Absolute Position Encoder with Redundant Spatial Phase Signal
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Solution Overview
Problem
Existing absolute position encoders are prone to measurement errors due to unintended gap variations and roll, pitch, and yaw deviations between the read head and the scale, which are not effectively addressed by current configurations.
Innovation Solution
An electronic absolute position encoder with a scale featuring a periodic and gradual pattern variation component, combined with a detector having spatial phase sensing elements and reference sensing elements, allows for the determination of scale factors that compensate for measurement errors caused by gap deviations and orientation changes, enhancing measurement accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional absolute position encoder configurations are used, then the device structure is simple, but measurement errors occur due to unintended gap variations and roll, pitch, and yaw deviations
Solution Approach 1:
The encoder configuration is segmented into multiple sensing elements arranged in specific patterns (e.g., quadrature arrangements with 90-degree phase shifts). Each sensing element processes specific spatial frequencies, allowing the system to separate and independently correct different types of measurement errors including gap variations and orientation deviations.
Solution Approach 2:
The patent introduces additional spatial dimensions by arranging sensing elements in multi-dimensional patterns (such as 2D arrays or quadrature configurations). This dimensional expansion enables the system to measure and compensate for roll, pitch, and yaw deviations by detecting signal variations across multiple spatial axes simultaneously.
2Measurement precision
If multiple sensing elements are added to compensate for measurement errors, then measurement accuracy improves, but device complexity increases
Solution Approach 1:
The multi-element sensing configuration serves multiple functions simultaneously: it measures primary position, compensates for gap variations, and corrects orientation deviations (roll, pitch, yaw). This universal approach allows a single encoder design to handle various error sources without requiring separate compensation mechanisms for each type of error.
Solution Approach 2:
The sensing elements are pre-configured in specific geometric arrangements (such as quadrature patterns or symmetric configurations) that inherently provide the mathematical relationships needed for error compensation. This preliminary structural setup enables real-time correction of measurement errors through signal processing without requiring additional active components or complex real-time adjustments.
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
The proposed solution effectively cancels out measurement errors due to roll, pitch, and yaw, providing robust and accurate position measurements in high-precision applications.
Implementation Method 1
a scale including a first scale track extending along a measuring axis direction and including a first signal modulating scale pattern
Implementation Method 2
a detector including at least a first set of sensing elements configured to provide a first set of detector signals in response to the first signal modulating scale pattern
Data Source
AI summary
An electronic absolute position encoder is provided having a scale, a detector, and a signal processor configured to determine an absolute position of the detector along the scale. The scale includes a signal modulating scale pattern comprising a periodic pattern component and a gradual pattern variation component. The detector includes N spatial phase sensing elements (e.g., conductive windings) and at least one reference sensing element, which is spaced apart along the measuring axis direction by a distance corresponding to an integer multiple of 360 degrees of spatial phase shift relative to a first one of the N spatial phase sensing elements. A first reference signal from the first reference sensing element and a first signal from the first one of the N spatial phase sensing elements include nominally similar signal contributions from the periodic pattern component, and a difference between the two signals is due to a difference in their signal contributions from the gradual pattern variation component. The difference may be used to determine a scale factor M1 for a gradual signal variation exhibited by the detector signals output from the detector.