Encoder Offset Voltage Correction Circuit
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Solution Overview
Problem
Conventional encoders suffer from phase errors due to offset voltages, which impair the linearity of encoder square-wave signals and can prevent the generation of these signals when pseudo sine-wave signal amplitudes are small.
Innovation Solution
An encoder with a displacement detection unit, signal generation unit, center voltage output setting unit, and a multiplication processing circuit that includes a mode switching unit, offset voltage detection unit, and offset voltage correction unit to correct offset voltages and improve signal linearity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional encoders use pseudo sine-wave signals from light receiving elements, then displacement detection is enabled, but offset voltages cause phase errors and impair signal linearity
Solution Approach 1:
The patent applies preliminary action by detecting the center voltage of the pseudo sine-wave signal in advance and using this detected center voltage as a reference for differential processing. This preliminary detection of the center voltage allows the system to compensate for offset voltages before they cause phase errors in the final displacement measurement, thereby maintaining signal linearity while enabling precise displacement detection.
2Use of energy by moving object
If pseudo sine-wave signal amplitudes are small, then energy consumption is reduced, but offset voltages prevent generation of encoder square-wave signals
Solution Approach 1:
The patent implements feedback by using the detected center voltage to dynamically adjust the differential processing reference. This feedback mechanism allows the system to maintain signal generation capability even when pseudo sine-wave signal amplitudes are small, as the center voltage detection and differential processing compensates for offset voltages that would otherwise prevent encoder square-wave signal generation.
3Reliability
If complex arithmetic processing is used to correct offset voltages, then signal linearity improves, but device complexity increases
Solution Approach 1:
The patent applies the taking out principle by extracting only the essential center voltage information from the pseudo sine-wave signal and using this extracted parameter for differential processing. This approach corrects offset voltage effects without requiring complex arithmetic processing, as the system only needs to detect and utilize the center voltage reference point rather than performing elaborate calculations.
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 solution effectively corrects offset voltages, enhances the linearity of encoder square-wave signals, and allows for higher resolution displacement detection without requiring complex arithmetic processing or nonvolatile memory for offset storage.
Implementation Method 1
The original signal generating means 1001 includes a light emitting element 1101, a rotating plate 1102, a stationary plate 1103, a light receiving element 1104
Implementation Method 2
The light receiving element 1104 outputs a current corresponding to the incident light
Data Source
AI summary
An encoder includes a scale, an encoder head, and a multiplication processing circuit. The encoder head includes a signal generation unit configured to generate a substantially sine-wave signal, and an output unit configured to output one of the substantially sine-wave signal and the center voltage of the substantially sine-wave signal to the multiplication processing circuit. The multiplication processing circuit includes a mode switching unit configured to switch a processing mode to one of an offset voltage detection processing mode in which an offset voltage serving as a difference between a predetermined reference voltage and the center voltage is corrected, and a displacement amount detection processing mode in which displacement detection processing is performed, an offset voltage detection unit configured to detect the offset voltage, and an offset voltage correction unit configured to correct an offset voltage of the substantially sine-wave signal output from the output unit.