Estimating Absolute Wheel Roll Radii Using Yaw Rate and Lateral Acceleration
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Solution Overview
Problem
Existing methods for estimating absolute wheel roll radii and vertical compression values of vehicle wheels are prone to errors due to reliance on nominal values and require accurate vehicle velocity measurements, which may not be available in all vehicles, and fail to account for interactions between tire pressure and stiffness.
Innovation Solution
A method that measures yaw rate and wheel speed signals from multiple wheels to determine absolute wheel roll radii and vertical compression values using relationships involving axle width and offset constants, without relying on nominal values or vehicle velocity, and incorporates lateral acceleration signals to estimate compression values.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If relative roll radius estimation is used based on vehicle velocity from angular wheel speed sensors, then the system can identify deviations from nominal values, but the determination becomes error-prone and subject to systemic errors when absolute wheel roll radius is not known
Solution Approach 1:
The patent introduces GPS-derived vehicle velocity as an intermediary measurement to resolve the contradiction between relative roll radius estimation and absolute roll radius determination. By using GPS velocity as an independent reference that does not depend on wheel speed sensors, the system can calculate absolute roll radius through the relationship: roll radius = vehicle velocity / angular wheel speed. This intermediary measurement breaks the error propagation chain inherent in pure sensor-based relative estimation.
2Measurement precision
If GPS equipment is used to determine vehicle velocity for roll radius estimates, then absolute roll radius can be determined, but the solution is not available in all vehicles that lack GPS equipment
Solution Approach 1:
The patent implements a self-service mechanism where the system automatically selects the appropriate velocity source based on availability. When GPS is available, it uses GPS velocity for absolute roll radius determination. When GPS is unavailable, it seamlessly transitions to using vehicle velocity from wheel speed sensors combined with nominal roll radius values. This self-service approach ensures the system remains adaptable and functional across all vehicle configurations without requiring manual intervention or system reconfiguration.
3Reliability
If roll radius change is used for tire pressure monitoring, then tire conditions can be detected, but the interaction between tire pressure and tire stiffness makes it difficult to distinguish their individual effects
Solution Approach 1:
The patent segments the roll radius change measurement into two distinct components: one attributable to tire pressure changes and another to tire stiffness changes. By measuring roll radius at multiple operating conditions and using the relationship between roll radius, vertical compression, and wheel load, the system can isolate pressure-induced roll radius changes from stiffness-induced changes. This segmentation allows independent monitoring of tire pressure and tire stiffness, resolving the interaction problem.
Data Source
AI summary
Methods, apparatuses and computer program products for estimating absolute wheel roll radii and/or a vertical compression value of wheels of a vehicle are disclosed, wherein yaw rates of the vehicle, wheel speeds of first and second wheels, and optionally lateral acceleration of the vehicle are measured and used as a basis for the estimation.