Colloquia

Summary

Rotating shafts are used in a wide range of applications such as machines, helicopters and in the drive system of cars and trucks. One common problem when using a long slender shaft is the vibration caused by the unbalance of the shaft. The supports of the shaft vibrate due to the vibrations of the shaft, which can influence the performance of other machines. Furthermore, the vibrations cause wear to the bearings and supports which reduce the lifetime. Moreover, the vibrations could also produce noise, which causes discomfort to people around the shaft.

In the past, vibrations of shafts have been studied extensively and various methods to reduce vibrations including rotor fixed actuators were investigated. Control schemes have also been developed for controlling the actuators. Most control schemes are not dependent on the rotational speed, while the system behaviour is dependent on the rotational speed. Little research has been carried out on rotational speed dependent controllers and those controllers have been seldom validated using an experimental set-up. Furthermore, an experimental demonstration set-up was desired at the University of Twente which can be used to study rotor dynamics and active controllers on different rotor materials.

In this master thesis, a dynamic model is formulated to investigate the vibrations of a long and slender solid-shaft with surface fixed piezo elements. Based on the rotor dynamic model, a control scheme is developed to control the vibrations of the shaft by actuating the piezo elements. Strain sensors fixed on the shaft are used to measure the deflection in the shaft and is used as feedback for the controller. Several controllers are developed to investigate which controller is the most effective and results in a stable behaviour.

An experimental demonstration set-up is made to investigate the rotor dynamics of a physical shaft and validate the developed control schemes. It can be concluded that controlling the vibration of the shaft by rotor fixed piezo elements is very effective. The demonstration set-up is performing well within the requirements, and can be used to demonstrate the effectiveness of an active control scheme. Furthermore, the set-up can be used in the future to develop and test controllers with machine learning features, and also investigate the behaviour of shafts made of different materials such as composites with anisotropic properties.