Centrifugal Pump Pressure Control With Square-Root Linearization
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Solution Overview
Problem
Centrifugal pumps exhibit non-linear behavior, making it difficult for standard controllers like PID to maintain consistent dynamic responsiveness across all operating points, especially when integrated into hydraulic piping networks with changing loads, such as heating or cooling systems, where hydraulic resistance varies over time.
Innovation Solution
The method involves using a hydraulic controller and a speed controller with a root calculation unit to linearize the control based solely on the pump curve, eliminating the need for system characteristic knowledge and geodetic height, by using the square root of the manipulated variable to determine the speed value, thereby compensating for the volume flow-independent part of the pump characteristic, resulting in consistent dynamic behavior and reduced overshooting.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a standard PID controller is used to regulate centrifugal pump pressure, then the controller structure is simple and easy to implement, but the dynamic responsiveness varies significantly across different operating points due to nonlinear pump behavior
Solution Approach 1:
The patent transforms the manipulated variable through a square root function to linearize the control characteristic. This parameter transformation compensates for the nonlinear behavior of the centrifugal pump, enabling consistent dynamic responsiveness across all operating points while maintaining a simple PID controller structure.
2Reliability
If affinity laws are used to compensate for nonlinear behavior, then dynamic responsiveness improves, but the controller requires adaptation for system characteristic curves and geodetic height calculations
Solution Approach 1:
The patent extracts and compensates only for the volume flow-independent part of the pump characteristic (the a·n² term) through square root transformation of the manipulated variable. This selective compensation eliminates the need to determine system characteristic curves or calculate geodetic heights, significantly reducing controller complexity while maintaining consistent dynamic behavior.
3Device complexity
If conventional hydraulic control is used without linearization, then the control system is simple, but pressure or delivery head exhibits significant overshoot during transient operations
Solution Approach 1:
The patent applies square root transformation to the manipulated variable to linearize the hydraulic control. This parameter change compensates for the nonlinear relationship between pump speed and delivery head, significantly reducing overshoot during transient operations while maintaining a relatively simple control structure.
Data Source
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AI summary
The invention relates to a method and control electronics for controlling the pressure (p_Act) or the delivery head (H) of a centrifugal pump (2) using a hydraulic controller (4), to which the control deviation of an actual value (p_Act) from a setpoint (p_ref) is supplied and which outputs a manipulated variable (X), and a speed controller (6) downstream of the hydraulic controller (4), which outputs a speed value (n) for setting the centrifugal pump (2) as a function of the manipulated variable (X), wherein the square root of the manipulated variable (X) is calculated and the speed controller (6) determines the speed value (n) as a function of the square root of the manipulated variable (X). The invention further relates to a centrifugal pump comprising such control electronics.