Steering Ratio Control Under Abnormal Vehicle Speed Signals
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Solution Overview
Problem
In steer-by-wire systems with redundant calculators, discrepancies in vehicle speed information input to different calculators can lead to instability in steering control when one calculator fails, making it difficult to determine the transmission ratio.
Innovation Solution
A steering control device with multiple communication lines and calculators that independently calculate and validate vehicle speed information, switching to operation-angle responsive control when abnormalities are detected, ensuring stable steering control by bypassing unreliable vehicle speed data.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If vehicle-speed responsive control is used to calculate transmission ratio based on vehicle speed information, then steering control adaptability to different speeds is improved, but system stability deteriorates when vehicle speed information becomes abnormal
Solution Approach 1:
The system implements feedback by comparing vehicle speed information from multiple communication lines and detecting abnormalities. When abnormality is detected, the system switches from vehicle-speed responsive control to operation-angle responsive control, preventing instability while maintaining adaptability during normal operation
Solution Approach 2:
The control system dynamically switches between two modes: vehicle-speed responsive control (for adaptability) and operation-angle responsive control (for stability). This dynamic adjustment allows the system to optimize performance based on the validity of input information
2Reliability
If redundant calculators are used to ensure system reliability, then control continuity is improved, but calculation stability deteriorates when communication lines provide conflicting information
Solution Approach 1:
Each calculator independently compares vehicle speed information received from multiple communication lines and detects abnormalities through feedback mechanisms. This allows redundant calculators to maintain control continuity while avoiding calculation instability by identifying and excluding abnormal data
Solution Approach 2:
The system prepares for potential communication failures by having operation-angle responsive control ready as a backup mode. When abnormality is detected, the system switches to this pre-prepared control mode, cushioning against the impact of conflicting information and maintaining calculation stability
Data Source
AI summary
A steering control device is configured to control a steering device that changes a transmission ratio between an operation angle of an operation member and a steering angle of a steerable wheel. The steering control device includes: communication lines for transmitting vehicle speed information; and calculators communicably connected to each other and individually connected to the communication lines. Each calculator calculates the transmission ratio based on the vehicle speed information received via a corresponding one of the communication lines and determines whether the received vehicle speed information is valid. When at least one of the calculators determines that the vehicle speed information is not valid, each calculator changes control for calculating the transmission ratio from a vehicle-speed responsive control in which the transmission ratio is calculated based on the vehicle speed information to a specific control in which the transmission ratio is calculated not based on the vehicle speed information.