Characterization of vibration motors for micro aerial vehicles

Abstract

In the search for a lightweight ornithopter micro aerial vehicle (MAV), conventional actuation using gears and crank mechanism to couple an electric motor to flapping wings are stumbling blocks in weight-saving efforts. An alternative was to mount a vibration motor on an elastic wing-flapping compliant mechanism to achieve actuation via simple harmonic motion. However, the performance of vibration motors mounted on elastic platforms had not been defined before as they were largely intended for rigid mounting on printed circuit boards (PCBs).

Thus, the objectives of this project were to develop and validate a reliable experiment to characterize the performance of a vibration motor mounted on different elastic platforms and to draw conclusions on the actuation capability of the vibration motor to drive wing-flapping mechanisms in MAVs.

In the development of a valid and reliable experiment, a vibration model based on a single-degree-of-freedom spring-mass system was adopted, using the free end of a cantilevered beam as the representative point for such a system. A vibration motor attached to this point was operated over a range of voltages and characterized in terms of displacement amplitude, force amplitude, frequency and electrical parameters. Different cantilever lengths were used to study the effects of stiffness on vibration motor performance.

It was shown that displacement amplitude tends to maximum value near resonance and increases with decreasing stiffness. Force amplitude also tends to maximum value near resonance, but decreases with decreasing stiffness. Stiffer support leads to higher frequency, even at the same voltage. When approaching resonance, power increases drastically while resistance drops.