Research On Yaw Stability Control Method Of Modern Trackless Train With Multi-joint Structure

With the rapid development of urbanization,urban congestion has become increasingly serious.The existing public transport can hardly meet people’s travel needs.As a new type of urban public transportation,modern trackless train,which combines the advantages of low cost of road transportation vehicle and large carrying capacity of rail transportation vehicle,are the future development trend of urban public transportation.However,the vehicle is equipped with multiple hydraulic articulations and in-wheel motors that can be driven independently.The complexity of the vehicle structure and the difficulty of vehicle motion control are greatly increased.The rear compartment of the vehicle is easy to sway,drift and deviate from the target trajectory,resulting in poor yaw motion stability of the vehicle.This thesis takes modern trackless train as the research object.The yaw rate tracking error and trajectory tracking error are used to evaluate the vehicle yaw stability,and the vehicle yaw stability control strategy is proposed.Firstly,the vehicle is simplified to a seven-section compartment connected by articulated devices and hydraulic devices.Based on Euler-Lagrange equation,the vehicle dynamics model with21 degrees of freedom is established in MATLAB~?software.The simulation comparison between the model in MATLAB~?and the virtual vehicle model in ADAMS~?is carried out to verify the correctness of the model.Secondly,to choose hydraulic device parameters reasonably and improve vehicle yaw stability,the parameter control strategy of the hydraulic device is proposed.According to the force analysis results of vehicle steady-state steering,the hydraulic device stiffness is only related to the vehicle speed and the first axis steering angle.Discrete sampling is performed in the continuous design space,and the objective function is selected as the sum of the yaw rate tracking error and the trajectory error of each axis.The offline optimization of stiffness parameters is carried out based on Genetic Algorithm,and the optimal hydraulic device stiffness of the entire design space is predicted online by functional interpolation method.Simulation verification of the control strategy is carried out.Then,in view of the problems of yaw rate oscillation and large trajectory error of rear axle under the action of hydraulic device stiffness control strategy,a yaw moment feedforward-feedback controller is designed.The feedforward desired value of the yaw rate is calculated based on the linear three-degree-of-freedom reference model.Based on the state equation of trajectory error,the compensated yaw rate is deduced by sliding mode control algorithm.The target yaw rate is obtained by adding the feedforward desired yaw rate to the compensated yaw rate.To achieve the yaw rate tracking the target value,PI control algorithm is designed to calculate the yaw moment which is distributed to the wheel by the torque distribution algorithm.Finally,the control algorithm is simulated and verified under the conditions of U-turn,S-turn and Single Lane Change.The experimental platform of the principle prototype is built to verify the effectiveness of control algorithm.Simulations and experiments verify the effectiveness of the proposed control algorithm.