CAN Bus Ground Fault Detection via Voltage Analysis

Solution Overview

Problem

Ground faults in the communications network of electronic control units (ECUs) can be difficult to detect, often leading to unnecessary ECU replacements and repeated repair visits, as they manifest as ECU faults rather than communication line faults.

Innovation Solution

A method involving the measurement of voltage points on a CAN bus using A-to-D converters to differentiate between recessive and dominant bits, calculate average voltages, and determine the presence of ground faults by comparing these values against predefined thresholds, allowing for the detection and isolation of floating ground and ground offset faults.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If service stations replace ECUs to solve performance issues, then ECU faults may be resolved, but unnecessary replacements occur and troubleshooting time increases when the actual problem is a ground fault on the communication network

Engineering Contradiction:

ImproveECU functionalityVSAvoidtroubleshooting time

Core Design Contradiction:

ReliabilityVSLoss of time

Solution Approach 1:

The system performs preliminary ground fault detection by monitoring CAN bus voltage levels before ECU failure occurs. The controller continuously measures voltage points on the communication network and compares them against threshold values to identify ground faults early, preventing unnecessary ECU replacements and reducing troubleshooting time

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent introduces an intermediary detection mechanism that monitors the communication network between ECUs and the ground. By measuring voltage levels on the CAN bus and analyzing differential signals, the system detects ground faults in the communication line rather than directly in the ECU, serving as an intermediary diagnostic layer

Inventive Principle:

Principle #24Intermediary (Mediator)

2Reliability

If service stations replace ECUs to solve performance issues, then ECU faults may be resolved, but unnecessary ECU replacements occur increasing repair costs

Engineering Contradiction:

ImproveECU functionalityVSAvoidECU replacement

Core Design Contradiction:

ReliabilityVSLoss of substance

Solution Approach 1:

The system performs preliminary ground fault detection by monitoring CAN bus voltage levels before ECU failure occurs. The controller continuously measures voltage points on the communication network and compares them against threshold values to identify ground faults early, preventing unnecessary ECU replacements and reducing troubleshooting time

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent introduces an intermediary detection mechanism that monitors the communication network between ECUs and the ground. By measuring voltage levels on the CAN bus and analyzing differential signals, the system detects ground faults in the communication line rather than directly in the ECU, serving as an intermediary diagnostic layer

Inventive Principle:

Principle #24Intermediary (Mediator)

3Loss of time

If ground faults are not detected early, then troubleshooting continues unnecessarily, but ECU failure may occur requiring more extensive repairs

Engineering Contradiction:

Improvetroubleshooting timeVSAvoidECU functionality

Core Design Contradiction:

Loss of timeVSReliability

Solution Approach 1:

The system performs preliminary ground fault detection by monitoring CAN bus voltage levels before ECU failure occurs. The controller continuously measures voltage points on the communication network and compares them against threshold values to identify ground faults early, preventing unnecessary ECU replacements and reducing troubleshooting time

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The system implements continuous feedback monitoring of CAN bus voltage levels. The controller measures voltage points, compares them against predefined thresholds, and provides diagnostic feedback about ground fault conditions. This feedback mechanism enables early detection and prevents ECU failure by alerting technicians to communication network issues before they cause permanent damage

Inventive Principle:

Principle #23Feedback

Data Source

PatentUS9989575B2Detection of ECU ground fault with can bus voltage measurements

Publication Date: 2018.06.05 GM GLOBAL TECHNOLOGY OPERATIONS LLC

AI summary

A method is disclosed for detecting ground faults in a communications system. The method includes measuring a predetermined number of voltage points; determining if the measured voltage points represent recessive or dominant bits; identifying which of the predetermined number of voltage points represent inter-frame bits and which represent frame data bits based on whether the measured voltage points are recessive or dominant; calculating a maximum average voltage for the inter-frame bits; calculating an average frame voltage for all dominant bits within a frame; determining a high average dominant voltage count based on a number of frames for which the average frame voltage is greater than a high voltage threshold; and determining if a ground fault exists based on the average frame voltage and the high average dominant voltage count.