Research On Skid-Steering Control Of Six-Wheel Independent Drive Unmanned Ground Platform

With the complexity and danger of emergency rescue and other environments becoming more prominent,unmanned ground platform vehicles have become a research hotspot,and mobility and work scene adaptability are the focus and goals of unmanned ground platform research.Compared with vehicles in the form of traditional deflection wheel steering,platform vehicles have superior flexibility during steering,enabling unmanned ground platforms to complete small-radius steering or even in-situ steering,and have high mobility in different road environments,while independent The in-wheel motor drive system has high space utilization and precise control,which is an important guarantee for the realization of unmanned ground platform skid steering.Relying on the research and development of a school-enterprise cooperation project,this paper takes the six-wheel in-wheel motor-driven unmanned ground platform as the research object,and compares and analyzes the research status of skid steer technology at home and abroad.The main research contents include the following aspects:First,the relevant research on slip-steering theory is carried out.By expounding the principle of skid-steering and analyzing the kinematics of the whole vehicle for the unmanned ground platform,the relationship between the speed of the vehicle’s center of mass and the instantaneous center of steering is obtained.Then,the research on the contact mechanism of the slip-steering wheel was carried out.Starting from the tire characteristics and ground mechanics,a tire model under joint working conditions was established based on the known data,and the linear and nonlinear characteristics of the tire force were analyzed.The theory analyzes the load-bearing characteristics and shear characteristics of soil on tires from the perspective of stress,and deduces the rolling resistance expression caused by soil subsidence from the perspective of energy conservation,and then analyzes the slip-steering process of the unmanned ground platform.Steering resistance torque.Finally,the extended Kalman filter algorithm theory is studied,which lays a theoretical foundation for the subsequent research on vehicle speed estimation.Second,the dynamic model of the unmanned ground platform is established.First,the vehicle coordinate system,the inertial coordinate system and the conversion relationship between the two are specified,which lays the foundation for the dynamic modeling of the unmanned ground platform.Next,according to the needs of the research content The dynamic relationship between the axial motion and the axis motion of the whole vehicle is analyzed,and a six-degree-of-freedom vehicle body dynamics model is established.Then,the suspension model is established with the elastic element and the shock absorber in parallel,the motor response is simulated with an inertial link,the motor model is established,and finally the wheel dynamics model is established.Thirdly,the research and design of the unmanned ground platform skid-steering motion control is carried out,and the layered control method is used to divide it into a skid-steering motion control layer,a torque distribution layer,and a state estimation layer.The vehicle speed is estimated by the extended Kalman filter algorithm,the longitudinal driving force controller is designed by the fuzzy PI control algorithm,and the yaw moment controller is designed by the sliding mode control algorithm.Next,the torque distribution is studied,and the distribution is carried out with the load rate variance and mean weighted minimization and energy consumption minimization as the optimization objectives,and the two-dimensional extension set theory is used to form a multi-objective optimization function for the two distribution weight coefficients.to coordinate the distribution of the torque of the six wheels,and realize the drive control of the unmanned ground platform.Finally,the effectiveness of the control strategy is verified by simulation.Fourth,the independent drive coordinated control simulation verification of the whole vehicle is carried out on the unmanned ground platform.The established vehicle simulation model is simulated and verified under the condition of double line shifting and fitting curve under the high and low adhesion road surface,and the simulation results of the actual state quantity and the expected state quantity are compared,and the slip-steering motion is analyzed.The tracking of the expected value in the process,the simulation shows that the tracking effect is ideal,and the torque distribution based on the torque coordination control strategy and the torque average distribution control strategy is compared and analyzed,and the simulation results are compared to illustrate the unmanned ground platform.The independent drive coordinated control strategy can reasonably distribute the torque required by each wheel and effectively follow the dynamic response of each parameter during the slip-steering motion of the unmanned ground platform.This paper provides a theoretical reference for the drive control of the unmanned ground platform through the research on the slip-steering control,and has certain practical significance for the application and promotion of the unmanned ground platform.