Variable-Capacity Pump Calibration for Nonlinear Flow Control
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Solution Overview
Problem
Existing calibration methods for current-controlled variable-capacity pumps suffer from inaccuracies due to manufacturing variations and hysteresis, especially in non-linear characteristics, leading to deviations from ideal operation.
Innovation Solution
A control calibration apparatus and method using a controller and flow sensor, particularly a pressure sensor, to determine a quadratic function formula based on measured current values at maximum and minimum flow rates, along with a fixed intermediate flow rate, to improve accuracy by calibrating the current-to-flow characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If pressure change point detection method is used for calibration, then calibration can be performed without additional instruments, but calibration accuracy deteriorates because the change point is difficult to find
Solution Approach 1:
The patent replaces pressure-based detection with flow rate-based detection. Instead of using pressure sensors to detect change points (mechanical/physical system), the invention uses flow rate measurements combined with quadratic function fitting to determine calibration points, thereby improving accuracy while maintaining ease of calibration
Solution Approach 2:
The patent creates a mathematical model (quadratic function) that copies and represents the actual current-to-flow characteristics. By fitting a quadratic function to measured data points, the system creates an accurate representation of the pump's behavior without needing to directly detect difficult physical change points
2Device complexity
If straight line calibration is used for non-linear pumps, then calibration process is simple, but calibration accuracy deteriorates especially for non-linear characteristics
Solution Approach 1:
The patent applies curvature by using quadratic functions instead of straight lines to model the current-to-flow characteristics. The quadratic function y = ax² + bx + c captures the non-linear (curved) behavior of variable-capacity pumps, thereby improving calibration accuracy for non-linear characteristics while adding only moderate complexity
Solution Approach 2:
The patent changes the mathematical model from linear (straight line) to quadratic (curved) to better match the actual non-linear characteristics of the pump. This parameter change in the calibration approach allows accurate representation of non-linear behavior without excessive complexity
3Productivity
If manufacturing variations and hysteresis are not compensated, then calibration process is simple, but flow control accuracy deteriorates
Solution Approach 1:
The patent implements feedback by measuring actual flow rates at multiple current values, comparing them with expected values, and using the differences to determine calibration correction values. This feedback mechanism compensates for manufacturing variations and hysteresis, improving flow control accuracy while maintaining reasonable calibration efficiency
Solution Approach 2:
The patent performs preliminary calibration measurements at multiple current values (including minimum, intermediate, and maximum flow rates) before finalizing the calibration. By collecting and analyzing data in advance, the system determines accurate calibration correction values that compensate for variations and hysteresis
Data Source
AI summary
Problem: Provide a control calibration apparatus for a variable-capacity pump that can increase the flow control accuracy of the variable-capacity pump and a method thereof. Solution: The control calibration apparatus of the variable capacitance pump includes a controller that outputs a value of current for a flow rate command of the variable-capacity pump and a flow sensor that measures a flow rate of the variable-capacity pump. The controller has a function for obtaining a quadratic function formula that is a current-to-flow characteristic for flow control of the variable-capacity pump from a first value of current when the maximum flow rate of the variable-capacity pump is measured by the flow rate sensor, a second value of current when the minimum flow rate of the variable-capacity pump is measured by the flow rate sensor, and a fixed value of current corresponding to a fixed flow rate based on the specifications of the variable-capacity pump.