129 research outputs found
The Rice Haptic Rocker: Skin stretch haptic feedback with the Pisa/IIT SoftHand
Touch provides an important cue to perceive the physical properties of the external objects. Recent studies showed that tactile sensation also contributes to our sense of hand position and displacement in perceptual tasks. In this study, we tested the hypothesis that, sliding our hand over a stationary surface, tactile motion may provide a feedback for guiding hand trajectory. We asked participants to touch a plate having parallel ridges at different orientations and to perform a self-paced, straight movement of the hand. In our daily-life experience, tactile slip motion is equal and opposite to hand motion. Here, we used a well-established perceptual illusion to dissociate, in a controlled manner, the two motionestimates. According to previous studies, this stimulus produces
a bias in the perceived direction of tactile motion, predicted by tactile flow model. We showed a systematic deviation in the movement of the hand towards a direction opposite to the one predicted by tactile flow, supporting the hypothesis that touch contributes to motor control of the hand. We suggested a model where the perceived hand motion is equal to a weighted sum of the estimate from classical proprioceptive cues (e.g., from musculoskeletal system) and the estimate from tactile slip
Pouring by Feel: An Analysis of Tactile and Proprioceptive Sensing for Accurate Pouring
As service robots begin to be deployed to assist humans, it is important for
them to be able to perform a skill as ubiquitous as pouring. Specifically, we
focus on the task of pouring an exact amount of water without any environmental
instrumentation, that is, using only the robot's own sensors to perform this
task in a general way robustly. In our approach we use a simple PID controller
which uses the measured change in weight of the held container to supervise the
pour. Unlike previous methods which use specialized force-torque sensors at the
robot wrist, we use our robot joint torque sensors and investigate the added
benefit of tactile sensors at the fingertips. We train three estimators from
data which regress the poured weight out of the source container and show that
we can accurately pour within 10 ml of the target on average while being robust
enough to pour at novel locations and with different grasps on the source
container
A Perspective on Cephalopods Mimicry and Bioinspired Technologies toward Proprioceptive Autonomous Soft Robots
Octopus skin is an amazing source of inspiration for bioinspired sensors, actuators and control solutions in soft robotics. Soft organic materials, biomacromolecules and protein ingredients in octopus skin combined with a distributed intelligence, result in adaptive displays that can control emerging optical behavior, and 3D surface textures with rough geometries, with a remarkably high control speed (âms). To be able to replicate deformable and compliant materials capable of translating mechanical perturbations in molecular and structural chromogenic outputs, could be a glorious achievement in materials science and in the technological field. Soft robots are suitable platforms for soft multi-responsive materials, which can provide them with improved mechanical proprioception and related smarter behaviors. Indeed, a system provided with a âlearning and recognitionâ functions, and a constitutive âmechanicalâ and âmaterial intelligenceâ can result in an improved morphological adaptation in multi-variate environments responding to external and internal stimuli. This review aims to explore challenges and opportunities related to smart and chromogenic responsive materials for adaptive displays, reconfigurable and programmable soft skin, proprioceptive sensing system, and synthetic nervous control units for data processing, toward autonomous soft robots able to communicate and interact with users in open-world scenarios
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Soft Morphological Computation
Soft Robotics is a relatively new area of research, where progress in material science has powered the next generation of robots, exhibiting biological-like properties such as soft/elastic tissues, compliance, resilience and more besides. One of the issues when employing soft robotics technologies is the soft nature of the interactions arising between the robot and its environment. These interactions are complex, and the their dynamics are non-linear and hard to capture with known models. In this thesis we argue that complex soft interactions
can actually be beneficial to the robot, and give rise to rich stimuli which can be used for the resolution of robot tasks. We further argue that the usefulness of these interactions depends on statistical regularities, or structure, that appear in the stimuli. To this end, robots should appropriately employ their morphology and their actions, to influence the system-environment interactions such that structure can arise in the stimuli. In this thesis we show that learning processes can be used to perform such a task. Following this rationale, this thesis proposes and supports the theory of Soft Morphological Computation (SoMComp), by which a soft robot should appropriately condition, or âaffectâ, the soft interactions to improve the quality of the physical stimuli arising from it. SoMComp is composed of four main principles, i.e.: Soft Proprioception, Soft Sensing, Soft Morphology and Soft Actuation. Each of these principles is explored in the context of haptic object recognition or object handling in soft robots. Finally, this thesis provides an overview of this research and its future directions.AHDB CP17
Design Considerations for 3D Printed, Soft, Multimaterial Resistive Sensors for Soft Robotics
Sensor design for soft robots is a challenging problem because of the wide range of design parameters (e.g., geometry, material, actuation type, etc.) critical to their function. While conventional rigid sensors work effectively for soft robotics in specific situations, sensors that are directly integrated into the bodies of soft robots could help improve both their exteroceptive and interoceptive capabilities. To address this challenge, we designed sensors that can be co-fabricated with soft robot bodies using commercial 3D printers, without additional modification. We describe an approach to the design and fabrication of compliant, resistive soft sensors using a Connex3 Objet350 multimaterial printer and investigated an analytical comparison to sensors of similar geometries. The sensors consist of layers of commercial photopolymers with varying conductivities. We characterized the conductivity of TangoPlus, TangoBlackPlus, VeroClear, and Support705 materials under various conditions and demonstrate applications in which we can take advantage of these embedded sensors
Model-free Soft-Structure Reconstruction for Proprioception using Tactile Arrays
Continuum body structures provide unique opportunities for soft robotics, with the infinite degrees of freedom
enabling unconstrained and highly adaptive exploration and manipulation. However, the infinite degrees of freedom of continuum
bodies makes sensing (both intrinsically and extrinsically) challenging. To address this, in this paper we propose a model-free
method for sensorizing tentacle-like continuum soft-structures
using an array of spatially arranged capacitive tactile sensors.
