Encoded Safety Diagnostics Using Hamming-Distance Codewords
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Solution Overview
Problem
Current functional safety systems face challenges in accurately detecting and responding to faults and timeouts in complex systems, particularly in environments prone to interference, where bit flips or software overwrites can occur due to bugs, memory issues, or malicious attacks, leading to potential unsafe operational states.
Innovation Solution
A method involving a safety module that stores and encodes state information as unique codewords with minimum hamming distances, allowing for the detection of mismatches and outputting safety messages based on matches or mismatches between stored and valid codewords, thereby triggering fault recovery processes and maintaining functional safety.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional functional safety systems are used without encoded diagnostics, then the system structure is simpler and easier to implement, but the system cannot reliably detect bit flips or software overwrites caused by interference, leading to potential unsafe operational states
Solution Approach 1:
The patent introduces an intermediary encoding layer (codewords with Hamming distance) between the functional safety system components and the diagnostic detection mechanism. This intermediary structure enables reliable detection of bit flips and software overwrites without requiring fundamental changes to the underlying safety system architecture, thus improving reliability while maintaining manageable complexity
Solution Approach 2:
The patent changes the parameter representation from simple binary states to encoded codewords with specific Hamming distances. By transforming the data representation parameters, the system gains the ability to detect and distinguish between functional states and fault states with higher reliability, while the encoding scheme itself manages the complexity through mathematical structure
2Measurement precision
If the system uses encoded diagnostics with Hamming distance, then the system can accurately differentiate between functional and fault states, but the communication overhead and processing time increase
Solution Approach 1:
The patent applies preliminary action by pre-defining valid codewords and their corresponding Hamming distances before system operation. This allows the system to quickly compare received messages against the predetermined codebook without performing complex real-time calculations, thereby maintaining measurement precision while minimizing communication and processing time overhead
3Reliability
If the system implements comprehensive codeword validation, then the error rate in safety messages is reduced, but the device complexity and computational requirements increase
Solution Approach 1:
The patent uses copying by transmitting redundant information through encoded codewords. The Hamming distance encoding creates multiple valid representations of system states, allowing the receiver to validate messages by checking against the codebook without requiring complex computational validation, thus reducing error rates while managing device complexity
Data Source
AI summary
A method includes, storing a set of valid codewords including: a first valid functional codeword representing a functional timeout state of a second controller; a first valid fault codeword representing a fault timeout state of the second controller and characterized by a minimum hamming distance from the first valid functional codeword; a second valid functional codeword representing a functional state of a system; and a second valid fault codeword representing a fault state of the system; in response to detecting receipt of a safety message from the second controller within a predefined time quantum, storing the first valid functional codeword in a first memory; in response to detecting a match between contents of the first memory and the first valid functional codeword, outputting the second valid functional codeword; in response to detecting a mismatch between contents of the first memory and every codeword in the first set of valid codewords, outputting the second valid fault codeword.