Pump Shutoff Research Articles

Automatic Artificial Pancreas Systems Using an Intelligent Multiple-Model PID Strategy.

In this paper, an individualized intelligent multiple-model technique is proposed to design automatic artificial pancreas (AP) systems for the glycemic regulation of type 1 diabetic patients. At first, using the multiple-model concept, the insulin-glucose regulatory system is mathematically identified by constructing some local models. In this step, trade-offs between the number of local models and the complexity of the overall closed-loop system are made by defining and solving a bi-objective optimization problem. Then, optimal AP systems are designed by tuning a bank of proportional-integral-derivative (PID) controllers via the genetic algorithm (GA). A fuzzy gain scheduling strategy is employed to determine the participation percentages of the PID controllers in the control action. Finally, two safety mechanisms, called insulin on board (IOB) constraint and pump shut-off, are installed in the AP systems to enhance their performance. To assess the proposed AP systems, in silico experiments are performed on virtual patients of the UVA/Padova metabolic simulator. The obtained results reveal that the proposed intelligent multiple-model methodology leads to AP systems with limited hyperglycemia and no severe hypoglycemia.

Transient simulations in water distribution networks: TSNet python package

Modeling transient flow conditions in water distribution networks (WDNs) has shown increasing usability for various applications, including burst and leak detection, sensor placement, model calibration, and risk assessment. To facilitate the integration of transient modeling in these simulation-based applications, this work contributes a new open source Python package for Transient Simulations in water Networks (TSNet). TSNet adopts the Method of Characteristics (MOC) for solving the system of partial differential equations governing the unsteady hydraulics. It allows users to simulate various conditions including operational changes in valves and pumps, as well as background leaks and pipe bursts. In this paper, the TSNet modeling framework is presented and a case study is used to showcase its capabilities of simulating WDN responses to valve closure, pump shut-off, leaks, and bursts with and without a surge protection tank. Results show that valve closure, pump shut-off, and pipe burst can generate significant transients in the WDN, while background leaks can help damp the transients to some extent.

A Comparative Study on Centrifugal Pump Designs and Two-Phase Flow Characteristic under Inlet Gas Entrainment Conditions

Capability for handling entrained gas is an important design consideration for centrifugal pumps used in petroleum, chemistry, nuclear applications. An experimental evaluation on their two phase performance is presented for two centrifugal pumps working under air-water mixture fluid conditions. The geometries of the two pumps are designed for the same flow rate and shut off head coefficient with the same impeller rotational speed. Overal pump performance and unsteady pressure pulsation information are obtained at different rotational speeds combined with various inlet air void fractions (α0) up to pump stop condition. As seen from the test results, pump 2 is able to deliver up to 10% two-phase mixtures before pump shut-off, whereas pump 1 is limited to 8%. In order to understand the physics of this flow phenomenon, a full three-dimensional unsteady Reynolds Average Navier-Stokes (3D-URANS) calculation using the Euler–Euler inhomogeneous method are carried out to study the two phase flow characteristics of the model pump after corresponding experimental verification. The internal flow characteristics inside the impeller and volute are physically described using the obtained air distribution, velocity streamline, vortex pattern and pressure pulsation results under different flow rates and inlet void fractions. Pump performances would deteriorate during pumping two-phase mixture fluid compared with single flow conditions due to the phase separating effect. Some physical explanation about performance improvements on handing maximum acceptable inlet two phase void fractions capability of centrifugal pumps are given.

Optimization of Pump Start-Up Depth in Drainage Pumping Station Based on SWMM and PSO

The pumps in multistage drainage pumping stations are often subject to frequent start-up and shutoffs during operation because of unreasonable start-up depths of the pumps; this will reduce the service lives of the pumps. To solve this problem, an optimization method for minimizing pump start-up and shutoff times is proposed. In this method, the operation of pumps in pumping station was optimized by constructing a mathematical optimization model. The storm water management model (SWMM) and particle swarm optimization (PSO) method were used to solve the problem and the optimal start-up depth of each pump is obtained. Nine pumping stations in Beijing were selected as a case study and this method was applied for multistage pumping station optimization and single pumping station optimization in the case study. Results from the case study demonstrate that the multistage pumping station optimization acquired a small number of pump start-up/shutoff times, which were from 8 to 114 in different rainfall scenarios. Compared with the multistage pumping station optimization, the single pumping station optimization had a bigger number of pump start-up/shutoff times, which were from 1 to 133 times, and the pump operating time was also longer, from 72 min to 7542 min. Therefore, the multistage pumping station optimization method was more suitable to reduce the frequency of pump start-up/shutoffs.

