Kinesthetic Haptic Device Research Articles

Human-centered design of a wearable kinesthetic haptic device for surgical teleoperation

Human-centered design of a wearable kinesthetic haptic device for surgical teleoperation

Human Perception of Wrist Flexion and Extension Torque During Upper and Lower Extremity Movement.

Real-world application of haptic feedback from kinesthetic devices is implemented while the user is in motion, but human wrist torque magnitude discrimination has previously only been characterized while users are stationary. In this study, we measured wrist torque discrimination in conditions relevant to activities of daily living, using a previously developed backdrivable wrist exoskeleton capable of applying wrist flexion and extension torque. We implemented a torque comparison test using a two-alternative forced-choice paradigm while participants were both seated and walking on a treadmill, with both a stationary and a moving wrist. Like most kinesthetic haptic devices, the wrist exoskeleton output torque is commanded in an open-loop manner. Thus, the study design was informed by Monte Carlo simulations to verify that the errors in the wrist exoskeleton output torque would not significantly affect the results. Results from ten participants show that although both walking and moving wrist conditions result in higher Weber Fractions (worse perception), participants were able to detect relatively small changes in torque of 12-19% on average in all grouped conditions. The results provide insight regarding the torque magnitudes necessary to make wrist-worn kinesthetic haptic devices noticeable and meaningful to the user in various conditions relevant to activities of daily living.

Enabling 4-DoF hand guidance using a portable haptic device exerting tangential force on the user's finger pads

Body-grounded kinesthetic haptic devices can provide cues for movement in multiple degrees of freedom by exerting forces directly on users, as in dexterous robot teleoperation tasks. However, these haptic devices have limited workspaces, can destabilize a teleoperation control loop, and can be expensive. Portable haptic devices can approximate the sensations of a kinesthetic device by exploiting diverse human sense of touch principles without these shortcomings. Our goal is to analyze the feasibility of hand guidance (HG) using tangential force stimuli. Here we reveal and quantify users’ interpretation of simultaneous tactile stimulation (STS) applied to multiple finger pads of the same hand. We completed an extensive experiment on different users to reveal a maximum number of understandable cues which can be used as movement commands for HG. As expected, many tactile stimuli tested were meaningless for users, but a few could be clearly interpreted — we call these “intuitive movement cues”. For the experiment, we designed a device that can be held in the palm and exerts tactile stimuli to the user's finger pads on the thumb and index fingers, or the thumb and middle fingers. We performed two studies in which we identified the extent of salience of different movement cues. In particular, commands to redirect the hand position and orientation in four axes: moving forward/backward, wrist twisting right/left (rotate clockwise/counter-clockwise), moving right/left, and wrist tilting up/down (rotate upwards/downwards). The results revealed that this approach provided 7 intuitive directional movement cues for relative HG in 3D space. The proposed HG principle is promising for applications such as robotic surgery training, laparoscopic training, and needle insertion training, during which surgical trainees must learn dexterous hand movements involving motion paths. There are many applications for 3D movement guidance outside the medical domain that could benefit from this haptics technology, including training for precise manipulation and assembly tasks, augmented teleoperation, and communication during shared control in collaborative human-machine systems.

Vibrotactile Display of Patterned Surface Textures With Kinesthetic Haptic Devices Using Balanced Impulses.

Kinesthetic haptic devices are designed primarily to display quasistatic and low-bandwidth forces and moments. Existing methods for vibrotactile display sometimes introduce haptic and/or audio artifacts. In this article, we propose a method to display vibrotactile stimulus signals of moderate to high frequency (20-500 Hz) using kinesthetic haptic devices with a standard 1 kHz haptic update rate. Our method combines symmetric square-wave signals whose periods are even multiples of the haptic update period with asymmetric square-wave signals whose periods are odd multiples of the haptic update period, while ensuring that the positive and negative impulses are balanced in both cases, and utilizing the just noticeable difference in frequency discrimination to avoid the need to display other frequencies. For frequencies at which the above method is insufficient, corresponding to a small band near 400 Hz for a 1 kHz update rate, we utilize a signal-mixing method. Our complete method is then extended to render haptic gratings by measuring scanning velocity, converting the local spatial frequency to its equivalent instantaneous temporal frequency, and displaying a single full-period vibration event. In a series of human-subject studies, we showed that our proposed method is preferred over existing methods for vibrotactile display of signals with relatively high-frequency content.

The effect of tactile augmentation on manipulation and grip force control during force-field adaptation

BackgroundWhen exposed to a novel dynamic perturbation, participants adapt by changing their movements’ dynamics. This adaptation is achieved by constructing an internal representation of the perturbation, which allows for applying forces that compensate for the novel external conditions. To form an internal representation, the sensorimotor system gathers and integrates sensory inputs, including kinesthetic and tactile information about the external load. The relative contribution of the kinesthetic and tactile information in force-field adaptation is poorly understood.MethodsIn this study, we set out to establish the effect of augmented tactile information on adaptation to force-field. Two groups of participants received a velocity-dependent tangential skin deformation from a custom-built skin-stretch device together with a velocity-dependent force-field from a kinesthetic haptic device. One group experienced a skin deformation in the same direction of the force, and the other in the opposite direction. A third group received only the velocity-dependent force-field.ResultsWe found that adding a skin deformation did not affect the kinematics of the movement during adaptation. However, participants who received skin deformation in the opposite direction adapted their manipulation forces faster and to a greater extent than those who received skin deformation in the same direction of the force. In addition, we found that skin deformation in the same direction to the force-field caused an increase in the applied grip-force per amount of load force, both in response and in anticipation of the stretch, compared to the other two groups.ConclusionsAugmented tactile information affects the internal representations for the control of manipulation and grip forces, and these internal representations are likely updated via distinct mechanisms. We discuss the implications of these results for assistive and rehabilitation devices.

