Adaptive Modeling And Control Design For A 3-DOF Helicopter

With the development of the technology and society, the requirement for modern equipments with guaranteed diversity, stability and mutual performance is increasingly high, which makes more strict commands to the control system to meet the demands of users. Helicopters can make a low motion (several meters off the ground), hover at low speed (start from suspending) and fly at a constant direction of the head of plane, especially can make vertical take-off and land in a small area. Meanwhile, the helicopter is widely used for people and goods transportation, searching and rescuing, disaster relief, fire control in cities and forest, and other fields of the aircraft. Since the helicopters are widely required for many industries, the state has paid more attention to this industry and developed strategy to help the development of plane, and it also brought challenges and opportunities for the helicopter’s development.3-DOF helicopter system is a simplified model of the helicopter, and is also the objective on which this thesis is focused.3-DOF helicopter is a multiple-input and multiple-output system which has strong coupling and nonlinear characteristics. Therefore, it is a complex plant that should be controlled via advanced control methods. For 3-DOF helicopter system, PID control is one of the widely-used control methods; and the PID control design is relatively common because it is simple, with good robustness and high reliability. PID control is widely used in the process and motion control, and particularly suitable for the system, which is difficult to obtain an accurate mathematical model. When PID control is applied to nonlinear systems, the control performance may degrade and not be able to meet the requirement. Other advanced control strategies, e.g. nonlinear control, adaptive control. Compared with other control methods, the salient features of the adaptive control are:it can adjust online the estimated parameters and thus reduce the model uncertainties which will improve the control performance in a certain way, making the system follow the given command.In this paper, a new adaptive control method is proposed, which will be applied for the 3-DOF helicopter system to verify its feasibility. First, to apply the adaptive control in the parameter estimation, it is time to discuss how to build the model of the helicopter, through which the input or output data and part system information are used to estimate the unknown parameter. Meanwhile, to overcome the unknown dynamic difficulty, neural network is introduced to develop the adaptive neural network controller, realizing the goal of control and guarantee the stability of the closed-loop system. Finally, a novel adaptive law is proposed based on the parameter estimation error, and at the same time realize the parameter estimation and control. The basic idea of adaptive control is:construct a new adaptive parameter learning law; online learning to the estimation parameters rapidly approach to the real value of the parameters. According to the simulation and experiment, the new proposed adaptive control algorithm is not only well satisfying the control requirement of given signal, but also it is rapidly obtaining the parameters estimation which are close to the real value. Therefore, this research results will be make a foundation for the adaptive control in the future.