Estimation of systemic vascular bed parameters for artificial heartcontrol

An extended Kalman filter estimator for the identification of systemic circulation model parameters during cardiac ejection and cardiac filling is described. The estimator has been developed for use in the control of a cardiac ventricular assist device. A lumped element circuit with a time-varying capacitor was used to represent the systemic circulation and the left ventricle. Since the haemodynamic variables that are measurable in patients with impaired cardiac function vary dramatically as the patients move through different levels of care, the estimator was designed so that it can be used with different sets of blood pressure and flow measurements. Preliminary evaluation of the performance of the estimator using data from a computer simulation and from a patient during open-heart surgery is presented. The robustness of the estimator to variations in parameter initialization is also described     

Mechanical ventilation and thoracic artificial lung assistance during mechanical circulatory support with PUCA pump: In silico study

Patients assisted with left ventricular assist device (LVAD) may require prolonged mechanical ventilatory assistance secondary to postoperative respiratory failure. The goal of this work is the study of the interdependent effects LVAD like pulsatile catheter (PUCA) pump and mechanical ventilatory support or thoracic artificial lung (TAL), by the hemodynamic point of view, using a numerical simulator of the human cardiovascular system. In the simulator, different circulatory sections are described using lumped parameter models. Lumped parameter models have been designed to describe the hydrodynamic behavior of both PUCA pump and thoracic artificial lung. Ventricular behavior atrial and septum functions were reproduced using variable elastance model. Starting from simulated pathological conditions we studied the effects produced on some hemodynamic variables by simultaneous PUCA pump, thoracic artificial lung or mechanical ventilation assistance. Thoracic artificial lung was applied in parallel or in hybrid mode. The effects of mechanical ventilation have been simulated by changing mean intrathoracic pressure value from −4 mmHg to +5 mmHg. The hemodynamic variables observed during the simulations, in different assisted conditions, were: left and right ventricular end systolic (diastolic) volume, systolic/diastolic aortic pressure, mean pulmonary arterial pressure, left and right mean atrial pressure, mean systemic venous pressure and the total blood flow. Results show that the application of PUCA (without mechanical ventilatory assistance) increases the total blood flow, reduces the left ventricular end systolic volume and increases the diastolic aortic pressure. Parallel TAL assistance increases the right ventricular end diastolic (systolic) volume reduction both when PUCA is switched “ON” and both when PUCA is switched “OFF”. By switching “OFF” the PUCA pump, it seems that parallel thoracic artificial lung assistance produces a greater cardiac output (respect to hybrid TAL assistance).     

Mathematical Analysis of Coronary Autoregulation and Vascular Reserve in Closed-Loop Circulation

The autoregulatory capacity of the coronary circulation has traditionally been studied in open-loop animal models where the coronary circulation was decoupled from the systemic circulation. In the closed-loop circulation, changes in arterial pressure alter coronary flow. Pressure variations can be caused by changes in cardiac contractility, preload, afterload, and heart rate. These changes also affect myocardial oxygen consumption. To maintain equilibrium between oxygen supply and consumption, coronary flow is altered by the autoregulation mechanism. Coronary resistance must change to produce the required change in coronary flow. The direction of change in coronary resistance is not directly predictable. Increased arterial pressure may result in either increased or decreased coronary resistance. To study the changes in coronary resistance in response to changes in arterial pressure that are produced by circulatory parameters, we used mathematical models. Coronary resistance was calculated to obtain equilibrium between ventricular oxygen consumption and supply for different values of contractility, preload, afterload, and heart rate. Maximum coronary resistance, indicating largest coronary vascular reserve and highest efficiency of arterial pressure generation, was defined as an optimal condition. The model predicted that the optimal value of cardiac contractility is its resting value. Minimizing end-diastolic volume and heart rate and maximizing peripheral resistance were shown to improve ventricular coronary vascular reserve. These observations suggest that afterload reduction therapy may not be beneficial for improving myocardial oxygen balance while venous vasodilatation and heart rate reduction result in greater coronary reserve.     

