Fail-Safe Position Detection Device for Vehicle Shift Levers
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Solution Overview
Problem
Conventional position detection devices for vehicle shift levers lack fail-safe mechanisms against power supply failures and detector failures, particularly in shift-by-wire systems, where a single power supply failure can lead to undetected and uncorrected errors.
Innovation Solution
A position detection device with two independent detection systems, each powered by a different power supply system, utilizing multiple magnetic sensors to output distinct detection patterns for different positions, ensuring a minimum 'humming distance' of 4 or more, allowing for error detection and correction even if one system fails.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a single power supply feeds a detector in a shift-by-wire system, then the device complexity is reduced, but the reliability deteriorates due to inability to detect or correct errors from power supply failures
Solution Approach 1:
The detection system is segmented into two independent detection systems, each fed by a separate power supply system. This segmentation allows the system to maintain operation and detect errors even if one power supply fails, as the other system continues to provide detection capability.
Solution Approach 2:
The patent changes the parameter of power supply configuration from a single shared power supply to multiple independent power supplies. This parameter change enables the system to detect and correct errors by comparing outputs from both systems, achieving fail-safe operation.
2Measurement precision
If multiple detectors are used to increase detection accuracy, then the measurement precision improves, but the device complexity increases due to additional components and configuration
Solution Approach 1:
The patent merges the functionality of multiple detectors into a unified detection system where four detectors work together to produce a four-digit detection pattern. This merging approach achieves high measurement precision through redundant detection while maintaining systematic organization that manages complexity.
Solution Approach 2:
The detection system uses four detectors that each produce a binary output, creating a four-digit detection pattern that serves as a coded representation of the operating unit's position. This copying approach enables error detection and correction by having multiple representations of the same positional information.
3Reliability
If detection patterns are designed with high humming distance for error detection, then the reliability improves, but the device complexity increases due to complex pattern configuration requirements
Solution Approach 1:
The patent changes the parameter of detection pattern design by setting specific output relationships among the four digits: certain two digits are made identical to each other and different from the other two digits. This parameter change ensures a minimum humming distance of 2 within one system and 4 across two systems, enabling error detection and correction without requiring overly complex pattern designs.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The device ensures fail-safe operation by detecting and correcting errors with multiple sensors, maintaining accurate position detection despite power supply or detector failures, and simplifies configuration while reducing overall dimensions.
Implementation Method 1
Each of the first detection system and the second detection system includes four detectors each of which has a detection function with one bit that outputs one of two values that varies according to a positional relationship with a detection target unit
Data Source
AI summary
A position detection device includes two detection systems that are respectively fed from power supply systems different from each other, and displace together with a shift lever. Each detection system can output detection patterns with four digits. A detection pattern when being located at a given position is different from a detection pattern when being located at another position. In any detection pattern, outputs of certain two digits among the four digits are set so as to be identical to each other, and to be different from outputs of two other digits. Alternatively, outputs of certain three digits among the four digits are set to be identical to each other, and to be different from an output of another digit.