Piecewise Glucose Cost Control in Insulin Delivery Devices
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Solution Overview
Problem
Conventional insulin delivery devices struggle with persistent positive glucose excursions due to conservative cost functions that fail to aggressively address low-level glucose deviations from the target level, leading to negative health effects.
Innovation Solution
The implementation of a piecewise cost function that dynamically adjusts based on glucose excursion persistence and magnitude, combining linear and quadratic functions to more aggressively penalize low-level deviations, using weights derived from historical data to enhance the control loop's responsiveness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conservative cost function is used to balance penalties for insulin delivery and glucose excursions, then the system delivers smaller insulin doses more frequently, but persistent positive glucose excursions occur at low levels
Solution Approach 1:
The patent changes the parameter of the cost function by introducing a piecewise definition with different penalty weights for different glucose excursion ranges. Specifically, it applies a higher penalty weight (e.g., 4.0) for excursions within a low-level range (e.g., 70-180 mg/dL) compared to standard excursions, thereby altering the system's response characteristics to address persistent low-level hyperglycemia while maintaining overall glucose control reliability
Solution Approach 2:
The cost function is segmented into multiple ranges with different penalty applications. The patent divides the glucose excursion problem into segments: a first range for low-level excursions (70-180 mg/dL) with enhanced penalties, and a second range for higher excursions with standard penalties. This segmentation allows the system to address different aspects of glucose control with appropriate specificity, preventing persistent low-level excursions without over-correcting for higher excursions
2Object-affected harmful factors
If the cost function aggressively penalizes glucose excursions, then persistent positive glucose excursions are reduced, but larger insulin deliveries may be required more frequently
Solution Approach 1:
The patent modifies the penalty parameter selectively by applying different weightings to different excursion ranges. The enhanced penalty weight (e.g., 4.0) is applied only to low-level excursions (70-180 mg/dL), while standard weighting is applied to higher excursions. This selective parameter change allows aggressive correction of persistent low-level excursions without proportionally increasing overall insulin delivery requirements
3Productivity
If a piecewise cost function with enhanced penalties is applied to low-level glucose excursions, then the control loop becomes more responsive to maintain target levels, but the device complexity increases
Solution Approach 1:
The patent segments the cost function into manageable ranges with distinct penalty applications. By dividing the glucose excursion space into a first range (70-180 mg/dL) with enhanced penalties and a second range with standard penalties, the system achieves enhanced responsiveness for the critical low-level excursions while keeping the overall function structure organized and computationally manageable through clear range-based segmentation
Data Source
AI summary
The exemplary embodiments may modify a glucose cost component of the cost function of the control loop of an insulin delivery device to compensate for persistent positive low level glucose excursions relative to a target glucose level. The exemplary embodiments may enable use of different glucose cost component functions for different glucose levels of the user. These glucose cost component functions may be employed in piecewise fashion with a different piece being applied for each respective range of glucose level values for the user. The final glucose cost function for calculating the glucose cost component may be a weighted combination of a piecewise glucose cost function and a weighted standard cost function (such as a quadratic function). The weights may reflect the magnitude and/or persistence of glucose excursions relative to a target glucose level.