1,810 research outputs found
Fully automated urban traffic system
The replacement of the driver with an automatic system which could perform the functions of guiding and routing a vehicle with a human's capability of responding to changing traffic demands was discussed. The problem was divided into four technological areas; guidance, routing, computing, and communications. It was determined that the latter three areas being developed independent of any need for fully automated urban traffic. A guidance system that would meet system requirements was not being developed but was technically feasible
A review of millimeter-wave radar research
With the rapid development of scientifi c research and the maturity of technology, millimeter-wave radar has become the
focus of research in industrial production, national defense construction and other fi elds because of its high precision and high applicability.
This paper introduces the application fields and algorithm development of millimeter wave radar, expounds the common application
scenarios of millimeter wave radar, and gradually elaborates the development and update of radar detection algorithm, on this basis, the
new research direction of millimeter wave radar and the improved algorithm idea of FMCW millimeter wave radar detection algorithm are
proposed
Spectral feature classification of oceanographic processes using an autonomous underwater vehicle
Submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy at the Massachusetts Institute of Technology and the Woods Hole Oceanographic Institution June 2000The thesis develops and demonstrates methods of classifying ocean processes using
an underwater moving platform such as an Autonomous Underwater Vehicle (AUV).
The "mingled spectrum principle" is established which concisely relates observations
from a moving platform to the frequency-wavenumber spectrum of the ocean process.
It clearly reveals the role of the AUV speed in mingling temporal and spatial
information. For classifying different processes, an AUV is not only able to jointly
utilize the time-space information, but also at a tunable proportion by adjusting
its cruise speed. In this respect, AUVs are advantageous compared with traditional
oceanographic platforms.
Based on the mingled spectrum principle, a parametric tool for designing an AUVbased
spectral classifier is developed. An AUV's controllable speed tunes the separability
between the mingled spectra of different processes. This property is the key to
optimizing the classifier's performance.
As a case study, AUV-based classification is applied to distinguish ocean convection
from internal waves. The mingled spectrum templates are derived from the MIT
Ocean Convection Model and the Garrett-Munk internal wave spectrum model. To
allow for mismatch between modeled templates and real measurements, the AUVbased
classifier is designed to be robust to parameter uncertainties. By simulation
tests on the classifier, it is demonstrated that at a higher AUV speed, convection's
distinct spatial feature is highlighted to the advantage of classification.
Experimental data are used to test the AUV-based classifier. An AUV-borne flow
measurement system is designed and built, using an Acoustic Doppler Velocimeter
(ADV). The system is calibrated in a high-precision tow tank. In February 1998, the
AUV acquired field data of flow velocity in the Labrador Sea Convection Experiment.
The Earth-referenced vertical flow velocity is extracted from the raw measurements.
The classification test result detects convection's occurrence, a finding supported by
more traditional oceanographic analyses and observations. The thesis work provides
an important foundation for future work in autonomous detection and sampling of
oceanographic processes.This thesis research
has been funded by the Office of Naval Research (ONR) under Grants NOOOl4-95-1-1316,
NOO0l4-97-1-0470, and by the MIT Sea Grant College Program under Grant NA46RG0434
The low-level guidance of an experimental autonomous vehicle
This thesis describes the data processing and the control that constitutes a method of guidance for an autonomous guided vehicle (AGV) operating in a predefined and structured environment such as a warehouse or factory. A simple battery driven vehicle has been constructed which houses an MC68000 based microcomputer and a number of electronic interface cards. In order to provide a user interface, and in order to integrate the various aspects of the proposed guidance method, a modular software package has been developed. This, along with the research vehicle, has been used to support an experimental approach to the research. The vehicle's guidance method requires a series of concatenated curved and straight imaginary Unes to be passed to the vehicle as a representation of a planned path within its environment. Global position specifications for each line and the associated AGV direction and demand speed for each fine constitute commands which are queued and executed in sequence. In order to execute commands, the AGV is equipped with low level sensors (ultrasonic transducers and optical shaft encoders) which allow it to estimate and correct its global position continually. In addition to a queue of commands, the AGV also has a pre-programmed knowledge of the position of a number of correction boards within its environment. These are simply wooden boards approximately 25cm high and between 2 and 5 metres long with small protrusions ("notches") 4cm deep and 10cm long at regular (Im) intervals along its length. When the AGV passes such a correction board, it can measure its perpendicular distance and orientation relative to that board using two sets of its ultrasonic sensors, one set at the rear of the vehicle near to the drive wheels and one set at the front of the vehicle. Data collected as the vehicle moves parallel to a correction board is digitally filtered and subsequently a least squares line fitting procedure is adopted. As well as improving the reliability and accuracy of orientation and distance measurements relative to the board, this provides the basis for an algorithm with which to detect and measure the position of the protrusions on the correction board. Since measurements in three planar, local coordinates can be made (these are: x, the distance travelled parallel to a correction board; and y,the perpendicular distance relative to a correction board; and Ɵ, the clockwise planar orientation relative to the correction board), global position estimation can be corrected. When position corrections are made, it can be seen that they appear as step disturbances to the control system. This control system has been designed to allow the vehicle to move back onto its imaginary line after a position correction in a critically damped fashion and, in the steady state, to track both linear and curved command segments with minimum error
