34 research outputs found
A Foot Placement Strategy for Robust Bipedal Gait Control
This thesis introduces a new measure of balance for bipedal robotics called the foot placement estimator (FPE). To develop this measure, stability first is defined for a simple biped. A proof of the stability of a simple biped in a controls sense is shown to exist using classical methods for nonlinear systems. With the addition of a contact model, an analytical solution is provided to define the bounds of the region of stability. This provides the basis for the FPE which estimates where the biped must step in order to be stable. By using the FPE in combination with a state machine, complete
gait cycles are created without any precalculated trajectories. This includes gait initiation and termination. The bipedal model is then advanced to include more realistic mechanical and environmental models and the FPE approach is verified in a dynamic simulation. From these results, a 5-link, point-foot robot is designed and constructed to provide the final validation that the FPE can be used to provide closed-loop gait control. In addition, this approach is shown to demonstrate significant robustness to external disturbances. Finally, the FPE is shown in experimental results to be an unprecedented estimate of
where humans place their feet for walking and jumping, and for stepping in response to an external disturbance
Humanoid Robots
For many years, the human being has been trying, in all ways, to recreate the complex mechanisms that form the human body. Such task is extremely complicated and the results are not totally satisfactory. However, with increasing technological advances based on theoretical and experimental researches, man gets, in a way, to copy or to imitate some systems of the human body. These researches not only intended to create humanoid robots, great part of them constituting autonomous systems, but also, in some way, to offer a higher knowledge of the systems that form the human body, objectifying possible applications in the technology of rehabilitation of human beings, gathering in a whole studies related not only to Robotics, but also to Biomechanics, Biomimmetics, Cybernetics, among other areas. This book presents a series of researches inspired by this ideal, carried through by various researchers worldwide, looking for to analyze and to discuss diverse subjects related to humanoid robots. The presented contributions explore aspects about robotic hands, learning, language, vision and locomotion
Climbing and Walking Robots
Nowadays robotics is one of the most dynamic fields of scientific researches. The shift of robotics researches from manufacturing to services applications is clear. During the last decades interest in studying climbing and walking robots has been increased. This increasing interest has been in many areas that most important ones of them are: mechanics, electronics, medical engineering, cybernetics, controls, and computers. Today’s climbing and walking robots are a combination of manipulative, perceptive, communicative, and cognitive abilities and they are capable of performing many tasks in industrial and non- industrial environments. Surveillance, planetary exploration, emergence rescue operations, reconnaissance, petrochemical applications, construction, entertainment, personal services, intervention in severe environments, transportation, medical and etc are some applications from a very diverse application fields of climbing and walking robots. By great progress in this area of robotics it is anticipated that next generation climbing and walking robots will enhance lives and will change the way the human works, thinks and makes decisions. This book presents the state of the art achievments, recent developments, applications and future challenges of climbing and walking robots. These are presented in 24 chapters by authors throughtot the world The book serves as a reference especially for the researchers who are interested in mobile robots. It also is useful for industrial engineers and graduate students in advanced study
Fall Prediction and Controlled Fall for Humanoid Robots
Humanoids which resemble humans in their body structure and degrees of freedom are anticipated to work like them within infrastructures and environments constructed for
humans. In such scenarios, even humans who have exceptional manipulation, balancing, and locomotion skills are vulnerable to fall, humanoids being their approximate imitators
are no exception to this. Furthermore, their high center of gravity position in relation to their small support polygon makes them more prone to fall, unlike other robots such
as quadrupeds. The consequences of these falls are so devastating that it can instantly annihilate both the robot and its surroundings. This has become one of the major stumbling
blocks which humanoids have to overcome to operate in real environments. As a result, in this thesis, we have strived to address the imminent fall over of humanoids by developing
different control techniques. The fall over problem as such can be divided into three subissues: fall prediction, controlled fall, and its recovery. In the presented work, the first two
issues have been addressed, and they are presented in three parts.
First, we define what is fall over for humanoids, different sources for it to happen, the effect fall over has both on the robot and to its surroundings, and how to deal with them.
Following which, we give a brief introduction to the overall system which includes both the hardware and software components which have been used throughout the work for varied
purposes.
