Design and analysis of open-source educational haptic devices
Keywords: Mechanical Engineering.

Open-source hardware significantly impacts the development of technology by allowing communities of users with varied expertise to share, customize, and collectively improve on designs. Most haptic hardware available outside of the research community is proprietary and expensive. This prevents communities of users from easily obtaining, building, modifying, and learning from the devices. We propose that the ability to easily obtain, assemble and customize a haptic device is especially important for educational applications. In this work we present three open-source haptic devices, for which we carefully considered trade-offs in cost, ease of fabrication and assembly, and performance -- toward making haptic devices more accessible for educational applications. We first present Hapkit 3.0: an open-source, customizable, 3D-printed, one-degree-of-freedom (1-DOF), kinesthetic haptic device developed for science, engineering and math learning. The design of Hapkit 3.0 built on the design of two previous versions of the device (Hapkit 1.0 and Hapkit 2.0). We performed an analysis of the mechanical components of the Hapkit family of devices as well as a stiffness discrimination study using the three versions of Hapkit. From the study we found that Hapkit 3.0 outperformed the previous two versions. We applied the Hapkit family of devices in several educational environments: a middle school classroom, an online class, and undergraduate and graduate courses. We also investigated the use of Hapkit to illustrate abstract mathematical concepts for high school students, and found evidence that haptic feedback could be used to visualize mathematical functions. We then present Haplink: an open-source, 3D-printed, kinesthetic haptic device that can be used as a 1- or 2-DOF device, and where the kinematics of the 2-DOF device build on the kinematics of the 1-DOF device. Haplink was designed with the idea that students benefit from learning concepts incrementally, and that a device that itself increments from one to two degrees of freedom will aid in this process. We analyze the resolution and force capabilities of Haplink throughout its workspace and the effects of the resolution and force capabilities in rendering different virtual environments. We also describe the use of Haplink in a university freshman course on haptics, where we demonstrated the use of Haplink to teach concepts incrementally. Finally we present HapCaps: an open-source, 3D-printed, tactile haptic device for finger sense training. HapCaps are haptic buttons designed to sense a press and give a tactile cue in the form of a vibration. We used 10 HapCaps to build a system (the HapCaps System) to combine finger sense training and math learning. Using the HapCaps System, we performed a four-week study in which first graders underwent finger sense training at the same time as they were learning math. The purpose of the study was to evaluate our device in a classroom environment as well as understand the logistics of using the HapCaps System hardware in a school setting. At the same time, we looked for any improvement in finger sense and math that would emerge from a short study. As a result of the study, we found evidence that the HapCaps System can be used to improve finger perception in first graders. We also improved the design based on the results of the study