Research On Brake Pedal Feel Based On Electro-Hydraulic Braking System

With the improvement of consumption ideas,consumers have higher and higher requirements for vehicle driving control performances.As one of the basic performances with the highest frequency experienced by consumers,brake pedal feel is easily recognized by consumers.For example,consumers often complain about the brake pedal feel: too heavy or soft pedal,slow brake response,bad linearization of pedal force,no confidence in braking,etc.Therefore,in the process of vehicle development,it is necessary to focus on the performances of brake pedal feel.At present,the objective evaluation of brake pedal feel is mainly represented by brake pedal force,pedal stroke and deceleration,but the subjective feeling of users cannot be directly expressed.Meanwhile,to meet the need of automobile electrification,intelligence and network connection,electronic hydraulic braking system is promising to be widely used.To shorten the tuning development on real vehicle and to reduce the cost,there is an urgent need to evaluate the subjective performance of brake pedal feel of electronic hydraulic braking system in the design and simulation stages,i.e.,to evaluate the brake pedal feel by objective experiment data instead of subjective assessment.To address the above requirements,this thesis carries out the following research on the pedal feeling of the electronic hydraulic braking system.Firstly,the subjective evaluation of pedal feel of electro-hydraulic braking system is studied.Based on the working principle of the electro-hydraulic braking system,the subjective evaluation method and evaluation index of the brake pedal feel are determined in combination with subjective evaluation of both customers and professionals.The grading method,testing site and vehicle requirements of the pedal feel of the electro-hydraulic braking system are determined.Secondly,according to the subjective evaluation method and evaluation index of the electro-hydraulic braking system pedal feel,corresponding objective test method and index processing method are proposed.Thirdly,the correlation model of subjective and objective evaluation index of pedal feel of the electro-hydraulic braking system is established by using multiple linear regression method.At the same time,the fuzzy analytic hierarchy process(FAHP)is used to establish the weight model of the subjective evaluation of the pedal feel of the electro-hydraulic braking system.Based on the correlation model of subjective and objective evaluation indexes and the weight model of subjective evaluation items,the subjective and objective consistency model of pedal feel of electro-hydraulic braking system is established.Finally,a simulation model of the pedal feel of the electro-hydraulic braking system is established.For a sedan equipped with the electro-hydraulic braking system,the subjective evaluation target of the brake pedal feel is set according to the market positioning.Then the brake pedal feel is simulated,based on which the parameters of the braking system are optimized to achieve the preset subjective evaluation target.The braking system is equipped on the vehicle,and its subjective evaluation is carried out.The validation of the model shows that there is only 2.17% of the maximum error between the actual subjective evaluations and the model outputs,meeting the error requirement of 5%.At the same time,the v-shaped research method of the brake pedal feel is proposed through the research on the pedal feel of the electro-hydraulic braking system.