This paper describes the development and construction of an energy harvesting device to provide a safe, reliable source
of electrical energy onboard gravity-dropped weapons such as aerial bombs. The generators collect and store mechanical
energy as the weapon falls away from the aircraft. Only after the weapon has fallen away from the aircraft is the stored
mechanical energy released, generating electricity through a hybrid piezoelectric and electromagnetic generation method.
The design, construction, and testing of the generator is discussed at length. Conceptual designs for integrating the
described energy harvester alongside current and alternative sources of electrical power are also discussed.
KEYWORDS: Energy harvesting, Prototyping, Chemical elements, Weapons, Energy efficiency, Control systems, Pollution control, Mathematical modeling, Control systems design, Electronic components
A novel technique is presented for transmitting forces to piezoelectric elements in electrical energy harvesting
applications. The approach results in amplifying any force transmitted to the piezoelectric element. Additionally, the
frequency of any cyclical input force is doubled. The increased performance and scalability of the technique make
possible its employment in a wide variety of energy harvesting applications. The methods and designs may be mated to
a number of intermediate energy harvesting techniques, which are discussed in detail with analysis of complete energy
harvesting devices including specific applications in munitions.
KEYWORDS: Energy harvesting, Electronics, Weapons, Energy efficiency, Control systems, Prototyping, Chemical elements, Capacitors, Pollution control, Mathematical modeling
Novel designs are presented for piezoelectric-based energy-harvesting power sources that are attached to mortar tubes to
harvest energy from the firing impulse. The power sources generate electrical energy by storing mechanical potential
energy in spring elements during the firing. The mass-spring unit of the power source begins to vibrate after firing,
thereby applying a cyclic force to a set of piezoelectric elements to which it is attached. The mechanical energy of
vibration is thereby converted to electrical energy over a relatively long period of time and stored in electrical energy
storage elements such as capacitors. The power sources are shown to provide a significant portion of the required
electrical energy of the fire control system.
A novel class of piezoelectric-based energy-harvesting power sources has been developed for gun-fired
munitions which harvest energy from the firing acceleration. These piezoelectric-based devices have been
shown to produce enough electrical energy for many applications such as fuzing, where they provide an ultrasafe
power source, often eliminating the need for chemical batteries. An overview of the development of these
power sources is provided, along with methods and results of laboratory and field testing performed on
prototypes. Additionally, methods for integrating the generators into different classes of projectiles are
discussed along with strategies for manufacturing and a side-by-side comparison with competing
technologies.
KEYWORDS: Energy harvesting, Electronics, Weapons, Energy efficiency, Control systems, Prototyping, Chemical elements, Capacitors, Pollution control, Mathematical modeling
Novel designs are presented for piezoelectric-based energy-harvesting power sources that are attached to mortar tubes to
harvest energy from the firing impulse. The power sources generate electrical energy by storing mechanical potential
energy in spring elements during the firing. The mass-spring unit of the power source begins to vibrate after firing,
thereby applying a cyclic force to a set of piezoelectric elements to which it is attached. The mechanical energy of
vibration is thereby converted to electrical energy over a relatively long period of time and stored in electrical energy
storage elements such as capacitors. The power sources are shown to provide a significant portion of the required
electrical energy of the fire control system.
KEYWORDS: Energy harvesting, Electronics, Safety, Prototyping, Systems modeling, Packaging, Finite element methods, Sensors, Receivers, Microelectromechanical systems
Several novel classes of piezoelectric-based energy-harvesting power sources are presented for very high-G gun-fired
munitions (40,000 - 240,000 Gs). The power sources are designed to harvest energy from the firing acceleration and in
certain applications also from in-flight vibrations. The harvested energy is converted to electrical energy for powering
onboard electronics, and can provide enough energy to eliminate the need for batteries in applications such as fuzing.
During the munitions firing, a spring-mass system undergoes deformation, thereby storing mechanical potential
energy in the elastic element. After release, the spring-mass system is free to vibrate and energy is harvested using
piezoelectric materials. Two distinct classes of systems are presented: First are systems where the spring-mass elements
are loaded and released directly by the firing acceleration. Second are those which use intermediate mechanisms
reacting to the firing acceleration to load and release the spring-mass system.
Description and evaluation of various methods for loading and releasing the spring-mass system in the high-impact
environment, as well as packaging for very-high-G survivability are discussed at length. Also included are methods for
using the devices as hybrid generator-sensors, how the devices intrinsically provide augmented safety, and methods to increase the efficiency of such power sources for very high-G applications.
Examples of a number of prototypes for complete high-G energy harvesting systems are presented. These power sources have been designed using extensive modeling, finite element analysis, and model validation testing. The results of laboratory, air-gun and firing tests are also presented.
