Multi-turn Rotation Angle Detection Using Prime Gear Ratios
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Solution Overview
Problem
Existing multi-turn rotation angle detection systems face challenges in achieving a wide detection range without increasing mechanistic complexity, size, and cost, while also dealing with the complexity of computation and memory usage in determining multi-turn absolute positions.
Innovation Solution
A transmission mechanism that uses a single change ratio between adjacent rotating shafts, allowing for the calculation of multi-turn absolute rotation angles using a formula that approximates detected values, reducing the need for multiple gear types and memory storage, and enabling flexible design of detection ranges.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If multiple gear types with different change ratios are used to expand multi-turn detection range, then the detection range increases, but the number of gear types and device complexity increases
Solution Approach 1:
The patent changes the parameter of gear tooth count to achieve different change ratios. By using gears with tooth counts that are relatively prime numbers (e.g., 20 teeth and 21 teeth), the system expands the multi-turn detection range without needing multiple sets of gears with different change ratios. The detection range becomes the product of the tooth counts of all gears in the transmission chain, significantly increasing versatility while maintaining a uniform gear structure.
2Measurement precision
If high-precision angle detectors are used for each rotating shaft, then measurement precision improves, but device complexity and cost increase
Solution Approach 1:
The patent merges the measurement functions of multiple angle detectors into a single angle detector. By using the transmission mechanism to relate the rotation angles of multiple shafts and detecting only the first shaft's angle, the system achieves the same measurement precision as if multiple detectors were used, but with reduced device complexity and cost.
Solution Approach 2:
The transmission mechanism acts as an intermediary that translates the rotation angles of multiple shafts into a relationship where only one angle needs to be measured. The gear transmission ratios serve as the intermediary factor that connects the unmeasured shaft angles to the measured shaft angle, enabling precise multi-turn detection through a single detector.
3Adaptability or versatility
If multiple rotating shafts with different change ratios are used, then multi-turn detection range expands, but computation complexity increases
Solution Approach 1:
The patent changes the parameter of gear tooth counts to relatively prime numbers, which simplifies the computation of multi-turn detection range. The detection range becomes simply the product of these tooth counts, avoiding the need for complex least common multiple calculations required when using non-relatively-prime gear ratios.
4Adaptability or versatility
If large memory is used to store detection data for wide multi-turn range, then detection range increases, but device size and cost increase
Solution Approach 1:
The patent replaces the need for large memory storage with a mechanical transmission system. Instead of storing detection data for the entire multi-turn range in memory, the gear transmission mechanism physically encodes the multi-turn information in the rotational positions of multiple shafts, allowing the system to achieve wide detection range with minimal memory requirements.
Data Source
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AI summary
There is provided a method for calculating with high accuracy a multi-turn absolute rotation angle of a motor rotating shaft coupled to a motor output shaft. In a rotation angle detection device according to this invention, a rotation angle θn of an n-th rotating shaft satisfies the relationship with a rotation angle θ1 of the motor rotating shaft: θn = (-(m±1)/m)n-1×θ1. The rotation angle detection device as an embodiment of a mechanism satisfying the relationship includes a gear mechanism in which a gear having (m±1) teeth meshes with a gear having m teeth between each adjacent two of first to n-th rotating shafts. A multi-turn rotation angle of the first rotating shaft is expanded to a detected value p1 of the first rotating shaft which is a rotation angle of the first rotating shaft and R0xm0+R1×m1+...Rn-2×mn-2 corresponding to the number of revolutions of the first rotating shaft, coefficients R0 to Rn-2 are obtained on the basis of detected values from angle detectors of the respective shafts, and the multi-turn rotation angle of the first rotating shaft is calculated. Detection errors generated in the angle detectors of the second and subsequent rotating shafts can be effectively reduced, and a high-accuracy multi-turn rotation angle can be calculated.