Sharif Digital Repository

In this paper, a novel robust adaptive control method is proposed for controlling the Lorenz chaotic attractor. A new backstepping controller for the Lorenz system based on the Lyapunov stability theorem is proposed to overcome the singularity problem that appeared in using the typical backstepping control method. By exploiting the property of the system, the resulting controller is shown to be singularity free and the closed loop system is globally stable. Due to unavailability of system states measurement in practice, the controller is selected such that only one system state is needed. To overcome the problem of parameter uncertainty, an additional term to Lyapunov function is added and... 

The N-3 Revolute-Prismatic-Spherical (N-3RPS) manipulator is a kind of serial-parallel manipulator and has higher stiffness and accuracy compared with serial mechanisms, and a larger workspace compared with parallel mechanisms. The locking mechanism in each joint allows the manipulator to be controlled by only three wires. Modeling the dynamics of this manipulator presents an inherent complexity due to its closed-loop structure and kinematic constraints. In the first part of this paper, the inverse kinematics of the manipulator, which consists of position, velocity, and acceleration, is studied. In the second part, the inverse and forward dynamics of the manipulator is formulated based on... 

To have a complete model of a thunniform Fish-Robot, models of both body and tail are required. The dynamic model of the body is developed according to the parameters of a thunniform Fish-Robot built in MIT University, while, as the main part of this paper, the dynamic model of the tail is developed using fuzzy logic. Using experimental data and table look-up scheme, a fuzzy black box is introduced that gives the value of thrust force generated for any value of the Fish-Robot's input parameters: frequency of tail oscillation, amplitude of tail oscillation and speed of the Fish-Robot. In the second part, a trajectory fuzzy controller is designed for the Fish-Robot. The output of trajectory... 

The subject of modeling and stability analysis of dc-dc resonant converters is still a challenge. The conventional large signal nonlinear model of the resonant converter is derived using the sinusoidal approximation and averaging followed by linearization about an operating point. Models obtained with such method involve considerable approximation, and produce results that are limited for higher performance designs. Therefore, it is essential to investigate the stability of the resonant converters using a more sophisticated model. Because of semiconductors switching, dc-dc resonant converters are intrinsically hybrid systems consist of discrete input and continuous states. The complexity of... 

This paper deals with proportional stabilization and closed-loop step response identification of the fractional order counterparts of the unstable first order plus dead time (FOPDT) processes. At first, the necessary and sufficient condition for stabilizability of such processes by proportional controllers is found. Then, by assuming that a process of this kind has been stabilized by a proportional controller and the step response data of the closed-loop system is available, an algorithm is proposed for estimating the order and the parameters of an unstable fractional order model by using the mentioned data  

The objective of this paper is to expand the concept of hybrid modeling and control in power electronics area. A new precise and non-averaged model of a DC-DC boost converter is developed on the basis of Mixed Logical Dynamical (MLD) systems, and the approach is extended by a new version of such systems which is called as Extended Mixed Logical Dynamical (EMLD) systems in this paper. A Model Predictive Controller (MPC) based on the Mixed Integer Quadratic Programming (MIQP) is designed for the MLD and EMLD models of the DC-DC boost converter considering all possible dynamics in Continuous and Discontinuous Conduction Modes of operations (CCM-DCM). The simulation results show the satisfactory... 

This paper presents closed loop simulation of a CMOS-MEMS force sensor for biomedical applications employing an optimal proportional-integral-derivative controller. Since the dynamic behavior of the sensor under investigation is nonlinear the iterative feedback tuning approach was proposed for optimal gains tuning of the proposed controller. Simulation results presented in this research illustrate that the proposed controller suppresses the undesired in-plane vibration induced by environment or gripper 40 times faster than the nonlinear controller proposed in the literature. To suppress the maximum input disturbance the maximum voltage was approximately 18 V which was less than the pull-in... 

Objective: The objective of this paper is to develop a hierarchical two-level power system load frequency control. Design: At the button level, standard PI controllers are utilized to control area's frequency and tie-line power interchanges. At the higher layer, model predictive control (MPC) is employed as a supervisory controller to determine the optimal set-point for the PI controllers in the lower layer. The proposed supervisory predictive controller computes the optimal set-points such that to coordinate decentralized local controllers. Blocking and coincidence point technology is employed to alleviate the computational effort of the MPC. In order to achieve the best closed loop... 

In this paper, the parameters of a 4D Lü hyper-chaotic system are identified via synchronization of two identical systems. Unknown parameters of the drive system are identified by an adaptive method. Stability of the closed-loop system with one state feedback controller is studied by using the Lyapunov theorem. Also the convergence of the parameters to their true values is proved. Then a fractional adaptation law is applied to reduce the time of parameter convergence. Finally the results of both integer and fractional methods are compared  

In this study, control strategies based on time-varying LQR, Lyapunov-Floquet transformation (LFT), backstepping, feedback linearization, and constant gain feedback control are implemented for the linearized time periodic equations of spacecraft relative motion when the reference orbit is elliptic. Also, natural and nonnatural leader-follower two-spacecraft formations are studied. The stability of the closed-loop response, the control effort required, and the settling time are investigated and compared for all control strategies. Furthermore, using constant gain feedback, the estimated region of attraction of the closed-loop system is obtained analytically  

The automatic landing of a quadrotor is often associated with model uncertainties, measurement noises, and ground effect phenomenon. To mitigate these challenges, the accurate estimation of states especially the height above the ground, and its rate of change is vital. Moreover, the error of ground effect model can also be estimated and compensated during landing. In this paper, the recently developed continuous ant colony filter is implemented for integrated estimation of states and parameters. The estimated states are used in height control loop. To investigate the closed loop performance of the filter, two control strategies, a classical proportional-integral-derivative controller and a... 

