Attitude control laws that use control moment gyros (CMGs) and momentum wheels are derived with nonlinear techniques. The control laws command the CMGs to provide rapid angular acceleration and the momentum wheels to reject tracking and initial condition errors. Numerical simulations of derived control laws are compared. A trend analysis is performed to examine the benefits of the derived controllers. We describe the design of a CMG built using commercial off-the-shelf (COTS) equipment. A mixed attitude control strategy is implemented on the spacecraft simulator at Virginia Tech. / Master of Science

There are benefits to the use of internal actuators for rotational maneuvers of small-scale underwater vehicles. Internal actuators are protected from the outside environment by the external pressure hull and will not disturb the surrounding environment during inspection tasks. Additionally, internal actuators do not rely on the relative fluid motion to exert control moments, therefore they are useful at low speed and in hover. This paper describes the design, fabrication and testing of one such autonomously controlled, internally actuated underwater vehicle. The Internally Actuated, Modular Bodied, Untethered Submersible (IAMBUS) can be used to validate non-linear control strategies using internal actuators. Vehicle attitude control is provided by three orthogonally mounted reaction wheels. The housing is a spherical glass pressure vessel, which contains all of the components, such as actuators, ballast system, power supply, on-board computer and inertial sensor. Since the housing is spherically symmetric, the hydrodynamics of IAMBUS are uncoupled (e.g. a roll maneuver does not impact pitch or yaw). This hull shape enables IAMBUS to be used as a spacecraft attitude dynamics and control simulator with full rotational freedom. / Master of Science

During normal walking, the relative motion of the human knee involves flexion/extension, anterior/posterior sliding, and medial/lateral rotation. As well, the knee experiences a complex, dynamic loading curve with a peak of up to seven times body weight. However, most wear testing machines that have been used to evaluate total knee replacement materials are unidirectional and/or apply only static force. This thesis presents an alternate wear testing device capable of simulating the most prevalent motions of the knee, and applying physiologically-correct loading to the material interface. By incorporating a CoCr disc, an UHMWPE block, stepping motors, pneumatic components, computer control, and linear tables in an x-y configuration, the device is capable of quickly screening new and alternative materials to UHMWPE before evaluating them on a much more expensive knee simulator. In addition, flexibility of the device allows programming of many different motion and loading configurations permitting materials testing under only certain circumstances, or evaluating the effects on wear of specific motions. Design rationale, development, validation, and future recommendations are presented. / Master of Science

Simulators are important tools for wireless sensor network (sensornet) design and evaluation. However, existing simulators only support evaluations of protocols and software aspects of sensornet design. Thus they cannot accurately capture the significant impacts of various hardware designs on sensornet performance. To fill in the gap, we proposed SUNSHINE, a scalable hardware-software cross-domain simulator for sensornet applications. SUNSHINE is the first sensornet simulator that effectively supports joint evaluation and design of sensor hardware and software performance in a networked context. SUNSHINE captures the performance of network protocols, software and hardware through the integration of two modules: a network simulator TOSSIM [1] and hardware-software simulator P-Sim composed of an instruction-set simulator SimulAVR [2] and a hardware simulator GEZEL [3]. This thesis focuses on the integration of TOSSIM and P-Sim. It discusses the integration design considerations and explains how to address several integration challenges: time conversion, data conversion, and time synchronization. Some experiments are also given to demonstrate SUNSHINE's cross-domain simulation capability, showing SUNSHINE's strength by integrating simulators from different domains. / Master of Science

A new approach is presented that relies upon 3D electromagnetic simulation results to characterize the complex permittivity of homogeneous dielectric materials. By modeling the test fixture and obtaining a set of simulated S-parameters through an iterative solution process, the dielectric constant and loss tangent can be found. With further development, the 3D simulation results may be used to replace the need for complex theoretical analysis of the measurement geometry. The method is applied to an X-band rectangular waveguide setup, for which the theoretical S-parameters can be readily calculated. A Teflon sample, for which the dielectric properties are well-known, is used for all measurements and calculations. After presenting a detailed derivation to obtain the theoretical S-parameters, the Teflon sample is measured and compared to the theoretical results, from which the comparison shows great promise. An inverse solution algorithm is used to solve for the material properties from the experimental S-parameters. Low-frequency measurement of the Teflon sheet was performed by using a dielectric capacitor test fixture. The results show the effect of an air gap between the electrode and sample, producing serious errors. / Master of Science

Yes / Intercultural competence is an essential 21st Century skill. A key issue for developers of cross-cultural training simulators is the need to provide relevant learning experience adapted to the learner’s abilities. This paper presents a dialogic approach for a quick assessment of the depth of a learner's current intercultural awareness as part of the EU ImREAL project. To support the dialogue, Linked Data is seen as a rich knowledge base for a diverse range of resources on cultural aspects. This paper investigates how semantic technologies could be used to: (a) extract a pool of concrete culturally-relevant facts from DBpedia that can be linked to various cultural groups and to the learner, (b) model a learner's knowledge on a selected set of cultural themes and (c) provide a novel, adaptive and user-friendly, user modelling dialogue for cultural awareness. The usability and usefulness of the approach is evaluated by CrowdFlower and Expert Inspection.

