Keehoon Kim

Robotic touch shifts perception of embodiment to a prosthesis in targeted reinnervation amputees

Existing prosthetic limbs do not provide amputees with cutaneous feedback. Tactile feedback is essential to intuitive control of a prosthetic limb and it is now clear that the sense of body self-identification is also linked to cutaneous touch. Here we have created an artificial sense of touch for a prosthetic limb by coupling a pressure sensor on the hand through a robotic stimulator to surgically redirected cutaneous sensory nerves (targeted reinnervation) that once served the lost limb. We hypothesize that providing physiologically relevant cutaneous touch feedback may help an amputee incorporate an artificial limb into his or her self image. To investigate this we used a robotic touch interface coupled with a prosthetic limb and tested it with two targeted reinnervation amputees in a series of experiments fashioned after the Rubber Hand Illusion. Results from both subjective (self-reported) and objective (physiological) measures of embodiment (questionnaires, psychophysical temporal order judgements and residual limb temperature measurements) indicate that returning physiologically appropriate cutaneous feedback from a prosthetic limb drives a perceptual shift towards embodiment of the device for these amputees. Measurements provide evidence that the illusion created is vivid. We suggest that this may help amputees to more effectively incorporate an artificial limb into their self image, providing the possibility that a prosthesis becomes not only a tool, but also an integrated body part.Passivity theory has been used for the past decade to derive stability conditions for human/machine interface applications. Demonstrating passivity of the haptic display implies stable and safe interaction for the human user. At the heart of the stability analysis is the physical dissipation provided by the haptic device, as it plays a key role in the design process for all components. This paper will derive the condition that the haptic device must satisfy in order to achieve passivity of the haptic display. These results will be used to investigate a general nonlinear device model.

On the Design of Miniature Haptic Devices for Upper Extremity Prosthetics

We have developed three different versions of a multifunction haptic device that can display touch, pressure, vibration, shear force, and temperature to the skin of an upper extremity amputee, especially the one who has undergone targeted nerve reinnervation (TR) surgery. In TR patients, sensation from the reinnervated skin is projected to the missing hand. This paper addresses the design of the mechanical display, the portion responsible for contact, pressure, vibration, and shear force. A variety of different overall design approaches satisfying the design specifications and the performance requirements are considered. The designs of the fully prototyped haptic devices are compared through open-loop frequency response, closed-loop force response, and tapping response in constrained motion. We emphasize the tradeoffs between key design factors, including force capability, workspace, size, bandwidth, weight, and mechanism complexity.

Haptic Feedback Enhances Grip Force Control of sEMG-Controlled Prosthetic Hands in Targeted Reinnervation Amputees

In this study, we hypothesized that haptic feedback would enhance grip force control of surface electromyography (sEMG)-controlled prosthetic hands for targeted reinnervation (TR) amputees. A new miniature haptic device, a tactor, that can deliver touch, pressure, shear, and temperature sensation, allows modality-matching haptic feedback. TR surgery that creates sensory regions on the patients skin that refer to the surface of the missing limb allows somatotopic-matching haptic feedback. This paper evaluates the hypothesis via an sEMG-controlled virtual prosthetic arm operated by TR amputees under diverse haptic feedback conditions. The results indicate that the grip force control is significantly enhanced via the haptic feedback. However, the simultaneous display of two haptic channels (pressure and shear) does not enhance, but instead degrades, grip force control.

Reaction of WC-Co coating with molten zinc in a zinc pot of a continuous galvanizing line

Abstract In a continuous galvanizing line (CGL), three so-called pot rolls are usually used to guide steel strips in a zinc pot. Generally zinc pot rolls are coated with WC–Co to protect the pot roll surface from severe corrosion by molten zinc. The degradation process of the WC–Co coating was evaluated through analyses of coated pot rolls used in a CGL zinc pot for 33 and 56 days. The rolls were coated by high velocity oxygen fuel spraying with WC–12% Co powders that were produced through sintering and crushing processes. On the surface of the WC–Co coated rolls, several types of deposits were observed including top dross (Fe2Al5 inter-metallic compound) that might induce dross defect on the surface of galvanized steel. The diffusion depth of zinc into the WC–Co coating used for 33 days was only 10 μm, but some areas were severely attacked along cracks within the coating layer because of a preferential reaction with aluminum. Through SEM study, we observed that not only zinc but also aluminum diffused into the WC–Co coating after being in the zinc pot for 56 days. In some cases, Al–Fe–Zn layers were observed on the surface of the spray coating. Those layers were analyzed to be Fe2Al5 as their chemical compositions are very similar to those of Fe2Al5 top dross. However, they are not the Fe2Al5 dross, but the reaction products between molten zinc and the coating layer according to their morphologies.

