Signal Processing Arrangement for Rotary Encoder Amplitude Error Compensation
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Solution Overview
Problem
Conventional rotary encoders using magnetic field sensors face angular errors due to amplitude deviations, sensitivity variations, and misalignment issues when processing sine and cosine signals, leading to non-linear errors in determining the rotation angle.
Innovation Solution
The proposed solution involves regulating the amplitudes of the input signals based on actual peak values to ensure coincidence, compensating for amplitude misalignment, and applying offset and phase corrections to improve linearity in determining the rotation angle, using adjustable gain blocks, trigonometric processing, and compensation mechanisms.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional trigonometric functions are applied to sine and cosine signals from magnetic field sensors, then the rotation angle can be determined, but amplitude deviations and misalignment cause angular errors and non-linear errors
Solution Approach 1:
The patent applies parameter changes by dynamically adjusting the amplitude of the sine and cosine signals to ensure they have equal amplitudes. This is achieved through detecting peak values of both signals and applying gain adjustments to equalize their amplitudes, thereby eliminating amplitude deviation errors and improving the linearity of rotation angle determination.
Solution Approach 2:
The patent implements feedback mechanisms by continuously monitoring the peak values of sine and cosine signals and using this information to adjust their amplitudes. The system also applies offset corrections based on detected signal characteristics, creating closed-loop feedback that compensates for amplitude deviations and maintains accurate angle measurement throughout operation.
2Adaptability or versatility
If magnetic field sensors are used to generate sine and cosine signals, then angular position can be determined, but sensitivity variations and misalignment lead to amplitude deviations
Solution Approach 1:
The patent applies self-service by enabling the signal processing system to automatically detect and correct its own errors. The system autonomously identifies amplitude deviations, offset errors, and phase shifts in the sine and cosine signals, then applies appropriate corrections without external intervention, compensating for sensor misalignment and sensitivity variations.
Solution Approach 2:
The patent implements preliminary action by performing offset correction and amplitude equalization before the final angle calculation. The system detects signal characteristics in advance and applies corrective transformations to the sine and cosine signals, ensuring they meet ideal requirements before trigonometric processing occurs.
3Measurement precision
If compensation schemes like current spinning or chopping techniques are applied, then some angular errors are reduced, but non-linear errors remain
Solution Approach 1:
The patent applies segmentation by dividing the error compensation process into distinct stages: offset correction, amplitude equalization, and phase alignment. Each stage addresses specific types of errors independently, with offset correction eliminating DC offsets, amplitude equalization ensuring equal signal amplitudes, and phase alignment correcting phase shifts, thereby comprehensively reducing both linear and non-linear errors.
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
This approach effectively compensates for amplitude, offset, and phase deviations, enhancing the linearity of rotation angle determination and reducing non-linear errors, thereby improving the accuracy of rotary encoders.
Implementation Method 1
such rotary encoders are usually built using a geometrical arrangement of magnetic field sensors like CMOS Hall elements, in conjunction with a magnetic source like a permanent magnet rotated above them
Data Source
AI summary
In a signal processing arrangement a first and a second input signal associated with the rotating object are received at signal inputs. Amplitude processing blocks are connected to the signal inputs and each have an adjustable gain. A trigonometric processing block has inputs coupled to outputs of the second amplitude processing blocks via respective signal paths. The trigonometric processing block is configured to determine a magnitude value and a phase value based on signals at its inputs. The signal processing arrangement further has compensation blocks configured to store values at the inputs of the trigonometric processing block as respective peak values, when the phase value assumes a respective phase value. A gain value is determined by applying a respective regulation function to respective amplitude errors being based on the peal values, and the gains of the amplitude processing blocks are adjusted based on the respective gain values.