Closed-loop Helium Circulation System for Actuation of a Continuously Operating Heart Catheter Pump

2017 ◽  
Vol 40 (6) ◽  
pp. 272-281
Author(s):  
Alen Karabegovic ◽  
Markus Hinteregger ◽  
Christoph Janeczek ◽  
Werner Mohl ◽  
Margit Gföhler
Keyword(s):  
Medical Devices ◽  
Closed Loop ◽  
Separate Flow ◽  
Stable Region ◽  
Circulation System ◽  
Continuous Systems ◽  
Total Size ◽  
Running Cost ◽  
Proper Operation ◽  
Noise Production

Background Currently available, pneumatic-based medical devices are operated using closed-loop pulsatile or open continuous systems. Medical devices utilizing gases with a low atomic number in a continuous closed loop stream have not been documented to date. This work presents the construction of a portable helium circulation addressing the need for actuating a novel, pneumatically operated catheter pump. The design of its control system puts emphasis on the performance, safety and low running cost of the catheter pump. Methods and results Static and dynamic characteristics of individual elements in the circulation are analyzed to ensure a proper operation of the system. The pneumatic circulation maximizes the working range of the drive unit inside the catheter pump while reducing the total size and noise production. Separate flow and pressure controllers position the turbine's working point into the stable region of the pressure creation element. A subsystem for rapid gas evacuation significantly decreases the duration of helium removal after a leak, reaching subatmospheric pressure in the intracorporeal catheter within several milliseconds. Conclusions The system presented in the study offers an easy control of helium mass flow while ensuring stable behavior of its internal components.

Stability boundary analysis of highly flexible aircraft with control saturation and structural flexibility

2020 ◽  
Vol 234 (6) ◽  
pp. 1195-1208
Author(s):  
Liang Xu ◽  
Yuping Lu ◽  
Boyi Chen ◽  
Haidong Shen ◽  
Zhen He
Keyword(s):  
Closed Loop ◽  
Stability Boundary ◽  
Open Loop ◽  
Loop System ◽  
Control Signal ◽  
Stable Region ◽  
Structural Flexibility ◽  
Flexible Aircraft ◽  
Control Saturation ◽  
Loop Stability

In this work, a method has been presented to analyze the influence of control saturation and structural flexibility on the stable radius of highly flexible aircraft. A dynamic model of aircraft is constructed followed by the analysis of kinetic characteristics. In this paper, the closed-loop stability boundary of highly flexible aircraft with open-loop instability is studied. The amplitude limit and bandwidth limit of the control signal are considered in the closed-loop stability boundary calculation. Our analysis shows that the boundary is related to the left eigenvector corresponding to the unstable poles and the amplitude constraint of the control signals. Stability of the boundary of feedback control system further reduces the limitation of the bandwidth of actuators. Focused on the phugoid instability of highly flexible aircraft, computational formulation of the closed-loop stable boundary is achieved. The Monte Carlo analysis has been employed to validate the stable region, under the LQR controller. Both the theory and simulations have nice correlations with each other which verify the stability of the closed-loop system, restricted by the open-loop system, and the influence of control signal bandwidth constraints.

scholarly journals Closed-loop verification of medical devices with model abstraction and refinement

2013 ◽  
Vol 16 (2) ◽  
pp. 191-213 ◽  
Author(s):  
Zhihao Jiang ◽  
Miroslav Pajic ◽  
Rajeev Alur ◽  
Rahul Mangharam
Keyword(s):  
Medical Devices ◽  
Closed Loop ◽  
Model Abstraction

scholarly journals Accuracy assessment methods for physiological model selection toward evaluation of closed-loop controlled medical devices

PLoS ONE ◽  
2021 ◽  
Vol 16 (4) ◽  
pp. e0251001
Author(s):  
Ramin Bighamian ◽  
Jin-Oh Hahn ◽  
George Kramer ◽  
Christopher Scully
Keyword(s):  
Medical Devices ◽  
Closed Loop ◽  
Physiological Model ◽  
Original Model ◽  
Control Algorithms ◽  
Refined Model ◽  
Predictive Capability ◽  
Physiological Models ◽  
Subject Specific ◽  
Leave One Out

Physiological closed-loop controlled (PCLC) medical devices are complex systems integrating one or more medical devices with a patient’s physiology through closed-loop control algorithms; introducing many failure modes and parameters that impact performance. These control algorithms should be tested through safety and efficacy trials to compare their performance to the standard of care and determine whether there is sufficient evidence of safety for their use in real care setting. With this aim, credible mathematical models have been constructed and used throughout the development and evaluation phases of a PCLC medical device to support the engineering design and improve safety aspects. Uncertainties about the fidelity of these models and ambiguities about the choice of measures for modeling performance need to be addressed before a reliable PCLC evaluation can be achieved. This research develops tools for evaluating the accuracy of physiological models and establishes fundamental measures for predictive capability assessment across different physiological models. As a case study, we built a refined physiological model of blood volume (BV) response by expanding an original model we developed in our prior work. Using experimental data collected from 16 sheep undergoing hemorrhage and fluid resuscitation, first, we compared the calibration performance of the two candidate physiological models, i.e., original and refined, using root-mean-squared error (RMSE), Akiake information criterion (AIC), and a new multi-dimensional approach utilizing normalized features extracted from the fitting error. Compared to the original model, the refined model demonstrated a significant improvement in calibration performance in terms of RMSE (9%, P = 0.03) and multi-dimensional measure (48%, P = 0.02), while a comparable AIC between the two models verified that the enhanced calibration performance in the refined model is not due to data over-fitting. Second, we compared the physiological predictive capability of the two models under three different scenarios: prediction of subject-specific steady-state BV response, subject-specific transient BV response to hemorrhage perturbation, and leave-one-out inter-subject BV response. Results indicated enhanced accuracy and predictive capability for the refined physiological model with significantly larger proportion of measurements that were within the prediction envelope in the transient and leave-one-out prediction scenarios (P < 0.02). All together, this study helps to identify and merge new methods for credibility assessment and physiological model selection, leading to a more efficient process for PCLC medical device evaluation.

