Wheel Contact Force Control for Road Friction Measurement
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Solution Overview
Problem
Existing methods for determining road surface friction coefficients often result in undesirable changes to vehicle dynamics, affecting the operator, cargo, and surrounding traffic.
Innovation Solution
A method that sets contact forces for ground engaging members to achieve a target global load vector with minimal deviation, allowing for the determination of road capability parameters like friction and load bearing without significant vehicle motion changes, using a control unit to manage contact forces and apply them via a ramp function.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If vehicle dynamics are changed to determine road surface friction coefficient, then measurement precision is improved, but vehicle stability deteriorates
Solution Approach 1:
The vehicle's ground engaging members are divided into two subsets: a first subset used for determining road capability parameters by applying controlled contact forces, and a second subset that maintains normal operation to preserve vehicle stability. This segmentation allows friction measurement on specific wheels without requiring overall vehicle dynamics changes.
Solution Approach 2:
Contact forces are applied locally to specific ground engaging members in the first subset rather than to the entire vehicle. This localized application enables road capability measurement at specific contact points while the rest of the vehicle maintains its normal stable operation.
2Measurement precision
If contact force is applied to ground engaging members for road capability determination, then measurement precision is improved, but vehicle operation convenience deteriorates
Solution Approach 1:
The control system segments ground engaging members into measurement subset and normal operation subset, allowing friction determination on specific wheels while the vehicle continues to operate normally with the other wheels, thus maintaining operational convenience.
Solution Approach 2:
The system preliminarily identifies and selects specific ground engaging members for measurement purposes before applying contact forces, ensuring that the measurement process can be initiated without disrupting the overall vehicle operation and driver control.
Data Source
AI summary
The invention relates to a method for determining a parameter indicative of a road capability of a road segment supporting a vehicle. The vehicle comprises a plurality of ground engaging members. The method comprises: for each ground engaging member in a sub-set of the plurality of ground engaging members, setting a contact force between the ground engaging member and the road segment; determining a target global load vector to be imparted to the vehicle, the target global load vector comprising at least a vertical load and an inclining moment, determining contact forces for the ground engaging members of the plurality of ground engaging members which are not in the sub-set such that the contact forces for the plurality of ground engaging members together result in a resulting global load vector, a difference measure between the resulting global load vector and the target global load vector being equal to or lower than a predetermined difference measure threshold, applying the contact force to each ground engaging member of the plurality of ground engaging members, for at least one ground engaging member in the sub-set, determining a parameter indicative of the road capability of the road segment associated with the ground engaging member.