PLC Output Signal Smoothing for Stable External Device Response
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Solution Overview
Problem
Programmable logic controllers (PLCs) often cause transient responses in external devices due to abrupt changes in digital signal outputs, leading to potential malfunctions or damage.
Innovation Solution
A PLC control apparatus and method that smooths the gradient of digital output signals using a non-linear correction function, specifically a sigmoid function, and adjusts the offset gain with a linear correction function, converting the signals into analog outputs to prevent transient responses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the PLC digital signal output value is abruptly changed at a specific point, then the PLC response speed is improved, but the external device experiences transient response leading to malfunction or damage
Solution Approach 1:
The patent applies preliminary action by pre-calculating and storing correction values in a correction value storage unit before the actual signal output. The correction values, which represent gradient smoothing amounts, are prepared in advance based on target values and interpolation frequencies, allowing the system to smoothly transition without abrupt changes that cause transient responses in external devices
Solution Approach 2:
The patent changes parameters by dynamically adjusting the gradient of the PLC digital signal output through interpolation frequency and target value modifications. The correction value calculation unit computes appropriate correction amounts based on these parameter changes, transforming the abrupt step function output into a smoothed signal that maintains response speed while preventing device damage
2Reliability
If a non-linear correction function with high interpolation frequency is applied to smooth the signal gradient, then the transient response of external devices is prevented, but the device complexity increases
Solution Approach 1:
The patent segments the signal processing function into distinct modular units: a correction value calculation unit that computes smoothing parameters, a correction value storage unit that stores pre-calculated values, and an interpolation unit that applies the sigmoid function. This segmentation allows each unit to perform its specific function independently, simplifying the overall system design while achieving reliable signal smoothing
Solution Approach 2:
The patent uses copying by storing correction values in advance in the correction value storage unit based on predetermined target values and interpolation frequencies. Instead of calculating correction values in real-time during operation, the system copies and retrieves pre-computed values, reducing computational complexity while maintaining the reliability benefits of high-frequency interpolation
Data Source
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AI summary
Disclosed are an apparatus and a method for controlling a PLC output signal. The method includes receiving the PLC digital output signal and interpolating a gradient of the PLC digital output signal by applying a nonlinear correction function to the received PLC digital output signal. The embodiment provides a stable output control apparatus and a stable output control method capable of allowing an external device controlled by a PLC to smoothly output a response and a PLC output is gradually changed to prevent the external device to be controlled from being malfunctioned or broken.