Sharif Digital Repository

Detection and isolation of faults in the exhaust gas path of a turbocharged spark ignition (SI) engine is an essential part of the engine control unit (ECU) strategies to minimize exhaust emission and ensure safe operation of a turbocharger. This paper proposes a novel physics-based strategy to detect and isolate an exhaust manifold leakage and a closed-stuck wastegate fault. The strategy is based on a globally optimal parameter estimation algorithm which detects an effective hole area in the exhaust manifold. The estimation algorithm requires prediction of the exhaust manifold's input and output flows. The input flow is predicted by a nonlinear Luenberger observer which is analytically... 

Experimental system identification of a flexible beam based on sweep square excitation is studied. For the purpose of nonparametric identification, an excitation signal is conducted to evaluate the frequency response of the system. The experiment is designed to excite the beam using a piezo actuator, in a way to raise the chance of exciting first three natural modes. In order to find the best linear representation of the real system, two different identification methods are applied. First, autoregressive moving average eXogenous method is employed to identify the transfer function of the beam. Then, the identification is carried out using the subspace identification method to obtain the... 

In this study, active vibration control of a cantilevered flexible beam structure equipped with bonded piezoelectric sensor/actuators is investigated. The linear quadratic regulator technique together with an observer is adopted to design the controller as well as to provide the full-state feedback. Two different approaches are subsequently used for simultaneously integrated optimization of the controller and observer parameters. In the first approach, a linear experimental model of the system is obtained using identification techniques, and the optimization is then performed based on a computer simulation of the system. However, in the second approach, a hardware-in-the-loop optimization... 

Approximate solutions for vibrations of flexible beam-type appendages subjected to tip mass are studied while uniform and exponential profiles for arm deployment are simulated. Applying an equivalent dynamical system and following Lagrangian approach, the equations of motion of the system are derived as nonlinear ordinary differential equations (ODEs) (with time-varying coefficients), in which the effect of the tip mass can be considered as some nonlinearity added to the 'no tip mass' case dynamics. The approximate closed-form solutions are obtained through a novel methodology using a computer algorithm, in which the solutions of the 'no tip mass' case are expanded by imposing quadratic... 

Using elastic couplings in servo motor drives may lead to torsional oscillations which are usually extinguished by reducing the bandwidth of the control system as a countermeasure. A high performance servo drive however needs fast dynamic characteristics. The conventional controllers, such as PI controllers, may not be able to improve the dynamic response while keeping the system stable. Fractional order modeling offers a good framework for flexible structures such as two mass servo drives. In this paper, the dynamic response and stability of two-mass servo drive is improved using a fractional order controller. The fractional order controller allows increasing the phase margin of the system... 

Position control of Shape Memory Alloy (SMA) actuators has been a challenging topic during the last years due to their nonlinearities in the governing physical equations as well as their hysteresis behaviors. Using the inverse of phenomenological hysteresis model in order to compensate the input-output hysteresis behavior of these actuators shows the effectiveness of this approach. In this paper, in order to control the tip deflection of a large deformation flexible beam actuated by an SMA actuator wire, a feedforward-feedback controller is proposed. The feedforward part of the proposed control system, maps the beam deflection into SMA temperature, is based on the inverse of the generalized... 

Detection and isolation of faults in the exhaust gas path of a turbocharged spark ignition (SI) engine is an essential part of the engine control unit (ECU) strategies to minimize exhaust emission and ensure safe operation of a turbocharger. This paper proposes a novel physics-based strategy to detect and isolate an exhaust manifold leakage and a closed-stuck wastegate fault. The strategy is based on a globally optimal parameter estimation algorithm which detects an effective hole area in the exhaust manifold. The estimation algorithm requires prediction of the exhaust manifold's input and output flows. The input flow is predicted by a nonlinear Luenberger observer which is analytically... 

There has been great demand for shape memory alloy (SMA) wires as actuators for shape control of flexible structures. The experimental setup of this study consists of a flexible beam actuated by two active SMA actuators. The input applied to the SMA actuator in this setup is electrical current while the output is the strain or position. To control strain of the actuator, the SMA wire is heated resistively in order to reach the desired temperature calculated by inverse of the phenomenological model. In heating the SMA wire resistively, the controllable quantity is the heat input to the wire via an applied current. In controller design, changes of physical properties of SMA wires and the... 

Vibration analysis of a new type of compliant parallel mechanism with flexible intermediate links is investigated. The application of the Timoshenko beam theory to the mathematical modeling of the intermediate flexible link is described, and the equations of motion of the flexible links are obtained by using Lagrange's equation of motion. The equations of motion are obtained in the form of a set of ordinary differential equations by using assumed mode method theory. The governing differential equations of motion are solved using perturbation method. The assumed mode shapes and frequencies are to be obtained based on clamped-clamped boundary conditions. Comparing perturbation method with... 

