A transponder is a radio or radar transmitter and receiver that responds to an incoming signal either by broadcasting its own predetermined signal (as in aircraft identification systems) or by relaying the incoming signal at a different frequency (as in satellite communications). They are used in different industries from aviation and marine to automotive and motorsports for a range of applications such as navigation and collision avoidance in air traffic or lap timing purposes in sport car racings. Depending on the application of the transponder, it may be subjected to different environmental disturbances such as mechanical shock and vibration, high pressures or thermal excitations.
Our first goal in this project funded by DSO national laboratories of Singapore, was to conduct high-velocity impact analysis of a military transponder which contained sensitive internal components such as batteries, antenna SATCOM card and other circuit boards dropped from drones at high altitudes. Next, we wanted to protect it against large imparted impact when it hits the ground. With extensive finite element analysis in different ground conditions, we showed that the original cushioning design that was an EPS foam was completely ineffective. Instead, we devised an air cushioning system that could effectively absorb the impact shock similar to the landing airbag system of the Mars Rover. However, an additional challenge was the available space limitation in the drones carrying the transponders as well as the landing accuracy of the transponders which would have been compromised if the cushioning system was inflated from the beginning; hence, we designed a smart cushioning system that could sense when the transponder was about to hit the ground to inflate the air cushions right before the impact.