Decentralized fuzzy C-means robust algorithm for continuous systems

2019 ◽  
Vol 92 (2) ◽  
pp. 222-228
Author(s):  
Tim Chen ◽  
J.C.Y. Chen
Keyword(s):  
Stability Criterion ◽  
Large Scale ◽  
Clustering Algorithm ◽  
Closed Loop ◽  
Linear Matrix ◽  
Model Description ◽  
Continuous Systems ◽  
Content Type ◽  
Fuzzy C Means ◽  
The Stability

Purpose This paper aims to address the robust controller design problem for a class of fuzzy C-means clustering algorithm that is robust against both the plant parameter perturbations and controller gain variations. Based on Takagi–Sugeno (T-S) fuzzy model description, the stability and control problems of nonlinear systems are studied. Design/methodology/approach A recently proposed integral inequality is selected based on the free-weight matrix, and the less conservative stability criterion is given in the form of linear matrix inequalities (LMIs). Findings Under the premise that the controller and the system share the same, the method does not require the number of membership functions and rules. Practical implications Furthermore, the modified controller in a large-scale nonlinear system is utilized as a stability criterion for a closed-loop T-S fuzzy system obtained by LMI, and is rearranged by a machine learning membership function. Originality/value The closed-loop controller criterion is derived by energy functions to guarantee the stability of systems. Finally, an example is given to demonstrate the results.

Dynamic Pricing Game Under Different Channel Power Structures in a Closed-Loop Supply Chain

2020 ◽  
Vol 30 (04) ◽  
pp. 2050052
Author(s):  
Junhai Ma ◽  
Fang Zhang ◽  
Hui Jiang
Keyword(s):  
Supply Chain ◽  
Supply Chains ◽  
Dynamic Pricing ◽  
Reference Price ◽  
Closed Loop ◽  
Stable Region ◽  
Power Structures ◽  
Closed Loop Supply Chain ◽  
Channel Power ◽  
Advantageous Position

The importance of closed-loop supply chains has been widely recognized both in academic communities and in industrial sectors. This paper starts from the traditional supply chains and the new self-supply chain of GREE to extract realistic problems, to mainly investigating two noncooperative dynamic pricing policies in a dual-channel closed-loop supply chain consisting of a manufacturer and a retailer. Then, it studies the influence of different channel power structures on dynamic decisions and their complexities. Furthermore, the reference price affects the purchase decisions of consumers. Therefore, the model takes into account the influence of reference price of the market demands. Results show that the manufacturer who opens up a direct channel can make a huge profit in the game. In the dynamic game evolution process, the game leader is in a more advantageous position when the system is in a stable region; once entering into the bifurcating region or chaotic region, the game follower needs to adjust his price to follow the leader’s decision in order to make a profit. In addition, the system’s stable region becomes smaller when the market demand becomes more sensitive to the difference between the reference price and the actual price. In this model, if the manufacturer acts as a leader, he is in a more advantageous position when the market is sensitive to channel competition in the stable stage while the result is opposite in the unstable stage.

The Effects of Closed-Loop Medical Devices on the Autonomy and Accountability of Persons and Systems

2016 ◽  
Vol 25 (4) ◽  
pp. 623-633 ◽  
Author(s):  
PHILIPP KELLMEYER ◽  
THOMAS COCHRANE ◽  
OLIVER MÜLLER ◽  
CHRISTINE MITCHELL ◽  
TONIO BALL ◽  
...  
Keyword(s):  
Medical Devices ◽  
Closed Loop ◽  
Personal Autonomy ◽  
Task Force ◽  
Legal Framework ◽  
Brain Computer Interfaces ◽  
Medical Systems ◽  
The Public ◽  
Computer Interfaces ◽  
Patient Advocacy Groups

Abstract:Closed-loop medical devices such as brain-computer interfaces are an emerging and rapidly advancing neurotechnology. The target patients for brain-computer interfaces (BCIs) are often severely paralyzed, and thus particularly vulnerable in terms of personal autonomy, decisionmaking capacity, and agency. Here we analyze the effects of closed-loop medical devices on the autonomy and accountability of both persons (as patients or research participants) and neurotechnological closed-loop medical systems. We show that although BCIs can strengthen patient autonomy by preserving or restoring communicative abilities and/or motor control, closed-loop devices may also create challenges for moral and legal accountability. We advocate the development of a comprehensive ethical and legal framework to address the challenges of emerging closed-loop neurotechnologies like BCIs and stress the centrality of informed consent and refusal as a means to foster accountability. We propose the creation of an international neuroethics task force with members from medical neuroscience, neuroengineering, computer science, medical law, and medical ethics, as well as representatives of patient advocacy groups and the public.

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