Carlos M. Pereira

A class of polarized cavity orientation sensors

A robust onboard full angular orientation sensor solution, based on a polarization scanning reference source and polarized geometrical cavity orientation sensors is presented. The sensor system provides a new non-GPS and non-inertial approach to angle measurements, with several key advantages over other methods, which include traditional phased-array antenna systems and the like. In this novel approach, the angular orientation information is coded into a time dependent pattern, which is insensitive to noise, while making the angle measurement independent of distance from the referencing source. The manuscript presents data from a field deployable system.

A review of piezoelectric-based electrical energy harvesting methods and devices for munitions

This paper presents a review of piezoelectric based energy harvesting devices and their charge collection and storage electronics for use in very harsh environment of gun-fired munitions. A number of novel classes of such energy-harvesting power sources that have been developed for gun-fired munitions and similar applications, including one with integrated safety and firing setback event detection electronics and logic circuitry. The power sources are designed to harvest energy from firing acceleration and vibratory motions during the flight. As an example, the application of the developed piezoelectric based energy harvesting devices with event detection circuitry to the development of self-powered initiators or switching devices with full no-fire safety circuitry for protection against accidental drops, transportation vibration, and other similar low amplitude accelerations and/or high amplitude but short duration acceleration events is presented. The designs allow the use of a very small piezoelectric elements, thereby making such devices to be highly miniaturized. These devices can be readily hardened to withstand very high G firing setback accelerations in excess of 100,000 G and the harsh firing environments. The design of prototypes and testing in shock loading machines, air guns and actual firing are presented.

Non-GPS full position and angular orientation onboard sensors for moving and stationary platforms

Angular orientation of both mobile and stationary objects continues to be an ongoing topic of interest for guidance and control as well as for non-GPS based solutions for geolocations of assets in any environment. Currently available sensors, which include inertia devices such as accelerometers and gyros; magnetometers; surface mounted antennas; radars; GPS; and optical line of sight devices, do not provide an acceptable solution for many applications, particularly for gun-fired munitions and for all-weather and all environment scenarios. A robust onboard full angular orientation sensor solution, based on a scanning polarized reference source and a polarized geometrical cavity orientation sensor, is presented. The full position of the object, in the reference source coordinate system, is determined by combining range data obtained using established time-of-flight techniques, with the angular orientation information.

Piezoelectric-based hybrid reserve power sources for munitions

Reserve power sources are used extensively in munitions and other devices such as emergency devices or remote sensors that have to be powered only once and for a relatively short duration. Current chemical reserve power sources, including thermal batteries and liquid reserve batteries require sometimes in excess of 100 msec to become fully activated. In many applications, however, electrical energy is required in a few msec following the launch event. In such applications, other power sources have to be provided to provide power until the reserve battery is fully activated. The amount of electrical energy that is required by most munitions before chemical reserve batteries are fully activated is generally small and can be provided by properly designed piezoelectric-based energy harvesting devices. In this paper the development of a hybrid reserve power source obtained by the integration of a piezoelectric-based energy harvesting device with a reserve battery that can provide power almost instantaneously upon munitions firing or other similar events is being reported. A review of the state of the art in piezoelectric-based electrical energy harvesting methods and devices and their charge collection electronics for use in the developed hybrid power sources is also provided together with the results of testing of the piezoelectric component of the power source and its electronic safety and charge collection electronics.

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

This paper presents a review of piezoelectric based energy harvesting devices and their charge collection electronics for use in very harsh environment of gun-fired munitions. A number of novel classes of such energy harvesting power sources have been developed for gun-fired munitions and similar applications, including those with integrated safety and firing setback event detection electronics and logic circuitry. The power sources are designed to harvest energy from firing acceleration and vibratory motions during the flight. As an example, the application of the developed piezoelectric based energy harvesting devices with event detection circuitry for the development of self-powered initiators with full no-fire safety circuitry for protection against accidental drops, transportation vibration, and other similar low amplitude accelerations and/or high amplitude but short duration acceleration events is presented. The design allows the use of a very small piezoelectric element, thereby allowing such devices to be highly miniaturized. These devices can be readily hardened to withstand very high G firing setback accelerations in excess of 100,000 G and the harsh firing environment. The design of prototypes and testing under realistic conditions are presented.

