Parameter Identification And Control Of 2-DOF Pan-tilt Based On Sine Wave Dither For Nonlinear System

Well as two-degree-of-freedom(2-DOF)pan-tilt is widely used in civil,industrial and military fields.Aiming at the situation that the working parameters of 2-DOF pan-tilt are prone to drift and its control effect is not good in the field environment,a parameter identification method based on sinusoidal dither is proposed.The real-time parameters are identified online through closed-loop,an adaptive backstepping controller based on sine dither is designed to improve the control effect of pan-tilt.Firstly,a nonlinear mathematical model structure with unknown parameters is established for the 2-DOF pan-tilt by mechanism modeling.Then the parameters of identification input signal PRBS,sampling time and identification time are designed.PRBS signals were input to the pan-tilt,and the output data were collected.The estimated values of corresponding parameters were calculated by the least square method,and the complete pantilt nonlinear model was obtained.Secondly,a real-time parameter identification scheme based on dither signal is proposed to solve the problem of parameter drift.The error cost function is defined when the pan-tilt parameters drift.The effects of dither signal type and other identification scheme parameters on the convergence of pan-tilt error cost function are verified.The dither signal is used to drive the error cost function to its local optimal value to identify the parameter offset.After that,Then,a nonlinear backstepping controller design method based on the augmented Lyapunov function is proposed for the identified nonlinear nominal model of the 2-DOF pan-tilt.Through the nonlinear model structure of the mechanical subsystem design virtual input,and introducing virtual input and the error between the actual input of augmented lyapunov function,and the system zero dynamics equation in the form of error is converted to linear differential equations,linear differential equations to find the root of the controller parameters meet the conditions,Combined with La Salle-Yoshizawa theorem,the closed-loop dynamic system is asymptotically stable globally.The simulation results show that the proposed controller design method has a good control effect on the nonlinear mathematical model of the 2-DOF pan-tilt.Finally,an adaptive backstepping controller based on sine dither algorithm is designed for 2-DOF pan-tilt.The adaptive backstepping controller can adjust the corresponding controller parameters in time when the parameters change.Numerical results show that the proposed controller design method can effectively improve the control effect of the controller.