Time Synchronization Using Dedicated Pulse Line and Time Counting

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Solution Overview

Problem

Existing time synchronization techniques are limited by propagation delay and jitter in data communication lines, leading to inaccurate synchronization between master and slave devices.

Innovation Solution

A time synchronization system where a master device transmits a fixed-period signal through a dedicated signal line and provides start time and transmission period information through a data communication line, allowing slave devices to calculate and correct their time based on the number of signal receptions, independent of data communication line delays.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If time information is transmitted through a data communication line alongside the time cycle pulse signal, then the slave device can receive both synchronization signals, but the time information is affected by jitter and propagation delay causing synchronization accuracy to deteriorate

Engineering Contradiction:

Improvesynchronization accuracyVSAvoidtime information delay

Core Design Contradiction:

Measurement precisionVSLoss of information

Solution Approach 1:

The patent separates the time cycle pulse signal transmission from the time information transmission. The time cycle pulse signal is transmitted through a dedicated signal line, while time information is transmitted through a data communication line. This segmentation allows each channel to be optimized independently, preventing the time information from being affected by the pulse signal's propagation delay and jitter.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent introduces a counter as an intermediary element that counts the number of received time cycle pulse signals. Instead of directly using time information transmitted through the data communication line (which suffers from delay), the slave device uses the counter value combined with the known transmission period to calculate the master device's time, thereby mediating around the propagation delay issue.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Measurement precision

If the transmission period of the time cycle pulse signal is shortened to improve synchronization accuracy, then the synchronization precision increases, but the maximum time lag caused by propagation delay and jitter becomes more significant relative to the period

Engineering Contradiction:

Improvesynchronization accuracyVSAvoidpropagation delay time

Core Design Contradiction:

Measurement precisionVSLoss of time

Solution Approach 1:

The patent replaces the traditional method of using directly transmitted time information (analogous to a mechanical clock signal) with a calculation-based approach. The slave device calculates the master device's time using the formula: master_time = slave_time + (counter_value × transmission_period). This substitution allows the system to achieve high synchronization accuracy even with short transmission periods because the calculation compensates for propagation delay rather than relying on perfectly synchronized signal arrival.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Reliability

If time information is transmitted every time a time cycle pulse signal is sent, then the slave device can continuously synchronize, but the bandwidth consumption of the data communication line increases

Engineering Contradiction:

Improvesynchronization reliabilityVSAvoidbandwidth consumption

Core Design Contradiction:

ReliabilityVSLoss of energy

Solution Approach 1:

The patent implements periodic transmission of time information at predetermined intervals rather than transmitting time information with every time cycle pulse signal. The slave device maintains synchronization by counting the number of received pulse signals during these intervals and calculating the master device's time based on the counter value and the known transmission period. This periodic approach reduces data communication bandwidth consumption while maintaining synchronization reliability.

Inventive Principle:

Principle #19Periodic action

Data Source

PatentUS11277253B2Time synchronization system, master device, slave device, and program

Publication Date: 2022.03.15 MITSUBISHI ELECTRIC CORP

AI summary

A time synchronization system includes a master and slave devices connected to each other via a data bus and a signal line dedicated to transmission of a fixed-period signal. The master device transmits the fixed-period signal through the signal line regularly at a transmission period, and transmits start time information indicating a transmission start time at which transmission of the fixed-period signal is started and transmission period information indicating the transmission period for the fixed-period signal through the data bus. The slave device counts a number of times the fixed-period signal is received and calculates, as a current time in the master device, a transmission time at which the master device transmits the fixed-period signal based on the number of times the fixed-period signal is received. The slave device corrects the time to the calculated current time in the master device.