Research On Property And Semi-active Control Of Landing Gear Shock Absorption System

Aircrafts would endure heavy load during landing or running on uneven runway at high speed. Shock absorption system is equipped on the modern aircraft landing gear to alleviate heavy load efficiently. The shock absorbing performance of landing gear will directly affect the aircraft's structure strength, safety and ride comfort.Compared with passive control, semi-active control system can change its parameters according to outside situation to achieve high damping performance. And the control performance of semi-active control system approaches to full active control system without additional energy power. As a result, semi-active control system is more simple, stable and safety. By means of test and simulation, the property and semi-active control technology of landing gear shock absorption system are studied.A drop test rig for small aircraft landing gear is designed and set up. Compared with general test rig, some structures of our rig are specially designed to remarkably reduce friction and vibration during drop. A comprehensive data acquisition and process system is built for research in detail.According to the work condition of drop test rig, a mathematical model of the shock absorber is built and relative test device is designed. By parameter identification and experiment, this dissertation makes research on air poly-tropic exponent, axial friction of shock absorber, orifice discharge coefficient and tire force. Based on the mathematical model, the drop process is simulated and furthermore, the results show that the model is accurate and credible.Control device is one of the key problems on landing gear semi-active control. In this dissertation, high-speed solenoid valve is used for control whose non-linear mathematical model is developed. In addition, several experiment corroborated the simulation results.A semi-active control test rig based on parallel high-speed solenoid valves is built. PD control law based on acceleration signal feedback is designed for drop test. The results reveal that semi-active control strategy based on parallel high-speed solenoid valves is feasible and adapted to the nose gear of small aircraft. Nevertheless, it may not be used for main gear because of the valve's low flux.Several control law, such as parameter self-regulating fuzzy PD controller, model-based PD controller, model-based neural network adaptive controller are adopted successively to do deep research on landing gear semi-active control law by simulation. The results show that the latter gains better performance.