Impact of pipes networks simplification on water hammer phenomenon

Simplification of water supply networks is an indispensible design step to make the original network easier to be analysed. The impact of networks’ simplification on water hammer phenomenon is investigated. This study uses two loops network with different diameters, thicknesses, and roughness coefficients. The network is fed from a boundary head reservoir and loaded by either distributed or concentrated boundary water demands. According to both hydraulic and hydraulic plus water quality equivalence, three simplification levels are performed. The effect of demands’ concentration on the transient flow is checked. The transient flow is initialized by either concentrated or distributed boundary demands which are suddenly shut-off or released. WHAMO software is used for simulation. All scenarios showed that both hydraulic equivalence and demands’ concentration simplifications increase the transient pressure and flow rate. However, hydraulic plus water quality equivalence simplification produces an adverse effect. Therefore, simplifications of the networks should be done carefully. Also, it was found that pump shut-off gives the same trend of valve shut-off or release.

Artificial Pancreas: Model Predictive Control Design from Clinical Experience

The objective of this research is to develop a new artificial pancreas that takes into account the experience accumulated during more than 5000 h of closed-loop control in several clinical research centers. The main objective is to reduce the mean glucose value without exacerbating hypo phenomena. Controller design and in silico testing were performed on a new virtual population of the University of Virginia/Padova simulator. A new sensor model was developed based on the Comparison of Two Artificial Pancreas Systems for Closed-Loop Blood Glucose Control versus Open-Loop Control in Patients with Type 1 Diabetes trial AP@home data. The Kalman filter incorporated in the controller has been tuned using plasma and pump insulin as well as plasma and continuous glucose monitoring measures collected in clinical research centers. New constraints describing clinical knowledge not incorporated in the simulator but very critical in real patients (e.g., pump shutoff) have been introduced. The proposed model predictive control (MPC) is characterized by a low computational burden and memory requirements, and it is ready for an embedded implementation. The new MPC was tested with an intensive simulation study on the University of Virginia/Padova simulator equipped with a new virtual population. It was also used in some preliminary outpatient pilot trials. The obtained results are very promising in terms of mean glucose and number of patients in the critical zone of the control variability grid analysis. The proposed MPC improves on the performance of a previous controller already tested in several experiments in the AP@home and JDRF projects. This algorithm complemented with a safety supervision module is a significant step toward deploying artificial pancreases into outpatient environments for extended periods of time.

Inpatient Studies of a Kalman-Filter-Based Predictive Pump Shutoff Algorithm

An insulin pump shutoff system can prevent nocturnal hypoglycemia and is a first step on the pathway toward a closed-loop artificial pancreas. In previous pump shutoff studies using a voting algorithm and a 1 min continuous glucose monitor (CGM), 80% of induced hypoglycemic events were prevented. The pump shutoff algorithm used in previous studies was revised to a single Kalman filter to reduce complexity, incorporate CGMs with different sample times, handle sensor signal dropouts, and enforce safety constraints on the allowable pump shutoff time. Retrospective testing of the new algorithm on previous clinical data sets indicated that, for the four cases where the previous algorithm failed (minimum reference glucose less than 60 mg/dl), the mean suspension start time was 30 min earlier than the previous algorithm. Inpatient studies of the new algorithm have been conducted on 16 subjects. The algorithm prevented hypoglycemia in 73% of subjects. Suspension-induced hyperglycemia is not assessed, because this study forced excessive basal insulin infusion rates. The new algorithm functioned well and is flexible enough to handle variable sensor sample times and sensor dropouts. It also provides a framework for handling sensor signal attenuations, which can be challenging, particularly when they occur overnight.

Closed-loop insulin delivery: from bench to clinical practice.

Automated closed-loop insulin delivery, also referred to as the 'artificial pancreas', has been an important but elusive goal of diabetes treatment for many decades. Research milestones include the conception of continuous glucose monitoring in the early 1960s, followed by the production of the first commercial hospital-based artificial pancreas in the late 1970s that combined intravenous glucose sensing and insulin delivery. In the past 10 years, research into the artificial pancreas has gained substantial momentum and focused on the subcutaneous route for glucose measurement and insulin delivery, which reflects technological advances in interstitial glucose monitoring and the increasing use of the continuous subcutaneous insulin infusion. This Review discusses the design of an artificial pancreas, its components and clinical results, as well as the advantages and disadvantages of different types of automated closed-loop systems and potential future advances. The introduction of the artificial pancreas into clinical practice will probably occur gradually, starting with simpler approaches, such as overnight control of blood glucose concentration and temporary pump shut-off, that are adapted to more complex situations, such as glycemic control during meals and exercise.

