Shaft Position Capture Using Relatively Prime Material Measures
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Solution Overview
Problem
Existing methods for capturing the absolute rotational position of a shaft often face challenges in achieving high resolution and wide measurement range, particularly in scenarios where voltage supply is unreliable, leading to complications in referencing the position after a failure or standstill.
Innovation Solution
The method employs at least two rotational material measures with different numbers of graduations that are relatively prime in pairs, allowing for a quantizable number of rotational states to be captured, and enables these measures to be used in a cascaded and state-synchronous manner to determine the absolute position of the shaft, ensuring unambiguous position determination even without a voltage supply.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If multiple material measures with different numbers of graduations are used to increase measurement range, then the total measurement range increases, but the device complexity increases
Solution Approach 1:
The measurement system is segmented into multiple independent material measures, each with a specific number of graduations. Each material measure can be individually sensed and evaluated, allowing the system to achieve a large total measurement range through the combination of multiple segmented components rather than requiring a single complex measurement system.
Solution Approach 2:
The sensor system is designed to universally sense multiple different material measures using the same sensing mechanism. The evaluation unit processes signals from all material measures and combines them to determine the absolute rotational position, making the system multi-functional in handling different graduation configurations without requiring separate specialized sensors for each material measure.
2Loss of information
If battery-powered electronic components are used to maintain position information, then position data can be stored, but reliability decreases due to battery failure risk
Solution Approach 1:
The system uses the existing kinetic energy and mechanical momentum of the rotating shaft to automatically maintain and update the position information in the non-volatile memory without requiring an external power source. The shaft's own rotation serves the dual purpose of both driving the machine and refreshing the position data, eliminating the need for battery-powered maintenance.
Solution Approach 2:
The system incorporates non-volatile memory that automatically stores position information in advance, cushioning against the risk of power loss. This pre-stored information ensures that position data is preserved and can be immediately retrieved after any power interruption, eliminating the need for battery-powered continuous maintenance and referencing procedures.
3Measurement precision
If high resolution position capture is achieved through multiple material measures, then measurement precision improves, but the number of sensors and complexity increases
Solution Approach 1:
The system uses more graduations on the material measures than the minimum required for a single revolution, creating an excessive number of measurable states. This partial redundancy allows the system to achieve high resolution and wide measurement range while using a manageable number of sensors, as the evaluation unit can process the additional states to determine absolute position without requiring a proportional increase in sensor count.
Data Source
AI summary
The invention relates to a method for capturing an absolute rotational position of a shaft using at least two rotational material measures which are synchronously coupled to the shaft, comprising material measures with a different number of graduations which are each relatively prime in pairs, a determination of the state of the individual material measures by means of sensors, wherein a quantizable number of rotational states Ni is captured for each material measure, the total measurement range of the capture system is determined by the product N=πi=1 Ni of the possible states of all material measure, and each combination of states (a0, a1, a2, . . . , an) occurs exactly once within the total measurement range N, with the result that the absolute position of the shaft can be determined at any time from the combination of states of the material measures. In order to obtain a high resolution and a wide measurement range, provision is made for some of the material measures to have a multiple of the required graduation for determining the states and/or for at least individual material measures to be used in a cascaded and state-synchronous manner.