Sharif Digital Repository

A dynamic model of a remotely operated vehicle (ROV) is developed. The hydrodynamic damping coefficients are estimated using a semi-predictive approach and computational fluid dynamic software ANSYS-CFX™ and WAMIT™. A sliding-mode controller (SMC) is then designed for the ROV model. The controller is subsequently robustified against modeling uncertainties, disturbances, and measurement errors. It is shown that when the system is subjected to bounded uncertainties, the SMC will preserve stability and tracking response. The paper ends with simulation results for a variety of conditions such as disturbances and parametric uncertainties. © 2018, Harbin Engineering University and Springer-Verlag... 

A dynamic model of a remotely operated vehicle (ROV) is developed. The hydrodynamic damping coefficients are estimated using a semi-predictive approach and computational fluid dynamic software ANSYS-CFX™ and WAMIT™. A sliding-mode controller (SMC) is then designed for the ROV model. The controller is subsequently robustified against modeling uncertainties, disturbances, and measurement errors. It is shown that when the system is subjected to bounded uncertainties, the SMC will preserve stability and tracking response. The paper ends with simulation results for a variety of conditions such as disturbances and parametric uncertainties. © 2018, Harbin Engineering University and Springer-Verlag... 

In this paper, the computation of robustness margin for linear time invariant fractional order systems is studied. For the definition of robustness margin, we employ the one introduced for polynomials (i.e. integer order) and extend it to fractional order functions. Using the well known concept of the value set and knowing its shape for the intended functions, this paper presents an easy way to obtain the robustness margin for fractional order systems. To illustrate the results, a numerical example is provided  

This paper deals with the analysis of robust BIBO-stability of LTI fractional order delay systems in the presence of real parametric uncertainties. Two large classes of these systems, namely retarded and neutral types, are considered. Two theorems are given to check the robust BIBO-stability of these two families of fractional order systems. One of these theorems provides necessary and sufficient conditions for the case of retarded type and another one presents only sufficient conditions for the case of neutral type. Furthermore, upper and lower bounds (cutoff frequencies) are provided for drawing the value sets. To illustrate the results, two numerical examples are presented  

We introduce a novel probabilistic framework to achieve robust non-fragile tuning methods in control of processes with parametric uncertainties. We consider probability distributions to model the process parameters' uncertainties. First, we propose the tuning framework in a general setting. Then, as an illustration, we apply it to PD control of IPD-modeled processes. It is noteworthy that the proposed tuning method is robust against the considered parametric uncertainties. Also, to empower the proposed robust tuning method in the viewpoint of non-fragility, we utilize a centroid approach. Selecting the form of the probabilistic framework, we empirically observe some of the popular tuning... 

Performance of a haptic device is evaluated based on the concept of transparency. Stability of a haptic device prevalently has been evaluated based on the passivity criterion. Due to conservativeness of passivity, it appears as an obstacle to improve transparency. In this paper, passivity is suggested to be replaced by the complementary stability criterion which accounts for the robust stability of the interaction in the presence of uncertain user hand dynamics. In this respect, an algorithm is proposed which guarantees transparency of the haptic device in a stable manner. Assuming that the dynamics of the device is known, a certain compensatory structure is assigned. This special structure... 

During the drug delivery process in chemotherapy, both of the cancer cells and normal healthy cells may be killed. In this paper, three mathematical cell-kill models including log-kill hypothesis, Norton-Simon hypothesis and Emax hypothesis are considered. Three control approaches including optimal linear regulation, nonlinear optimal control based on variation of extremals and H∞-robust control based on μ-synthesis are developed. An appropriate cost function is defined such that the amount of required drug is minimized while the tumor volume is reduced. For the first time, performance of the system is investigated and compared for three control strategies; applied on three nonlinear models... 

Performance control of a boiler–turbine unit is of great importance due to demands for the economical operations of power plants and environmental awareness. In this paper, an optimal control strategy is designed to achieve the desired performance of a boiler–turbine unit. A multivariable nonlinear model of a utility boiler–turbine unit is considered. By manipulation of valves position for the fuel, steam and feed-water flows; output variables including the drum pressure, electric output and fluid density (and consequently drum water level) are controlled. Performance measure of the problem is defined such that the control efforts are minimized while the tracking objectives are obtained. In... 

The performance of hapticdevicesisevaluatedbasedontheconceptoftransparency, whiletheirstabilityhasprevalentlybeenevaluatedbasedonthepassivitycriterion. Duetotheconservativenessofpassivity, itappearsasanobstacletoimprovingtransparency.Inthepresentpaper, passivityissuggestedtobereplacedbythecomplementarystabilitycriterionwhichaccoun tsfortherobuststabilityoftheinteractioninthepresnceofuncertainuserhanddynamics. Inthisrespect, analgorithmisproposedwhichguaranteestransparencyofthehapticdeviceinastablemanne r.Assumingthatthedynamicsofthedeviceisknown, acertaincompensatorystructureisassigned. Thisspecialstructureguaranteestransparencyofthedevicebycompensatingforthedynami... 

