786 research outputs found
Vision Science and Technology at NASA: Results of a Workshop
A broad review is given of vision science and technology within NASA. The subject is defined and its applications in both NASA and the nation at large are noted. A survey of current NASA efforts is given, noting strengths and weaknesses of the NASA program
Study of the urban evolution of Brasilia with the use of LANDSAT data
The urban growth of Brasilia within the last ten years is analyzed with special emphasis on the utilization of remote sensing orbital data and automatic image processing. The urban spatial structure and the monitoring of its temporal changes were focused in a whole and dynamic way by the utilization of MSS-LANDSAT images for June 1973, 1978 and 1983. In order to aid data interpretation, a registration algorithm implemented at the Interactive Multispectral Image Analysis System (IMAGE-100) was utilized aiming at the overlap of multitemporal images. The utilization of suitable digital filters, combined with the images overlap, allowed a rapid identification of areas of possible urban growth and oriented the field work. The results obtained permitted an evaluation of the urban growth of Brasilia, taking as reference the proposed stated for the construction of the city
Push recovery with stepping strategy based on time-projection control
In this paper, we present a simple control framework for on-line push
recovery with dynamic stepping properties. Due to relatively heavy legs in our
robot, we need to take swing dynamics into account and thus use a linear model
called 3LP which is composed of three pendulums to simulate swing and torso
dynamics. Based on 3LP equations, we formulate discrete LQR controllers and use
a particular time-projection method to adjust the next footstep location
on-line during the motion continuously. This adjustment, which is found based
on both pelvis and swing foot tracking errors, naturally takes the swing
dynamics into account. Suggested adjustments are added to the Cartesian 3LP
gaits and converted to joint-space trajectories through inverse kinematics.
Fixed and adaptive foot lift strategies also ensure enough ground clearance in
perturbed walking conditions. The proposed structure is robust, yet uses very
simple state estimation and basic position tracking. We rely on the physical
series elastic actuators to absorb impacts while introducing simple laws to
compensate their tracking bias. Extensive experiments demonstrate the
functionality of different control blocks and prove the effectiveness of
time-projection in extreme push recovery scenarios. We also show self-produced
and emergent walking gaits when the robot is subject to continuous dragging
forces. These gaits feature dynamic walking robustness due to relatively soft
springs in the ankles and avoiding any Zero Moment Point (ZMP) control in our
proposed architecture.Comment: 20 pages journal pape
Human Motion Trajectory Prediction: A Survey
With growing numbers of intelligent autonomous systems in human environments,
the ability of such systems to perceive, understand and anticipate human
behavior becomes increasingly important. Specifically, predicting future
positions of dynamic agents and planning considering such predictions are key
tasks for self-driving vehicles, service robots and advanced surveillance
systems. This paper provides a survey of human motion trajectory prediction. We
review, analyze and structure a large selection of work from different
communities and propose a taxonomy that categorizes existing methods based on
the motion modeling approach and level of contextual information used. We
provide an overview of the existing datasets and performance metrics. We
discuss limitations of the state of the art and outline directions for further
research.Comment: Submitted to the International Journal of Robotics Research (IJRR),
37 page
Autonomous Execution of Cinematographic Shots with Multiple Drones
This paper presents a system for the execution of autonomous cinematography
missions with a team of drones. The system allows media directors to design
missions involving different types of shots with one or multiple cameras,
running sequentially or concurrently. We introduce the complete architecture,
which includes components for mission design, planning and execution. Then, we
focus on the components related to autonomous mission execution. First, we
propose a novel parametric description for shots, considering different types
of camera motion and tracked targets; and we use it to implement a set of
canonical shots. Second, for multi-drone shot execution, we propose distributed
schedulers that activate different shot controllers on board the drones.
