Force sensing of an asymmetric dielectric barrier discharge using mechanical resonators

Dielectric barrier discharge (DBD) plasma actuators are of great interest in flow control research and application. DBD plasma actuators are low-cost, lightweight, high voltage devices that have the capability of generating small amounts of thrust on the order of a few tenths of a gram. The thrust is created by rapidly pulsing plasma discharges which correlate to the frequency of the applied alternating current waveform, in the low kilohertz range. Plasma actuators experience a reactant force generated by the pulsed plasma charging and then expelling air away from the charged surface. This force fluctuates with time as the plasma is created and then extinguished, twice per cycle for a sine wave input. This research uses tuned harmonic resonators to amplify the motion of a plasma actuator, which for a 10 gram actuator is less than one nanometer in distance per cycle. Reflective mirrored stainless steel double-clamped beams are used in conjunction with a laser interferometer system capable of resolving 0.0791 nanometers at a bandwidth of 50MHz. Resonators designed for this application provide motion amplification of 100 times or greater. The total system, although highly sensitive to outside motions, is capable of detecting nanometer and sub-nanometer motion of a plasma actuator running at nominal voltages of 6.5-9.3kV and a frequency of 3kHz. Periodic displacements, and the forces that cause them, are measured --Abstract, page iii