A novel class of two-stage piezoelectric-based electrical energy generators is presented for rotary machinery in which
the input speed is low and varies significantly, even reversing. Applications include wind mills, turbo-machinery for
harvesting tidal flows, etc. Current technology using magnet-and-coil rotary generators require gearing or similar
mechanisms to increase the input speed and make the generation cycle efficient. Variable speed-control mechanisms are
also usually needed to achieve high mechanical to electrical energy conversion efficiency.
Presented here are generators that do not require gearing or speed control mechanisms, significantly reducing
complexity and cost, especially pertaining to maintenance and service. Additionally, these new generators can expand
the application of energy harvesting to much slower input speeds than current technology allows.
The primary novelty of this technology is the two-stage harvesting system. The harvesting environment (e.g. wind)
provides input to the primary system, which is then used to successively excite a secondary system of vibratory elements
into resonance - like strumming a guitar. The key advantage is that by having two decoupled systems, the low-andvarying-
speed input can be converted into constant and much higher frequency vibrations. Energy is then harvested
from the secondary system's vibrating elements with high efficiency using piezoelectric elements or magnet-and-coil
generators. These new generators are uncomplicated, and can efficiently operate at widely varying and even reversing
input speeds.
Conceptual designs are presented for a number of generators and subsystems (e.g. for passing mechanical energy
from the primary to the secondary system). Additionally, analysis of a complete two-stage energy harvesting system is discussed with predictions of performance and efficiency.
A novel class of piezoelectric-based energy-harvesting power sources has been developed for gun-fired munitions
and similar high-G applications. The power sources are designed to harvest energy primarily from the firing acceleration,
but from in-flight vibratory motions as well. During the firing, a spring-mass element reacts to the axial acceleration,
deforming and storing mechanical potential energy. After the projectile has exited the muzzle, the spring-mass element
is free to vibrate, and the energy of the vibration is harvested using piezoelectric materials.
These piezoelectric-based devices have been shown to produce enough electrical energy for many applications such
as fuzing, and are able to eliminate the need for chemical batteries in many applications. When employed in fuzing
applications, the developed power sources have the added advantage of providing augmented safety, since the fuzing
electronics are powered only after the projectile has exited the muzzle and traveled a safe distance from the weapon
platform.
An overview of the development of these novel power sources is provided, especially designing and packaging for
the high-G environment. Extensive laboratory and field testing has been performed on various prototypes; the methods
and results of these experiments are presented. In addition to presenting the development and validation of this
technology, methods for integrating the generators into different classes of projectiles are discussed along with strategies
for manufacturing. This technology is currently validated to the extent that prototype devices have been successfully
fired on-board actual gun-fired projectiles, demonstrating survivability and indicating performance. Strategies for
designing the devices for a particular round and transitioning to commercialization are also discussed.
KEYWORDS: Wind energy, Energy harvesting, Chemical elements, Magnetism, Teeth, Energy conversion efficiency, Control systems, Electronics, Prototyping, Ceramics
A novel class of two-stage piezoelectric-based electrical energy generators is presented for rotary machinery in which the input speed is relatively low, varies significantly over time, and is even reversing. This class of energy generators is highly suitable for applications such as wind mills, turbo-machinery used to harvest tidal flows, and the like. Current technology uses magnet-and-coil-based rotary generators. However, to make the generation cycle efficient, gearing or other similar mechanisms have to be used to increase the input speed to the generator. Variable speed-control mechanisms are also usually needed to achieve high mechanical to electrical energy conversion efficiency. This novel class of electrical energy generators uses a decoupled two-stage system. The harvesting environment (wind, tidal flow, etc.) directly provides input to the primary system. The low and varying input motion is then used to successively excite an array of vibrating elements (secondary system). The key advantage is that by having two decoupled systems, the low speed and highly varying input motion is converted into constant and much higher frequency mechanical vibrations, which are then harvested using piezoelectric elements. As a result, by eliminating the need for gearing and speed control mechanisms, the system complexity and cost - including those related to maintenance and service - is significantly reduced. Additionally, these novel generators can expand the application of power generation to much slower input speeds than are harvestable using current technology.
A novel class of piezoelectric-based event sensing and energy-harvesting power sources is presented for gunfired
munitions. The power sources are designed to harvest energy from firing acceleration and vibratory motions during
the flight. The piezoelectric element may be used to measure setback acceleration level, indicate the barrel exit time and
impact time and force levels for fuzing purposes. The developed power sources have the added advantage of providing
safety, since the fuzing electronics are powered only after the munitions have exited the barrel. The developed
piezoelectric-based energy harvesting power sources produce enough electrical energy for applications such as fuzing.
