Low power control methods for energy efficient structures

The aim of this proposal is to discover energy efficient control laws for vibration suppression with the goal of running such systems using harvested energy or a combination of harvested and stored energy by exploiting nonlinearity in both the harvesting mechanism and in control law formulation. It is proposed to investigate the concept of using harvested energy to control the vibration response of flexible structures. Structural components in bridges, airplanes, buildings, wind turbines, etc. are flexible and hence are easily disturbed into vibration from a variety of sources. Often the best solution is a passive one, but in many circumstances performance and safety demand the use of semi-active or active control. The major roadblock in using active control is the requirement for an external power source. Here we propose to investigate the possibility that ambient energy might be harnessed, stored and recycled to provide the energy needed to mitigate vibrations through low power nonlinear control laws, enabling better performance of structures in extreme conditions (wind storms, earthquakes, gusts, etc.).

The impact of the proposed research is three fold: reducing waste globally, increasing manufacturing in the UK, and adding to the global science base in vibration suppression and energy harvesting. First consider waste reduction. Currently more then a million tonnes of batteries appear on the market every year and only a few percent are properly disposed of. The proposed effort has the potential to greatly reduce battery waste through not only employing renewable energy but by researching methods to reduce energy consumption and to prolong battery live through integrated recharging. Batteries are used in numerous sensing and control applications and the goal of the proposed research is to reduce the reliance on batteries and/or to extend their useable life. The disposal of batteries has formed the topic of several EU environmental decrees and is a substantial problem facing a green oriented economy. New EU regulations regarding battery disposal underscore the problem and are having an economic impact on products and indirectly on the economy. According to the European commission, mercury, lead and cadmium are the most problematic substances in the battery waste stream and batteries made with these metals are classified as hazardous waste. Improper disposal consists of burning or depositing in landfills. When these waste batteries are burned, they contribute to air pollution and, when they end up in landfill, the metals leach into the surrounding land. Hence the proposed effort addresses an important environmental and economic consideration.

The second impact of the proposed research is in supporting the creation of new products and in enhancing current energy harvesting products. Evidence for this can be found in the attached letters of support from a sample of both small and large manufacturing companies. The letter from e4Structures mentions new manufacturing products specifically by opening a line of energy harvesting devices by opening the controls market to them. The letter from AirBus (UK) mentions the specific impact this research would have on reducing waste in aircraft production and how this research would lead to new products. Specifically they have a range of applications where control action is required, and power is not easily accessible, exactly the problem to proposed research will solve. The letter from Perpetuum mentions "making our products more attractive in the market place". Here they are referring specifically to their line of energy harvesting products. Hence, the proposed effort will have a positive effect on British commercialization.

To date there have been several attempts to commercialize products based on vibration based energy harvesting. However, these attempts have proved problematic, mainly because of one of the difficulties with energy harvesting from vibration sources is that the amount of energy obtained is relatively small. The fact that there are concerted efforts taking place to exploit this type of technology, indicate the high value placed on it as a source of alternative or "green" energy. It's certainly the case, that for autonomous, low power devices the potential impact will be very high.