Hysteresis and significant nonlinearities in the behavior of Shape Memory Alloy (SMA) actuators encumber effective utilization of these actuator. Due to these effects, the position control of SMA actuators has been a great challenge in recent years. Literature review of the research conducted in this area shows that using the inverse of the phenomenological hysteresis models can compensate the hysteresis of these actuators effectively. But, inverting some of these models, such as Preisach model, is numerically a complex task. However, the generalized Prandtl-Ishlinskii model is analytically invertible, and therefore can be implemented conveniently as a feedforward controller for compensating... 

There are two different ways of using SMA wires as actuators for shape control of flexible structures; which can be either embedded within the composite laminate or externally attached to the structure. Since the actuator can be placed at different offset distances from the beam, external actuators produce more bending moment and, consequently, considerable shape changes with the same magnitude of the actuation force comparing to the embedded type. Such a configuration also provides fast convection which is very important in shape control applications that require a high-frequency response of SMA actuators. Although combination and modeling of externally-attached SMA actuator wires and... 

There are two different ways of using shape memory alloy (SMA) wire as an actuator for shape control of flexible structures: it can be either embedded within the composite laminate or externally attached to the structure. As the actuator can be placed at different offset distances from the beam, external actuators produce more bending moment and, consequently, considerabnle shape changes with the same magnitude of actuation force compared with the embedded type. Such a configuration also provides faster heat transfer rate owing to convection, which is very important in shape control applications that require a highfrequency response of SMA actuators. Although combination and physics-based... 

There are two ways of using SMAs as actuators for shape control of flexible structures; they can be either embedded within composite laminates or externally attached to the structures. Since the actuator can be placed at different offset distances from the beam, external actuators produce more bending moment and, consequently, more shape change. Such a configuration also allows introduction of fast convection cooling, very important in shape control applications that require a high-frequency response of SMA actuators. Although combination and modeling of externally-attached SMA actuator wires and strips have been widely considered by some researchers, these studies have some weaknesses that... 

Flapping wings are promising lift and thrust generators, especially for very low Reynolds numbers. To investigate aeroelastic effects of flexible wings (specifically, wing's twisting stiffness) on hovering and cruising aerodynamic performance, a flapping-wing system and an experimental setup were designed and built. This system measures the unsteady aerodynamic and inertial forces, power usage, and angular speed of the flapping wing motion for different flapping frequencies and for various wings with different chordwise flexibility. Aerodynamic performance of the vehicle for both no wind (hovering) and cruise condition was investigated. Results show how elastic deformations caused by... 

In this paper, the vibration suppression of micro- or nano-scale cantilever beams used in M/NEMS devices is studied. The beam is subjected to some nonlinear distributed forces, namely electrostatics force with first order fringing field correction, Casimir, and van der Waals forces. For the sake of precision, the beam is modeled by strain gradient elasticity theory capable of predicting the size effects in mechanical behavior of small-scale flexible structures. Since the governing partial differential equation of motion is nonlinear, the linearization approach is adopted to tackle the control problem. A novel control law is proposed that guarantees the exponential stability of the linearized... 

Using seven bond-order potentials and five force fields, the fundamental natural frequency of C60,Ag(1) (breathing mode), and two other basic modes, namely Hg(1) (squashing mode) and T2g(1) are calculated. The same frequencies are derived through a DFT B3LYP/6-31G(d) calculation. Furthermore, the results are compared with Raman and IR scattering data, and previous quantum mechanics calculations, depicting the strength of each interatomic potential in predicting the vibrational properties of Buckminsterfullerene. AIREBO, which is formulated for analyzing hydrocarbons, shows the highest accuracy among all of the potentials under investigation. In general, bond-order potentials predict a... 

The steer by wire system for vehicles has attracted much attention in recent years. Steer by wire systems provide many benefits in terms of functionality and at the same time present significant challenges too. It is essential to investigate the stability of steer by wire systems using a more sophisticated model rather than common approximated models. Fractional order modeling offers a good modeling framework for complex dynamical systems involving flexible structures such as multi-mass drives. In this paper a nonlinear fractional order model for steer by wire systems is presented  

Vibration control is an essential problem in different structure. Smart material can make a structure smart, adaptive and self-controlling so they are effective in active vibration control. Piezoelectric elements can be used as sensors and actuators in flexible structures for sensing and actuating purposes. In this paper we use PZT elements as sensors and actuator to control the vibration of a cantilever beam. Also we study the effect of different types of controller on vibration. © 2009 IEEE