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The constitutive equation of an Euler-Bernoulli beam under the excitation of moving mass is considered. The dynamics of the uncontrolled system is governed by a linear, self-adjoint partial differential equation. A Dirac-delta function is used to describe the position of the moving mass along the beam and its inertial effects. An approximate formulation to the problem is obtained by limiting the inertial effect of the moving mass merely to the vertical component of acceleration. Having defined a "critical velocity" in terms of the fundamental period and span of the beam, it is shown that for smaller velocities, the approximate and exact approaches to the problem almost coincide. Since, the... 

This paper presents a new controller for power system stabilizer (PSS) that, unlike the conventional linear controllers, consists of both a linear and a nonlinear part. The linear part is properly designed to improve the small-signal stability margin and the damping of the local electromechanical modes. The nonlinear part is then designed to improve transient stability margin of the system without violating the features offered by the linear controller. Both parts are designed based on a perspective which attributes the system oscillations to a Hopf bifurcation (HB) phenomenon. More specifically, the design of the nonlinear part is done through the definition of a nonlinear index that... 

This paper investigates the robustness of strong structural controllability for linear time-invariant directed networked systems with respect to structural perturbations, including edge additions and deletions. In this regard, an algorithm is presented that is initiated by endowing each node of a network with a successive set of integers. Using this algorithm, a new notion of perfect graphs associated with a network is introduced, and tight upper bounds on the number of edges that can be added to, or removed from a network, while ensuring strong structural controllability, are derived. Moreover, we obtain a characterization of critical edges with respect to edge additions and deletions;... 

In this paper, we discuss the controllability of a family of linear time-invariant (LTI) networks defined on a signed graph. In this direction, we introduce the notion of positive and negative signed zero forcing sets for the controllability analysis of positive and negative eigenvalues of system matrices with the same sign pattern. A sufficient combinatorial condition that ensures the strong structural controllability of signed networks is then proposed. Moreover, an upper bound on the maximum multiplicity of positive and negative eigenvalues associated with a signed graph is provided. © 2019 IEEE  

The averaged switch modeling approach is a powerful method for representing the behavior of a wide variety of converters through equivalent circuits. The model is not linear and it is common to perform a small signal linearization about an operating point and design a linear controller. Models obtained with such method involve considerable approximation and produce results that are limited for high performance controller designs. In this paper a piecewise affine approximation technique is introduced for modeling PWM converters. This model is much more precise in predicting the dynamic response of averaged nonlinear model comparing the linear model. This paper also presents a piecewise linear... 

The eigenvalue perturbation theorem is used to propose a convex fragility criterion with application to control system design. The criterion can be considered as a non-normality measure of the controller state-space matrix. Non-normality of a matrix is defined as its distance to the nearest real normal matrix within a convex normal subspace. Based on the criterion, an H∞ method for the order reduction of linear time-invariant (LTI) controllers is developed which leads to non-fragile reduced order controllers. 2020 IEEE. Personal use is permitted, but republication/redistribution requires IEEE permission  

In this article the design and simulation of a velocity and position control for an underwater Remotely Operated Vehicle (ROV) is addressed. The system has a nonlinear dynamic with parametric uncertainties making it a reasonable test-bed for investigating the effectiveness of robust nonlinear control algorithms. The studied ROV can be actively controlled along the 3 Cartesian coordinate directions and rotated about the vertical axis using 4 thrusters positioned on the ROV. The dynamics of the actuator system, consisting of thrusters, is assumed to be a first order linear system with an unknown parameter. To control this system adaptive back-stepping, as a robust adaptive nonlinear control... 

This paper is concerned with estimation and stability of control systems over communication links subject to limited capacity, power constraint, fading, noisy feedback, and different transmission rate rather than system sampling rate. A key issue addressed in this paper is that in the presence of noisy feedback associated with channel, which models transmission of finite number of bits over such links as is the case in most practical scenarios, the well-known eigenvalues rate condition is still a tight bound for stability. Based on an information theoretic analysis, necessary conditions are derived for stability of discrete-time linear control systems via the distant controller in the mean... 

The design and implementation of linear and nonlinear control methods for a three-pole active magnetic bearing (AMB) is presented in this paper. It is shown that the system has nearly linear dynamics by adding a bias to coil currents. A decentralized PID feedback law and an integral sliding mode controller are proposed and the unknown state variables of the system are estimated by the Kalman filter. The optimal gains of the linear controller are determined by the LQG technique. To evaluate the effectiveness of the proposed controllers, they are implemented on an experimental setup. The experimental results show that the proposed methods can effectively stabilize the three-pole AMB. The... 

In this article the constitutive equation of an Euler-Bernoulli beam, excited by multiple moving masses is considered. A set of multiple piezo-ceramic actuators is used to harness the dynamic response of the beam. In this regard the beam response is suppressed by utilizing a linear control algorithm with a time varying gain matrix and displacement-velocity feedback. The efficiency of the results is investigated through the numerical analysis of an example problem  

This paper presents an optimal multi-loop control structure for uninterruptible power supply (UPS) applications which use voltage source inverter (VSI) coupled with LC filter. A resonant controller ensures tracking of sinusoidal voltage reference and rejection of sinusoidal current disturbance with no steady-state error if the loop remains stable. The challenges are reduction of output total harmonic distortion (THD), improving damping of the LC resonance frequency and preventing generation of fast closed-loop modes which go beyond the frequency range of inverter with limited switching frequency. An extension of the classic linear quadratic regulator (LQR) is proposed which addresses the... 

