Vehicle Steering Angle Estimation via Dynamic Wheel Speed Weighting
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Solution Overview
Problem
Existing vehicle steering angle calculation methods are prone to accuracy deterioration due to wheel slip or lock during acceleration or deceleration, leading to potential violent movements in estimated steering angles.
Innovation Solution
An estimated steering angle calculation device that combines first and second estimated steering angles based on front and rear wheel speed differences, weighted by accelerator opening degree or brake treading force to improve accuracy and prevent sudden changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the average estimated steering angle is calculated by averaging the first estimated steering angle (based on front wheel speeds) and the second estimated steering angle (based on rear wheel speeds), then a robust redundant system is formed, but the accuracy deteriorates when wheel slip or lock occurs due to acceleration or deceleration
Solution Approach 1:
The patent applies dynamics by making the contribution rates of front and rear wheel speed differences variable based on accelerator opening degree and brake treading force. Instead of using fixed equal weighting, the system dynamically adjusts the weighting coefficients (alpha and beta) according to vehicle operational conditions. During acceleration or deceleration when slip or lock may occur, the contribution rates are modified to reduce the influence of potentially inaccurate measurements, thereby maintaining reliability while improving accuracy.
Solution Approach 2:
The patent changes the parameters of the estimation system by introducing variable contribution rates (alpha and beta) that depend on accelerator opening degree and brake treading force. When the accelerator opening degree increases or brake treading force increases, indicating acceleration or deceleration conditions, the system adjusts these parameters to weight the front and rear wheel speed differences differently, suppressing the deterioration of accuracy caused by wheel slip or lock.
2Device complexity
If equal weighting is applied to front and rear wheel speed differences, then the calculation is simple, but the estimated steering angle may exhibit violent movements during acceleration or deceleration
Solution Approach 1:
The system transitions from static equal weighting to dynamic variable weighting based on vehicle operational state. The contribution rates alpha and beta are adjusted according to accelerator opening degree and brake treading force, making the weighting scheme adaptive to changing conditions. This dynamic approach prevents violent movements in the estimated steering angle during acceleration or deceleration while maintaining reasonable calculation complexity.
Solution Approach 2:
The patent introduces accelerator opening degree and brake treading force as intermediary parameters that mediate between the raw wheel speed measurements and the final estimated steering angle. These intermediary variables provide information about vehicle operational conditions, allowing the system to adjust the contribution of front and rear wheel speed differences appropriately, thereby stabilizing the estimated steering angle during transient conditions.
Data Source
AI summary
There is provided an estimated steering angle calculation device for a vehicle capable of suppressing deterioration in accuracy of an estimated steering angle even if vehicle wheels slips or is locked due to acceleration or deceleration of the vehicle. Although, when being accelerated during turning, tire gripping force of front wheels serving as a driving wheel increases and a difference between wheel speeds of the front wheels decreases so that an estimated steering angle θes relative to an actual steering angle θact tends to decrease, the deterioration in accuracy of the estimated steering angle θes due to this tendency can be suppressed by increasing a second contribution rate relative to the estimated steering angle θes on the rear wheel side and decreasing a first contribution rate on the front wheel side in accordance with an accelerator opening degree.