708 research outputs found
Human-Robot Interaction Through Fingertip Haptic Devices for Cooperative Manipulation Tasks
No full textTeleoperation of multi-robot systems, e.g. dual manipulators, in cooperative manipulation tasks requires haptic feedback of multi-contact interaction forces. Classical haptic devices restrict the workspace of the human operator and provide only one contact point. An alternative solution is to enable the operator to command the robot system via free-hand motions which extends the workspace of the human. In such a setting, a multi-contact haptic feedback may be provided to the human through multiple wearable haptic devices, e.g. fingertip devices that display forces on the human fingertips. In this paper we evaluate the benefit of using wearable haptic fingertip devices to interact with a bimanual robot setup in a pick-and-place manipulation task. We show that haptic feedback through wearable devices improves task performance compared to the base condition of no haptic feedback. Therefore, wearable haptic devices are a promising interface for guidance of multi-robot manipulation systems
Haptic Communications
No full textSteinbach E, Hirche S, Ernst MO, et al. Haptic Communications. PROCEEDINGS OF THE IEEE, FRONTIERS OF AUDIOVISUAL COMMUNICATIONS. In Press;100(4):937-956.Audiovisual communications is at the core of multimedia
systems that allow users to interact across distances. It is
common understanding that both audio and video are required
for high quality interaction. While audiovisual information provides
a user with a satisfactory impression of being present in
a remote environment, physical interaction and manipulation
is not supported. True immersion into a distant environment
and efficient distributed collaboration require the ability to
physically interact with remote objects and to literally get in
touch with other people. Touching and manipulating objects
remotely becomes possible if we augment traditional audiovisual
communications by the haptic modality. Haptic communications
is a relatively young field of research that has the potential
to substantially improve Human-Human and Human-Machine-
Interaction. In this paper we discuss the state-of-the-art in haptic
communications both from a psychophysical and technical point
of view. From a human perception point of view, we mainly focus
on the multimodal integration of audio, video and haptics and
the improved performance that can be achieved when combining
them.We also discuss how the human adapts to discrepancies and
synchronization errors between different modalities, a research
area which is typically referred to as perceptual learning. From
a technical perspective, we address perceptual coding of haptic
information and the transmission of haptic data streams over
resource-constrained and potentially lossy networks in the presence
of unpredictable and time-varying communication delays.
In this context, we also discuss the need for objective quality
metrics for haptic communication. Throughout the paper we
stress the fact that haptic communications is not meant as
a replacement of traditional audiovisual communications but
rather as an additional dimension for telepresence that will allow
us to advance in our quest for truly immersive communication
Invariance Control with Chattering Reduction
No full textIn many control applications, state and/or output constraints need to be satisfied. For that purpose, artificial limits are imposed using a specially designed control law. Among other methods, invariance control has proven valuable for addressing the problem of state and output constraints in nonlinear control systems. However, invariance controlled systems often exhibit undesirable chattering behavior in particular in digital implementation. In this work, we propose a novel invariance-based control approach, which significantly reduces chattering. We give a condition for stability and restrictions on the admissible constraint configuration. The approach and the results are illustrated in simulations
Effects of a future warmer ocean on the coexisting copepods Calanus finmarchicus and C. glacialis in Disko Bay, Western Greenland
No full textThe effects of temperature and food was examined for Calanus finmarchicus and C. glacialis during 3 phases of the phytoplankton spring bloom in Disko Bay, western Greenland. The 2 species were collected during pre-bloom, bloom, and post-bloom and exposed to temperatures from 0 to 10°C, combined with deficient or excess food. Fecal pellet and egg production were measured as indices for grazing and secondary production, respectively. Furthermore, changes in body carbon, nitrogen, and lipid content were measured. C. glacialis sampled before the bloom and incubated with excess food exhibited high specific egg production at temperatures between 0 and 2.5°C. Higher temperatures did not increase egg production considerably, whereas egg production for C. finmarchicus more than tripled between 2.5 and 5°C. Starved C. glacialis produced eggs at all temperatures stimulated by increasing temperatures, whereas starved C. finmarchicus needed temperatures above 5°C to produce eggs fueled by their lipid stores. Few C. finmarchicus had mature gonads at the initiation of the pre-bloom and bloom experiment, and egg production of C. finmarchicus therefore only increased as the ratio of individuals with mature gonads increased. During the bloom, both C. glacialis and C. finmarchicus used the high food availability for egg production, while refueling or exhausting their lipid stores, respectively. Finally, during the post-bloom experiment, production was low by C. finmarchicus, whereas C. glacialis had terminated production. Our results suggest that a future warmer ocean will reduce the advantage of early spawning by C. glacialis and that C. finmarchicus will become increasingly prevalen
Gaussian Processes for Dynamic Movement Primitives with Application in Knowledge-based Cooperation
No full textDynamic Movement Primitives (DMPs) represent stable goal-directed or periodic movements, which are learned from observations or demonstrations. They rely on proper function approximators, which are sufficiently flexible to represent arbitrary movements but also ensure goal convergence in pointto- point motions. This work shows that Gaussian Processes (GPs) are suitable as a regressor for learning movements with DMPs ensuring stability. In addition, GPs provide a measure for the uncertainty about the current movement, which we exploit by proposing a new cooperation scheme for DMPs: For better reproduction of demonstrations, we follow the intuition, that individuals with more knowledge lead towards the goal, while others follow and focus on cooperation. Along with simulation results, we validate the presented methods in a robotic cooperative object manipulation task
Event-based Scheduling of Multi-loop Stochastic Systems over Shared Communication Channels
No full textThis paper introduces a novel dynamic event-based
scheduling mechanism for networked control systems
(NCSs) composed of multiple linear heterogeneous stochastic
plants whose feedback loops are closed over a shared constrained
communication channel. Each subsystem competes for
the channel access in order to update its own controller with
true local state values. Employing an emulation-based control
policy, a probabilistic scheduler allocates the communication
resource according to a prioritized error-based (PEB) measure.
