Master of Science (MS), Ohio University, 2020, Electrical Engineering (Engineering and Technology)

With a growing demand for large unmanned aircraft system operations in the national airspace system, a method to safely and automatically land unmanned aircraft at a wide range of airports with varying levels of equipage is still needed. Currently no navigation system is capable of a fully coupled precision approach and landing without the use of ground based navigational aids. To enable widescale adoption and usage of unmanned aircraft systems, an aircraft based augmentation system that provides precision approach and landing service without sacrificing safety is required to land the aircraft at all runways. This thesis proposes an aircraft based GPS augmentation system using an on-board downward facing radar altimeter for precision approach and landing of unmanned aircraft systems. The proposed architecture is initially evaluated using a simulation environment designed to test multiple different GNSS, radar altimeter, and terrain elevation database configurations. Following the offline simulation, a flight test analysis is completed testing the proposed architecture using pre-recorded flight test data at the Ohio University Airport (OH) and Reno-Tahoe International Airport (NV). Furthermore, this thesis provides a sensitivity study on the systematic errors in the augmentation system to better characterize and account for the inherent errors of the architecture's subsystems. This thesis then discusses modifications to the previously developed terrain database spot algorithm to better account for the characteristics of the selected radar altimeter. Finally, an approach for future certification is proposed followed by recommendations for further research on the topic.

Committee: Maarten Uijt de Haag Ph.D. (Advisor); Frank van Graas Ph.D. (Committee Member); Sabrina Ugazio Ph.D. (Committee Member); Justin Frantz Ph.D. (Committee Member) Subjects: Electrical Engineering; Engineering

Master of Science (MS), Ohio University, 1996, Electrical Engineering & Computer Science (Engineering and Technology)

Investigating the effect of the DGNSS SCAT-I data link on VOR signal reception

Committee: Trent Skidmore (Advisor) Subjects:

Doctor of Philosophy (PhD), Ohio University, 2018, Mechanical and Systems Engineering (Engineering and Technology)

Cable-Suspended Parallel Robots (CSPRs) are a class of devices that use three or more winch-activated cables to manipulate an end-effector within a workspace. A distinct advantage of CSPRs is that large payloads can be manipulated over distances that encompass a very large workspace. The application motivating this research (among other commercial applications) is harvesting algae which is commonly used in bioplastics, nutraceuticals, and biofuels. Harvesting algae from one to four acre circulating pond systems is done at significant cost, because it involves pumping the pond water to a centrifuge/filtration system to collect concentrated algae, before transporting it to a central processing location. Thus, an outcome of this research is to collect data using a prototype CSPR system with and without the assistance of GPS corrections to assess the next steps in developing this technology and support cost reductions in commercial algae harvesting. The research presented herein focuses on the requisite precision and accuracy required by the end-effector for this application. To meet these requirements, a unique control scheme incorporating Real Time Kinematics (RTK) and a Global Positioning System (GPS) was developed to significantly improve CSPR positioning. A 1/500th scale prototype CSPR system using RTK and GPS was developed for this research. The system consists of four towers equipped with a central controller and distributed motors and drivers connected via EtherCAT, a high-speed network. A series of tests were performed to demonstrate feasibility and performance of this unique control concept that uses RTK-GPS positional data to correct and improve end-effector positioning. The performance of the CSPR (without RTK-GPS) was first characterized in a well-controlled, indoor environment using a Coordinate Measuring Machine (CMM) with a single point accuracy of 0.001 inch. Subsequent tests were performed outdoors, with and without RTK-GPS activation. For all outdoor (open full item for complete abstract)

Committee: Robert Williams (Advisor); David Bayless (Committee Member); Frank Kraft (Committee Member); Natalie Kruse Daniels (Committee Member); Morgan Vis-Chiasson (Committee Member) Subjects: Alternative Energy; Engineering; Mechanical Engineering; Robotics; Robots

Doctor of Philosophy (PhD), Ohio University, 1999, Electrical Engineering & Computer Science (Engineering and Technology)

This dissertation discusses integration architectures using digital terrain elevation data (DTED) with an inertial navigation system (INS), a global positioning system (GPS) and a radar altimeter. Two integration architectures are considered: DTED with INS, GPS and radar altimeter for aircraft vertical accuracy improvement during the final approach; and DTED with kinematic GPS (KGPS) and a radar altimeter for enhanced aircraft flight safety. Error models were generated and verified with flight-test data. High-fidelity simulation was used to investigate vertical accuracy improvement. Improvement was found to be 1.2 meters, a reduction of 28.6% in the vertical error. Flight testing was performed to assess the feasibility of enhanced flight safety. Reasons for enhanced flight safety are twofold: 1) the ad-hoc integration of terrain elevation data into the cockpit conceivably may create scenarios which lead to accidents because the cockpit display is quite realistic, and 2) reduction of controlled flight into terrain (CFIT). The radar altimeter is the principle sensor used to compare navigation outputs with publicly available DTED. Results show that it is feasible to define an operationally useful probability of agreement,- P a, among KGPS, DTED and the radar altimeter, by using a mean-square-difference test statistic. This probability of agreement can be used to warn the pilot if the terrain depiction does not agree with the navigation solution provided by KGPS, thus enhancing flight safety.

