Sharif Digital Repository

Recent research has revealed that the security of deep neural networks that directly process 3D point clouds to classify objects can be threatened by adversarial samples. Al-though existing adversarial attack methods achieve high success rates, they do not restrict the point modifications enough to preserve the point cloud appearance. To overcome this shortcoming, two constraints are proposed. These include applying hard boundary constraints on the number of modified points and on the point perturbation norms. Due to the restrictive nature of the problem, the search space contains many local maxima. The proposed method addresses this issue by using a high step-size at the beginning of the... 

The current study investigates the effect of polyacrylonitrile (PAN) addition on morphology and antifouling properties of poly(vinyl chloride) (PVC) asymmetric flat ultrafiltration (UF) membranes. The membranes are prepared via phase inversion method induced by immersion precipitation at different PVC/PAN blending ratio up to 40 wt% PAN. Also, membranes with blending ratio of PVC/ PAN:70/30, which showed the highest water flux and flux recovery ratio, were used for membrane preparation with 4 wt% of Polyethylene glycol (PEG) addition in four different molecular weight, 600 Da, 1,000 Da, 6,000 Da and 20,000 Da, which was used as pore former and hydrophilic polymeric additive. The performance... 

This paper presents a new method for identification of distributed unbalanced mass (DUM) of flexible rotors. To this end, a circular section rotor with constant area, distributed parameters, and a spatial distributed unbalanced mass is considered. Rotary inertia and gyroscopic effects are included in the dynamic of system. Then, by measuring the deflection of shaft at some points while rotating in a specific angular speed, an identification method is proposed to obtain the amount of DUM. This information can be used in balancing procedure of the rotor. The method is justified by two numerical simulations. Copyright © 2006 by ASME  

In this paper, a combination of fuzzy clustering estimation and sliding mode control is used to control a chaotic system, which its mathematical model is unknown. It is assumed that the chaotic system has an affine form. At first, the nonlinear noninput part of the chaotic system is estimated by a fuzzy model, without using any input noise signal. Without loss of generality, it is assumed that chaotic behavior is appeared in the absence of input signal. In this case, the recurrent property of chaotic behavior is used for estimating its model. After constructing the fuzzy model, which estimates the noninput part of the chaotic system, control and on-line identification of the input-related... 

In present paper, a feedback linearization control is applied to control a chaotic pendulum system. Tracking the desired periodic orbits such as period-one, period-two, and period-four orbits is efficiently achieved. Due to the presence of saturation in real world control signals, the stability of controller is investigated in presence of saturation and sufficient stability conditions are obtained. At first feedback linearization control law is designed, then to avoid the singularity condition, a saturating constraint is applied to the control signal. The stability conditions are obtained analytically. These conditions must be investigated for each specific case numerically. Simulation... 

This study investigates the chaotic response of the spring-pendulum system. In this system besides of strange attractors, multiple regular attractors may co-exist for some values of system parameters, and it is important to study the global behavior of the system using the basin boundaries of the attractors. Here multiple scales method is used to distinguish the regions of stable and unstable attractors. Early studies show that there are unstable regions for the spring-pendulum system. In this study using bifurcation diagrams and Poincaré maps, it is shown that in some cases the response becomes quasi-periodic or chaotic for some deviations from external and internal resonance frequencies.... 

In this article, dynamic equations of a single wheel robot, known as Gyrover, through Lagrange method applying a new approach will be addressed. There is no simplification on the dynamic analysis. Considering any possible differentiable function for the road's curve, the effect of the road's roughness is completely described in the dynamic equation evaluation. Although there are complicated relations between the wheel and rough terrain, due to the efficient generalized coordinate selection, closed form dynamic equation of the motion is derived. Because of the closed form formulation, required time for simulation will be reduced. From the proposed complete model a simplified model for the... 

Genetic Algorithm is applied to the physical parameter estimation of a full vehicle nonlinear multi-body ride model. Beforehand unity of system representation (identifiability) and sensitivity analysis for determining the effects of parameter changes on the response of the vehicle is discussed. A random road profile is designed as a persistent excitation. Input-output data required for the identification is obtained from ADAMS/CAR simulations of a more complex model. Robustness of the identification method is studied by adding different noise levels to the ADAMS output signals. Validation of the results is carried out by comparison of the identified model outputs with experimental... 

