154 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
Gait-Behavior Optimization Considering Arm Swing and Toe Mechanisms for Biped Robot on Rough Road
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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
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Έμ΄λ λ‘λ΄ λ³΄ν ν¨ν΄μ μμ±νλ€.Foot slippage is one of the factors responsible for the increasing instability during human walking. A slip occurs when the horizontal shear force acting on the foot becomes greater than the frictional force between the foot and the ground, which is proportional to the vertical force. For humanoid robot walking, the possibility of a slip depends upon how the horizontal shear force and vertical force both acting on the foot are designed.
In the linear inverted pendulum model (LIPM), which is commonly used to generate the center of mass (COM) trajectory of humanoid robots, the vertical height of the COM is kept constant. The constant height of the COM restricts that the vertical force is always equal to the gravitational force at any walking speed. However, upon increasing the walking speed, the horizontal ground reaction force increases in proportion with the forward and lateral accelerations of the COM. This increase in the horizontal ground reaction force, while the vertical ground force is being constant, suggests that the robot-foot slippage can occur because of the restriction of the vertical motion by the LIPM constraint.
By generating the appropriate vertical motion, the robot-foot slippage can be reduced during humanoid robot walking. Researchers in the field of ergonomics have been conducted studies on the relationship between the available coefficient of friction (aCOF) and the utilized coefficient of friction (uCOF) to predict the potential for a slip during human walking. The aCOF is both the static and dynamic coefficient of friction between two objects in contact, and it depends on the properties of the objects. The uCOF is the ratio of the horizontal shear force to the vertical force applied by the supporting foot. Foot slippage occurs when the uCOF exceeds the aCOF. Various types of vertical motion can set the maximum value of the uCOF to be less than the aCOF between the foot and floor for humanoid robot walking. One of the simple and energy-efficient methods is to minimize the mechanical work of the COM by introducing added vertical motion. Therefore, the COM pattern would become more energy efficient by exchanging kinetic energy and potential energy.
This thesis aims to generate the appropriate vertical motion of the COM to maintain the utilized coefficient of friction (uCOF) less than the available coefficient of friction between the foot and the ground, and to minimize the mechanical work during humanoid robot walking. Before generating a slip-safe and energy-efficient COM trajectory for humanoid robot walking, studies on analyzing the COM patterns, mechanical work, and uCOF during human walking are conducted to understand the principle of walking. Vertical motions at various speeds are generated using an optimization method. Subsequently, the generated COM motion patterns are used as reference trajectories of the COM for humanoid robot walking. This thesis suggests a way to generate slip-safe and energy-efficient COM patterns, which, in turn, overcome the limitations of the LIPM by adding vertical COM motion.Chapter 1 Introduction 1
1.1 Research Background 1
1.2 Contributions of Thesis 3
1.3 Overviews of Thesis 4
Chapter 2 Dynamics of Walking 5
2.1 Walking Model 5
2.1.1 Linear Inverted Pendulum Model 5
2.1.2 Spring-Loaded Inverted Pendulum Model 6
2.1.3 Extrapolated Center of Mass Dynamics 9
2.2 Walking Theory 11
2.2.1 Step-to-Step Transition 11
Chapter 3 HumanWalking Analysis 13
3.1 Motion Capture for Walking 13
3.1.1 Motion Capture Technology 13
3.1.2 Joint Kinematics and Kinetics 15
3.2 Joint and COM During Human Walking 17
3.2.1 Introduction 17
3.2.2 Methods 19
3.2.3 Change of Joint Angle and the COM 20
3.2.4 Discussion 26
3.3 Slipping During Human Walking 27
3.3.1 Introduction 27
3.3.2 Methods 31
3.3.3 Change of uCOF and GRF 34
3.3.4 Interaction Effect Between Heel Area and Speed 36
3.3.5 Discussion 39
3.4 Mechanical Work During Human Walking 44
3.4.1 Introduction 44
3.4.2 Methods 46
3.4.3 Calculation for Joint Mechanical Work 48
3.4.4 Change of Joint Mechanical Work 51
3.4.5 Change of Stride Parameters 53
3.4.6 Discussion 54
Chapter 4 Robot Walking Pattern Generation 59
4.1 Introduction 59
4.2 Forward and Lateral COM 61
4.2.1 XcoM Method 61
4.2.2 Preview Control Method 63
4.3 Vertical COM 64
4.3.1 Calculation for uCOF 64
4.3.2 Calculation for ZMP 65
4.3.3 Calculation for COM Mechanical Work 66
4.3.4 Optimization for Vertical COM Generation 68
4.3.5 Results of Optimization for Vertical COM 73
4.4 Slipping During Robot Walking 75
4.4.1 Robot Simulation 75
4.4.2 Robot Experiments 77
4.5 Mechanical Work During Robot Walking 81
4.5.1 Robot Simulation 81
4.5.2 Robot Experiments 82
4.6 Discussion 87
4.6.1 Tracking Errors in Robot Experiments 87
4.6.2 Effect of Vertical Motions on Real Net Power 91
4.6.3 Trade-Off Between Efficiency and Stability 92
4.6.4 Difference Between Human and Robot 93
Chapter 5 Conclusions 95
Bibliography 97
Abstract (Korean) 111Docto
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
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