Sharif Digital Repository

In this paper, a nonlinear adaptive impedance controller is proposed for UAVs equipped with a robot manipulator that interacts with environment. In this adaptive controller, by considering the nonlinear dynamics model of the UAV plus the robot manipulator in Cartesian coordinates, all of model parameters are considered to be completely uncertain and their estimation is updated using an adaptation law. The objective of the proposed adaptive controller is the control of manipulator's end-effector impedance in Cartesian coordinates to have a stable physical interaction. The adjustable Cartesian impedance is a desired dynamical relationship between the end-effector motion in Cartesian... 

Conventional models of cardiovascular system (CV) frequently lack required detail. Once utilized to study the heart function, these models focus primarily on the overall relationship between pressure, flow and volume. This study proposes a localized and regional model of the CV system. It utilizes non-invasive blood flow and pressure seed data and temporal cardiac muscle regional activation to predict the operation of the heart. Proposed localized analysis considers specific regions of the heart, namely base, mid and apex sections of the left ventricle. This modular system is based on a hydraulic electric analogy model, estimating desired parameters, namely resistance (R), compliance (C),... 

Many-core processors facilitate coarse-grained reliability by exploiting available cores for redundant multithreading. However, ensuring high reliability with reduced power consumption necessitates joint considerations of variations in vulnerability, performance and power properties of software as well as the underlying hardware. In this paper, we propose a power-efficient reliability management system for many-core processors. It exploits various basic redundancy techniques (like, dual and triple modular redundancy) operating in different voltage-frequency levels, each offering distinct reliability, performance and power properties. Our system performs Dynamic Redundancy and Voltage Scaling... 

In this paper, a new nonlinear robust adaptive impedance controller is addressed for Unmanned Aerial Vehicles (UAVs) equipped with a robot manipulator that physically interacts with environment. A UAV equipped with a robot manipulator is a novel system that can perform different tasks instead of human being in dangerous and/or inaccessible environments. The objective of the proposed robust adaptive controller is control of the UAV and its robotic manipulators end-effector impedance in Cartesian space in order to have a stable physical interaction with environment. The proposed controller is robust against parametric uncertainties in the nonlinear dynamics model of the UAV and the robot... 

Heat exchanger network synthesis (HENS) is one of the most efficient process integration tools to save energy in chemical plants. In this work, a new optimization framework is proposed for the synthesis of HENS, based on a genetic algorithm (GA) coupled with a commercial process simulator through the ActiveX capability of the simulator. The use of GA provides a robust search in complex and nonconvex spaces of mathematical problems, while the use of a simulator facilitates the formulation of rigorous models for different alternatives. To include the most common heat exchanger structures in the model, a promising superstructure has been used. Allowing nonisothermal mixing of streams in the new... 

Although modular linear flux-reversal permanent magnet motors are widely attractive for high reliability urban rail transit because of their advantages such as high power density, high reliability, low permanent magnet flux leakage problem, and improved fault-tolerant capability, they suffer from high thrust ripples. In this article the authors use a layer model for defining different optimization problems to improve thrust density, efficiency, and thrust ripples, independently and simultaneously. Design variables are chosen based on the sensitivity analysis of different objective functions relative to motor different geometrical parameters and some constraints are taken into account to... 

In this paper, a new fuzzy based Model Coordination (F-MC) strategy is proposed for hierarchical control of large-scale systems (LSS). To solve the overall problem with a two-level optimal control strategy, we first decompose the system into several sub-systems at the first level. Then, at the second level, a fuzzy coordinator will be used to predict the interaction between subsystems. The proposed fuzzy based coordination approach is applicable to all types of LSS. Although in this paper, an optimal control of a 2DOF robot manipulator, as a LSS, will be considered. The obtained results are compared with the centralized optimization  

This paper proposes an N-modular redundancy (NMR) technique with low energy-overhead for hard real-time multi-core systems. NMR is well-suited for multi-core platforms as they provide multiple processing units and low-overhead communication for voting. However, it can impose considerable energy overhead and hence its energy overhead must be controlled, which is the primary consideration of this paper. For this purpose the system operation can be divided into two phases: indispensable phase and on-demand phase. In the indispensable phase only half-plus-one copies for each task are executed. When no fault occurs during this phase, the results must be identical and hence the remaining copies... 

This paper presents a fuzzy-based interaction prediction approach (F-IPA) for two-level optimal control of large-scale systems. The design procedure uses a decomposition/coordination framework of hierarchical structures. At the first level, the system is decomposed into subsystems for which subproblems are formed. At the second level, a fuzzy coordinator is used to predict the coordination parameters needed to coordinate the solutions of the first level subproblems. The fuzzy coordinator uses a critic vector to evaluate its performance and learn its parameters by minimizing an energy function. The proposed control scheme is implemented on a two-degrees-of-freedom (2DOF) model of robot... 

Advances in semiconductor technology have made integration of multiple processing cores into one single die a promising trend towards increasing processing performance, lowering power consumption, and increasing reliability for embedded systems. Multicore processors, due to their intrinsic redundancies, are good choices for critical embedded systems for which the reliability is a crucial component. In this paper, an aging-aware adaptive fault tolerance method for DVFS-enabled multicore processors is presented. The analytical results show 3 to 6 order of magnitude increase in reliability of the system without addition of cores or redundant software. By using an aging-aware approach, the... 