In some tasks, a rigid robot manipulator handles a long, slender, and flexible tool, which usually has not been equipped with vibration measuring devices. This situation makes a difficult tool tip position control problem. In this paper, a new method will be presented for simultaneous tip position and vibration suppression control of a flexible tool on a rigid-link 3-DOF robot. This approach uses fuzzy logic rule-based controllers without using any sensor and actuator on the tool and with no a priori knowledge about the tool. Numerical simulation of robot and tool set has been accomplished and results support the fact that designed fuzzy controllers perform remarkably well in reducing... 

This paper proposes a new electromagnetic force model and its parameter identification method. As a case study, the parameters of the proposed model for an experimental electromagnetic bearing system are obtained using extended Kalman filter (EKF). The experimental setup includes a symmetric rigid rotor which is disturbed by the electromagnet of a magnetic bearing. Experimental results show that the system response to harmonic excitation includes super-harmonic terms which are not shown by the well-known conventional electromagnetic force model. This shortcoming necessitates an investigation to propose a more realistic electromagnetic force model. Based on the observations of the system... 

In some tasks, a rigid robot manipulator handles a long, slender, and flexible tool, which usually has not been equipped with vibration measuring devices. This situation makes a different tool tip position control problem. In this paper, a new method will be presented for simultaneous tip position and vibration suppression control of a flexible tool on a rigid-link 3-DOF robot. This approach uses fuzzy logic rule-based controllers without using any sensors and actuators on the tool or a priori knowledge about the tool. Numerical simulation of robot and tool set has been accomplished and results support the fact that designed fuzzy controllers perform remarkably well in reducing vibrations... 

Three-axis rotary table is a flight motion simulator (FMS) used in the hardware in the loop (HWIL) simulation. Geometrical Modeling of 3-axis rotary tables is described and then three possible Geometrical layouts are driven. Kinematic and dynamic modelings of a 3-axis rotary table are developed in this paper. Denavit-Hartenberg (D-H) method, Recursive Newton-Euler (RNE) and Lagrange methods are used, respectively, in kinematic and dynamic modeling. A kinematic Error analysis is applied to determine the orientation and position accuracy of the table. Dynamic sensitivity analysis is also performed and the first-order sensitivity functions are derived corresponding several dynamic and control... 

This paper illustrates the control of chaos using a fuzzy estimating system based on batch training and recursive least square methods for a continuous time dynamic system. The fuzzy estimator system is trained on both Ott-Geobogi-Yorke (OGY) control algorithm and Pyragas's delayed feedback control algorithm. The system, considered as a case study, is a Bonhoeffer-van der Pol (BVP) oscillator. It is found that the implemented fuzzy control system constructed on OGY algorithm results in smaller control transient response than that of the OGY control algorithm itself. The transient response of Pyragas fuzzy control does not show a significant improvement in compare to the Pyragas control... 

Shape Memory Alloys (SMA's) are inherently non-linear devices exhibiting significant hysteresis in their stress-strain-temperature characteristic. We have used the variable sub-layer SMA model of Ikuta [3] to extract the advanced dynamic model of our proposed varying stress SMA actuator. A nonlinear finite element analysis was used to model the proposed bending spring in the actuator and the extended variable sub-layer model of Ikuta was considered to extract stress-displacement relations. Finally, these two models are combined with thermo dynamic model of SMA and a schematic flowchart is proposed to calculate SMA resultant strain under an arbitrary current input. At the end, we applied this... 

This paper illustrates the control of chaos using a fuzzy estimating system based on batch training and recursive least square methods for a continuous time dynamic system. The fuzzy estimator system is trained on both Ott-Geobogi-Yorke (OGY) control algorithm and Pyragas's delayed feedback control algorithm. The system, considered for this study, is a Bonhoeffer-van der Pol (BVP) oscillator. It is found that the implemented fuzzy control system constructed on OGY algorithm results in smaller control transient response than that of the OGY control algorithm itself. The transient response of Pyragas fuzzy control does not show a significant improvement in compare to the Pyragas control...