Research On Sensor Fault Diagnosis And Fault-Tolerant Control Of Integrated Brake Control System

The development of automobile intellectualization and electrification puts forward new functional requirements for brake system.Under the trend of development,the integrated control brake system has become the mainstream of the development of brake system with its highly integrated structure and function.However,due to the highly integrated function and structure,the functional failure probability of the integrated brake system increases significantly.In order to avoid accidents,it is necessary to ensure the functional safety of the integrated brake system.The sensors are important parts of the integrated brake system,and its normal operation is the premise of the effective control of the system.If it fails,it will lead to the failure of the brake system and cause potential danger.Therefore,it is of great significance to carry out functional safety analysis of integrated brake system,design safety mechanism for the sensors,and do research on fault diagnosis and fault-tolerant control of sensors for vehicle driving safety.Based on "Research and Industrialization of Key Technologies of Wire Control Dynamic System"(No.kq2102008),a major science and technology project of Changsha Bureau of Science and Technology,in this paper the integrated brake system with redundant brake unit is taken as the research object.The functional safety analysis is carried out according to the functional safety standard ISO 26262,and the fault diagnosis and fault-tolerant control of the sensors in brake system are studied.The main research contents are as follows:(1)Functional safety analysis of the integrated brake control system.According to the Functional Safety standard ISO 26262,carry out functional safety analysis of integrated brake system.Firstly,the system related items are defined,and the hardware architecture,function definition,working mode and control principle of the system are analyzed.Secondly,hazard analysis and risk assessment are realized through exposure probability,severity and controllability rating to determine automotive safety integrity level and safety goals.Then derive the functional safety requirements by analyzing the system safety concept,and assign them to each sensor.The technical safety requirements for sensors are obtained by analyzing the system hardware.Based on these analyses,the safety mechanism for sensors is designed.(2)Research on sensor fault diagnosis of integrated brake system.Based on the sensor safety mechanism,design the sensor fault diagnosis strategy of the integrated control brake system.Firstly,the mathematical model of the integrated control brake system is built and analyzed,and the sensor fault diagnosis method is selected based on the analyze.Aiming at the master cylinder pressure sensor and pedal travel sensor in pedal unit,multinomial regression algorithm is used to analyze the redundant information between the two sensors,and the residual evaluation function is introduced to realize the fault diagnosis of the sensors.For the active cylinder pressure sensor,motor position sensor and current sensors,support vector machine regression algorithm is adopted to design the prediction model and the prediction model is designed with the running state of the system as the feature to realize the real-time prediction of sensor information.Then complete sensor fault diagnosis by analyzing the residual difference between the predicted value and the measured value.(3)Research on sensor fault-tolerant control of integrated brake system.Firstly,analyze the fault-tolerant effect of sensor redundant signals,and design the signal switching logic for the pedal travel sensor,master cylinder pressure sensor and active cylinder pressure sensor which can be fault-tolerant controlled by redundant signals.Secondly,by improving the sliding mode observer switch function,adding the back electromotive force observer and the phase-locked loop observer,the rotor real-time information is accurately obtained,which can realize the fault-tolerant control of the motor position sensor.Then,in view of current sensors,design a fault tolerant control mechanism based on the number of fault sensors as sensor fault classification.A fault-tolerant control method based on coordinate transformation is designed to realize fault tolerant control of single-phase current sensor.Aiming at the fault of multiphase current sensor,after analyzing and testing the characteristics of redundant brake unit,the pressure control method is designed to realize the fault-tolerant control of brake system based on hardware redundancy.(4)Fault injection test for integrated brake system.The fault diagnosis and fault tolerantcontrol methods of integrated brake system sensor are verified by fault injection test.Firstly,build the hardware-in-the-ring test bench,analysis of sensor fault manifestations and design sensor fault injection scheme.Design the sensor fault injection test cases under basic power assist function and active brake function,and then sensor fault injection tests are carried out.The experimental results show that the designed sensor fault diagnosis strategy can detect the fault state of the sensor in time,and can implement the correct fault-tolerant control strategy to realize the fault-tolerant control of the brake system after the fault,which can meet the functional safety requirements of brake system.