SpiderClip: Towards an Open Source System for wearable Device Simulation in Virtual Reality


Autoren: Dirk Queck, Phillip Zimmer, Nicole Burkard, Iannis Albert, Georg Volkmar, Bastian Dänekas, Rainer Malaka, Marc Herrlich
ACKNOWLEDGMENTS: This work was partially supported by the German Research Foundation (DFG) within the priority program “Scalable Interaction Paradigms for Pervasive Computing Environments” (SPP2199), by the Klaus Tschira Foundation within the graduate school “Empowering Digital Media” at the University of Bremen, and by the Research Initiative of Rhineland-Palatinate within the priority area “AI Enhanced Cognition and Learning” and the graduate program “Cognitive Dynamics” both at TU Kaiserslautern.

What is SpiderClip?


Smartwatches and fitness trackers integrate different sensors from inertial measurement units to heart rate sensors in a very compact and affordable form factor. This makes them interesting and relevant research tools. One potential application domain is virtual reality, e.g., for health related applications such as exergames or simulation approaches. However, commercial devices complicate and limit the collection of raw and real-time data, suffer from privacy issues and are not tailored to using them with VR tracking systems. We address these issues with an open source design to facilitate the construction of VR-enabled wearables for conducting scientific experiments.

0. What you need?

This section covers all the materials to assemble the SpiderClip Prototype. You will need various hardwarecomponents, a 3D printer, glue or screws and various software components.
Hardware
Components:
Arduino Nano 33 IOT 2x
3.7 polymer Lithium Flat Battery
Sparkfun Bio Sensor Hub with Pulse Oximeter and Heart Rate Sensor
3D Printing:
Vive Tracker 1.0 and Vive Tracker 2.0:
Cap
Mainboard
Top
Drawing of Clip
Vive Tracker 3.0:
Top
Clip 1
Clip 2
VR-Setup(HTC Vive)
HTC Vive hardwarecomponents
2 Basestations
HTC Vive Tracker V2 or V3
Vive Tracker hand strap
Software
For Arduino:
Before the code runs some libraries have to be downloaded
<Adafruit_MPU650.h>
<Adafruit_Sensor.h>
<SparkFun_Bio_Sensor_Hub_Library.h>
<Wire.h>
Then you can download the Code from GitHub
Download the code here!
Sparkfun Pulse Oximeter and Heart Rate Sensor
For Unity:
You'll need to download the SteamVR Asset before you can use the virtual watch:
Download it here!
Unity VR-Watch: You need to download the SDK, so you can use the VR-Wearable:
You can use this link to do so.

1. Wiring Hardware Components

Arduino Nano 33 IoT (3.7V) is connected to a Sparkfun Bio Sensor via I2C (SCL, SDA). Both share a common 3.7V power source. The Arduino Nano 33 IoT acts as a master and controls the Bio Sensor while receiving data.

The Arduino Nano Every Board can be powered by a Micro-USB connector to the computer, a power supply or a 3.7 Lithium battery.
The communication with the microcontroller for the heart rate sensors is done via the standardized I2C interface.

2. SpiderClip-Sensor Source Code

In this chapter the source code for de Arduino is explained. The download link to the source code can be found here:
Download it here!
First you have to download some libraries to make the source code work.
These libraries are:
  1. <ArduinoBLE.h>
  2. <Arduino_LSM6DS3>
  3. <SparkFun_Bio_Sensor_Hub_Library.h>
  4. Wire.h (should be already installed)
You can also take a look at the code here:


3. 3D-Construction SpiderClip

The concept of SpiderClip is that the assembled components can be attached to the Vive tracker and thus merge with it hardware-wise into a unified device. This case consists of three parts and offers space for all selected hardware components. The 3 components have to be printed individually with a common 3D printer. To attach them to each other you can either use glue or you can screw the parts together.
Top row: Prototype, with HTC Vive Tracking System 1.0 support. Top left: Prototype, IMU and Bluetooth as separate system components. The system can be attached to the tracker with a clip mechanism. Top right: Exploded view of the prototype. Bottom row: Plug-and-screw system: Support for HTC Vive Tracking System 2.0 and 3.0 assembly with integrated battery (yellow) and cut-out for tracking support. Bottom right: Exploded view, individual housing components and battery integration.

At this point it is important to mention that the components should not be assembled yet. The „marriage“ of the hardware components and the 3D printed parts will be explained in the next chapter.

4. Fusion 3D-Printed Assebliies and Hardware Components

First, the Arduino Nano Every, the breadboard and the MPU6050 IMU must be glued to the bracket board using glue and a hot glue gun.

Next, the „top“ element can be attached to the bracket board (See exploded view).

After that, the HC-05 module can be plugged into the recess of the „Top“ element.

Finally, the „Protective Cover“ element is glued onto the „Top“ element

5. SetUp SpiderClip and Unity Implementation

After loading the source code on the Arduino board and assembling all hardware components, the Spider Clip can be attached to the Vive Tracker.
With this step, the preparation of the SpiderClip hardware components is finished and we can now download the virtual wearable.

The download link to the wearable can be found here:
https://github.com/D-Queck/VR_Wearable_SpiderClip
In the next section, I‘ll show you how the Unity Asset works for the wearable.

6. Unity MR-Wearable Asset

This section explains the virtual wearable for Unity. Figure xy shows the wearable in a virtual training environment. The wearable is based on the SteamVR PlugIn, which is required for functionality. However, the wearable can be implemented in any Set Up.
An important part of the plug-in is the Serial- Com script which uses the NuGet package Sys- tem.IO which provides communication over the serial port of the PC. The script handles all input parameters coming from the wearable and is the basis for the parameters displayed from the Dsahboard.
The wearable is attached to the Player Prefab of the SteamVR plugin and localizes itself via the HTC Vive Tracker. It includes a TimeMana- ger that displays the time and all WatchVR Ga- meObject + Dashboard.