Moreover, an event-based mechanism is used to synchronize shot execution among
the drones and to account for inaccuracies during shot planning. Finally, we
showcase the system with field experiments filming sport activities, including
a real regatta event. We report on system integration and lessons learnt during
our experimental campaigns
Aerospace medicine and biology: A continuing bibliography with indexes (supplement 324)
This bibliography lists 200 reports, articles and other documents introduced into the NASA Scientific and Technical Information System during May, 1989. Subject coverage includes: aerospace medicine and psychology, life support systems and controlled environments, safety equipment, exobiology and extraterrestrial life, and flight crew behavior and performance
Modelling and control of lightweight underwater vehicle-manipulator systems
This thesis studies the mathematical description and the low-level control structures for
underwater robotic systems performing motion and interaction tasks. The main focus is
on the study of lightweight underwater-vehicle manipulator systems. A description of
the dynamic and hydrodynamic modelling of the underwater vehicle-manipulator system
(UVMS) is presented and a study of the coupling effects between the vehicle and manipulator
is given. Through simulation results it is shown that the vehicle’s capabilities are
degraded by the motion of the manipulator, when it has a considerable mass with respect to
the vehicle. Understanding the interaction effects between the two subsystems is beneficial
in developing new control architectures that can improve the performance of the system.
A control strategy is proposed for reducing the coupling effects between the two subsystems
when motion tasks are required. The method is developed based on the mathematical
model of the UVMS and the estimated interaction effects. Simulation results show the validity
of the proposed control structure even in the presence of uncertainties in the dynamic
model. The problem of autonomous interaction with the underwater environment is further
addressed. The thesis proposes a parallel position/force control structure for lightweight underwater
vehicle-manipulator systems. Two different strategies for integrating this control
law on the vehicle-manipulator structure are proposed. The first strategy uses the parallel
control law for the manipulator while a different control law, the Proportional Integral
Limited control structure, is used for the vehicle. The second strategy treats the underwater
vehicle-manipulator system as a single system and the parallel position/force law is
used for the overall system. The low level parallel position/force control law is validated
through practical experiments using the HDT-MK3-M electric manipulator. The Proportional
Integral Limited control structure is tested using a 5 degrees-of-freedom underwater
vehicle in a wave-tank facility. Furthermore, an adaptive tuning method based on interaction
theory is proposed for adjusting the gains of the controller. The experimental results
show that the method is advantageous as it decreases the complexity of the manual tuning
otherwise required and reduces the energy consumption. The main objectives of this
thesis are to understand and accurately represent the behaviour of an underwater vehiclemanipulator
system, to evaluate this system when in contact with the environment and to
design informed low-level control structures based on the observations made through the
mathematical study of the system. The concepts presented in this thesis are not restricted
to only vehicle-manipulator systems but can be applied to different other multibody robotic
systems
NASA Automated Rendezvous and Capture Review. Executive summary
In support of the Cargo Transfer Vehicle (CTV) Definition Studies in FY-92, the Advanced Program Development division of the Office of Space Flight at NASA Headquarters conducted an evaluation and review of the United States capabilities and state-of-the-art in Automated Rendezvous and Capture (AR&C). This review was held in Williamsburg, Virginia on 19-21 Nov. 1991 and included over 120 attendees from U.S. government organizations, industries, and universities. One hundred abstracts were submitted to the organizing committee for consideration. Forty-two were selected for presentation. The review was structured to include five technical sessions. Forty-two papers addressed topics in the five categories below: (1) hardware systems and components; (2) software systems; (3) integrated systems; (4) operations; and (5) supporting infrastructure
Optimal Multi-UAV Trajectory Planning for Filming Applications
Teams of multiple Unmanned Aerial Vehicles (UAVs) can be used to record large-scale
outdoor scenarios and complementary views of several action points as a promising
system for cinematic video recording. Generating the trajectories of the UAVs plays
a key role, as it should be ensured that they comply with requirements for system
dynamics, smoothness, and safety. The rise of numerical methods for nonlinear
optimization is finding a
ourishing field in optimization-based approaches to multi-
UAV trajectory planning. In particular, these methods are rather promising for
video recording applications, as they enable multiple constraints and objectives to
be formulated, such as trajectory smoothness, compliance with UAV and camera
dynamics, avoidance of obstacles and inter-UAV con
icts, and mutual UAV visibility.
