Construction Of Electromagnetic-Mechanical Coupled Regenerative Braking System And Research Of Active Stability Control For Electric Vehicles

The technology of electric vehicles was an effective way to solve the problems of energy shortage and pollution. And regenerative braking was one of the preponderant technologies, which can achieve efficient recovery of braking energy and improve energy efficiency for the electric vehicle. There were two sets of separate braking systems existing in braking energy recovery technology, one was hydraulic or electro-mechanical friction braking system, and the other was regenerative braking. But they needed to be controled coordinately and independently in the process of braking. However the current regenerative braking system remains a bunch of disadvatages, for example, it had far more control parameters than need and consumed actuation energy. Meanwhile, it was difficult to control concertedly and the discrete on-off control of traditional ABS could lead to the chattering with high frequency, etc. Based on technical actuality and research results of regenerative braking and distributed driving, according to electromagnetic theory and analysis of braking energy flow, and combining modern advanced mechatronic control technology, a new-type electromagnetic-mechanical coupled regenerative braking system was proposed(referred to as EMCB). It overcame the independent deficiencies on each other in two braking systems, and integrated the advantages of electro-mechanical braking, regenerative braking of in-wheel motor and direct distributed driving. When providing electromagnetic braking and energy feedback, EMCB actuated friction braking and realized electromagnetic-mechanical coupled regenerative braking. Then the first generation prototype was designed and completed. The coupled mechanism of electromagnetic-mechanical coupled regenerative braking system was analyzed and verified by self-established test platform, which included electromagnetic braking and coupled braking test bench, measurement and control system of software and hardware, and active safety test bench of the vehicle.EMCB system not only simplified the structure of braking and driving system of electric vehicles remarkably and improved energy efficiency, but also provided a new technical means for stability control and unmanned drive. A braking force distribution strategy and continuous-state control strategy of anti-lock braking was proposed based on ideal curve of braking force distribution and adaptive sliding mode control. The results showed that, the braking force distribution strategy could realize practical braking force distribution curve which agreed with I-curve well under low and middle braking strength, and it made slip and wear of front and rear wheels more consistent and reduced the differences effectively between the longitudinal characteristics of the tire. The braking stability and utilization adhered coefficient of road was ensured and improved. The deficiency of conventional ABS discrete on-off control was ameliorated by continuous-state control during anti-lock braking conditions. The continuous-state control strategy had better responsiveness, robustness and slip control performance. The longitudinal stability control strategy improved braking comfort and recovery efficiency to increase the driving range of electric vehicles effectively. With the vehicle dynamic model of lateral force limitation, lateral stability control strategy of non-limit adhered state was proposed based on direct braking input distribution and fuzzy-compensation control. The results showed that, the designed double fuzzy controllers and wheel distribution compensator had take handling stability and following trajectory into account, and avoided excessive correction and interference on driver. And the proposed fuzzy-compensation stability rnntrnl algorithm had better robustness and yaw stability, which reduced the tracking error of vehicle slip angle and yaw rate effectively. The electric vehicle stability control strategy integrating regenerative braking not only can increase the driving safety of electric vehicles, but also had a good recovery efficiency.According to the latest research results of active vehicle stability control and self-driving technologies at domestic and overseas, the kinematic mechanism and dynamic characteristic of active-limit adhered state is revealed through studying and analyzing vehicle steady sideslip motion and aggressive maneuvers, such as handbrake cornering, pendulum-turn and trail-braking which were widely used in rally races. On this account the concept of cognitive frontier and hypothesis of energy conversion was presented. Aimed at the electric vehicle that integrated braking and driving by wire system with four in-wheel motor, the vehicle stability control idea of active-limit adhered state was advanced on basis of the cognitive frontier of unmanned vehicle and law of energy conversion. Under the conditions of large steering angle and hairpin corner the lateral stability control mechanism of active-limit adhered state, which is from the non-limit adhered state to limit adhered state and limit adhered state back to non-limit adhered state, was preliminary explored with modified nonlinear dynamic model of the vehicle. It provided some reference and possible solution for active stability control of the unmanned vehicle.