Multi-Gear Absolute Position Sensing for Actuator Accuracy
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Solution Overview
Problem
Conventional electromechanical actuators face issues with positional accuracy due to susceptibility to electrical noise and wear, especially with analog position sensors, and require complex and costly solutions for absolute position sensing, which also lead to delays in real-time control applications.
Innovation Solution
A system of N gears with unique tooth counts, where angular position sensors measure the position of each gear within one rotation, and a control module calculates the angular position of the input shaft over multiple rotations using measured values and pre-stored reference values, enabling absolute digital position sensing without the need for multiple sensors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If analog position sensors are used, then position sensing is achieved, but the motor becomes susceptible to electrical noise and wear, reducing accuracy and device life
Solution Approach 1:
The patent replaces mechanical contact-based position sensing (analog sensors with sliding/rolling contacts) with a magnetic field-based sensing system using magnets attached to gears and magnetic sensors. This substitution eliminates wear from mechanical contact while maintaining position sensing capability, directly resolving the contradiction between measurement precision and reliability.
Solution Approach 2:
The patent creates multiple copies of the position sensing system by attaching multiple magnets to different gears (first gear, second gear, etc.) and using corresponding magnetic sensors. Each gear-magnet-sensor combination provides redundant position information, enhancing reliability through multiple independent sensing channels while maintaining accurate position measurement.
2Measurement precision
If incremental position encoders are used, then position sensing is achieved, but homing operation is required upon power-up, causing delay and motion detrimental to real-time control
Solution Approach 1:
The patent performs preliminary action by pre-establishing the relationship between multiple gear positions and the input shaft position during system initialization. By using multiple gears with different tooth counts and their corresponding magnetic sensors, the system pre-calculates and stores position mapping information, enabling immediate absolute position determination upon power-up without requiring homing operation.
Solution Approach 2:
The patent implements feedback by continuously monitoring the positions of multiple gears through magnetic sensors and using this information to calculate the absolute position of the input shaft. The control module processes feedback from multiple sensor channels simultaneously, enabling real-time position determination without time-consuming homing sequences.
3Measurement precision
If multiple sensors are used for absolute position sensing, then position accuracy is improved, but device complexity and manufacturing cost increase
Solution Approach 1:
The patent applies universality by using the same type of magnetic sensor for multiple measurement functions. The same magnetic sensor technology is used to detect positions of the first gear, second gear, and additional gears, eliminating the need for different sensor types and reducing overall system complexity while maintaining absolute position sensing accuracy.
Solution Approach 2:
The patent merges multiple position sensing functions into a unified system where multiple magnetic sensors detect positions of different gears, and a control module integrates this information to determine absolute input shaft position. This combining approach reduces device complexity by using identical sensor components and a centralized processing unit rather than separate sensing systems.
4Reliability
If absolute position sensors with separate power supplies are used, then position maintenance after power loss is achieved, but system complexity and manufacturing cost increase
Solution Approach 1:
The patent implements self-service by using the motor's own operation to maintain position information. The multiple gears are driven by the motor itself, and their positions are continuously tracked by magnetic sensors powered by the same motor power supply. This eliminates the need for separate power supplies while maintaining the ability to determine absolute position after power loss through the gear train's mechanical memory.
Data Source
AI summary
Methods and systems for measuring multi-turn angular position include a system of N gears meshed with one another, each gear having a unique number of teeth. A first gear is mounted to an input shaft. A set of N angular position sensors are each configured to measure the angular position of a respective gear in the system of N gears within one rotation. A control module is configured to determine an angular position of the input shaft over multiple rotations using the measured angular positions of the N gears.