Committee: Frank van Graas (Advisor) Subjects:

Master of Science (MS), Ohio University, 1994, Electrical Engineering & Computer Science (Engineering and Technology)

A shipboard global positioning system carrier phase interferometric aircraft flight reference system

Committee: Frank van Graas (Advisor) Subjects:

Master of Science (MS), Ohio University, 1996, Electrical Engineering & Computer Science (Engineering and Technology)

DGPS/ILS integration for an automatic landing system using Kalman Filtering

Committee: Michael Braasch (Advisor) Subjects:

Master of Science (MS), Ohio University, 1998, Electrical Engineering & Computer Science (Engineering and Technology)

Integration of differential global positioning system and an inertial navigation system for aircraft surface movement guidance

Committee: Frank van Graas (Advisor) Subjects:

Master of Science (MS), Ohio University, 1998, Electrical Engineering & Computer Science (Engineering and Technology)

An inertial measurement unit interface and processing system synchronized to global positioning system time

Committee: Frank van Graas (Advisor) Subjects:

Doctor of Philosophy (PhD), Ohio University, 1998, Electrical Engineering & Computer Science (Engineering and Technology)

The Local Area Augmentation System (LAAS) is being developed to support precision approach and landing operations in and about the local area surrounding an airport. The LAAS Program is currently under development by the Federal Aviation Administration (FAA) with Minimum Aviation System Performance Standards for the LAAS being developed by RTCA, Incorporated. The LAAS uses differential Global Positioning System (DGPS) and includes one or more airport pseudolites (APL) to increase the availability for certain installations. This dissertation addresses the addition of a differentially corrected, ranging APL into a LAAS. Prior to this work, no ranging APL has been integrated into a prototype LAAS and demonstrated in a real-time flight environment showing that an increase in LAAS availability is feasible. The APL requirements resulted in a prototype APL transmitting and receiving subsystem with a coarse-acquisition (C/A) code format that could be operated at any frequency within the L1 ± 10.0 MHz band. To investigate the major APL error the developmental approach was performed in two phases. Phase I implemented an APL operating at a center frequency off-L1 and concentrated on multipath limiting. The Phase II on-L1 APL architecture implemented a unique pulsing, automatic gain control (AGC) and GPS Blanker technique in the common reception path to maximize APL signal tracking and minimize electromagnetic interference to DGPS. To minimize ground multipath for the APL geometry, which is more severe than for GPS, a multipath limiting antenna (MLA) was designed, fabricated, and tested within a 4-month period. The implementation of this MLA concept was a first for APL applications and also contributed to the successful multipath limiting of ground multipath at the DGPS LAAS Ground Station. This effort successfully demonstrated that ground multipath can be limited (with low variance and no long-term bias) for the APL geometry and that suitable precision approach performance can (open full item for complete abstract)

Committee: Frank van Graas (Advisor) Subjects:

Master of Science (MS), Ohio University, 2003, Electrical Engineering & Computer Science (Engineering and Technology)

Integrated Global Positioning System and inertial navigation system integrity monitor performance.

Committee: Frank van Graas (Advisor) Subjects:

Master of Science (MS), Ohio University, 2002, Electrical Engineering & Computer Science (Engineering and Technology)

Traditionally, Differential Global Positioning System (DGPS) provides corrections to enable high accuracy position solution to mobile users. The Local Area Augmentation System (LAAS) employs DGPS to obtain precise positioning of aircraft for various levels of landing categories in the airport vicinity. Unrelated to LAAS, some remote-positioning systems transmit measurements from a mobile user to another location to determine the state of the mobile user remotely. The Bi-directional DGPS proposed here would enable both of these features simultaneously within the same architecture. The purpose of this research was to demonstrate a Bi-directional DGPS, within a prototype LAAS, that integrates both DGPS and remote-positioning capabilities. The Bi-directional DGPS was successfully demonstrated at the Ohio University Airport using both a van and an aircraft as a mobile user with a fixed supporting ground-based station. This thesis presents the architecture, results and conclusions of these demonstrations.

