Sharif Digital Repository

In this research, the issue of outsourcing control calculations to servers or external computing parties for non-ideal situations has been discussed. Due to the confidentiality of the information of the control systems, it is necessary to guarantee and maintain the privacy of the data from sensors to the actuators. In this research, secure multi-party computation using secret sharing has been utilized to establish the privacy of these data and simultaneously outsource control computing. In other words, the goal is to design a secure controller by means of secure multi-party computations. One of the most important challenges in the design of controllers that use communication channels to send... 

This dissertation investigates the detection of false data injection attacks in largescale residential energy grids. A typical multi-micro-grid framework is investigated by considering the geographical dispersion of equivalent models, wherein each microgrid is assumed as an agent and managed by a local aggregator. Furthermore, a fully distributed Nash equilibrium seeking algorithm in the partial-decision information scenario is proposed, where each microgrid estimates the actions of all the microgrids by relying only on the information exchanged with some neighbors over a communication network. To effectively reduce unnecessary signal transmission among the agents, an adaptive algorithm,... 

In this dissertation, a data-driven model predictive control (MPC) algorithm has been developed to control unknown linear time invariant systems. This algorithm only needs past measured input-output data of the system and an upper bound on the order of the system to derive the system output to a desired value. To improve the transient response of the system, we define two filters on the performance and the effort terms of cost function of the optimization problem. Moreover, the Hankel matrices used in the optimization problem are updated online based on a multi-step event-triggered MPC scheme to deal with uncertainties and disturbances. With this method, the computational load of this... 

The stability of dynamic systems has long been discussed in the theory of control and many people and experts have researched in this field and important results have been obtained from their research. In the real world, systems stability is the premise of controlling their behavior. In fact, systems that are unstable will not be controllable without stability. Therefore, the stability of the systems is discussed and at the same time the control expectations of the system will be raised. The systems of the surrounding world behave nonlinearly; Therefore, their exact stability is not debatable with linear approaches and requires stronger mathematics and attention to specific behaviors of... 

Due to conspicuous increases in shopping and goods transportation in this unbridled world, a significant part of companies’ final interest and final cost are related to their distributions of goods. Meanwhile, because of practical constraints of service hours and service distances, logistics companies usually build multiple depots to serve a great number of dispersed customers. Hence, multi-depot vehicle routing problems (MDVRP) win more and more engineers’ and companies’ attention to thrift their cost by using optimization methods. Considering NP-hardness of MDVRP and the lack of optimal solution derived by heuristic and meta-heuristic approaches in the large scale problems, in this... 

With the rapid increase in the number of vehicles and the limitations on the extension of transportation network infrastructure, the need for utilizing proper methods to reduce traffic congestion has become increasingly important. One way to reduce traffic congestion is to control the signal splitting of traffic lights. Model predictive control (MPC) has been utilized so far by using different models of traffic flow dynamics in this field. Due to the high computational effort of MPC at each step time, the real-time implementation for large-scale networks has become a big challenge. Store-And-forward (SAF) is one of the traffic flow models that, due to its simplicity, makes it possible to... 

This thesis is related to the identification and design of a robust controller for an electrohydrodynamic printer system. As an emerging technology, this printer uses a strong electric field to deliver fluid ink from various conductive materials to the substrate. Modeling this system is complex due to the effect of different variables on its performance. In this project, first a simplified model with numerical solution data of the COMSOL model that is validated experimentaly is proposed. Then, by presenting a new control method that is a variant of an active disturbance rejection control baesd on extended state observer has been controlled. The new control method is actually an amendment to... 

Electric vehicles (EVs) will be used rampantly in future transportation system. Although the uncontrolled charging of these EVs will be threatening for the stability and sustainability of the grid, a well-suited energy trading policy may provide a number of beneficial services to the grid as well as preserving the sustainability of the system along with heightening the performance of operation. In this paper, by taking advantage of block rate tariff, a wholesale pricing policy is introduced. A multi-objective approach is utilized to address the cost reduction and load levelling services, concurrently, in order to guarantee the profits of the both the grid and EVs. Due to the high... 

In this paper, an energy management problem of a distribution system is studied. The energy trading among a distribution company and some aggregators controlling flexible loads and electric vehicles is modeled as a large-scale Nash bargaining problem. A distributed approach is proposed using the alternating direction method of multipliers decomposition technique, to keep privacy of traders and reduce calculation complexities. We prove that the proposed method admits a Nash bargaining solution. Since the participants' information is not available beforehand, we design an MPC-based algorithm to overcome system uncertainties. To verify the proposed approach a numerical scenario has been... 

Over the past two decades, the production of ultra-light drones has increased dramatically. These aircraft are used in applications such as filming, surveying, etc. One of the most important goals is to fly them for a long time. From time immemorial, a lot of work has been done to get such birds to fly, but nothing has ever been done on their engines and propellers, and they have always been considered ideal models (in other words, their efficiency is a bit ideal). In this dissertation, the main purpose is to study some of these sets and to obtain the flight time of a particular drone. First, a low-velocity wind tunnel was built to examine these complexes, then we tested these complexes... 

