Rotary Encoder Calibration for Temperature Drift Compensation
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Solution Overview
Problem
Rotary encoders face accuracy deviations due to temperature changes, affecting precise positioning and control in machines, especially in environments with varying ambient temperatures.
Innovation Solution
A method for calibrating rotary encoders involves rotating the machine shaft at a predefined speed, capturing position values at initial and altered sensor temperatures, determining deviations, and correcting output signals to maintain accuracy across temperature changes, using a stationary sensor unit and exciter unit configuration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the rotary encoder is calibrated at room temperature, then the measuring accuracy is high at room temperature, but the measuring accuracy deteriorates at increased ambient temperatures due to temperature drift
Solution Approach 1:
The patent applies preliminary action by performing calibration at multiple predetermined temperatures before actual operation. The rotary encoder is calibrated at room temperature and at least one other temperature, and correction values are stored in advance. During operation, the appropriate correction value is selected based on the current temperature, eliminating temperature drift effects without requiring real-time recalibration.
Solution Approach 2:
The patent changes the calibration parameter (temperature) to multiple predetermined values. By calibrating at different temperatures and storing correction values for each temperature level, the system adapts to temperature variations. The correction values are selected based on the current temperature, allowing the encoder to maintain accuracy across different thermal conditions.
2Adaptability or versatility
If calibration is performed at multiple temperatures to compensate for temperature drift, then temperature adaptability improves, but the calibration complexity and time increase
Solution Approach 1:
The patent performs the time-consuming multi-temperature calibration process in advance during manufacturing or setup. The correction values for multiple temperatures are predetermined and stored in memory before the encoder enters service. During actual operation, the system simply reads the stored correction values based on current temperature, making the calibration process instantaneous and eliminating ongoing calibration time losses.
Solution Approach 2:
The patent creates copies of calibration data at different temperatures and stores them in memory. Instead of performing actual physical recalibration at each temperature change, the system uses pre-captured measurement data and correction values that replicate the effect of multi-temperature calibration. This copying approach maintains temperature adaptability while eliminating the time required for repeated calibration procedures.
3Measurement precision
If the sensor unit is heated or cooled to different temperatures for calibration, then temperature drift compensation accuracy improves, but the energy consumption increases
Solution Approach 1:
The patent performs the energy-intensive heating and cooling calibration process once during manufacturing or initial setup. The correction values for multiple temperatures are predetermined and stored in memory. During normal operation, the system only needs to sense the current temperature and select the appropriate pre-stored correction value, eliminating the need for continuous heating or cooling cycles and significantly reducing ongoing energy consumption.
4Measurement precision
If correction values are stored for multiple temperatures, then the measuring accuracy across different temperatures improves, but the memory requirements and device complexity increase
Solution Approach 1:
The patent changes the calibration parameter (temperature) to multiple predetermined values and stores correction data for each. By organizing the correction values in a structured manner indexed by temperature, the system achieves comprehensive temperature compensation. The complexity is managed by using a straightforward lookup approach where the current temperature directly identifies the appropriate correction value, keeping the implementation simple despite multiple temperature points.
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 method allows for high measuring accuracy and precise rotational angle determination independent of ambient and sensor temperatures, ensuring accurate motor control and positioning even under temperature fluctuations.
Implementation Method 1
The sensor unit (12) comprises a Hall sensor (18)
Implementation Method 2
heating or cooling at least the stationary sensor unit to a second sensor temperature
Implementation Method 3
The reason for such a temperature-dependent deviation, which is also referred to as 'temperature drift', at an increased temperature may, for example, be an expansion of the materials used at the rotary encoder
Data Source
AI summary
A method for calibrating a rotary encoder for capturing rotational angle position of a machine shaft. The rotary encoder includes an exciter unit which is rotationally fixed to the machine shaft, and a stationary sensor unit which interacts therewith. The method includes rotating the machine shaft to perform a rotational movement at a predefined rotational speed at a first sensor temperature, capturing a first position measured value at a first predefined rotational angle position at the first sensor temperature, heating or cooling the sensor unit to a second sensor temperature, capturing a second position measured value at the first predefined rotational angle position at the second sensor temperature, determining a first deviation between at least the second position measured value and a first desired position measured value, and correcting an output signal from the rotary encoder via the first deviation.