An Intelligent System Approach to the Dynamic Hybrid Robot Control

The objective of this study was to solve the robot dynamic hybrid control problem using intelligent computational processes. In the course of problem- solving, biologically inspired models were used. This was because a robot can be seen as a physical intelligent system which interacts with the real world environment by means of its sensors and actuators. In the robot hybrid control method the neural networks, fuzzy logics and randomization strategies were used. To derive a complete intelligent state-of-the-art hybrid control system, several experiments were conducted in the study. Firstly an algorithm was formulated that can estimate the attracting basin boundary for a stable equilibrium point of a robot's kinematic nonlinear system. From this point the Artificial Neural Networks (ANN) based solution approach was verified for the inverse kinematics solution. Secondly, for the intelligent trajectory generation approach, the segmented tree neural networks for each link (inverse kinematics solution) and the randomness with fuzziness (coping the unstructured environment from the cost function) were used. A one-pass smoothing algorithm was used to generate a practical smooth trajectory path in near real time. Finally, for the hybrid control system the task was decomposed into several individual intelligent control agents, where the task space was split into the position-controlled subspaces, the force-controlled subspaces and the uncertain hyper plane identification subspaces. The problem was considered as a blind-tracking task by a human

Physics-Based Approaches For Structural Health Monitoring And Nondestructive Evaluation With Ultrasonic Guided Waves

The engineering infrastructures have a growing demand for damage monitoring systems to avoid any potential risk of failure. Proper damage monitoring solutions are of a great interest to this growing demand. The structural health monitoring (SHM) and nondestructive evaluation (NDE) offer appropriate online and offline damage monitoring solutions for a variety of mechanical and civil infrastructures that includes unmanned aerial vehicles (UAV), spaceships, commercial aircraft, ground transportation, wind turbines, nuclear spent fuel storage tanks, bridges, naval ships, and submarines. The fundamentals of the ultrasonic SHM and NDE consist of multi-disciplinary fields. The dissertation addresses SHM and NDE using ultrasonic guided waves, with an emphasis on the development of an analytical solution for non-axisymmetric guided wave propagation, multiphysics simulation, and experimental study of acoustic emission from the structural fatigue damage. An analytical solution for non-axisymmetric coupled guided wave propagation in plate-like structures was developed based on the equations of motion and elasticity relations. A general non-axisymmetric solution of guided wave propagation inplateis needed to analyze the guided wave-scatter from non-axisymmetric damage as encountered in practice. Under non-axisymmetric conditions, the problem is highly coupled and no potential based analytical solution has been reported in the literature so far. Helmholtz decomposition theorem was applied to the Navier-Lame equations that yielded a set of four coupled partial differential equations in four unknowns, the scalar potential Φ and the three components of the vector potential Hr, Hz, HΘ. A fourth equation, the ‘gauge condition’ was then added to the decomposition. A particular interpretation of the gauge condition is proposed. Our proposed approach decouples the governing equations and reduced the number of unknowns from four to three thus allowing one to express the solution in an elegant straight-forward way. The Rayleigh-Lamb characteristic equations were recovered and a general normal-modes expression for the solution was obtained. A hybrid global analytical and local finite element method was used to solve a practical aerospace rivet hole crack detection. The scatter cube of complex-valued wave damage interaction coefficients (WDICs) was developed to analyze any rivet hole of a multiple-rivet-hole lap joint system. It had been shown that not all parameters such as actuator-sensor locations, and frequencies were equally sensitive to the damage scatter. The optimum combination of parameters could better detect the crack in the rivet hole. The simulated time domain signals were produced for the optimum combination of parameters. Multiphysics simulations for fatigue crack generated acoustic emission (AE) were performed and the results were validated by the experiments. A novel application of inexpensive piezoelectric wafer active sensors (PWAS) has been explored. It has been shown that PWAS transducers successfully captured the fatigue-crack generated acoustic emissions in the thin plate-like aerospace materials. PWAS performance was compared with existing commercial AE sensors. It was found that PWAS captured richer frequency content than the existing AE sensors. Various AE waveform signatures were found from the fatigue crack advancement during the fatigue load evolution. Some AE waveform signatures were found to be related to the fatigue-crack extension while some of them were related to the fatigue-crack fretting, rubbing, and clapping. This observation was confirmed viii by synchronizing the fatigue loading with AE measurement by the same AE instrument. The in-situ microscopic measurement was performed during fatigue loading in MTS which provided the insights of the AE waveform evolution. It was hypothesized that the crack length estimation could be related the AE waveform signatures. FEM simulations and experiments were conducted using laser Doppler vibrometer (LDV) to verify our hypothesis. Two case studies are discussed showing the implementation of SHM and NDE approach in practical applications: (1) horizontal crack detection, size, and shape estimation in stiffened structures, (2) impact damage detection in manufactured aerospace composite structures. The dissertation finishes with conclusions, major contributions, and suggestions for future work

Using the Gauge Condition to Simplify The Elastodynamic Analysis of Guided Wave Propagation

