Research On Electronic-Hydraulic-Compound Regenerative Braking For Electric Vehicles

Today, energy shortage and air pollution are more and more serious. The development of low-speed micro-electric vehicles is becoming the consensus. Electric vehicle regenerative braking is important for energy conservation. An in-depth study on the regenerative braking of pure electric vehicles is carried out, and the main works in the dissertation include:The angular velocity and displacement variation of the brake pedal with time during braking is studied. The relationship of the braking strength and the pedal angular displacement is also illustrated. Based on the symbolic time series method, which is developed by information theory, chaotic time series and symbolic dynamics, the angular velocity variation of the brake pedal is analyzed. A clear distinction between the emergency braking and the general braking is found in the free clearance of the brake pedal. This method has obvious denoising effects, and the conclusion is stable and reliable, which provides a new method for the study of braking intention.A four quadrant DC chopper circuit is designed to produce regenerative current. The structure and working mode of composite power system is studied, which is composed of super-capacitors and lead-acid batteries. And the topology analysis and selection of commonly used bi-directional DC/DC are carried out.Based on the braking dynamic and braking regulations, a mathematical model on the range safe braking is established, and the brake-force distribution with maximum energy recovery and its control process are designed based on this model. To achieve this distribution and control process, a hydraulic brake system model is established firstly. Then, the high-speed on/off electromagnetic valves and hydraulic modulator are laid out in parallel. By calibrating the relationship between cylinder pressure and the duty ratio of the high-speed on/off electromagnetic valves, the wheel cylinder pressure can be controlled by them in non-emergency braking conditions. Of course, the wheel cylinder brake model must be studied. So, the constraints from electric braking force can be satisfied first, then, the need of the hydraulic braking force is determined by the allocation strategy. The wheel brake cylinder pressure is calculated through the brake model transformation, and the duty ratio of the high-speed on/off electromagnetic valve is determined by the wheel brake cylinder pressure. By controlling the duty ratio of the high-speed on/off electromagnetic valve, the hydraulic braking force can be adjusted according to need.The experimental study is one of the main works in this dissertation. The pure electric vehicle regenerative braking system test platform is established. To achieve the specified angular velocity, an instantaneous controller is designed. A new method is proposed to present the front axle braking force on tire from ground by the bench. That is to say, an anti-torque to wheel is provided by a magnetic particle clutch, which is driven by an inverter-driven induction motor. At the same time, the induction motor can follow the tracks of vehicle speed.