CAN Bus Ground Fault Detection via Logic Signal Sampling
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Solution Overview
Problem
In long distance multi-node CAN bus industrial control, ground faults often occur, leading to subsequent misoperations of onsite control devices, and existing solutions struggle with reliable and efficient detection due to complex interference and electronic characteristics of CAN buses.
Innovation Solution
A fault detection system comprising a first sampling module, a second sampling module, a detection module, and a fault judgment module, which acquires sent and received logic signals, samples voltage between the ground wire and CAN bus, detects mismatches with reference voltages, and converts results into a ground fault index to reliably judge faults.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If ground fault detection is performed on CAN bus in industrial control, then fault detection capability is improved, but detection reliability deteriorates due to complex interference and electronic characteristics
Solution Approach 1:
The patent applies preliminary action by performing sampling of the sent logic signal and received logic signal before the actual ground fault detection. The first sampling module captures the logic signals at a specific timing (when both signals indicate dominant state) to establish a baseline reference, which is then used by the detection module to compare against subsequent measurements. This preliminary sampling enables more reliable fault detection by providing a reference state before interference affects the measurement.
Solution Approach 2:
The patent employs parameter changes by utilizing the impedance state transition of the CAN transceiver. When both sent and received logic signals indicate a dominant state, the CAN transceiver is in a low impedance state. The detection system changes the measurement parameter by sampling during this specific impedance state, which eliminates the influence of high impedance state (recessive state) on ground fault detection. This parameter change enables reliable detection despite complex interference.
2Measurement precision
If sampling is performed when CAN bus is in recessive state, then sampling coverage is improved, but detection accuracy deteriorates due to high impedance state influence
Solution Approach 1:
The patent changes the operational parameter by selecting a specific timing window when both sent and received logic signals indicate dominant state. During this window, the CAN transceiver operates in low impedance state, which is fundamentally different from the high impedance state in recessive state. This parameter change ensures that sampling occurs under optimal electrical conditions, achieving both high measurement precision and efficient detection without the interference problems of recessive state sampling.
3Reliability
If detection is performed continuously, then detection coverage is improved, but system complexity increases
Solution Approach 1:
The patent implements periodic action by performing ground fault detection at specific intervals rather than continuously. The detection is triggered periodically when both sent and received logic signals indicate dominant state, creating a regular sampling rhythm. This periodic detection approach maintains comprehensive fault coverage while significantly reducing system complexity compared to continuous monitoring, as the detection module only activates during these predetermined sampling windows.
Data Source
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AI summary
Embodiments of the present application provide a fault detection system, a fault detection method and a CAN bus device. The fault detection system comprises: a first sampling module, which is connected between a CAN transceiver and a CAN controller, and is used for acquiring a sent logic signal and a received logic signal of the CAN transceiver, and, when the sent logic signal and the received logic signal both indicate that the CAN bus is in a dominant state, outputs a first enabling signal indicating a sampling result; a second sampling module, one end of the second sampling module being connected between a ground wire and the CAN bus, and the other end outputting a sampled voltage; a detection module, which is connected to the first sampling module and the second sampling module, and is used for detecting whether the sampled voltage matches a first reference voltage of the CAN bus in a recessive state in response to the first enabling signal; a fault judgment module, which is connected to the detection module, and is used for converting a detection result into a ground fault index of the CAN bus when the sampled voltage does not match the first reference voltage.