Autonomous Vehicle Clock Sync Using Verified GPS Time
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Solution Overview
Problem
Autonomous vehicles face challenges in verifying the accuracy of computed GPS time when GPS signals are unavailable, leading to clock drift, which can affect synchronization and accuracy in detection and tracking systems.
Innovation Solution
An autonomous vehicle system that compares a sensor-based position, determined independently from GPS data using sensors and a digital map, to a computed GPS position to verify the accuracy of GPS time, allowing for clock updates only when the positions match within a threshold distance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If GPS time is used to update the clock, then synchronization accuracy is improved, but reliability deteriorates when GPS signals are unavailable or spoofed
Solution Approach 1:
The system performs preliminary verification by comparing sensor-based position with GPS-based position before accepting GPS time for clock updates. This advance check prevents unreliable GPS data from corrupting the clock synchronization, thereby maintaining both accuracy and reliability.
Solution Approach 2:
The system implements a feedback mechanism where the computed position from sensors is continuously compared with GPS computed position. This feedback loop verifies GPS signal integrity before allowing clock updates, ensuring that only reliable GPS time data is used to maintain synchronization accuracy.
2Reliability
If sensor-based position computation is performed independently of GPS, then reliability is improved, but device complexity increases
Solution Approach 1:
The sensor system serves multiple functions: it provides both autonomous navigation capability and GPS signal verification. By using the same sensors for both purposes, the system achieves reliable position verification without proportionally increasing complexity, as the sensors already exist for primary navigation functions.
Data Source
AI summary
A method of updating a clock associated with an autonomous vehicle includes determining, at a processor, a sensor-based position of the autonomous vehicle. The sensor-based position is determined based on data from one or more sensors and based on a digital map accessible to the processor. The method also includes determining, at the processor, a global positioning system (GPS) computed position of the autonomous vehicle and a GPS time. The GPS computed position and the GPS time are determined based on a plurality of GPS signals received from GPS satellites. The method further includes comparing the sensor-based position to the GPS computed position to determine whether the sensor-based position is within a threshold distance from the GPS computed position. The method also includes updating the clock associated with the autonomous vehicle based on the GPS time in response to a determination that the sensor-based position is within the threshold distance from the GPS computed position.