Steering Torque Estimation for Reliable Automated Driving Handover
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Solution Overview
Problem
Existing methods for terminating automated driving operations in vehicles are prone to unintentional termination due to inaccuracies in measuring manual steering torque, especially during rapid steering interventions.
Innovation Solution
A method that estimates manual torque by measuring steering column torque and steering wheel angle, using a model equation that considers the moment of inertia of the steering wheel and frictional torque in the steering system.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If steering column torque is measured using a torque sensor to determine steering intervention, then the measurement is simple and direct, but the measurement accuracy deteriorates during rapid steering interventions causing unintentional termination
Solution Approach 1:
The patent introduces a model-based estimation system that acts as an intermediary between the steering column torque sensor and the termination decision logic. Instead of directly using the measured steering column torque, the system uses a dynamic model that incorporates steering wheel angle, angular acceleration, moment of inertia, and frictional torque to estimate the actual manual torque applied by the driver. This intermediary estimation layer filters out false signals during rapid steering interventions while preserving genuine driver intent.
Solution Approach 2:
The patent replaces the direct mechanical measurement approach (steering column torque sensor) with a computational estimation approach. The system substitutes the physical measurement of manual torque with a mathematical model that calculates estimated manual torque based on measurable parameters (steering wheel angle, angular acceleration) and known system properties (moment of inertia, frictional torque). This substitution eliminates the measurement inaccuracies inherent in direct torque sensing during dynamic conditions.
2Device complexity
If a torque sensor is installed on the steering column to measure steering torque, then the device complexity is reduced, but the measurement accuracy deteriorates during rapid steering interventions
Solution Approach 1:
The patent introduces a model-based estimation system that acts as an intermediary between the steering column torque sensor and the termination decision logic. Instead of directly using the measured steering column torque, the system uses a dynamic model that incorporates steering wheel angle, angular acceleration, moment of inertia, and frictional torque to estimate the actual manual torque applied by the driver. This intermediary estimation layer filters out false signals during rapid steering interventions while preserving genuine driver intent.
Solution Approach 2:
The patent replaces the direct mechanical measurement approach (steering column torque sensor) with a computational estimation approach. The system substitutes the physical measurement of manual torque with a mathematical model that calculates estimated manual torque based on measurable parameters (steering wheel angle, angular acceleration) and known system properties (moment of inertia, frictional torque). This substitution eliminates the measurement inaccuracies inherent in direct torque sensing during dynamic conditions.
3Speed
If the deactivation threshold is set low to detect driver intention quickly, then the responsiveness is improved, but the risk of unintentional termination increases
Solution Approach 1:
The patent implements a feedback mechanism where the estimated manual torque is continuously compared against dynamically adjusted deactivation thresholds. The system provides feedback by monitoring the driver's steering behavior over time and adjusting the threshold based on the estimated torque rather than raw sensor data. This feedback loop enables quick detection of genuine driver intent while filtering out transient disturbances, as the estimation model incorporates frictional torque and moment of inertia to distinguish between intentional steering and system-induced torque variations.
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
This method provides a more robust estimation of manual torque, reducing the risk of unintentional termination of automated driving and allowing for accurate detection of the driver's intention to take control.
Implementation Method 1
a steering column torque at the steering column is measured
Implementation Method 2
the estimation is based on a model equation of the steering system, which takes into consideration a moment of inertia of the steering wheel
Implementation Method 3
a frictional torque in the steering system
Data Source
AI summary
A method for terminating an automated driving function of a vehicle involves deactivating the driving function by a steering intervention of a driver of the vehicle in a steering system, which includes a steering column and a steering wheel. In order to determine the steering intervention, a steering column torque at the steering column is measured and a steering wheel angle is measured. A manual torque acting on the steering wheel is estimated based on the measured steering column torque and the measured steering wheel angle. The estimation is based on a model equation of the steering system, which takes into consideration a moment of inertia of the steering wheel and a frictional torque in the steering system.