Research On Three-degree-of-freedom Helicopter Control System Based On Precise Feedback Linearization

At present,the research and application of UAV(Unmanned Aerial Vehicle)have become a hot spot.In the research,the unmanned helicopter control technology is not only an important aspect of the unmanned helicopter system development,but also the core technology.The excellent control algorithm is the core technology of unmanned helicopter enterprise,and it can bring huge profits for the enterprise.Now the consumer class unmanned helicopter market is hot.But there are many unmanned helicopter crashes,or even wounding incidents,which makes the unmanned helicopter stable operation has been concerned,and makes the stability of the UAV must be set about both the modeling and control.The research focus of this paper is the research of unmanned helicopter control technology.The platform of the study is a 3-DOF(three-degree-of-freedom)helicopter experimental platform,designed to study a linearization and decoupling control algorithm for highly nonlinear and strongly coupled affine systems.The main work of the paper is as follows:(1)The Lagrange method and Newton’s second law are used to systematically modeling and systematically identify the system characteristics of three-degree-of-freedom helicopters.Firstly,the mechanical structure and electrical structure of the 3-DOF helicopter are modeled in detail to obtain the system dynamics equation with affine nonlinearity.The linear system identification experiment of the height axis and the pitch axis are carried out by using the M sequence.The linearity of the system is obtained,which proves the nonlinearity and strong coupling of the three free helicopter systems.(2)Based on the PID controller method of the traditional SISO system,this paper designed a position controller for 3-DOF helicopters with MIMO and strong coupling characteristics.First,a multivariable PD decoupling controller is designed for the height axis and the pitch axis.A cascade PD controller between the travel axis and the pitch axis is designed.The experimental results show that the system position response achieves the basic control objectives,but there are problems such as difficulty in system parameters,slow system response,poor system robustness and poor system coupling characteristics.Seriously,the system has the phenomenon of "losing high".(3)Using the LQR output-tracking controller designed a 3-DOF helicopter position-tracking controller.Firstly,the affine system of the 3-DOF helicopter is linearized at the equilibrium point,and the control rate of the system is solved according to the control rate of the LQR output-tracking controller,and the control rate of the actual system is obtained.The experimental process shows that the position response of the system is quick and the parameter adjustment is convenient,but the decoupling characteristic is poor,and the system still has the phenomenon of "losing high".(4)The decoupling and linearization of the 3-DOF helicopter affine system based on the precise feedback linearization method is proposed.Firstly,the decoupling and linearization of the affine system is carried out on a large scale by means of accurate feedback linearization.The LQR method and the PD method are used to design the position controller under the wide range of linear conditions.The experimental results show that the position of the control system is rapid,the parameters are easy to adjust,the decoupling of the system is complete,and the phenomenon of "Iosing high" is completely solved.(5)A simulation software based on 3-DOF helicopter control algorithm was developed.According to the PID control algorithm,LQR tracking control algorithm and accurate feedback linearization algorithm in the study of the 3-DOF helicopter,this paper designs the controller design simulation software based on MATLAB.In the actual parameter adjustment process of system,the simulation results of this software can be used directly on the device.This paper is revolved the position control of the 3-DOF helicopter,compared the advantages and disadvantages of the two control methods,such as PID decoupling control and LQR tracking controller.An accurate feedback linearization method is proposed,and the 3-DOF helicopter in a wide range of decoupling and linearization work,make up for the shortcomings of the first two methods.In this paper,the precise feedback linearization method and the simulation algorithm of the control algorithm proposed for the 3-DOF helicopter are useful for the control and simulation of other unmanned helicopters.