Location Corrections Through Differential Networks System

The electrical transmission lines used to transmit power are optimized for 50 to 60 Hz waveforms, but are suitable for waveforms of higher frequencies, into the megahertz range. Therefore, powerline conductors are capable of transmitting signals which could be used for geolocation. Indeed, frequencies in the 100 kHz range are used for diagnostic purposes in contemporary power grids today. Signals transmitted in this band are used to verify the operation of sites along the power grid, are used to configure the power grid (for example, throw a circuit breaker). The technology takes advantage of the suitability of electrical conductors employed in power transmission for signal transmission in the sub-megahertz range, and, in the preferred embodiment, utilizes the existing diagnostics signals in this range for geolocation.

While real-time positioning computed by standard GPS service is adequate for some onboard applications, inherent position discontinuities are not acceptable for high-precision instrument applications, such as view-period prediction and maneuver planning, both of which are computations that require a continuous prediction of the spacecraft state. Real-time positioning also requires simultaneous measurements from four GPS satellites, a mission-limiting factor that must be considered. GEONS processes data from standard GPS receivers, onboard communication equipment, and/or attitude sensors, producing accurate absolute and relative navigation solutions in real time. Other functions, including onboard maneuver control and relative navigation for keeping formations are also supported by GEONS. All information is quickly available to scientists when it is included in the down-linked telemetry stream. GEONS provides high-quality solutions with fewer than four visible GPS space vehicles by employing an extended Kalman filter (EKF) augmented with physically representative models for gravity, atmospheric drag, solar radiation pressure, clock bias, and drift to provide accurate state estimation and a realistic state error covariance. GEONS incorporates the information from all past measurements—carefully balanced with GEONS’ data of the physical models governing these measurements—to produce an optimal estimate of the user spacecraft’s orbit. GEONS’ high-fidelity state dynamics model reduces sensitivity to measurement errors and provides high-accuracy velocity estimates, permitting accurate state prediction during signal outages or degraded coverage. Autonomous navigation reduces total mission cost by eliminating the need for routine, ground-based orbit determination and special tracking services, and it is required for advanced mission concepts, such as satellite formation flying. GEONS was designed for autonomous operation within the very limited resources of an onboard computer. Autonomous initialization and enhanced fault detection capabilities are implemented using instantaneous geometric GPS solutions. By incorporating information from past measurements, GEONS provides highly accurate orbit estimates even with one visible GPS space vehicle—and even during signal outages or degraded coverage. This unprecedented accuracy and reliability reduces navigation errors and does it autonomously with minimal onboard computer resources. Additionally, GEONS processes Doppler measurement data from onboard attitude sensors. These different types of measurements are all incorporated into the GEONS software, producing a navigation system capable of handling multiple orbit regimes and navigation subsystems, while requiring no additional hardware. Fusion of these data types increases system stability and reliability and enables graceful degradation in the event that a component fails during orbit.

The innovation builds upon conventional UWB hardware by incorporating tracking methodology and algorithms in addition to external amplifiers for signal boost. The tracking methodology is a triangulation calculation consisting of Angle of Arrival (AOA) and Time Difference of Arrival (TDOA) using a cross-correlation peak detection method. By directly estimating TDOA information from UWB pulses, the method achieves the high temporal resolution (on the order of picoseconds) needed to measure AOA with extreme precision. The system uses a PC to synchronize and process data in real time from two receivers, or clusters, to display the position of the transmitter-equipped person or object. The interface software enables the PC to access the two data sets simultaneously through separate sockets. In the data collection process, data segments from each receiver are interleaved with those from the other receiver in chronological order of collection. Within the PC, the data segments are stored in a separate buffer; therefore, the contents of the buffers are representations of the same UWB pulse waveform arriving at the two receivers at approximately the same time. This data synchronization provides the separate and simultaneous collection of waveform data that the tracking algorithm requires for accurate real-time tracking.

Commonly used RFID protocols are widely accepted because they are inexpensive and easy to implement. However, the associated low transmit power and narrow bandwidth typically result in coarse local-ization estimates. Often it is desirable to know the precise location of assets without reverting to an entirely different and more expensive protocol. Additionally, many industrial and other applications may desire technology that confirms the mating of components. This new program-mable sensor tag technology facilitates both precise localization and mating confirmation in-part by allowing the RFID sensor tag to become a type of distributed low-cost reader. To determine a tag attachment, this innovation utilizes a fixed location RFID sensor tag that incorporates a receptacle node to measure an electrical “influence” through resistance, capacitance, inductance, etc. Assets for which localization is desired are outfitted with “influence tags” – devices that produce a set of distinguishable responses when placed in the receptacle region of the RFID sensor tag. Mating or connections are confirmed when electrodes from an influence tag become attached to matching electrodes on a sensor tag’s receptacle node. Information obtained by the RFID sensor tag is stored in its local memory bank through which a dedicated reader can retrieve influence tag information. Potential applications exist for this technology where specific assets need to be precisely located and/or confirmation is needed when two parts have been correctly connected or attached. This RFID tag technology allows the retrieval of inventory status information in an energy efficient manner from inexpensive, small form factor hardware. Robotic retrieval of assets can be more easily facilitated with this innovation.

Current RFID readers, such as the EPC Global Class 1 Gen 2, are limited by narrow bandwidth restrictions, maximum transmit power, and a limited number of RF ports, which results in relatively coarse ranging resolution and accuracy, limited techniques for localization, and limited antenna functionality. Some of the currently available solutions, such as using larger antennas or adding switched multiplexers, often result in unacceptable cost, volume, aesthetics and mass penalties. The Agile RFID Antenna System integrates a frequency multiplexer into the RFID reader antenna system to provide greater antenna functionality without requiring additional reader RF ports, resulting in improvements in reader-tag communications read accuracy, read range, and localization. The Agile RFID Antenna System is at a TRL 8 (Technology has been proven to work in its final form and under expected conditions) and has been used on the International Space Station to support logistics management and it is now available for your company to license and develop into a commercial product. Please note that NASA does not manufacture products itself for commercial sale.