August 30, 2012

Virtual Reality Lets Upper-Limb Amputees Practice Prosthetic Control

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Images of the advanced myoelectric prosthetic hand training game. In the top image, the user aims the virtual hand at the object with a wrist-worn “ArmTarget” until the hand and sphere are aligned (yellow circle); then the force is adjusted (green circle). In the bottom image, the user closes the virtual hand, ready to then move the grasped object to the target area. Images courtesy of Vienna University of Technology, Interactive Media Systems Group, Annette Mossel.

A team of engineers and researchers from Ottobock, Duderstadt, Germany, and the Interactive Media Systems Group, Institute of Software Technology and Interactive Systems, Vienna University of Technology (TU Vienna), Austria, have developed a virtual reality (VR) system, called the Prosthesis Trainer, to help individuals with upper-limb amputations learn how to use their prostheses. Development of the VR training application, the brainchild of Andrei Ninu, an engineer at Ottobock, and Hannes Kaufmann, PhD, associate professor at TU Vienna, started in spring 2011 by Ninu and Michael Bressler, a TU Vienna master’s student. The current prototype was presented August 22, at Unity – Unite 2012, Amsterdam, the Netherlands, by Annette Mossel, a research associate at TU Vienna.

Wearing a VR headset and sensors to track arm movements, users can practice controlling their myoelectric prosthesis without risking damage to themselves or their surroundings. The system uses the iotracker optical motion-capture system with electromyography (EMG) to generate input for grasping control of the virtual prosthesis, creating a realistic simulation. Data from the iotracker and EMG signals are then fed into ARTiFICe, a VR framework for mapping the real world onto virtual objects using the Unity3D game engine. The iotracker and ARTiFICe were developed at TU Vienna.

Mossel explained the intention behind the development of the system and how it is used: The team implemented two mini “serious games”—games designed for a primary purpose other than entertainment—to motivate the patient to practice myoelectric prosthetic control. The first game allows the beginner prosthesis user to practice grasping various shaped object, such as cubes and cylinders. The second game is more advanced; it involves grasping spherical objects with different virtual-hand orientations as well as learning how to adjust grasp force with the myosensors. If the applied grasp force is too strong for the selected sphere, the sphere explodes. The grasped spheres must then be moved into a box.

“We plan to implement a more complex serious game based on the underlying technology in the next months,” Mossel added.

A preliminary study using able-bodied individuals will test the system’s robustness and usability with people who do not have any specific technical background, Mossel said. This will be done in cooperation with the Vienna General Hospital and will be supervised by medical experts. The results will then be used to optimize the system so that it can be used in the future for upper-limb amputee patients. The project roadmap includes tests with amputee patients, but no date has been set.

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