This paper presents a new method for tuning linear controllers such as Proportional-Integrating (PI) and Proportional-Resonant (PR) structures which are frequently used in different power electronic and power system applications. Those controllers are placed within a general structure offered by the Internal Model Principle (IMP) of control theory. In this paper, the first perspective uses the well-known concept of Linear Quadratic Regulator (LQR) to address the problem as a regulation problem. Matrix Q of the LQR design is then finely adjusted in order to assure desired transient response for the system. The second perspective is based on redefining the LQR problem in order to make it... 

In this paper a novel non-rotating space tethered configuration is introduced which its relative positions controlled using electromagnetic forces. The attitude dynamics is controlled by three reaction wheels in the body axes. The nonlinear coupled orbital dynamics of a dumbbell tethered satellite formation flight are derived through a constrained Lagrangian approach. These equations are presented in the leader satellite orbital frame. The tether is assumed to be mass-less and straight, and the J2 perturbation is included to the analysis. The forces and the moments of the electromagnetic coils are modeled based on the far-filed model of the magnetic dipoles. A guidance scheme for generating... 

The objective of this work is to design electrostatic actuators for a CMOS-MEMS nano-newton capacitive force sensor to suppress vertical vibrations disturbances. Electrostatic actuators are selected because the movable part of this force sensor is anchored to the fixed parts. In the first step, we propose a framework for simulation of the force sensor based on finite element method. The proposed model is modified utilizing comparison between the simulation and experimental models to improve the performance of the model. Then, 14 pairs of electrostatic actuators are designed for applying the control algorithm and their pull-in voltage is calculated. In next step, Modal Analysis is applied to... 

This paper is concerned with tracking state trajectory at remote controller, stability and performance of linear time-invariant noiseless dynamic systems with multiple observations over the packet erasure network subject to random packet dropout and transmission delay that does not necessarily use feedback channel full time. Three cases are considered in this paper: (1) without feedback channel, (2) with feedback channel intermittently and (3) with full time availability of feedback channel. For all three cases, coding strategies that result in reliable tracking of state trajectory at remote controller with asymptotically zero mean absolute estimation error are presented. Asymptotic mean... 

In this paper, two fractional-order linear controllers are proposed to stabilize unstable equilibrium points of a chaotic fractional-order system. The first controller is based on the dynamic output feedback control idea and requires detectability of the linearized model of the fractional-order system on the equilibrium point. The second controller is a dynamic state feedback controller and requires observability of the linearized model. In both considered cases, the stabilizability of the model is assumed. The number of inner states in the second controller is one and therefore its structure is much simpler than the first controller. To illustrate the applicability, these controllers are... 

This paper reports the design of an optimal controller to prevent suppressvertical vibration due to undesired out of plane excitations generated by environment or gripper during manipulation for a CMOS-MEMS Nano-Newton capacitive force sensor applied for biomedical applications. Undesired out of plane excitations generated by environment or gripper during manipulation is the most prevalent source of vertical vibration in this type of sensors. To suppress the vibrational movement a PZT 5A is used as actuation mechanism. Discrete element method DEM model and Modal analysis were used to find dominant natural frequencies and mode shape vectors. To eliminate out of plane excitation an optimal... 

It is generally accepted that active control systems provide better structural performance when compared to their passive counterparts. On the other hand, the design of active control systems based on linear control theory is highly dependent on the structural properties. For this reason, their performance is expected to be affected more severely by variations in structural properties compared to those of passive systems. These variations can occur due to nonlinear structural behavior, or even before that due to uncertainties in the estimation of these properties and in numerical modeling. The present work is an investigation of the dependency of various control systems used for supplemental... 

A globally convergent algorithm for synthesis of sparse optimal state feedback (SOSF) control of linear time-invariant (LTI) systems is proposed. This problem is known to be NP-hard due to its combinatorial nature. A structured H2 norm controller design problem is intrinsically non-convex, even if a fixed structure is known in advance. The proposed algorithm minimizes the H2 norm performance index, simultaneously regularizes the sparsity of the control structure using the norm. It guarantees that the solution converges to a stationary point of the original problem. The algorithm is implemented using Linear Matrix Inequalities (LMIs) which are efficient, reliable and extendable to other... 

This study investigates the asymptotic swarm stabilisation of fractional-order swarm systems in the presence of two different kinds of model uncertainties and external disturbances while the upper bound of the uncertainties is a linear function of pseudo-states norms with unknown coefficients. To this end, first a fractional-integral sliding manifold is constructed and then an adaptive-robust sliding mode controller is designed to guarantee the asymptotic swarm stability in a fractional-order linear time-invariant swarm system. The stability analysis of the proposed control system is done based on the Lyapunov stability theorem. Using the proposed controller, the coefficients of the upper...