Evolution and Analysis of Hapkit: An Open-Source Haptic Device for Educational Applications.

We present the design, evolution and analysis of "Hapkit," a low-cost, open-source kinesthetic haptic device for use in educational applications. Hapkit was developed in 2013 based on the design of the Stanford Haptic Paddle, with the goal of decreasing cost and increasing accessibility for educational applications, including online teaching, K-12 school use, and college dynamic systems and control courses. In order to develop Hapkit for these purposes, we tested a variety of transmission, actuation, and structural materials. Hapkit 3.0, the latest version, uses a capstan drive, inexpensive DC motor, and 3-D printed structural materials. A frequency-domain system identification method was used to characterize Hapkit dynamics across the various designs. This method was validated using a first principles parameter measurement and a transient response analysis. This characterization shows that Hapkit 3.0 has lower damping and Coulomb friction than previous designs. We also performed a user study demonstrating that Hapkit 3.0 improves discrimination of virtual stiffness compared to previous designs. The design evolution of Hapkit resulted in a low-cost, high-performance device appropriate for open-source dissemination and educational applications.

Effects of Different Hand-Grounding Locations on Haptic Performance With a Wearable Kinesthetic Haptic Device

Grounding of kinesthetic feedback against a user's hand can increase the portability and wearability of a haptic device. However, the effects of different hand-grounding locations on haptic perception of a user are unknown. In this letter, we investigate the effects of three different hand-grounding locations-back of the hand, proximal phalanx of the index finger, and middle phalanx of the index finger-on haptic perception using a newly designed wearable haptic device. The novel device can provide kinesthetic feedback to the user's index finger in two directions: along the finger-axis and in the finger's flexion-extension movement direction. We measure users' haptic perception for each grounding location through a psychophysical experiment for each of the two feedback directions. Results show that among the studied locations, grounding at proximal phalanx has a smaller average just noticeable difference for both feedback directions, indicating a more sensitive haptic perception. The realism of the haptic feedback, based on user ratings, was the highest with grounding at the middle phalanx for feedback along the finger axis, and at the proximal phalanx for feedback in the flexion-extension direction. Users identified the haptic feedback as most comfortable with grounding at the back of the hand for feedback along the finger axis and at the proximal phalanx for feedback in the flexion-extension direction. These findings show that the choice of grounding location has a significant impact on the user's haptic perception and qualitative experience. The results provide insights for designing next-generation wearable hand-grounded kinesthetic devices to achieve better haptic performance and user experience in virtual reality and teleoperated robotic applications.

Analytical Dynamic Analysis of a Kinesthetic Haptic Device

Marie Curie International Reintegration Grant within the 7th European Community Framework Programme

Toward a Future with Human Hands-Like Haptics: A Universal Framework for Interfacing Existing and Future Multipoint Haptic Devices

The two hands and ten fingers that humans are born with are the most dexterous parts of the body and the intrinsic tools that have created our history. To advance human-computer interaction so that we make use of such dexterity, an intuitive interface is highly desirable. Work in this field has led to the era of haptic interaction, yet the advances of haptic hardware and the corresponding software development kits (SDKs) have remained at the singlepoint stage for many years. Compared to the original intention of having multimanual, multifinger haptic devices that support both kinesthetic and tactile feedbacks, single-point kinesthetic haptic devices (SPHs) are a compromise between intuitive interactions and affordability. They are limited for probing-like operations and incapable of performing more sophisticated tasks. This limitation has caused the SPHs to lose much of their value in real-life applications where the dexterity that human hands possess is essential. Another reason for the slow transition from SPHs to multipoint haptic devices (MPHs) is the unique hardware designs and software implementations for MPHs. Unlike SPHs that share a rather similar architecture that can be easily abstracted for common communications, MPHs can be significantly different in their looks and the underlying interaction models, such as a multimanual model for collaborative hand manipulations and a multifinger model for pinch and grasp. The situation becomes even worse when considering incorporating both kinesthetic and tactile feedbacks together for more comprehensive systems, as these two are usually considered separate under existing hardware and SDK implementations, while they actually both belong to haptics and are interdependent on human hands.

Haptic Communication for a 2D Pointing Task in a Virtual Environment

This paper examines the properties of haptic communication between two human operators using kinesthetic haptic devices in a collaborative task in a virtual environment. Twenty subjects, divided into 10 dyads, participated in a 2D pointing task. Each dyad consisted of a supervisor and an acting agent. The supervisor’s role was to guide the acting agent towards a target in the virtual environment through either verbal or haptic communication only. Verbal communication was found to be the most efficient means of communication, but collaboration was also effective using haptic communication. Several different haptic communication strategies were observed, all with equal effectiveness as measured by task completion time. These strategies followed the same pattern as the verbal strategies. These results suggest that haptic communication in a virtual environment is possible, allowing for future designs of haptically enhanced collaborative work in virtual environments.