Multiturn Rotary Encoder with Dual Redundant Revolution Tracking
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Solution Overview
Problem
Multiturn rotary encoders that measure the number of shaft revolutions are either dependent on a power supply, leading to data loss when powered off, or require costly battery backup solutions, and there is a need for redundant measurement systems for safety applications.
Innovation Solution
A multiturn rotary encoder design incorporating a single-turn unit for absolute position measurement, a power-dependent first multiturn unit for counting revolutions, and a power-independent second multiturn unit based on gear stages, allowing for initialization and comparison of code words to verify unit functionality upon power restoration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a counter-based multiturn unit is used to measure shaft revolutions, then the number of revolutions can be counted, but the counter value is lost when power supply is switched off
Solution Approach 1:
The encoder is divided into two independent multiturn units: a first multiturn unit with counter electronics that counts revolutions when powered, and a second multiturn unit with gear stages that mechanically tracks revolutions independently of power supply. Each unit has its own code carrier and scanning unit, allowing them to operate autonomously and compensate for each other's limitations.
Solution Approach 2:
The invention changes the operational parameter of the second multiturn unit from active counting to passive mechanical tracking. The gear stages continuously accumulate rotational position mechanically, so when power is restored, the second unit already contains the correct revolution information without needing to retain electrical state.
2Reliability
If a battery is added to maintain counter-based multiturn unit functionality during power loss, then data retention is improved, but device complexity and cost increase
Solution Approach 1:
The invention replaces the electrical energy storage system (battery) with a mechanical energy storage system (gear stages). The gear-based second multiturn unit passively accumulates rotational position through mechanical means, eliminating the need for active power management components like batteries, voltage regulators, and power management circuits.
Solution Approach 2:
The second multiturn unit serves itself by continuously tracking shaft revolutions through its gear stages without requiring external power or control. The mechanical system automatically maintains accurate revolution information throughout power cycles, making the system self-sufficient and eliminating complex power management requirements.
3Reliability
If two independent multiturn units are implemented for redundant measurement, then measurement reliability is improved, but device complexity increases
Solution Approach 1:
Both multiturn units are designed with identical functional architecture (code carrier, scanning unit, evaluation unit) but serve different purposes: the first unit provides active counting when powered, while the second unit provides passive mechanical tracking. This universal design allows the system to achieve redundancy through functional differentiation rather than structural complexity.
Solution Approach 2:
The evaluation unit serves as an intermediary that receives data from both multiturn units and performs initialization and comparison functions. It mediates between the two units by using the second unit's mechanically tracked position to initialize the first unit's counter, thereby integrating the redundant measurements into a unified reliable output.
Data Source
AI summary
A multiturn rotary encoder includes: a single-turn unit, including a code carrier that is able to be scanned by a single-turn scanner in order to generate single-turn position signals, and a single-turn evaluation unit for processing the single-turn position signals to form at least one single-turn code word that indicates the absolute position of an input shaft within one revolution; a first multiturn unit dependent on a power supply, including at least a first multiturn code carrier that is able to be scanned by a first multiturn scanner in order to generate first multiturn position signals, and a first multiturn evaluation unit for processing the first multiturn position signals to form a first multiturn code word that indicates the number of revolutions executed by the input shaft; and a second multiturn unit independent of a power supply, including at least a second multiturn code carrier that is able to be scanned by a second multiturn scanner in order to generate second multiturn position signals, and a second multiturn evaluation unit for processing the second multiturn position signals to form a second multiturn code word which likewise indicates the number of revolutions executed by the input shaft. The value of the first multiturn code word of the first multiturn unit in an initialization phase after the power supply of the multiturn rotary encoder has been switched on is able to be referenced with the value of the second multiturn code word.