Steering Wheel Position Estimation Using Dual Dynamic Models
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Solution Overview
Problem
Existing methods for determining the absolute angular position of a vehicle's steering wheel, particularly in electric power steering systems, face precision and reliability issues due to the limitations of dynamic models used, which can lead to inaccurate results in extreme driving conditions.
Innovation Solution
A method that involves estimating the absolute angular position using two distinct dynamic models, one based on wheel speed differences and the other on yaw rate, with a verification step to compare the differences against a coherence threshold, allowing for the exclusion of unreliable values and iterative learning adjustments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a single dynamic model is used to estimate absolute angular position, then the method is simple and fast, but precision and reliability degrade in extreme driving conditions
Solution Approach 1:
The patent divides the estimation process into multiple independent dynamic models (first model based on wheel speed difference, second model based on yaw rate), each handling specific driving conditions. This segmentation allows the system to maintain high precision across diverse scenarios while keeping each individual model simple and computationally efficient.
Solution Approach 2:
The system dynamically switches between different dynamic models based on driving conditions by comparing estimated values against coherence thresholds. This parameter change approach enables the system to adapt to extreme driving conditions by selecting the most appropriate model, thereby maintaining precision without requiring a single complex universal model.
2Measurement precision
If multiple dynamic models are used to improve precision, then measurement accuracy increases, but computational complexity and processing time increase
Solution Approach 1:
The patent applies partial action by using multiple simplified dynamic models rather than one comprehensive complex model. Each model performs a specific estimation function (wheel speed-based or yaw rate-based), and the system combines results selectively. This approach achieves high precision through multiple partial estimations while avoiding the computational burden of a single excessive complex model.
Solution Approach 2:
The system implements feedback by comparing the estimated values from different models against predetermined coherence thresholds. This feedback mechanism validates the consistency of estimates and enables dynamic selection of reliable models, reducing processing time by eliminating inconsistent results early in the computation process.
3Reliability
If dynamic models are used without verification, then the method is computationally efficient, but reliability decreases due to model limitations in extreme conditions
Solution Approach 1:
The patent incorporates feedback through coherence threshold comparison, where the system continuously monitors the consistency of estimates from different dynamic models. This feedback loop identifies when model limitations are activated (e.g., in extreme driving conditions) and triggers appropriate responses such as switching models or flagging unreliable estimates, thereby enhancing reliability without requiring overly complex verification procedures.
Solution Approach 2:
The system prepares for model failures in extreme conditions by establishing coherence thresholds and alternative models in advance. This beforehand cushioning approach ensures that when a dynamic model reaches its validity limits, the system already has prepared fallback mechanisms (alternative models or threshold-based rejection) to maintain reliability, avoiding the need for complex real-time verification procedures.
Data Source
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AI summary
The invention relates to a method for determining the absolute angular position of a steering wheel (3) of a vehicle, said method involving an initial-estimate step (a) during which a first value (Angle1) indicative of the absolute angular position of said steering wheel (3) is evaluated by a first model based on analyzing a first vehicle running dynamic parameter, such as the speed differential of the wheels of one wheelset, a second-estimate step (b) during which a second value (Angle2) indicative of the absolute angular position of said steering wheel is evaluated by a second model based on analyzing a second dynamic parameter, such as the yaw rate, followed by a checking step (c) during which the difference between the first value (Angle1) and the second value (Angle2) is compared against a predetermined consistency threshold (S) in order to decide, through suitable weighting, whether said values are to be considered or excluded.