Sensor Offset Determination in Motor Vehicle Steering Systems
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Solution Overview
Problem
Existing sensor systems in motor vehicle steering systems face inaccuracies due to design-induced constant offsets, which can falsify measured variables, necessitating effective offset correction methods for achieving sufficient measuring accuracy.
Innovation Solution
A method and device for determining sensor offset by generating a predetermined relative motion between two components using an actuator, measuring this motion with a sensor, and calculating the offset from stored data, while accounting for dynamic friction and position-dependent deviations, allowing for periodic and symmetrical motion to simplify and improve measurement accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a sensor is used to monitor mechanical variables in a steering system, then the position and motion can be detected, but design-induced constant offsets falsify the measured variables and reduce measurement accuracy
Solution Approach 1:
The patent applies preliminary action by performing offset determination before normal operation. The control unit generates a predetermined relative motion between the steering wheel and steering column, measures the sensor output during this motion, and calculates the offset value in advance. This pre-calculated offset is then stored and used to correct all subsequent measurements, eliminating the harmful effect of the constant offset from design variations.
2Measurement precision
If static friction between components is present, then the measurement can be falsified or made impossible, but generating and measuring motion cancels out static friction contributions
Solution Approach 1:
The patent applies dynamics by transforming the measurement from a static condition to a dynamic condition. Instead of measuring the sensor output at a fixed position where static friction dominates, the control unit generates a predetermined relative motion between components. During this motion, only dynamic friction acts on the system, and its contributions cancel out over the complete motion cycle. This dynamic measurement approach eliminates the harmful effect of static friction.
3Ease of manufacture
If the measurement method accounts for dynamic friction components only, then the measurement is significantly simplified, but this requires generating and measuring relative motion between components
Solution Approach 1:
The patent applies self-service by using the sensor itself to measure the motion that is generated for calibration. The control unit generates a predetermined relative motion between the steering wheel and steering column, and the same sensor that will be used for normal operation measures this motion. The sensor data during this self-generated motion is processed to determine the offset, eliminating the need for external calibration equipment or complex measurement setups.
4Measurement precision
If the relative motion is periodic and symmetrical with maximum amplitudes, then only symmetrical friction components occur which cancel out, facilitating evaluation of sensor data
Solution Approach 1:
The patent applies periodic action by using a periodic and symmetrical relative motion between the steering wheel and steering column. The control unit generates this periodic motion with specific characteristics (symmetrical about the neutral position, with defined maximum amplitudes), causing only symmetrical dynamic friction components to occur during the motion cycle. These symmetrical friction components cancel out when evaluating the sensor data over the complete period, facilitating accurate offset determination.
Data Source
AI summary
A method for determining a sensor offset of a sensor in a device, in particular in a steering system for a motor vehicle. The device has a first component, a second component which is movable with respect to the first component, a resetting element, an actuator and a sensor for determining the relative motion between the first component and the second component. The method comprises the following steps: firstly, a predetermined relative motion between the first component and the second component is generated by the actuator. The resulting relative motion is measured by means of the sensor, and the sensor data obtained from the measurement are stored. A constant sensor offset of the sensor is then determined on the basis of the stored sensor data. Furthermore, a device is described whose sensor offset can be determined by means of the method.