Wheel Rotational Inertia Measurement for Accurate Friction Control
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Solution Overview
Problem
The rotational inertia of vehicle wheels affects tire-ground friction calculation and vehicle performance, particularly when different tires or rims/wheels are mounted, leading to inaccuracies in vehicle control systems like stability and anti-lock braking systems.
Innovation Solution
A method and system for determining vehicle wheel rotational inertia by applying torque at different levels and measuring rotational characteristics using an electric motor and wheel speed sensor, with a controller to calculate inertia based on rotational speeds and accelerations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If rotational inertia is not determined accurately, then vehicle control systems operate with default values, but tire-ground friction calculation and vehicle performance are inaccurate
Solution Approach 1:
The system uses the vehicle's own electric motor and existing wheel speed sensors to perform rotational inertia measurement, eliminating the need for external measurement equipment. The motor serves both as the propulsion system and as the test equipment, allowing the vehicle to measure its own wheel parameters without additional complex hardware
Solution Approach 2:
The controller continuously monitors wheel speed sensor data and uses feedback from multiple torque levels to calculate rotational inertia. The system applies torque at different levels, measures the resulting rotational speeds, and iteratively determines inertia values, with the ability to update inertia values when changes are detected
2Measurement precision
If multiple torque levels are applied to determine rotational inertia, then measurement accuracy improves, but testing time and energy consumption increase
Solution Approach 1:
The system applies torque at multiple levels (first level and second level) to obtain sufficient data for accurate inertia calculation, but only for the duration needed to capture the necessary rotational speed measurements. The method determines inertia as a function of rotational speeds caused by both torque levels without requiring exhaustive testing
Solution Approach 2:
The measurement process uses periodic torque application at different levels, where the controller alternates between first level torque and second level torque to gather data points. This periodic approach allows accurate inertia determination through multiple measurements while managing testing time efficiently
3Adaptability or versatility
If rotational inertia values are updated when changes are detected, then vehicle performance adapts to different tires and rims, but system complexity increases
Solution Approach 1:
The system automatically detects changes in rotational inertia and updates its values without requiring external intervention or complex configuration. The controller monitors wheel behavior and self-adjusts the inertia parameters based on measured data from the motor and speed sensor
Solution Approach 2:
The system dynamically changes the rotational inertia parameter based on detected conditions. When the controller determines that rotational inertia has changed (indicating different tires or rims), it updates the inertia value to reflect the new configuration, allowing the vehicle control systems to adapt to varying wheel characteristics
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Improves the accuracy of tire-ground friction estimation and enhances vehicle control systems by providing precise rotational inertia data for stability and anti-lock braking systems.
Implementation Method 1
an electric motor having a variable torque output. In at least some implementations, electrical power to the electric motor is controlled by a controller to cause the motor to provide the first level of torque and the second level of torque
Implementation Method 2
the rotational speed of the wheel is determined by a wheel speed sensor
Data Source
AI summary
In at least some implementations, a method of determining rotational inertia of a vehicle wheel is accomplished by applying torque to the wheel and determining a rotational characteristic of the wheel resulting from the applied torque. The method includes the steps of applying torque at a first level to a wheel, determining one or more rotational speeds of the wheel caused by the torque at the first level, applying torque at a second level to the wheel, where the second level is different than the first level, determining one or more rotational speeds of the wheel caused by the torque at the second level, and determining a rotational inertia of the wheel as a function of the one or more rotational speeds of the wheel caused by both the torque at the first level and the torque at the second level.