Research On Dynamics State Estimation And Stability Coordinated Control For Commercial Vehicle

With the rapid development of Chinese national economy,the road communications and transportation infrestructure of our country has been improved,which has promoted the rapid development of road transport and maintained the production and sales of commercial vehicles at a relatively high level for many years.The commercial vehicles are prone to instability because of characteristics itself,which can cause traffic accidents,serious casualties and economic losses.Most commercial vehicles use pneumatic braking system due to high quality.The stability system of commercial vehicles,based on air braking system,can improve the stability of commercial vehicles and prevent the vehicles from yaw instability or rollover instability.The research on the commercial vehicle pneumatic stability control system is still relatively rare in China,and most of researches are mainly carried out in universities and research institutes.There are no domestic companies that have developed the products of pneumatic stability control system that can be used in practical applications.In the view of the characteristics of pneumatic braking,the commercial vehicle pneumatic stability control system is researched on the basis of the previous development of hydraulic stability control system in our laboratory in the article.Taking a biaxial commercial vehicle as the research object,the TruckSim vehicle model,AMESim pneumatic system model and Matlab/Simulik control strategy model are built,and the off-line joint simulation of the stability coordination control system is conducted based on these models.Then the hardware-in-loop test is carried out using the pneumatic stability system platform.The results of the off-line simulation and hardware-in-loop test indicted that the commercial vehicle pneumatic stability control system described in this article can improve commercial vehicles stability.The main content of this article is as follows:?1?Based on the concept of layered modular,the overall structure of the stability control strategy for commercial vehicles is established.The commercial vehicle stability coordinated control system adopts the multi-objective coordinated control model based on layered module structure,which mainly includes the state variables and parameter estimation,the upper control module and the lower execution module.State variables and parameter identification mainly estimate the key parameters of commercial vehicle.The upper control module is mainly for vehicle status identification,vehicle dynamics coordinated control target formulation,the braking force and additional yaw moment distribution.The lower execution module is mainly the control of pneumatic brake hardware system,in order to achieve the brake deceleration and additional yaw moment of the upper control module and ensure the stability of the vehicle.At last,the key technologies,that need to be solved to complete the stability coordination control system of commercial vehicle,are summarized.?2?Key state variables and parameters,such as brake torque,longitudinal speed,vehicle quality,road slope and centroid position estimation methods are proposed.Based on the dynamics of pneumatic system,the brake chamber pneumatic pressures of the commercial vehicle are estimated in this paper,and the braking torques of the brake chamber are obtained.In view of the different states of the vehicle and the thresholds of the longitudinal acceleration,the longitudinal speed estimation methods are discussed.Based on the analysis of the different characteristics of the changes of vehicle mass and road slope,different approaches are taken to calculate the forgetting factors,and the recursive least squares with variable forgetting factor is used to estimate the vehilcle mass and road slope.In order to improve the reliability and robustness of estimation,the cubature H infinite Kalman filter is used to estimate the centroid position of the vehicle.?3?Based on the zero moment point?ZMP?and time-to rollover?TTR?,the rollover warning is performed,and the brake force and the additional yaw moment for rollover prevention are calculated by the fuzzy control method;the ideal value of the yaw rate is estimated and corrected,and the feedforward and feedback combination method is used to calculate the additional yaw moment for yaw instability prevention;according to whether there is a target brake force,different coordinated control strategies are adopted to obtain the target brake torque of each wheel and the brake torques are applied.Firstly,the rollover index of commercial vehicle with ZMP is put forward.The y-axis coordinate value of ZMP,y_ZMP,is calculated with the use of the vehicle's state parameters and compared with the set threshold value to determine the roll state of the vehicle.The vehicle rollover time is predicted by combining ZMP rollover index with TTR warning algorithm.Then the vehicle brake force and additional yaw moment can be calculated by fuzzy control method,withy_ZMP,and predictive rollover time as the control variables.Secondly,according to the two degree-of-freedom model,the ideal value of the yaw rate is obtained,and the ideal yaw rate is corrected based on the lateral acceleration,the road adhesion coefficient and the load transfer.The feedforward and feedback combined method is used to calculate the additional yaw moment for yaw stability control.The feedforward additional yaw moment is calculated based on the steering angle.The yaw rate and sideslip angle are used as the feedback control varibles,and the feedback additional yaw moment is calculated according to the control varibles deviation and the weight coefficient.The“correctedb-b&-mmethod”is proposed to calculate the weight coefficients of yaw rate and sideslip angle,which takes the sideslip angle,the rate of sideslip angle and tire-road friction coefficient into account.The additional yaw moment for yaw stability control is obtained based on the result of feedforward and feedback control.Thirdly,a coordinate control strategy is proposed to determine the target braking force and the target additional yaw moment of the vehicle based on the anti-rollover target braking force and target additional yaw moment,the additional yaw moment for yaw instability prevention.The wheels needed to be braked are determined and the slip ratio deviation of each wheel is obtained with the HSRI tire model.The target braking moment of the wheel and target brake pressure of the chamber is calculate with the PD method.At last,the action of each control valve is obtained,according to the difference between the current pressure and the target pressure of the brake chamber of each wheel,to ensure that the pressure of the brake chamber can follow the target brake pressure quickly and accurately and the stability coordinated control of the vehicle is realized.?4?The commercial vehicle stability coordinated control strategy is verified by simulation.The parameters estimation algorithm are verified.The estimation value of the air chamber brake pressure is consistent with the actual pressure of the test platform.The maximum deviation rate of the longitudinal speed estimation is 3.9%,the maximum deviation rate of the vehicle mass estimation is 2.9%,and when stable the maximum error of the road slope estimation was 0.5deg,the maximum deviation rate of centroid position estimation is 3.58%.By constructing a co-simulation platform based on Matlab/Simulink,TruckSim and AMESim,the high-friction sine-increase simulation,high-friction sine-with-dwell simulation,high-friction fishhook simulation,low-friction sine-increase simulation,low-friction sine-with-dwell simulation,and open loop low-friction double-lane-change simulation are carried out.The simulation results show that the stability control system can make the vehicle response meet the standard and prevent the vehicle from yaw instability and rollover instability effectively.?5?The commercial vehicle stability coordinated control system verification test based on the hardware-in-the-loop platform.Based on the pneumatic brake hardware device,the hardware-in-loop platform is built by combining Simulator,real-time simulation system,and MicroAutobox,universal controller.And then the high-friction sine-increase test,high-friction sine-with-dwell test,high-friction fishhook test,low-friction sine-increase test,low-friction sine-with-dwell test,and open loop low-friction double-lane-change test are experimented.The test results show that the stability control system can make the vehicle response meet the standard and prevent the vehicle from yaw instability and rollover instability effectively.