Electric Power Steering Manual Input Detection
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Solution Overview
Problem
Conventional electric power steering systems struggle to accurately detect manual inputs during automatic steering control due to reliance on threshold-based methods, leading to potential delays and discomfort for drivers and passengers.
Innovation Solution
The system calculates the time series response of the torsion bar torque based on mechanical equations and compares it with detected values to accurately determine manual inputs, using a matching degree assessment that integrates the difference between calculated and detected steering torques over time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If threshold-based methods are used to detect manual inputs during automatic steering control, then the system structure remains simple, but the detection precision is insufficient leading to delays and unnecessary stops
Solution Approach 1:
The patent replaces simple threshold-based detection with a physics-based mechanical model that calculates expected torsion bar torque using the equation Tbar = Jh*s''(t) + Dh*s'(t) + Kh*s(t). This substitution of mechanical modeling for empirical thresholding achieves precise detection without requiring complex additional sensors or systems.
Solution Approach 2:
The system uses existing sensors (steering angle sensor, acceleration sensor) to gather data that feeds into the mechanical model. The model itself serves as the detection mechanism by comparing calculated torque with actual torque from the torsion bar, eliminating the need for separate detection hardware.
2Reliability
If threshold-based detection is used, then the control system remains simple, but the automatic steering control stops unnecessarily causing discomfort
Solution Approach 1:
The patent implements continuous feedback by comparing the calculated torsion bar torque (from the mechanical model) with the actual detected torque. This feedback loop allows the system to distinguish between normal torque variations and actual manual inputs, preventing false stops and maintaining smooth operation.
Solution Approach 2:
The system performs preliminary calculation of expected torsion bar torque using the mechanical model before making detection decisions. By predicting what the torque should be under automatic control conditions, the system can proactively identify deviations indicating manual input without waiting for threshold violations.
3Measurement precision
If mechanical equation-based detection is implemented, then the manual input detection precision improves, but the calculation complexity increases
Solution Approach 1:
The patent applies a dynamic mechanical model that accounts for inertial (Jh*s''(t)), damping (Dh*s'(t)), and spring (Kh*s(t)) components of the torsion bar system. This dynamic approach captures the time-varying behavior of the steering system, enabling accurate detection across different operating conditions without requiring overly complex calculations.
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 approach enables precise detection of manual inputs, preventing unnecessary stops of automatic steering control and ensuring smooth transitions to manual control, thus enhancing steering performance and comfort.
Implementation Method 1
a torsion bar 9 which is interposed within the column shaft 2, a steering angle sensor 14 for detecting a steering angle θ of the handle 1 by means of a torsional angle of the torsion bar 9
Data Source
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AI summary
[Problem] An obj ect of the present invention is to provide an electric power steering apparatus that performs a judgment of a manual input during an automatic steering control by an accurate and precise method based on the mechanical equation, and have a steering performance which a driver and a fellow passenger do not feel uncomfortable. [Means for solving the problem] The present invention is an electric power steering apparatus that assist-controls a steering system by driving a motor based on a motor current command value and has a function performing an automatic steering control and a manual steering control, comprising: a function that calculates a time series response of a torsion bar torque based on a mechanical equation due to characteristics of a handle and a torsion bar, judges an adaptation degree of the calculated steering torque calculated-value and a detected value of the torsion bar torque, and judges "presence" or "absence" of a manual input during the automatic steering control by means of the adaptation degree.