Steer-by-Wire Angle Sensing via Gear-Reduced Motor Shaft Detection
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Solution Overview
Problem
Steer-by-wire steering systems face challenges in accurately determining the absolute steering angle without mechanical connections, as existing sensors are prone to environmental influences and require complex wiring, and existing encoder solutions are ambiguous due to high motor revolutions.
Innovation Solution
A sensor array coupled to the motor shaft via a gearbox, which reduces relative movement speed and ensures unambiguous correlation with the steering angle, integrated with a compact design to protect against environmental influences, using magnetoresistive, inductive, or optical sensors, and optionally a rotor position sensor for enhanced resolution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If angle sensors are installed in the steering linkage to detect steering angle, then steering angle detection is enabled, but the system becomes vulnerable to environmental influences and requires complex wiring
Solution Approach 1:
The patent replaces mechanical sensors in the steering linkage with a magnetic field-based detection system. A magnetic field generator is mounted on the motor shaft, and a magnetic field sensor is mounted on the housing, eliminating the need for mechanical connections and wiring in the steering linkage area. This substitution removes the system's vulnerability to environmental influences while maintaining steering angle detection capability.
2Measurement precision
If rotary encoders are used on the motor shaft to detect steering angle, then steering angle can be determined, but the high number of motor revolutions creates ambiguous correlation with steering angle
Solution Approach 1:
The patent introduces a magnetic field generator mounted on the motor shaft that rotates with it, creating a rotating magnetic field. A magnetic field sensor mounted on the housing detects this field. The gear ratio between the motor shaft and steering linkage serves as an intermediary that reduces the high-speed rotation to a lower speed, establishing an unambiguous correlation between the magnetic field variations and the steering angle position.
3Measurement precision
If absolute position sensors are used in the steering linkage, then absolute steering angle can be detected, but calibration is required after power loss
Solution Approach 1:
The patent performs preliminary action by continuously monitoring the relationship between motor shaft position and steering linkage position during normal operation. The control unit stores this correlation data, so when power is restored after a failure, the system already has the necessary calibration information and can immediately resume accurate absolute steering angle detection without requiring time-consuming recalibration procedures.
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
Enables reliable and precise determination of the steering angle, minimizing wiring and environmental vulnerability, with improved resolution and cost-effectiveness through a compact, integrated design.
Implementation Method 1
a magnetic field generator (32) mounted on the motor shaft (18) such that the magnetic field generator (32) generates a magnetic field that rotates with the motor shaft (18)
Implementation Method 2
a magnetic field sensor (33) mounted on the housing (36) such that the magnetic field sensor (33) detects the magnetic field
Implementation Method 3
The sensor can be, in particular, a magnetoresistive sensor and/or an inductive sensor
Implementation Method 4
The sensor can be, in particular, a magnetoresistive sensor and/or an inductive sensor
Data Source
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AI summary
The invention relates to a steer-by-wire steering system (10) for a motor vehicle, comprising an electric motor (20) for effecting the steering movement of the steering system (10) and a steering linkage (12) for transmitting the steering movement in the direction of the wheels of the motor vehicle, wherein the electric motor (20) is mechanically coupled to the steering linkage (12) via a steering gear (16) in such a way that a steering movement of the steering system (10) over the entire possible steering angle range of the steering system (10) requires a plurality of revolutions of the motor shaft (18), and a sensor arrangement (34) for detecting the movement of the motor shaft (18) with a sensor (38) and a target (40) detectable by the sensor (38).The sensor arrangement (34) is coupled to the motor shaft (18) via a gearbox (32) such that the motor shaft (18) causes a relative movement between the sensor (38) and the target (40), which enables a unique assignment between the relative position of the target (40) to the sensor (38) and the steering angle of the steering system (10).