Optimal control of nonlinear systems with input constraints using linear time varying approximations

We propose a new method to solve input constrained optimal control problems for autonomous nonlinear systems affine in control. We then extend the method to compute the bang-bang control solutions under the symmetric control constraints. The most attractive aspect of the proposed technique is that it enables the use of linear quadratic control theory on the input constrained linear and nonlinear systems. We illustrate the effectiveness of our technique both on linear and nonlinear examples and compare our results with those of the literature

Force control of a tri-layer conducting polymer actuator using optimized fuzzy logic control

Conducting polymers actuators (CPAs) are potential candidates for replacing conventional actuators in various fields, such as robotics and biomedical engineering, due to their advantageous properties, which includes their low cost, light weight, low actuation voltage and biocompatibility. As these actuators are very suitable for use in micro-nano manipulation and in injection devices in which the magnitude of the force applied to the target is of crucial importance, the force generated by CPAs needs to be accurately controlled. In this paper, a fuzzy logic (FL) controller with a Mamdani inference system is designed to control the blocking force of a trilayer CPA with polypyrrole electrodes, which operates in air. The particle swarm optimization (PSO) method is employed to optimize the controller\u27s membership function parameters and therefore enhance the performance of the FL controller. An adaptive neuro-fuzzy inference system model, which can capture the nonlinear dynamics of the actuator, is utilized in the optimization process. The optimized Mamdani FL controller is then implemented on the CPA experimentally, and its performance is compared with a non-optimized fuzzy controller as well as with those obtained from a conventional PID controller. The results presented indicate that the blocking force at the tip of the CPA can be effectively controlled by the optimized FL controller, which shows excellent transient and steady state characteristics but increases the control voltage compared to the non-optimized fuzzy controllers

Hızlı bir feribotun düşey ivmelenmesinin T-Foil ve trim tab sistem

his study is concerned with the active T-foil placed near the bow on the keel line of the fast ferry and two active trim tab controls placed at the stern to improve the maritime performance of a fast ferry, whilst improving the comfort and safety of passengers and crew. In the scope of the study, the vertical direction of the fast ferry under the random head waves, heave and pitch motions were taken into account. For the control of T-foil and trim Tabs, PID and LQR control methods were used. The purpose of these controllers is to reduce the acceleration of the heave and pitch motions of the fast ferry by changing the operating angles of the T-foil and trim tab wings. A random wave model was created using the Pierson-Moskowitz model, and simulations were done assuming that the fast ferry was subjected to random head waves. Finally, in order to see the effect of vertical acceleration on passengers, the rate of seasickness (MSI) change of the fast ferry in uncontrolled and controlled states was examined. Mathematical models of fast ferry, T-foil and trim tab and their simulations were carried out in MATLAB / Simulink environment. The simulation results show that T-foil and trim tab Active systems can effectively reduce vertical acceleration by improving heave and pitch motions.Bu çalışma, hızlı bir feribotun denizcilik performansını iyileştirmek, yolcu ile mürettebatın konfor ve güvenliğini artırmak için hızlı feribotun omurga hattında pruvaya yakın bir noktaya yerleştirilen hareketli T-foil ve kıç tarafına yerleştirilen iki adet hareketli trim tab kontrolü ile ilgilidir. Çalışma kapsamında baştan gelen düzensiz dalgaların etkisindeki hızlı feribotun düşey yönde yaptığı baş kıç vurma ve dalıp çıkma hareketleri dikkate alınmıştır. T-foil ve trim tabların kontrolü için ise PID ve LQR kontrol yöntemleri kullanılmıştır. Bu kontrolörlerin amacı, T-foil ve trim tab kanatlarının çalışma açılarının değiştirilmesiyle hızlı feribotun pozisyonunu kontrol ederek baş kıç vurma ve dalıp çıkma hareketlerinin ivmelenmesini azaltmaktır. Pierson-Moskowitz modelinden yararlanılarak düzensiz bir dalga modeli oluşturulmuş ve çalışmalar hızlı feribotun baştan gelen düzensiz dalgalara maruz kaldığı varsayılarak yapılmıştır. Son olarak düşey ivmelenmenin yolcular üzerindeki etkisini görebilmek için hızlı feribotun kontrolsüz ve kontrollü durumda deniz tutması oranı (MSI) değişimi incelenmiştir. Hızlı feribotun, T-foilin ve trim tabın matematiksel modelleri MATLAB / Simulink ortamında elde edilerek simülasyonları gerçekleştirilmiştir. Simülasyon sonuçları, T-foil ve trim tab aktif sistemlerinin baş kıç vurma ve dalıp çıkma hareketlerini iyileştirerek düşey ivmelenmeyi etkili bir şekilde azaltabildiğini göstermektedir

