Dual-Sensor Multi-Turn Limiting for Battery-Free Position Tracking
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Solution Overview
Problem
Existing multi-turn limiting devices for motor-driven elements, such as greenhouse windows, face issues with complexity, reliance on batteries, and limited accuracy due to the inability to distinguish between positions separated by integer amounts of turns during power outages, leading to potential damage and safety concerns.
Innovation Solution
A multi-turn limiting device using a movable member with a non-unitary transmission ratio and a second sensor to provide accurate position sensing across multiple turns, employing a combination of transmission ratios to ensure unique sensor readings, and incorporating a processor for error detection and robust operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a single sensor is used to track position over multiple turns, then the device can operate without a battery, but it cannot distinguish between positions separated by integer amounts of turns
Solution Approach 1:
The position sensing function is segmented into two independent sensors: a first sensor providing coarse position information over multiple turns, and a second sensor providing fine position information within a single turn. This segmentation allows the system to achieve both multi-turn tracking and precise position distinction without requiring a battery-powered memory system.
Solution Approach 2:
The solution transitions from a single-dimensional position tracking approach to a two-dimensional sensing approach by introducing a second sensor with a different transmission ratio. This creates a positional encoding system where the combination of readings from both sensors uniquely identifies each position, similar to how a clock face uses hour and minute hands to distinguish time.
2Reliability
If a battery or magnetic induction sensor is used to maintain position information during power outages, then position accuracy is maintained, but the device becomes more complex and/or requires battery replacement
Solution Approach 1:
The system uses the motor's own operational characteristics to maintain position information. During normal motor operation, the two sensors continuously provide position data that is processed by the controller to determine absolute position. This self-service approach eliminates the need for external power sources or magnetic induction sensors, as the motor's operation itself serves to refresh and maintain position information.
Solution Approach 2:
The patent replaces the electrical/magnetic memory systems (batteries, magnetic induction sensors) with a mechanical sensing approach using two sensors and a controller that processes their combined readings. This substitution eliminates moving electrical contacts and magnetic components, resulting in a more reliable, maintenance-free system.
3Measurement precision
If a non-unitary transmission ratio is used with a second sensor, then position sensing accuracy over multiple turns is enhanced, but the transmission system becomes more complex
Solution Approach 1:
The transmission system is designed with different local characteristics for different sensing needs. The first sensor uses a unitary transmission ratio for straightforward multi-turn tracking, while the second sensor uses a non-unitary transmission ratio specifically optimized for providing precise within-turn position information. This local differentiation of transmission characteristics optimizes the overall measurement precision without requiring the entire system to be complex.
Data Source
AI summary
A multi-turn limiting device for limiting movement of an element driven by a motor includes a sensor configured to provide a sensor signal corresponding to a position of the element, a movable member mechanically couplable to the element via a transmission having a non-unitary first transmission ratio and a further sensor configured to provide a further sensor signal corresponding to the position of the movable member. A controller switches the motor via a switching signal determined on the basis of the two sensors. A method of limiting movement of an element driven by a motor includes sensing the position of the element using two sensors and a movable member which is coupled to the element via a non-unitary transmission ratio.