Crew interface definition study, phase 1
The timeline analysis of the Shuttle orbiter missions which was conducted in the Phase I Crew Interface Definition Study and the requirements for the man-in-the-loop simulation study are presented. Mission definitions and objectives are presented as they relate to various Shuttle Orbiter missions. The requirements for crew participation and the information required by the crew are discussed, and finally the rationale behind the display concept and calling procedures is given. The simulation objectives, the simulation mechanization, including a detailed presentation of the display and control concept, the simulator test plan and the results are discussed
Analysis and design of a capsule landing system and surface vehicle control system for Mars exploration
Problems related to the design and control of a mobile planetary vehicle to implement a systematic plan for the exploration of Mars are reported. Problem areas include: vehicle configuration, control, dynamics, systems and propulsion; systems analysis, terrain modeling and path selection; and chemical analysis of specimens. These tasks are summarized: vehicle model design, mathematical model of vehicle dynamics, experimental vehicle dynamics, obstacle negotiation, electrochemical controls, remote control, collapsibility and deployment, construction of a wheel tester, wheel analysis, payload design, system design optimization, effect of design assumptions, accessory optimal design, on-board computer subsystem, laser range measurement, discrete obstacle detection, obstacle detection systems, terrain modeling, path selection system simulation and evaluation, gas chromatograph/mass spectrometer system concepts, and chromatograph model evaluation and improvement
Trajectory planning based on adaptive model predictive control: Study of the performance of an autonomous vehicle in critical highway scenarios
Increasing automation in automotive industry is an important contribution to
overcome many of the major societal challenges. However, testing and validating a highly
autonomous vehicle is one of the biggest obstacles to the deployment of such vehicles,
since they rely on data-driven and real-time sensors, actuators, complex algorithms,
machine learning systems, and powerful processors to execute software, and they must
be proven to be reliable and safe.
For this reason, the verification, validation and testing (VVT) of autonomous
vehicles is gaining interest and attention among the scientific community and there has
been a number of significant efforts in this field. VVT helps developers and testers to
determine any hidden faults, increasing systems confidence in safety, security, functional
analysis, and in the ability to integrate autonomous prototypes into existing road
networks. Other stakeholders like higher-management, public authorities and the public
are also crucial to complete the VTT process.
As autonomous vehicles require hundreds of millions of kilometers of testing
driven on public roads before vehicle certification, simulations are playing a key role as
they allow the simulation tools to virtually test millions of real-life scenarios, increasing
safety and reducing costs, time and the need for physical road tests.
In this study, a literature review is conducted to classify approaches for the VVT
and an existing simulation tool is used to implement an autonomous driving system. The
system will be characterized from the point of view of its performance in some critical
highway scenarios.O aumento da automação na indústria automotiva é uma importante
contribuição para superar muitos dos principais desafios da sociedade. No entanto,
testar e validar um veículo altamente autónomo é um dos maiores obstáculos para a
implantação de tais veículos, uma vez que eles contam com sensores, atuadores,
algoritmos complexos, sistemas de aprendizagem de máquina e processadores potentes
para executar softwares em tempo real, e devem ser comprovadamente confiáveis e
seguros.
Por esta razão, a verificação, validação e teste (VVT) de veículos autónomos está
a ganhar interesse e atenção entre a comunidade científica e tem havido uma série de
esforços significativos neste campo. A VVT ajuda os desenvolvedores e testadores a
determinar quaisquer falhas ocultas, aumentando a confiança dos sistemas na
segurança, proteção, análise funcional e na capacidade de integrar protótipos autónomos
em redes rodoviárias existentes. Outras partes interessadas, como a alta administração,
autoridades públicas e o público também são cruciais para concluir o processo de VTT.
Como os veículos autónomos exigem centenas de milhões de quilómetros de
testes conduzidos em vias públicas antes da certificação do veículo, as simulações estão
a desempenhar cada vez mais um papel fundamental, pois permitem que as ferramentas
de simulação testem virtualmente milhões de cenários da vida real, aumentando a
segurança e reduzindo custos, tempo e necessidade de testes físicos em estrada.
Neste estudo, é realizada uma revisão da literatura para classificar abordagens
para a VVT e uma ferramenta de simulação existente é usada para implementar um
sistema de direção autónoma. O sistema é caracterizado do ponto de vista do seu
desempenho em alguns cenários críticos de autoestrad
Analysis and design of a capsule landing system and surface vehicle control system for Mars exploration
Problems related to an unmanned exploration of the planet Mars by means of an autonomous roving planetary vehicle are investigated. These problems include: design, construction and evaluation of the vehicle itself and its control and operating systems. More specifically, vehicle configuration, dynamics, control, propulsion, hazard detection systems, terrain sensing and modelling, obstacle detection concepts, path selection, decision-making systems, and chemical analyses of samples are studied. Emphasis is placed on development of a vehicle capable of gathering specimens and data for an Augmented Viking Mission or to provide the basis for a Sample Return Mission
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