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optimal-control
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Optimal trajectory planning for flight through microburst wind shears
, Article Aerospace Science and Technology ; Volume 15, Issue 7 , October , 2011 , Pages 567-576 ; 12709638 (ISSN) ; Kiani, M ; Hassanpour, A ; Sharif University of Technology
2011
Abstract
Microburst wind shear is a potential hazard for aviation safety, especially in some crucial phases of flight like take-off and landing. Optimal trajectories could be useful for suitable retrieval of transport aircrafts encountering microburst. These types of trajectories are investigated in this paper for landing phase in two scenarios of escape and landing utilizing the most recent realistic analytical model of the microburst. In this regard, a set of complete six degrees of freedom aircraft's equations of motion is taken in a variation formulation of this problem. This approach is particularly useful for determination of optimal escape or approach trajectories constrained with respect to...
Distributed optimal control using an efficient method for decomposition
, Article 2017 25th Iranian Conference on Electrical Engineering, ICEE 2017, 2 May 2017 through 4 May 2017 ; 2017 , Pages 661-666 ; 9781509059638 (ISBN) ; Farhadi, A ; Sharif University of Technology
Abstract
This paper is concerned with a new method for decomposing large scale systems into disjoint neighborhoods of subsystems with specific size determined a priori for managing communication load of a Jacobi based distributed optimal control method. The proposed decomposition method clusters subsystems into disjoint neighborhoods based on the strength of control inputs interaction between subsystems. The proposed method is a new method and uses the time response of system for decomposition. Using extensive computer simulation it is illustrated that this method finds the best decomposition. © 2017 IEEE
Optimal stability of a redundant mobile manipulator via genetic algorithm
, Article Robotica ; Volume 24, Issue 6 , 2006 , Pages 739-743 ; 02635747 (ISSN) ; Naderi, D ; Eslami, S ; Sharif University of Technology
2006
Abstract
Once the path of the vehicle and the desired task of the end-effector are predefined, in order to apply the optimal stability criterion, the manipulator should be redundant. In this paper, the goal is to find the position, angular velocity, and angular acceleration of the redundant link of the manipulator such that the entire system becomes optimally stable. By considering the full dynamic interaction between the manipulator and its vehicle, the stability issue becomes more complex. There are some measures of stability and one of them is the tire's upward force. This measure tries to equalize the upward forces of the tires that lead to optimal stability and better steer-ability. Optimizing...
A fast flux search controller for DTC based induction motor drives
, Article PESC Record - IEEE Annual Power Electronics Specialists Conference ; Volume 2005 , 2005 , Pages 739-744 ; 02759306 (ISSN); 0780390334 (ISBN); 9780780390331 (ISBN) ; Zolghadri, M. R ; Emadi, A ; Sharif University of Technology
2005
Abstract
In this paper, a flux search controller is proposed to increase the efficiency of a direct torque controlled induction motor with light load. The reference flux value is determined through a two stage minimization algorithm with the amplitude of the stator current as the objective function. In the transient state, a great flux step is used to speed up the convergence. In the steady state, a noise cancellation algorithm is used to let using small flux step and improves the steady state behavior of flux controller. Simulation and experimental confirm the fast dynamics of the proposed method and its superiority compared to the other optimal flux search controllers. © 2005 IEEE
A novel approach to coordination of large-scale systems; Part I - Interaction prediction principle
, Article 2005 IEEE International Conference on Industrial Technology, ICIT 2005, Hong Kong, 14 December 2005 through 17 December 2005 ; Volume 2005 , 2005 , Pages 641-647 ; 0780394844 (ISBN); 9780780394841 (ISBN) ; Sharif University of Technology
2005
Abstract
Coordination strategies in large-scale systems are mainly based on two principles; Interaction Prediction Principle and Interaction Balance Principle. In this paper, which consists of two parts, the concept of coordination is introduced within the framework of two-level large-scale systems, and two new approaches for coordination based on Interaction Prediction Principle and Interaction Balance Principle have been presented. The new strategies have much faster convergence rate than the previously suggested classical methods. They extremely reduce the number of iterations required for obtaining the overall optimal solutions. The efficacy and advantage of the proposed approaches, in compare to...
