Hydrostatic Pressure Unit With Pulsation-Selective Inverter Control
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Solution Overview
Problem
Existing fluid pressure units experience instability in discharge pressure and flow rate due to pulsations caused by hydraulic pump discharge fluctuations and motor torque ripple, leading to reduced stability when controlled by an inverter.
Innovation Solution
A fluid pressure unit equipped with a detector to measure pressure and/or flow rate, a controller to maintain predetermined values, and a suppressor, such as a band stop or notch filter, to mitigate the impact of pulsation frequency components, adjusting the stop band based on pump rotational speed and teeth number to stabilize discharge.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the inverter controls the motor based on detected pressure and flow rate to maintain predetermined values, then the pressure and flow rate stability improves, but pulsation frequency components in the detected value cause instability and reduced control accuracy
Solution Approach 1:
A suppressor unit is introduced as an intermediary component between the pressure detector and the inverter controller. This suppressor specifically targets and removes pulsation frequency components from the detected pressure signal before it reaches the controller, allowing accurate pressure control without the destabilizing influence of pulsation artifacts in the detection data
Solution Approach 2:
The system uses feedback control where the inverter adjusts motor operation based on detected pressure values to maintain predetermined pressure levels. The suppressor enhances this feedback mechanism by ensuring that only relevant pressure information (without pulsation noise) is used for control decisions, improving both stability and accuracy
2Reliability
If the suppressor strongly suppresses pulsation frequency components, then pressure stability improves, but responsiveness of the motor and pump in higher frequency ranges deteriorates
Solution Approach 1:
The suppressor is designed with frequency-selective characteristics, applying strong suppression specifically at pulsation frequency components while maintaining minimal impact on other frequency ranges. This localized suppression approach ensures that pressure stability is improved at the problematic frequencies without compromising the overall responsiveness of the motor and pump system
Solution Approach 2:
The suppressor's frequency characteristics are optimized to change suppression strength based on frequency parameters. By adjusting the suppression profile to be frequency-dependent, the system achieves strong attenuation of pulsation frequencies while preserving responsiveness in higher frequency ranges where motor and pump dynamic performance is critical
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 system effectively suppresses fluctuations in discharge pressure and flow rate, maintaining stability even with changing rotational speeds, thereby enhancing the responsiveness and reliability of the motor and pump operation.
Implementation Method 1
the suppressor may be a band stop filter in which a frequency of the pulsation frequency component is included in a stop band
Implementation Method 2
the band stop filter may be a notch filter in which the frequency of the pulsation frequency component is included in the stop band
Data Source
Figure 1
Figure 2~3
Figure 4~5
AI summary
A fluid pressure unit is provided with an inverter (17), a motor (10) controlled by the inverter, a pump (11) driven by the motor to discharge a fluid, a detector (16) configured to detect a pressure of the fluid, a flow rate of the fluid, or both, a controller (20) configured to control the inverter such that a pressure of the pump, a flow rate of the pump, or both becomes a predetermined value based on a detected value by the detector, and a suppressor (33) configured to suppress a change of an output of the inverter caused by a pulsation frequency component of the fluid included in the detected value.