5,402 research outputs found
Fast Damage Recovery in Robotics with the T-Resilience Algorithm
Damage recovery is critical for autonomous robots that need to operate for a
long time without assistance. Most current methods are complex and costly
because they require anticipating each potential damage in order to have a
contingency plan ready. As an alternative, we introduce the T-resilience
algorithm, a new algorithm that allows robots to quickly and autonomously
discover compensatory behaviors in unanticipated situations. This algorithm
equips the robot with a self-model and discovers new behaviors by learning to
avoid those that perform differently in the self-model and in reality. Our
algorithm thus does not identify the damaged parts but it implicitly searches
for efficient behaviors that do not use them. We evaluate the T-Resilience
algorithm on a hexapod robot that needs to adapt to leg removal, broken legs
and motor failures; we compare it to stochastic local search, policy gradient
and the self-modeling algorithm proposed by Bongard et al. The behavior of the
robot is assessed on-board thanks to a RGB-D sensor and a SLAM algorithm. Using
only 25 tests on the robot and an overall running time of 20 minutes,
T-Resilience consistently leads to substantially better results than the other
approaches
A Dynamics and Stability Framework for Avian Jumping Take-off
Jumping take-off in birds is an explosive behaviour with the goal of
providing a rapid transition from ground to airborne locomotion. An effective
jump is predicated on the need to maintain dynamic stability through the
acceleration phase. The present study concerns understanding how birds retain
control of body attitude and trajectory during take-off. Cursory observation
suggests that stability is achieved with relatively little cost. However,
analysis of the problem shows that the stability margins during jumping are
actually very small and that stability considerations play a significant role
in selection of appropriate jumping kinematics. We use theoretical models to
understand stability in prehensile take-off (from a perch) and also in
non-prehensile take-off (from the ground). The primary instability is tipping,
defined as rotation of the centre of gravity about the ground contact point.
Tipping occurs when the centre of pressure falls outside the functional foot. A
contribution of the paper is the development of graphical tipping stability
margins for both centre of gravity location and acceleration angle. We show
that the nose-up angular acceleration extends stability bounds forward and is
hence helpful in achieving shallow take-offs. The stability margins are used to
interrogate simulated take-offs of real birds using published experimental
kinematic data from a guinea fowl (ground take-off) and a diamond dove (perch
take-off). For the guinea fowl the initial part of the jump is stable, however
simulations exhibit a stuttering instability not observed experimentally that
is probably due to absence of compliance in the idealised joints. The diamond
dove model confirms that the foot provides an active torque reaction during
take-off, extending the range of stable jump angles by around 45{\deg}.Comment: 21 pages, 11 figures; supplementary material:
https://figshare.com/s/86b12868d64828db0d5d; DOI: 10.6084/m9.figshare.721056
Design and Development of an Affordable Haptic Robot with Force-Feedback and Compliant Actuation to Improve Therapy for Patients with Severe Hemiparesis
The study describes the design and development of a single degree-of-freedom haptic robot, Haptic Theradrive, for post-stroke arm rehabilitation for in-home and clinical use. The robot overcomes many of the weaknesses of its predecessor, the TheraDrive system, that used a Logitech steering wheel as the haptic interface for rehabilitation. Although the original TheraDrive system showed success in a pilot study, its wheel was not able to withstand the rigors of use. A new haptic robot was developed that functions as a drop-in replacement for the Logitech wheel. The new robot can apply larger forces in interacting with the patient, thereby extending the functionality of the system to accommodate low-functioning patients. A new software suite offers appreciably more options for tailored and tuned rehabilitation therapies. In addition to describing the design of the hardware and software, the paper presents the results of simulation and experimental case studies examining the system\u27s performance and usability
Rapid inversion: running animals and robots swing like a pendulum under ledges.
Escaping from predators often demands that animals rapidly negotiate complex environments. The smallest animals attain relatively fast speeds with high frequency leg cycling, wing flapping or body undulations, but absolute speeds are slow compared to larger animals. Instead, small animals benefit from the advantages of enhanced maneuverability in part due to scaling. Here, we report a novel behavior in small, legged runners that may facilitate their escape by disappearance from predators. We video recorded cockroaches and geckos rapidly running up an incline toward a ledge, digitized their motion and created a simple model to generalize the behavior. Both species ran rapidly at 12-15 body lengths-per-second toward the ledge without braking, dove off the ledge, attached their feet by claws like a grappling hook, and used a pendulum-like motion that can exceed one meter-per-second to swing around to an inverted position under the ledge, out of sight. We discovered geckos in Southeast Asia can execute this escape behavior in the field. Quantification of these acrobatic behaviors provides biological inspiration toward the design of small, highly mobile search-and-rescue robots that can assist us during natural and human-made disasters. We report the first steps toward this new capability in a small, hexapedal robot
In silico case studies of compliant robots: AMARSI deliverable 3.3
In the deliverable 3.2 we presented how the morphological computing ap-
proach can significantly facilitate the control strategy in several scenarios,
e.g. quadruped locomotion, bipedal locomotion and reaching. In particular,
the Kitty experimental platform is an example of the use of morphological
computation to allow quadruped locomotion. In this deliverable we continue
with the simulation studies on the application of the different morphological
computation strategies to control a robotic system
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