Dual Encoder Plunger Position Sensing for Injection Systems
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Solution Overview
Problem
Medical fluid injection systems face challenges in accurately monitoring the position of plungers within reservoirs, leading to potential errors in fluid delivery, which can result in unsafe operations and equipment damage due to uncertainty in injectable media quantities.
Innovation Solution
The implementation of a system that includes a plunger shaft, motor, and encoders (both single-turn and multi-turn) to determine the plunger's position within the reservoir, with a controller array comparing encoder outputs to ensure accuracy and disable the motor if discrepancies exceed a predetermined threshold, thereby preventing unintended operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single encoder is used to monitor motor position, then the device complexity is reduced, but the measurement precision and reliability of plunger position determination deteriorates
Solution Approach 1:
The system implements feedback by using multiple encoders (single-turn and multi-turn) to continuously monitor motor position and plunger location, comparing their outputs to detect discrepancies and provide corrective control signals to maintain accurate positioning
Solution Approach 2:
The system performs preliminary verification by comparing encoder outputs before executing injection operations, detecting potential position errors in advance and preventing unsafe operations from occurring
2Reliability
If redundant encoder systems are implemented to improve measurement precision, then the reliability of position sensing is enhanced, but the device complexity increases
Solution Approach 1:
The controller array continuously compares feedback from both single-turn and multi-turn encoders, using the disagreement signal to detect positioning errors and trigger corrective actions or safety shutdowns
Solution Approach 2:
The system monitors changes in encoder output parameters over time, detecting when position discrepancies exceed predetermined thresholds and responding by adjusting motor control or halting operation to maintain safety
3Reliability
If the system continuously monitors plunger position with high precision, then the safety of injection operations is improved, but the loss of time for position verification increases
Solution Approach 1:
The dual-encoder system performs continuous position verification throughout the entire injection process rather than discrete checks, eliminating idle verification time and maintaining constant safety monitoring without interrupting the injection workflow
Data Source
AI summary
Injection systems can include a reservoir, a plunger mounted within the reservoir, and a plunger shaft including engaging the plunger within the reservoir. A motor can be coupled to the plunger shaft and can be configured to cause the plunger and plunger shaft to move within the reservoir. Systems can include a first encoder and a second encoder and a controller array in communication with the first and second encoders. The controller array can receive outputs from the first and second encoders representative of the position of the motor. Outputs from one encoder can be used to confirm the accuracy of the output of the other encoder. The controller can compare the outputs from the encoders, and, if the difference in the outputs is greater than a predetermined amount, disable operation of the motor.