Research On High Precision Control Strategy Of Fast Steering Mirror

With the continuous development of science and technology in aerospace,industrial technology,biomedicine and other fields,the application of precision control systems has become more and more extensive,and the requirements for accuracy have become higher and higher.As a precision tracking subsystem of a composite axis tracking system,the requirements of the precision index of the fast steering mirror(FSM)system are becoming more and more stringent.Based on the actual project,this paper explores the methods to improve the control accuracy of system and expand the operating boundary of the system.Then,with this goal,according to the idea of establishing the nonlinear model of the system,analyzing the performance of the controller,designing of the controller,and exploring of the limit performance of the system,the following main work was studied and completed:1.First is establishing a complete system model under the full operating range,including linear,non-linear,and noise components.Based on the analysis of the physical structure of the system,a theoretical linear model of the system is established.Based on the difference between the model and the actual open-loop frequency characteristics,the theoretical parameters are corrected to obtain a theoretical linear white box model that is very close to the actual system..In order to be more practical,the actual nonlinear parameter values were obtained through theoretical calculations and experimental measurements,and then,simplified nonlinear models were established,including saturation limit models and dead zone models.At the same time,a noise model is established based on a set of measured noise signals.Then,the white box model is transformed a little to obtain the nonlinear state space model of the system,which is used for the controller design,performance analysis and performance limit exploration in subsequent work.2.Secondly,the double-integral controller is designed based on the theory of state augmentation and state feedback.This design method is simple to debug,and we can adjust he system performance flexibly through the configuration of the poles,thereby searching the system's physical limits.Compared with the single-integral controller,the performance of the controller has been improved,which can completely meet the requirements of the project.3.Third,the state feedback dual integral controller is equivalent to a classical type controller.Aiming at the difficulty of implementing the state feedback dual-integral controller,a dimensionality reduction observer was introduced,and then the model equivalent and order reduction were performed.So,the double integral controller was equivalent to a classical controller.After equivalence,the controller can be regarded as a classical controller composed of several typical links such as lead link,notch link,integral link and first-order differential link.In this way,it not only has the advantages of convenient debugging and good control effects of modern control theory,but also the advantages of simple implementation of classical controllers,which has great practical significance.4.Fourth,the system's performance limit is explored,and the system's performance limit curve is obtained.It is found that the performance of the system is affected in the order of the voltage saturation limit,the acceleration saturation limit and the velocity saturation limit.Based on this,the performance limit curve of the system is drawn and the working area of the system is divided.Compared with the single-integral controller,the linear operating range of the double-integral controller is increased,the runaway limit of the system is also significantly improved.So,the performance limit of the system is improved.To sum up,this paper has designed a double-integral controller for fast steering mirrors with high accuracy index,good limit performance and easy implementation.The simulation results show that the steady-state accuracy of the controller can reach 0.8 ?,the tracking accuracy in the low-frequency band is significantly improved compared with the single integral controller,and it has a larger linear working area and is less out of control.