Follow Up Rearview Mirror System Based On Sliding Mode Variable Structure Control

Traffic safety has been highly concerned by people.Usually driving safety is determined by the driver's information and largely depends on the field of vision.The driver obtains the lateral and rear view field of the vehicle mainly through the external rearview mirror.However,due to the limitation of the size and angle of the rear view mirror,there is a blind area behind the rear side of the vehicle,which is a high incidence area of accidents.In order to reduce the blind area of driving and improve the safety of driving,the research of the servo rear view mirror system is carried out.The servo system of the rear view mirror is based on the signal of speed,steering wheel and steering lights.The motor position servo control is realized by single-chip microcomputer and the angle of the rearview mirror is adjusted in real time.Based on the analysis of the relationship between vehicle steering trajectory,rearview mirror location and driver's blind area,the sliding mode control algorithm of BLDC motor with rearview mirror is studied;the hardware circuit and software control strategy of servo rear view mirror system are designed.The influence of speed and steering angle of steering wheel on the track of vehicle is studied.The vehicle trajectory curve is obtained according to the simulation of specific vehicle.Considering the driver's eye and head rotation,the driver's eye area is determined,and the driver's blind area is determined according to the driver's eye position,rearview mirror location and vehicle's inherent information.Considering the actual road condition,the track and the range of the driver's field of vision,the suitable rotation position of the rearview mirror is given as the system of the following rearview mirror.The brushless DC motor is selected as the actuator of the servo rear view mirror system.The mathematical model of the motor is established and simplified,which is convenient for the design of control algorithm.A position control algorithm of DC motor based on sliding mode backstepping method of first order low pass filter is proposed.The actual position control is realized by backstepping virtual control.The first derivative low pass filter is used to calculate the derivative of virtual control,and the phase lag of the system is compensated.In order to simplify the hardware circuit design,reduce the use of current and speed sensor,the DC motor position sliding mode high gain observer control algorithm based on sliding mode backstepping method is designed.The high gain state observer motor speed and current and its derivative.The motor parameter drift and load disturbance effect on observer are discussed.The sliding mode variable structure index reaching law is improved.The Lyapunov function is designed to prove the stability of the system.Compared with the traditional sliding mode variable structure and PID control algorithm,the effectiveness of the algorithm is verified by the simulation experiment.The software and hardware of the servo rearview mirror system are designed.The software design includes the design of the system function realization,the system fault diagnosis design and the system digital signal filtering design.The hardware design includes the MCU module,the power supply module,the motor drive module,the signal acquisition and processing module.The servo rearview mirror system realizes the "follow up" function of the rearview mirror in the process of vehicle driving,which reduces the blind area of the driver's field of vision and improves the safety of driving.Meanwhile,the research of vehicle trajectory and driver's visual field can be used for the layout design of the rearview mirror.The research of sliding mode variable structure control algorithm of Brushless DC motor has a certain reference value for other motor position servo control.