Syndrome of Inappropriate Secretion of Antidiuretic Hormone Cholestasis and Pericardial Effusion Due to Brucellosis Infection: A Case Report

Syndrome of inappropriate secretion of antidiuretic hormone (SIADH) is an extremely rare complication of infectious diseases. A rare case of brucellosis complicated by syndrome of inappropriate secretion of antidiuretic hormone (SIADH) cholestasis and pericardial involvement is reported. A 27-year-old woman was admitted for fever, abdominal pain, and scleral icterus. Her medical history revealed no recent use of diuretic agents. In addition to cholestasis and elevated liver enzymes, euvolemic hyponatremia, hypouricemia, low plasma osmolality, and high urinary osmolality were also detected. Surrenal and thyroid tests were also within normal range. Echocardiography revealed minimal pericardial effusion with normal cardiac functions. The final diagnosis was SIADH due to Brucellosis. Hyponatremia, cholestasis, and pericardial disease were resolved with effective antibrucellar treatment with streptomycine and doxycycline. After completing treatment of brucellosis, there was not any more evidence of cholestasis and pericardial fluid

Fuzzy control of a conjugated polymer actuator

Polypyrrole actuators may represent time varying and nonlinear dynamics as the solvent evaporation continuously affects their performance. Linear models can be used to design controllers for polypyrrole actuators to some extent but their performance may not be sufficient in order to comply with the requirements for applications where high precision is necessary. This paper proposes a Fuzzy Logic controller to improve the tracking performance of a trilayer polypyyrole conducting polymer actuator. As the fuzzy controller does not require a model for the system, the nonlinearities and uncertainties can be handled effectively. Experimental results show that fuzzy control improves the tracking performance compared to the conventional PID controller which is designed based on a linear model of the polypyrrole actuator

Nonlinear dynamical systems with applications to cancer modelling and control

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Model-free control of an electro-active polymer actuator

Conducting polymer actuators (CPAs) are promising candidates for replacing conventional actuators due to their advantageous properties such as low cost, low weight, small actuation voltage and biocompatibility. One of the obstacles for these actuators to become widespread in real world applications is the difficulty of controlling their position or force output as these actuators represent time varying and nonlinear dynamics due to various effects such as synthesis process and conditions, changes in ambient conditions, etc. Linear models are of limited use to design controllers for them since the performance of these controllers may not be sufficient due to model mismatches. Especially, due to their time varying behaviour, a pre-designed controller based on an identified model may show performance deterioration in time. In this study, a model-free control framework is proposed to control the tip displacement of a trilayer conducting polymer actuator with polypyrrole electrodes. The proposed control strategy eliminates the requirement of identification of the dynamics of CPAs for each application and is based on fast derivative estimation of noisy signals. Another advantage of the method is that it is very simple to design and implement. Experimental results are obtained for the model free control method and compared with those of classical PI control

Hybrid force and position control of a conducting tri-layer electro-active polymer actuator

In this study, the displacement and blocking force of the tip point of a cantilevered electro-active polymer (EAP) actuator has been controlled for a cell injection process which consists of approaching, interacting and leaving steps. A vision-based system is used to acquire the tip displacement data for identifying a transfer function model of the actuator and its position control. Discrete time Proportional-Integral controllers are used to control the position and blocking force. A Smith Predictor is utilized in the vision-based position control system to compensate for the time delay due to image processing. Experimental position and blocking force results prove that the proposed control strategies are effective enough to guide the actuator to undertake the cell injection process. This study contributes to the previously published work from the point of view of simultaneously controlling the position and blocking force of the electroactive polymer actuators and widening their application areas

Vibration suppression of an elastic beam via sliding mode control

This paper presents experimental results of sliding mode control (SMC) technique applied to an elastic beam. The aim of the controller is to suppress first two vibration modes of the beam. Mathematical model of the beam is a finite dimensional model obtained from the Bernoulli-Euler beam equation. As the system states are to be available in order to design the SMC, an observer has been designed to obtain the states of the system by measuring tip deflection of the beam. By using observed states of the finite dimensional model, SMC is designed and applied to the elastic beam giving thoroughly suppressed vibration modes