Showing papers by "Cristina I. Muresan published in 2020"

Closed-Loop Control of Anesthesia: Survey on Actual Trends, Challenges and Perspectives

Abstract: Automation empowers self-sustainable adaptive processes and personalized services in many industries. The implementation of the integrated healthcare paradigm built on Health 4.0 is expected to transform any area in medicine due to the lightning-speed advances in control, robotics, artificial intelligence, sensors etc. The two objectives of this article, as addressed to different entities, are: i) to raise awareness throughout the anesthesiologists about the usefulness of integrating automation and data exchange in their clinical practice for providing increased attention to alarming situations, ii) to provide the actualized insights of drug-delivery research in order to create an opening horizon towards precision medicine with significantly improved human outcomes. This article presents a concise overview on the recent evolution of closed-loop anesthesia delivery control systems by means of control strategies, depth of anesthesia monitors, patient modelling, safety systems, and validation in clinical trials. For decades, anesthesia control has been in the midst of transformative changes, going from simple controllers to integrative strategies of two or more components, but not achieving yet the breakthrough of an integrated system. However, the scientific advances that happen at high speed need a modern review to identify the current technological gaps, societal implications, and implementation barriers. This article provides a good basis for control research in clinical anesthesia to endorse new challenges for intelligent systems towards individualized patient care. At this connection point of clinical and engineering frameworks through (semi-) automation, the following can be granted: patient safety, economical efficiency, and clinicians’ efficacy.

Mathematical modelling with experimental validation of viscoelastic properties in non-Newtonian fluids.

Abstract: The paper proposes a mathematical framework for the use of fractional-order impedance models to capture fluid mechanics properties in frequency-domain experimental datasets. An overview of non-Newtonian (NN) fluid classification is given as to motivate the use of fractional-order models as natural solutions to capture fluid dynamics. Four classes of fluids are tested: oil, sugar, detergent and liquid soap. Three nonlinear identification methods are used to fit the model: nonlinear least squares, genetic algorithms and particle swarm optimization. The model identification results obtained from experimental datasets suggest the proposed model is useful to characterize various degree of viscoelasticity in NN fluids. The advantage of the proposed model is that it is compact, while capturing the fluid properties and can be identified in real-time for further use in prediction or control applications. This article is part of the theme issue 'Advanced materials modelling via fractional calculus: challenges and perspectives'.

Robust controller design: Recent emerging concepts for control of mechatronic systems

Abstract: The recent industrial revolution puts competitive requirements on most manufacturing and mechatronic processes. Some of these are economic driven, but most of them have an intrinsic projection on the loop performance achieved in most of closed loops across the various process layers. It turns out that successful operation in a globalization context can only be ensured by robust tuning of controller parameter as an effective way to deal with continuously changing end-user specs and raw product properties. Still, ease of communication in non-specialised process engineering vocabulary must be ensured at all times and ease of implementation on already existing platforms is preferred. Specifications as settling time, overshoot and robustness have a direct meaning in terms of process output and remain most popular amongst process engineers. An intuitive tuning procedure for robustness is based on linear system tools such as frequency response and bandlimited specifications thereof. Loop shaping remains a mature and easy to use methodology, although its tools such as Hinf remain in the shadow of classical PID control for industrial applications. Recently, next to these popular loop shaping methods, new tools have emerged, i.e. fractional order controller tuning rules. The key feature of the latter group is an intrinsic robustness to variations in the gain, time delay and time constant values, hence ideally suited for loop shaping purpose. In this paper, both methods are sketched and discussed in terms of their advantages and disadvantages. A real life control application used in mechatronic applications illustrates the proposed claims. The results support the claim that fractional order controllers outperform in terms of versatility the Hinf control, without losing the generality of conclusions. The paper pleads towards the use of the emerging tools as they are now ready for broader use, while providing the reader with a good perspective of their potential.

