Modeling And Motion Control Study Of Six-wheel Independent Drive Platform System

With its good off-road and obstacle-crossing capabilities,wheeled unmanned platforms are widely used in military combat,field rescue and site handling and other scenarios with harsh environments.As the number of wheeled unmanned platform drive wheels increases,it can significantly enhance its dynamics,but the mutual coupling and limitation between multiple wheels will make the structure and control of the system more complex.In this paper,under the premise of comprehensive consideration of the wheeled unmanned platform power demand and system complexity,the six-wheel independently driven unmanned platform is selected as the research object,and the following research is carried out on how to realize its stable operation under low-speed heavy load conditions.Firstly,this paper constructs a kinematic and dynamics model of the unmanned platform with the center of mass position,vehicle mass and road slope as the relevant parameters for the problem of center of mass shift under low-speed heavy load conditions,and conducts Simulink-based modeling simulation to verify the influence of each parameter on the stability and coordination of the system motion.Secondly,based on the vehicle model derived in the previous paper,the corresponding parameter estimation algorithm is designed in real time in order to reduce the influence of the unknown parameters of center of mass position,vehicle mass and road slope on the system performance.In order to reduce the coupling between the mass and slope parameters,a recursive least squares method with variable forgetting factor is used to establish a joint estimator to reduce the coupling and improve the accuracy.Meanwhile,in order to reduce the complexity of the center-of-mass position estimation and improve the convergence speed,a center-of-mass position estimator is designed using easily available sensor data such as longitudinal acceleration,wheel speed and torque,and the effectiveness of the estimation algorithm is demonstrated by simulation.Again,after the parameter estimation results of the previous paper are available,the study of the unmanned platform stability and coordinated motion control strategy is carried out.In order to reduce the nonlinearity and coupling of the system,a hierarchical control structure is designed,dividing the control system into a total torque decision layer and a torque distribution layer.In order to solve the problem of slow motion response of the vehicle under heavy load,a feedforward with PI feedback control structure is adopted for the total driving torque decision layer.At the same time,in order to improve the coordination between each drive wheel,the torque distribution is carried out using the load ratio-based rule and the torque output is optimized using the drive anti-skid technique.After the overall simulation analysis,the vehicle operation is very stable.Finally,in order to verify whether the control strategy is practically feasible,the whole control algorithm is built in the Simulink platform and integrated into the MPC5746 R embedded hardware platform,and the effectiveness of the control strategy is verified by calibrating and testing each parameter and verifying the actual six-wheel unmanned platform for various operating conditions.