Based on this policy, a higher chance of transmission is assigned
to the subsystems with higher errors, while the other requests
are blocked when the channel capacity is reached. Under some
mild assumptions, the probabilistic nature of PEB scheduling
scheme facilitates an approximative decentralized implementation.
We evaluate the stochastic stability of the overall NCS
scheduled by PEB policy in terms of networked-induced error
ergodicity, by applying the drift criterion over a multi time-step
horizon. Moreover, we derive uniform performance bounds for
the networked-induced error variance, which demonstrates a
significant reduction in comparison with static and random
access scheduling schemes such as TDMA and CSMA
Lupin protein isolate versus casein modifies cholesterol excretion and mRNA expression of intestinal sterol transporters in a pig model
No full textAbstract
Background
Lupin proteins exert hypocholesterolemic effects in man and animals, although the
underlying mechanism remains uncertain. Herein we investigated whether lupin proteins
compared to casein modulate sterol excretion and mRNA expression of intestinal sterol
transporters by use of pigs as an animal model with similar lipid metabolism as humans, and
cellular cholesterol-uptake by Caco-2 cells.
Methods
Two groups of pigs were fed cholesterol-containing diets with either 230 g/kg of lupin
protein isolate from L. angustifolius or 230 g/kg casein, for 4 weeks. Faeces were collected
quantitatively over a 5 d period for analysis of neutral sterols and bile acids by gas
chromatographically methods. The mRNA abundances of intestinal lipid transporters were
analysed by real-time RT-PCR. Cholesterol-uptake studies were performed with Caco-2 cells
that were incubated with lupin conglutin γ, phytate, ezetimibe or albumin in the presence of
labelled [4-14C]-cholesterol.
Results
Pigs fed the lupin protein isolate revealed lower cholesterol concentrations in total plasma,
LDL and HDL than pigs fed casein (P < 0.05). Analysis of faeces revealed a higher output of
cholesterol in pigs that were fed lupin protein isolate compared to pigs that received casein
(+57.1%; P < 0.05). Relative mRNA concentrations of intestinal sterol transporters involved
in cholesterol absorption (Niemann-Pick C1-like 1, scavenger receptor class B, type 1) were
lower in pigs fed lupin protein isolate than in those who received casein (P < 0.05). In vitro
data showed that phytate was capable of reducing the uptake of labelled [4-14C]-cholesterol
into the Caco-2 cells to the same extend as ezetimibe when compared to control (−20.5% vs.
−21.1%; P < 0.05).
