Vehicle Steering Torque Control via Offset Correction
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Solution Overview
Problem
Conventional electric power steering apparatuses are affected by road surface states and mechanical system changes due to aging, leading to inconsistent steering torque delivery.
Innovation Solution
A vehicle steering apparatus with a torsion bar and sensors that uses a target steering torque generating section, converting section, and torsional angle control to maintain desired steering torque by following a target torsional angle, incorporating an offset correcting section to suppress unintended assist and stabilize steering operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional electric power steering apparatus uses feed-back control of motor current, then assist torque can be generated, but steering torque becomes inconsistent due to road surface states and mechanical aging
Solution Approach 1:
The patent implements feedback control by detecting the actual steering torque via torque sensor and comparing it with the target steering torque, then adjusting motor current to minimize the deviation. This closed-loop control ensures consistent steering torque delivery despite road surface variations and mechanical aging.
Solution Approach 2:
The system dynamically adjusts motor current parameters based on detected steering torque and deviation from target values. By changing electrical parameters (current magnitude and direction) in response to mechanical conditions, the system maintains reliable steering torque across varying operating conditions.
2Reliability
If offset value of steering torque is not corrected, then system remains simple, but unintended assist occurs and steering operation becomes unstable
Solution Approach 1:
The offset correcting section performs preliminary correction of steering torque by detecting and compensating for offset values before they cause unintended assist. This preventive approach stabilizes steering operation without requiring complex real-time intervention mechanisms.
Solution Approach 2:
The patent replaces complex mechanical adjustment mechanisms with electronic offset correction through software/algorithms in the control unit. The ECU calculates and compensates for torque offset values electronically, achieving stable steering operation with simpler physical hardware.
3Measurement precision
If motor current is controlled based on steering torque deviation, then assist torque accuracy improves, but system becomes more complex
Solution Approach 1:
The control unit performs multiple functions including torque detection, offset correction, target torque calculation, and motor current control within a single integrated device. This multi-functionality achieves precise steering assist without proportionally increasing system complexity.
Solution Approach 2:
The patent introduces a target steering torque as an intermediary value that mediates between detected steering torque and required motor current. This intermediate parameter simplifies the control logic by providing a clear reference point for current adjustment, improving accuracy without excessive complexity.
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
The solution ensures consistent steering torque delivery independent of road surface states and mechanical changes, providing improved steering stability and reduced unintended assist.
Implementation Method 1
a torsion bar 2A having any spring constant
Data Source
AI summary
A vehicle steering apparatus that obtains the appropriate steering torque to the steering angle without being affected by road surface state and changes of mechanical characteristics of the steering system due to aging. The steering apparatus includes a target steering torque generating section to generate a target steering torque, a converting section to convert the target steering torque into a target torsional angle, and a torsional angle control section to calculate a motor current command value so as to follow-up a torsional angle to the target torsional angle. The target steering torque generating section includes an offset correcting section to obtain the first torque signal from a characteristic depending on the set steering angle based on an offset value of the steering torque and outputs the first torque signal as a target steering torque. The steering apparatus drives and controls the motor based on the motor current command value.