A novel class of MEMS accelerometers for guidance and control of gun-fired munitions

The state of art in shock resistant MEMS accelerometer design is to reduce the size of the proof-mass, thereby reducing the generated forces and moments due to shock loading. Physical stops are also provided to limit proof-mass motion to prevent damage to various moving components. The reduction of the proof-mass size reduces the sensor sensitivity. In addition, to increase the sensor dynamic response, proof-mass motion needs to be minimally damped, resulting in a significant sensor settling time after experiencing a high shock loading such as those experienced by gun-fired munitions during firing. The settling time is particularly important for accelerometers that are used in gun-fired munitions and mortars for navigation and guidance. This paper describes the development of a novel class of accelerometers that are provided with the means of locking the sensor proof-mass in its “null” position when subjected to acceleration levels above prescribed thresholds, thereby protecting the moving parts of the accelerometer. In munitions applications, the proof-mass is thereby locked in its null position during the firing and released during the flight to begin to measure flight acceleration with minimal settling time. Details of the design and operation of the developed sensors and results of their prototyping and testing are presented. The application of the developed technology to other types of inertial sensors and devices is discussed.

A novel method for full position and angular orientation measurement of moving objects

Angular orientation of an object such as a projectile, relative to the earth or another object such as a mobile platform continues to be an ongoing topic of interest for guidance and/or steering. Currently available sensors, which include inertia devices such as accelerometers and gyros; magnetometers; surface mounted antennas; radars; GPS; and optical line of sight devices, do not provide an acceptable on-board solution for many applications, particularly for gun-fired munitions. We present a viable solution, which combines open-aperture sensors with custom designed radiation patterns and one or more amplitude modulated polarization scanning reference sources. Subsequently, the sensor system presents a new approach to angle measurements, with several key advantages over traditional cross-polarization based rotation sensors. Primarily, angular information is coded into a complex spatiotemporal pattern, which is insensitive to power fluctuations caused by environmental factors, while making the angle measurement independent of distance from the referencing source. Triangulation, using multiple sources, may be also used for onboard position measurement. Both measurements are independent of GPS localization; are direct and relative to the established local referencing system; and not subject to drift and/or error accumulation. Results of laboratory tests as well as field tests are presented.

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

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.

Piezoelectric-based event sensing and energy-harvesting power sources for thermal battery initiation in gun-fired munitions

A novel class of piezoelectric-based energy harvesting devices with integrated safety and firing setback event detection electronics and logic circuitry that can be used in gun-fired munitions is presented. In this paper, the application of the device to the development of initiators for thermal reserve batteries in gun-fire munitions is presented. The novel and highly efficient electrical energy collection and storage and event detection and safety electronics used allows the use of a very small piezoelectric element. As a result, such devices can be highly miniaturized for used in small reserve batteries. For thermal battery initiation, when the prescribed firing setback acceleration profile, i.e., the prescribed all-fire condition is detected, a highly efficient charge collection electronic circuitry routes the charges generated by the piezoelectric element of the device to the initiator bridge element, thereby causing the thermal battery pyrotechnic material to be ignited. For munitions powered by thermal reserve batteries, the present initiation device provides a self-powered initiator with full no-fire safety circuitry for protection against accidental drops, transportation vibration, and other similar low amplitude accelerations and/or high amplitude but short duration acceleration events. The device is shown to be readily set to initiate thermal batteries under almost any all-fire conditions. The device can be readily hardened to withstand very high G firing setback accelerations in excess of 100,000 G and the harsh firing environment. The design of prototypes and testing under realistic conditions are presented.

Novel motion-doubling mechanism for improved piezoelectric energy-harvesting performance

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.