Closed-Loop Identification And Anti-Disturbance Control Of Unmanned Helicopter Yaw Channel

Unmanned helicopters have many advantages,such as good maneuverability,easy to hover,low altitude flight and no casualties,which make them have a wide range of prospects in civil and military fields.It is particularly important to maintain the stability of the attitude of the unmanned helicopter when it is in the state of hover lock,and the influence of external wind disturbance and internal signal coupling should be minimized as far as possible.Most of the unmanned helicopter heading channels adopt the PI controller design scheme.The structure is simple,the parameters are few,and it is easy to implement in engineering.However,it is difficult to achieve satisfactory results for the unmanned helicopter,which is a strong disturbance system.As a result,how to improve the anti-interference ability of the system under the premise of ensuring the tracking performance has become the focus of this paper.Based on the application needs of practical engineering,this paper mainly studies the mod-eling and disturbance rejection control of the course path of unmanned helicopter.In this paper,the mechanism model of the helicopter is firstly analyzed,and the mechanism model in hov-ering or small motion state is approximately linearized into a first-order inertial link,which provides a reference for obtaining the model by using the method of system identification in the future.According to the safety condition of the unmanned helicopter in operation,this paper first describes the steps of open-loop identification,and then describes in detail the closed-loop method and the means to improve the identification accuracy.This paper discusses the identi-fication experiment of unmanned helicopter in cooperation with a research institute and stud-ies the method of extracting effective model from the data with limited excitation frequency band.Subsequently,this article explains the numerical accuracy problems encountered in iden-tifying the course dynamics of this type of helicopter,proposes a relatively simple identification structure,and conducts experiments on a small unmanned helicopter used in a laboratory that has less stringent safety requirements.This kind of open-loop model with relatively simple structure,easy to realize and identification can be directly used in control design.The identification of the yaw channel of an unmanned helicopter cooperated with a research institute found that the open-loop transfer function obtained by different methods is highly dis-persive,and the closed-loop model can only be used as the controlled object for control de-sign.In order to improve the anti-disturbance ability and reduce the impact on the tracking performance,this paper designs a control strategy based on the robust optimal control robust anti-disturbance controller and the tracking performance controller.Due to the requirement of high security,this paper determines the final compensation control structure based on the orig-inal angle loop closed loop.The simulation results show that the anti-disturbance effect under this control structure can be improved by at least 3 times.For the small unmanned helicopter used in the laboratory with less stringent safety requirements,the angle loop is directly opened to design the anti-disturbance of the speed loop.Two control structures are proposed: single-degree-of-freedom and two-degree-of -freedom(2DOF)based on the Q filter.Both simulations and experiments show that a better anti-disturbance performance can be achieved under a single-degree-of-freedom control scheme,but improving the anti-disturbance performance will have a greater impact on the tracking performance.The two-degree-of-freedom control based on the Q filter can achieve decoupling design between tracking performance and anti-interference per-formance to a certain extent.As a relatively simple control structure,it may provide a new idea for anti-disturbance control of unmanned helicopters.