Nonlinear Control Law Design And Simulation For Unmanned Small-scaled Helicopter

Unmanned helicopter (UH) has the ability of vertical taking off and landing, hovering and pivot turning as common helicopter. Besides, UH is also of strong mobility, flexibility and has the feature of'none casualty', etc. Because of all the advantages above, UH has received growing attention. However, UH is of complex dynamics, and has a multivariate and nonlinear system with strong coupling, and all the above result to a strong demand for designing a flight control system for UH with better performance. However, the accomplishment of helicopter dynamics modeling is a prerequisite for such designing.This paper presents a method of helicopter dynamics modeling based on Lagrange's equation. Taking a scale model helicopter as an example, the author tries to build a reduced-order model (3-DOF) using the Second Lagrange's equation. Based on this, a linearized model is achieved on the basis of the small disturbance linear theory. A PID control law, with which the linearized model and the nonlinear model are stabilized and controlled respectively, is designed for the linearized model. Some simulation results demonstrate that the PID control law has a good controlling ability of the linearized model, but is not well available for the nonlinear model.The linearized model is difficult to fully reflect the nonlinear nature, so the linearized control law fail to control the nonlinear model well. Backstepping and zero-dynamic methods respectively are applied to design control law for the nonlinear model. The simulation results demonstrate that the control law made by these two designing styles can be effectively applied to stabilize and control the nonlinear model.Mathematical simulation results can only be used to prove that the control algorithm is reasonable. In order to verify the closed-loop system is a Real-time simulation system, dSPACE Real-time simulation system is applied to construct the rapid control prototyping of helicopter flight control system. By contrasting the results of mathematical simulation and Real-time simulation, the control law designed above is tested to be effective, and lays the foundation for the Hardware-in-the-Loop Simulation and the semi-physical simulation.