Quantitative Comparison of Bilateral Teleoperation Systems Using

This paper presents a quantitative comparison framework for bilateral teleoperation systems (BTSs) that have different dynamic characteristics and sensory configurations for a given task-dependent performance objective (TDPO). mu-synthesis is used to develop the framework since it can efficiently treat systems containing uncertainties and disturbances. The framework consists of: 1) a feasibility test and 2) a comparison methodology using prioritized TDPOs. As the formulation used is based on mu-synthesis, the system, operator, and environment models are represented in the form of linear nominal models with frequency-dependent multiplicative uncertainties. This framework is applied to a BTS including an uncertain human operator and environment in a practical case study. The validity of the proposed quantitative framework is confirmed through experiments. The proposed framework can be used as a tool to design BTSs, especially when there are constraints in designing drive mechanisms and choosing sensory configurations.

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The range of human kinematic motion as well as force resolution should be known for design of a haptic device. In addition, a haptic interface can be designed more easily when master and slave devices are the same kinematically. However, human kinematic factors have not been analyzed and applied deeply because of their complexity. Although calibration techniques have been developed, there is a limit to describe the dexterous motion. In this paper haptic manipulation which uses the tactile sensing more often than the visual sensing is defined and analyzed. During haptic manipulation, thumb and the wrist are the most important. The thumb model described has only two variables to be calibrated and successfully expresses opposition which is a unique thumb motion of human. Through this model, the workspace of thumb and three finger grasping haptic manipulation are determined. Especially, this result can be a criterion to design a haptic device which expresses human dexterous motion.

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Purpose – The purpose of this paper is to present a surgical robot for spinal fusion and its control framework that provides higher operation accuracy, greater flexibility of robot position control, and improved ergonomics.Design/methodology/approach – A human‐guided robot for the spinal fusion surgery has been developed with a dexterous end‐effector that is capable of high‐speed drilling for cortical layer gimleting and tele‐operated insertion of screws into the vertebrae. The end‐effector is position‐controlled by a five degrees‐of‐freedom robot body that has a kinematically closed structure to withstand strong reaction force occurring in the surgery. The robot also allows the surgeon to control cooperatively the position and orientation of the end‐effector in order to provide maximum flexibility in exploiting his or her expertise. Also incorporated for improved safety is a “drill‐by‐wire” mechanism wherein a screw is tele‐drilled by the surgeon in a mechanically decoupled master/slave system. Finally, ...

Human kinematic factor for haptic manipulation : the wrist to thumb

There are two main limitations in the conventional robot-assisted spinal fusion surgery. Since the end effector in the state of art has a role of guiding the insertion pose of a screw only, i) convenience that can be obtained when the robot intervenes in the surgery more actively could be limited, ii) The insertion pose of a screw provided by the robots could be deteriorated by surgeons resisting force since he should insert a screw with his own hand withstanding the large reaction force transmitted through the drilling handle. To overcome those limitations, this paper proposes a novel approach for spinal fusion, wherein the robot performs the spinal fusion using the equipped end effector following surgeons guide. We developed a dexterous small-sized the end effector that can perform previous gimleting and screwing tasks into the vertebrae. A five-DOF robot body that has kinematically-closed structure guides the insertion pose of a screw and resists strong reaction force firmly during the screwing process. Based on admittance control framework, the surgeon controls the pose of the end effector precisely to compensate induced static/dynamic errors during the operation. A torque feedback method without torque sensor that suggests the haptic information about the status of drilling is also included. The performance of the CoRASS was verified by experiments.

Cooperative robotic assistant with drill‐by‐wire end‐effector for spinal fusion surgery

In this paper, we study energy harvesting from the mouse click motions of a robot finger and a human index finger using a piezoelectric material. The feasibility of energy harvesting from mouse click motions is experimentally and theoretically assessed. The fingers wear a glove with a pocket for including the piezoelectric material. We model the energy harvesting system through the inverse kinematic framework of parallel joints in a finger and the electromechanical coupling equations of the piezoelectric material. The model is validated through energy harvesting experiments in the robot and human fingers with the systematically varying load resistance. We find that energy harvesting is maximized at the matched load resistance to the impedance of the piezoelectric material, and the harvested energy level is tens of nJ.

Human-guided surgical robot system for spinal fusion surgery: CoRASS

Since bio-electric signals such as surface EMG are easily influenced by undesired artifacts and experimental environments including various electrical noises by peripheral devices, the amplifier is an issue of great importance. Although most commercial surface EMG amplifier systems provide high performance in acquiring electric bio-signals, they are not convenient for myoelectric control applications because they usually use wet-type electrodes that should be attached to the skin individually and there are also some limitations to possible modifications. In this study, we propose and develop a surface EMG interface that employs dry-type electrodes, a single supplied circuit for reduced weight, two voltage followers to improve input impedance, and a modified driven-right-leg circuit using a virtual ground circuit. By adapting a wearable band-type interface. The EMG electrodes can be reused while offering high performance corresponding to that of commercial products. The developed surface EMG system was successfully applied to decode human motion intentions of eight different configurations and a rest condition by using a fast training algorithms in a non-targeted manner.