Context Aware Control Systems: An Engineering Applications Perspective

Abstract: Cyber-physical systems revolve around context awareness, empowering objective-oriented services, products and operations based on real data. Self-aware and self-control systems are core elements in the Industry 4.0 framework towards self-sustainable adaptive manufacturing and personalized services. This development is witnessed by the context-aware pervasive assistance to users and machines in decisions making process for optimizing product performance and economic yield. While integration of the virtual and the physical world entails smart sensors communication and complex data analytics, it relies on artificial intelligence tools to manage process operations. The objective of the article is to create awareness that systems & control community must address theoretical and practical aspects from a larger perspective. Context aware control is emerging as a natural solution to maximize the use of available sensing instrumentation and the relatively low cost data logging, i.e. an important source for extracting information, interpreting and using context information and adapt its functionality to the current context of use. This article presents a concise overview of applications where context aware systems and control methodologies are relevant in the seven societal challenges acknowledged by European policy-makers: Digital Society; Food; Health and Well-Being; Smart Resource Management; Urban Planning, Mobility Dynamics and Logistics; New Energy Demand and Delivery; and Society.

Generalization of the FOPDT Model for Identification and Control Purposes

Abstract: This paper proposes a theoretical framework for generalization of the well established first order plus dead time (FOPDT) model for linear systems. The FOPDT model has been broadly used in practice to capture essential dynamic response of real life processes for the purpose of control design systems. Recently, the model has been revisited towards a generalization of its orders, i.e., non-integer Laplace order and fractional order delay. This paper investigates the stability margins as they vary with each generalization step. The relevance of this generalization has great implications in both the identification of dynamic processes as well as in the controller parameter design of dynamic feedback closed loops. The discussion section addresses in detail each of this aspect and points the reader towards the potential unlocked by this contribution.

Event-Based Implementation of Fractional Order IMC Controllers for Simple FOPDT Processes

Abstract: Fractional order calculus has been used to generalize various types of controllers, including internal model controllers (IMC). The focus of this manuscript is towards fractional order IMCs for first order plus dead-time (FOPDT) processes, including delay and lag dominant ones. The design is novel at it is based on a new approximation approach, the non-rational transfer function method. This allows for a more accurate approximation of the process dead-time and ensures an improved closed loop response. The main problem with fractional order controllers is concerned with their implementation as higher order transfer functions. In cases where central processing unit CPU, bandwidth allocation, and energy usage are limited, resources need to be efficiently managed. This can be achieved using an event-based implementation. The novelty of this paper resides in such an event-based algorithm for fractional order IMC (FO-IMC) controllers. Numerical results are provided for lag and delay dominant FOPDT processes. For comparison purposes, an integer order PI controller, tuned according to the same performance specifications as the FO-IMC, is also implemented as an event-based control strategy. The numerical results show that the proposed event-based implementation for the FO-IMC controller is suitable and provides for a smaller computational effort, thus being more suitable in various industrial applications.

An Experimental Tuning Approach of Fractional Order Controllers in the Frequency Domain

Abstract: Fractional calculus has been used intensely in recent years in control engineering to extend the capabilities of the classical proportional–integral–derivative (PID) controller, but most tuning techniques are based on the model of the process. The paper presents an experimental tuning procedure for fractional-order proportional integral–proportional derivative (PI/PD) and PID-type controllers that eliminates the need of a mathematical model for the process. The tuning procedure consists in recreating the Bode magnitude plot using experimental tests and imposing the desired shape of the closed loop system magnitude. The proposed method is validated in the field of active vibration suppression by using an experimental set-up consisting of a smart beam.

Fractional-Order Models for Biochemical Processes

Abstract: Biochemical processes present complex mechanisms and can be described by various computational models. Complex systems present a variety of problems, especially the loss of intuitive understanding. The present work uses fractional-order calculus to obtain mathematical models for erythritol and mannitol synthesis. The obtained models are useful for both prediction and process optimization. The models present the complex behavior of the process due to the fractional order, without losing the physical meaning of gain and time constants. To validate each obtained model, the simulation results were compared with experimental data. In order to highlight the advantages of fractional-order models, comparisons with the corresponding integer-order models are presented.

An event based implementation of a fractional order controller on a non-Newtonian transiting robot.

Abstract: Fractional order control is an emerging topic in the field of control engineering due to its numerous advantages. Many control strategies such as the Proportional Integral Derivative, Internal Model Control, robust or predictive controllers have a generalization into the fractional calculus theory or offer fractional order implementation possibilities. The present study tackles the event-based implementation of fractional controllers. The task is complex due to the higher orders needed to approximate fractional elements and the scarce availability of direct discretization methods for fractional operators. The proposed strategy is validated through simulations on a scalable nanorobot designed to transit non-Newtonian environments. The event-based algorithm implements a Fractional Order Proportional Derivative (FOPD) that controls the position of the nanorobot, validating the presented solution for implementing fractional order event based controllers.

