We have developed a multichannel electrogmyography sensor system capable of receiving and processing signals from up to 32 implanted myoelectric sensors (IMES). The appeal of implanted sensors for myoelectric control is that electromyography (EMG) signals can be measured at their source providing relatively cross-talk-free signals that can be treated as independent control sites. An external telemetry controller receives telemetry sent over a transcutaneous magnetic link by the implanted electrodes. The same link provides power and commands to the implanted electrodes. Wireless telemetry of EMG signals from sensors implanted in the residual musculature eliminates the problems associated with percutaneous wires, such as infection, breakage, and marsupialization. Each implantable sensor consists of a custom-designed application-specified integrated circuit that is packaged into a bio-compatible RF BION capsule from the Alfred E. Mann Foundation. Implants are designed for permanent long-term implantation with no servicing requirements. We have a fully operational system. The system has been tested in animals. Implants have been chronically implanted in the legs of three cats and are still completely operational four months after implantation.
Abstract. The design of exoskeletons is a popular and promising area of research both for restoring lost function and rehabilitation, and for augmentation in military and industrial applications. A major practical challenge to the comfort and usability for exoskeletons is the need to avoid misalignment of the exoskeletal joint with the underlying human joint. Alignment mismatches are difficult to prevent due to large inter-user variability, and can create large stresses on the attachment system and underlying human anatomy. Previous self-aligning systems have been proposed in literature, which can compensate for muscle forces, but leave large residual forces passed directly to the skeletal system. In this paper we propose a new mechanism to reduce misalignment complications. A decoupling approach is proposed which allows large forces to be carried by the exoskeletal system while allowing both the muscle and skeletal joint force presented to the user to be compensated to any desired degree.
We trained a rhesus monkey to perform randomly cued, individuated finger flexions of the thumb, index, and middle finger. Nine Implantable MyoElectric Sensors (IMES) were then surgically implanted into the finger muscles of the monkey's forearm, without any observable adverse chronic effects. Using an inductive link, we wirelessly recorded EMG from the IMES as the monkey performed a finger flexion task. A principal components analysis (PCA) based algorithm was used to decode which finger switch was pressed based on the recorded EMG. This algorithm correctly decoded which finger was moved 89% of the time. These results demonstrate that IMES offer a safe and highly promising approach for providing intuitive, dexterous control of artificial limbs and hands after amputation.
Haptic transparency is an extensively studied subject in teleoperation. However, the exact role of transparency in human-in-the-loop task execution is only partially understood. In this study, a human factors experiment was performed with the goal to assess the effect of transparency on the rate and generalizability of motor learning. Subjects performed a reach adaptation task under the effect of a viscous curl force field, while two levels of transparency were provided, namely (near) natural transparency and reduced transparency based on a bilateral position-error controller. In the 'familiarization' stage subjects performed an eight cm planar movement in a straight line without any external dynamics. In the 'learning' stage, subjects performed the same movement, but now under the effect of a viscous curl force field. Finally, subjects were instructed to 'generalize' their learning of the force field for a comparable movement in a different position and orientation.The results show that, while the rate of learning and steadystate performance of a task may not benefit from the highest level of transparency, the ability to generalize beyond a set of preexperienced motions increases when haptic transparency is (close to) natural. It is concluded that haptic transparency may allow for more rapid and more accurate behaviour in situations that have not yet been encountered.
When human operators employ robotic lifting aids, haptic feedback about the lifted object is important. In an experimental study we manipulated two factors that influence haptic feedback to the operator: the percentage of compensated weight, and the way the lifted object is held: robocentric (the human hand lifting the robot that holds the object) or anthropocentric (the robot lifting the human who holds the object). We hypothesize that directly holding the object (anthropocentric approach) will improve the realized trajectories when rapidly lifting partly compensated weights. Subjects (n=10) performed a fast semi-repetitive lifting task, lifting a 4kg object to a designated target in either an anthropocentric or robocentric lifting scenario, at different levels (50% -75% -95%) of weight compensation. The anthropocentric approach yielded significantly smaller mean over-or under-shoot compared to robocentric lifting, especially for the first trials. The difference increased for higher levels of compensation. We conclude that for fast lifting, the anthropocentric approach better helps subjects to estimate the required forces to move the weight to the target, especially for unexpected movements at high levels of compensation.
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