Research On Skid-Steering And Coordinated Control Technology For Distributed Drive Unmanned Ground Platform

With the improvement of science and technology,unmanned platforms have begun to be widely used in the construction of community economy and national defense modernization.As a special steering form,skid-steering can greatly improve the flexibility and maneuverability of unmanned platforms compared to Ackerman steering.The application of distributed drive system also lays the foundation for highperformance vehicle chassis control,becoming one of the key technologies to improve the performance of unmanned platforms.In this paper,combine with an engineering research and development project,by summarizing and analyzing the research status of skid-steering at home and abroad,skid-steering and coordinated control technology of the distributed drive unmanned platform are studied,and the path following control algorithm based on model predictive control is designed.The main research contents include the following aspects:Firstly,the dynamics modeling of an unmanned platform with six-wheel independent drive is studied.In-wheel motor model of the unmanned platform independently driven by the six-wheel in-wheel motor with skid-steering,the tire model of the combined side slip and longitudinal slip and the dynamic model of the trailing arm,the wheel model and the vehicle body dynamics model are established.And then,the linear acceleration and deceleration and conditions are simulated in Simulink.Finally,the simulation angle data of the swing arm swing of the unmanned platform is converted with the suspension data measured by the linear sensor in the vehicle test.The comparison proves the accuracy and precision of the established vehicle dynamics model.Secondly,the skid-steering of unmanned platform based on model predictive control is studied.The three-degrees-of-freedom single-track dynamics model of the unmanned platform is studied,and lateral velocity,longitudinal velocity,heading angle,yaw rate,lateral displacement and longitudinal displacement in the ground coordinate system of the vehicle are selected as the state variables and the expected yaw moment which is applied to the vehicle is selected as the control quantity,the predictive model of model predictive control is established,and the optimization problem with constrains is solved,and finally the skid-steering controller is simulated and verified in Simulink.Thirdly,the research on the coordinated control strategy of driving torque is carried out.The theory related to the Kalman filter algorithm is studied,the advantages and disadvantages of several Kalman filter algorithms are compared,and the unscented Kalman filter is used to estimate the longitudinal and lateral vehicle speed of the unmanned platform,and the algorithm flow of vehicle speed estimation is determined.The algorithm flow.After that,the expected longitudinal vehicle speed is taken as the target,and the expected total driving force is decided by the PI controller.Then,the sixwheel distributed drive torque coordinated control strategy is studied.The expected yaw moment obtained by the skid-steering controller in the previous study and the expected total driving force obtained by the PI controller are combined,the torque distribution of the six in-wheel motors is performed based on the minimum variance of the tire load rate and minimization of tire dissipation energy.And the torque distribution is dynamically adjusted according to the lateral acceleration and longitudinal vehicle speed using the look-up table method,so that the unmanned platform can not only track the desired movement path and longitudinal vehicle speed,while also ensuring stability during driving.Fourthly,the research of distributed drive coordination control is carried out.Establishing a distributed drive coordinated control simulation model by integrating the unmanned platform dynamics model,skid-steering controller model,vehicle speed estimation model,total driving force decision model,and drive torque coordinated control model in this chapter fist of all.Then three working conditions of straight-line correction,double-shifting path tracking and trigonometric curve path tracking were selected to simulate and verify the multi-wheel drive coordinated control strategy.And the actual path,expected path,and actual heading in the simulation results were verified.Quantified comparative analysis between angle and expected heading angle,actual speed and expected speed,actual speed and estimated speed,actual total driving force/total yaw moment and expected total driving force/total yaw moment.Comparing with the non-linear correction control,the linear correction control can effectively prevent the unmanned platform from deviating;in the double-line-shifting path tracking and trigonometric curve tracking conditions,the distributed drive coordination control strategy can make the unmanned platform track the desired path and desired heading angle accurately.This proves the effectiveness of the distributed drive coordinated control strategy proposed in this paper.