ExoKit: A Toolkit for Rapid Prototyping of Interactions for Arm-based Exoskeletons

TL;DR

ExoKit addresses the barrier to exploring human–exoskeleton interaction by providing a low-fidelity, modular, open-source toolkit tailored to novices. It combines easy-to-fabricate hardware with high-level functional abstractions for motion actuation, sensing, and augmentation, accessible through CLI, GUI, a Processing library, and Arduino firmware. The authors validate the approach with diverse applications and two usage studies, showing rapid prototyping, iterative design, and varied workflows, while highlighting wearability, customization, and safety considerations. The work advances early-stage interaction design in wearable robotics and offers a practical platform for education, experimentation, and creative exploration in HCI.

Abstract

Exoskeletons open up a unique interaction space that seamlessly integrates users' body movements with robotic actuation. Despite its potential, human-exoskeleton interaction remains an underexplored area in HCI, largely due to the lack of accessible prototyping tools that enable designers to easily develop exoskeleton designs and customized interactive behaviors. We present ExoKit, a do-it-yourself toolkit for rapid prototyping of low-fidelity, functional exoskeletons targeted at novice roboticists. ExoKit includes modular hardware components for sensing and actuating shoulder and elbow joints, which are easy to fabricate and (re)configure for customized functionality and wearability. To simplify the programming of interactive behaviors, we propose functional abstractions that encapsulate high-level human-exoskeleton interactions. These can be readily accessed either through ExoKit's command-line or graphical user interface, a Processing library, or microcontroller firmware, each targeted at different experience levels. Findings from implemented application cases and two usage studies demonstrate the versatility and accessibility of ExoKit for early-stage interaction design.

Figures (13)

• Figure 1: Degrees of freedom supported by ExoKit and the joints' ranges of motion (RoM) according to norkin_2016. The colored areas indicate the RoMs supported by ExoKit.
• Figure 2: ExoKit's key functionalities comprise basic functions and five augmentation strategies. They are conceptually organized in a two-dimensional space: Control determines whether the user is in full control of movement, is guided or constrained, or fully controlled by the exoskeleton. Augmentation complexity captures the degree of abstraction, from basic functions up to real-time modification of user movement.
• Figure 3: Basic functions offered by ExoKit: Moving a joint $j_i$ to an angle $\theta_i$ expressed as (a) absolute w.r.t. $j_i$'s calibrated zero-degree angle, or (b) relative to the joint's current angle; (c) locking joint $j_i$ in place, or (d) collecting real-time sensor data of selected joints.
• Figure 4: ExoKit provides functional abstractions for five relevant classes of augmentation strategies which enable to (a) replay a scripted motion on demand, (b) continuously transfer one user's motions onto another one, (c) augment a user's motion effort by amplifying or resisting her ongoing motions, (d) alter the user's motion style, or (e) guide the user towards or away from an area.
• Figure 5: ExoKit's software features three functions for motion guidance: (a) constraining a user's motion to an area centered around $\theta_i$ with range $\epsilon$, (b) guiding a user towards this area, (c) or guiding the user away from it.