Second, the first sub-issue is addressed by proposing a generic method to predict the falling over of humanoid robots in a reliable, robust, and agile manner across various
terrains, and also amidst arbitrary disturbances. The aforementioned characteristics are strived to attain by proposing a prediction principle inspired by the human balance sensory
systems. Accordingly, the fusion of multiple sensors such as inertial measurement unit and gyroscope (IMU), foot pressure sensor (FPS), joint encoders, and stereo vision sensor,
which are equivalent to the human\u2019s vestibular, proprioception, and vision systems are considered. We first define a set of feature-based fall indicator variables (FIVs) from the
different sensors, and the thresholds for those FIVs are extracted analytically for four major disturbance scenarios. Further, an online threshold interpolation technique and an
impulse adaptive counter limit are proposed to manage more generic disturbances. For the generalized prediction process, both the instantaneous and cumulative sum of each FIVs
are normalized, and a suitable value is set as the critical limit to predict the fall over.
To determine the best combination and the usefulness of multiple sensors, the prediction performance is evaluated on four different types of terrains, in three unique combinations:
first, each feature individually with their respective FIVs; second, an intuitive performance based (PF); and finally, Kalman filter based (KF) techniques, which involve the usage
of multiple features. For PF and KF techniques, prediction performance evaluations are carried out with and without adding noise. Overall, it is reported that KF performs better
than PF and individual sensor features under different conditions. Also, the method\u2019s ability to predict fall overs during the robot\u2019s simple dynamic motion is also tested and
verified through simulations. Experimental verification of the proposed prediction method on flat and uneven terrains was carried out with the WALK-MAN humanoid robot.
Finally, in reference to the second sub-issue, i.e., the controlled fall, we propose two novel fall control techniques based on energy concepts, which can be applied online to mitigate
the impact forces incurred during the falling over of humanoids. Both the techniques are inspired by the break-fall motions, in particular, Ukemi motion practiced by martial arts
people. The first technique reduces the total energy using a nonlinear control tool, called energy shaping (ES) and further distributes the reduced energy over multiple contacts by
means of energy distribution polygons (EDP). We also include an effective orientation control to safeguard the end-effectors in the event of ground impacts. The performance of
the proposed method is numerically evaluated by dynamic simulations under the sudden falling over scenario of the humanoid robot for both lateral and sagittal falls. The effectiveness of the proposed ES and EDP concepts are verified by diverse comparative simulations regarding total energy, distribution, and impact forces.
Following the first technique, we proposed another controller to generate an online rolling over motion based on the hypothesis that multi-contact motions can reduce the impact
forces even further. To generate efficient rolling motion, critical parameters are defined by the insights drawn from a study on rolling, which are contact positions and attack
angles. In addition, energy-injection velocity is proposed as an auxiliary rolling parameter to ensure sequential multiple contacts in rolling. An online rolling controller is synthesized
to compute the optimal values of the rolling parameters. The first two parameters are to construct a polyhedron, by selecting suitable contacts around the humanoid\u2019s body. This
polyhedron distributes the energy gradually across multiple contacts, thus called energy distribution polyhedron. The last parameter is to inject some additional energy into the
system during the fall, to overcome energy drought and tip over successive contacts. The proposed controller, incorporated with energy injection, minimization, and distribution
techniques result in a rolling like motion and significantly reduces the impact forces, and it is verified in numerical experiments with a segmented planar robot and a full humanoid
model
Locomoção bípede adaptativa a partir de uma única demonstração usando primitivas de movimento
Doutoramento em Engenharia EletrotécnicaEste trabalho aborda o problema de capacidade de imitação da locomoção
humana através da utilização de trajetórias de baixo nível codificadas com
primitivas de movimento e utilizá-las para depois generalizar para novas
situações, partindo apenas de uma demonstração única. Assim, nesta linha de
pensamento, os principais objetivos deste trabalho são dois: o primeiro é
analisar, extrair e codificar demonstrações efetuadas por um humano, obtidas
por um sistema de captura de movimento de forma a modelar tarefas de
locomoção bípede. Contudo, esta transferência não está limitada à simples
reprodução desses movimentos, requerendo uma evolução das capacidades
para adaptação a novas situações, assim como lidar com perturbações
inesperadas. Assim, o segundo objetivo é o desenvolvimento e avaliação de
uma estrutura de controlo com capacidade de modelação das ações, de tal
forma que a demonstração única apreendida possa ser modificada para o robô
se adaptar a diversas situações, tendo em conta a sua dinâmica e o ambiente
onde está inserido.
