With a good balance between power transfer distance and efficiency, wireless power transfer (WPT) using magnetic resonant coupling is preferred in many applications. Generally, WPT systems are ...desired to provide constant output voltage with the highest possible efficiency as power supplies. However, the highest efficiency is not achieved by the reported closed-loop WPT systems that maintain constant output voltage against coupling and load variations. In this paper, an efficiency evaluation method is put forward to evaluate the closed-loop control schemes. Furthermore, a maximum efficiency point tracking control scheme is proposed to maximize the system efficiency while regulating the output voltage. This control scheme is unique and prominent in that it fixes the operating frequency at the receiving-side resonant frequency and converts both the input voltage and the load resistance at the same time. Thus, the maximum efficiency point on the constant output voltage trajectory can be tracked dynamically. Therefore the system's output voltage can be maintained constant and its efficiency is always the highest. The experimental results show that the maximum efficiency point is tracked and a very high overall efficiency is achieved over wide ranges of coupling coefficient and load resistance.
A closed‐loop system that can mini‐invasively track blood glucose and intelligently treat diabetes is in great demand for modern medicine, yet it remains challenging to realize. Microneedles ...technologies have recently emerged as powerful tools for transdermal applications with inherent painlessness and biosafety. In this work, for the first time to the authors' knowledge, a fully integrated wearable closed‐loop system (IWCS) based on mini‐invasive microneedle platform is developed for in situ diabetic sensing and treatment. The IWCS consists of three connected modules: 1) a mesoporous microneedle‐reverse iontophoretic glucose sensor; 2) a flexible printed circuit board as integrated and control; and 3) a microneedle‐iontophoretic insulin delivery component. As the key component, mesoporous microneedles enable the painless penetration of stratum corneum, implementing subcutaneous substance exchange. The coupling with iontophoresis significantly enhances glucose extraction and insulin delivery and enables electrical control. This IWCS is demonstrated to accurately monitor glucose fluctuations, and responsively deliver insulin to regulate hyperglycemia in diabetic rat model. The painless microneedles and wearable design endows this IWCS as a highly promising platform to improve the therapies of diabetic patients.
A fully integrated wearable closed‐loop system (IWCS) based on microneedle‐iontophoresis platform is developed for in situ diabetic sensing and treatment. This IWCS is demonstrated to accurately monitor glucose fluctuations and responsively deliver insulin to regulate hyperglycemia. The painless microneedles and wearable design endow this IWCS as a highly promising platform to improve the therapies of diabetic patients.
Aims
To explore parents’ experiences of using remote monitoring technology when caring for a very young child with type 1 diabetes during a clinical trial.
Methods
Interviews were conducted with ...parents of 30 children (aged 1–7 years) participating in a trial (the KidsAP02 study) comparing hybrid closed‐loop insulin delivery with sensor‐augmented pump therapy. In both arms, parents had access to remote monitoring technology. Data analysis focused on identification of descriptive themes.
Results
Remote monitoring technology gave parents improved access to data which helped them pre‐empt and manage glucose excursions. Parents observed how, when children were in their own care, they could be more absent while present, as their attention could shift to non‐diabetes‐related activities. Conversely, when children were others’ care, remote monitoring enabled parents to be present while absent, by facilitating oversight and collaboration with caregivers. Parents described how remote monitoring made them feel more confident allowing others to care for their children. Parents’ confidence increased when using a hybrid closed‐loop system, as less work was required to keep glucose in range. Benefits to children were also highlighted, including being able to play and sleep uninterrupted and attend parties and sleepovers without their parents. While most parents welcomed the increased sense of control remote monitoring offered, some noted downsides, such as lack of respite from caregiving responsibilities.
Conclusions
Remote monitoring can offer manifold benefits to both parents and very young children with type 1 diabetes. Some parents, however, may profit from opportunities to take ‘time out’.
Aim
Automated insulin delivery systems have improved glycaemic control in people with type 1 diabetes mellitus. The analysis investigated predictors of improved sensor glucose time‐in‐range (TIR; ...70‐180 mg/dl) based on real‐world use of the MiniMed 780G advanced hybrid closed‐loop (AHCL) system.
Methods
Data uploaded by MiniMed 780G system users from August 2020‐July 2021 were analysed using univariate and multivariable models to identify baseline, demographic and system use characteristics associated with TIR after AHCL initiation (post‐AHCL). System settings associated with improved TIR post‐AHCL were identified and their impact on time below range (TBR, <70 mg/dl) post‐AHCL was explored.
