Handwheel Torque Correction for Accurate Hands-On-Wheel Detection
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Solution Overview
Problem
Existing steering systems, particularly hydraulic systems, face challenges in accurately detecting whether an operator's hands are on the handwheel during rapid steering maneuvers due to the lack of consideration for inertia, damping, and friction effects, leading to errors in hands-on-wheel detection.
Innovation Solution
The method involves generating handwheel speed and acceleration signals, synchronizing them by creating delayed signals, and using these signals to estimate operator torque, accounting for damping, inertia, and friction, while also correcting for offset masses to improve detection accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional hands-on-wheel detection methods are used without considering inertia, damping, and friction effects, then the system is simpler to implement, but detection accuracy deteriorates during rapid steering maneuvers
Solution Approach 1:
The patent applies preliminary action by pre-calculating and storing lookup tables for inertia, damping, and friction effects before operation. These pre-computed values are ready for immediate use during rapid steering maneuvers, eliminating the need for complex real-time calculations while maintaining high detection accuracy
Solution Approach 2:
The patent introduces an intermediary processing layer that synchronizes handwheel signals with steering torque signals using delay correction based on inertia and damping effects. This intermediary layer acts as a mediator between the raw sensor signals and the final detection logic, compensating for dynamic effects without requiring complete system redesign
2Measurement precision
If handwheel signals are not synchronized with steering torque signals, then processing is faster and simpler, but detection accuracy deteriorates due to phase differences during rapid maneuvers
Solution Approach 1:
The patent applies preliminary action by pre-calculating the delay correction values based on the relationship between handwheel angle, speed, acceleration and steering torque during system initialization or calibration phase. These pre-computed delay corrections are stored and applied during operation, avoiding real-time iterative calculations while maintaining synchronization accuracy
Solution Approach 2:
The patent implements dynamic delay correction that adapts to changing steering conditions. The delay amount is not fixed but varies based on handwheel speed and acceleration signals, allowing the system to maintain synchronization accuracy across different maneuver types while keeping processing efficient through piecewise linear approximation
Data Source
AI summary
A method includes receiving a handwheel angle signal, generating a handwheel speed signal and a handwheel acceleration signal, and synchronizing the handwheel speed signal and the handwheel acceleration signal. The method also includes delaying the handwheel angle signal, calculating a sum of the delayed handwheel angle signal and a phase value, converting the sum of the delayed handwheel angle signal and the phase value to radians, determining an offset correction value by calculating a sine function value of the converted sum of the operator torque estimation signal and the phase value, calculating a product of the offset correction value and a calibratable value of an offset mass magnitude, adjusting the operator torque estimation signal by adding the product and the calibratable value of an offset mass magnitude, and determining whether hands of an operator of the vehicle are on the handwheel based on the adjusted operator torque estimation signal.