By using visual tracking, the relationship between the tactile
response and the 3D shape of the continuum soft-structure can be
learned. A data set of 15000 random soft-body postures was used,
with recorded camera-tracked positions logged synchronously to
the tactile sensor responses. This was used to train a neural
network which can predict posture. We show it is possible to
achieve proprioceptive awareness over all three axis of motion
in space, reconstructing the body structure and inferring the
soft body headâs pose with an average accuracy of â 1mm in
comparison to the visual tracked counterpart. To demonstrate
the capabilities of the system, we perform random exploration
of environments limiting the work-space of the sensorized robot.
We find the method capable to autonomously reconstruct the
reachable morphology of the environment without the need of
external sensing units.This work was funded by the UK Agriculture and Horticulture Development
Board (CP 172) and Physical Sciences Research Council (EPSRC) MOTION
grant [EP/N03211X/2
On the development of a cybernetic prosthetic hand
The human hand is the end organ of the upper limb, which in humans serves the important
function of prehension, as well as being an important organ for sensation and communication.
It is a marvellous example of how a complex mechanism can be implemented,
capable of realizing very complex and useful tasks using a very effective combination of
mechanisms, sensing, actuation and control functions.
In this thesis, the road towards the realization of a cybernetic hand has been presented.
After a detailed analysis of the model, the human hand, a deep review of the state of the
art of artificial hands has been carried out. In particular, the performance of prosthetic
hands used in clinical practice has been compared with the research prototypes, both for
prosthetic and for robotic applications. By following a biomechatronic approach, i.e. by
comparing the characteristics of these hands with the natural model, the human hand, the
limitations of current artificial devices will be put in evidence, thus outlining the design
goals for a new cybernetic device.
Three hand prototypes with a high number of degrees of freedom have been realized and
tested: the first one uses microactuators embedded inside the structure of the fingers, and
the second and third prototypes exploit the concept of microactuation in order to increase
the dexterity of the hand while maintaining the simplicity for the control. In particular, a
framework for the definition and realization of the closed-loop electromyographic control of
these devices has been presented and implemented.
The results were quite promising, putting in evidence that, in the future, there could
be two different approaches for the realization of artificial devices. On one side there
could be the EMG-controlled hands, with compliant fingers but only one active degree of
freedom. On the other side, more performing artificial hands could be directly interfaced
with the peripheral nervous system, thus establishing a bi-directional communication with
the human brain
Mesure tactile proprioceptive pour des doigts sous-actionnés
RĂSUMĂ
La prĂ©hension et la manipulation dâobjets par des robots deviennent de plus en plus rĂ©pandues dans divers domaines, et ce, pour de multiples applications. Lâutilisation de robots permet dâamĂ©liorer la rĂ©pĂ©tabilitĂ©, la rapiditĂ© et la prĂ©cision lors de certaines tĂąches, et ce, comparativement aux performances dâun opĂ©rateur humain. De plus, un robot peut Ă©galement
ĂȘtre conçu pour accomplir certaines tĂąches quâune personne ne pourrait effectuer, que ce soit au niveau de la force nĂ©cessaire ou du manque dâespace pour manoeuvrer. Des robots peuvent Ă©galement plus aisĂ©ment fonctionner dans des environnements hostiles. Tout comme
pour lâĂȘtre humain, la rĂ©troaction tactile est particuliĂšrement utile et mĂȘme inĂ©vitable pour effectuer certaines tĂąches. Il faut toutefois souligner quâil sâagit dâun thĂšme de recherche oĂč lâon est encore bien loin dâavoir atteint les performances humaines. Pour sâen approcher, de nombreuses et diverses technologies de capteurs tactiles existent, mais chacune comporte ses
dĂ©fauts. Ainsi, bien quâil existe actuellement des solutions technologiques pour donner une rĂ©troaction sensorielle Ă un robot ou Ă son opĂ©rateur, ces derniĂšres sâavĂšrent gĂ©nĂ©ralement coĂ»teuses, prĂ©sentent diffĂ©rents dĂ©fauts au niveau de la sensibilitĂ© et ne sont pas toujours adaptĂ©es Ă certaines utilisations.
