Pressure Monitor And Failure Analysis Of Regenerative Braking System On Electric Vehicle

The regenerative braking system should assure the good braking feeling and the safetybesides the advantages of environment-friendly and energy saving. The coordination ofmotor braking force and hydraulic braking force, which was carried out by the brakingcontrol system through the correct and stable information of pressure, is the key to keep thebraking comfort; at the same time, the analysis of pressure failure is very important to theimprovement of braking safety.Now, a lot of study on pressure monitor and failure analysis of the regenerative brakingsystem is done by the enterprises, institutes, colleges at home and abroad. A lot of attentionis paid on the algorithm of pressure estimation in the aspect of pressure monitor. Thepressure failure analysis pays a lot of attention on the diagnosis of pressure sensor failure onthe assumption that the hydraulic components are fine. So it means a lot in breakingtechnical blockage and elevating the research ability by monitoring the pressure using thevalues of pressure sensors and estimated pressure values collectively, as well as doing thefailure analysis and diagnosis comprehensively by taking account of the hydrauliccomponents failure and the pressure sensors failure.Under the national “863”program, the paper do some study on pressure monitor andpressure failure analysis of regenerative braking system on electric vehicle on the basis ofthe researching achievements at home and aboard:1.The research on the regenerative braking system is done from hardware sketch andbraking force distribution strategy: the vehicle, the main hydraulic components and thelayout are studies on the aspect of hardware sketch; the relationship of the braking forcedistribution between the front axle and the rear axle, the hydraulic force and the motor forceof the front axle are studied, the relationship of the master cylinder pressure, the brake pedalstroke simulator pressure and the wheel cylinder pressure are clarified.2.The study of the system pressure monitor is done from hardware detecting and analytic detecting. As to hardware monitor, the pressure sensor technology is analysed, andthe working theory and technical characteristics of the piezoresistive pressure sensor are paidspecial attention; as to the analytical detecting, the algorithm of pressure estimating wasproposed, which use the relationship of brake pedal stroke-brake pedal speed-master cylinderpressure to estimate the pressure of the master cylinder. The algorithm of estimating wheelcylinder pressure was proposed based on the mass of the vehicle which take the advantage ofusing the P-V characteristics of wheel cylinder reversely. The pressure monitoring methodwas presented based on the consistency check and data fusion utilizing the value of pressuresensor taken from the hardware detecting and estimated pressure taken from the analyticaldetecting.3.The system pressure failure analysis is done from main failure mode and pressureperformance after the failure of hydraulic components and pressure sensors, then thediagnostic method was proposed taking account of the hydraulic components and pressuresensors comprehensively.4.The methods of pressure monitor and pressure failure analysis are verified on theplatform of hardware in loop test bench.From the study above, the conclusion was reached by the paper below:(1) Pressure monitor, which use the method based on consistency check and data fusionby utilizing pressure sensor measurement value and pressure estimated value can get rid ofthe unreliable data and utilize the reliable data effectively and improve the reliability andaccuracy of the pressure monitor level compared with the pressure monitor method ofhardware monitor or analytic monitor alone.(2)Pressure failure analysis, the diagnostic method utilizing the pressure characteristicsof the abnormal hydraulic components and abnormal pressure sensor overcomes thelimitation of the traditional diagnostic method which can only diagnose the failure ofhydraulic component or the pressure sensor alone. Furthermore, the method can diagnose theconcrete failure position and failure type comprehensively.