241 research outputs found
Controlling Dynamic Stability and Active Compliance to Improve Quadrupedal Walking
Summary. It is widespread the idea that animal legged locomotion improves
wheeled locomotion on very rough terrain. However, the use of legs as locomotion
system for vehicles and robots is still far away from competing with wheels
and trucks even on natural ground. Walking robots feature two main disadvantages.
One is the lack of reacting capabilities from external disturbances, and the other is
the very slow walking motion. Both obstacles prevent walking mechanisms from being
introduced in industrial processes and from being part of service and assistance
robotics. This paper is aimed at solving the two above obstacles by combining a dynamic
stability margin that quantifies the impact energy that a robot can withstand,
and either controlling a dynamic walk by means of active compliance, which helps
the robot react to disturbances. Experiments performed on the SILO4 quadruped robot show a relevant improvement on the walking gait.This work has been partially funded by CICYT (Spain) through Grant
DPI2004-05824. The first author is supported by a postdoctoral CSIC-I3P
contract granted by the European Social Fund.Peer reviewe
Neuro-mechanical entrainment in a bipedal robotic walking platform
In this study, we investigated the use of van der Pol oscillators in a 4-dof embodied bipedal robotic platform for the purposes of planar walking. The oscillator controlled the hip and knee joints of the robot and was capable of generating waveforms with the correct frequency and phase so as to entrain with the mechanical system. Lowering its oscillation frequency resulted in an increase to the walking pace, indicating exploitation of the global natural dynamics. This is verified by its operation in absence of entrainment, where faster limb motion results in a slower overall walking pace
Neuro-mechanical entrainment in a bipedal robotic walking platform
In this study, we investigated the use of van der Pol oscillators in a 4-dof embodied bipedal robotic platform for the purposes of planar walking. The oscillator controlled the hip and knee joints of the robot and was capable of generating waveforms with the correct frequency and phase so as to entrain with the mechanical system. Lowering its oscillation frequency resulted in an increase to the walking pace, indicating exploitation of the global natural dynamics. This is verified by its operation in absence of entrainment, where faster limb motion results in a slower overall walking pace
Multiple chaotic central pattern generators with learning for legged locomotion and malfunction compensation
An originally chaotic system can be controlled into various periodic
dynamics. When it is implemented into a legged robot's locomotion control as a
central pattern generator (CPG), sophisticated gait patterns arise so that the
robot can perform various walking behaviors. However, such a single chaotic CPG
controller has difficulties dealing with leg malfunction. Specifically, in the
scenarios presented here, its movement permanently deviates from the desired
trajectory. To address this problem, we extend the single chaotic CPG to
multiple CPGs with learning. The learning mechanism is based on a simulated
annealing algorithm. In a normal situation, the CPGs synchronize and their
dynamics are identical. With leg malfunction or disability, the CPGs lose
synchronization leading to independent dynamics. In this case, the learning
mechanism is applied to automatically adjust the remaining legs' oscillation
frequencies so that the robot adapts its locomotion to deal with the
malfunction. As a consequence, the trajectory produced by the multiple chaotic
CPGs resembles the original trajectory far better than the one produced by only
a single CPG. The performance of the system is evaluated first in a physical
simulation of a quadruped as well as a hexapod robot and finally in a real
six-legged walking machine called AMOSII. The experimental results presented
here reveal that using multiple CPGs with learning is an effective approach for
adaptive locomotion generation where, for instance, different body parts have
to perform independent movements for malfunction compensation.Comment: 48 pages, 16 figures, Information Sciences 201
An Overview of Legged Robots
The objective of this paper is to present the evolution and the state-of-theart in the area of legged locomotion systems. In a first phase different possibilities for mobile robots are discussed, namely the case of artificial legged locomotion systems, while emphasizing their advantages and limitations. In a second phase an historical overview of the evolution of these systems is presented, bearing in mind several particular cases often considered as milestones on the technological and scientific progress. After this historical timeline, some of the present day systems are examined and their performance is analyzed. In a third phase are pointed out the major areas for research and development that are presently being followed in the construction of legged robots. Finally, some of the problems still unsolved, that remain defying robotics research, are also addressed.N/
Postural control on a quadruped robot using lateral tilt : a dynamical system approach
Autonomous adaptive locomotion over irregular terrain is one important
topic in robotics research. Postural control, meaning movement generation
for robot legs in order to attain balance, is a first step in this
direction. In this article, we focus on the essential issue of modeling the
interaction between the central nervous system and the peripheral information
in the locomotion context. This issue is crucial for autonomous
and adaptive control, and has received little attention so far. This modeling
is based on the concept of dynamical systems whose intrinsic robustness
against perturbations allows for an easy integration of sensory-motor
feedback and thus for closed-loop control. Herein, we focus on achieving
balance without locomotion.
The developed controller is modeled as discrete, sensory driven corrections
of the robot joint values in order to achieve balance. The robot
lateral tilt information modulates the generated trajectories thus achieving
balance. The system is demonstrated on a quadruped robot which
adjusts its posture until reducing the lateral tilt to a minimum.(undefined
Sagittal tilt control of a quadruped robot using a dynamical systems approach
Autonomous adaptive locomotion over irregular terrain is one important topic in
robotics research. Balance control, meaning movement generation for robot legs, is a first step
in this direction. In this article, we focus on the essential issue of modeling the interaction
between the central nervous system and the peripheral information in the locomotion context.
This is an important issue for autonomous and adaptive control, and has received little
attention so far. This modeling is based on the concept of dynamical systems whose intrinsic
robustness against perturbations allows for an easy integration of sensory-motor feedback
and thus for closed-loop control. In this article, balance is achieved without locomotion.
The developed controller is modeled as discrete, sensory driven corrections of the robot joint
values. The robot sagittal tilt information modulates the generated trajectories thus achieving
balance. The system is demonstrated on a quadruped robot which adjusts its posture until
reducing the sagittal tilt to a minimum
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