Research On Key Technologies Of Model Driven Vehicle Stability Control System

The Electronic Stability Control System(ESC)is one of the core technologies for automotive chassis control,which improves the stability and safety of the vehicle.Foreign scholars have researched it earlier and completed the development of industrialization.The product has formed a complete development process from requirements analysis to acceptance testing,and the product occupancy rate is dominant,resulting in the key technologies in ESC only being mastered by foreign active security suppliers and formed a technological barrier.This paper relies on the school-enterprise cooperation project "Development of Vehicle Chassis Torque Control Model".Based on the Simulink software,the ESC development and integration method is estabilished by using the model driven technology.The three key module control strategies of engine torque control,direct yaw moment control and multi-function coordinated control are studied in ESC,and the vehicle parameter matching and calibration parameter strategy is constructed.The main results of the paper are as follows:(1)Using advanced model drive technology,an integration development method for vehicle stability control is proposed.The limitations of the traditional code writing development method are pointed on.On this basis,model driven control software development principles and standards are developed,including the globalization principle is adopted to avoid the fuzzy problem of subsystem interaction,the systemlevel simulation can be used to observe the performance of the system and the data transmission between subsystems,and the model driven control strategy is adopted to facilitate early detection of bugs in the design phase;selection of agile development model to save and reduce the development time and risk of complex systems.According to the characteristics of model driven,the real-time task partitioning method of each main function in ESC is proposed;the model hierarchical structure is established based on ISO 26262-6 standard;the signal flow is managed based on different module distribution management to clear the data transmission and operation process;the parameter files are defined in blocks according to the function domain and execution purpose;the MATLAB/Simulink model specification is applied to the ESC model construction process.Based on the control strategy development and model driven development methods,combined with the previous development results of the research group,the simulation model of ESC control software is developed on the Simulink platform and the code generation is realized.The source code amount reached more than 200 M,and the ESC controller executed the code amount.1.5M,reaching the level of similar foreign products.(2)Combining control theory,automotive dynamics theory and engineering practice,the vehicle electronic stability control strategy is designed.Based on the modularization idea,a system-level stability control architecture is established and the control strategies and methods of the Anti-lock Braking System(ABS),the Traction Control System(TCS)and Vehicle Dynamic Control(VDC)are explored.The three key models are studied in ESC:(1)For the engine torque control,the vehicle slip ratio and the differential shell speed are taken as the control objects,the real-time performance of its control intervention and exit is improved.PID feedback control is adopted and the target engine torque control strategy is established for the influence of engine torque variation on the vehicle and the driver.In combination with engine speed and torque variation,the gearbox gear retention strategy is designed to avoid the influence of clutch engagement on the drive wheel torque.(2)For the direct yaw moment control,based on the analysis of the vehicle instability state,On the basis of the Ackermann model,the correction of the tire lateral stiffness,road inclination and ABS intervention are considered to calculate the target yaw rate,which makes it more suitable for complex vehicle stability control conditons.The side slip angle and the yaw rate are taken as the controlled objects.The calculation of the target yaw moment is completed by the sliding mode control algorithm,and the weighting factor of the side slip angle is designed.The controlled wheels are determined according to the steering characteristics of the vehicle and the wheel lock condition.Combined with the dynamic equation of the yaw moment and the braking force to calculate the braking torque of the controlled wheel.(3)Because the driving condition of the vehicle is more complicated,this paper designs a dual cascade control strategy based on driver braking demand,direct yaw moment control,anti-over-slip control and anti-lock braking control requirements.The primary stability coordination rule calculates the target braking torque according to each functional feature and the starting sequence of controller.The advanced stability coordination rule optimizes the target braking torque according to the order of the controller intervention time.This method can effectively improve the robustness of the system and reduce the difficulty of function superposition,and avoid the control target and the braking torque control confusion.(3)A co-simulation test platform for vehicle dynamics and control software is built to verify the ESC developed.The platform consists of two parts,one is based on AMESim software to build a vehicle integrated simulation model,including the ESC Hydraulic Control Unit(HCU)model,and gives a mathematical description of the main components,including 15 degrees of freedom vehicle dynamics model,engine model,gearbox model,tire model and braking system model,etc.The other part is the ESC model built in Matlab/Simulink software combined with the model development method and integrated design.On the platform,the stability control system is simulated under six working conditions: high adhesion braking,low adhesion braking,jump road braking,low adhesion acceleration,split surface acceleration,and the sine with dwell test.The sub-module response results including ABS,TCS,and VDC are verified.Then through testing including high adhesion cornering brakes,low adhesion cornering brakes,jump road curve braking,high adhesion step partial braking,low adhesion step partial braking,low adhesion lane partial braking,slalom with increasing steering angle partial braking.It verifies the effectiveness of the coordinated control strategy in the event of the initiation of each major functions.The simulation proves that the vehicle state parameter estimation is accurate and the control strategy is reasonable and effective.The control logic covers various driving conditions of the vehicle,which effectively avoids vehicle instability and reaches the engineering application level.(4)According to the characteristics of the control software model developed by the model driven technology,the vehicle matching and software calibration strategy of ESC is proposed.The ESC’s vehicle calibration process and planning cycle are summarized,and the specific contents and methods in the matching of the vehicle hardware and braking system are established,including sensor calibration,centroid position matching,characteristic vehicle speed calculation,flow coefficient,CP coefficient and P-V characteristics;then,the main software calibration parameters in ESC are extracted by analysising the control strategy,combined with the simulation on the simulation test platform,the critical value of the calibration parameters is determined and the feasible domain of the matching parameters is obtained.Within this range,the ant colony algorithm using the elite strategy completes the further tuning of the calibration parameters,effectively improving the overall efficiency of the calibration work.(5)The verification of the effectiveness and accuracy of the research method and the developed control system is completed based on the real vehicle test platform.After the refitting the brake system and control system of the test vehicle,the test vehicle is built with the rapid control prototype.In the real road environment,the relevant tests of summer high adhesive pavement and winter low adhesive pavement are carried out respectively.The ABS function of the developed system is verified by dry asphalt pavement and ice surface full-force braking.The results showed that the average braking deceleration meets the regulatory standards,the yaw rate did not exceed 5% of the national standard;the TCS function is verified by the ice surface acceleration and the split road acceleration.The test results show that the vehicle acceleration meets the requirements of the industry;Combined with the FMVSS 126 regulations,the VDC function is verified by the Sine with Dwell condition.The test results proved that the yaw rate and lateral displacement of the vehicle meet the requirements of FMVSS 126.The test data verify the ESC control strategy studied in this paper has strong real-time performance,high reliability,good effectiveness,and adaptability to working conditions.It also shows that the model-driven technology proposed in this paper can be applied to the development of ESC complex control systems and shows obvious advantages.