Total systemic arterial compliance and aortic characteristic impedance in the dog as a function of pressure: a model based study

Total arterial compliance and aortic characteristic impedance as a function of pressure in the anesthetized closed chest dog (n = 5) were studied. The three-element windkessel (consisting of a peripheral resistance, a total systemic arterial compliance, and an aortic characteristic impedance) was assumed as an arterial model. Aortic pressure was varied by pacing the heart at different rates after the production of atrioventricular block and by administration of Angiotensin and Hydralazine. Model parameters were estimated by two different methods. The first was based on a computerized optimization procedure using all the information contained in the aortic pressure and flow waveforms. The second method used the diastolic decay of aortic pressure to compute total arterial compliance and used the arterial input impedance spectrum to compute aortic characteristic impedance. Total arterial compliance and aortic characteristic impedance changed with pressure. The parameter optimization procedure yielded values of total arterial compliance ranging from 0.20 to 1.4 ml/mmHg and values of aortic characteristic impedance ranging from 0.05 to 0.42 mmHg sec/ml. Values of parameters estimated on the basis of the impedance spectrum and diastolic pressure decay were similar. Compliance values as a function of mean aortic pressure could be fitted with a bell-shaped curve similar to that found from in vitro studies of aortic segments. Characteristic impedance values as a function of mean aortic pressure could be fitted with a parabolic function the minimum of which was found in the range of control to high pressures (90-160 mmHg).     

基于弹性腔模型的下肢脉动信号仿真

脉搏波包含人体的重要生理信息,对下肢脉动信号进行仿真研究,有助于辅助临床诊断和疾病预测。根据电网络模型理论,将下肢各段动脉等效为串并联弹性腔,建立了下肢动脉仿真模型。通过matlab/simulink对该模型的脉搏波在不同动脉顺应性和外周阻力的条件下进行仿真分析,得到正常与病理状态下足背动脉脉搏波的仿真波形。结果显示,当血管顺应性减小时,收缩压升高,主波波峰前移,脉压差增大;外周阻力增大时,脉搏波上升支的幅度与斜率均增大,脉压差增大,仿真结果与实测基本吻合。该模型能较有效模拟血管不同生理参数下的脉搏波,对血管疾病的诊治和相关医疗仪器的开发具有一定应用价值。     

人工心脏磁悬浮系统涡电流位移传感器的设计

设计一种用于人工心脏的非接触式涡电流位移传感器。针对人工心脏磁悬浮系统特有的钛合金隔层结构,采用有限元分析涡电流位移传感器磁场,得到其结构参数;同时研制能实时监控传感器线圈绕制的装置,以提高线圈阻抗的一致性。经对传感器性能测试,结果显示所设计的涡电流位移传感器标准偏差为3.8%,灵敏度高于10%,能满足人工心脏磁悬浮系统的要求。     

Model-based synthetic fuzzy logic controller for indirect bloodpressure measurement

In this paper, a new measurement system for the noninvasive monitoring of the continuous blood pressure waveform in the radial artery is presented. The proposed system comprises a model-based fuzzy logic controller, an arterial tonometer and a micro syringe device. The flexible diaphragm tonometer registers the continuous blood pressure waveform. To obtain accurate measurement without distortion, the tonometer's mean chamber pressure must be kept equal to the mean arterial pressure (MAP), the so-called optimal coupling condition, such that the arterial vessel has the maximum compliance. Since the MAP cannot be measured directly, to keep the optimal coupling condition becomes a tracking control problem with unknown desired trajectory. To solve this dilemma, a model-based fuzzy logic controller is designed to compensate the change of MAP by applying a counter pressure on the tonometer chamber through the micro syringe device. The proposed controller consists of a model-based predictor and a synthetic fuzzy logic controller (SFLC). The model-based predictor estimates the MAPs changing tendency based on the identified arterial pressure-volume model.     

Study of arterial blood pressure by a Windkessel-type model: influence of arterial functional properties.

OBJECTIVE: To analyse the performance of a Windkessel blood pressure (BP) modeling of arterial compliance adjusted in a dynamic fashion according to a non-linear relationship between the arterial compliance (AC) and BP. Non invasive measurements of the radial BP waveform (MILLAR tonometry) were compared to those constructed by an electric simulator reproducing the model in a symmetrical network subdivided into 121 segments. We introduced at cardiac level the aortic stroke volume (Doppler echocardiography) and the dynamic values of compliance (relation of compliance-to pressure, constant or variable) whether the model was linear or non linear, measured by high resolution Doppler (NIUS 02) for each subject. RESULTS: At the radial artery segment the modelled BP obtained by the non linear model of AC was not significantly different from the measured BP wave, while in the linear model (AC constant at mean BP level) the systolic BP was significantly underestimated. (*P < 0.05). CONCLUSION: This work shows the limits inherent in simplification of arterial compliance in the Windkessel model using constant parameters. This demonstrates the influence of the dynamic properties of the arterial wall in a conduction artery on the level of systolic and diastolic BP.     

