In this paper, design of an ultra high-resolution, compact and tunable optical displacement sensor for optomechatronical
systems is presented. In this proposal nanophotonic principles are used to develop displacement sensor which is required
strongly in micro and nano machines especially micro robotics. For this purpose, in this work nanocrystal doped micro
ring resonator is used as the basic cell. Then we propose integrated case for array applications such as array of micro
mirrors. We show that the proposed sensor can easily detect well below nanometer to near picometer ranges. Also, it is
illustrated that using Electromagnetically Induced Transparency (EIT) resolution of the proposed sensor can be
increased.
A new Terahertz photodetector based on Electromagnetically Induced Transparency (EIT) is proposed. In the terahertz
range (low energy signal) the limiting point is dark current. Dark current determines the signal-noise ratio of detectors.
Our main purpose in terahertz detection is reduction of the dark current which is done by converting the incoming
Terahertz IR signal to short-wavelength or visible probe optical field through EIT phenomena. For realization of this
idea, we used 4-level atoms which can be implemented by quantum wells or dots. In the proposed structure, the
terahertz-IR signal does not interact directly with ground state electrons, but affects the absorption characteristics of the
short-wavelength or visible probe optical field that directly interact with ground state electrons. Therefore, in the
proposed structure, the important thermionic dark current in terahertz detection, can be strongly reduced.
The road vehicle communication system constitutes an important component of an intelligent transportation system
(ITS). In this structure, control station is connected to base station via optical fiber for accomplishing high bandwidth
data exchange. Due to millimeter-wave feature, the system has small cells and also provides high mobility. In order to
have fast handover and dynamic bandwidth allocation, a medium access control scheme is used. Base stations are
deployed along the road to support the communication link to a vehicle. In this paper, we use a quasi-crystal lens to
focus the reflected waves to reduce the number of the base stations. The structure of the quasicrystal lens posses 12-fold
symmetry and hence 12-fold symmetric quasi-crystal. In this quasi structure, we have demonstrated that if we select a
proper slab thickness, we can achieve focusing in the outside of the slab as well as equal intensity of the source wave.
A new and efficient proposal for all-optical tunable mirror of VCSEL using electromagnetically induced transparency
(EIT) is proposed. For this purpose a slab doped with quantum dots for realization of 3-level atomic system is
considered. Density matrix formulation for time evaluation of the proposed structure is used. The reflection and
transmission coefficients of the considered slab are calculated and time development of the related amplitude and output
power and threshold current density of VCSEL laser studied. We show that some nanometer tuning can be obtained. So,
the proposed idea can open a new realization method of all-optical tunable VCSEL lasers.
Two-dimensional quasi-photonic crystal as microwave focusing element is studied. The proposed structure is a random
square-triangle tiling system with 12-fold symmetry and, hence, 12-fold symmetry quasi crystal. For this structure, finite
difference time domain for illustration of focusing of the electromagnetic wave is used and results show that with
suitable selection of crystal structure output signal is exactly the same as input one. The effective index of considered
structure is near to -1. This situation is useful for small spatial dispersion that is necessary for focusing.
Motion, independent of forces, is described by kinematic parameters (usually using Denavit-Hartenberg convention)
that have been used widely in biomechanical fields. Examples of these fields include robotics, human
motion studies, and biomechanical structures' design and control; e. g. for exoskeleton and artificial human
arm. A common way to precisely measure the joints movements is by using a motion capture system. Until
now, the most successful motion capture technology is optical motion capture; this is due to its highly accurate
measurement of small reflective markers that are attached to some relevant body landmarks.
This paper addresses the problem of estimating the human arm kinematics parameters from video or captured
images of human arms. We introduce a new robust framework that leads to reliable and accurate estimation of
shoulder and elbow center of rotations along with the arm kinematics parameters.
In this paper, the effect of carrier tunneling between wells on multiple-quantum well (MQW) laser characteristics is
investigated. Based on the rate equations developed for 3-levels (carrier transport between 3-D, 2-D and quasi 2-D
states) including carrier tunneling effect, a circuit model is proposed. According to simulation results with change of
tunneling time three interesting regions of operation are obtained. The operation of the proposed laser doesn't change for
tunneling time larger than a threshold value (0.1 nsec). For the tunneling time smaller than another threshold value (0.01
nsec) the operation of the laser strongly degraded. For the tunneling time between the two thresholds values the
operation of the laser can be optimized, which in this paper it is done for obtaining low turn-on delay time, leading to
suitable operation from simultaneous filling of the wells, high output intensity and large bandwidth points of view.
