Abstract

Travelling wave patterns observed in the movement of certain aquatic animals has motivated research in the modification of flow behavior, especially to deal with boundary layer separation in airplane plane wings. Research has shown that inducing travelling waves on the top surface of the wing can generate sufficient momentum to prevent boundary layer separation without increasing the drag. Due to this interesting property, generation of travelling waves on solid surfaces is being widely studied. Recently methods such as two-mode excitation, active sink and impedance matching have shown promise in generation of uniform travelling waves in solids with the help of piezo electric actuators. Unfortunately, there are some challenges involved in the experimental application of these methods. These open loop methods require exact knowledge of the system dynamics therefore, uncertainties in the system dynamics can affect the uniformity and the amplitude of the travelling waves. Some methods rely on selective mode excitation, which can cause interference from unwanted modes if the transient behavior of the system is not accounted. A tracking control method is proposed that augments the open-loop piezo actuation method (two-mode excitation) and provides a more robust method for generating uniform travelling waves. The periodic signal tracking control method drives the output of the temporal part of the distributed parameter system to a desirable output. In addition, the controller alters the reference signal such that the parasitic behavior of unnecessary modes is cancelled out. The combination of the mode suppression and signal tracking deals with the challenges of the piezo actuation methods and add to its performance by improving the quality of the generated wave.

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