Research On Active Body Attitude Control Of Vehicle With ACC System Based On ECAS

With the development of intelligence,various types of advanced driver assistance systems emerge in an endless stream.Among them,Adaptive Cruise Control(ACC)can automatically control the engine system and braking system according to the signals collected by the radar detector,adjust the longitudinal cruising speed of the vehicle,and reduce the driver's handling burden to a certain extent.However,at present,during the cruising process of the ACC system,the longitudinal acceleration value of the self-vehicle controller output synchronized with the preceding vehicle will be caused by the sudden change of the driving speed of the preceding vehicle,causing the load to shift in the front and rear axles,resulting in the body posture “heading up”.Or "head down" and make driving comfort affected.Long-term use will reduce the user's trust in the ACC system and even cause the ACC system to be deprecated.On the other hand,the Electronically Controlled Air Suspension(ESC)has been used in passenger and commercial vehicles to improve its overall performance due to its variable stiffness and height-adjustability characteristics.Based on this idea,based on the electronically controlled air suspension system,the vehicle attitude control system of the vehicle ACC system under cruise conditions is developed to improve the vehicle stability and ride comfort,and realize the application of vehicle intelligent technology.In response to the above problems,the main research contents of this paper include:(1)Firstly,the ACC system is modeled from the analysis of the working conditions of the vehicle body.The longitudinal kinematics model of the two-vehicle system of the ACC system is established,and the inverse engine model and the inverse braking system model of the lower-layer controller of the ACC system are modeled.(2)Established a model of the vehicle electronically controlled air spring system.Including modeling the air spring mechanism model,mechanism modeling of gas charging and deflating thermodynamics process,modeling of solenoid valve mechanism,and modeling of pipeline system mechanism.In addition,the dynamic model of the vehicle's electronically controlled air suspension is modeled.(3)The upper multi-target controller of ACC system is designed according to the model predictive control algorithm.Based on the two-vehicle longitudinal kinematics model,the cruise multi-performance control system is considered under the model predictive control framework,and multiple performance targets are weighted,so that the transformation is in the form of constraints or objective functions,and then obtained under the model prediction framework.Upper control sequence.(4)The vehicle body attitude control system is designed.Based on the sliding mode variable structure control theory,the real-time pitch angle of the vehicle is the control variable.Under the sliding mode,the anti-pitching moment of the vehicle body attitude is expected under the sliding condition,and the chattering problem is controlled.Then the force distribution is adopted.The model model distributes the expected pitching moment and converts it into the desired vertical vertical force of the suspension;the thermodynamic process of the gas charging and discharging gas converts the suspension force into the desired air quality,and further converts the duty cycle module into the charging and discharging time,and finally The air spring charging and discharging process is realized by the PWM valve PWM wave,thereby generating the vertical force of the suspension and synthesizing the desired additional torque.(5)Based on Matlab and CarSim,a joint simulation platform was built and simulated analysis was carried out.The Carsim environment is the trigger condition of the vehicle body attitude control system.The ACC system uses the electronically controlled air suspension under the Matlab/Simulink environment under the action of the vehicle body attitude controller under the front vehicle rapid acceleration and emergency braking conditions.The air suspension system charge and discharge control the body pitch angle,achieve the body posture imbalance suppression and improve the ride comfort.The research results show that the ECAS-based body attitude control system designed to control the high-speed switch solenoid valve to achieve air spring charge and discharge by real-time torque conversion during self-adaptive ACC system adaptive cruise acceleration or emergency braking.In addition,the vehicle body posture imbalance is effectively and reliably suppressed,and the low-frequency vibration of the vehicle body is reduced,and the ride comfort is improved.