Steer-by-Wire Ratio Synchronization via Adaptive Filter Bandwidth
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Solution Overview
Problem
Steer by wire (SbW) systems often fail to maintain the desired steering ratio during vehicle operation, leading to undesirable effects such as lag in vehicle response and the appearance of autonomous steering, due to issues like exceeding slew rate capabilities, excess load on actuators, and initialization problems.
Innovation Solution
A processor-based system that determines the difference between commanded and achieved steering ratios, adjusting the commanded ratio to match the achieved ratio when exceeding a threshold, and dynamically adjusts the filter bandwidth based on vehicle characteristics like handwheel position, speed, and throttle position to minimize driver perception and ensure synchronization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the commanded steering ratio is rapidly adjusted to match the achieved steering ratio, then the steering ratio synchronization is improved, but noise responses and driver perception of autonomous steering increase
Solution Approach 1:
The filter bandwidth is dynamically adjusted based on operating conditions (vehicle speed, handwheel angle, throttle position). During normal operation, a lower bandwidth filters noise effectively. During centering maneuvers, the bandwidth is increased to allow rapid steering ratio adjustment without triggering autonomous steering perception, thus resolving the contradiction between synchronization precision and noise perception
Solution Approach 2:
The system changes the filter bandwidth parameter adaptively based on vehicle operating conditions. By monitoring vehicle speed, handwheel angle, and throttle position, the system selects appropriate bandwidth values to optimize both noise filtering and steering ratio synchronization performance, preventing the harmful effects of excessive noise or autonomous steering perception
2Device complexity
If a fixed filter bandwidth is used to adjust the commanded steering ratio, then the system complexity is reduced, but the ability to adapt to different vehicle conditions deteriorates
Solution Approach 1:
The filter bandwidth parameter is changed adaptively based on vehicle operating conditions including vehicle speed, handwheel angle, and throttle position. The system implements multiple bandwidth levels (first, second, and third bandwidths) that are selected based on the current operating state, enabling the system to adapt to different conditions without requiring overly complex control mechanisms
Solution Approach 2:
Different filter bandwidths are applied for different operating conditions and steering scenarios. The system uses local quality by tailoring the filter characteristics to specific operating regimes (e.g., higher bandwidth for centering maneuvers, lower bandwidth for normal operation), optimizing performance for each local condition rather than using a uniform approach
Data Source
AI summary
A method for a steer by wire steering system. The method includes determining a difference between a commanded steering ratio and an achieved steering ratio and determining whether the difference between the commanded steering ratio and the achieved steering ratio is greater than a threshold. The method also includes, in response to a determination that the difference between the commanded steering ratio and the achieved steering ratio is greater than the threshold, adjusting the commanded steering ratio to be equal to the achieved steering ratio. The method also includes, in response to a determination that the difference between the commanded steering ratio and the achieved steering ratio is greater than the threshold, selectively adjusting a bandwidth of a filter based on at least one vehicle characteristic of an associated vehicle and adjusting, using the filter, the commanded steering ratio to be equal to a desired steering ratio.