Driving Control Of The In-wheel Motor Of Multi-Axis Steering Electric Vehicls

Electric automobiles are an important direction in the development of the current automotive industry.Driving by using distributed in-wheel motors,as a new driving form of electric autos,can optimize the structure of cars and has the advantages of higher efficiency of transmission and space utilization and diversification of driving form.In this thesis,driving control of the in-wheel motors and the control strategy of cars are the research objects and the main points are in the following:(1)Analysis of the characteristics of the in-wheel motors and bench testBy comparing the performance of several common drive motors,the advantages of permanent magnet motors were pointed out.By discussing the structures,working principles and mathematics model of the permanent brushless dc motor adopted in the experiment,the open-loop control system and double closed-loop control system of the motor was analyzed and established,and the simulation of the system was carried out by using Matlab/Simulink software.By designing test platform,the actual acceleration performance and the mechanical property of the in-wheel motors were tested through a designed experiment.(2)Study of the electronic differential control algorithmOn the basis of the structure of the experimental car,the dynamics models of the car and tires were analyzed.By analyzing the current electronic differential control algorithm,the deficiencies of them were pointed out.According to Ackermann theorem,the electronic differential model based turning speed was deduced.Introducing deviation rate as the new control target and combining the established dynamics models,the centrifugal force of the wheel in steering was analyzed.By introducing the torque control,a concurrent control strategy for speed and torques based the bidirectional sliding rate was put forward,and then the simulation of the control algorithm was carried out to verify its rationality by using Matlab/Simulink software.(3)Development of the experimental prototype cars and its control systemTo verify the rationality of the control algorithm,a three-axle car prototype with the first axle steering and the second and third axles being driven by the four in-wheel motors mounted on the two axles was developed.The distribution hierarchical Control system of the prototype car was built by using a micro industrial computer ARK-5261,a data acquisition card PCI-1712 and a 12-axis movement control card as central control units and with the motor controller developed based on mono-Chip Computer STM8 S.It is a closed-loop system based on speed and torque feedback with speed sensors and current sensors built-in,in which the operation information of the driver is acquired with angle sensors and acceleration pedal.The control program of the system was developed using Labview and the rationality of the system was verified on the test bench of the prototype car.