Sensor Fault Diagnosis And Fault-tolerant Control Of Integrated Brake Control System Based On Functional Safety Analysis

In recent years,under the background of the rapid development of society and the electrification and intelligence of automobiles,the safety of vehicle should be paid more attention.The Integrated Braking Control system is more suitable for the trend of automotive development with its highly integrated structure and functions.Equipped with Redundant Brake Unit,the redundancy of the braking function can be realized to meet the needs of the highly automated driving system.The Integrated Braking Control system plays an increasingly important role in the safety of vehicle driving.Therefore,the Functional Safety of the integrated braking control system should be guaranteed.After the release of the ISO 26262 Functional Safety standard,the concept of Functional Safety has gradually become popular in the research of automobile safety.Therefore,analyzing the Function Safety of the Integrated Braking Control system according to the method of functional safety,performing fault diagnosis and fault-tolerant control on sensors,and using Redundant Brake Unit to realize the failure backup of braking functions are of great significance for vehicle driving safety.Based on the school-enterprise cooperation project ’ Development of IBC Integrated Braking Control Algorithm’,this paper taking the Integrated Brake Control system as the research object,doing the Functional Safety analysis according to the functional safety standard,does research on sensor fault diagnosis and fault-tolerant control.The main research contents are as follows:（1）Functional Safety analysis of the Integrated Brake Control system.According to the ISO 26262 Functional Safety standard,the Functional Safety analysis of the system will be done.Firstly,the item definition will be done.Secondly,Hazard Analysis and Risk Assessment will be carried out,including determining the Automotive Safety Integrity Level according to the severity,exposure probability and controllability of the hazard event and obtaining safety goals.Then,according to the concept of functional safety,the Functional Safety requirements are obtained from the safety goal.Lastly,the Functional Safety requirements are allocated to the system sensors by Fault Tree Analysis,and the Functional Safety requirements for the sensors.（2）Research on control strategy of the Integrated Brake Control system and pressure control strategy of Redundant Brake Unit.In the first part,the algorithm of the vehicle braking function is designed,including the basic braking function and deceleration control function.Then,the pressure control algorithm of the executive layer is completed,including the pressure loop controller with feedforward and feedback and the position control of PMSM based on the servo three closed loop.Finally,the pressure control strategy of the executive layer is verified,and the results show that the control effect is good.The second part analyzes and tests the characteristics of the solenoid valve firstly,which is the key component of the Redundant Brake Unit.And then,based on the results,valve characteristics feedforward plus PI feedback boost and decompression control algorithm is designed.Finally,the pressure control strategy of Redundant Brake Unit is verified,and the results show that the pressure control can meet the requirements of braking function backup.（3）Sensor fault diagnosis and fault-tolerant control of Integrated Brake Control system.The fault diagnosis method and the fault-tolerant method after the sensor fault is detected are mainly considered.Firstly,the fault is analyzed and modeled.And then the hardware redundancy is used to realize the fault detection of the pedal travel sensor and switch the output signal if the fault is detected;for the motor current sensor,the fault detection method based on the coordinate transformation is designed,and the fault-tolerant compensation of the signal after the single-phase sensor fault is realized;for the motor rotation angle sensor,the EKF algorithm is used to estimate the rotation angle,and the residual chi-square test is used to realize the fault diagnosis.The estimation and fault diagnosis algorithms are verified by simulation,and the results show that the algorithm can successfully detect the occurrence of faults.Finally,the fault state of the Integrated Brake Control system and the fault-tolerant scheme in different states are defined.（4）Test verification for sensor fault diagnosis and fault-tolerant control of Integrated Brake Control system.To verify sensor fault diagnosis and fault-tolerant control of Integrated Brake Control system,fault injection test is used.Firstly,a hardware-in-loop test bench combining the Integrated Brake Control system and Redundant Braking Unit is built.And then,the fault injection scheme and fault injection test case are determined.Finally,the fault injection tests of pedal travel sensors and motor current sensors are performed respectively on the basic braking function and deceleration control function of the Integrated Brake Control system.The results show that the fault can be detected successfully,and fault-tolerance method designed can run effectively,including signal switching using redundancy,fault-tolerance compensation and using Redundant Brake Unit as braking backup.The braking function of Integrated Brake Control system can reach ‘Fail Operational’ level,keeping the vehicle in a safe condition.Functional Safety requirements for sensors in Chapter 2 can be met.