Vehicle Steering Device Hands-On Detection
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Solution Overview
Problem
Existing vehicle steering systems often inaccurately determine whether the steering wheel is being held or not, leading to erroneous interpretations of steering wheel operation states, especially when external forces from the road surface are applied.
Innovation Solution
A vehicle steering device incorporating a driver torque estimation observer, low-pass filter, and hands-on/off determination unit, which estimates driver torque using torsion bar torque and rotational angle data, and filters this torque to precisely distinguish between hands-on and hands-off states.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If work load is used to determine steering wheel operation state, then the determination process is simple, but the determination accuracy deteriorates due to external forces from road surface
Solution Approach 1:
The patent introduces a driver torque estimation observer as an intermediary component that processes multiple sensor inputs (torsion bar torque, steering angle, motor torque) to generate an estimated driver torque value. This estimated value serves as a mediator between the raw sensor data and the final hands-on/off determination, filtering out external road surface forces while preserving genuine driver input signals.
Solution Approach 2:
The system implements feedback by continuously monitoring multiple parameters (torsion bar torque, steering angle, motor torque) and using the driver torque estimation observer to continuously update the estimated driver torque. This feedback loop allows the system to adapt to changing conditions and distinguish between external disturbances and actual driver operations more accurately.
2Loss of information
If torque sensor and steering angle sensor are used, then more information is available, but the determination accuracy still deteriorates due to road surface forces generating false work load signals
Solution Approach 1:
The driver torque estimation observer acts as an intermediary that intelligently processes information from multiple sensors (torque sensor, steering angle sensor, motor torque sensor) while filtering out misleading signals caused by road surface forces. It synthesizes these inputs to produce a reliable estimated driver torque that represents actual driver operation intent.
Solution Approach 2:
The patent replaces direct mechanical threshold-based determination with a computational estimation system. Instead of directly using mechanical sensor outputs to determine hands-on/off state, the system uses the driver torque estimation observer to computationally estimate driver torque, substituting mechanical determination with intelligent signal processing.
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 configuration allows for accurate determination of steering wheel operation states, reducing false positives and negatives, and enabling precise mode switching control between manual and automatic operation modes.
Implementation Method 1
an output shaft coupled to the input shaft via a torsion bar
Data Source
AI summary
A vehicle steering device includes a steering wheel, an input shaft, an output shaft coupled to the input shaft via a torsion bar, an electric motor, a torque detector that detects a torsion bar torque applied to the torsion bar, a rotational angle detector that detects a rotational angle of the electric motor, and a microcomputer. The microcomputer is configured to estimate a driver torque applied to the steering wheel using at least (i) the torsion bar torque detected by the torque detector, (ii) the rotational angle of the electric motor detected by the rotational angle detector, and (iii) a physical model that is constructed with a torsion bar viscosity and a torsion bar rigidity, and determine whether the steering wheel is operated in a hands-on state or a hands-off state based on the estimated driver torque.