The power sources are designed to withstand firing accelerations in excess of 120,000 G. In certain applications such as
fuzing, the developed power sources have the potential of completely eliminating the need for chemical batteries. The
design of a number of prototypes, including their packaging for high G hardening, and the results of laboratory, air-gun
and firing tests are presented.
Harvesting mechanical energy from ocean wave oscillations for conversion to electrical energy has long been pursued as an alternative or self-contained power source. The attraction to harvesting energy from ocean waves stems from the sheer power of the wave motion, which can easily exceed 50 kW per meter of wave front. The principal barrier to harvesting this power is the very low and varying frequency of ocean waves, which generally vary from 0.1Hz to 0.5Hz.
In this paper the application of a novel class of two-stage electrical energy generators to buoyant structures is presented. The generators use the buoy's interaction with the ocean waves as a low-speed input to a primary system, which, in turn, successively excites an array of vibratory elements (secondary system) into resonance - like a musician strumming a guitar. The key advantage of the present system is that by having two decoupled systems, the low frequency and highly varying buoy motion is converted into constant and much higher frequency mechanical vibrations. Electrical energy may then be harvested from the vibrating elements of the secondary system with high efficiency using piezoelectric elements.
The operating principles of the novel two-stage technique are presented, including analytical formulations describing the transfer of energy between the two systems. Also, prototypical design examples are offered, as well as an in-depth computer simulation of a prototypical heaving-based wave energy harvester which generates electrical energy from the up-and-down motion of a buoy riding on the ocean's surface.
Presented here is an innovative class of piezoelectric-based generators for application in gun-fired
munitions and other similar devices. The generators are designed to produce electrical energy as a result of
the firing acceleration with enough output to power certain on-board electronic circuitry, such as lowpower
fuzing. In this class of piezoelectric-based generators, a novel mechanism is provided with which the
strain applied to the piezoelectric stack can be maintained at its in-firing peak value throughout the flight of
the projectile. As a result, the generated charge can be harvested efficiently during a significantly longer
period of time. In addition, in some munitions applications this can totally eliminate the need for storing the
generated electrical energy in another storage medium. This class of impact-based piezoelectric generator
devices is intrinsically robust in design which makes it suitable for high-G applications. Also, since the
present devices produce energy due to the firing acceleration, a high degree of safety is guaranteed because
the electronics are not powered until the projectile is fired. A basic proof-of-concept design and a
deployable prototype concept are presented which will demonstrate the scalability of the present devices as
well as their survivability in high-G environments.
A novel class of vibration-based electrical energy generators is presented for applications in which the
input rotary speed is relatively low and varies significantly over time such as wind mills, turbo-machinery used
to harvest tidal flows, and the like. Current technology uses magnet and coil based rotary generators to generate
electrical energy in such machinery. However, to make the generation cycle efficient, gearing or other similar
mechanisms have to be used to increase the output speed. In addition, variable speed mechanisms are usually
needed to achieve high mechanical to electrical energy conversion efficiency since speed variation is usually
significant in the aforementioned applications. The objective of the present work is the development of
electrical energy generators that do not require the aforementioned gearing and speed control mechanisms,
thereby significantly reducing complexity and cost, particularly those related to maintenance and service. This
novel class of electrical energy generators operates based on repeated vibration of multiple vibrating elements
that are tuned to vibrate at a fixed prescribed frequency. The mechanical energy stored in the vibration elements
is transformed into electrical energy using piezoelectric elements. The present generators are very simple, can
efficiently operate over a very large range of input speeds, and should require minimal service and
maintenance. The project is at the early stages of its development, but the analytical modeling and computer
simulation studies using realistic system and component parameters indicate the potentials of this class of
piezoelectric-based generators for the indicated applications.
A novel class of piezoelectric-based energy-harvesting power sources is presented for gun-fired munitions and
other similar applications that require very high G survivability. The power sources are designed to harvest energy from
the firing acceleration as well as vibratory motion of munitions during the flight and convert it to electrical energy to
power onboard electronics. The developed piezoelectric-based energy harvesting power sources produce enough
electrical energy for applications such as fuzing. The power sources are designed to withstand firing accelerations in
excess of 100,000 G. In certain applications such as fuzing, the developed power sources have the potential of
completely eliminating the need for chemical batteries. In fuzing applications, the developed power sources have the
added advantage of providing additional safety, since with such power sources the fuzing electronics are powered only
after the munitions have exited the barrel and have traveled a safe distance from the weapon platform. The design of a
number of prototypes, including their packaging for high G hardening, and the results of laboratory and air-gun testing
are presented. Methods to increase the efficiency of such energy-harvesting power sources and minimize friction and
damping losses are discussed.
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