Linear Solenoid Valve Controller Noise Suppression
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Solution Overview
Problem
The controllability of the exciting current in linear solenoid valves is compromised due to noise components superimposed on the current, affecting the accuracy of PWM cycle average calculations, and the robustness of dither control is reduced by changes in power supply voltage and resistance values.
Innovation Solution
A controller that executes pulse width modulation control and dither control with a dither correction amount calculation process, where the dither correction amount is calculated by multiplying the ratio of the control value of the pulse width modulation signal and the average current value by a dither current value, ensuring the increase in exciting current is canceled out within one dither cycle, and using the same sampling period for average current value calculations in feedback and dither correction processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the average value of the exciting current is calculated in one PWM cycle, then the calculation speed is fast, but the calculation accuracy is lowered due to noise components
Solution Approach 1:
The patent segments the averaging period into multiple PWM cycles (specifically 10 cycles) rather than averaging over a single PWM cycle. This segmentation allows noise components to be distributed and canceled out across multiple cycles, improving calculation accuracy while maintaining acceptable response time for control applications.
Solution Approach 2:
The patent employs periodic sampling and averaging over a fixed number of PWM cycles (10 cycles) to systematically reduce noise impact. By consistently averaging over this periodic interval, the system achieves stable and accurate current measurements that are robust against transient noise while maintaining real-time control capability.
2Ease of operation
If dither control is executed based on average current value, then static friction is reduced, but controllability deteriorates due to noise affecting average value calculation
Solution Approach 1:
The patent segments the averaging process to cover 10 PWM cycles, which provides a more accurate representation of the true average current by filtering out noise. This improved accuracy ensures that the dither control is based on reliable current measurements, thereby maintaining controllability while reducing static friction through effective dithering.
Solution Approach 2:
The patent implements feedback control where the averaged current value (computed over 10 PWM cycles) is continuously used to adjust the PWM duty cycle. This feedback mechanism, combined with the noise-resistant averaging method, ensures that dither control operates accurately despite the presence of noise, maintaining system controllability.
3Manufacturing precision
If dither correction amount is calculated for each PWM cycle, then control precision is improved, but calculation load increases
Solution Approach 1:
The patent merges the averaging process with the dither correction calculation by computing the average current value over 10 PWM cycles and then using this averaged value to determine the dither correction amount. This combined approach maintains control precision through accurate current measurement while reducing calculation load by performing the averaging operation once per dither cycle rather than requiring separate complex calculations for each PWM cycle.
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 improves the controllability and robustness of the exciting current by suppressing the influence of noise and maintaining control accuracy despite changes in power supply voltage and resistance, reducing calculation load and preventing excessive current flow.
Implementation Method 1
executing a pulse width modulation control for controlling an exciting current of the linear solenoid valve
Implementation Method 2
execute a dither control that periodically increases and decreases the exciting current through correction with a dither correction amount to vibrate a spool of the linear solenoid valve
Data Source
AI summary
A controller for a linear solenoid valve is configured to: calculate an average value of an exciting current within a period including a natural number multiple of the dither cycle as an average current value; execute a feedback control on a control value of the pulse width modulation signal such that a target value of the exciting current and the average current value match; and calculate a dither correction amount by multiplying a ratio between the control value of the pulse width modulation signal obtained by the feedback control and the average current value by a dither current value that is a current value corresponding to the dither correction amount and calculating the dither correction amount such that an increase in the exciting current due to the dither correction amount is canceled out by a decrease in the exciting current due to the dither correction amount within one dither cycle.