Sharif Digital Repository

In this paper, we consider a control strategy of multi-robot systems, or simply, swarms, based on emotional control technique. First, we briefly discuss a "kinematic" swarm model in n-dimensional space introduced in an earlier paper. In that model, motion of every swarm member is governed by predefined inter-individual interactions. Limitations of every member's field of view are also considered in that model. After that, we consider a general model for vehicle dynamics of each swarm member, and use emotional control theory to force their motion to obey the dynamics of the kinematic model. Based on the kinematic model, stability (cohesion) analysis is performed and coordination controller.is... 

Under different loading conditions, the over-head cranes may experience a wide range of model parameters variation. A robust control strategy is developed to achieve the high positioning accuracy, short transportation time and suppression of swing angle for an uncertain over-head crane system. Over-head crane is modeled as a three degrees of freedom system and control problem is investigated for two cases: a system with a single control input (the force on trolley) and a system with two control inputs (the force on trolley and the torque on lifter). Regulator and observer systems are designed. To achieve the tracking objectives, an optimal robust controller is designed based on μ-synthesis... 

During the drug delivery process in chemotherapy, both of the cancer cells and normal healthy cells may be killed. In this paper, three mathematical cell-kill models including log-kill hypothesis, Norton-Simon hypothesis and Emax hypothesis are considered. Three control approaches including optimal linear regulation, nonlinear optimal control based on variation of extremals and H∞-robust control based on μ-synthesis are developed. An appropriate cost function is defined such that the amount of required drug is minimized while the tumor volume is reduced. For the first time, performance of the system is investigated and compared for three control strategies; applied on three nonlinear models... 

This paper proposes a control strategy for an islanded microgrid to effectively coordinate hybrid power source (HPS) units and to robustly control individual interfaced inverters under unbalanced and nonlinear load conditions. Cascaded H-bridge (CHB) multilevel inverters are flexibly deployed in order to enhance the power quality and redundancy. The HPS employs fuel cell (FC) as the main and supercapacitors (SC) as complementary power sources. Fast transient response; high performance; and high power density are the main characteristics of the proposed HPS system. The presented control strategy consists of a power management strategy for the HPS units and a voltage control strategy for the... 

The way central nervous system manages the excess degrees of freedom to solve kinetic redundancy of musculoskeletal system remains an open question. In this study, we utilise the concept of synergy formation as a simplifying control strategy to find the muscle recruitment based on summation of identified muscle synergies to balance the biomechanical demands (biaxial external torque) during an isometric shoulder task. A numerical optimisation-based shoulder model was used to obtain muscle activation levels when a biaxial external isometric torque is imposed at the shoulder glenohumeral joint. In the numerical simulations, 12 different shoulder torque vectors in the transverse plane are... 

When the network suffers from congestion, the core or edge routers signal the incidence of congestion through the active queue management (AQM) to the sources. The time-varying nature of the network dynamics and the complex process of retuning the current AQM algorithms for different operating points necessitate the development of a new AQM algorithm. Since the non-minimum phase characteristics of the network dynamics restrict direct application of the proportional-integral-derivative (PID) controller, we propose a compensated PID controller based on a new control strategy addressing the phase-lag and restrictions caused by the delay. Based on the unstable internal dynamics caused by the... 

In this paper, the participation of wind farms in load frequency control (LFC) is studied. A previously proposed macromodel for the wind farm is employed to regulate its output power. The wind farm including its proposed control strategy is incorporated into the conventional LFC model. The proposed LFC structure is able to dynamically maintain the system frequency at the nominal value against the power imbalances. To achieve proper transient response, the integral control parameter of the LFC controller is optimized using the genetic algorithm (GA). To verify the effectiveness of the proposed method, several simulation case studies are carried out. The results show that the wind farm can... 

In this paper, optimal approaches for controlling chaos is studied. The unstable periodic orbits (UPOs) of chaotic system are selected as desired trajectories, which the optimal control strategy should keep the system states on it. Classical gradient-based optimal control methods as well as modern optimization algorithm Particle Swarm Optimization (PSO) are utilized to force the chaotic system to follow the desired UPOs. For better performance, gradient-based is applied in multi-intervals and the results are promising. The Duffing system is selected for examining the proposed approaches. Multi-interval gradient-based approach can put the states on UPOs very fast and keep tracking UPOs with... 

Increase of nonlinear loads has led to the rise of harmonic currents, voltage distortion and imbalance in power systems. IEEE Std. 1459 proposes new definitions for electric power in sinusoidal, nonsinusoidal, balanced and unbalanced conditions which can be used for compensation of nonsinusoidal and unbalanced systems. Among different definitions, IEEE Std. 1459 proposes the new concept of effective apparent power and power factor which is more related to the real losses in a power system. In this paper, by expansion of definitions of IEEE Std. 1459, instantaneous forms of effective parameters are defined. Then, a new control strategy for a Shunt Active Power Filters (SAPFs) is defined based... 

