Sensor Time Synchronization via Periodic Reset in Automotive ECU
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Solution Overview
Problem
Existing motor vehicle systems face challenges in accurately synchronizing the timing of events from various non-synchronous sensors, leading to potential errors that can impact the performance of driving assistance systems, particularly in self-driving vehicles.
Innovation Solution
A system comprising sensors with relative internal clocks and an electronic control unit with an absolute internal clock, which communicates via a communication network to reset all relative clocks periodically, allowing for the calculation of absolute sensor time by adjusting relative sensor time using a reset time, thereby reducing network load and synchronizing sensor data accurately.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If multiple time bases are used to date events from different sensors, then event dating capability is provided, but time synchronization accuracy deteriorates due to lack of synchronization between time bases
Solution Approach 1:
The patent introduces a master control unit with a master time base as an intermediary that coordinates all slave time bases in the sensor network. This master unit sends synchronization commands and receives time data from all sensors, acting as a central mediator that ensures consistent event dating across the entire system while maintaining high synchronization accuracy.
Solution Approach 2:
Instead of having each sensor maintain its own independent time base and try to synchronize with others, the patent inverts the approach by having all sensors synchronize to a single master time base. This reversal of the synchronization direction (from distributed to centralized) resolves the contradiction by providing both accurate event dating and reliable time synchronization.
2Reliability
If synchronization signals are transmitted over the communication network to synchronize sensors, then time synchronization is achieved, but network load increases
Solution Approach 1:
The master control unit transmits synchronization commands periodically at fixed time intervals rather than continuously or on-demand. This periodic approach ensures reliable time synchronization across all sensors while significantly reducing the overall network communication load compared to continuous synchronization methods.
Solution Approach 2:
Each slave time base in the sensor nodes is configured to automatically adjust its timing based on received synchronization commands from the master unit. This self-service mechanism allows sensors to synchronize autonomously without requiring complex coordination protocols, thereby reducing network communication overhead while maintaining reliable synchronization.
3Measurement precision
If absolute synchronization with decoding is implemented, then precise time alignment is achieved, but processing time increases
Solution Approach 1:
The system performs preliminary time alignment by having all slave time bases synchronize to the master time base before actual sensing and data collection begins. This pre-synchronization ensures that when events are detected, they are already time-aligned, eliminating the need for complex decoding and post-processing time alignment operations.
Solution Approach 2:
The patent extracts the time synchronization function from the complex absolute synchronization with decoding process and implements it as a separate, simpler periodic synchronization mechanism. By separating the synchronization function from the main data processing flow, the system achieves precise time alignment without the time overhead of complex decoding operations.
Data Source
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AI summary
Method for date-stamping an event detected in an automotive vehicle comprising a plurality of sensors each comprising a relative internal clock, and an electronic control unit comprising an absolute internal clock and configured to communicate with each of the sensors via a communication network, in which, at each period (ΔTz), the whole set of relative internal clocks of the sensors is reset to zero, via communication frames of the communication network; the absolute time of resetting to zero (Tz) of the absolute clock of the electronic control unit is stored at each reset to zero; an event is detected; at each detected event, a sensor relative time (Trel_c) is received originating from the sensor's relative clock associated with the detected event; and a sensor absolute time (Tabs_c) is calculated as a function of the sensor relative time (Trel_c) of the internal clock of a sensor associated with the detected event and of the time of resetting to zero (Tz) stored by a storage module in the electronic control unit at each reset to zero, defining a reference relative time (Trel).