Design Of Control System For Independent Steering Intelligent Mobile Platform Based On Distributed Drive

The intelligent mobile platform is an important application scenario of intelligent driving,in which the control layer function is one of the key technologies to realize intelligent driving.Due to its simple structure and high transmission efficiency,distributed drives have wider applicability and become a good choice for intelligent mobile platform drives.Distributed four-wheel drive intelligent mobile platforms mostly use electronic differential control.Aiming at the problems of understeering and serious tire wear in the steering process,this article designs an intelligent mobile platform based on the distributed drive of the in-wheel motor distributed four-wheel drive and the steering motor front wheel independent steering.It’s wheel hub motor chooses to use brushless DC wheel hub motor,the steering motor chooses to use two-phase hybrid stepping motor,and the vehicle control unit chooses to use Raspberry Pi.And in order to make the intelligent mobile platform intelligent in the future,so that it can complete the control layer function in intelligent driving.In this article,the control system of the intelligent mobile platform will be designed from four levels: single motor control,multi-motor cooperative control,vehicle path following control and real vehicle control.Firstly,from the level of single motor control,mathematical models are established for the two-phase hybrid stepping motor and brushless DC motor,and their control principles are analyzed.The single-motor control Matlab/Simulink models of two motors are built respectively.In order to verify the correctness of the model construction,the model simulation was carried out respectively,and the speed control of the brushless DC motor and the rotation angle control of the two-phase hybrid stepping motor were realized.Secondly,starting from the level of multi-motor cooperative control,a multi-motor cooperative hierarchical control strategy is designed based on Ackermann steering geometry,which realizes the wheel speed and angle distribution of six motors in the dynamic process of intelligent mobile platform steering.The Matlab/Simulink model of the six-motor cooperative control of the intelligent mobile platform is built and the model is simulated,and it is verified that the multi-motor cooperative hierarchical control strategy can make the intelligent mobile platform move in a coordinated manner as a whole.Furthermore,from the level of vehicle path following control,the Model Predictive Control(MPC)method is adopted,and the MPC path following controller is designed based on the kinematic model of the intelligent mobile platform.The controller is applied to the six-motor cooperative control Matlab/Simulink model of the intelligent mobile platform for simulation,and the path-following control is carried out with the circular desired path and the linear desired path respectively.It is verified that the designed MPC path following controller can realize the path following control of the intelligent mobile platform.Finally,starting from the level of real vehicle control,the hardware selection of motor,motor driver and worm gear reducer is carried out.Then I wrote the control code for the GPIO pins of the Raspberry Pi to control the motor in Python.Finally,based on the topic communication framework of Robot Operating System(ROS),the ROS function package for distributed drive control of intelligent mobile platform is developed,and the feasibility of the ROS function package is verified.