Committee: Chris Bartone (Advisor) Subjects:

Master of Science (MS), Ohio University, 2001, Electrical Engineering & Computer Science (Engineering and Technology)

Global Positioning System based runway instrumentation system

Committee: Frank van Grass (Advisor) Subjects:

Doctor of Philosophy (PhD), Ohio University, 1994, Electrical Engineering & Computer Science (Engineering and Technology)

An Interferometric Global Positioning System Flight Reference System (IGPS FRS) is implemented and flight tested on a transport category aircraft. This dissertation discusses the IGPS FRS theory and principles of operation, its architecture and integration with the aircraft, and the initial static calibration and flight-test performance results. The validity of the results is established by referencing them to a known ground test point and/or a laser tracking system. The principles underlying the operation of the IGPS FRS are similar to those used for kinematic surveying, and are also referred to as differential carrier-phase tracking with integer ambiguities resolved. Flight Reference System objectives include: 0.1 m accuracy rms (each axis); one or more updates per second; UTC (Universal Time, Coordinated) synchronization better than 0.1 ms; real-time, all-weather operation; and, repeatable flight paths. The latter requirement calls for full integration with the aircraft flight control system and coupled flight.

Committee: Frank van Graas (Advisor) Subjects:

Master of Science (MS), Ohio University, 2001, Electrical Engineering & Computer Science (Engineering and Technology)

The next generation of advanced aircraft landing system will utilize the Global Positioning System (GPS). The availabilityof GPS is augmented by the use of pseudolites "pseudo satellites." Pseudolites transmit a GPS-like signal that can be used as a ranging source in place of or in addition to ranging sources from a satellite. The Local Area Augmentation System (LAAS) is being used to further augment GPS for precision approaches and landings by using a concept known as Differential GPS (DGPS). One major error source in DGPS is due to transmitted signal reflections (multipath) off nearby obstacles. Efficient antenna design can be used to mitigate multipath by severely attenuating signals from negative elevation angles. The research contained in this document was conducted in order to optimize the current wideband airport pseudolite (WBAPL) multipath limiting antenna (MLA) for pseudolite transmission in the LAAS. To that end, three phases of study were conducted. The first stage modeled the ground-to-air link between the WBAPL transmitting MLA and the reception antenna during approaches with an attempt to define optimal WBAPL antenna locations. The second stage was conducted to characterize the basic pattern requirements of the WBAPL transmitting MLA and sought to project a hypothetical coverage volume given a preliminary pseudolite antenna pattern. The third stage was performed to attain some level of validation for the new WBAPL MLA transmitting antenna pattern measured by an external contractor through the independent synthesis of a similar antenna radiation pattern.

Committee: Chris Bartone (Advisor) Subjects:

Master of Science (MS), Ohio University, 2000, Electrical Engineering & Computer Science (Engineering and Technology)

An investigation of integrated global positioning system and inertial navigation system fault detection

Committee: Michael Braasch (Advisor) Subjects:

Doctor of Philosophy (PhD), Ohio University, 1988, Electrical Engineering & Computer Science (Engineering and Technology)

This paper describes a new technique that hybridizes the NAVSTAR Global Positioning System (GPS) and the Long Range Navigation System,LORAN-C, based on a generic pseudorange processing technique. The concept, theoretical analysis, and justification of a hybrid GPS/LORAN-C system are presented, along with a scheme for meeting sole means of navigation requirements. Following the design and modeling phase, a prototype hybrid GPS/LORAN-C receiver was developed and implemented. The hybrid GPS/LORAN-C receiver concept was proven through an actual flight test, which was referenced to a Differential GPS truth trajectory. The hybrid system has the potential to meet all requirements for a next generation of sole means of air navigation for the conterminous United States.

Committee: Richard McFarland (Advisor) Subjects:

Master of Science (MS), Ohio University, 2004, Electrical Engineering & Computer Science (Engineering and Technology)

A secure data collection and distribution system has been created for Global Positioning System (GPS) research. Specifically, a program, RxData, has been created, using Borland C++, to produce a database from binary GPS data sent from the LAAS Ground Facility (LGF) data logger at the Ohio University airport. This data is sent through a one-way null modem cable which serves as a hardware firewall. In addition, several programs have been purchased, configured, and implemented to allow access to the binary data via a secure Internet connection. The secure connection has been established using 128-bit encryption between the FTP server, Serv-U FTP v5.0, and the FTP client, FTP Voyager v11.0, and all connections with the server are sent through a software firewall, Sygate Personal Firewall Pro v5.5, which protects the server and database from Internet related attacks.

