CAN Node Signal Detection for Failure Diagnosis Without Disconnection
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Solution Overview
Problem
Existing communication failure detection devices for two-wire CAN communication systems require disconnection of CAN communication lines for diagnosis, leading to complex configurations and inability to perform failure diagnosis in ordinary circuit states.
Innovation Solution
A communication failure detection device with two signal detection circuits at each node that outputs predetermined patterns onto the communication lines to identify failure types based on signal combinations, allowing for simple configuration and identification of failures without disconnection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the CAN communication lines are disconnected from the joint circuit and connected with the test circuit for abnormality diagnosis, then the abnormality diagnosis can be performed, but the circuit configuration becomes complicated and the diagnosis cannot be performed in ordinary circuit state
Solution Approach 1:
The patent combines the test circuit functionality with the ordinary CAN communication circuit by integrating the signal detection circuits into the node structures that are already present in the CAN network. The communication failure detection device uses the existing communication lines without requiring disconnection or separate test connections, thereby merging the diagnostic function with the operational circuit.
Solution Approach 2:
The signal detection circuits are designed to perform multiple functions: they detect communication failures during normal operation and also identify specific failure types. The same circuit structure serves both ordinary CAN communication and failure detection purposes, eliminating the need for separate test circuits or disconnection mechanisms.
2Reliability
If disconnection units (relays) are used to disconnect CAN communication lines from the joint circuit for test, then abnormality diagnosis can be performed individually on each line, but the circuit configuration is complicated
Solution Approach 1:
The patent extracts the essential diagnostic function from the complex disconnection mechanism. Instead of using relays to physically disconnect lines, the signal detection circuits detect failure patterns by monitoring signal characteristics during normal communication, extracting diagnostic information without requiring physical disconnection or additional switching components.
Solution Approach 2:
The CAN communication system performs self-diagnosis through the signal detection circuits that monitor communication signals during normal operation. The system identifies failure types by analyzing signal patterns generated during ordinary communication, eliminating the need for external test equipment or complex disconnection mechanisms.
3Device complexity
If two signal detection circuits are used to detect signals on communication lines with predetermined patterns, then failure identification can be performed with simple configuration, but timing differences may cause identification errors
Solution Approach 1:
The signal detection circuits use periodic communication patterns (dominant and recessive states alternating in a predetermined sequence) to detect failures. By repeating the communication cycle multiple times and comparing results, the system absorbs timing differences and reduces identification errors, maintaining high accuracy despite the simple two-circuit configuration.
Solution Approach 2:
The signal detection circuits incorporate feedback mechanisms where the detected signal patterns are compared against expected patterns. When timing differences cause anomalies, the feedback system adjusts the comparison timing or repeats the detection cycle, ensuring accurate failure identification while maintaining the simplicity of the two-circuit design.
Data Source
AI summary
There is provided a communication failure detection device configured to detect a communication failure of a two-wire CAN communication device that makes communication between nodes according to a CAN protocol. Each of the nodes is provided with two signal detection circuits configured to detect signals on the two communication lines. Each node makes communication for failure dentification to output signals of predetermined patterns onto the two communication lines when an execution condition is satisfied in response to the occurrence of a protocol error of CAN communication. Each node then performs failure identification to identify the type of a failure based on a combination of the signals respectively detected by the two signal detection circuits during the communication for failure identification.