In this paper, the problem of boundary stabilization of a vibrating non-classical micro-scale Euler-Bernoulli beam is considered. In non-classical micro-beams, the governing Partial Differential Equation (PDE) of motion is obtained based on the non-classical continuum mechanics which introduces material length scale parameters. In this research, linear boundary control laws are constructed to stabilize the free vibration of non-classical micro-beams which its governing PDE is derived based on the modified strain gradient theory as one of the most inclusive non-classical continuum theories. Well-posedness and asymptotic stabilization of the closed loop system are investigated for both cases... 

In non-classical micro-beams, the strain energy of the system is determined by the non-classical continuum mechanics. In this study, we consider a closed-loop control methodology for suppressing the vibration of non-classical microscale Euler-Bernoulli beams with nonlinear electrostatic actuation. The non-dimensional form of the governing nonlinear partial differential equation of the system is introduced and converted into a set of ordinary differential equations using the Galerkin projection method. In addition, we prove the observability of the system and we design a state estimation system using the extended Kalman filter algorithm. The effectiveness and performance of the proposed... 

Pulsating heat pipes (PHPs) are interesting heat transfer devices. Their simple, high maintaining, and cheap arrangement has made PHPs very efficient compared to conventional heat pipes. Rotating closed loop PHP (RCLPHP) is a novel kind of them, in which the thermodynamic principles of PHP are combined with rotation. In this paper, effect of rotational speed on thermal performance of a RCLPHP is investigated experimentally. The research was carried out by changing input power (from 25. W to 100. W, with 15. W steps) and filling ratio (25%, 50%, and 75%) for different rotational speeds (from 50. rpm to 800. rpm with an increment of 125. rpm). The results presented that at a fixed filling... 

Fault detection (FD) in power electronic converters is necessary in embedded and safety critical applications to prevent further damage. Fast FD is a mandatory step in order to make a suitable response to a fault in one of the semiconductor devices. The aim of this study is to present a fast yet robust method for fault diagnosis in nonisolated dc-dc converters. FD is based on time and current criteria which observe the slope of the inductor current over the time. It is realized by using a hybrid structure via coordinated operation of two FD subsystems that work in parallel. No additional sensors, which increase system cost and reduce reliability, are required for this detection method. For... 

Five different approaches are presented to assign characteristic ratios for commensurate fractional order systems having order in (0,0.5]. Through the indirect methods, a closed-loop or plant transfer function is converted to a commensurate order one with an order greater than 0.5 so that the previously designed CRA method by the authors is applicable. The first method among the proposed direct ones is based on increasing the order of the desired closed-loop transfer function that allows the employment of positive characteristic ratios. In the second method the closed-loop response is sped up by augmenting an appropriate zero. The final method uses negative characteristic ratios to reach the... 

This paper considers a closed-loop system consisting of a fractional/integer order system and a fractional PID controller. Assuming that the uncertain coefficients of the fractional PID controller lie in some known intervals independently (i.e. that controller is a member of an interval family), the paper presents some easy to use theorems to investigate the robust bounded-input bounded-output stability of the resultant closed-loop system. Moreover, a finite frequency bound required in drawing the related graphs has also been provided. Finally, some numerical examples are presented to illustrate the results  

High throughput AES encryption/decryption is a necessity for many of modern embedded systems. This article presents a high performance yet cost efficient AES system. Maestro can be used in a wide range of embedded applications with various requirements and limitations. Maestro is about one million times faster than the pure software implementation. The Maestro architecture is composed of two major components; the soft processor aimed at system initialization and control, and the hardware AES engine for high performance AES encryption/decryption. A ten stage implicit pipelined architecture is considered for the AES engine. Two novel techniques are proposed in design of AES engine which enable... 

In this study, performance of a flat plate solar collector operating in conjunction with a closed-loop pulsating heat pipe is investigated experimentally. The experiments were carried out in Yazd, Iran. The experimental setup consisted of a flat plate solar collector, pulsating heat pipe, and a tank. The pulsating heat pipe's evaporator is located inside the flat plate collector. In order to investigate the effect of the evaporator length on the efficiency of the system, three different length collectors are manufactured in the evaporating section. In addition, the effects of the pulsating heat pipe filling ratio, inclination angle, and flow rate are investigated for each collector... 

Kinematic control of a special hyper-redundant manipulator with lockable joints is studied. In this manipulator, the extra cables are replaced by a locking system to reduce the weight of the structure and the number of actuators. This manipulator has discrete and continuous variables due to its locking system. Therefore, a hybrid approach has been adopted in control. At first the forward kinematics and velocity kinematics of this manipulator are derived, and then a novel closed-loop control algorithm is presented. This algorithm consists of decision making, an inner loop controller, and kinematic calculation blocks. The decision making block is the logical part of the control scheme in which...