Demoz Gebre-Egziabher
McKnight Land-Grant Professor
Research
My research has to do with multi-sensor navigation and guidance systems (sometimes called integrated navigation systems). Multi-sensor or integrated navigation systems combine the information from multiple sensors to generate an estimate of a vehicle's navigation state vector. The entries of the navigation state vector normally consist of the three vehicle's position coordinates, the three velocity components and the parameters used to describe the vehicle's attitude.My research in multi-sensor systems is concerned with the following two broad areas:
- Designing multi-sensor system to address specific navigation and guidenace applications
- Developing algorithms for designing, analyzing and precisely quantifying the performance sensor fusion algorithms.
Research Projects
Use of UAVs at platforms for sensors in traffic monitoring and highway infrastructure management
Remotely sensed data gathered from moving platforms such as Remotely Piloted Vehicles (RPVs) or Uninhabited Aerial Vehicles (UAVs) can address the shortcoming encountered with the traditional method of data collection. RPVs and UAVs are a complimentary technology to ground based cameras and other ITS technologies. They can be flown over land and traffic directly to problem areas. In doing so, they fill large ‘coverage holes’, providing a ‘big picture’ of traffic flow over large portions of the road network. They also fit within the recent framework that addresses transportation security and anti-terrorism measures. This framework, published by the Transportation Security Agency (TSA), emphasizes harnessing ‘dual-use’ technologies that meet the needs of our transportation systems as well as for homeland security roles and law enforcement. Furthermore, RPVs and UAVs do not require (a) risking the lives of highly skilled personnel to fly the aircraft especially under hostile or toxic conditions, or (b) a regional airport to house and provide the landing-takeoff-fueling cycles. And potentially, with adequate 3D feature and terrain knowledge, they may be safely flown at much lower altitudes than manned aircraft (such is the case during low cloud ceilings, etc).
More information
GPS Receiver Design for Ultra-Weak GPS Signals
Over the past decade GPS has become the single most important and ubiquitous utility in modern navigation. Given that GPS-based systems can provide centimeter-level accuracy today, the principle research issues for modern aerospace navigation are not related to accuracy per se, but robustness, which is quantified by the metrics of integrity risk and continuity risk. Integrity risk is the likelihood of an undetected navigation error or failure that results in hazardously misleading information. Continuity risk is the probability of a detected but unscheduled navigation function interruption after an operation has been initiated. One of the major threats to GPS integrity and continuity is signal power attenuation caused by unintentional interference from other radio frequency signals, malicious jamming or signal obstruction in urban environments.
More information
Attitude Determination
Attitude is the term used to describe the orientation of a rigid body in space and an attitude determination system is used to measure attitude. The attitude information generated by these systems are used in many navigation, guidance and control applications such as pilot-in-the-loop control of manned aircraft, geo-referencing images captured from Uinhabited Aerial Vehicles (UAV), Micro Aerial Vehicles (MAV) or satellite operations.Miniature flying vehicles and satellites require attitude determination systems that are compact (see figure on right), consume very littel power and generate an accurate solution. For example, the figure on the left shows the avionics bay of a small aerial vehicle.
More information
GPS-Based Precision Landing Systems
Precision landing systems guide airplanes to the touchdown point on a runway in inclement weather (low visibility) conditions. The civilian precision approach and landing system in current wide use is based on system adopted in the 1940s and relies on analog signals. In the past decade there has been a significant world-wide effort to develop differential GPS-based precision landing systems. A wide-area variant of these systems known as WAAS has been fielded and is currently providing some level of precision guidance services. Local-area variants of these systems are also under development. In the local-area systems, information from the aircraft’s GPS receiver is compared to measurements from a reference GPS antenna at the touchdown point (or close to it). This allows removing common mode errors and when used with the GPS carrier phase observables can result in accuracies on the order of centimeters. This level of accuracy will be required by the local-area system known as Shipboard Relative GPS (SRGPS). SRGPS is the seaborne variant of the Joint Precision Approach and Landing System (JPALS) being developed by the US Department of Defense. SRGPS will support flight operation to and from naval vessels (Pervan, Fang, Gebre-Egziabher, Pullen & et. al, Navigation, 50:181-191).More information
Algorithms for Multi-Sensor Integration
Multi-sensor or integrated navigation systems combine the information from multiple sensors to generate an estimate of a vehicle’s navigation state vector. The entries of the navigation state vector normally consist of the three vehicle’s position coordinates, the three velocity components and the parameters used to describe the vehicle’s attitude. Multi-sensor navigation algorithms used in commercial aviation must not only generate an accurate estimate of the navigation state vector but also meet stringent reliability requirements. One of these reliability requirements is that they must provide a precise bound on the probability with which hazardous navigation errors occur quantified by the metric of integrity.
More information
Small Satellite Design
The mission for Nanosat-5 is to design, construct and validate a GPS bistatic radar for remote sensing applications onboard small satellites in low Earth orbit. The mission can be accomplished by using Goldeneye to collect GPS signals that are reflected off of the Earth’s surfaces, such as land, ocean or ice. Goldeneye is considered a remote sensing device because the reflected GPS signals it collects provide a lot of information. For example, ocean conditions such as wave height and wind speed affect the properties of the GPS signals that are reflected from the ocean’s surface. After Goldeneye collects the reflected GPS signals, the signals will be processed to determine the oceans surface conditions where the reflected GPS signals originated.
More information
Last Modified: Tuesday, 07-Aug-2007 07:12:48 CDT