Widespread use of sensitive loads in industries has required the need for high efficiency voltage regulators in order to provide continuous and fast dynamic adjustable AC voltage. This paper introduces a new control strategy to improve the response time and performance of a double stage switch mode regulator. The proposed strategy responds to input voltage variations quickly and improves the efficiency and performance of the circuit. Results of some simulations are presented and analyzed. Experimental tests on a laboratory prototype verify the excellent performance of the proposed system  

The complexity associated with musculoskeletal modeling, simulation, and neural control of the human spine is a challenging problem in the field of biomechanics. This paper presents a novel method for simulation of a 3D trunk model under control of 48 muscle actuators. Central pattern generators (CPG) and artificial neural network (ANN) are used simultaneously to generate muscles activation patterns. The parameters of the ANN are updated based on a novel learning method used to address the kinetic redundancy due to presence of 48 muscles driving the trunk. We demonstrated the feasibility of the proposed method with numerical simulation of experiments involving rhythmic motion between upright... 

This paper presents a control strategy for the autonomous (islanded) operation of a distributed generation (DG) unit. The DG unit supplies a balanced load through a voitage-sourced converter (VSC). To maintain the autonomous operation in the islanded mode, the DG unit should provide its dedicated load with a sinusoidal voltage with a constant magnitude and a constant frequency. The dynamic model of the islanded DG system is represented by a set of nonlinear equations. Since the objective is to regulate voltage and frequency of the islanded DG about their rated values, the nonlinear model is linearized about the operating point. The obtained linearized model represents a multivariable LTI... 

In this paper, a new control strategy is proposed to improve the performance of a wind generator system composed of a three-phase PMSG and a Back-to-Back three-phase to single-phase converter. With the use of the large inductance of the synchronous generator, the control method minimizes the generator torque ripple when the system supplies a single-phase load. The problem arises from the fact that the instantaneous power of a single-phase load is pulsating at the double of the system frequency. This paper tries to minimize the effect of this pulsating power on the PMSG torque without using a large capacitor on the DC link. Simulation results show the effectiveness of the proposed method. ©... 

Development of high frequency power electronic devices leads to high performance and flexible switch mode AC voltage stabilizers instead of traditional electromechanical types. This paper introduces a novel double stage topology for switch mode AC voltage regulators. The system produces a continuous adjustable isolated AC voltage providing a constant output voltage for sensitive loads. In order to simplify the control strategy, a symmetrical PWM is used. In contrast with conventional AC choppers, the proposed circuit does not need any snubber circuits or voltage and current sensors which leads to a simpler and more reliable circuit. Detailed analysis and simulation results show the... 

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... 

Under different loading conditions, the over-head cranes may experience a wide range of model parameters variation. A robust control strategy is developed to achieve the high positioning accuracy, short transportation time and suppression of swing angle for an uncertain over-head crane system. Over-head crane is modeled as a three degrees of freedom system and control problem is investigated for two cases: a system with a single control input (the force on trolley) and a system with two control inputs (the force on trolley and the torque on lifter). Regulator and observer systems are designed. To achieve the tracking objectives, an optimal robust controller is designed based on μ-synthesis... 

A decentralized servomechanism controller for islanded (autonomous) operation of radial connection of two distributed generation (DG) units is proposed in this paper. Each DG unit utilizes a voltage-sourced converter (VSC) for interface to its dedicated load. The DG units and the loads are to operate in the islanded mode of operation. Each DG unit regulates the voltage of its dedicated load in a decentralized manner. In this paper, it is first shown that the radial connection of two DG units in the islanded mode constitutes an interconnected composite system consisting of two subsystems. Moreover, the paper shows that the overall islanded system can be controlled by the local controllers,... 

In this paper, the Line-Modulated Fixed Off-Time method is used as the current control strategy for a Power Factor Corrector (PFC) pre-regulator. A zero voltage switching PWM (ZVS-PWM) auxiliary circuit is configured to perform ZVS in the switches. Soft commutation of the main switch is achieved without additional current stress. A significant reduction in the total conduction loss is achieved, since the circulating current for the soft switching flows only through the auxiliary circuit and a minimum number of switching devices are involved in the circulating current path .The proposed rectifier uses a single converter instead of the conventional configuration composed of a four-diode... 

In this paper, the design of a formation flight controller is investigated. Each vehicle in the formation is controlled by designing two separate control loops. The formation flight controller placed in the outer loop employs behavior-based control as a distributed control strategy to steer the vehicle by producing acceleration commands and the control system placed in the inner loop is to convert these commands to the actuator commands. Leader following architecture is applied to define the structure for the formation flight. To study the pragmatic issues of the proposed formation flight controller, it is implemented into multiple micro air vehicles which are modeled by a... 

This work deals with the problem of controlling the outlet temperature of a tubular heat exchanger system by means of flow pressure. The usual industrial case is to try to control the outlet temperature by either the temperature or the flow of the fluid, which flows through the shell tube. But, in some situations, this is not possible, due to the fact that the whole of system coefficients variation cannot quite be covered by control action. In this case, the system behavior must precisely be modeled and appropriate control action needs to be obtained based on novel techniques. A new multiple models control strategy using the well-known linear generalized predictive control (LGPC) scheme has...