Magnetic Rotary Encoder Controller for INL Error Compensation
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Solution Overview
Problem
Magnetic rotary encoders face significant challenges in reducing integral non-linearity errors, which affect the accuracy of determining the position of a rotating magnet, and existing correction methods require calibration and cannot adapt to temperature and lifetime drifts.
Innovation Solution
A controller that receives position parameters from a rotary encoder, determines error compensation parameters based on time marks between predefined angles, and uses these parameters to correct for integral non-linearity errors, allowing for continuous high-accuracy position determination of a rotating magnet.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a burnt INL-correction circuit is used, then INL error is reduced, but the system requires calibration for each chip and cannot react to temperature- and lifetime-drift
Solution Approach 1:
The patent implements a dynamic INL correction approach where correction values are continuously determined based on measured rotation times during operation. Unlike static burnt-in correction circuits, this system adapts to changing conditions (temperature, lifetime drift) by recalculation during runtime, making the correction mechanism flexible and responsive to environmental variations.
Solution Approach 2:
The system performs self-calibration during normal operation by measuring actual rotation times of the magnet and automatically determining correction values without requiring external calibration equipment or manual intervention. The controller uses the encoder's own output signals to generate correction data, enabling the system to self-adjust to drift conditions.
2Object-affected harmful factors
If noise reduction filter is applied, then noise is reduced to about 0.1°, but INL error remains up to 3° and is harder to reduce
Solution Approach 1:
The patent separates noise reduction and INL correction as distinct processing steps. The filter handles high-frequency noise while the subsequent INL correction block addresses systematic position errors. This segmentation allows each component to optimize for its specific function without interfering with the other, achieving both noise reduction and INL compensation.
Solution Approach 2:
The patent introduces an intermediary correction mechanism that processes the filtered encoder output through a lookup table or calculation block that applies position-dependent correction values. This intermediary stage transforms the filtered but still inaccurate position data into corrected position information by compensating for the non-linearities in the encoder's magnetic field sensing.
3Adaptability or versatility
If error correction parameters are continuously calculated during rotation, then adaptability to drift is improved, but additional processing time and complexity are required
Solution Approach 1:
The system calculates error correction parameters periodically based on complete rotation cycles of the magnet. By using the start and end positions of each full rotation as reference points, the controller determines correction values at regular intervals without requiring continuous complex calculations. This periodic approach balances adaptability with processing efficiency.
Solution Approach 2:
The patent changes the parameter used for correction from static factory-calibrated values to dynamic values derived from actual rotation time measurements. By monitoring the time taken for complete rotations and comparing it to expected values, the system adjusts correction parameters based on real operational conditions, achieving adaptability through parameter evolution rather than structural complexity.
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 controller effectively reduces integral non-linearity errors, providing accurate position determination of a rotating magnet by continuously calculating and applying error correction parameters, even in the presence of temperature and lifetime drifts, thereby improving the overall accuracy of the rotary encoder.
Implementation Method 1
The rotating magnet generates a rotating magnetic field that is sensed by the magnetic rotary encoder, for example by Hall sensors of the encoder.
Implementation Method 2
The rotating magnet generates a rotating magnetic field that is sensed by the magnetic rotary encoder, for example by Hall sensors of the encoder.
Data Source
AI summary
A controller (1) to reduce integral non-linearity errors of a magnetic rotary encoder (2) comprises a position error determining unit (20) to determine a plurality of time marks (P0, . . . , Pk) specifying a respective time at which a moving device (3) reaches a respective one of predefined positions (α0, . . . , αk). The position error determining unit (20) calculates a plurality of error correction parameters (B[0], . . . , B[k]) in dependence on the time marks (P0, . . . , Pk). An error compensation unit (10) of the controller determines a respective error compensated position parameter (φstart_comp, φ0_comp, . . . , φn_comp) for each position parameter (φstart, φ0, . . . , φn) received from the encoder (2) in dependence on the respective position parameter (φstart, φ0, . . . , φn) and the respective error correction parameter (B[0], . . . , B[k]).