| As a key technology to reduce energy consumption for electric vehicle,more and moreattention has been attached to braking energy recovery system, and the rate of brakingenergy recovery is the main evaluation index. Hydraulic control unit(HCU) as one of the keyactuators of the braking energy recovery system, its performance directly affects the controleffect of the system. During Braking, HCU is used to adjust the brake pressure to preventwheel locked, therefore, improves driving safety, at the same time, it also facilitates thecoordinated control between hydraulic braking and regenerative braking, increasing the rateof braking energy recovery.If the current wheel brake pressure has been known, it is relatively easy to control. Thebrake pressure could be obtained by pressure sensors which are quite precise components.Once on longer in force, will lead to inaccurate pressure value or can not get pressure value.Hardware redundancy on the pressure sensor will lead to complex system structure, andincrease system costs. Therefore, this article developed a pressure estimation algorithm torealize analytical redundancy for pressure sensor, which solved the shortcomings ofhardware redundancy.This article is the part of the key braking energy recovery technologies of major projectof “863” plan energy saving and new energy vehicles which is assumed by China’s firstautomobile co., LTD. And the main contents as follows:1. Theoretical analysis on braking energy recovery HCU. It mainly includes the analysison structure of braking energy recovery and HCU and important component of HCU;analysis on the relationship between flow characteristics of inlet valve and wheel cylinderpressure; the analysis on on-off characteristic and control characteristic of Solenoid valve;Braking energy recovery system model was built by using AMEsim software, which wasused to analyse the braking characteristics of inlet valve, delivery valve, electric hydraulicpump and low pressure accumulator; analysis on the curve of P-V. The above researches provide important theory basis for the study on the pressure estimation algorithm of brakingenergy recovery system.2. Study on the pressure estimation algorithm for the braking energy recovery system. Itmainly includes analysis on the working state of braking energy recovery system, andobtained the relationship among the master cylinder pressure, pressure simulator and wheelcylinder pressure; According to the working state of the components and P-V characteristiccurve obtained by test, the wheel pressure estimation algorithm was proposed based onunifying theory and experimental study. According to pedal displacement sensor signal andthe characteristics of pedal stroke simulator, the research on the pressure algorithm of themaster cylinder and pedal stroke simulator were carried on.3. pressure sensor fault detection and fault-tolerant control of The braking energyrecovery system. It mainly includes the analysis on the three common pressure sensor failuremodes of the braking energy recovery system and basic detection logic; According to theworking state of the braking energy recovery system, residual vector was built using thepressure estimation algorithm developed by this paper and pressure sensors signals, whichwas used to detect pressure sensor, and then using estimation value carried out fault-tolerantcontrol, that improved the fault detection accuracy, and effectively avoid the noise caused bythe uncertain factors such as system miscalculation.4. Hardware in loop experimental verification of pressure estimation algorithm andsensor fault detection and fault-tolerant control. Using MATLAB/Simulink pressureestimation algorithm model is established, and combined with prophase laboratory researchexperiment verification was carried out on the hardware in loop test bench.Results showed that the pressure estimation algorithm developed by this paper has thefeasibility and the validity. The pressure sensor fault detection and fault-tolerant controlcould be carried out. |
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