Matching Items (2)
Description
Autonomous vehicle control systems utilize real-time kinematic Global Navigation Satellite Systems (GNSS) receivers to provide a position within two-centimeter of truth. GNSS receivers utilize the satellite signal time of arrival estimates to solve for position; and multipath corrupts the time of arrival estimates with a time-varying bias. Time of arrival estimates are based upon accurate direct sequence spread spectrum (DSSS) code and carrier phase tracking. Current multipath mitigating GNSS solutions include fixed radiation pattern antennas and windowed delay-lock loop code phase discriminators. A new multipath mitigating code tracking algorithm is introduced that utilizes a non-symmetric correlation kernel to reject multipath. Independent parameters provide a means to trade-off code tracking discriminant gain against multipath mitigation performance. The algorithm performance is characterized in terms of multipath phase error bias, phase error estimation variance, tracking range, tracking ambiguity and implementation complexity. The algorithm is suitable for modernized GNSS signals including Binary Phase Shift Keyed (BPSK) and a variety of Binary Offset Keyed (BOC) signals. The algorithm compensates for unbalanced code sequences to ensure a code tracking bias does not result from the use of asymmetric correlation kernels. The algorithm does not require explicit knowledge of the propagation channel model. Design recommendations for selecting the algorithm parameters to mitigate precorrelation filter distortion are also provided.
ContributorsMiller, Steven (Author) / Spanias, Andreas (Thesis advisor) / Tepedelenlioğlu, Cihan (Committee member) / Tsakalis, Konstantinos (Committee member) / Zhang, Junshan (Committee member) / Arizona State University (Publisher)
Created2013
Description
Real-Time Operating Systems are used in a variety of applications ranging from autonomous vehicles, flight controllers, and energy management systems to pacemakers, satellite tracking systems, amateur robotics and much more. It turns out that while general-purpose computers can perform tasks quite quickly, the execution time for various processes varies noticeably between different executions. Execution time variation poses a big challenge for many computer-controlled systems that operate in the real-world such as robots, autonomous vehicles, drones, traffic signals, etc. The execution time variation matters in these systems since they must interact in the real world and perform actions at the proper times, and executing these tasks at other times can have varied effects ranging from a minor inconvenience to catastrophic failure. Many of these real-time systems are comprised of single board computers, such as a pacemaker. One single-board computer that is popular among hobbyists due to its form factor, cost, and performance is the Raspberry Pi, which uses an ARM-based processor. In order to provide a Real-Time Operating System for this single board computer this paper presents Jobbed, a single-core Real-Time Operating System which uses a fixed priority preemptive scheduler, targeted at the Raspberry Pi 2B. In this paper, we present the algorithmic structure behind this system and compare it to the Raspbian Operating System in an array of performance and behavioral tests targeted towards proper Real-Time Operating Systems.
ContributorsCunningham, Christian (Author) / Shrivastava, Aviral (Thesis director) / Vrudhula, Sarma (Committee member) / Barrett, The Honors College (Contributor) / Department of Physics (Contributor) / School of Mathematical and Statistical Sciences (Contributor)
Created2022-05