Electromechanical Power Steering Absolute Angle Measurement
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Solution Overview
Problem
Conventional electromechanical power steering systems face challenges in accurately determining the absolute angle of rotation of the steering shaft across multiple revolutions, requiring complex calibration and expensive construction, and lack efficient measurement methods that function when the ignition is switched off.
Innovation Solution
An electromechanical power steering system that uses a combination of a rotor position sensor and a steering angle sensor unit, with an evaluation unit to calculate a highly accurate absolute angle of rotation by storing measurement tuples and adjusting for the number of revolutions, simplifying the construction and calibration process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If two gear transmissions are used to determine absolute angle, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The patent extracts the absolute angle determination function from complex gear transmissions and implements it through a single gear transmission combined with electronic signal processing. The steering angle sensor unit uses a simplified gear mechanism where the sensor element detects the position of the gear wheel, and the evaluation unit electronically calculates the absolute angle by combining rotor angle data with gear transmission ratios, eliminating the need for multiple mechanical gearings.
Solution Approach 2:
The patent replaces complex mechanical gear transmission systems with an electronic measurement and calculation system. Instead of using two mechanical gear transmissions to achieve both absolute angle determination and high angular resolution, the system uses a single gear transmission and processes signals electronically through the evaluation unit, which combines rotor position sensor data with steering angle sensor data to compute the absolute angle.
2Measurement precision
If two sensors are used to monitor steering shaft and rotor position, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The patent merges the functions of multiple sensors into a coordinated system where a rotor position sensor and a steering angle sensor unit work together. The evaluation unit combines the signals from both sensors, using the rotor angle data and steering angle data along with the gear transmission ratio to calculate the absolute steering shaft angle, achieving high measurement precision without requiring separate independent sensor systems.
3Device complexity
If conventional sensors are used to measure steering angle, then device complexity is reduced, but measurement precision deteriorates
Solution Approach 1:
The patent implements a feedback mechanism where the evaluation unit continuously processes signals from the rotor position sensor and steering angle sensor unit, using the gear transmission ratio to calculate and update the absolute angle value. This feedback loop ensures that the system maintains high measurement precision by constantly adjusting and verifying the angle measurement based on the coordinated input from both sensors.
4Measurement precision
If complex calibration procedures are used, then measurement precision is improved, but loss of time increases
Solution Approach 1:
The patent performs preliminary actions by storing the gear transmission ratio and calibration data in the evaluation unit before actual measurement operations. The system pre-calculates and stores the relationship between rotor angle and steering shaft angle based on the gear transmission ratio, allowing for quick and accurate absolute angle determination without requiring complex real-time calibration procedures during vehicle operation.
Data Source
AI summary
A device and a method may be used to determine a highly accurate absolute angle of rotation Xt of the rotational position of a rotatably supported steering shaft. Rotation of a rotor of an electric motor with a gearing with a gearing transmission factor K for power assistance may be coupled into rotation of the steering shaft. A rotational position of rotation of the rotor can be measured by means of a rotor position sensor and by using a number of revolutions of the rotor that have occurred. This value is used directly to determine the highly accurate absolute angle of rotation Xt of the steering shaft. Calibration methods involve determining initial values from which the counting of revolutions or the calculations occur.