基于模糊免疫PID的左心室辅助装置控制系统仿真

为了提高左心室辅助装置运行的稳定性,研究了模糊免疫PID控制在左心室辅助装置控制系统中的应用.首先,分析了辅助装置的工作原理及其系统建模;其次,对模糊免疫PID控制算法进行分析;最后,进行了基于模糊免疫PID左心室辅助装置控制的仿真.仿真结果表明,模糊免疫PID控制技术比常规PID控制具有更好的控制稳定性.     

心电R波检测及控制左心辅助装置

心衰是一种威胁人类生命的主要疾病之一,左心室辅助装置作为心脏移植前的过渡支持治疗使用,对心衰终末期患者的生活质量和生存率有明显提升;在对心电图实现自动的检测中,QRS波群的检测是最关键的环节,它影响着后续数据分析和处理的正确性及准确性;设计利用数据库数据和人体心电采集数据作为原始待处理源,通过高阶低通滤波与香农能量的创新算法结合进行处理数据,在硬件上增加使用高阶自适应中值滤波算法,使得处理后的实时数据噪声降到最低,有利于准确提取到R波,最后使用测试后的心电R波驱动左心室辅助装置,达到对心衰患者进行辅助治疗的作用,并且通过MATLAB和Modelsim软件仿真成功后,在FPGA硬件上实现了实时心电信号控制血泵系统的方案;经试验测试此方法可以准确的提取R波,并且可以控制左心辅助装置同步进行泵血。     

Estimation of a physiologic strategy based on a mathematical model for assisting and substituting cardiac functions by a robotic artificial heart

In order to assist and substitute diseased cardiac functions, it is important to develop a robotic artificial heart capable of adapting to physiologic changes in the same way the natural heart does. In this paper, we propose a method of estimating a physiologic strategy based on the systemic circulation model in order enable the effective medical care and therapeutic control using an artificial heart. The physiologic strategy is estimated by the internal physiologic parameters identified from a mathematical model using online parameter identification with the δ operator and the resonant frequency is calculated from the identified physiologic parameters. In the computer simulation study, the physiologic parameters and the resonant frequency could be identified precisely. During the animal experiment, the estimated physiologic parameters and resonant frequency corresponded to the physiologic changes. In the terminal stage of the animal experiment, the physiologic parameters were changed — mean peripheral resistance was increased from 0.4 to 1.0 mmHg s/ml and mean aortic compliance was decreased from 0.50 to 0.20 mmHg/ml. The resonant frequency was synchronized with the heart rate. As a result, we estimated the physiologic strategy as the changes in the identified physiologic parameters online to assist and substitute diseased cardiac function by a robotic artificial heart.     

Basic position/force control of a single-axis arm designed with an ultrasonic motor

Recently, many studies on assist robots have been conducted in which the development of a unique system is required to support elderly people, physically handicapped people, and/or care givers. One typical system is called the assist suit, which has been used on a trial basis. The assist suit is a mechatronics device which can assist physical human actions. However, the current assist suit has a few problems with respect to cost, size, weight, endurance, and so on. This article describes a fundamental study concerning a compact assist device. The assist device supports one spot on the body, such as a knee, an elbow, or a shoulder. First, a simple single-axis arm was designed using an ultrasonic motor which can generate a high torque from a low velocity range. Then a servo-system, a torque control system, and a passive torque control system were designed and their characteristics were evaluated. In addition, the stability of the servo-system was analyzed. Here, the passive torque control includes a stiffness control and a compliance control.     

Reinforcement learning based compliance control of a robotic walk assist device

ABSTRACT

Millions of people around the globe have to deal with walking disability. Robotic walk assist devices can help people with walking disabilities, especially those with weak legs. However, safety, cost, efficiency and user friendliness are some of the key challenges. For robotic walk assist devices, light weight structure and energy efficient design as well as optimal control are vitally important. In addition, compliance control can help to improve the safety of such devices as well as contribute to their user friendliness. In this paper, an optimal adaptive compliance control is proposed for a Robotic walk assist device. The suggested scheme is based on bio-inspired reinforcement learning. It is completely dynamic-model-free scheme and employs joint position and velocity feedback as well as sensed joint torque (applied by user during walk) for compliance control. The efficiency of the controller is tested in simulation on a robotic walk assisting device model.     