Results
In total, 12 870 users were included, of which 2977 had baseline sensor glucose data. Baseline TIR and time in AHCL (defined as the percentage of time the system was in Auto‐mode) were positively associated with TIR post‐AHCL with larger values predicting greater mean TIR post‐AHCL. Characteristics inversely associated with TIR post‐AHCL included the percentage of daily basal insulin dose, daily autocorrection dose, number of daily AHCL exits triggered by the system and number of daily alarms, wherein larger values of these characteristics predicted lower mean TIR post‐AHCL. System settings that predicted the largest mean TIR post‐AHCL were active insulin time of 2 h and glucose target of 100 mg/dl. Active insulin time was not associated with TBR post‐AHCL.
Conclusion
Modifiable factors, including optimized pump settings, can allow users to achieve glycaemic targets with >80% TIR. The findings from this analysis will potentially guide the optimal use of the MiniMed 780G system and facilitate meaningful improvements in safe glycaemic control.
This article presents a novel degradation modeling and prognostic method for a class of closed-loop feedback systems with degrading actuators. Toward this end, we first present a degradation modeling ...framework by integrating the stochastic degradation process model of the actuator and the state transition model of the system. This takes into consideration the mutual effects between the component-level degradation and system-level state. Then, the particle filter algorithm is utilized to jointly estimate the hidden degradation state of the actuator and the system state through indirect observations. Further, a time-varying nonlinear diffusion process equipped with two-stage parameters updating procedure is used to learn the evolving progression of the hidden degradation state. As such, a residual-threshold-based remaining useful life (RUL) prediction method is presented by simulating future system states and degradation trajectories based on the learned degradation process. As the application of the predicted RUL, a fault tolerant control method is presented by adjusting the controller parameter so as to extend the life of the system. Finally, a simulation study is conducted using a closed-loop control system in an inertial platform to verify the proposed method. The results indicate that the proposed method can reduce prognosis error, improve robustness, and extend the lifetime of the system.
•system identification method based on hysteresis loop bias relay feedback without using excitation is designed•hysteresis loop bias relay instead of a controller is proposed•a parameter scheme for ...the hysteresis loop bias relay to guide the selection of parameters is proposed
This paper proposes a closed-loop system identification method based on hysteresis loop bias relay feedback without using excitation. The method utilizes hysteresis loop bias relay instead of a controller to ensure the informativity of data without external excitation and with only noisy feedback. Additionally, this paper proposes a parameter scheme for the hysteresis loop bias relay to guide the selection of parameters more rationally, thus improving the accuracy of the identification model. Compared to recently proposed switching controller methods, the advantage of this method lies in the fact that it requires fewer samples and shortens data collection time. The method's effectiveness is verified through simulation comparisons with typical methods.
An artificial “closed‐loop” system that mimics the glucose‐responsive insulin secretion of pancreas β‐cells can potentially improve the treatment efficacy for diabetes. Herein, a lipid bilayer‐coated ...polymeric nanoparticle (NP) with “core–shell” structure is designed. As far as it is known, it is the first and only intravenous nanoplatform utilizing enzymatic‐oxidation scheme to achieve glucose‐responsive insulin delivery so far. Ethoxy acetal–derivatized dextran nanoparticles (Ace‐DEX NPs) are constructed as “inner core” loaded with insulin, and coloading glucose oxidase (GOx) and catalase (CAT) endow the “inner core” excellent glucose‐sensitive ability. Red blood cell membrane (RBCm)‐derived coating is adopted as “outer shell.” It collectively provides a closed microenvironment for GOx‐based enzymatic‐oxidation scheme and camouflages it from elimination. Above all, the anchored glucose transporters (GLUTs) on the “outer shell” are able to sense blood glucose levels and facilitate the transport of outer blood glucose getting inside. Under a hyperglycemic condition, the internalized glucose is catalytically converted into gluconic acid with the aid of the GOx and subsequently triggers acid degradation of the “inner core” to secrete insulin. By governing the blood glucose levels on an automatic and continuous basis, the RBCm‐Ace‐DEX NPs can effectively respond to hyperglycemia and turn to resting conditions under normoglycemia.
Ethoxy acetal derivatized dextran nanoparticles (Ace‐DEX NPs) are constructed as “inner core” and red blood cell membrane (RBCm)‐derived coating is adopted as “outer shell”. This glucose‐responsive nanoplatform can steadily circulate in the blood at normalglycemia. While under hyperglycemic condition, the glucose internalized by the anchored GLUTs is catalytically converted into gluconic acid with the aid of GOx and CAT and subsequently triggers acid degradation of RBCm‐Ace‐DEX NPs to secrete insulin.
