Steering Angle Sensing With Integrated Revolution Counting
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Solution Overview
Problem
Current steer-by-wire and electric power steering systems require multiple sensors and high accuracy production to determine the steering angle unambiguously, leading to high costs and potential loss of absolute position during vehicle restarts, which affects the true power-on-function.
Innovation Solution
A compact and cost-effective steering system with a single integrated circuit containing a magnetic sensor and a revolution counter, using a magnetic target object and a conductive structure to detect the rotational position and number of revolutions of the spindle nut, ensuring accurate and unambiguous determination of the steering angle.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If two rotational angle sensors with different transmission ratios are used to detect steering angle unambiguously, then measurement precision is improved, but device complexity and manufacturing cost increase
Solution Approach 1:
The patent combines two separate sensor circuits (rotational angle sensor and revolution counter) into a single integrated circuit that processes signals from a single target object. This merging maintains the ability to determine absolute position unambiguously while reducing the number of separate sensor circuits from two to one, thereby lowering device complexity and manufacturing cost.
Solution Approach 2:
The integrated circuit performs multiple functions: it detects both the rotational position (0-360 degrees) and the number of revolutions of the target object using a single circuit design. This multi-functionality eliminates the need for separate dedicated sensors for each measurement task, resolving the contradiction between measurement precision and device complexity.
2Productivity
If rotational angle sensor with index sensor is used to detect number of revolutions, then productivity is improved, but reliability deteriorates due to loss of absolute position during vehicle restart
Solution Approach 1:
The integrated circuit continuously tracks and stores the number of revolutions in memory during vehicle operation. When the vehicle restarts, this pre-stored revolution count is immediately available, allowing the system to rapidly determine the absolute position without needing to recount revolutions from zero. This preliminary action ensures both fast productivity upon restart and reliable true power-on-function capability.
Solution Approach 2:
The system uses feedback from the index signal to continuously update the revolution count in memory during operation. This ongoing feedback mechanism ensures that the stored value is always current and accurate, maintaining reliability during vehicle restarts while enabling quick determination of absolute position, thus resolving the contradiction between productivity and reliability.
3Measurement precision
If high accuracy production is implemented to minimize production tolerance influence on sensor signals, then measurement precision is improved, but manufacturing cost increases
Solution Approach 1:
The integrated circuit incorporates self-calibration and error compensation mechanisms that automatically adjust for production tolerances during initial operation or system initialization. This self-service approach compensates for manufacturing variations without requiring extremely tight production tolerances, thereby maintaining high measurement precision while easing manufacturing requirements and reducing costs.
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 system achieves a true power-on-function with reduced electronic and magnetic components, minimizing the impact of production tolerances and ensuring high accuracy in determining the steering angle, while being more cost-effective and resistant to errors like belt slip.
Implementation Method 1
a magnetic sensor for detecting the rotational position of the magnetic target object
Implementation Method 2
The revolution counter is based on the operating principle of magnetic resistance
Data Source
AI summary
A steering system for a vehicle is disclosed, for example a steer-by-wire steering system or an electric power steering system. The steering system includes a linearly displaceable steering rod, a spindle nut which is coupled to the steering rod and which is rotatable to displace the steering rod, and a detection device for detecting a rotational position of the spindle nut. The detection device comprises a magnetic target object, which is directly or indirectly rotationally coupled to the spindle nut, a magnetic sensor for detecting the rotational position of the magnetic target object, and a revolution counter for detecting a number of revolutions of the magnetic target object. The magnetic sensor and the revolution counter are present in a common integrated circuit.