Multi-interface GPS Time Synchronizer for ADAS Drift Reduction
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Solution Overview
Problem
Existing systems face challenges in establishing a unified time base for ADAS/HFL applications across multiple interfaces, leading to difficulties in correlating data from different sensors due to varying GPS antennas causing drift and jitter, and the lack of compatibility between different communication protocols, which affects data relevance and accuracy.
Innovation Solution
A time synchronizer that receives UTC time in serial+PPS format from a GPS device and outputs timestamp data in multiple formats, including CAN, Ethernet, and gPTP, using a Linux real-time controller and FPGA to create a unified UTC time base for various devices, thereby synchronizing multiple data sources and eliminating the need for multiple GPS antennas.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If multiple GPS antennas are used to provide time synchronization to different sensors, then each sensor can have its own time source, but drift and jitter occur between different antennas causing time base inaccuracy
Solution Approach 1:
The patent consolidates multiple GPS antenna inputs into a single unified time base by using one GPS receiver to generate a common timestamp that is then distributed to all sensors through multiple output interfaces (CAN, Ethernet, gPTP, serial+PPS). This merging approach eliminates drift and jitter between antennas while maintaining reliable time synchronization across all devices.
Solution Approach 2:
The time synchronizer device performs multiple functions: it receives GPS time signals, generates unified timestamps, and distributes them through multiple communication protocols (CAN, Ethernet, gPTP, serial+PPS) to different sensor types. This multi-functionality allows a single device to serve as the universal time source for diverse sensors without requiring separate GPS antennas for each.
2Adaptability or versatility
If multiple GPS receivers are used to supply time to multiple ECUs, then each ECU can have dedicated time input, but drift between receivers contributes to timestamp inaccuracy
Solution Approach 1:
The patent segments the time distribution function across multiple output interfaces (CAN, Ethernet, gPTP, serial+PPS) while maintaining a single unified time source. Each interface is optimized for different ECU types and communication protocols, providing adaptability without requiring multiple GPS receivers. The segmentation occurs at the output distribution stage, not at the time source stage.
Solution Approach 2:
The time synchronizer acts as an intermediary device between the single GPS receiver and multiple ECUs. It receives the GPS time signal, generates unified timestamps, and distributes them through appropriate communication protocols to different ECU types. This intermediary role eliminates drift between receivers while maintaining broad interface compatibility.
3Quantity of substance
If a single GPS antenna is used with a splitter to supply multiple devices, then the same signal is provided to all devices, but splitters introduce delays and attenuate signals limiting cabling and accuracy
Solution Approach 1:
The patent replaces the mechanical signal splitting approach with an electronic time generation and distribution system. Instead of using a physical splitter that divides the GPS signal (causing attenuation and delays), the system uses a single GPS receiver to generate a unified timestamp that is then electronically distributed to multiple devices through different communication protocols (CAN, Ethernet, gPTP, serial+PPS). This substitution eliminates signal degradation while providing multiple time outputs.
4Adaptability or versatility
If different communication protocols are used for different sensors, then each sensor can use its native protocol, but correlating data from sensors with different protocols becomes difficult
Solution Approach 1:
The time synchronizer provides universal time synchronization by supporting multiple communication protocols (CAN, Ethernet, gPTP, serial+PPS) simultaneously. Each sensor receives timestamps in its native protocol format from the same unified time source, ensuring both protocol adaptability and data correlation accuracy. The multi-functionality of the time synchronizer allows it to serve diverse sensors without protocol conversion issues.
Data Source
AI summary
A time synchronizer receives UTC (Coordinated Universal Time) time in serial+PPS (Pulse Per Second) format from a GPS (Global Positioning System) device and outputs timestamp data in multiple formats, including: CAN (Controller Area Network), Ethernet, gPTP (generic Precision Time Protocol), and serial+PPS. Multiple data sources receive timestamp data in the multiple formats and each provide data in a unified UTC time base to a sensor-fusion device. The unified UTC time base is based on the timestamp data in the multiple formats output by the time synchronizer. The time synchronizer may perform edge detection for a first transition of an internal clock signal following a transition of the PPS signal received from the GPS device. The internal clock signal may be asynchronous with the PPS signal received from the GPS device. The internal clock signal may have a frequency of 40 MHz.