Study On Assisted Strategy Of Electric Booster For Braking System

Auto electronic technology is the inevitable trend of the development of automotive technology.After the electronic technology has been widely used in the engine,transmission,steering and suspension system,the use of electric power assisted brake are gradually replacing the traditional vacuum booster braking system both at home and abroad.The electric power assisted braking system uses the electric motor to provide the power directly.And the assisting power is controlled by the electronic control unit.It has the advantages of power adjustable,environmental protection,energy saving and convenient maintenance etc.And it is one of the hotspots and leading technologies of automobile technology development.The study on the brake system of domestic enterprises is still in the vacuum booster stage.In order to enhance the high-end brand shaping ability of domestic electric power assisted braking system,according to the needs of enterprise,the electric booster for vehicle braking system is studied,and a motor assisted strategy of combining the braking intention and fuzzy control is proposed.Firstly,scheme of electronic power assisted braking system and motor controller is designed.According to whether the pedal force can be transmitted to the master cylinder,the mechanical structure is divided into two kinds of decoupling and non-decoupling.And the coupled design is further provided with emergency braking devices to prevent the failure of power motor,in considering hazardous circumstances that pedal force cannot be transmitted to master cylinder which lead to braking failure.Also,the hardware circuit of the DC motor controller is designed,including the minimum system,drive circuit,AD sampling and communication circuit design.Secondly,brake pedal feel is simulated.The simulation model of hydraulic braking system components is setup in AMESim,and the simulation model of power motor and brake pedal is setup in Simulink.The relationship between brake pedal force,pedal displacement and braking deceleration is obtained by the joint simulation of AMESim and Simulink.Next,the evaluation method of brake pedal feel index is introduced to objectively evaluate brake pedal feel.It is verified that the braking scheme,the ratio of transmission and the response of the selected DC motor driven by controller can make the driver obtain a good brake pedal feel.Finally,a assisted strategy of combining the braking intention and fuzzy control is proposed,and the assisted strategy is verified by hardware-in-the-loop simulation.Based on the analysis of driver’s braking intention and braking intensity,a assisted strategy is proposed that the direction of motor assist can be controlled based on recognition of three braking situations by depressing the pedal,releasing the pedal and keeping the pedal and the motor power can be controlled based on fuzzy control.Two hardware-in-the-loop simulation experiments are carried out to verify the assisted strategy of motor.