Catheter ablation is the preferred minimally invasive treatment for cardiac arrhythmias. Limited maneuverability of currently available catheters undermines the success of this treatment and subjects operations to prolonged repeated attempts to pace suspicious zones and ablate the arrhythmogenic substrates under ionizing radiation of fluoroscopy. To compensate for such inefficiencies, a control system that can replace operator's hand during the procedure is desired. This system should be able to direct catheter tip toward the ablation site and maintain its contact with the substrate during ablation, accelerating the process and enhancing its precision. To realize such a system, the first step is to kinematically model the catheter and to devise a control strategy to embed the kinematics of the catheter. This paper proposes a simplified approach to model and control a general single-segment active catheter as a continuum robot. In this approach, the flexible catheter is modeled as a rigid manipulator having coupled joints. Utilizing the structural coupling of the catheter, joint-variables are reduced to actuatable parameters thus lifting some of the mathematical difficulties in formulation of a control strategy for redundant manipulators. The modeling is validated through experiments with a typical steerable ablation catheter equipped with an electromagnetic tracker in vitro.
In this paper a novel method for investigation of inverse scattering in optical complex mediums is proposed. The
proposed method is based on Radial Basis Function Neural Networks (RBFNN) and Genetic Algorithms (GAs).
Medium discrimination is performed by RBFNN and corresponding medium parameters identification is done
using GAs. In the proposed method for simplicity the apodized, chirped and simultaneously apodized and
chirped types of mediums are considered as RBFNN library. The proposed method tries to open a new insight to
inverse scattering in optical devices and systems identification. The simulated results closely follow full
numerical simulations to illustrate the ability of the proposed algorithm.
In this paper an optical transfer function for description of the operation of complex fiber Bragg Gratings similar to
electrical ones is presented (H(jω)). For this purpose and reconstruction of the transfer function, the Genetic
Algorithm (GA) is used to find optimum number of poles and zeros from the measured reflection coefficient. After
building the transfer function according to the developed algorithm in this paper, the reflection coefficient for this
approximated system is obtained (simulated) and compared with measured values. The results obtained from the
approximated transfer function in these cases are so close to real measured data. So, the presented method introduces an
interesting approach for identification of the complex Bragg Gratings in frequency domain. Some of optical
characteristics (both frequency domain and time domain parameters) of these systems can be extracted from the
approximated transfer function easily.
An efficient method for high precision displacement measurement based on micro scale ring resonator and MOEMS is presented. The proposed structure can be used as discrete and integrated sensor in engineering applications. Photo-elastic effect is used to convert the physical displacement to the index of refraction variation in the ring resonator array. Analytical relation for description of system transfer function is derived. Single and multiple ring resonators are examined for increase of the system sensitivity. It is shown that an array of multiple ring resonators (array) is better than single ring case. Effects of optical and geometrical parameters of the proposed structure on sensitivity are studied.
The Interpolation method for identification of the Apodized and Chirped Fiber Bragg Gratings is used. For this purpose,
the Riccati equation for obtaining the reflection coefficient is used and numerically solved. Then for various system
parameters, the maximum reflection peaks, bandwidth of the reflection coefficient and the central frequency are
determined. Then using interpolation technique, three analytical equations can be extracted for the above-mentioned
quantities. Therefore using the obtained reflection coefficient there is a map from the reflection coefficient in frequency
domain to real space (index of refraction space). Hence, for the measured reflection coefficient, one can determine the
index of refraction profile including Apodized and Chirped functions. The proposed method is effective and can easily
determine the index of refraction profile.
In this paper a novel method is proposed for live endocardial boundary identification. The goal is to achieve an optimal solution to the problem of real-time automatic detection and tracking of endocardial border in ultrasonic image sequences acquired through Intracardiac Echocardiography (ICE). Border identification of 2D ultrasonic images, which normally consists of a number of stages namely preprocessing, segmentation, detection and visualization of the border, is a cumbersome task. ICE's potential in guidance of minimally invasive interventions requires online boundary detection of its inherently less speckled images. Numerous studies have addressed this issue in echographic images by proposing various methods applicable at each stage. With this repository of methods available, a comparative study is performed on single-image segmentation approaches. An algorithm based on order-statistics operators is proposed to achieve fast border delineation in a sequence of images. This method can outperform other approaches in terms of time and robustness, and does not require user interaction.
