Browsing by Author "Petovello, Mark G."

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    Assessment of Different Sensor Configurations for Collaborative Driving in Urban Environments
    (Hindawi, 2013-01-07) Petovello, Mark G.; Basnayake, Chaminda; O'Keefe, Kyle; Wei, Phil
    Vehicle-to-vehicle relative navigation of a network of vehicles travelling in an urban canyon is assessed using least-squares and Kalman filtering covariance simulation techniques. Between-vehicle differential GPS is compared with differential GPS augmented with between-vehicle ultrawideband range and bearing measurements. The three measurement types are combined using both least-squares and Kalman filtering to estimate the horizontal positions of a network of vehicles travelling in the same direction on a road in a simulated urban canyon. The number of vehicles participating in the network is varied between two and nine while the severity of the urban canyon was varied from 15-to 65-degree elevation mask angles. The effect of each vehicle’s azimuth being known a priori, or unknown is assessed. The resulting relative positions in the network of vehicles are then analysed in terms of horizontal accuracy and statistical reliability of the solution. The addition of both range and bearing measurements provides protection levels on the order of 2 m at almost all times where DGPS alone only rarely has observation redundancy and often exhibits estimated accuracies worse than 200 m. Reliability is further improved when the vehicle azimuth is assumed to be known a priori.
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    Combined Acquisition and Tracking Methods for GPS L1 C/A and L1C Signals
    (2010-12-01) Macchi-Gernot, Florence; Petovello, Mark G.; Lachapelle, Gérard
    As part of the GPS modernization, the GPS L1 C/A signal will be augmented by the L1C signal. With this improvement, for the first time, several signals from the same constellation will be available at the same frequency. In this paper, an acquisition method is implemented to combine the GPS L1 C/A and L1C signals before correlation. The combined acquisition succeeds to acquire the signal at low C/N0, whereas the acquisition of the L1C data channel alone fails. Concerning the tracking, a method to combine the GPS L1 C/A and L1C signals before the discriminator is developed. This method shows better performance than the traditional tracking using only one signal. Finally, a Kalman filter to combine the signals in the tracking is developed. It shows better performance than the traditional tracking in all conditions. Since the L1C signal will not be broadcast before 2013, these methods are tested using a software signal simulator.
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    GPS/Reduced IMU with a Local Terrain Predictor in Land Vehicle Navigation
    (Hindawi Publishing Corporation, 2008) Sun, Debo; Petovello, Mark G.; Cannon, M. Elizabeth
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    GPS/Reduced IMU with a Local Terrain Predictor in Land Vehicle Navigation
    (2008-11-03) Sun, Debo; Petovello, Mark G.; Cannon, M. Elizabeth
    In order to reduce the cost and volume of land vehicle navigation (LVN) systems, a “reduced” inertial measurement unit (IMU) consisting of only one vertical gyro and two or three accelerometers is generally used and is often integrated with other sensors. Since there are no horizontal gyros in a reduced IMU, the pitch and roll cannot be calculated or observed directly from the inertial data, and the navigation performance is thus affected by local terrain variations. In this work, a reduced IMU is integrated with global positioning system (GPS) data and a novel local terrain predictor (LTP) algorithm. The latter is used primarily to help estimate the pitch and roll of the reduced IMU system and thus to improve the navigation performance. In this paper, two reduced IMU configurations and two grades of IMUs are investigated using field data. Test results show that the LTP is valid. Specifically, inclusion of the LTP provides more than an 80% horizontal velocity improvement relative to the case when the LTP is not used in a GPS/reduced IMU configuration.
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    Real-time integration of a tactical-grade IMU and GPS for high-accuracy positioning and navigation
    (2003) Petovello, Mark G.; Lachapelle, Gérard
    The integration of the Global Positioning System (GPS) and Inertial Navigation Systems (INSs) is often used to provide accurate positioning and navigation information. For applications requiring the highest accuracy, the quality of the inertial sensors required is usually assumed to be very high. This dissertation investigates the integration of GPS with a tactical-grade Inertial Measurement Unit (IMU) for centimetre-level navigation in real-time. Different GPS/INS integration strategies are investigated to assess their relative performance in terms of position and velocity accuracy during partial and complete data outages, carrier phase ambiguity resolution after such data outages, and the overall statistical reliability of the system. In terms of statistical reliability, the traditional equations used in dynamic systems are redeveloped in light of some practical considerations, including centralized and decentralized filter architectures, and sequential versus simultaneous measurement updating. Results show that the integrated solution outperforms the GPS-only approach in all areas. The difference between loose and tight integration strategies was most significant for ambiguity resolution and system reliability. The integrated solution is capable of providing decimetre-level accuracy or better for durations of about five or ten seconds when a complete or partial GPS outage is simulated. This level of accuracy, extended over longer time intervals, is shown to reduce the time required to resolve the 11 ambiguities by an average of about 50% or more for data outages as long as 30 seconds when using a tight integration strategy. More importantly, the reliability of the ambiguity resolution process is improved with the integrated system. Statistical reliability parameters are also dramatically better when using the integrated system with the ability of detecting a single-cycle cycle slip being better and more consistent, relative to GPS-only. The effect of undetected blunders on the final system is also significantly reduced. Two real-time tests are analyzed and results show that directly resolving the 11 ambiguities is still unreliable in suburban environments, even with the integrated system. However, using the widelane phase observable, sub-decimetre navigation is demonstrated in suburban and pseudo-urban environments, despite the relatively adverse operational conditions encountered.