A ideia por detrás desta abordagem é resolver o problema da generalização a
partir de uma demonstração única, combinando para isso duas estruturas
básicas. A primeira consiste num sistema gerador de padrões baseado em
primitivas de movimento utilizando sistemas dinâmicos (DS). Esta abordagem
de codificação de movimentos possui propriedades desejáveis que a torna ideal
para geração de trajetórias, tais como a possibilidade de modificar determinados
parâmetros em tempo real, tais como a amplitude ou a frequência do ciclo do
movimento e robustez a pequenas perturbações. A segunda estrutura, que está
embebida na anterior, é composta por um conjunto de osciladores acoplados
em fase que organizam as ações de unidades funcionais de forma coordenada.
Mudanças em determinadas condições, como o instante de contacto ou
impactos com o solo, levam a modelos com múltiplas fases. Assim, em vez de
forçar o movimento do robô a situações pré-determinadas de forma temporal, o
gerador de padrões de movimento proposto explora a transição entre diferentes
fases que surgem da interação do robô com o ambiente, despoletadas por
eventos sensoriais. A abordagem proposta é testada numa estrutura de
simulação dinâmica, sendo que várias experiências são efetuadas para avaliar
os métodos e o desempenho dos mesmos.This work addresses the problem of learning to imitate human locomotion actions
through low-level trajectories encoded with motion primitives and generalizing
them to new situations from a single demonstration. In this line of thought, the
main objectives of this work are twofold: The first is to analyze, extract and
encode human demonstrations taken from motion capture data in order to model
biped locomotion tasks. However, transferring motion skills from humans to
robots is not limited to the simple reproduction, but requires the evaluation of
their ability to adapt to new situations, as well as to deal with unexpected
disturbances. Therefore, the second objective is to develop and evaluate a
control framework for action shaping such that the single-demonstration can be
modulated to varying situations, taking into account the dynamics of the robot
and its environment.
The idea behind the approach is to address the problem of generalization from
a single-demonstration by combining two basic structures. The first structure is
a pattern generator system consisting of movement primitives learned and
modelled by dynamical systems (DS). This encoding approach possesses
desirable properties that make them well-suited for trajectory generation, namely
the possibility to change parameters online such as the amplitude and the
frequency of the limit cycle and the intrinsic robustness against small
perturbations. The second structure, which is embedded in the previous one,
consists of coupled phase oscillators that organize actions into functional
coordinated units. The changing contact conditions plus the associated impacts
with the ground lead to models with multiple phases. Instead of forcing the robot’s
motion into a predefined fixed timing, the proposed pattern generator explores
transition between phases that emerge from the interaction of the robot system
with the environment, triggered by sensor-driven events. The proposed approach
is tested in a dynamics simulation framework and several experiments are
conducted to validate the methods and to assess the performance of a humanoid
robot
Systèmes cognitifs artificiels : du concept au développement de comportements intelligents en robotique autonome
Les travaux présentés dans le cadre de cette habilitation à diriger des recherches s’appuient sur le principe de la robotique développementale et plus particulièrement sur le paradigme de l’énaction. L’idée n’est donc pas de développer un robot intelligent, mais plutôt de concevoir un robot qui soit capable de le devenir. L’originalité du travail présenté dans ce mémoire repose sur le fait que le système cognitif artificiel est décomposé en deux parties distinctes : la première regroupe des processus cognitifs « inconscients » et la deuxième concerne les processus cognitifs « conscients ». Les processus cognitifs inconscients correspondent aux aptitudes (pré-programmées ou apprises) fonctionnant de manière quasi-automatique, alors que les processus cognitifs conscients contribuent au développement et à l’apprentissage de nouvelles aptitudes. La cognition associée au robot est donc le résultat d’un processus de développement par lequel le robot devient progressivement plus habile et acquiert les connaissances lui permettant d’interpréter le monde qui l’entoure.Ce mémoire se décompose en trois grandes parties. La première partie correspond à un curriculum vitae détaillé présentant l’ensemble de mon parcours professionnel. La deuxième partie est consacrée à la présentation plus approfondie de mes activités de recherches qui se sont focalisées sur le développement de systèmes cognitifs artificiels appliqués à la robotique avec des applications dans les domaines de la locomotion bipède, la perception et l’acquisition autonome de connaissances ainsi que les systèmes multi-robots et l’intelligence distribuée. Enfin, la troisième partie est une compilation de quatre articles de revue représentatives de l’ensemble de mes travaux de recherches
A Bio-inspired architecture for adaptive quadruped locomotion over irregular terrain
Tese de doutoramento
Programa Doutoral em Engenharia Electrónica e de ComputadoresThis thesis presents a tentative advancement on walking control of small quadruped and humanoid
position controlled robots, addressing the problem of walk generation by combining dynamical systems
approach to motor control, insights from neuroethology research on vertebrate motor control and
computational neuroscience.