矿井通风除尘试验装置及PLC监控系统设计

基于实验室通风环境,设计了一套矿井通风除尘试验装置及PLC监控系统。该通风除尘试验装置集通风与除尘功能于一体,能自动监测通风机与除尘器的风量、风压、阻力等性能参数;PLC监控系统可对通风机、发尘器进行远程/就地开停及变频调速控制,实时监测通风机、发尘器运行状态、运行电流、运行频率等参数,模拟并实现了矿井通风系统的井下通风计算机远程集中监控。实际应用表明,该系统运行稳定可靠、操作简便、可扩展性强。     

Adaptive hybrid force/position control of robot manipulators using an adaptive force estimator in the presence of parametric uncertainty

This study is devoted to sensorless adaptive force/position control of robot manipulators using a position-based adaptive force estimator (AFE) and a force-based adaptive environment compliance estimator. Unlike the other sensorless method in force control that uses disturbance observer and needs an accurate model of the manipulator, in this method, the unknown parameters of the robot can be estimated along with the force control. Even more, the environment compliance can be estimated simultaneously to achieve tracking force control. In fact, this study deals with three challenging problems: No force sensor is used, environment stiffness is unknown, and some parametric uncertainties exist in the robot model. A theorem offers control laws and updating laws for two control loops. In the inner loop, AFE estimates the exerted force, and then, the force control law in the outer loop modifies the desired trajectory of the manipulator for the adaptive tracking loop. Besides, an updating law updates the estimated compliance to provide an accurate tracking force control. Some experimental results of a PHANToM Premium robot are provided to validate the proposed scheme. In addition, some simulations are presented that verify the performance of the controller for different situations in interaction.     

Adaptive sliding mode control for a general nonlinear multicompartment lung model with input pressure and rate saturation constraints

In this article, we develop an output feedback adaptive sliding mode controller for a general multicompartment lung mechanics model with nonlinear resistance and compliance respiratory parameters. Specifically, for a given clinically plausible reference volume pattern, we develop an adaptive sliding mode controller that accounts for input pressure and rate saturation constraints to automatically adjust the applied input pressure by the mechanical ventilator so that the total lung volume tracks the given reference pattern. The pressure due to lung muscle activity is also considered in the controller design. A Lyapunov‐based approach is presented to show convergence of the closed‐loop system, and the proposed control framework is applied to a two‐compartment lung model to show the efficacy of the proposed control method. Copyright © 2015 John Wiley & Sons, Ltd.     

Computational model of three-dimensional cardiac electromechanics

We coupled a continuum model of impulse propagation with a three-dimensional model of regional ventricular mechanics. Equations for action potential propagation, myofilament activation and active contraction were solved in an anatomically detailed finite element model of canine left and right ventricular geometry, muscle fiber architecture and Purkinje fiber network anatomy. Finite element equations for time-dependent excitation and recovery variables were assembled using a collocation method and solved using adaptive Runge-Kutta integration. Resting tissue mechanics were modeled as nonlinear, orthotropic and hyperelastic. A Windkessel model for arterial impedance was coupled to ventricular pressure and volume to compute hemodynamic boundary conditions during ejection. Ventricular volume constraints were imposed during the isovolumic phases. This model showed good agreement in the time course of regional systolic strains with experimental measurements during normal sinus rhythm and demonstrates the importance of the Purkinje fiber system in determining the mechanical activation sequence.     

基于出风温湿度检测的冷却塔防白雾控制装置设计

设计一种基于出风温湿度检测的冷却塔防白雾控制装置,该装置可实现出风温湿度参数的实时采集,并进行相应计算,根据计算结果判断冷却塔是否处于雾区,从而实现防白雾水泵的自动变压控制,利用电动阀控制最大进水量,实现较小混水量的消雾,节约成本。     

基于变频器的水位自动控制系统设计

针对传统人工控制水泵自动化水平低、电能浪费严重的问题,设计出一种采用变频器和水位压力传感器相结合的系统,利用变频器内置PID功能,控制水泵流量,从而实现蓄水池水位的自动控制。给出了设备选型、线路原理图、变频器内置PID参数计算和相关参数设置。     

备用泵组自动投入装置的研究与应用

通过摸索,发明了这一泵组装置。装置带有自动投入的特性,被安设在供水泵站以内。这样的装置,能辨识异常态势下的出口压力、出口阀门带有的流量;在辨识的基础上,启动现有的备用泵组。因此,这一装置化解掉了自动投入的疑难,在供水设备产出故障时,或者水泵本体产出故障时,可以维持住泵站带有的稳定性。自动投入情形下的泵组装置,为后续时段内的生产,供应了可用的保证。