| With the upgrading of "energy-saving and new energy vehicles" industry, the researches on vehicle energy flow and its relationship with vehicle performances have received more and more attentions. Meanwhile, studies on powertrain energy flow and regenerative braking system have been started for a long time and rapidly developed. However, the research on suspension system energy flow and its impact on vehicle performance was just started. Suspension system is one of the most important systems in the vehicle chassis, which plays the role of supporting the vehicle body, isolating the vibration caused by the uneven road, and also, has a direct impact on the ride comfort and driving safety.For off-road vehicles, due to the poor driving conditions, the dampers’ reciprocating movement is very violent, the damping oil produces a lot of heat, resulting in worse damping characteristics, decreased ride comfort and reduced suspension service life. Therefore, it is very important to study on the energy conversion mechanism of the vehicle suspension system, and to explore the Regenerate Mechanism and systems to harvest the vibration energy of the suspension.In this dissertation, an off-road vehicle suspension system was chosen as the research object, a mechanism model of the traditional suspension energy conversion was developed, the influences of the damper temperature rise characteristics on suspension performance were discussed; via the suspension vibration model, the energy regeneration mechanism and the potential use were studied, and performance evaluation index of off-road vehicle regenerative suspension system was put forward; for the off-road vehicles, which usually have great deadweight and drive on bad road conditions, a series of pump energy regenerative suspension system configuration were designed innovatively, which realized to convert the reciprocating shift of the suspension vibration to large unidirectional circulationoil flow, reduced the damping oil temperature rising and improved the generator efficiency; what’s more, this layout made the suspension to have a considerably large controllable range of non-symmetry recovery / compression damping forces; based on the previewed road information and multiplexed model predictive control, a semi-active regenerative suspension control algorithm was developed by considering the system hardware constraints, the ride comfort and energy efficiency of off-road vehicles, which improved the ride comfort, driving safety and energy recovery efficiency. The main research contents and conclusions are summarized as follows:(1) Mechanism analysis and experimental study on the energy conversion of vehicle suspension system. The shock absorber thermodynamic model was divided into three parts: the heat conduction process model, convective heat transfer process model and the radiative heat transfer process model, and the damping oil density- temperature properties and viscosity-temperature properties were also considered in these models. Via this model, the passive damping energy dissipation mechanism and oil temperature rising mechanism were studied, and the impact of the shock absorber oil temperature rising characteristic on the suspension performance was analyzed; finally, the temperature rising characteristic test under shock absorber sustained loading and damping characteristic test under different test temperatures and loading speeds were conducted to verify these models and mechanisms.(2) Theoretical study on suspension vibration energy modeling and harvesting potential. Based on the classical quarter car, the suspension of instantaneous power prediction model was established; combined a random road generation tool, the suspension vibration energy harvesting potential caused by the uneven road excitation was detailed discussed under various vehicle velocities and road grades, the results show that the off-road vehicle suspension has a better energy recovery potential; finally, based on comprehensive consideration of the off-road vehicle driving characteristics and different ride comfort evaluation criteria, an off-road vehicle regenerative suspension performance evaluation method was put forward, which considers both ride comfort and regenerative characteristics.(3) Configuration design, performance analysis and prototype development of the pumping regenerative suspension for off-road vehicles. According to the large weight and poor driving conditions of off-road vehicles, a series of pumping regenerative suspension layouts were innovative designed, and based on the pumping twin-tube regenerative suspension system, theoretical modeling, parameter analysis and prototype development were conducted. Thisscheme can convert reciprocating suspension vibration movement into one-way oil flow, and drive the hydraulic motor and generator to rotate unidirectional which will improve the generator efficiency and working reliability; non-symmetry recovery/compression damping force required by suspension was also achieved; the scheme has a considerable large controllable range of damping force, which makes it a good hardware basis for semi-active control. A prototype was developed by carefully designing and selecting its key components(actuator, regenerative module and charging management module); based on the particularity of this prototype, regenerative characteristic test system was designed and manufactured, by which various experiments were conducted to research on the damping characteristic, temperature rising characteristic, controllable damping range and energy regenerative characteristic.(4) Hardware in the loop experimental study on the off-road vehicle pumping regenerative suspension prototype. In order to verify the actual performance of this prototype during real vehicle condition, a HIL test rig was designed and manufactured and the HIL tests were conducted combined with a real-time vehicle dynamics model; under random road and pulse excitations, the different work states(maximum regenerative, target damping properties and follow-up) of this prototype were experimentally researched in regard of damping characteristics and harvesting characteristics.(5) Research on the control algorithm of the semi-active regenerative suspension based on the road preview information. Firstly, the road preview implementation method was analyzed and a four-wheel random road model and a semi-active control based seven DOF vehicle model were established. Secondly, a multiplexed model predictive controller was designed in consideration of hardware constraints of the regenerative suspension, ride comfort and regenerative efficiency. Finally, by selecting skyhook damping control and passive suspension as comparison, the designed control algorithm was verified in random road input and pulse input conditions. The results show that this controller can improve the vehicle ride comfort, at the same time, have a high regenerative efficiency and fuel economy.The main innovations of this dissertation are organized as:(1) The suspension system energy transfer and regenerate mechanisms were revealed, which provides a theoretical basis for the regenerative suspension design.(2) A series of pumping regenerative suspension layouts were innovative designed and theproposed prototype realized to convert the reciprocating shift of the suspension vibration to large unidirectional circulation oil flow, reduce the damping oil temperature rising and improve the generator efficiency, and also have a considerably large controllable range of non-symmetry recovery / compression damping forces.(3) A control algorithm of the semi-active regenerative suspension based on the road preview information was proposed, which can improve the vehicle ride comfort, at the same time, have a high regenerative efficiency and fuel economy. |
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