Design of car active suspension systems to obtain desired performance on reducing effect of road excitation on human health
, Article DETC2005: ASME International Design Engineering Technical Conferences and Computers and Information in Engineering Conference, Long Beach, CA, 24 September 2005 through 28 September 2005 ; Volume 6 A , 2005 , Pages 383-390 ; 0791847438 (ISBN); 9780791847435 (ISBN) ; Ahmadian, M. T ; Sharifi Sedeh, R ; Sadati, N ; Sharif University of Technology
American Society of Mechanical Engineers
2005
Abstract
Advent of passenger cars has caused people to use them for more efficiency in their performance and wasting less time. Problems, however, still exist in them. For instance, since people travel with cars, their human bodies undergo in fatigue, restlessness, and sometimes health problems. Human body reaction under external vibration depends on the amplitude, frequency, and acceleration of the applied external excitation. These limitations which are usually announced by the bureau of standards imply the necessity of control of amplitude, vibration, frequency, and acceleration received by human body due to cars passing humps and bumps. In this paper, a quarter car model with active suspension...
Online optimal flux controller for DTC based induction motor drives
, Article IECON 2004 - 30th Annual Conference of IEEE Industrial Electronics Society, Busan, 2 November 2004 through 6 November 2004 ; Volume 2 , 2004 , Pages 1391-1395 ; Zolghadri, M. R ; Roye, D ; Emadi, A ; Sharif University of Technology
2004
Abstract
A flux search controller is proposed to achieve the best efficiency in a direct torque controlled induction motor with light load. The reference flux value is determined through a minimization algorithm with stator current as objective function. Experimental results show that using motor current instead of motor input power as the objective function causes better performance. © 2004 IEEE
A new hierarchical approach for optimal control of robot manipulators
, Article 2004 IEEE Conference on Robotics, Automation and Mechatronics, 1 December 2004 through 3 December 2004 ; 2004 , Pages 306-311 ; 0780386469 (ISBN); 9780780386464 (ISBN) ; Babazadeh, A ; Sharif University of Technology
2004
Abstract
In this paper, a new approach for optimal control of robot manipulators is presented. For this purpose, the system is considered as a two-level large-scale system where a gradient based coordination strategy is used to coordinate the overall system. This is achieved within a decomposition-coordination framework, where the robot manipulator is first decomposed into several sub-systems in such a way that each sub-system consists of several consecutive links and joints. With the aim of optimization, the control problem is first decomposed into m sub-problems, at the first level, where each sub-problem is solved using a gradient optimization method. Then, by using a new methodology which is...
Two-level robust optimal control of large-scale nonlinear systems
, Article IEEE Systems Journal ; Volume 9, Issue 1 , 2015 , Pages 242-251 ; 19328184 (ISSN) ; Rahmani, M ; Saif, M ; Sharif University of Technology
Abstract
Finding an optimal control strategy for a nonlinear uncertain system is a challenging problem in the area of nonlinear controller design. In this paper, a two-level control algorithm is developed for robust optimal control of large-scale nonlinear systems. For this purpose, using a decomposition/coordination framework, the large-scale nonlinear system is first decomposed into several smaller subsystems, at the first level, where a closed-form solution as a feedback of states and interactions is obtained to optimize each subsystem. At the second level, a substitution-type prediction method, as a coordination strategy, is used to compensate the nonlinear terms of the system and to predict the...
