547 research outputs found
3LP: a linear 3D-walking model including torso and swing dynamics
In this paper, we present a new model of biped locomotion which is composed
of three linear pendulums (one per leg and one for the whole upper body) to
describe stance, swing and torso dynamics. In addition to double support, this
model has different actuation possibilities in the swing hip and stance ankle
which could be widely used to produce different walking gaits. Without the need
for numerical time-integration, closed-form solutions help finding periodic
gaits which could be simply scaled in certain dimensions to modulate the motion
online. Thanks to linearity properties, the proposed model can provide a
computationally fast platform for model predictive controllers to predict the
future and consider meaningful inequality constraints to ensure feasibility of
the motion. Such property is coming from describing dynamics with joint torques
directly and therefore, reflecting hardware limitations more precisely, even in
the very abstract high level template space. The proposed model produces
human-like torque and ground reaction force profiles and thus, compared to
point-mass models, it is more promising for precise control of humanoid robots.
Despite being linear and lacking many other features of human walking like CoM
excursion, knee flexion and ground clearance, we show that the proposed model
can predict one of the main optimality trends in human walking, i.e. nonlinear
speed-frequency relationship. In this paper, we mainly focus on describing the
model and its capabilities, comparing it with human data and calculating
optimal human gait variables. Setting up control problems and advanced
biomechanical analysis still remain for future works.Comment: Journal paper under revie
Fast walking with rhythmic sway of torso in a 2D passive ankle walker
There is a category of biped robots that are equipped with passive or un-actuated ankles, which we call Passive-Ankle Walkers (PAWs). Lack of actuation at ankles is a disadvantage in the fast walking of PAWs. We started this study with an intuitive hypothesis that rhythmic sway of torso may enable faster walking in PAWs. To test this hypothesis, firstly, we optimized the rhythmic sway of torso of a simulated PAW model for fast walking speed, and analyzed the robustness of the optimal trajectories. Then we implemented the optimal trajectories on a real robot. Both the simulation analysis and the experimental results indicated that optimized torso-swaying can greatly increase the walking speed by 40%. By analyzing the walking patterns of the simulated model and the real robot, we identified the reason for the faster walking with swaying-torso: The rhythmic sway of torso enables the robot to walk with a relatively large step-length while still keeninu a hizh sten-frenuencv
Humanoid Robot Soccer Locomotion and Kick Dynamics: Open Loop Walking, Kicking and Morphing into Special Motions on the Nao Robot
Striker speed and accuracy in the RoboCup (SPL) international robot soccer league is becoming
increasingly important as the level of play rises. Competition around the ball is now decided in a
matter of seconds. Therefore, eliminating any wasted actions or motions is crucial when attempting to
kick the ball.
It is common to see a discontinuity between walking and kicking where a robot will return to an
initial pose in preparation for the kick action. In this thesis we explore the removal of this behaviour
by developing a transition gait that morphs the walk directly into the kick back swing pose. The
solution presented here is targeted towards the use of the Aldebaran walk for the Nao robot.
The solution we develop involves the design of a central pattern generator to allow for controlled
steps with realtime accuracy, and a phase locked loop method to synchronise with the Aldebaran walk
so that precise step length control can be activated when required. An open loop trajectory mapping
approach is taken to the walk that is stabilized statically through the use of a phase varying joint
holding torque technique. We also examine the basic princples of open loop walking, focussing on the
commonly overlooked frontal plane motion.
The act of kicking itself is explored both analytically and empirically, and solutions are provided
that are versatile and powerful. Included as an appendix, the broader matter of striker behaviour
(process of goal scoring) is reviewed and we present a velocity control algorithm that is very accurate
and efficient in terms of speed of execution
Desenvolvimento de comportamentos para robô humanoide
Mestrado em Engenharia de Computadores e TelemáticaHumanoid robotics is an area of active research. Robots with human body
are better suited to execute tasks in environments designed for humans.
Moreover, people feel more comfortable interacting with robots that have
a human appearance. RoboCup encourages robotic research by promoting
robotic competitions. One of these competitions is the Standard Platform
League (SPL) in which humanoid robots play soccer. The robot used is
the Nao robot, created by Aldebaran Robotics. The di erence between
the teams that compete in this league is the software that controls the robots.
