Mathematical Model and Vibration Analysis of Aircraft with Active Landing Gear System using Linear Quadratic Regulator Technique

This paper deals with the study and comparison of passive and active landing gear system of  the aircraft and dynamic responses due to runway irregularities while the aircraft is taxying. The dynamic load and vibration caused by the unevenness of runway will result in airframe fatigue, discomfort of passengers and the reduction of the pilot’s ability to control the aircraft. One of the objectives of this paper are to obtain a mathematical model for the passive and active landing gears for full aircraft model. The main porpuse of current paper is to design Linear Quadratic Regulator (LQR) for active landing gear system that chooses damping and stiffness performance of suspension system as control object. Sometimes conventional feedback controller may not perform well because of the variation in process dynamics due to nonlinear actuator in active control system, change in environmental conditions and variation in the character of the disturbances. To overcome the above problem, this research designs a controller for a second order system based on Linear Quadratic Regulator. The performance of active system is compared with the passive landing gear system by numerical simulation. The results of current paper in compared with the previous work mentioned in reference, demonstrate 37.04% improvement in body acceleration, 20% in fuselage displacement and 13.8% in the shock strut travel. The active landing gear system is able to increase the ride comfort and good track holding by reducing the fuselage acceleration and displacement and load induced to airframe caused by runway excitation.