Year

2017

Degree Name

Master of Philosophy (Mechatronics)

Department

School of Mechanical, Materials and Mechatronic Engineering

Abstract

A new modified positive position feedback (M-PPF) controller is proposed as an improved alternative to the positive position feedback controller for use in circumstances where greater control over the damped frequency range is required.

An experimental investigation was conducted using a system consisting of a fully clamped thin aluminium plate mounted to the front face of a cubic steel tank, which was filled with 9 varying amounts of water. The plate was excited via an electromagnetic shaker, and the controller was implemented to attempt to reduce amplitudes for the first four modal frequencies of the plate using an array of sensor/actuator pairs of piezoelectric patches.

It is shown that the M-PPF method can effectively control the first four modes of the system for various water levels, and it is shown in comparison within the literature, that it can be tuned more accurately and precisely than traditional PPF controllers as hypothesised. The overall average amplitude reduction was seen to be 14.8%.

Plate modal frequency and amplitude effects due to changing levels of water were explored. It is found that, in general, modal frequencies follow an overall linear decreasing trend as the water level increases, due to the damping effect the water has on the plate. Strain amplitudes were seen to follow a decreasing trend for the first and fourth mode, and a less prominent, increasing trend for the second and third modes. Amplitude for all modes after the first seems to vary somewhat sporadically, as oscillation at lower amplitudes, as is the case for these modes, is more readily influenced by the movement of the fluid.

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