Another league promoted by RoboCup is the 3D Soccer Simulation
League (3DSSL). In this league the soccer game is played in a computer
simulation. The robot model used is also the one of the Nao robot. However,
there are a few di erences in the dimensions and it has one more
Degree of Freedom (DoF) than the real robot. Moreover, the simulator
cannot reproduce reality with precision. Both these leagues are relevant
for this thesis, since they use the same robot model. The objective of this
thesis is to develop behaviors for these leagues, taking advantage of the
previous work developed for the 3DSSL. These behaviors include the basic
movements needed to play soccer, namely: walking, kicking the ball, and
getting up after a fall. This thesis presents the architecture of the agent
developed for the SPL, which is similar to the architecture of the FC Portugal
team agent from the 3DSSL, hence allowing to port code between both
leagues easily. It was also developed an interface that allows to control a
leg in a more intuitive way. It calculates the joint angles of the leg, using
the following parameters: three angles between the torso and the line connecting
hip and ankle; two angles between the foot and the perpendicular
of the torso; and the distance between the hip and the ankle. It was also
developed an algorithm to calculate the three joint angles of the hip that
produce the desired vertical rotation, since the Nao robot does not have a
vertical joint in the hip. This thesis presents also the behaviors developed
for the SPL, some of them based on the existing behaviors from the 3DSSL.
It is presented a behavior that allows to create robot movements by de ning
a sequence of poses, an open-loop omnidirectional walking algorithm, and
a walk optimized in the simulator adapted to the real robot. Feedback was
added to this last walk to make it more robust against external disturbances.
Using the behaviors presented in this thesis, the robot achieved a forward
velocity of 16 cm/s, a lateral velocity of 6 cm/s, and rotated at 40 deg/s.
The work developed in this thesis allows to have an agent to control the
Nao robot and execute the basic low level behaviors for competing in the
SPL. Moreover, the similarities between the architecture of the agent for
the SPL with that of the agent from the 3DSSL allow to use the same high
level behaviors in both leagues.A robótica humanoide é uma área em ativo desenvolvimento. Os robôs com
forma humana estão melhor adaptados para executarem tarefas em ambientes
desenhados para humanos. Além disso, as pessoas sentem-se mais
confortáveis quando interagem com robôs que tenham aparência humana.
O RoboCup incentiva a investigação na área da robótica através da realização de competições de robótica. Uma destas competições é a Standard
Platform League (SPL) na qual robôs humanoides jogam futebol. O robô
usado é o robô Nao, criado pela Aldebaran Robotics. A diferença entre as
equipas que competem nesta liga está no software que controla os robôs.
Outra liga presente no RoboCup é a 3D Soccer Simulation League (3DSSL).
Nesta liga o jogo de futebol é jogado numa simulação por computador. O
modelo de robô usado é também o do robô Nao. Contudo, existem umas
pequenas diferenças nas dimensões e este tem mais um grau de liberdade do
que o robô real. O simulador também não consegue reproduzir a realidade
com perfeição. Ambas estas ligas são importantes para esta dissertação,
pois usam o mesmo modelo de robô. O objectivo desta dissertação é desenvolver
comportamentos para estas ligas, aproveitando o trabalho prévio
desenvolvido para a 3DSSL. Estes comportamentos incluem os movimentos
básicos necessários para jogar futebol, nomeadamente: andar, chutar a bola
e levantar-se depois de uma queda. Esta dissertação apresenta a arquitetura
do agente desenvolvida para a SPL, que é similar á arquitetura do agente
da equipa FC Portugal da 3DSSL, para permitir uma mais fácil partilha de
código entre as ligas. Foi também desenvolvida uma interface que permite
controlar uma perna de maneira mais intuitiva. Ela calcula os ângulos das
juntas da perna, usando os seguintes parâmetros: três ângulos entre o torso
e a linha que une anca ao tornozelo; dois ângulos entre o pé e a perpendicular
do torso; e a distância entre a anca e o tornozelo. Nesta dissertação foi
também desenvolvido um algoritmo para calcular os três ângulos das juntas
da anca que produzam a desejada rotação vertical, visto o robô Nao não
ter uma junta na anca que rode verticalmente. Esta dissertação também
apresenta os comportamentos desenvolvidos para a SPL, alguns dos quais
foram baseados nos comportamentos já existentes na 3DSSL. É apresentado
um modelo de comportamento que permite criar movimentos para o robô
de nindo uma sequência de poses, um algoritmo para um andar open-loop e
omnidirecional e um andar otimizado no simulador e adaptado para o robô
real. A este último andar foi adicionado um sistema de feedback para o
tornar mais robusto. Usando os comportamentos apresentados nesta dissertação, o robô atingiu uma velocidade de 16 cm/s para frente, 6 cm/s para
o lado e rodou sobre si pr oprio a 40 graus/s. O trabalho desenvolvido nesta
dissertação permite ter um agente que controle o robô Nao e execute os
comportamentos básicos de baixo nível para competir na SPL. Além disso,
as semelhan cas entre a arquitetura do agente para a SPL com a arquitetura
do agente da 3DSSL permite usar os mesmos comportamentos de alto nível
em ambas as ligas
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
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