Steering Lock Control Using Latch Circuits for ASIL-D Safety
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Solution Overview
Problem
Conventional steering lock systems face challenges in achieving high safety levels like ASIL-D without increasing manufacturing costs and software verification burdens, especially in vehicles with manual transmissions, where additional sensors are needed, and require redundant microcomputer systems for accurate steering lock activation.
Innovation Solution
A steering lock system that utilizes a power supply and latch circuit to determine the vehicle's running state, with a steering lock controller and driver to manage lock requests, reducing the need for redundant microcomputers and dedicated sensors by using existing vehicle power supply signals for state determination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If redundant microcomputer systems are used to determine vehicle stopped state, then safety level (ASIL-D) is improved, but device complexity and software verification burden increase
Solution Approach 1:
The patent combines multiple state determination signals (power supply signal, shift P signal, vehicle speed signal) into a unified determination process within a single microcomputer system. The latch circuit integrates these signals to generate a comprehensive stopped state determination, eliminating the need for separate redundant microcomputer systems while maintaining ASIL-D safety level.
Solution Approach 2:
The microcomputer system is designed to handle multiple functions: it processes power supply signals, shift P signals, and vehicle speed signals through the latch circuit to determine both stopped state and steering lock control. This multi-functional approach replaces multiple specialized microcomputers, reducing device complexity while preserving safety requirements.
2Measurement precision
If dedicated sensors are installed to obtain stopped state signals, then measurement precision is improved, but manufacturing cost increases
Solution Approach 1:
The patent repurposes existing vehicle sensors and signals (power supply signal, shift P signal, vehicle speed signal) for stopped state determination. These existing components serve multiple functions in the vehicle system, and the latch circuit integrates them without requiring dedicated new sensors, thereby maintaining measurement precision while avoiding additional manufacturing costs.
Solution Approach 2:
The system uses already-available vehicle signals and existing sensor outputs to determine stopped state. The latch circuit processes signals that are naturally generated by the vehicle's power supply system, transmission system, and speed sensing system, making the existing infrastructure serve the additional function of steering lock control without requiring external dedicated sensors.
Data Source
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AI summary
A steering lock system (1) includes: a power supply configured to become an ON state when a vehicle is in a state capable of running; a latch circuit (15) configured to hold output of an ignition power-supply signal indicating the ON state or OFF state of an ignition power supply (5); a steering lock controller (8) configured to perform lock determination of a steering (2) of the vehicle and output a lock request signal for requesting lock of the steering (2) depending on a result of the lock determination; and a steering lock driver (7) configured to lock the steering (2) based on the lock request signal and the power-supply signal.