Research On Energy Management Control Strategy And Integrated Control Of Regenerative Braking System Of Hybrid Electric Vehicle

As the energy crisis and environmental pollution problems getting serious, people’srequirements of the energy saving and environmental protection of auto industry are increasing.The hybrid electric vehicle with low fuel consumption and low emissions is considered as themost promising alternatives to the traditional internal combustion engine vehicle. The design ofenergy management control strategies and braking control strategies is a significant part step ofthe control system design of hybrid electric vehicles. This subject is one of the key technologies ofhybrid electric vehicles. Many auto manufacturers around the world are conducting this research.This dissertation takes a ‘national863program’ and some university-enterprise cooperationprojects as background, takes a complex hybrid electric car as research object, conducts researcheson the base of allover analysis of the specifics, research status and development trends of hybridelectric vehicles. This dissertation research focus on the following aspects: a working torquedistribution according the driver’s torque demand of tree power sources of the hybrid drive system;developing a regenerative braking control strategy that can recovery braking energy as much aspossible under the premise of meeting the requirements of regulation and security; analyzing theworking principles of regenerative braking and hydraulic braking system and developing aintegrated braking control strategy; developing the simulation software platform of the complexhybrid electric vehicle; carrying out the simulation analysis and real car test.The torque distribution strategy is a key part of the hybrid electric vehicle control strategydesign, as well as a significant method to reduce fuel consumption. It relates to the cooperation ofthe internal combustion engine, electric machine and battery. This paper studies the structure ofhybrid electric system and analyses the working modes and energy flows to distribute the outputtorques of engine and electric machines with an equivalent BSFC method.The braking energy recover technology is one of the important methods to improve the fueleconomy of hybrid vehicles. The regenerative braking is a technique that is commonly used inhybrid electric vehicle manufacture. Regenerative braking strategy involves the braking safety, thedriver’s feeling and energy recovery rate. The design needs comprehensive consideration ofvarious factors. This paper put forward an optimal braking energy recovery control strategy on thepremise of meeting the ECE regulation’s requirements, maximizing safety and satisfying thedriver’s feelings. The electric machine’s operating points during braking are optimized with apurpose of getting the highest overall efficiency.Since the braking strength and braking stability of electric machines may not be enough insome situations, an integrated braking system with electric machines and hydraulic brake system should be used. Therefore, the cooperation of the regenerative braking control system and ABShydraulic brake control system has become a unavoidable problem that the hybrid electric vehicleresearch team must face. In this paper, an integrated braking precept of regenerative braking andABS hydraulic braking is put forward. This precept can carry out the cooperation of electricmachines and friction braking disks both in the normal braking and anti-lock braking situations.This integrated braking control system is designed to ensure the braking safety and recover part ofthe braking energy.The development of simulation platform is an important part of the hybrid electric vehiclecontrol strategy design. The simulation platform has a direct impact on the efficiency and accuracyof the controller development. In this paper, a combined methods of theoretical modeling andexperimental modeling is used to build the dynamic model in Matlab/Simulink environment. Thissimulation model is suitable for both simulation analysis and control strategy study of hybridelectric vehicles. The model includes the full vehicle, driver, controller, engine, electric machinesand other components as power source, transmission, clutch, power consumption components, andso on. Both simulation and experiment results show the correctness and validity of the model willthe accuracy requirements and following tasks’ needs.On the base of the established simulation model, the controller model is built. Then,simulation and analysis of the torque distribution strategy and braking control strategy is carriedout. Finally, a real car test system is built and tests for controller are carried into execution both onroad and chassis dynamometer. Both simulation and tests results show that the engine and electricmachines cooperate quite well under different vehicle status and driver demands. The controllercan distribute the required torque reasonably and reduce energy consumption to design target. Thecontroller can control the regenerative braking system and hydraulic braking system and recoveryabout40%of braking energy in normal braking. The anti-lock braking control strategy can ensurebrake strength and stability and recover part of the braking energy.As the key technologies of hybrid electric vehicles, energy management strategies andbraking control strategy play an important role in the development of hybrid electric vehicles. Thisstudy provides a bit contribution to improve the level of research and development of hybridelectric vehicles and achieve the independent intellectual property rights in China.