Legged locomotion is a complex dynamical process, despite the seemingly easy and natural behavior
of the constantly present proficiency of legged animals. Research on locomotion and motor control
in vertebrate animals from the last decades has brought to the attention of roboticists, the potential of
the nature’s solutions to robot applications. Recent knowledge on the organization of complex motor
generation and on mechanics and dynamics of locomotion has been successfully exploited to pursue
agile robot locomotion.
The work presented on this manuscript is part of an effort on the pursuit in devising a general,
model free solution, for the generation of robust and adaptable walking behaviors. It strives to devise a
practical solution applicable to real robots, such as the Sony’s quadruped AIBO and Robotis’ DARwIn-
OP humanoid. The discussed solutions are inspired on the functional description of the vertebrate
neural systems, especially on the concept of Central Pattern Generators (CPGs), their structure and
organization, components and sensorimotor interactions. They use a dynamical systems approach for
the implementation of the controller, especially on the use of nonlinear oscillators and exploitation of
their properties.
The main topics of this thesis are divided into three parts.
The first part concerns quadruped locomotion, extending a previous CPG solution using nonlinear
oscillators, and discussing an organization on three hierarchical levels of abstraction, sharing the purpose
and knowledge of other works. It proposes a CPG solution which generates the walking motion
for the whole-leg, which is then organized in a network for the production of quadrupedal gaits. The
devised solution is able to produce goal-oriented locomotion and navigation as directed through highlevel
commands from local planning methods. In this part, active balance on a standing quadruped is
also addressed, proposing a method based on dynamical systems approach, exploring the integration of
parallel postural mechanisms from several sensory modalities. The solutions are all successfully tested on the quadruped AIBO robot.
In the second part, is addressed bipedal walking for humanoid robots. A CPG solution for biped
walking based on the concept of motion primitives is proposed, loosely based on the idea of synergistic
organization of vertebrate motor control. A set of motion primitives is shown to produce the basis
of simple biped walking, and generalizable to goal-oriented walking. Using the proposed CPG, the
inclusion of feedback mechanisms is investigated, for modulation and adaptation of walking, through
phase transition control according to foot load information. The proposed solution is validated on the
humanoid DARwIn-OP, and its application is evaluated within a whole-body control framework.
The third part sidesteps a little from the other two topics. It discusses the CPG as having an alternative
role to direct motor generation in locomotion, serving instead as a processor of sensory information
for a feedback based motor generation. In this work a reflex based walking controller is devised for the
compliant quadruped Oncilla robot, to serve as purely feedback based walking generation. The capabilities
of the reflex network are shown in simulations, followed by a brief discussion on its limitations,
and how they could be improved by the inclusion of a CPG.Esta tese apresenta uma tentativa de avanço no controlo de locomoção para pequenos robôs quadrúpedes
e bipedes controlados por posição, endereçando o problema de geração motora através da combinação
da abordagem de sistemas dinâmicos para o controlo motor, e perspectivas de investigação
neuroetologia no controlo motor vertebrado e neurociência computacional.
Andar é um processo dinâmico e complexo, apesar de parecer um comportamento fácil e natural
devido à presença constante de animais proficientes em locomoção terrestre. Investigação na área da locomoção
e controlo motor em animais vertebrados nas últimas decadas, trouxe à atenção dos roboticistas
o potencial das soluções encontradas pela natureza aplicadas a aplicações robóticas. Conhecimento
recente relativo à geração de comportamentos motores complexos e da mecânica da locomoção tem
sido explorada com sucesso na procura de locomoção ágil na robótica.
O trabalho apresentado neste documento é parte de um esforço no desenho de uma solução geral,
e independente de modelos, para a geração robusta e adaptável de comportamentos locomotores. O
foco é desenhar uma solução prática, aplicável a robôs reais, tal como o quadrúpede Sony AIBO e
o humanóide DARwIn-OP. As soluções discutidas são inspiradas na descrição funcional do sistema
nervoso vertebrado, especialmente no conceito de Central Pattern Generators (CPGs), a sua estrutura e
organização, componentes e interacção sensorimotora. Estas soluções são implementadas usando uma
abordagem em sistemas dinâmicos, focandos o uso de osciladores não lineares e a explorando as suas
propriedades.
