Research On Lateral Stability Control Of AGVs Combined With Active Steering And Differential Drive

It is easier to realize the control of chassis lateral dynamics active safety system such as active front wheel steering and direct yaw moment control by using the distributed drive form of automated guided vehicle(AGV).However,the centroid of the automated guided vehicle is high when carrying goods,and it is prone to lateral instability under the action of road excitation and centrifugal force when turning on uneven roads.Therefore,this article takes the AGV as the research object to control its lateral stability.The main research contents are as follows:(1)Dynamic model establishment and model validation of automated guided vehicle.The vehicle dynamics model and subsystem model of the AGV including eight-degree-of-freedom vehicle dynamics model,wheel dynamics model,suspension model,tire model and drive system model are established.At the same time,considering the coupling effect between the movement of the AGV body,the interaction between the drive system,the steering system and the suspension system is analyzed.In addition,through the joint simulation of Carsim dynamics software and Simulink,the vehicle model is verified under the step steering condition.(2)Parameter estimator design and stability evaluation index derivation of automated guided vehicle.In order to obtain the key state parameters of the vehicle in real time,and considering that the unmanned vehicle is affected by the uneven road surface excitation during steering,it exhibits nonlinear dynamic characteristics.This paper uses the unscented Kalman filter method to design the state parameter estimator.In addition,in view of the shortcomings of the traditional lateral stability evaluation index,this paper introduces the external road input,and derives the improved lateral stability index based on the lateral load transfer rate.(3)A lateral stability control strategy combining active steering and differential drive is proposed.According to the lateral stability index as the boundary,different index values are involved in different controllers to avoid the interaction between the controllers.The active steering controller is designed by using model predictive control algorithm with yaw rate and roll angle as control inputs.In order to improve the response speed of the system and enhance the robustness of the system,a differential drive controller combining feedforward and feedback is designed to distribute the four-wheel drive torque.In the design of the differential drive feedback controller,in order to weaken the adverse effects caused by the tremor of the general sliding mode control,the dynamic sliding mode control is used to improve the transient response performance of the control.Finally,the four-wheel drive torque is distributed according to the load ratio.(4)Simulation and real vehicle experimental verification.Simulink simulation platform and real vehicle experiment platform are built to simulate and verify the control strategy.Simulation and real vehicle experiments were carried out under different convex block road excitations in step steering conditions.The maximum mean error between simulation and experiment is 8.9%,indicating that the designed parameter estimator can follow the actual parameter values and the proposed lateral stability control strategy can improve the lateral stability of an automated guided vehicle under turning conditions on uneven road surfaces.