Air-handling unit (AHU) is one of the most complex installations that its control is necessary for maintaining satisfactory comfort conditions in buildings with low energy utilization. In this paper, a multivariable nonlinear and minimum phase model of the AHU is considered in the presence of uncertainties. The controller design is divided into two types. The first controller type is for the linearized plant based on decoupled PID-Fuzzy and PD-type Fuzzy controllers. The second type is based on full matrix PID-Fuzzy and pole-placement controllers in which interaction effects are considered. The indoor temperature and relative humidity are controlled via manipulation of valve positions of air... 

This paper presents sliding mode control and model reference adaptive control strategies for the tape transport mechanism. A nonlinear multivariable MIMO model of the process, consisting of take-up and supply reel servos for tape tension control and capstan servo for speed control is considered. The sliding mode control is applied for the nonlinear dynamic model of the process, while the model reference adaptive control deals with the linearized one. Moreover, in order to associate with the realistic model of system, design of controllers is accomplished with respect to parametric uncertainties. It is shown that both control strategies can guarantee asymptotic stability of the closed-loop... 

In this paper, modeling and vibration control of a strain-gradient clamped-free Euler-Bernoulli micro-beam exposed to varying disturbance is studied. A strain-gradient model of the Euler-Bernoulli micro-beam is represented in this paper and consisted of one partial differential equation and six ordinary equations as governing motion equation and boundary conditions, respectively. A boundary controller is proposed to suppress the system's vibration. The controller is derived based on the direct Lyapunov method. An adaptation law is devised to assure system's stability under parametric uncertainties. With the proposed adaptive robust boundary control, uniform boundedness under environmental... 

Ground reaction force (GRF) characteristics of amputee walking are important for the analysis of clinical gait data, and also to update model reference adaptive impedance (MRAI) controllers. GRF estimation is a better alternative than direct GRF measurement because of the disadvantages of load cells, such as high cost, integration difficulties due to weight and physical dimensions, the possibility of overload, and measurement noise. This paper presents four robust MRAI observer/controller combinations for GRF estimation-based control of a prosthesis and a legged robot model in the presence of parametric uncertainties and unmodeled dynamics, in which the robot model is employed to mimic... 

Chatter suppression is an important topic in any type of machining process. In this paper, orthogonal cutting process is modeled as a single degree of freedom dynamic system. A nonlinear delay differential equation is presented that models flank wear of the tool. Uncertainties in cutting velocity, tool wear size and parameters of the dynamic model are included in the model of cutting process. The force provided by a piezo-actuator is taken as the control input of the system. A sliding mode control scheme is used and an effective control law is derived which suppresses the chatter vibration. Results for two distinct cases of a sharp tool and a worn tool are presented and compared which shows... 

Since the injection of the oncolytic viruses in the virotherapy process reduces the toxicity and drug resistance inherent in the chemotherapy; chemovirotherapy as a novel combination therapy has become an efficient cancer treatment. The primary purpose of this paper is to design a robust optimal control strategy for the chemovirotherapy through which the tumor density decreases to its stable condition with limited drug and virus delivery. This desired treatment should be responsive in the presence of input disturbances and parametric uncertainties. In this regard, an ODE (Ordinary Differential Equation) mathematical model of the chemovirotherapy process presenting the connection between the... 

In this paper, the robust bounded-input bounded-output stability of a large class of linear time invariant fractional order families of systems with real parametric uncertainties is analyzed. The transfer functions contain polynomials in fractional powers of the Laplace variable s, possibly in combination with exponentials of fractional powers of s. Using the concept of the value set and a generalization of the zero exclusion condition theorem, a theorem to check the robust bounded-input bounded-output stability of these families of systems is presented. An upper cutoff frequency for drawing the value sets is provided as well. Finally, two numerical examples are given to illustrate results... 

Tape mechanisms must be able to transport the tape with a constant velocity for achieving high rate of data transfer. In this paper, a multivariable model of tape transport mechanism including the take-up and supply reel servos for tape tension control and capstan servo for speed control is considered. To achieve desired performance,pole-placement approach based on general canonical control form (GCCF) is used. Instead of using expensive tension sensors, an observer is designed. A regulator system is developed for disturbance rejection; and a modified integral control is designed for perfect tracking of desired setpoints in tape speed and tensions. Since the real dynamic model associates... 

Tape mechanisms must be able to transport the tape with a constant velocity for achieving high rate of data transfer. In this paper, a multivariable model of tape transport mechanism including the take-up and supply reel servos for tape tension control and capstan servo for speed control is considered. To achieve desired performance,pole-placement approach based on general canonical control form (GCCF) is used. Instead of using expensive tension sensors, an observer is designed. A regulator system is developed for disturbance rejection; and a modified integral control is designed for perfect tracking of desired setpoints in tape speed and tensions. Since the real dynamic model associates... 

In this paper, a new nonlinear robust adaptive impedance controller is addressed for Unmanned Aerial Vehicles (UAVs) equipped with a robot manipulator that physically interacts with environment. A UAV equipped with a robot manipulator is a novel system that can perform different tasks instead of human being in dangerous and/or inaccessible environments. The objective of the proposed robust adaptive controller is control of the UAV and its robotic manipulators end-effector impedance in Cartesian space in order to have a stable physical interaction with environment. The proposed controller is robust against parametric uncertainties in the nonlinear dynamics model of the UAV and the robot...