In this paper, a new open architecture for visual servo control tasks is illustrated. A Puma-560 robotic manipulator is used to prove the concept. This design enables doing hybrid force/visual servo control in an unstructured environment in different modes. Also, it can be controlled through Internet in teleoperation mode using a haptic device. Our proposed structure includes two major parts, hardware and software. In terms of hardware, it consists of a master (host) computer, a slave (target) computer, a Puma 560 manipulator, a CCD camera, a force sensor and a haptic device. There are five DAQ cards, interfacing Puma 560 and a slave computer. An open architecture package is developed using Matlab(R), Simulink(R) and XPC target toolbox. This package has the Hardware-In-the-Loop (HIL) property, i.e., enables one to readily implement different configurations of force, visual or hybrid control in real time. The implementation includes the following stages. First of all, retrofitting of puma was carried out. Then a modular joint controller for Puma 560 was realized using Simulink(R). Force sensor driver and force control implementation were written, using sfunction blocks of Simulink(R). Visual images were captured through Image Acquisition Toolbox of Matlab(R), and processed using Image Processing Toolbox. A haptic device interface was also written in Simulink(R). Thus, this setup could be readily reconfigured and accommodate any other robotic manipulator and/or other sensors without the trouble of the external issues relevant to the control, interface and software, while providing flexibility in components modification.
In this paper, the problem of combined vision/force servo control for robot manipulator is addressed. Three different robot vision control strategies: position-based, image-based, and hybrid control are combined with an impedance-based force controller and a comparison of these three combined vision/force control methods is investigated for the first time, in the context of generic robot kinematic-based sensory-task-space control structure. Furthermore, the issue of contact surface parameters estimation is also investigated. Simulation results have demonstrated that all the above vision/force control strategies are comparable in terms of both the dynamic response and accuracy of positioning and force control.
Design of objects that are used in vision-guided robotic systems crucially affects the overall system performance. In this paper, we target the problem of optimal feature point design for a given camera motion profile in robotic eye-in-hand systems. Having the intrinsic camera calibration parameters, the motion profile, and the image Jacobian matrix, a new directional relative motion resolvability measure is introduced. For each known point on the camera trajectory with known camera-to-object relative pose, the proposed measure is evaluated as a separate objective, resulting in a multi-objective
problem. A bounded multi-objective optimization approach is successfully utilized to solve the underconstrained feature design problem. Simulation results show that the motion of the camera is better resolved for the optimally designed object.
An optomechatronic system based on one-dimensional ultrasound detector array for intravascular pressure measurement is presented. The proposed structure is based on optical linear ring resonators array. The applied pressure on ring resonator will change the physical parameters such as effective cross section of the ring and finally the effective index of refraction. The transmitted intensity changes and the measured output power could be used for measuring the pressure. Also, for rejection of common errors after photodetectors blocks, differential amplifiers can be utilized. For incident light coupling to the rings, the integrated 3-dB couplers are used. The effect of pressure on single ring is simulated and the effects of coupling coefficient, coupler loss and ring resonator diameter are investigated. This structure easily can be extended to two-dimensional cases. So, the proposed structure can be used for intravascular imaging including low noise and high integration and precision.
In this paper, we focus on the robust feature selection and investigate the application of scale-invariant feature transform (SIFT) in robotic visual servoing (RVS). We consider a camera mounted onto the endpoint of an anthropomorphic manipulator (eye-in-hand configuration).
The objective of such RVS system is to control the pose of the camera so that a desired relative pose between the camera and the object of interest is maintained. It is seen that the SIFT feature point correspondences are not unique and hence those feature points with more than a unique match are disregarded. When the endpoint moves along a trajectory, the robust SIFT feature points are found and then for a similar trajectory the same selected feature points are used to keep track of the object in the current view. The point correspondences of the remaining robust feature points would provide the epipolar geometry of the two scenes, where knowing the camera calibration the motion of the camera is retrieved. The robot joint angle vector is then determined solving the inverse kinematics of the manipulator. We show how to select a set of robust features that are appropriate for the task of visual servoing. Robust SIFT feature points are scale and rotation invariant and effective when the current position of the endpoint is farther than and rotated with respect to the desired position.
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