Conclusions
Data reveal that the cholesterol-lowering effect of lupin protein isolate is attributable to an
increased faecal output of cholesterol and a reduced intestinal uptake of cholesterol. The
findings indicate phytate as a possible biofunctional ingredient of lupin protein isolate.Background: Lupin proteins exert hypocholesterolemic effects in man and animals, although the underlying mechanism remains uncertain. Herein we investigated whether lupin proteins compared to casein modulate sterol excretion and mRNA expression of intestinal sterol transporters by use of pigs as an animal model with similar lipid metabolism as humans, and cellular cholesterol-uptake by Caco-2 cells. Methods. Two groups of pigs were fed cholesterol-containing diets with either 230 g/kg of lupin protein isolate from L. angustifolius or 230 g/kg casein, for 4 weeks. Faeces were collected quantitatively over a 5 d period for analysis of neutral sterols and bile acids by gas chromatographically methods. The mRNA abundances of intestinal lipid transporters were analysed by real-time RT-PCR. Cholesterol-uptake studies were performed with Caco-2 cells that were incubated with lupin conglutin γ, phytate, ezetimibe or albumin in the presence of labelled [4- 14C]-cholesterol. Results: Pigs fed the lupin protein isolate revealed lower cholesterol concentrations in total plasma, LDL and HDL than pigs fed casein (P < 0.05). Analysis of faeces revealed a higher output of cholesterol in pigs that were fed lupin protein isolate compared to pigs that received casein (+57.1%; P < 0.05). Relative mRNA concentrations of intestinal sterol transporters involved in cholesterol absorption (Niemann-Pick C1-like 1, scavenger receptor class B, type 1) were lower in pigs fed lupin protein isolate than in those who received casein (P < 0.05). In vitro data showed that phytate was capable of reducing the uptake of labelled [4- 14C]-cholesterol into the Caco-2 cells to the same extend as ezetimibe when compared to control (-20.5% vs. -21.1%; P < 0.05). Conclusions: Data reveal that the cholesterol-lowering effect of lupin protein isolate is attributable to an increased faecal output of cholesterol and a reduced intestinal uptake of cholesterol. The findings indicate phytate as a possible biofunctional ingredient of lupin protein isolate
Control of Networked Cyber-Physical Systems (Dagstuhl Seminar 19222)
No full textThis report documents the program and the outcomes of Dagstuhl Seminar 19222 "Control of Networked Cyber-Physical Systems".
Such systems typically operate under very tight timing constraints and at the same time witness an ever-increasing complexity in both size and the amount of information needed to main controllability.
Yet, the development of control systems and of communication/computation infrastructures has traditionally been decoupled, so that valuable insights from the respective other domain could not be used towards the joint goal of keeping cyber-physical systems (CPS) controllable.
In order to overcome this "black box" thinking, the seminar brought together researchers from the key communities involved in the development of CPS.
In a series of impulse talks and plenary discussions, the seminar reviewed the current start-of-the-art in CPS research and identified promising research directions that may benefit from closer cooperation between the communication and control communities
Live discrimination of Calanus glacialis and C. finmarchicus females: can we trust phenological differences?
No full textTwo key players in the Arctic and subarctic marine ecosystem are the calanoid copepods, Calanus finmarchicus and C. glacialis. Although morphologically very similar, these sibling species have different life cycles and roles in the Arctic pelagic marine ecosystem. Considering that the distribution of C. glacialis corresponds to Arctic water masses and C. finmarchicus to Atlantic water masses, the species are frequently used as climate indicators. Consequently, correct identification of the two species is essential if we want to understand climate-impacted changes on Calanus-dominated marine ecosystems such as the Arctic. Here, we present a novel morphological character (redness) to distinguish live females of C. glacialis and C. finmarchicus and compare it to morphological (prosome length) and genetic identification. The characters are tested on 300 live females of C. glacialis and C. finmarchicus from Disko Bay, western Greenland. Our analysis confirms that length cannot be used as a stand-alone criterion for separation. The results based on the new morphological character were verified genetically using a single mitochondrial marker (16S) and nuclear loci (six microsatellites and 12 InDels). The pigmentation criterion was also used on individuals (n = 89) from Young Sound fjord, northeast Greenland to determine whether the technique was viable in different geographical locations. Genetic markers based on mitochondrial and nuclear loci were corroborative in their identification of individuals and revealed no hybrids. Molecular identification confirmed that live females of the two species from Greenlandic waters, both East and West, can easily be separated by the red pigmentation of the antenna and somites of C. glacialis in contrast to the pale opaque antenna and somites of C. finmarchicus, confirming that the pigmentation criterion is valid for separation of the two specie
Robot team teleoperation for cooperative manipulation using wearable haptics
No full textRobot teams require planning and adaptive capabilities in order to perform cooperative manipulation tasks in dynamic or unstructured environments. Since these capabilities are inherent to humans, it is suitable to consider human-robot team teleoperation for cooperative manipulation where a single human collaborates with the robot team. In this paper, we present a subtask-based control approach which enables a simultaneous execution of two subtasks by the robot team, interacting with the object: trajectory tracking and formation preservation. Control inputs for both subtasks are provided by the human operator. The commands are projected onto the spaces of subtasks using a command mapping strategy. Analogously, measured interacting forces are projected onto the space of feedback signals, provided to the human via wearable fingertip haptic devices through a feedback mapping strategy. Experimental results validate the proposed approach
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