Effects of structural configuration on vibration control of smart laminated beams under random excitations
, Article Journal of Mechanical Science and Technology ; Volume 24, Issue 5 , 2010 , Pages 1119-1125 ; 1738494X (ISSN) ; Sharif University of Technology
Abstract
The influence of structural configuration on vibration responses of smart laminated beams under random loading is studied. The effect of laminate configurations and locations of sensors/actuators in the smart system is also investigated. The layer-wise approximation for displacement and electric potential is utilized to construct the finite element model. The closed-loop control response is determined through an optimal control algorithm based on the Linear Quadratic Regulator (LQR). The correlation coefficient between the input random force and the applied actuating voltage for various configurations is also computed. It is revealed that for softer configurations, the correlation...
RedQueen: an online algorithm for smart broadcasting in social networks
, Article WSDM 2017 - Proceedings of the 10th ACM International Conference on Web Search and Data Mining, 2 February 2017 ; 2017 , Pages 51-60 ; 9781450346757 (ISBN) ; Upadhyay, U ; Rabiee, H. R ; Gomez Rodriguez, M ; Sharif University of Technology
Association for Computing Machinery, Inc
2017
Abstract
Users in social networks whose posts stay at the top of their followers' feeds the longest time are more likely to be noticed. Can we design an online algorithm to help them decide when to post to stay at the top? In this paper, we address this question as a novel optimal control problem for jump stochastic differential equations. For a wide variety of feed dynamics, we show that the optimal broadcasting intensity for any user is surprisingly simple - it is given by the position of her most recent post on each of her follower's feeds. As a consequence, we are able to develop a simple and highly efficient online algorithm, RedQueen, to sample the optimal times for the user to post....
Muscles force patterns prediction and joint reactions determination during 3D spine movements by means of optimal control theory
, Article 2008 International Conference on Control, Automation and Systems, ICCAS 2008, Seoul, 14 October 2008 through 17 October 2008 ; December , 2008 , Pages 548-553 ; 9788995003893 (ISBN) ; Pourtakdoust, H ; Vossoughi, G. R ; Kim, J. Y ; Parnianpour, M ; Sharif University of Technology
2008
Abstract
Modeling the spine behavior plays a key role in understanding mechanisms leading to spinal disorders and injuries. The goal of this article is to develop a new model to obtain 3D spine movement patterns. High degrees of freedom of the system, a great many of muscles involved in the spine movements and its unstable intrinsic behavior make the control problem more difficult. New theories in computational motor control suggest optimal control as a useful tool for modeling Central Nervous System (CNS) to provide appropriate control signals while it computes the neural interactions with biological sensors. Therefore, CNS is modeled as an optimal controller. Our simulations illustrate the movement...
Optimal Trajectory Correction for Hazardous Near-Earth Asteroids
,
M.Sc. Thesis
Sharif University of Technology
;
Zohoor, Hassan
(Supervisor)
;
Sayyadi, Hassan
(Supervisor)
Abstract
The collision of moderately large asteroids and comets also referred to as Near-Earth Objects (NEO's) with earth would have catastrophic consequences. Such events have occurred in the past and may occur again in the future. However, for the first time in known history, humanity may have the technology required to counter this threat. Methods studied for mitigation of this hazard are based on deflecting asteroid's trajectory and are normally divided into two basic categories: high energy impulsive methods, and long-duration low-thrust methods. Two parts of mission to be optimized are the trajectory of spacecraft to reach the target and the deflection strategy which could be analyzed by the...
Using Optimal Control for Dynamic Pricing under Learning Effect of Supply and Demand
, M.Sc. Thesis Sharif University of Technology ; Kianfar, Farhad (Supervisor)
Abstract
In this research a monopolist is considered which its object is maximization of profit during a predetermined period. Optimal control theory is used as a tool for determining of optimal trend for control variables. Price, warranty length and production rate are considered as control variables and cumulative demand and production are considered as state variables. Learning effect in production side and demand side are entered in the model too. In the demand side, learning effect shows its influences with movement of market from diffusion phase to saturation phase. In diffusion phase the demanded quantity of productions increases by increase of cumulative demand, on the contrary in the...
