Design Method Of Variable Buffer Protection System For Towbarless Vehicle

Under towing or pushing back operation of aircraft,the aircraft towbarless vehicle dirver may make a sudden acceleration or sudden braking behavior based on hedging considerations or emergency response,which is caused by poor operating environments,unexpected events or improper operations.Which can cause excessive traction load that leads to an accident once it exceeds the load limits of the nose landing gear of aircraft and its related components.Therefore,a new aircraft towbarless vehicle with a variable buffered protection is proposed.It can unload the excessive traction load.The Douglas TBL200 is retrofitted with four parallel variable buffers between the frame and the clamping-lifting device to form an "aircraft towbarless vehicle(frame-variable hydraulic buffers-clamping and lifting device)-aircraft" variable buffer towbarless system.The radial dimensions of the hydraulic cylinder are determined by the hydraulic cylinder design principles.A semi-active control method is proposed to control the buffer.This control method can accomplish variable buffer protection function with few control valves.Firstly,Hydraulics plug-in of ADAMS is used to establish the hydraulic system.The buffer distance of the variable hydraulic buffer,the relevant parameters of the control valve and the main structure size of the variable buffer are determined by the most dangerous working conditions in acceleration and braking.Then,when the buffer control valve is not opened,the stiffness of the buffer is calculated theoretically and simulated.The results show that the longitudinal stiffness of the aircraft towbarless vehicle is enough without affecting the normal towing operation when the variable hydraulic buffer is not working.Finally,through the simulation study of different traction and braking conditions,the simulation results show that the variable hydraulic buffer aircraft towing vehicle transformed from Douglas TBL200 can cope with all the sudden situations in straight driving,so that the traction load of the nose landing gear of A320-200 aircraft is less than the maximum allowable load value of 94250 N.The design will protect the aircraft from the irregular traction operation of the airport.