Research On Finite-time Adaptive Attitude Tracking Control For Twin-rotor Aircrafts

The rotor aircrafts,as a common type of UAV,have many advantages such as simple structure,strong maneuverability,simple operation and high efficiency and low cost ratio,and have the ability to adapt to complex environments such as vertical takeoff and landing,free hover,etc.,so they have a broad development prospect.Therefore,they are widely used in agricultural plant,industrial inspection,search and rescue,Intelligence reconnaissance etc.,especially in other civilian occasions and military fields.The rotor aircrafts are underactuated systems with nonlinear,multivariable and strong coupling.The uncertainties of the internal system model and the external unknown disturbance increase the difficulties of designing the aircrafts control system.As the key technical point of the rotor aircrafts control system,it is necessary to research on the attitude control schemes.The research of this dissertation are as follows:Firstly,in the dissertation,the test platform of two-rotor aircrafts is designed,including the test rig of two-rotor aircrafts,the host system console and direct-current power supply,which provides platform guarantee for subsequent control schemes experiments.The simple mathematical model of the two-rotor aircrafts is established based on Euler Angle description.The evaluation indexes of measuring the system control performance,such as IAE,ISDE,IAU and ISDU,are introduced,which provide theoretical basis support for the analysis and comparison of experimental data.Secondly,considering the uncertainties of the two-rotor aircrafts internal system model and the external unknown disturbance,the adaptive updated laws are designed to estimate the upper bounds of the uncertainties of the internal system model and the external unknown disturbance,no prior knowledge of the internal model uncertainty and the external unknown disturbance in advance.A finite-time adaptive attitude control scheme is proposed based on finite-time attitude control and adaptive updated laws.The Lyapunov synthesis is provided to show that the sliding mode variable,attitude error and velocity error could be uniform ultimate boundedness and converge to the neighborhood of the equilibrium within the finite time.The experimental results validate the effectiveness and superiority of the proposed scheme on the twin-rotor test platform.Considering that the upper bounds of the system state variables convergence time in the finite-time control scheme are related to the initial values of the state variables,a fixed-time attitude control scheme is proposed to ensure that the upper bound of the system state variables convergence time is determined by designable parameters and irrelevant to the initial values of the state variables.And on this basis the adaptive uptaed laws are designed to estimate the upper bound of the uncertainties of the internal system model and the external unknown disturbance.The Lyapunov synthesis is provided to show that the sliding mode variable,attitude error and velocity error could converge to the neighborhood of the equilibrium within the fixed time and and the settling time is independent of initial states.The experimental results validate the effectiveness and superiority of the proposed scheme and the influences of sign function on system control performance on the twin-rotor test platform.Different from the aforementioned control schemes,which avoid the singularity problem indirectly by a piecewise continuous function,a fixed-time adaptive attitude control scheme based on a novel non-singular terminal sliding mode surface is proposed for twin-rotor to solve the saturation problem of system control input.A novel non-singular terminal sliding mode surface is constructed and a fixed-time controller is designed accordingly.The singularity problem in the controller design could be avoided through constructing an auxiliary function.The adaptive update laws are developed to estimate the upper bounds of the lumped uncertainties and external disturbances,such that the prior knowledge on the bounds is not require.The Lyapunov synthesis is provided to show that the sliding mode variable,attitude error and velocity error could converge to the neighborhood of the equilibrium within the fixed time,and the settling time is independent of initial states.The experimental results validate the effectiveness and superiority of the proposed scheme on the twin-rotor test platform.Finally,in the dissertation,comparative experiments of three designed attitude control schemes are designed.The step response,three different transition time curves,combined rectangular waves and sine waves with multiple amplitude are selected as the defined trajectories of the experiments.The experimental results on the twin-rotor test platform show the fixed-time adaptive attitude control scheme based on a novel non-singular terminal sliding mode surface has better transient response speed and smaller attitude tracking error,the fixed-time adaptive attitude control scheme takes second place and is superior to the finite-time adaptive attitude control scheme.