129 research outputs found
Highly dynamic robotic leg for non-biomimetic walking robots
Due to a predisposition of DNA to generate symmetric anatomy, there are no tripedal animals in nature. Yet, threelegged walking might be the sweet spot between the energy efficiency of bipeds and the stability of quadrupeds. This paper presents the non-biomimetic leg for the TriPed, a novel three-legged mobile walking robot that aims to study the advantages and disadvantages of three-legged walking. We showcase its new non-biomimetic leg design that allows for fast repositioning by keeping the leg mass close to the body. This is done using physical experiments as well as a simscape simulation. The experiments show that the legs are capable of moving about 3 m/s
Bimanual Motor Strategies and Handedness Role During Human-Exoskeleton Haptic Interaction
Bimanual object manipulation involves multiple visuo-haptic sensory feedbacks
arising from the interaction with the environment that are managed from the
central nervous system and consequently translated in motor commands. Kinematic
strategies that occur during bimanual coupled tasks are still a scientific
debate despite modern advances in haptics and robotics. Current technologies
may have the potential to provide realistic scenarios involving the entire
upper limb extremities during multi-joint movements but are not yet exploited
to their full potential. The present study explores how hands dynamically
interact when manipulating a shared object through the use of two
impedance-controlled exoskeletons programmed to simulate bimanually coupled
manipulation of virtual objects. We enrolled twenty-six participants (2 groups:
right-handed and left-handed) who were requested to use both hands to grab
simulated objects across the robot workspace and place them in specific
locations. The virtual objects were rendered with different dynamic proprieties
and textures influencing the manipulation strategies to complete the tasks.
Results revealed that the roles of hands are related to the movement direction,
the haptic features, and the handedness preference. Outcomes suggested that the
haptic feedback affects bimanual strategies depending on the movement
direction. However, left-handers show better control of the force applied
between the two hands, probably due to environmental pressures for right-handed
manipulations
Preliminary design and control of a soft exosuit for assisting elbow movements and hand grasping in activities of daily living
The development of a portable assistive device to aid patients affected by neuromuscular disorders has been the ultimategoal of assistive robots since the late 1960s. Despite significant advances in recent decades, traditional rigid exoskeletonsare constrained by limited portability, safety, ergonomics, autonomy and, most of all, cost. In this study, we present thedesign and control of a soft, textile-based exosuit for assisting elbow flexion/extension and hand open/close. We describea model-based design, characterisation and testing of two independent actuator modules for the elbow and hand,respectively. Both actuators drive a set of artificial tendons, routed through the exosuit along specific load paths, thatapply torques to the human joints by means of anchor points. Key features in our design are under-actuation and the useof electromagnetic clutches to unload the motors during static posture. These two aspects, along with the use of 3Dprinted components and off-the-shelf fabric materials, contribute to cut down the power requirements, mass and overallcost of the system, making it a more likely candidate for daily use and enlarging its target population. Low-level control isaccomplished by a computationally efficient machine learning algorithm that derives the system’s model from sensorydata, ensuring high tracking accuracy despite the uncertainties deriving from its soft architecture. The resulting system isa low-profile, low-cost and wearable exosuit designed to intuitively assist the wearer in activities of daily living
Long Exciton Dephasing Time and Coherent Phonon Coupling in CsPbBrCl Perovskite Nanocrystals
Fully-inorganic cesium lead halide perovskite nanocrystals (NCs) have shown
to exhibit outstanding optical properties such as wide spectral tunability,
high quantum yield, high oscillator strength as well as blinking-free single
photon emission and low spectral diffusion. Here, we report measurements of the
coherent and incoherent exciton dynamics on the 100 fs to 10 ns timescale,
determining dephasing and density decay rates in these NCs. The experiments are
performed on CsPbBrCl NCs using transient resonant three-pulse four-wave
mixing (FWM) in heterodyne detection at temperatures ranging from 5 K to 50 K.