Dynamic Pricing and Optimal Warranty and Advertisement Policy For High-Tech Products
, M.Sc. Thesis Sharif University of Technology ; Kianfar, Farhad (Supervisor)
Abstract
This study frames optimal policies for determining price , warranty length and Advertisement rate when free replacement of defective items is the business policy and the demand is dependent on price, warranty, advertisement and cumulative sales for high-tech products which have functional aspects. We apply optimal control theory to a profit-maximization model that takes into consideration the expected warranty cost per item. The maximization of market values is based upon a pre-determined life cycle and spans across both expansion and saturation phases of the market. We further investigate the optimal policies for an exponential lifetime distribution, when the demand function is set by...
Evaluation of Trunk Movement System Strategies through the Concept of Muscle Synergies
, M.Sc. Thesis Sharif University of Technology ; Firoozbakhsh, Keikhosrow (Supervisor) ; Parnianpour, Mohammad (Co-Advisor)
Abstract
In this study, by dividing spine motion in two part, ordinary movement and initial-final accelerated movement, the commands of CNS are evaluated by optimization methods to find synchronous and time varying synergies. Spine, which is a complex structure of vertebrae and cartilage, has been modeled by a 3D inverted pendulum with a ball and socket joint at L4/L5 incorporated with 18 muscle fascicles. Planning of point-to-point spine motion is performed by optimal control method in combined with cost function of kinematics and kinetic features that available in spine structure. In the second step, coactivation of muscles is predicted by utilizing static optimization along with stability...
Electromagnetic Formation Flying of Space Tether
, M.Sc. Thesis Sharif University of Technology ; Asadian, Nima (Supervisor)
Abstract
In this thesis a novel non-rotating space tethered configuration is introduced which its relative positions are 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 advantage of using equations in the Cartesian coordinate system over presenting the equations of satellite formation plane angles is the appearance of gravity gradient and Earth’s magnetic field effects. The tether is assumed to be mass-less and...
Pricing New Product with Social Effects Consideration
, M.Sc. Thesis Sharif University of Technology ; Shavandi, Hassan (Supervisor)
Abstract
The main purpose of this thesis, is the scrutiny of social influences on products sales and prices. That is what probable effects can be imposed on the amount of sale and price of products as a result of customer's satisfaction or dissatisfaction. In this research pricing of a new product is considered which is produced and supplied through market in a monopolized manner for a specific time period. At the first period, people purchase the product given factors such as price, quality, etc. a part of whom, put comments about their experience regarding the product quality on social networks. In following periods, alongside with aforementioned factors, new purchasers also consider positive or...
Optimal Landing Ground_run for FAR_23 Aircraft
, M.Sc. Thesis Sharif University of Technology ; Malaek, Mohammad Bagher (Supervisor)
Abstract
As demand for floght has been incrased, a critical questin to pose is that is it economic to use larger Ailplanes or smaller Airplanes with higher flight frequency should be use. It is self evident that in a large Airplane the whole seats can not be accupied in all cases. Conversly, in small Airplanes, in most cases the seats are accupied but for aqual demand there most be more flights.In order to increase the number of flights, new methods should be used in such a way that smaller Airplanes live the Runway as soon as possible.In this project with modelling all effective factor regarding to Landing of a commercial FAR_23 Airplane, the Landing distance and thr erquired time for living the...
3D Trapping, Cooling of a Nanoparticle and Optimal Control of a Heat Engine in a Quantum Optomechanical System
, Ph.D. Dissertation Sharif University of Technology ; Bahrampour, Alireza (Supervisor)
Abstract
In this dissertation, we propose and analytically investigate a scheme for effective three-dimensional cooling of a nanoparticle optically trapped in a Fabry-Perot cavity using multiple cavity modes. By employing active feedback cooling using amplitude modulation of cavity modes, our approach allows to access the UHV regime without the need for any additional means like an external tweezer or a radio-frequency trapping approach. For a set of feasible experimental parameters, we demonstrate that the cooling rates achievable are sufficient to overcompensate recoil heating. Therefore the approach is suited to trap a particle for indefinite times at UHV pressures, where air damping cannot...