Peristaltic Pump Feedback Control for Flow Chemistry
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Solution Overview
Problem
Existing pumps in flow chemistry, particularly at the laboratory scale, face challenges with corrosive reagents and reagents containing high levels of particulates, as they often operate at low pressure and exhibit irregular flow rates, and struggle to maintain consistent output.
Innovation Solution
A peristaltic pump system with a motor-driven rotor, a pressure sensor, and a control unit that adjusts the rotor's speed based on detected pressure to maintain a constant output pressure, using a lookup table to determine the desired rotor position and interpolate between transfer function maps to compensate for non-linearities and tubing variations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If peristaltic pumps operate at constant speed, then the pump structure is simple, but the output flow rate becomes irregular
Solution Approach 1:
The patent implements a feedback control system where a pressure sensor monitors downstream pressure and feeds this information to a control unit. The control unit adjusts the motor speed in real-time based on pressure deviations, ensuring consistent flow rate despite variations in system resistance or tubing conditions.
Solution Approach 2:
The patent transitions from static constant-speed operation to dynamic speed adjustment. The motor speed is continuously varied according to pressure feedback, allowing the pump to adapt to changing system conditions and maintain reliable flow output.
2Ease of manufacture
If peristaltic pumps use standard tubing, then the pump is easy to manufacture, but it cannot handle corrosive reagents
Solution Approach 1:
The patent changes the material parameter of the tubing from standard materials to chemically resistant materials such as perfluoroelastomers or PTFE. This material substitution enables the pump to handle corrosive reagents including strong acids, bases, and organic solvents while maintaining ease of manufacture through available tubing options.
3Stress or pressure
If peristaltic pumps operate at high pressure, then the pump can deliver reagents to reaction chambers, but the flow rate becomes irregular
Solution Approach 1:
The patent uses pressure feedback from a downstream pressure sensor to continuously adjust motor speed. This closed-loop control compensates for pressure variations and maintains consistent flow rate even when operating at high pressures required for flow chemistry applications.
4Stress or pressure
If positive displacement pumps use non-return valves, then they can maintain pressure, but they cannot handle precipitates or air bubbles
Solution Approach 1:
The patent removes the non-return valves from the pump system entirely. The peristaltic pumping action inherently maintains pressure through continuous tubing compression, eliminating the need for valves that would be clogged by precipitates or air bubbles. This extraction of problematic components enables handling of challenging reagents.
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 achieves a consistent output flow within 5% variation of the desired rate, effectively handling corrosive and particulate-rich reagents by precisely regulating outlet pressure and reducing the need for mass flow sensing, thus providing stable and accurate reagent delivery.
Implementation Method 1
a pressure sensor monitoring the pressure of the pumped fluid downstream of the pump
Implementation Method 2
a peristaltic pump having a rotor driven by the motor; a pressure sensor monitoring the pressure of the pumped fluid downstream of the pump
Data Source
AI summary
Provided is a pump and a method of controlling a pump. The pump and method are particularly for use in dispensing reagents, for example in flow chemistry, and more particularly on a laboratory scale. The pump aims to provide a substantially constant output flow of fluid. The pump comprises: a motor; a peristaltic pump having a rotor driven by the motor; a pressure sensor monitoring the pressure of the pumped fluid downstream of the pump; and a control unit which controls the motor by adjusting the standard operating speed of the motor according to the pressure detected by the pressure sensor, such that the pump operates continuously at a rate set by an operator. Embodiments of the pump make use of lookup tables to determine a desired position of the pump rotor at each point in the cycle with the entry point into the lookup table being determined by the feedback from the pressure sensor. Long term changes in the performance of the pump can also be accounted for by changing the entry in the lookup table which is consulted.