Torque Converter Slip Error for Road Surface Detection
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Solution Overview
Problem
Existing methods for determining road surface characteristics, such as smoothness or irregularities, are limited to braking and traction-control events and require additional hardware, failing to provide information during steady-speed or accelerating conditions.
Innovation Solution
A method using a torque converter to determine the rotational speed difference between the input and output shafts, calculating a slip error rate, and comparing it to case statements defined by amplitude and duration to identify road surface characteristics like coefficient of friction, allowing for continuous surface characterization without additional hardware.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If wheel speed sensors are added to detect road surface characteristics, then measurement capability is improved, but device complexity increases
Solution Approach 1:
The torque converter, originally designed for power transmission, is made to serve a dual function by using its slip characteristics to detect road surface conditions. This eliminates the need for separate sensing hardware while providing continuous road surface characterization during all driving modes including acceleration, steady-state, and braking conditions.
Solution Approach 2:
The system uses the vehicle's own existing operational parameters (torque converter input and output shaft speeds) to detect road surface characteristics. The torque converter effectively serves itself by providing its own diagnostic information about road conditions through its natural slip behavior during vehicle operation.
2Loss of information
If wheel speed sensors are used during braking events, then road surface information is obtained, but information availability is limited to specific conditions
Solution Approach 1:
The torque converter continuously provides slip information during all driving conditions - acceleration, steady-state cruising, and braking - because it is always engaged during vehicle motion. This enables uninterrupted road surface characterization without requiring separate sensing systems for different driving modes, thereby eliminating information gaps that exist in braking-only detection systems.
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
Enables continuous characterization of road surfaces, including transitions, without relying on braking or traction control, providing accurate information on surface types and friction coefficients during various driving conditions.
Implementation Method 1
a torque converter providing a fluid couple between an input shaft driven by an engine and an output shaft coupled to the driven wheel
Data Source
AI summary
In a method for characterizing a road surface beneath a moving vehicle whose powertrain includes a torque converter coupling the engine to a driven wheel, a set of successive values for the torque converter's slip error rate is generated using filtered values for engine speed and torque converter turbine speed. The road surface characteristic is identified based on the set of slip error rate values, as through a comparison of the set with a plurality of case statements, wherein each case statement corresponds with a different road characteristic and/or general surface type. Weighted average values are calculated based on subsets of the values within the set, for use in identifying transitions from one type of surface to another, or one surface characteristic to another. Indicated slip error rates generated in response to changes in an engine torque demand request are also identified to avoid a false indication.