Sharif Digital Repository

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... 

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... 

In this paper, a new model reference adaptive controller (MRAC) for uncertain switched linear systems is developed. A class of uncertain switched linear systems with parametric mismatched and input matched uncertainties, control input effectiveness and unmodeled dynamics is studied in this paper. The difference in input matrix for different switching modes which means the input channel degradation is investigated through this paper. By using common Lyapunov function method and developing new linear matrix inequality based sufficient conditions, uniform ultimate boundedness of the reference tracking error is guaranteed by switched MRAC and by using a novel nonlinear controller term, the size... 

Purpose - The purpose of this paper is to propose a supervisory command-to-line-of-sight guidance law with lead angle which keeps the missile flight within the tracking beam. Design/methodology/approach - A nonlinear supervisory controller is designed and coupled with the main sliding mode controller in the form of an additional control signal. The supervisory control signal is activated when the beam angle constraint goes to be violated. Initially a supervisory controller is designed using nonlinear control theory. Subsequently the main tracking controller is designed using sliding mode approach which forces the missile to fly along the desired line-of-sight. The stability of the... 

The paper presents the application of a rule- based control scheme for an Advanced Static Var Compensator (ASVC) to improve power system transient stability. The proposed method uses a current reference, based on the Transient Energy Function (TEF) approach. The proposed scheme provides, also, a continuous control of the reactive power flow. The performance of the proposed approach is compared with that of a system using a conventional control method and of a system without ASVC. A single-machine system and an IEEE three machine system are used to verify the performance of the proposed method. © Sharif University of Technology  

This paper proposed a new curvature based path-description method for path-generation of planar mechanism, in which the position vector of a point on coupler, which follows most closely a predefined path, is directly calculated as a function of coupler motion properties. In addition this curvature based method makes it possible to define an objective function independent of rotation and translation transformations. Therefore, in this method, initial position, orientation, and coupler point vector parameters are not the optimization variable. These five parameters could be calculated as a function of other design parameters and they are found when these optimal values are obtained. Reducing... 

Presented in this paper are a method, named the Dynamic Rule Prediction (DRP), which predicts the behavior of a system and its application in designing a controller. The aim of the study is to overcome some of the limitations and shortcoming of the other modeling methods. The effectiveness of this method is verified. The controller based on DRP possesses two main features. It can control the system without any prior knowledge of the controlled plant. It is, also, superior as its high-speed prediction. This paper focuses on the robot manipulator controllers and applications of this approach in it  

An application of a new controller order reduction technique with stability and performance preservation based on linear matrix inequality optimization to an active suspension system is presented. In this technique, the rank of the residue matrix of a proper rational approximation of a high-order H∞controller subject to the H∞-norm of a frequency-weighted error between the approximated controller and the high-order H∞ controller is minimized. However, because solving this matrix rank minimization problem is very difficult, the rank objective function is replaced with a nuclear-norm that can be reduced to a semidefinite program so that it can be solved efficiently. Application to the active... 

Purpose - To devise a new technique to synthesise optimal feedback control law for non-linear dynamic systems through fuzzy logic. Design/methodology/approach - The proposed methodology utilizes the open-loop optimal control solutions (OCSs) of the non-linear systems for the training of the fuzzy system in the process of developing closed-loop fuzzy logic guidance (FLG). This is achieved through defining a set of non-dimensionalised variables related to the system states. Findings - FLG is capable of generating closed-loop control law for the non-linear problem investigated. Since the proposed fuzzy structure is independent of the system equations, the approach is potentially applicable to... 

In this paper, a new approach for controlling the sway angle of the load in trolley cranes is presented which is based on the flexibility of the cable and variation of its length by the time. The crane dynamics has been described by hybrid PDE and ODE equations which uses the PDE as the equations of motion for the flexible cable and ODE for those of the trolley and the load. The purpose of the controller is to transport the load to the desired position and to eliminate its sway angle at the destination. The control law is based on the Lyapunov's second method. The efficiency of the proposed controller is demonstrated via various simulations  

This paper presents a generic vector model for the brushless doubly-fed machine (BDFM) with a nested-loop rotor. The vector model is presented for a generic p1/p2 pole-pair BDFM which may have any number of loops per nest. The vector transformations utilized in the derivation of the vector model are provided in general form such that the model can be represented in any appropriate reference frames according to the specific application of the model, such as BDFM analysis, simulations, or control system synthesis. The derived vector model benefits from the feature of reduced order in comparison with the coupled-circuit model, which is the most detailed model for the BDFM, while maintaining the...