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Soft Wearable Haptic Devices

3-DoF Wearable, Pneumatic Haptic Device to Deliver Normal, Shear, Vibration, and Torsion Feedback

Haptic devices worn on the forearm have the ability to provide communication while freeing the user’s hands for manipulation tasks. We introduce a multi-modal haptic device with a rigid rotational housing and three soft fiber-constrained linear pneumatic actuators. Soft pneumatic actuators are used because of their compliance, light weight, and simplicity, while rigid components provide robust and precise control. The soft pneumatic actuators provide linear horizontal and vertical movements, and the rigid housing, affixed to a motor, provides rotational movement of the tactor. The device can produce normal, shear, vibration, and torsion skin deformation cues by combining the movement of the soft pneumatic actuators with the rotational housing. The tactor is able to provide a shear force of up to 0.47 N and a normal force of up to 1.3 N. To elucidate the physical design principle and the actuation strategy, the static force and displacement of the soft tactor are modeled as a function of material, design parameters, and pressure. The models were validated experimentally.

More Detail:

K. Yoshida, C.M. Nunez, S.R. Williams, A.M. Okamura, and M. Luo. “3-DoF Wearable, Pneumatic Haptic Device to Deliver Normal, Shear, Vibration, and Torsion Feedback”, IEEE World Haptics Conference. (2019).


Design and Analysis of Pneumatic 2-DoF Soft Haptic Devices for Shear Display

Haptic devices use touch to enable communication in a salient and private manner. While most haptic devices are held or worn at the hand, there is recent interest in developing wearable haptic devices for the arms. This frees the hands for manipulation tasks, but creates challenges for wearability. One approach is to use pneumatically driven soft haptic devices that, compared to rigid devices, can be more readily worn due to their form factor and light weight. We propose a 2-degree of freedom (2-DOF) pneumatic soft linear tactor that can be mounted on the forearm and provide shear force. The tactor is comprised of four soft fiber-constrained linear pneumatic actuators connected to a dome-shaped tactor head. The tactor can provide fast, repeatable forces on the order of 1 N in shear, in various directions in the plane of the skin surface. We demonstrate the trade-offs of two housing schemes, one soft and one rigid, that mount the pneumatic soft linear actuator to the forearm. A user study demonstrated the performance of both versions of the device in providing directional cues, highlighting the challenges and importance of grounding soft wearable devices and the difficulties of designing haptic devices given the perceptual limits of the human forearm.

More Detail:

S. Kanjanapas, C.M. Nunez, S.R. Williams, A.M. Okamura, and M. Luo. “Design and Analysis of Pneumatic 2-DoF Soft Haptic Devices for Shear Display ”, IEEE Robotics and Automation Letters (2019).


A Soft Robotic Wearable Wrist Device for Kinesthetic Haptic Feedback

Advances in soft robotics provide a unique approach for delivering haptic feedback to a user by a soft wearable device. Such devices can apply forces directly on the human joints, while still maintaining the safety and flexibility necessary for use in close proximity to the human body. To take advantage of these properties, we present a new haptic wrist device using pressure-driven soft actuators called reverse pneumatic artificial muscles (rPAMs) mounted on four sides of the wrist. These actuators are originally pre-strained and release compressive stress under pressure, applying a safe torque around the wrist joints while being compact and portable, representing the first soft haptic device capable of real-time feedback. To demonstrate the functional utility of this device, we created a virtual path-following task, wherein the user employs the motion of their wrist to control their embodied agent. We used the haptic wrist device to assist the user in following the path and study their performance with and without haptic feedback in multiple scenarios. Our results quantify the effect of wearable soft robotic haptic feedback on user performance. Specifically, we observed that our haptic feedback system improved the performance of users following complicated paths in a statistically significant manner, but did not show improvement for simple linear paths. Based on our findings, we anticipate broader applications of wearable soft robotic haptic devices toward intuitive user interactions with robots, computers, and other users.

EH. Skorina, M. Luo, and C. D. Onal. “A Soft Robotic Wearable Wrist Device for Kinesthetic Haptic Feedback.” Frontiers in Robotics and AI 5 (2018): 83.