We found a low-temperature exciton dephasing time of 24.51.0 ps, inferred
from the decay of the photon-echo amplitude at 5 K, corresponding to a
homogeneous linewidth (FWHM) of 545 {\mu}eV. Furthermore, oscillations in
the photon-echo signal on a picosecond timescale are observed and attributed to
coherent coupling of the exciton to a quantized phonon mode with 3.45 meV
energy
Adaptive model-based myoelectric control for a soft wearable arm exosuit:A new generation of wearable robot control
Despite advances in mechatronic design, the widespread adoption of wearable robots for supporting human mobility has been hampered by 1) ergonomic limitations in rigid exoskeletal structures and 2) the lack of human-machine interfaces (HMIs) capable of sensing musculoskeletal states and translating them into robot-control commands. We have developed a framework that combines, for the first time, a model-based HMI with a soft wearable arm exosuit that has the potential to address key limitations in current HMIs and wearable robots. The proposed framework was tested on six healthy subjects who performed elbow rotations across different joint velocities and lifting weights. The results showed that the model-controlled exosuit operated synchronously with biological muscle contraction. Remarkably, the exosuit dynamically modulated mechanical assistance across all investigated loads, thereby displaying adaptive behavior
Environment-based Assistance Modulation for a Hip Exosuit via Computer Vision
Just like in humans vision plays a fundamental role in guiding adaptive
locomotion, when designing the control strategy for a walking assistive
technology, Computer Vision may bring substantial improvements when performing
an environment-based assistance modulation. In this work, we developed a hip
exosuit controller able to distinguish among three different walking terrains
through the use of an RGB camera and to adapt the assistance accordingly. The
system was tested with seven healthy participants walking throughout an
overground path comprising of staircases and level ground. Subjects performed
the task with the exosuit disabled (Exo Off), constant assistance profile
(Vision Off ), and with assistance modulation (Vision On). Our results showed
that the controller was able to promptly classify in real-time the path in
front of the user with an overall accuracy per class above the 85%, and to
perform assistance modulation accordingly. Evaluation related to the effects on
the user showed that Vision On was able to outperform the other two conditions:
we obtained significantly higher metabolic savings than Exo Off, with a peak of
about -20% when climbing up the staircase and about -16% in the overall path,
and than Vision Off when ascending or descending stairs. Such advancements in
the field may yield to a step forward for the exploitation of lightweight
walking assistive technologies in real-life scenarios
A robot-aided visuomotor wrist training induces gains in proprioceptive and movement accuracy in the contralateral wrist
Proprioceptive training is a neurorehabilitation approach known to improve proprioceptive acuity and motor performance of a joint/limb system. Here, we examined if such learning transfers to the contralateral joints. Using a robotic exoskeleton, 15 healthy, right-handed adults (18-35 years) trained a visuomotor task that required making increasingly small wrist movements challenging proprioceptive function. Wrist position sense just-noticeable-difference thresholds (JND) and spatial movement accuracy error (MAE) in a wrist-pointing task that was not trained were assessed before and immediately as well as 24 h after training. The main results are: first, training reduced JND thresholds (- 27%) and MAE (- 33%) in the trained right wrist. Sensory and motor gains were observable 24 h after training. Second, in the untrained left wrist, mean JND significantly decreased (- 32%) at posttest. However, at retention the effect was no longer significant. Third, motor error at the untrained wrist declined slowly. Gains were not significant at posttest, but MAE was significantly reduced (- 27%) at retention. This study provides first evidence that proprioceptive-focused visuomotor training can induce proprioceptive and motor gains not only in the trained joint but also in the contralateral, homologous joint. We discuss the possible neurophysiological mechanism behind such sensorimotor transfer and its implications for neurorehabilitation
Physiological and kinematic effects of a soft exosuit on arm movements
Background: Soft wearable robots (exosuits), being lightweight, ergonomic and low power-demanding, are attractive for a variety of applications, ranging from strength augmentation in industrial scenarios, to medical assistance for people with motor impairments. Understanding how these devices affect the physiology and mechanics of human movements is fundamental for quantifying their benefits and drawbacks, assessing their suitability for different applications and guiding a continuous design refinement.
Methods: We present a novel wearable exosuit for assistance/augmentation of the elbow and introduce a controller that compensates for gravitational forces acting on the limb while allowing the suit to cooperatively move with its wearer. Eight healthy subjects wore the exosuit and performed elbow movements in two conditions: with assistance from the device (powered) and without assistance (unpowered). The test included a dynamic task, to evaluate the impact of the assistance on the kinematics and dynamics of human movement, and an isometric task, to assess its influence on the onset of muscular fatigue.
Results: Powered movements showed a low but significant degradation in accuracy and smoothness when compared to the unpowered ones. The degradation in kinematics was accompanied by an average reduction of 59.20±5.58% (mean ± standard error) of the biological torque and 64.8±7.66% drop in muscular effort when the exosuit assisted its wearer. Furthermore, an analysis of the electromyographic signals of the biceps brachii during the isometric task revealed that the exosuit delays the onset of muscular fatigue.
Conclusions: The study examined the effects of an exosuit on the characteristics of human movements. The suit supports most of the power needed to move and reduces the effort that the subject needs to exert to counteract gravity in a static posture, delaying the onset of muscular fatigue. We interpret the decline in kinematic performance as a technical limitation of the current device. This work suggests that a powered exosuit can be a good candidate for industrial and clinical applications, where task efficiency and hardware transparency are paramount
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