Robust Adaptive Controller Design For UAV Helicopters With Constraints

Unmanned aerial vehicle(UAV)helicopters have been widely used in military and civil areas,which have advantages of simple control,stable operation and strong anti-disturbance during trajectory tracking operation.However,due to the characteristics of high nonlinearity,intense coupling,UAV helicopters possess some demands,such as workspace constraints,safety performance.Therefore,it is a great challenge to design controller for UAV with constraints.For these problems,some works are researched in this dissertation by using the yaw control mode of non-affine nonlinear UAV helicopters with constraints,such as pitch angle saturation,unmeasurable states,state constraints,actuator fault and external disturbance.The details are shown as follows:In order to solve the adverse effects of pitch angle saturation and suppress external disturbance for the yaw tracking of UAV helicopters,we propose a nonlinear disturbance observer-based backstepping sliding mode control.Taylor series expansion technique is adopted to transform the yaw system of non-affine nonlinear UAV helicopters with input saturation to affine form.Nonlinear disturbance observer is given to compensate the unknown compound disturbances.Thus,finite-time backstepping sliding mode controller are put forward,in which the first order filter is introduced to avoid “explosion of complexity” in backstepping control,and auxiliary system is designed to compensate the influence of filtering error.Simulations illustrate the effectiveness of the proposed control method.An extended state observer-based saturation integral backstepping control is proposed for the yaw system of non-affine nonlinear UAV helicopters with unmeasurable states and input saturation.An extended state observer is designed to measure states for the yaw system of non-affine nonlinear UAV helicopters with constraints.Based on this,global approximation method is used to make the control input explicit.To accurately estimate compound unknown disturbances,a super twisting disturbance observer is designed,which makes approximation errors converge to zero in finite time.Then,we derive the anti-saturation integral backstepping controller.Simulations verify that the proposed control method can complete the tracking task and ensure the stability of system.We put forward an adaptive sliding mode disturbance observer-based all states constrained control scheme,directing against the matter for the yaw system of non-affine nonlinear UAV helicopters with yaw angle and angular velocity constraints.Combining taylor series expansion and robust sliding mode filtering technology,the yaw system of non-affine nonlinear UAV helicopters with state constraints is converted into affine form.An adaptive terminal sliding mode disturbance observer is used to estimate unknown disturbances.Based on the above works,a constrained command filter controller is designed by barrier function.Simulations explain the yaw closed-loop system of UAV has good tracking performance.An adaptive neural network fault-tolerant control is shown,when the perturbed yaw system of non-affine nonlinear UAV helicopters is subject to pitch angle saturation,state constraints and actuator failure.The approximate method is applied to make the control variable explicit.To estimate the unknown function,we design the neural network.the adaptive technique is utilized to estimate the unknown parameters at the same time.Furthermore,to eliminate the adverse influence of saturation,we design anti-saturation compensator.On this account,barrier function-based an adaptive neural network fault-tolerant controller is proposed.Simulation analyses illustrate the validity of the proposed control scheme.