Sensors dispense with wires and batteries

A device that converts machine vibrations into electrical energy could revolutionise plant monitoring equipment. The PMG7 microgenerator, developed by Southampton University spin-out company Perpetuum, can be used to power sensors, microprocessors and transmitters - without the expense of batteries, cabling or maintenance. It can also transmit large amounts of data while monitoring. The device could be designed in to almost any type of vibrating equipment. It is already being used by Yorkshire Water, the US Navy and a major oil company - all of whom are looking for significant cost savings. The 'vibration energy harvester' converts kinetic energy - from the vibration of the equipment running at mains frequency (50kHz or 60Hz) - into electrical energy. It can generate up to 5mW, which is enough to power a wireless transmitter, sending up to 6kbytes of critical data every few minutes. Smaller amounts of data - such as a temperature readings - can be transmitted several times each second. It can operate in most industrial environments and at minimal vibration levels. The device uses a magnet and coil arrangement to transform the kinetic energy of vibration into a low power electrical signal. The clever part is in the design of the electronic circuits and the resonant beam. The way these work together means that the device does not have to be precision-tuned for different frequencies. It is designed to resonate at mains frequency with a bandwidth of (0.2Hz, giving excellent performance on any AC synchronous motor-powered equipment. Output is from 0.1mW to several mW of power, depending on the level of vibration (eg. up to 5mW at 100mg or 400(W at 25mg). Around 80% of the cost of condition based maintenance systems is in installation and set up. This is why many companies are now using portable condition monitoring devices. Perpetuum's device eliminates the cost - and time - of installation. The microgenerator is simply screwed into place, or held there by magnets. The device allows operators to continually monitor plant equipment, providing valuable data - such as temperature and vibration spectra - about the condition of equipment, including pumps, motors and fans. This means the data can be used to optimise the efficiency and availability of plant, increase the cost efficiency of maintenance work, to prevent accidents and make significant savings in energy costs. "This is a major breakthrough in the technology," says Roy Freeland, CEO at Perpetuum. "We have completed field trials at Yorkshire Water, the US Navy and an international oil company. This is a practical device, not a laboratory experiment. No competitive offering has come close to this level of performance in terms of the amount of data that can be sent, or the conditions under which it will operate reliably." There have been several partial successes in the search for a truly practical microgenerator, but Perpetuum claims that its device is the most viable to date. "Development work has been carried out with piezomaterials in the past, but their inherent reliability problems proved their downfall," says Freeland. Vibration energy harvesting - the simple idea that the vibration of a piece of plant or machinery could be transformed into an electrical signal - is a very powerful concept with widespread implications for industry. Despite its benefits, continuous condition monitoring is currently carried out on only a very small percentage of installed industrial machinery because of the limitations and cost of the existing wired and battery-powered technologies. Wired systems are too expensive to install on a widespread basis, and wireless, battery-powered systems suffer from reliability and maintenance issues. But vibration energy harvesting is an attractive option for wireless condition monitoring because all mains-driven machinery vibrates. Indeed, the level of its vibration is frequently used as an indicator of its condition. The PMG7 produces much higher levels of power than previous attempts at vibration energy harvesting, claims Perpetuum. It meets the power needs of wireless sensor systems created by the recent development of low power sensors, microprocessors and transceivers. The world-wide market for condition monitoring systems is forecast to grow significantly in the next two to three years. The world-wide plant asset management (PAM) and condition monitoring (CM) market, which totalled almost $900 million in 2002, is predicted to reach almost $1.3 billion by the end of 2007, expanding at a cumulative annual growth rate exceeding 7%, according to a recent study by industry analyst firm the ARC Advisory Group. The report stated that cutbacks in maintenance staff and the new wave of computer-literate maintenance technicians are driving the adoption of new technologies in PAM and CM solutions. In the second edition of a report on the North American Market for 'RF/Microwave Wireless Monitoring and Control Products in Discrete and Process Manufacturing', published in June 2005, Venture Development Corporation forecasted that shipment of RF/microwave wireless products for industrial monitoring and control applications in the US would increase from $154.1 million in 2004 at a compound annual growth rate of 36.6%, reaching $419.3 million by 2007. The PMG7 has been proven in a series of field trials, using the Snap remote sensing module from Perpetuum's US partner, RLW. RLW develops hardware and software for Condition Based Maintenance (CBM) applications. Its devices perform machine health monitoring and provide health status messages to remote destinations. It developed the Snap to exploit vibration energy harvesting after selecting Perpetuum's microgenerator as the best alternative. Six Snap modules are now reporting the health of pumping equipment and blowers at Yorkshire Water's Esholt plant by providing vibration spectra and temperature data for condition monitoring. A Snap module was installed on a compressor at the US Navy's Philadelphia base and demonstrated the transmission of vibration and temperature data. Three further modules were supplied for a trial installation on a test pumping circuit. The devices were readily mounted with magnets onto pumps motors and pipework to produce data for condition monitoring. A new device being developed measures just 5mm by 5mm. It could be used for tyre pressure monitoring systems (where weight and size are key issues) or other automotive applications. The weight of wiring harnesses in cars might also be slashed by switching to wireless sensing. Perpetuum will also unveil a version of the technology for the helicopter industry at the Farnborough Air Show later this month. Perpetuum [Box Out if you've got room] Title: History of the Technology Jan 2005: The first Snap is successfully demonstrated to the US Navy providing temperature data from a compressor completely wirelessly using Perpetuum's early microgenerator. Jan - July 2005: Development work is stepped up, resulting in the rapid development of much more powerful microgenerators capable of producing 80 times more than the original design. July 2005: Won flagship trial contracts from US Navy through RLW Inc., Yorkshire Water and an international oil company. Nov 2005: Successful trial installations of the PMG7-powered Snap with reliable transmission of up to 6kbytes of data. Feb 2006: Received $4 million invesent from Quester funds and Top Technology. Apr 2006: Perpetuum relocates to new facilities at Southampton Science Park. Pointers * The device is the first practical, effective method for wireless, battery-free sensing of almost any type of vibrating equipment * The clever part is in the design of the resonant beam and the electronic circuits * The device is not a laboratory device and OEMs, sensor manufacturers and end users can buy it now