The main objective of this thesis is to plan online trajectories for multi-UAV teams in
video applications, formulating novel optimization problems and solving them in real
time.
The thesis begins by presenting a framework for carrying out autonomous cinematography
missions with a team of UAVs. This framework enables media directors
to design missions involving different types of shots with one or multiple cameras,
running sequentially or concurrently. Second, the thesis proposes a novel non-linear
formulation for the challenging problem of computing optimal multi-UAV trajectories
for cinematography, integrating UAV dynamics and collision avoidance constraints,
together with cinematographic aspects such as smoothness, gimbal mechanical limits,
and mutual camera visibility. Lastly, the thesis describes a method for autonomous
aerial recording with distributed lighting by a team of UAVs. The multi-UAV trajectory
optimization problem is decoupled into two steps in order to tackle non-linear cinematographic aspects and obstacle avoidance at separate stages. This allows the
trajectory planner to perform in real time and to react online to changes in dynamic
environments.
It is important to note that all the methods in the thesis have been validated
by means of extensive simulations and field experiments. Moreover, all the software
components have been developed as open source.Los equipos de vehículos aéreos no tripulados (UAV) son sistemas prometedores para grabar
eventos cinematográficos, en escenarios exteriores de grandes dimensiones difíciles de cubrir
o para tomar vistas complementarias de diferentes puntos de acción. La generación de
trayectorias para este tipo de vehículos desempeña un papel fundamental, ya que debe
garantizarse que se cumplan requisitos dinámicos, de suavidad y de seguridad.
Los enfoques basados en la optimización para la planificación de trayectorias de múltiples
UAVs se pueden ver beneficiados por el auge de los métodos numéricos para la resolución de
problemas de optimización no lineales. En particular, estos métodos son bastante
prometedores para las aplicaciones de grabación de vídeo, ya que permiten formular múltiples
restricciones y objetivos, como la suavidad de la trayectoria, el cumplimiento de la dinámica
del UAV y de la cámara, la evitación de obstáculos y de conflictos entre UAVs, y la visibilidad
mutua.
El objetivo principal de esta tesis es planificar trayectorias para equipos multi-UAV en
aplicaciones de vídeo, formulando novedosos problemas de optimización y resolviéndolos en
tiempo real.
La tesis comienza presentando un marco de trabajo para la realización de misiones
cinematográficas autónomas con un equipo de UAVs. Este marco permite a los directores de
medios de comunicación diseñar misiones que incluyan diferentes tipos de tomas con una o
varias cámaras, ejecutadas de forma secuencial o concurrente. En segundo lugar, la tesis
propone una novedosa formulación no lineal para el difícil problema de calcular las
trayectorias óptimas de los vehículos aéreos no tripulados en cinematografía, integrando en el
problema la dinámica de los UAVs y las restricciones para evitar colisiones, junto con aspectos
cinematográficos como la suavidad, los límites mecánicos del cardán y la visibilidad mutua de
las cámaras. Por último, la tesis describe un método de grabación aérea autónoma con
iluminación distribuida por un equipo de UAVs. El problema de optimización de trayectorias se
desacopla en dos pasos para abordar los aspectos cinematográficos no lineales y la evitación
de obstáculos en etapas separadas. Esto permite al planificador de trayectorias actuar en
tiempo real y reaccionar en línea a los cambios en los entornos dinámicos.
Es importante señalar que todos los métodos de la tesis han sido validados mediante extensas
simulaciones y experimentos de campo. Además, todos los componentes del software se han
desarrollado como código abierto
Sailbot 2017-2018
The goal of this MQP was to build and program a robot capable of competing in the 2018 International Robotic Sailing Competition (IRSC), also known as Sailbot. This project utilized existing research on control and design of autonomous sailboats, and built on lessons learned from the last two years of WPI’s Sailbot entries. The final product of this MQP was a more reliable, easier to control, and more innovative design than last year’s event-winning boat
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