In this article, gauge condition in elastodynamics is explored more to revive its potential capability of simplifying wave propagation problems in elastic medium. The inception of gauge condition in elastodynamics happens from the Navier-Lame equations upon application of Helmholtz theorem. In order to solve the elastic wave problems by potential function approach, the gauge condition provides the necessary conditions for the potential functions. The gauge condition may be considered as the superposition of the separate gauge conditions of Lamb waves and shear horizontal (SH) guided waves respectively, and thus, it may be resolved into corresponding gauges of Lamb waves and SH waves. The manipulation and proper choice of the gauge condition does not violate the classical solutions of elastic waves in plates; rather, it simplifies the problems. The gauge condition allows to obtain the analytical solution of complicated problems in a simplified manner

Guided Wave Inspection Of Cracks In The Rivet Hole Of An Aerospace Lap Joint Using Analytical-Fem Approach

Ultrasonic guided waves are very attractive for the inspection of large structures using nondestructive evaluation (NDE) and structural health monitoring (SHM) technique. Combined analytical and finite element analysis (CAFA) has been introduced for the detection of butterfly cracks in the rivet hole of the aerospace lap joint. Finite element analyses have been performed on the local damage area in spite of the whole large structure. Fundamental Lamb wave modes (S0 and A0) have been strike on the local damage from multiple directions to analyze the cracks of multiple-rivet-hole lap joint. The rivet hole cracks (damage) in the plate structure gives rise to the non-axisymmetric scattering of Lamb wave as well as shear horizontal (SH) wave although the incident Lamb wave source (primary source) is axisymmetric. Hence, the damage in the plate acts as a non-axisymmetric secondary source of Lamb wave and SH wave. The non-axisymmetric scattering of Lamb and SH waves are described using the wave damage interaction coefficient (WDIC). The WDIC of scattered Lamb and SH waves depends on the azimuth directions of the rivet hole as well as the frequencies of excitation. The WDIC involves scattering and mode conversion of Lamb waves occurred due to local damage. WDIC is captured around the damage for each direction of incidence over the frequency domain and “scatter cube” is formed for each incident Lamb mode. By analyzing the scattered cube of WDICs over the frequency domain and azimuth directions, the optimum parameters (frequency and location of sensor) can be determined for each angle of incidence. The scatter cubes are fed into the exact analytical framework to produce the time domain signal. This analysis enables us to obtain the optimum design parameters for better detection of the cracks in the rivet holes. The optimum parameters can be obtained for all possible cases of incident Lamb waves that would help to analyze the multiple-rivet-hole problem. Some examples of obtaining the optimum parameters are illustrated based on the most prominent time domain signal. The optimum parameters provide the guideline of the design of the sensor installation to obtain the most noticeable signals that represent the presence of cracks in the rivet hole. The thesis finishes with conclusions, and suggestions for future work

Non-cash payment method using QR codes in an automated microcontroller-based vending machine

This thesis report is submitted in partial fulfillment of the requirements for the degree of Bachelor of Science in Electrical and Electronic Engineering, 2014.Cataloged from PDF version of thesis report.Includes bibliographical references (page 42).The purpose of this thesis project is to implement a micro-controller-based automated vending machine which uses codes as a method for authorization of payments of online accounts to implement a non cash payment method for a contact less mobile payment system. Once a user places his/her order in the vending machine a QR (quick response) code is generated which holds all of the information of the user's order. An application is used to scan that QR code. The QR code once scanned with that application, populates the information of the order and sends that information to a web server only after the user’s approval for using their online account for payment. This web server takes this input from the user and processes the payment. The transaction is made from the web server with an online payment platform which holds the user's account. After the transaction is made, a second QR code, which stores the user's order information and authorization, is sent to the user's application from the server. User displays the QR code and it is scanned by the vending machine's scanner to release the desired product(s) thus making the process contact less.Md. Shahidur RahmanShamiha Yeasin BintuSidratul AmanB. Electrical and Electronic Engineerin

Guided Wave Based Crack Detection in the Rivet Hole Using Global Analytical with Local FEM Approach

In this article, ultrasonic guided wave propagation and interaction with the rivet hole cracks has been formulated using closed-form analytical solution while the local damage interaction, scattering, and mode conversion have been obtained from finite element analysis. The rivet hole cracks (damage) in the plate structure gives rise to the non-axisymmetric scattering of Lamb wave, as well as shear horizontal (SH) wave, although the incident Lamb wave source (primary source) is axisymmetric. The damage in the plate acts as a non-axisymmetric secondary source of Lamb wave and SH wave. The scattering of Lamb and SH waves are captured using wave damage interaction coefficient (WDIC). The scatter cubes of complex-valued WDIC are formed that can describe the 3D interaction (frequency, incident direction, and azimuth direction) of Lamb waves with the damage. The scatter cubes are fed into the exact analytical framework to produce the time domain signal. This analysis enables us to obtain the optimum design parameters for better detection of the cracks in a multiple-rivet-hole problem. The optimum parameters provide the guideline of the design of the sensor installation to obtain the most noticeable signals that represent the presence of cracks in the rivet hole