Aim
To evaluate the real‐world performance of the MiniMed 670G system in Europe, in individuals with diabetes.
Materials and Methods
Data uploaded from October 2018 to July 2020 by individuals living ...in Europe were aggregated and retrospectively analysed. The mean glucose management indicator (GMI), percentage of time spent within (TIR), below (TBR) and above (TAR) glycaemic ranges, system use and insulin consumed in users with 10 or more days of sensor glucose data after initial Auto Mode start were determined. Another analysis based on suboptimally (GMI > 8.0%) and well‐controlled (GMI < 7.0%) glycaemia pre‐Auto Mode initiation was also performed.
Results
Users (N = 14 899) spent a mean of 81.4% of the time in Auto Mode and achieved a mean GMI of 7.0% ± 0.4%, TIR of 72.0% ± 9.7%, TBR less than 3.9 mmol/L of 2.4% ± 2.1% and TAR more than 10 mmol/L of 25.7% ± 10%, after initiating Auto Mode. When compared with pre‐Auto Mode initiation, GMI was reduced by 0.3% ± 0.4% and TIR increased by 9.6% ± 9.9% (P < .0001 for both). Significantly improved glycaemic control was observed irrespective of pre‐Auto Mode GMI levels of less than 7.0% or of more than 8.0%. While the total daily dose of insulin increased for both groups, a greater increase was observed in the latter, an increase primarily due to increased basal insulin delivery. By contrast, basal insulin decreased slightly in well‐controlled users.
Conclusions
Most MiniMed 670G system users in Europe achieved TIR more than 70% and GMI less than 7% while minimizing hypoglycaemia, in a real‐world environment. These international consensus‐met outcomes were enabled by automated insulin delivery meeting real‐time insulin requirements adapted to each individual user.
Advanced hybrid closed-loop (AHCL) systems represent the next step of automation intended to maximize normoglycemia in people with type 1 diabetes (T1D). In the AHCL MiniMed 780G system, different ...algorithm glucose targets for insulin infusion are available and autocorrection boluses are delivered. The aim was to prospectively evaluate the impact of the implementation of this AHCL system in a clinical setting.
T1D subjects using a sensor-augmented pump with predictive low-glucose suspend (SAP-PLGS) were upgraded to AHCL. Baseline, every 3 days, 2-week and 1-month sensor and pump data were downloaded. Glucose target was set to 100 mg/dL and active insulin time to 2 h for all the subjects. Time in different glucose ranges was compared.
Fifty-two T1D subjects were included (age: 43 ± 12 years, 73% females, diabetes duration: 27 ± 11 years, HbA1c: 7.2% ± 0.9%, time in SAP-PLGS: 5 ± 2 years). Time in range (TIR) 70-180 mg/dL increased from 67.3% ± 13.6% at baseline to 79.6% ± 7.9% at 1 month (
= 0.001). Time in hyperglycemia >180 and >250 mg/dL decreased from 29.4% ± 15.1% to 17.3% ± 8.6% and from 6.9% ± 7.8% to 2.5% ± 2.4%, respectively (
= 0.001). No differences in time in hypoglycemia <70 or <54 mg/dL were found. Time in Auto Mode was 97% ± 4%, and autocorrection insulin was 31% ± 14% of bolus insulin. Four hours postprandial glucose was improved from 162 ± 26 mg/dL at baseline to 142 ± 16 mg/dL at 1 month (
= 0.001). No severe hypoglycemia or diabetic ketoacidosis episodes occurred.
AHCL systems allow well-controlled T1D patients to rapidly increase their TIR. The most aggressive settings allow optimal outcomes in TIR, without increasing hypoglycemia frequency.
This study is concerned with the event-based security control problem for a class of discrete-time stochastic systems with multiplicative noises subject to both randomly occurring denial-of-service ...(DoS) attacks and randomly occurring deception attacks. An event-triggered mechanism is adopted with hope to reduce the communication burden, where the measurement signal is transmitted only when a certain triggering condition is violated. A novel attack model is proposed to reflect the randomly occurring behaviours of the DoS attacks as well as the deception attacks within a unified framework via two sets of Bernoulli distributed white sequences with known conditional probabilities. A new concept of mean-square security domain is put forward to quantify the security degree. The authors aim to design an output feedback controller such that the closed-loop system achieves the desired security. By using the stochastic analysis techniques, some sufficient conditions are established to guarantee the desired security requirement and the control gain is obtained by solving some linear matrix inequalities with non-linear constraints. A simulation example is utilised to illustrate the usefulness of the proposed controller design scheme.
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