Abstract
Recently, an on-rotor sensing (ORS) approach has been actively studied as it allows the sensor element to be mounted on a rotating shaft to accurately capture the dynamic behaviour and thereby used for high performance condition monitoring. Like other wireless devices the ORS nodes are powered by battery or power capacitance units. Frequent recharging or replacement of the batteries leads to additional system service costs and cancels the outstanding merits of service-free and high reliability provided by using wireless sensor systems. To overcome this power supply limit, the project aims to develop a prototype harvesting system for ORS applications.After an extensive literature study on the massive academic publications on the trending subject of energy harvesting, a magnetic-piezoelectric vibration energy harvester (MPVEH) is proposed based hybrid the merits of high efficiency and compact structure of these two approaches. The harvester is modelled with a lumped parameter system, comprehensive simulation and experimental studies were carried out to understand the effect of magnetic sizes and setup distance and layout on the electrical energy output performance. By doing such studies, the following main contributions to the knowledge on the subject of energy harvesting has been made:
• A novel vibration harvesting mechanism based on impulsive excitation is proposed, which controls the output performance at low operating speeds in the prototype MPVEH, therefore widening the harvesting band up to the first vibration bending modes of the cantilever piezoelectric beam assembly.
• Increasing the size and distribution of the external magnets has been found to provide input to the MPVEH that is more effective in improving electric outputs, compared with decreasing the distance between the interacting magnets,
• Another remarkable approach developed is that the first twist vibration mode of the assembly can be activated by the impulsive force from the magnets setting with an offset fixture. Experiments show that it makes more contributions to outputs at full operating speeds, compared with conventional approach workable only around the first bending mode.
• Additionally, it has also been found that the lumped parameter model produces results agreeable with experiments for the horizontal rotors in which gravitational forces is predominantly linear. However, because of the difficulty in accurately modelling the nonlinearity and distortions of the dynamic magnetic forces, the model produces higher prediction than the measured ones. Moreover, it also reminds that magnet fixtures should be more carefully designed to minimise the losses in magnetic flux.
| Date of Award | 7 Jul 2022 |
|---|---|
| Original language | English |
| Supervisor | Andrew Ball (Main Supervisor) & Fengshou Gu (Co-Supervisor) |