This paper proposes a novel error-feedback lattice recursive least-squares (EF-LRLS) filter for online estimation of power system oscillatory modes. The EF-LRLS filter is applied to ambient data provided by phasor measurement units to identify the autoregressive (AR) model parameters. This filter has a modular structure; accordingly, if the length of the filter equals N, it identifies AR(1) to AR(N) models concurrently. In the proposed method, removing very low and high frequencies and re-sampling steps are fulfilled in an online fashion. This adaptive filter has less computational complexity than standard RLS filter, making it an appropriate choice for online system identification. The... 

Datapath designs that perform polynomial computations over Z 2n are used in many applications such as computer graphics and digital signal processing domains. As the market of such applications continues to grow, improvements in high-level synthesis and optimization techniques for multivariate polynomials have become really challenging. This paper presents an efficient algorithm for optimizing the implementation of a multivariate polynomial over Z2n in terms of the number of multipliers and adders. This approach makes use of promising heuristics to extract more complex common sub-expressions from the polynomial compared to the conventional methods. The proposed algorithm also utilizes a... 

Many real-time systems are in fact isochronal, where both early and late responses are harmful to the system or lead to lower quality of service. Real-time task scheduling problems proved that are NP-hard problems. Therefore, it is necessary to apply a heuristic search strategy on these problems. In this paper, a multi-objective genetic algorithm is proposed for static task scheduling in non-overloaded isochronal soft real-time systems. Its objective is to maximize the total utility of jobs. Simulation results indicate that genetic algorithm could be a suitable heuristic search strategy for task scheduling in isochronal soft real-time systems. © 2009 IEEE  

This paper presents the design of a fault-tolerant universal asynchronous receiver transmitter (UART) called micro-FT-UART for safety-critical SoC-based applications. This UART exploits advantages of three fault-tolerant techniques to tolerate soft errors. The three techniques are triple modular redundancy (TMR), Hamming code and a new technique called correction by parity storing (CPS). An VHDL model of a micro-UART is simulated by the ModelSim v.6.0 and synthesized by the Synopsys Design Compiler v.X-2005.09- SP2. About 1000 single-bit errors and 1000 multiple-bit errors are injected into different parts of the micro-UART to find out the error sensitivity of each specific part. Considering... 

We present a method for global estimation of joint velocities in rigid manipulators. A class of velocity observers with smooth dynamics are introduced whose structure depend on freely selectable functions and gains giving the flexibility of achieving multiple design objectives at the same time. Unlike most methods, no a priori knowledge of an upper bound for velocity magnitude is used. An adaptive version of the observer is also presented to handle a class of structured uncertainties in manipulator model. Simulation example illustrates low noise sensitivity of the globally convergent observer in comparison with semi-globally convergent observers. © 2009 IEEE  

Single event upsets (SEUs) and single event transients (SETs) are major reliability concerns in deep submicron technologies. As technology feature size shrinks, digital circuits are becoming more susceptible to SEUs and SETs. A novel SEU/SET-tolerant latch called feedback redundant SEU/SET-tolerant latch (FERST) is presented, where redundant feedback lines are used to mask SEUs and delay elements are used to filter SETs. Detailed SPICE simulations have been done to evaluate the proposed design and compare it with previous latch designs. The results show that the SEU tolerance of the FERST latch is almost equal to that of a TMR latch (a widely used latch which is the most reliable among the... 

In recent years, confrontation with hardware Trojans has become a major concern due to various reasons including outsourcing. Such a growing threat is more pronounced in reconfigurable devices as they are used in widespread applications due to low design cost and short time-to-market. Besides their vulnerability to hardware Trojan attacks, SRAM-based reconfigurable devices are also significantly susceptible to faults originated by particle strikes. There have been various methods to mitigate either hardware Trojan attacks or faults. To our knowledge, however, no method has been presented that can integrate detecting, distinguishing, and mitigating faults and Trojans. In this paper, we... 

Triple Modular Redundancy (TMR) is a historical and long-time-used approach for masking various kinds of faults. By employing redundancy and analyzing the results of three separate executions of the same program, TMR is able to attain excellent levels of reliability. While TMR provides a desirable level of reliability, it suffers from the high power consumption of the redundant hardware, a severe detriment to its broad adoption. The energy consumption of TMR can be mitigated if its operations are divided into two stages, and one stage is dropped in the absence of fault. Such an approach, which is evaluated in recent research, however, quickly fails in the presence of permanent faults, as we... 

Intense global competition, dynamic product variations, and rapid technological developments force manufacturing systems to adapt and respond quickly to various changes in the market. Such responsiveness could be achieved through new paradigms such as Reconfigurable manufacturing systems (RMS). In this paper, the problem of configuration design for a scalable reconfigurable RMS that produces different products of a part family is addressed. In order to handle demand fluctuations of products throughout their lifecycles with minimum cost, RMS configurations must change as well. Two different approaches are developed for addressing the system configuration design in different periods. Both...