Study on Vibration Characteristics o the Towbarless Aircraft Taxiing System

The civil aircraft nosewheel is clamped, lifted, and retained through the pick-up and holding system of the towbarless towing vehicle (TLTV), and the aircraft may be moved from the parking position to an adjacent one, the taxiway, a maintenance hangar, a location near the active runway, or conversely only with the power of the TLTV. The TLTV interfacing with the nose-landing gear of civil transport aircraft for the long-distance towing operations at a high speed could be defined as a towbarless aircraft taxiing system (TLATS). The dynamic loads induced by the system vibration may cause damage or reduce the certified safe-life limit of the nose-landing gear or the TLTV when the towing speed increases up to 40 km/h during the towing operations due to the maximum ramp weight of a heavy aircraft. In this article, the vibration differential equations for the TLATS are derived based on Newton's second law, and the corresponding matrix formulas are obtained through Laplace transforms. The vibration transmissibilities of the system motion responses to the harmonic road input are evaluated in terms of the frequency response functions (FRFs) in the frequency domain. The simulations are conducted to compare the ride comforts between the TLTV at a low speed of 10 km/h and that at 40 km/h under the random and bump road excitations, respectively. Further, the effects of the aircraft mass, driver seat stiffness coefficient, TLTV center of gravity (CG) location, and the driver seat location on system vibration characteristics in both time and frequency domains are investigated. The results show that the TLTV CG location, the driver seatstiffness coefficient, and location are relatively sensitive to a TLATS's ride comfort, which is significant to the TLTV manufacturer.