Nowadays technology is increasingly present in our everyday lives, and among the emerging technologies those oriented to the reproduction of tactile, kinesthetic and skin sensations are getting interest in several application fields.These technologies allow enriching the sensory experience of humans, for instance immersed in virtual environments, in augmented or mixed-reality applications and/or during teleoperation tasks.Recent studies available in literature confirm that the use of tactile technologies not only increases the involvement of users in teleoperation tasks but also increases their accuracy and performance. Interesting applications of haptic technologies are also present in telemedicine and in tele-rehabilitation, these applications became particularly significant in the last year, when the pandemic situation required solutions for guaranteeing social distance and human/human physical contacts.&nbsp;Although the hand is one of the primary interfaces between humans and the surrounding environment, most of the haptic devices that return tactile stimuli are located on the fingers or on the wrist, while few of them are developed specifically for the palm.Among the main haptic devices on the palm we find the grounded ones, having a base external to the user’s body and connected to a fixed base. The research in this topic is&nbsp; increasingly oriented towards wearable devices to free the user and not limit his workspace.To date, wearability is a fundamental requirement for haptic devices, and in this context the compromise between the extension of the area of the palm that can be stimulated, and the number of actuators used is almost inevitable.Through this work we want to present a haptic wearable device for rendering forces in the palm that attempt to find a trade-off between the aforementioned requirements.The State-of-the-art devices are mostly based on localized and fixed contact points on the palm. Among these, there are two main typologies of devices: devices based on vibrotactile actuations, and devices using mechanical actuations. The last ones usually employ tightening bands reproducing only a normal pressure on the palm, allowing the user to feel a limited and predetermined type of sensations.The aim of this work is to present a device able to stimulate a large area of the palm by containing the number of actuators and preserving the wearability constraint. In order to achieve these objectives a mobile platform with interchangeable palm interfaces is designed. The various interfaces, which differ in shape, can be easily connected and disconnected to/from the device to reproduce a tactile sensation more similar to the desired stimulus in different tasks.Inspired from a family of wearable devices that we developed for fingertip stimulation, the mobile platform has a "Y" shape and it is actuated by three servomotors positioned on the back of the hand by means of tendons, allowing the transmission motion. In order to provide to the user the possibility to easily wear the device and avoid the continuous contact with the palm, we added a set of&nbsp; springs at the base of the platform. The tendons and the springs allow us to reproduce the cutaneous stimulus both in static and dynamic conditions. The use of three actuators furthermore allows reproducing both normal and tangential components of the contact force (necessary for simulating shear forces), and the contact with virtual/remote surfaces with different orientations (that can be used for instance for reproducing the contact variable curvature surfaces).In the extended version of the paper we will: i) describe the haptic device based on tendons taking into account the physical/anatomical features of the palm;ii) present the design of interchangeable modules for simulations of different types of contact;iii) detail the mechanical, mechatronics and manufacturing aspects of the device (including FEM analysis, hardware and control description);iv) present a working prototype of the device with some preliminary tests.&nbsp;

Design of a Wearable and Modular Haptic Device for Hand Palm Cutaneous Feedback

Paper Proceedings: https://asmedigitalcollection.asme.org/IMECE/IMECE2021/volume/85543

ASME 2021 International Mechanical Engineering Congress and Exposition (IMECE2021)

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