Committee: Constantinos Vassiliadis (Advisor) Subjects:

Master of Science (MS), Ohio University, 2004, Electrical Engineering & Computer Science (Engineering and Technology)

Technology trends indicate a smaller, cheaper GPS receiver as time proceeds. The automobile industry has greatly benefited from these strides in navigation technology, however this industry is sensitive to the cosmetics of exposed antennas. This thesis introduces the concept of a multiple antenna GPS configuration to enhance performance in automobiles, where multiple antenna are “hidden” but have limited view of the upper hemi-sphere. Traditionally, placement of a GPS antenna is critical; the roof of the automobile is considered the most effective location to place an antenna, in terms of GPS signal reception. Today, manufacturers are keeping an eye on automobile aesthetics. Smaller antennas allow mounting inside an automobile's glass windshields, thus also making it discreet (“hidden” antennas). This also reduces the risk of damage through vandalism, bad weather or theft. The performance implications due to decreased sky coverage are reduced through the use of multiple antennas, which collectively make up for vehicle-induced blockage. For this demonstration, GPS measurements are combined from four antenna-receiver sets in an intelligent fashion to form a “Virtual Receiver”. This “Virtual Receiver” philosophy and the algorithm involved are discussed. This thesis also illustrates the improvement in satellite coverage and enhancement in positional accuracy obtained by this method over each individual antenna-receiver set. The combined antenna system performance is compared to an independent “truth” roof mounted antenna-receiver setup. The multiple-antenna receiver configuration tested acts as a test bed for more effective antenna placement in automobiles. The mask-angles of this “Virtual Receiver” are controlled, to simulate an urban canyon environment and a performance analysis was conducted.

Committee: Chris Bartone (Advisor) Subjects:

Doctor of Philosophy (PhD), Ohio University, 2003, Electrical Engineering & Computer Science (Engineering and Technology)

This dissertation documents the design, development, and field and flight testing of a WBAPL for integration into a prototype LAAS. One major area of risk in the LAAS CAT II/III program is the unresolved issue of sufficient system availability. One feasible, low-cost, means of augmenting the GPS constellation for LAAS to enhance availability is by the incorporation of APLs. Critical issues that seek consideration in APL design are a low-cost solution to the near-far problem, effective mitigation of APL multipath at the LGF reception sites, and a solution to the issue of measurement errors as a function of peak received signal power level. This dissertation details the development of a prototype WBAPL within the framework of LAAS requirements, with the intent of resolving the aforementioned issues. The architecture includes a simple and novel method to facilitate rapid direct-WB signal acquisition, and details a cost-effective resolution to the power-bias problem. Results from laboratory tests to verify and characterize the power-induced measurement errors are described in the dissertation. Independent solutions to the power-bias problem at the ground and airborne segments were incorporated into the prototype WBAPL architecture. The solution on the ground involves the employment of RF power-control techniques. With the aim of low-cost implementation, the solution adopted for the airborne segment relies on carrier-phase measurements as the aircraft approaches the WBAPL transmission antenna. A time-differenced carrier-phase positioning algorithm that does not require real-time resolution of the unknown carrier-phase integer ambiguities is adopted. This differential CP approach is launched from a carrier-smoothed code based solution that is maintained from the beginning of the approach until the phase handover-point. A modification to the WBAPL single difference geometry matrix is incorporated into the TDCP algorithm. The proposed architecture was successfully flight-te (open full item for complete abstract)

Committee: Chris Bartone (Advisor) Subjects:

Master of Sciences (Engineering), Case Western Reserve University, 2011, EECS - Electrical Engineering

This thesis describes a cost effective, accurate, and precise electronic navigation system which is suitable for outdoor commercial mobile robots. The hardware design of the system incorporates commercial off the shelf Global Positioning System receiver modules and support electronics. The software design of the system makes use of an open source positioning library to enable Real Time Kinematic satellite positioning. The designed navigation system has been integrated with a preexisting mobile robot platform, an autonomous robot lawn mower, which includes a set of reference sensors to provide accurate robot pose information. The reference platform is used to quantitatively evaluate the performance of the new cost effective system. A degradation factor of 1.7 in terms of positional accuracy is traded off in favor of achieving a cost savings factor of about thirty.

Committee: Roger Quinn PhD (Advisor); Roger Quinn PhD (Committee Chair); Marc Buchner PhD (Committee Member); Francis Merat PhD (Committee Member) Subjects: Computer Engineering; Electrical Engineering; Robotics; Robots