Sensorless Occlusion Detection in Fluid Delivery Pumps
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Solution Overview
Problem
Existing fluid delivery devices, such as insulin pumps, face challenges in accurately and efficiently delivering medication due to variations in reservoir friction, occlusion detection complexity, and energy inefficiency, which can lead to unreliable and costly designs.
Innovation Solution
Implementing a processor-controlled method using motor position sensors to detect plunger position and occlusions, compensating for friction variations, and optimizing motor control for pulsatile operations with active braking, eliminating the need for additional strain sensors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If strain sensors are added to detect occlusions and friction, then occlusion detection accuracy improves, but device complexity and cost increase
Solution Approach 1:
The motor serves dual purposes: delivering fluid and detecting occlusions. The motor's own performance characteristics (current, speed, torque) are used as indicators of occlusion conditions, eliminating the need for separate strain sensors. The system monitors the motor's electrical parameters during operation to infer occlusion states.
Solution Approach 2:
Electrical sensing replaces mechanical strain sensing. Instead of using strain sensors to mechanically detect forces, the system uses electrical measurements (current, voltage, power) from the motor control circuitry to detect mechanical occlusion conditions. This substitution reduces hardware complexity while maintaining detection capability.
2Manufacturing precision
If friction compensation mechanisms are implemented, then delivery accuracy improves, but device complexity increases
Solution Approach 1:
The system continuously monitors motor electrical parameters and uses this feedback to compensate for friction variations. By measuring the motor's actual performance and comparing it to expected values, the control system can infer friction conditions and adjust delivery parameters accordingly, achieving accurate compensation without additional sensors.
Solution Approach 2:
The motor control system performs multiple functions: fluid delivery, occlusion detection, and friction compensation. The same electrical measurements used for basic motor control are also utilized to detect friction variations and compensate for them, eliminating the need for separate friction sensing mechanisms.
3Reliability
If continuous monitoring of delivery rate is performed, then occlusion detection reliability improves, but energy consumption increases
Solution Approach 1:
The motor control system operates continuously during fluid delivery, maintaining constant monitoring of electrical parameters. This continuous operation allows for real-time occlusion detection without requiring separate monitoring cycles, as the useful action of motor control inherently provides the monitoring function.
Solution Approach 2:
The motor control circuitry serves dual purposes by simultaneously controlling motor operation and monitoring for occlusions. The same electrical measurements taken for basic motor function control are also used for occlusion detection, eliminating the need for additional power-consuming monitoring systems.
Data Source
AI summary
A processor-implemented method comprises obtaining a baseline coefficient of variation of delivery rate of a fluid delivery device; obtaining an instantaneous delivery rate of the fluid delivery device during a motor stroke, the motor stroke including a plurality of motor steps; determining a current minimum delivery rate of the fluid delivery device based on the instantaneous delivery rate and a previous minimum delivery rate of the fluid delivery device; storing the current minimum delivery rate in a buffer; determining a current coefficient of variation of delivery rate of the fluid delivery device based on data in the buffer; and determining whether an occlusion has occurred based on one or more threshold values and a rate of change of the current coefficient of variation of delivery rate with respect to the baseline coefficient of variation of delivery rate.