In this thesis, computational load reduction in linear matrix inequality based model predictive control for nonlinear multi-input systems is studied. The main idea is decomposing the system into several smaller interacting subsystems and computing each control input separately. The main challenge is how to consider the effects of interactions among subsystems in the control design. Three approaches are investigated in this thesis. In the first approach, a static approximation of the effects of other subsystems is augmented in the local model of each subsystem, to improve the closed loop performance than fully decentralized methods. In the second approach, considering the mutual interactions... 

The emergence of Autonomous Vehicles (AVs) provides the opportunities to ameliorate traffic congestion while increasing safety. AVs, using the vehicle to vehicle and vehicle to infrastructure communication, can gather and infer the information of adjacent vehicles and traffic flow. The objective of this article is to develop a cooperative control method to manipulate AVs longitudinal and lateral movements in order to enhance macroscopic features of the mixed traffic flows. In this paper, we propose a potential function to control longitudinal movement of AVs considering their physical constraints. The developed controller provides an optimal, collision-free car following by minimizing the... 

The maximum number of oscillation frequencies which can be generated in a linear integer order system at the steady state is the half of its inner dimension. In this thesis, we seek the using of fractional order delayed systems with minimum order to produce maximum number of oscillation frequencies. We found a relation between the system parameters and the oscillation frequency and then adjust the system’s coefficients so that all the roots of the characteristic equation, except the roots on the imaginary axis, lie on the left-hand side of the imaginary axis. Taking into account the diagonal and triangular lower for the state space matrices of fractional order systems with one delay, we... 

In this work, we try to develop a method for searching for an object which is known to us and also returning it back where the search was begun, through shortest possible path. The surrounding environment was assumed unknown and only a stereo camera and an IMU exist to work with. The proposed method was developed in Linux using GPU and with C++ language and also achieved 58 fps. Parallel programming was utilized in different parts of the algorithm and obstacle avoidance is guarranteed. The surrounding environment and obstacles are assumed changing over the time  

Recently, there has been a surge of research activities in the area of networks in the systems and control community. One foundational class of questions on networked systems pertains to their controllability. While there are classical tests to check the controllability of linear time-invariant (LTI) systems, their applications to large-scale networks is numerically infeasible. Indeed, finding a minimum cardinality set of input nodes that ensure the controllability of a network is NP-hard. Moreover, when the interaction strengths along the edges of a network are unknown, the classical controllability test cannot be applied. To overcome these issues, an alternative set of approaches involves... 

In this thesis, partitioning of multi inputs nonlinear dynamical systems into distinct subsystems with the goal of designing decentralized, distributed, and cooperative predictive controllers for reducing the computational load and time in practical implementations has been studied. At first, the concept of dynamical systems graph is introduced and the problem of decomposing nonlinear dynamical systems into distinct subsystems has been converted to the problem of decomposing dynamical systems graph into separate subgraphs. The proposed method for decomposition of the dynamical system graph is represented as a linear integer optimization programing where the separated subgraphs is obtained by... 

In this thesis, the general form of descriptor linear systems with time-delay is studied. First, an approach is presented to analyze the stability of descriptor linear systems with commensurate time-delay. Through this approach, not only stable and unstable regions of the system can be determined, but also the number of unstable roots in each unstable region can be calculated. Additionally, a decomposition approach is proposed, which transforms the descriptor systems with time-delay to normal time-delay systems with a lower order. As a result, a large number of methods which are only available for normal systems with time-delay can be utilized for descriptor systems with time-delay. Also,... 

Many processes and real world systems indicate nonlinear behavior and operate either naturally in multiple regions or in a wide range of operation space. Modelling and control of these systems by nonlinear methods needs to have a deep insight. Furthermore, the nonlinear methods leads to complexity issues. To overcome these problems, multi-model methods are introduced which consist of two steps, decomposition and combination. In decomposition step, the complex system is divided into a set of simple models; in the combination step, the behavior of local models are combined. How to decompose to local models and how to combine them are two main questions in this area which not answered... 

A control system capable of tolerating system malfunctions while maintaining an acceptable level of performance is referred as fault tolerant control system. The constraints on the amplitude of input control signals limit the domain of attraction even for linear models. Ignoring this fact may lead to an unsatisfactory performance and even closed loop instability. Designing the controller such that the domain of attraction is maximized has been an attractive topic for researchers. On the other hand, persistent disturbances always play an essential role in the real word systems. Designing the controller in a way such that the effect of such disturbances is attenuated is another challenging... 

In recent decays, multiple model controllers have been attracted much attention due to their essential ability to control of non-linear systems with wide operating ranges. Number and location of models are two important factors. In this research an algorithm for determining number of models and their locations has been proposed which can be counted as an extension to existing algorithms. Utilizing the proposed algorithm, the minimum number of models which achieve closed-loop stability can be determined. If transient response of non-linear system with these models be not satisfactory, the number of models are increased by one using Binary Search method, and consequently the location of models...