Coming to Grips with the Objects We Grasp

Detection object usage through wearable sensing

In this project we intend to look deeper in the combination of two relatively cheap technologies that enable identifying objects and interactions with these objects. The Object Interaction Bracelet is worn around the wrist, and contains inertial sensors, an RFID reader and its antenna. The RFID reader detects tags attached to objects that are taken in the user's hand, while the inertial sensors detect characteristic interactions with that object. Our aim is to take this technology away from the (current) early prototype stage and design such a bracelet that can be worn for longer periods without having to frequently ask the user to recharge their bracelets or change batteries. Current tests show that at least 2 full days of continuous logging (on a local micro-SD card) is possible from a light-weight battery. 

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Open source design. The project is committed to produce open-source (you can download the latest 'Porcupine" accelerometer PCB and schematics, as well as the antenna schematics and and antenna PCB) and reproducible designs. The files can be read and edited with EagleCAD software, which has a free reduced version available for download from their website.

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Combining spotted objects and gestures. For many tasks, combining the knowledge of what objects were grasped with what gestures were made with them can improve recognition of said tasks considerably. The plot below shows several activities in the garden, with in the top plot the spotted object ID's and in the bottom plot the acceleration traces. 

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Hardware

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The hardware consists out of 4 modules and a light-weight battery (see image to the left for all components attached to each other):

  • Porcupine board, with 3D accelerometer and micro-SD card
  • SkyeTek M1 mini RFID reader module
  • Oval antenna & matching circuit PCB, enhancing RFID range
  • ConnectBlue OEMSPA311 module for wireless transmission

For batteries, we tend to use either the KliC-7002 (600mAh) or the VARTA LPP402025 (150mAh) Li-Ion rechargeable batteries, connected to the recharging circuit of the Porcupine module. The weight of the whole setup, including straps, is currently around 32 grams. The component cost for everything together is around 320 euros, not including the time and effort to solder everything.

After altering the antenna's shape or size, one has to modify the component values of the matching circuit. Since this procedure is critical to the performance of the reading range and robustness of the RFID detection, we have dedicated a separate page to these steps. Alternatively, one can read a more compact version in this paper (published at TEI 2010).

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Gardening activities

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Long-term data set

Publication:

  • Eugen Berlin, Jun Liu, Kristof Van Laerhoven and Bernt Schiele, "Coming to Grips with the Objects We Grasp: Detecting Interactions with Efficient Wrist-Worn Sensors", International Conference on Tangible and Embedded Interaction (TEI 2010), Cambridge MA, USA, ACM Press, pp. 57-64, 01/2010. XMLBibTexPaper (pdf)Google Scholar.
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