Research On Driving Stability Of Six Wheel Distributed Driven Unmanned Vehicle

In this paper,the driving stability control strategy of six-wheel distributed drive unmanned vehicle is studied.The six-wheel distributed drive unmanned vehicle has strong power performance and good mobility,and can adapt to complex terrain well.Unlike the classical vehicle steering mode,the skid steering gets rid of the mechanical steering system and decreases the weight of vehicle,so it is more beneficial to the vehicle configuration.Hence,the six wheel distributed drive unmanned vehicle has high commercial value and military value.However,due to the increasing number of electronic control systems,how to coordinate multiple electronic control systems to improve the driving stability of the vehicle.The integrated and coordinated control of vehicle driving,braking,steering and other control systems has become the focus and difficulty of vehicle dynamics research in recent years.Firstly,according to the theory of vehicle dynamics and combined with the simulation requirements of this study,a 9-DOF dynamic model of six-wheel distributed drive unmanned vehicle including 3-DOF body and 6-DOF wheel is established,which provides the model basis and simulation platform for the later vehicle stability analysis and control algorithm design.Then,based on the analysis of vehicle straight driving stability,selecting the yaw rate as the variable,the straight driving control system of the six-wheel distributed drive unmanned vehicle is designed.For the sake of the speed following of the vehicle,PI control is used to calculate the total driving / braking torque of the vehicle;For the sake of the robustness enhancement of the control system,the integral sliding mode variable structure control method is used to determine the additional yaw moment needed to modify the yaw of the unmanned vehicle;For the sake of the avoidance the excessive slip of the driving wheel,an optimal slip rate driving anti-skid controller based on proportional integral control is designed.Secondly,the skid steering of wheeled vehicle is analyzed,and the basic principle of skid steering of wheeled vehicle is introduced.Based on the wheel skid steering dynamics,the skid steering controller of six-wheel distributed drive unmanned vehicle is designed.Finally,the linear driving stability control system and skid steering controller of six wheel distributed drive unmanned vehicle are simulated and verified after integrating vehicle dynamics model and control system.The simulation indicates that: when the unmanned vehicle runs in a straight line on the split road,the deviation rate is only 7.653e-05,and each driving wheel does not exceed the optimal slip rate.The straight driving control system ensures the straight driving stability of the unmanned vehicle.The simulation condition of skid steering is set as the road with adhesion coefficient of 0.8.The simulation indicates that longitudinal velocity does not fluctuate greatly and the yaw rate tracking effect is good in the process of skid steering which verifies the effectiveness of the skid steering controller.