Active magnetic bearings have several potential applications in spacecraft design. Based on the gyrostat model, we develop equations that describe the internal torques and forces that occur between the body and one of the attached wheels. We evaluate the transverse torques for the torque--free gyrostat and a gyrostat undergoing attitude maneuvers using momentum wheels and external torques. We then apply these internal forces to a model of an active magnetic bearing system and discuss their effects on the force limit, the actuator slew rate and the equivalent stiffness and damping parameters. As a basis for this study we use the Distributed Spacecraft Attitude Control System Simulator (DSACSS) with a Revolve MBRotor active magnetic bearing system. The results of several numerical simulations show that the magnitude and frequency of the internal torques remain small over the estimated range of motion of the DSACSS--MBRotor gyrostat. As such, the transverse torques caused by the rotational motion remain less than the discussed performance limits. We show that the magnitude of the internal torques can also be minimized by reducing the axial moment of inertia of the wheel. Furthermore, we discuss the equivalent Jeffcott model. By applying a standard Proportional--Integral--Derivative controller to the active magnetic bearing both the equivalent stiffness and damping parameters remain constant. / Master of Science

Due to economic and operational constraints, there is an increasing demand from aviation operators and training manufacturers to extract maximum training usage from the lower fidelity suite of flight simulators. It is possible to augment low-fidelity flight simulators to achieve equivalent performance compared to high-fidelity setups but at reduced cost and greater mobility. In particular for visual manoeuvres, the virtual reality technique of head-tracking amplification for virtual view control enables full field-of-regard access even with limited field-of-view displays. This research quantified the effects of this technique on piloting performance, workload and simulator sickness by applying it to a fixed-base, low-fidelity, low-cost flight simulator. In two separate simulator trials, participants had to land a simulated aircraft from a visual traffic circuit pattern whilst scanning for airborne traffic. Initially, a single augmented display was compared to the common triple display setup in front of the pilot. Starting from the base leg, pilots exhibited tighter turns closer to the desired ground track and were more actively conducting visual scans using the augmented display. This was followed up by a second experiment to quantify the scalability of augmentation towards larger displays and field of views. Task complexity was increased by starting the traffic pattern from the downwind leg. Triple displays in front of the pilot yielded the best compromise delivering flight performance and traffic detection scores just below the triple projectors but without an increase in track deviations and the pilots were also less prone to simulator sickness symptoms. This research demonstrated that head augmentation yields clear benefits of quick user adaptation, low-cost, ease of systems integration, together with the capability to negate the impact of display sizes yet without incurring significant penalties in workload and incurring simulator sickness. The impact of this research is that it facilitates future flight training solutions using this augmentation technique to meet budgetary and mobility requirements. This enables deployment of simulators in large numbers to deliver expanded mission rehearsal previously unattainable within this class of low-fidelity simulators, and with no restrictions for transfer to other training media.

This thesis investigated the development of an EEG-based brain controlled switch and the design of a software for nerve conduction study. For EEG-based brain controlled switch, we proposed a novel paradigm for an online brain-controlled switch based on Event-Related Synchronizations (ERDs) following external sync signals. Furthermore, the ERD feature was enhanced by 3 event-related moving averages and the performance was tested online. Subjects were instructed to perform an intended motor task following an external sync signal in order to turn on a virtual switch. Meanwhile, the beta-band (16-20Hz) relative ERD power (ERD in reverse value order) of a single EEG Laplacian channel from primary motor area was calculated and filtered by 3 event-related moving average in real-time. The computer continuously monitored the filtered relative ERD power level until it exceeded a pre-set threshold selected based on the observations of ERD power range to turn on the virtual switch. Four right handed healthy volunteers participated in this study. The false positive rates encountered among the four subjects during the operation of the virtual switch were 0.8±0.4%, whereby the response time delay was 36.9±13.0s and the subjects required approximately 12.3±4.4 s of active urging time to perform repeated attempts in order to turn on the switch in the online experiments. The aim of nerve conduction simulator software design is to create software that can be used by nerve conduction simulator to serve as a medical simulator or education tool to train novice physicians for nerve conduction study test. The real response waveform of 10 different upper limb nerves in conduction studies were obtained from the equipment used in real patient studies. A waveform generation model was built to generalize the response waveform near the standard stimulus site within study interest region based on the extracted waveforms and normal reference parameters of each study and stimulus site coordinates. Finally, based on the model, a software interface was created to simulate 10 different nerve conduction studies of the upper limb with 9 pathological conditions.

A visão de muitas pessoas sobre uma colônia de formigas, em geral, é de que estes pequenos e inofensivos insetos somente se movem aleatoriamente para coletar alimento e conservá-los em seus ninhos. Um olhar destreinado não conseguiria notar o nível de complexidade e organização que é requerido por uma colônia de formigas para sua sobrevivência. Uma formiga simples é parte de um grande grupo que coopera entre si para criar um superorganismo. Sem uma autoridade central ou indivíduos com habilidade de um pensamento cognitivo complexo, a colônia se auto-organiza, e, de fato, ajusta seus recursos de uma maneira muito eficiente. Essa dissertação investiga o papel da comunicação indireta nas tarefas de exploração e forrageamento, e como isso afeta as decisões de um agente simples e traz um comportamento emergente útil à toda colônia. Por fim, este trabalho implementa uma plataforma de simulação multi-agente inspirado em formigas / Most people\'s view of an ant colony and ants in general is that they simply pose harmless little insects that move randomly and gather food in their underground nests. The untrained eye would have never guessed the level of complexity and organisation that is required in order for an ant colony to survive. The simple ant is a part of a huge group, which cooperate one superorganism. Without any central authority or the ability of complex cognitive thought from the individuals, the colony seems to self organise and in fact adjust its resources in a quite efficient way. This dissertation investigates the role of indirect communication in the exploration and forage task and how it affects the decisions of the single agent and brings an emergent behaviour that is useful to all the colony. Finally this work implements an ant inspired multi-agent simulation plataform