Os tópicos principais desta tese estão divididos em três partes.
A primeira parte explora o tema de locomoção quadrúpede, expandindo soluções prévias de CPGs
usando osciladores não lineares, e discutindo uma organização em três níveis de abstracção, partilhando
as ideias de outros trabalhos. Propõe uma solução de CPG que gera os movimentos locomotores
para uma perna, que é depois organizado numa rede, para a produção de marcha quadrúpede. A
solução concebida é capaz de produzir locomoção e navegação, comandada através de comandos de alto
nível, produzidos por métodos de planeamento local. Nesta parte também endereçado o problema da
manutenção do equilíbrio num robô quadrúpede parado, propondo um método baseado na abordagem
em sistemas dinâmicos, explorando a integração de mecanismos posturais em paralelo, provenientes de várias modalidades sensoriais. As soluções são todas testadas com sucesso no robô quadrupede AIBO.
Na segunda parte é endereçado o problema de locomoção bípede. É proposto um CPG baseado
no conceito de motion primitives, baseadas na ideia de uma organização sinergética do controlo motor
vertebrado. Um conjunto de motion primitives é usado para produzir a base de uma locomoção bípede
simples e generalizável para navegação. Esta proposta de CPG é usada para de seguida se investigar
a inclusão de mecanismos de feedback para modulação e adaptação da marcha, através do controlo de
transições entre fases, de acordo com a informação de carga dos pés. A solução proposta é validada
no robô humanóide DARwIn-OP, e a sua aplicação no contexto do framework de whole-body control é
também avaliada.
A terceira parte desvia um pouco dos outros dois tópicos. Discute o CPG como tendo um papel
alternativo ao controlo motor directo, servindo em vez como um processador de informação sensorial
para um mecanismo de locomoção puramente em feedback. Neste trabalho é desenhado um controlador
baseado em reflexos para a geração da marcha de um quadrúpede compliant. As suas capacidades são
demonstradas em simulação, seguidas por uma breve discussão nas suas limitações, e como estas podem
ser ultrapassadas pela inclusão de um CPG.The presented work was possible thanks to the support by the Portuguese Science and Technology Foundation through the PhD grant SFRH/BD/62047/2009
Climbing and Walking Robots
With the advancement of technology, new exciting approaches enable us to render mobile robotic systems more versatile, robust and cost-efficient. Some researchers combine climbing and walking techniques with a modular approach, a reconfigurable approach, or a swarm approach to realize novel prototypes as flexible mobile robotic platforms featuring all necessary locomotion capabilities. The purpose of this book is to provide an overview of the latest wide-range achievements in climbing and walking robotic technology to researchers, scientists, and engineers throughout the world. Different aspects including control simulation, locomotion realization, methodology, and system integration are presented from the scientific and from the technical point of view. This book consists of two main parts, one dealing with walking robots, the second with climbing robots. The content is also grouped by theoretical research and applicative realization. Every chapter offers a considerable amount of interesting and useful information
Bio-Inspired Robotics
Modern robotic technologies have enabled robots to operate in a variety of unstructured and dynamically-changing environments, in addition to traditional structured environments. Robots have, thus, become an important element in our everyday lives. One key approach to develop such intelligent and autonomous robots is to draw inspiration from biological systems. Biological structure, mechanisms, and underlying principles have the potential to provide new ideas to support the improvement of conventional robotic designs and control. Such biological principles usually originate from animal or even plant models, for robots, which can sense, think, walk, swim, crawl, jump or even fly. Thus, it is believed that these bio-inspired methods are becoming increasingly important in the face of complex applications. Bio-inspired robotics is leading to the study of innovative structures and computing with sensory–motor coordination and learning to achieve intelligence, flexibility, stability, and adaptation for emergent robotic applications, such as manipulation, learning, and control. This Special Issue invites original papers of innovative ideas and concepts, new discoveries and improvements, and novel applications and business models relevant to the selected topics of ``Bio-Inspired Robotics''. Bio-Inspired Robotics is a broad topic and an ongoing expanding field. This Special Issue collates 30 papers that address some of the important challenges and opportunities in this broad and expanding field