Research On Low Altitude Penetration And Terrain Following Of Helicopter

First of all, this paper summarizes the history, actuality and future development trend of aircraft low altitude penetration. The main advantage and problem of helicopter in low altitude penetration is discussed. The significance of the study is demonstrated subsequently. Then, the system structure and the critical problem of subsystems in helicopter low altitude penetration system are analyzed. The features of helicopter are studied, including structure, flight and operation. The mathematics modeling of helicopter is researched based on the analysis of its main aerodynamics components. The control system constitution and strategy of such a complex, nonlinear and strong coupling system is discussed. The helicopter control system is divided into CAS (Control Augmentation System) and PCFS (Path Control Following System), according to the requirement of low altitude penetration system. The PIDNN theory and its remarkable values in multi-variable control system are researched and applied in the CAS designed. The algorithm of critical commands of PCFS is researched. Then, the digital map technique which is closely related to low altitude penetration is studied. The random algorithm of digital map and its interpolation technique is discussed. Considering the helicopter flight capability and the concrete mission target, the algorithm of flight safety surface which is based on digital map is researched, including the conversion of max climb angle, max normal overload and min clearance to terrain gradient limit, terrain curvature limit and clearance limit. The disadvantage of transferring threat to terrain is analyzed and an improved modeling of threat that models threat as a sphere cloud with certain distribution is described. The path planning problems and several intelligent algorithms are summarized and discussed. The principles and characteristics of ACA (Ant Colony Algorithm) are researched. 2-D path planning is obtained using ant colony algorithm based on flight safety surface. Therefore, the optimal 3-D low altitude penetration reference path is derived naturally.