Research On Application Of Terminal Sliding Mode Control In Airborne Photoelectric Payload

Airborne photoelectric payload is widely used in urban monitoring,field search and rescue,power line inspection,disaster early warning and other fields.The accuracy of line of sight(LOS)stabilization control of airborne photoelectric payload determines the image quality,which is one of the key technologies.During the imaging process of flight,the internal friction,mass unbalance torque and other internal disturbances,as well as the external disturbances such as the attitude change,aerodynamic force and vibration of the aircraft seriously affect the control accuracy of line of signt.It is of great significance to study the line of sight pointing control to improve the imaging quality.In order to improve the control accuracy of the line of sight of the airborne pho-toelectric payload under complex multi-source disturbance,based on terminal sliding mode control algorithm,the following aspects are studied in this paper:(1)The line of sight pointing control of airborne photoelectric payload is analyzed and modeled.This paper introduces the requirements and system composition of the line of sight pointing control of airborne photoelectric payload,and establishes the mathematical model.The main influencing factors of line of sight pointing control are analyzed,which lays the foundation for the controller design(2)The frame driving control of airborne photoelectric payload based on perma-nent magnet synchronous motor(PMSM)is studied.Permanent magnet synchronous motor is driven by field-oriented control.Aiming at the problem of parameter perturba-tion and external disturbance of permanent magnet synchronous motor,a motor control method combining terminal sliding mode control and nonlinear disturbance observer is designed.(3)Aiming at the angular velocity closed-loop of mechanical frame,considering the limitation of the traditional terminal sliding mode control method in reaching speed,a novel reaching law is designed to improve the convergence speed of the system and reduce the chattering caused by terminal sliding mode control.A high-order terminal sliding mode observer is designed to further improve the anti-disturbance performance of the system.(4)In order to further improve the control accuracy of line of sight,a control method based on fast steering mirror is studied.The fast steering mirror driven by piezoelectric ceramic is used as the actuator to achieve two-stage stabilization.Aiming at the hysteresis nonlinear characteristics of piezoelectric actuator,the Bouc-Wen model is used to simulate the actuator,and the bat search optimization algorithm is used to identify the model parameters.Combined with the model,a high-order terminal sliding mode hysteresis observer is designed to realize the observation and compensation of hysteresis nonlinearity.On this basis,a new finite time convergence terminal sliding mode controller is designed in the outer loop control loop to achieve better response characteristics.From the current loop of the motor to the speed loop of the frame and then to the control of the two-stage stabilizing element,a terminal sliding mode controller design method is proposed to solve the problem of the line of sight of the airborne photoelectric payload.Complete theoretical analysis and proof are carried out,and the controller is verified by simulation and experiment.Compared with the traditional control method,the new control method achieves better control performance under complex multi-source nonlinear disturbances.