller could output an appropriate switch signal duty ratio to the MOS pipe to make the actual damping force track the ideal damping force.Compared with a passive suspension,dynamics and energy regeneration of the hydro-electric and regenerative semi-active suspension in single work mode and overall situation were studied by simulation to verify reliability and stability of the semi-active suspension system.Finally,the bench test of the hydro-electric regenerative semi-active suspension was conducted to study its dynamics and energy regeneration in single work mode and overall situation.Experimental result was consistent with that of simulation,which verified validity of the simulation result and feazibility of the hydro-electric regenerative semi-active suspension.To sum up,in this paper,the DC-DC converter was added into the hydro-electric and regenerative suspension,in which the shock absorber actual damping force could track the ideal damping force by adjusting duty ratio of the MOS pipe switch signal to achieve system semi-active control.The road-frequency adaptive semi-active control strategy was proposed based on the established dynamic model of the hydro-electric and regenerative suspension.The double-ring hybrid controller consisting of a skyhook and groundhook controller and a fuzzy PID controller of the semi-active suspension,as well as the frequency recognition method,was designed.Compared with the passive suspension,body acceleration of the semi-active suspension in comfort mode decreased by 27.91%,and wheel dynamic load in sport mode decreased by 32.65%.In aggregative mode,body acceleration decreased by 18.87% while wheel dynamic load decreased by 29.89%.And the average energy regeneration power reached to 46.94 W.Thus,dynamic performance of the hydro-electric suspension was remarkably improved and the energy was regenerated. |
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