GPS Timestamp Circuit for Multi-Sensor Clock Synchronization
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Solution Overview
Problem
Autonomous driving vehicles face challenges in generating accurate and synchronized timestamps for sensor inputs due to the variability and cost of high precision crystal oscillators, leading to imprecise timekeeping and synchronization across different sensors and devices.
Innovation Solution
A GPS-based high precision timestamp generation circuit that synchronizes local oscillators with GPS pulse signals, using multiple granularity counters to adjust and synchronize time signals, ensuring precise timestamp generation and synchronization across sensors and devices.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If high precision crystal oscillators are used to generate accurate timestamps, then timekeeping accuracy is improved, but cost increases and availability decreases
Solution Approach 1:
The patent uses GPS satellite signals as an intermediary time reference source. Instead of relying on expensive local crystal oscillators, the system receives highly accurate time signals from GPS satellites and uses them to synchronize local timing circuits, achieving high precision timekeeping through an external reference rather than expensive local components
Solution Approach 2:
The patent replaces the mechanical crystal oscillator system with an electronic GPS-based timing system. By substituting the physical crystal resonance mechanism with electronic signal processing of GPS time signals, the system achieves comparable or superior accuracy without the cost and availability constraints of high-precision crystal oscillators
2Adaptability or versatility
If multiple clock sources from sensors and devices are used for time generation, then time availability is improved, but synchronization precision deteriorates due to confusion and imprecision
Solution Approach 1:
The patent merges multiple sensor time sources by synchronizing them to a common GPS-based time reference. All sensors receive timestamps derived from the same GPS time signal, eliminating the confusion and imprecision that arise from using independent clock sources while maintaining the availability of multiple sensor inputs
Solution Approach 2:
The patent creates homogeneous time reference across all sensors by using a unified GPS-based timing system. All time measurements and timestamps are derived from the same GPS time signal, ensuring consistent time bases across diverse sensors and devices, which eliminates synchronization issues caused by heterogeneous clock sources
Data Source
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AI summary
In one embodiment, a system receives, at a sensor unit, a global positioning system (GPS) pulse signal from a GPS sensor of the autonomous driving vehicle (ADV), where the GPS pulse signal is a RF signal transmitted by a satellite to the GPS sensor, where the sensor unit is coupled to a number of sensors mounted on the ADV to perceive a driving environment surrounding the ADV and to plan a path to autonomously drive the ADV. The system receives a first local oscillator signal from a local oscillator. The system synchronizes the first local oscillator signal to the GPS pulse signal in real-time, including modifying the first local oscillator signal based on the GPS pulse signal. The system generates a second oscillator signal based on the synchronized first local oscillator signal, where the second oscillator signal is used to provide a time to at least one of the sensors.