Piezoelectric-based electrical energy harvesting and storage methods and electronics for munitions

Abstract

The U.S. Armament Research development Center (ARDEC) and the Army Research Laboratories in Adelphi, Maryland, and their small business collaborator (Omnitek Partners, LLC) have been developing alternatives to current reserve batteries for certain munitions applications. It is shown that using a novel passive method, efficiency of over 70 percent could be achieved in the transfer of generated electrical charges to appropriate selected storage mediums. The paper also describes the development of test-beds to simulate electrical charge generation of the energy harvesting power sources during the firing and the flight for use in the design and evaluation of the collection electronics. INTRODUCTIONIn recent years, particularly following the development of low-power electronics, sensors and wireless communications devices, electrical energy generators that harvest energy from the environment have seen renewed attention. In this area, piezoelectric materials have been widely used to generate electrical energy from ambient vibration. Such electrical energy generators and methods of collecting, regulating and storing the generated electrical energy have been the subject of numerous studies (e.g., see [1][2][3][4][5][6]). For a review of the published literature on energy harvesting and related areas, the reader is referred to [7].Harvesting energy from transient high-shock events such as gun-firing and converting it to usable electrical energy is also not new. Part of the work on this type of energy harvesting, particularly for applications on-board gun-fired projectiles have been reported in [8][9][10][11][12][13][14][15][16][17][18]. The developed piezoelectric power generators are generally suitable for applications with low to medium power requirements. To date, several such piezoelectric-based power generators have been developed and tested for fuzing applications, which are designed to produce energy from firing setback acceleration.The launch environment of gun fired munitions provide high setback accelerations. Most munitions are also subjected to vibration and wobbling oscillations. Different methods for effective generation of electrical energy from firing setback acceleration and flight vibration and wobbling oscillations have been described in [8-13 and 15-17]. In munitions applications, the main motivation for using the described energy harvesting is the development of miniaturized power supplies to provide munitions with very fast power-up capability; to incorporate safety features with the powering up process; and to improve the shelf-life and temperature performance of the power source to meet military operational and storage temperature requirements of -65 to +175 º C and a shelf life of 20 years.Power sources developed with piezoelectric-based energy harvesting devices have been shown to be capable of replacing chemical-based power sources to meet many of munitions and fuzing power requirements, particularly where electrical energy of the order of 100 milli-Joules is to be provided. These power sources ...

Piezoelectric energy-harvesting power source and event detection sensors for gun-fired munitions

“…The basic circuitry of a totally passive charge collection and storage electronics for such a "one-shot" energy harvesting devices is shown in Figure 4 and was described in detail in [19]. In this circuitry, the capacitance of the piezoelectric element and the inductor L1 is provided with a significantly higher resonant frequency than the storage capacitor C and inductor L2 resonant frequency.…”

“…In these devices, the shock loading effectively results in a very short duration pulsed loading of the piezoelectric element. Such devices are referred to as "one-shot" energy harvesting power sources or generators [18][19]. The main challenge in both groups, but particularly in the latter group, is that due to the very short duration of shock loading, it becomes difficult to efficiently harvest the charges generated by the device piezoelectric element and store it in a storage device such as a capacitor.…”

“…The actual designs may vary to match the requirements of each application, including the available space, firing acceleration levels, the expected vibration levels and frequencies during the flight, the amount of energy to be produced, etc. For more detail the reader is referred to articles [8][9][10][11][12][13][14][15]17 In general, a single piezoelectric stack of appropriate size, area and height is used and the natural frequency of vibration of the mass-spring unit is selected to optimally match the power requirement of a specific application.…”

“…In these devices, the shock loading effectively results in a very short duration pulsed loading of the piezoelectric element. Such devices are referred to as ``one-shot'' energy harvesting power sources or generators [18][19].…”