An Efficient Design and Implementation of a Quadrotor Unmanned Aerial Vehicle Using Quaternion-Based Estimator

Abstract: The main goal of the research is to design a low-cost, performing quadrotor unmaned aerial vehicle (UAV) system. Because of low cost limits, the performance must be ensured by other ways. The present proposal is a quaternion-based estimator used in the control loop. In order to make the proposed solution easy to be reproduced by the reader, step-by-step instructions are given, including component choices, design, and implementation. Throughout the article, detailed description of the system model is given. The efficacy of the suggested quaternion-based predictive control is evaluated by extended experimental results.

Fractional Order Internal Model Control Strategies for a Submerged Nanorobot

Abstract: Fractional calculus is a well-known tool that improves the closed loop performance of processes when compared to integer order approaches. The study presents a generalization of the popular Internal Model Control (IMC) strategy for fractional order processes of any complexity. The controller is based on the inverse fractional order transfer function to which a fractional order filter is added. The velocity of a scalable nanorobot operating in submersed environments is the chosen process to exemplify the proposed control strategy. The Fractional Order Internal Model Control (FOIMC) is developed for the fractional dynamics of the robot. The validity of method is proved through simulations regarding reference tracking, disturbance rejection and robustness to gain variations.

A non-Newtonian impedance measurement experimental framework: modeling and control inside blood-like environments—fractional-order modeling and control of a targeted drug delivery prototype with impedance measurement capabilities

Abstract: The chapter is focused on presenting an experimental setup that mimics the non-Newtonian nature of blood environments. The platform was developed with didactic purposes to familiarize oneself with the interaction between submerged devices and non-Newtonian surroundings. The blood environment is a platform resembling a primary circulatory system consisting of a liquid with non-Newtonian particularities flowing inside a vein/artery. The submerged device is a small-scale robot looking like a submarine, which is equipped with a thrusting propeller and an impedance measuring sensor. The submersible travels through the blood-like environment measuring the impedance of the fluid and stops in areas where unusual impedance values are detected. The dynamics of the robot are modeled using fractional-order differentiation, and control capabilities are implemented in order to ensure proper operation.

A real life implementation of fractional order event based PI control

Abstract: The paper presents a novel generalization of available integer-order event based control strategies into the fractional order field, offering a real life implementation possibility of event based fractional order control. A fractional order Proportional Integral (FOPI) controller is tuned using a set of frequency domain specifications such as gain crossover frequency, phase margin and robustness. A generalized theoretical approach is developed for FOPI event based control strategies. In addition, real-life solutions are provided in order to implement the FOPI controller on a Vertical Take-Off and Landing (VTOL) platform. The proposed methodology is validated experimentally by assessing the closed loop system performance in various scenarios such as step reference tracking, disturbance rejection and robustness to gain uncertainties.

Internal Model Control: Efficient Disturbance Rejection for Dead-Time Process Models with Validation on an Active Suspension System.

Abstract: Internal Model Control algorithms have numerous advantages, linked to the simplicity of the tuning procedure, the intrinsic dead-time compensation, reasonable robustness. In this paper, a novel idea for tuning an optimized IMC filter for input or load disturbance rejection is used and validated experimentally on a poorly damped process, an active suspension system. The core principle of the design is that the disturbance filter compensates for the process dead-times, provided that the disturbances have a stochastic nature with the spectral energy centered in a narrow frequency band (such as quasi-periodic disturbances). Diophantine equations are used to compute the disturbance filter coefficients. The experimental results show that the novel IMC controller improves the rejection capabilities of the standard default IMC algorithm. Validation is performed considering variations in the disturbance frequency. An adaptive suspension control situation is also tested, with an adapted IMC controller improving even further the disturbance attenuation properties of the proposed optimized IMC.

Experimental validation of the KC autotuner on a highly nonlinear vertical take-off and landing (VTOL) process

Abstract: The paper focuses on a novel PID (proportional integral derivative) autotuner based on a single experi-mental sine test. The Kiss Circle (KC) autotuner design and validation are targeted on a vertical take-off and landing platform which exhibits a highly oscillatory non-linear motion with time delay. An additional autotuner fit for time delay processes such as the well-known Ziegler-Nichols method is used to determine a PID controller for the Vertical Take-Off and Landing (VTOL) process. The experimental results obtained with the two different experimental tuning methods under several operating conditions are compared, illustrating the superiority of the KC autotuner.