Ant-colony-based simulation–optimization modeling for the design of a forced water pipeline system considering the effects of dynamic pressures

Valve and pump shut-off in water pipeline systems lead to transient flow. This flow is a complex phenomenon and is potentially a very serious problem causing extra dynamic pressure in the system. Within the last few decades, the evolutionary and meta-heuristic algorithms, such as genetic algorithms, simulated annealing. More recently, however, ant-colony optimization algorithms have received considerable attention. In this paper the procedure and application of the ant-colony optimization algorithm to the design of a water supply pipeline system, considering dynamic pressures arising from valve closure, is presented. A simulation–optimization interaction loop (SOIL) is defined that cycles between the steady-state and transient flow modules to describe the hydraulics of the pipeline and ant colony optimization algorithm. A hydraulic simulation module is coupled with the ant colony optimization algorithm to form an efficient and powerful software program which locates the pumping stations at any possible or predefined locations while optimizing their specifications, along with pipe diameters, at each decision point. The model may equally regard or disregard the dynamic pressures. Two examples are provided to illustrate the proposed methodology which is limited to the solution of any gravity and/or forced water supply pipeline which is typical for water supply systems.

Preventing Hypoglycemia Using Predictive Alarm Algorithms and Insulin Pump Suspension

Nocturnal hypoglycemia is a significant problem. From 50% to 75% of hypoglycemia seizures occur at night. Despite the development of real-time glucose sensors (real-time continuous glucose monitor [CGM]) with hypoglycemic alarms, many patients sleep through these alarms. The goal of this pilot study was to assess the feasibility using a real-time CGM to discontinue insulin pump therapy when hypoglycemia was predicted. Twenty-two subjects with type 1 diabetes had two daytime admissions to a clinical research center. On the first admission their basal insulin was increased until their blood glucose level was <60 mg/dL. On the second admission hypoglycemic prediction algorithms were tested to determine if hypoglycemia was prevented by a 90-min pump shutoff and to determine if the pump shutoff resulted in rebound hyperglycemia. Using a statistical prediction algorithm with an 80 mg/dL threshold and a 30-min projection horizon, hypoglycemia was prevented 60% of the time. Using a linear prediction algorithm with an 80 mg/dL threshold and a 45-min prediction horizon, hypoglycemia was prevented 80% of the time. There was no rebound hyperglycemia following pump suspension. Further development of algorithms is needed to prevent all episodes of hypoglycemia from occurring.

An Air Embolism Detection Device for Use with a Non-Occlusive Arterial Pumphead

(J. Extra-Corpor. Technol. 19[4]: p. 406-407 Winter 1988). A clinical evaluation of an air-bubble detector system used in conjunction with a non-occlusive pumphead is described in this report. The detector system was originally designed for occlusive roller pumpheads. A non-occlusive pump system can now be integrated with an existing rollerhead pump setup to accomplish the same desired effect, that is, automatic shutoff of the non-occlusive arterial pumphead if air is detected. The system is designed to produce an audible alarm when a bolus of air enters the bypass circuit. This system can be operated in a manual or automatic mode for arterial pump shutoff. This system has been judged effective in our clinical setting.

Computer Control of Irrigation for Electrical Load Management

ABSTRACT MANY electrical power suppliers have initiated load shedding programs to reduce the operating load on the transmission and delivery system during periods of peak demand. Typically, these programs result in irrigation pump shutoff on a predetermined rotational schedule. A computerized radio telemetry system was developed which automatically determines the soil water status of the field served by each pump based on climatic data, sets priorities for load interruption based on soil water status, and stops pumps upon receipt of a signal from the power supplier. The system also provides for remote control of pumps and monitoring of their operational status.

Operating Options for Pumped Equalizing Storage

There are two basic ways in which equalizing storage can be used by the operator of a service district with a pumped supply. Either the storage is unregulated and “floats” on the system for an extended period of time, or the storage is replenished, perhaps once each day, by manipulating the pumping schedule. This article discusses a hypothetical system comprised of a single pumped sendout, a distribution network, a single elevated storage site, and a constant‐suction water level. The pump shutoff and design heads, the volume, and the total depth and height of elevated storage have been held constant. Essentially, the pump design capacity was investigated to determine the effect of its quantity on recoverability of equalizing storage. Two operating options were considered: full daily recovery of storage by using higher‐capacity pumps; and, full recovery over about half of the year using a lower‐capacity pump, permitting the storage to float on the system. In the example presented, the annual power cost for the former appears to be 8 per cent higher. The range of pumping rates is greater, and the volume of storage utilized is less, for the daily full‐recovery option.

Complete Pump Characteristics and the Effects of Specific Speeds on Hydraulic Transients

This paper presents complete pump characteristics of specific speeds 1800, 7600, and 13,500 (gpm units) in the ν – hP (flow ratio-head ratio) co-ordinate system. The method of developing these complete pump characteristics from test data is described. The three complete pump characteristics are compared, and the effects of specific speed on hydraulic transients caused by power failure or pump shutoff is presented.