Research On Driving And Stability Control Of Hybrid Semi-trailer Train Based On State Estimation

The hybrid semi-trailer train studied in this paper is developed on the basis of existing ordinary semi-trailer trains,in order to improve fuel consumption rate,reduce exhaust emissions and environmental pollution,and increase electric drive in trailer parts to improve vehicle carrying capacity and economic benefits.It has the same structural characteristics of large mass,long size,high center of mass and complex saddle coupling relationship as the ordinary semi-trailer train,which easily leads to the instability of the train,such as folding and rollover,etc.,and it is more likely to lose stability after the improper control power is added to the trailer.In this paper,based on the vehicle dynamics model,through the control algorithm,the driving/braking torque of the trailer can be reasonably matched,and at the same time,the stability and safety of the whole vehicle can be improved by ensuring its ability to prevent rollover and other instability;Some state parameters required by the control algorithm can not be directly measured or the measurement cost is too high,which needs to be estimated by the algorithm combined with the vehicle dynamics principle.Therefore,this paper takes the hybrid semi-trailer train as the research object,studies the vehicle state estimation,torque matching and stability control,and completes the following work:(1)a vehicle mathematical model with 14 degrees of freedom is established,which takes into account the longitudinal,lateral,yaw and roll motions of tractor and trailer,the rotation of six tires and the steering motion of steering wheels,and the reliability of the model is verified by joint simulation with Truck Sim automobile dynamics simulation software.(2)Aiming at the problems of uncertain measurement noise,serious influence of accumulated error and sensitive initial value in the process of semi-trailer state estimation,a double adaptive unscented Kalman filter algorithm(FFUKF)is proposed,which is suitable for estimating several state variables such as articulation angle and vehicle speed of semi-trailer trains.Based on the nonlinear dynamic model of semi-trailer car,through the measured wheel speed and vehicle acceleration information,firstly,fuzzy control is used to adaptively adjust the slip rate tolerance,comprehensively judge the stable state of each wheel,and estimate a vehicle speed through the wheel speed;At the same time,fuzzy control adaptively adjusts the measurement noise,and estimates the hinge angle and another vehicle speed by using unscented Kalman algorithm;Then,the Kalman filter algorithm is used to fuse the estimation results of the two methods,so as to realize the real-time estimation of the longitudinal and lateral velocity,yaw rate and the articulation angle between trailer and tractor.At last,the multi-condition simulation experiment is carried out in Simulink/Truck Sim co-simulation environment,which proves that the proposed double adaptive unscented Kalman estimation algorithm(FFUKF)has strong adaptability,stability and robustness,has higher estimation accuracy than the ordinary fuzzy adaptive unscented Kalman(FUKF),and can effectively overcome the cumulative error.even if the initial estimation value is inaccurate and ABS control input is available,the vehicle speed and hinge angle can still be accurately estimated in real time.(3)The principle and process of two quantitative rollover indicators and rollover warning time are introduced.Then,supported by the semi-trailer dynamic model and the yaw rate,roll angle,longitudinal hinge force and other state parameters provided by FFUKF estimator,a controller which can reasonably match the driving torque of the trailer and has stability control function is designed.It consists of three MPC sub-controllers: stability,braking and driving.The yaw MPC(Model predictive control)reduces the difference between the actual roll angle/yaw rate and the expected value by increasing the additional differential torque of the trailer,and avoids the vehicle side slip,shimmy and rollover instability.Brake MPC prevents the train from folding instability by increasing additional braking torque;Driving MPC controls trailer to increase proper wheel driving torque and improve the transportation capacity of the whole vehicle.Finally,through the joint simulation with Truck Sim,it is verified that the controller can not only reasonably match the power of the hybrid semi-trailer train and define the boundary input of the electric driving torque,but also effectively improve the anti-sideslip,shimmy,rollover and folding ability of the vehicle,and has the advantages of short response time and good stability control effect.