Observing Motor Impairment using the Cave Automatic Virtual Environment (CAVE) to Guide Soft Exosuit Design Steven Lessard1 , Leya Breanna Baltaxe-Admony1 , Ash Robbins1 , Kevin Le1 , Mircea Teodorescu1 , and Sri Kurniawan1∗ 1. INTRODUCTION Soft exosuits can potentially promote and augment human motion while passively retaining structural compliance and flexibility. These traits are important for applications where users require additional strength or guidance but must retain a full range of motion. One such application of this technology is within the field of physical therapy. The design and implementation of these exosuits, however, is a difficult problem. In this extended abstract, we propose a system for designing soft exosuits based upon the quantitative motion capturing afforded by a virtual reality environment known as the Cave Automatic Virtual Environment (CAVE). We then illustrate an early prototype for the design of a soft upper-limb exosuit.

2. MOTION CAPTURE

Figure 1. The Cave Automatic Virtual Environment (CAVE) for 3D motion capture and virtual reality display.

3. SOFT EXOSUIT DESIGN

The CAVE is a platform enclosed by three walls, upon each of which (and the floor) is projected an image (Figure 1). These images are streamed live from an associated computer. Additionally, the CAVE is equipped with four infrared cameras, positioned such that any reflectively coated object can be viewed in three dimension. Using an associated master computer equipped with the correct software, these cameras can track the motion of a user wearing reflective trackers.

The results from these exploratory measurements prompted the design for a form-fitting, shoulderaccentuated, structurally compliant, flexible and lightweight exosuit. Similar to some pre-exsiting soft exosuits [2,3], movement generated by the suit is cabledriven. This suit uses seven independent lengths of braided-aramid fishing line to pull above the skin on a neoprene base layer in parallel with designated muscles (Figure 3).

Users can don these reflective trackers and perform motions that quantitatively illustrate their mobility (Figure 2). These motions, such as those from the QuickDASH metric [1], can highlight which muscles are not properly supporting the measured person. As a result, the focus of an exosuit to meet the user’s needs can be determined for future manufacturing.

This type of technology can potentially be used to customize exosuits to individuals’ needs. As particular muscles are targeted, a user can be instructed to wear their unique exosuit as it caters to their particular needs.

∗1 University

of California, Santa Cruz, Santa Cruz, CA 95064

4. ACKNOWLEDGMENT We would like to thank all the participants for volunteering in the user study.

(a) Participant with injured rotator cuff

(b) In this graph, the motion of the particpant’s impaired arm is compared to that of her unimpaired arm. Specifically, this graph shows the hand tracking node with respect to time.

Figure 2. A participant with an injured rotator cuff demonstrates simple arm movements as they are tracked by the CAVE.

References [1] P. E. Mintken, P. Glynn, and J. A. Cleland, “Psychometric properties of the shortened disabilities of the arm, shoulder, and hand questionnaire (quickdash) and numeric pain rating scale in patients with shoulder pain,” Journal of Shoulder and Elbow Surgery, vol. 18, no. 6, pp. 920–926, 2009. [2] R. D. Kornbluh, A. S. Kernbaum, T. Low, K. G. Witherspoon, B. K. McCoy, A. A. E. Ziemba, P. M. Birkmeyer, and R. M. Mahoney, “Exosuit system,” Feb. 23 2016, uS Patent 9,266,233. [3] M. Wehner, B. Quinlivan, P. M. Aubin, E. MartinezVillalpando, M. Baumann, L. Stirling, K. Holt, R. Wood, and C. Walsh, “A lightweight soft exosuit for gait assistance,” in Robotics and Automation (ICRA), 2013 IEEE International Conference on. IEEE, 2013, pp. 3362– 3369.

Figure 3. A soft upper-limb exosuit that uses seven cables to articulate arm movement. Cables can independently pull to augment bicep flexion, tricep flexion, pronation, suppination, and anterior, middle, and posterior deltoid flexion. Additionally, three CAVE-trackable nodes are placed on the suit to verify suit effect on users.