Dans lâoptique de trouver une alternative efficace aux technologies conventionnelles de dĂ©tection et de mesure tactiles, la prĂ©sente thĂšse se concentre sur la possibilitĂ© dâutiliser la raideur inhĂ©rente du mĂ©canisme de transmission dâun doigt sous-actionnĂ©. En effet, les doigts et les mains sous-actionnĂ©s sont de plus en plus communĂ©ment utilisĂ©s pour leur simplicitĂ© propre et leur capacitĂ© Ă saisir et Ă sâadapter Ă la forme dâobjet de maniĂšre purement mĂ©canique sans schĂ©ma de commande complexe ou de nombreux actionneurs. Contrairement aux mĂ©canismes pleinement actionnĂ©s, les doigts sous-actionnĂ©s, communĂ©ment appelĂ©s adaptatifs, comportent des Ă©lĂ©ments passifs pour contraindre leur mouvement avant le contact, tout en permettant dâobtenir une prise stable sans dĂ©velopper des forces de contact trop Ă©levĂ©es
initialement.
Les doigts sous-actionnĂ©s Ă©tant gĂ©nĂ©ralement dĂ©pourvus dâactionneurs Ă lâintĂ©rieur du doigt lui-mĂȘme, les seuls capteurs dĂ©jĂ prĂ©sents sont typiquement situĂ©s Ă lâunique actionneur. Toutefois, en analysant et traitant en temps rĂ©el les donnĂ©es de ces capteurs internes, Ă©galement
appelĂ©s proprioceptifs, il est possible dâextraire une panoplie dâinformations sur ce qui se passe au niveau des phalanges. Ce principe est donc utilisĂ© pour obtenir des algorithmes de dĂ©tection tactile pouvant ĂȘtre utilisĂ©s sur diffĂ©rents systĂšmes, tels quâune pince compliante
et un préhenseurs à membrures.----------ABSTRACT
Robotic hands have become more and more prevalent in many fields. They have replaced human operators in many repetitive applications where robots become more precise and efficient. Moreover, robotic graspers can lift heavier loads and accomplish maneuvers a human could not. They can also manipulate objects in hostile environments where it would be dangerous for humans. Therefore, a lot of work has been done in recent years to improve their capabilities such as their speed, dexterity, strength, and versatility. However, current robotic manipulators lack the sensory feedback of their human counterparts. Indeed, haptic and tactile feedbacks are still very limited in current devices, which may be a problem, because tactile sensing is deemed nearly mandatory for a large number of applications. Conventional tactile sensors, which are usually applied on the external surface of a robot, are generally used, but they can also be costly, insensitive to some dynamic phenomena, and not adequate to some applications.
To solve these issues, many authors have worked on finding alternatives to standard tactile sensors. This thesis fits in this current trend by focusing on the possibility of using the internal stiffness of underactuated fingers to design a virtual tactile sensor. This technique is referred to as proprioceptive tactile sensing. It is applied here to underactuated robotics
fingers, which are becoming prevalent in many fields. Underactuated mechanisms, sometimes referred to as self-adaptive, are particularly interesting because of their intrinsic ability to mechanically adapt themselves to the shape of an object without complex control laws and
as low as only one actuator. As they have by definition less actuators, they generally have no sensor in the fingerâs mechanism itself. Instead of adding new sensors, it is possible to take advantage of the sensors already present, such as the ones at the actuator.
Therefore, in this thesis, only data provided by sensors at the actuator is used. Since a oneto-one relationship exists between the contact location and the instantaneous stiffness of the mechanism, it is possible to compute one from the other. Therefore, with the measurements from sensors at the actuator, it is possible to estimate the point of contact. To this aim, a complete model is proposed and experimental data is provided. Different algorithms were tested successfully on a compliant biocompatible gripper and a 2-DOF linkage-driven finger.
Finally, an optimization procedure is presented with the aim of finding the optimal parameters of the transmission mechanism to improve the sensitivity of the virtual tactile sensor. The data presented in this thesis demonstrate the robustness of the proposed proprioceptive
tactile sensing (PTS) technique
Dual-Modality Haptic Feedback Improves Dexterous Task Execution with Virtual EMG-Controlled Gripper
Upper-extremity amputees who use myoelectric prostheses currently lack the
haptic sensory information needed to perform dexterous activities of daily
living. While considerable research has focused on restoring this haptic
information, these approaches often rely on single-modality feedback schemes
which are necessary but insufficient for the feedforward and feedback control
strategies employed by the central nervous system. Multi-modality feedback
approaches have been gaining attention in several application domains, however,
the utility for myoelectric prosthesis use remains unclear. In this study, we
investigated the utility of dual-modality haptic feedback in a virtual
EMG-controlled grasp-and-hold task with a brittle object and variable load
force. We recruited N=20 non-amputee participants to perform the task in four
conditions: no feedback, vibration feedback of incipient slip, squeezing
feedback of grip force, and dual (vibration + squeezing) feedback of incipient
slip and grip force. Results suggest that receiving any feedback is better than
receiving none, however, dual-modality feedback is far superior to either
single-modality feedback approach in terms of preventing the object from
breaking or dropping, even after it started slipping. Control with
dual-modality feedback was also seen as more intuitive than with either of the
single-modality feedback approaches
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