Multi-turn Position Sensor with Dual Gear Ratios
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Solution Overview
Problem
Existing position sensors for electric motors are inadequate for detecting intermediate positions between end positions, limiting their ability to provide precise data for evaluating the position of an axle over a specified number of turns.
Innovation Solution
A position sensor system utilizing two transmissions with specific gear ratios and contactless magnetic rotary encoders, where the output shaft and output gear wheel are integrated as a single piece, allowing for precise detection of intermediate positions by differing in one turn over the specified number of turns, and utilizing Hall sensors for data decoding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a single transmission is used in the position sensor, then the device complexity is low, but the measurement precision for intermediate positions over multiple turns is insufficient
Solution Approach 1:
The position sensor is divided into two independent transmission systems (first transmission with gearwheel GW1-GW2 and second transmission with gearwheel GW3-GW4), each measuring different aspects of the rotation. This segmentation allows the system to achieve high precision multi-turn measurement by combining data from both transmissions, resolving the contradiction between measurement precision and device complexity.
Solution Approach 2:
The two transmissions are nested within a single position sensor housing, with both gearwheel pairs mounted on the same output shaft OS. The transmissions are integrated together with the output shaft and housing forming a compact unit, allowing complex multi-turn measurement functionality to be contained within a unified structure.
2Measurement precision
If two transmissions with different gear ratios are used, then the position detection precision over multiple turns is improved, but the device complexity increases
Solution Approach 1:
Each transmission is designed with specific local characteristics - the first transmission has gearwheel GW1 with z1 teeth and GW2 with z2 teeth, while the second transmission has gearwheel GW3 with z3 teeth and GW4 with z4 teeth. These different local gear ratios are optimized for their respective measurement functions, allowing high precision multi-turn detection while maintaining manageable complexity through specialized design.
Solution Approach 2:
Both transmissions share common components including the output shaft OS, housing GE, and magnetic encoder M, making these elements serve multiple functions. The gearwheels GW1-GW4 are all mounted on the same output shaft and measured by the same encoder, creating a universal measurement system that achieves enhanced precision without proportionally increasing overall complexity.
3Manufacturing precision
If the output shaft and output gear wheel are integrated as one piece, then the manufacturing precision is improved, but the adaptability for different sensor configurations is reduced
Solution Approach 1:
The output shaft OS and output gear wheel OGW are merged into a single integrated component, eliminating potential errors from relative movement or misalignment between separate parts. This integration significantly improves manufacturing precision and assembly reliability, while the modular position sensor design allows the integrated unit to be adapted to different sensor configurations through the holding plate HP1 and distance pieces DP.
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 precise detection and evaluation of intermediate positions, allowing the electric motor to accurately determine the end positions and stop at specified turns, enhancing the motor's control and positioning accuracy.
Implementation Method 1
a magnetic encoder (M) for decoding the angular positions of the gearwheels (GW1, GW2, GW3, GW4)
Implementation Method 2
utilizing Hall sensors for data decoding
Data Source
Figure 1
Figure 2
AI summary
The invention relates to a position sensor (PS) that is in position to deliver data for evaluating positioning data of an axle (OS) over a specified number of turns, where two transmissions (G1, G2) are affixed to the axle (OS) for being in position to transmit each the position of the axle to a rotary encoder (RE), the transmission ratios being chosen such that over the specified number of turns of the axle (OS) both transmissions (G1, G2) at the output differ in one turn, as well as to an evaluation circuit, and to an electric motor.