Treadmills in Action

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Omnidirectional Treadmill

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New Paths through the Virtual World

 
Cybernetics experts are using the world’s first omnidirectional platform to study how the brains of walkers combine hearing, seeing and feeling.
   

Treadmills & more

Treadmills are an important tool to study the complex interaction between action and perception during walking. Within the EU-funded CyberWalk research project, we have set up two different treadmills.

Omnidirectional Treadmill

Walking is the most natural way for humans to navigate through their environment. Until recently it was almost impossible to physically walk through Virtual Environments in an unconstrained way. In the EU project "CyberWalk" an omnidirectional treadmill was developed, which together with real-time tracking, optimized control and several perceptual tricks enables humans to walk through Virtual Worlds in an natural and unconstrained fashion.
 
The CyberWalk treadmill is an ideal tool to study the interaction between perception and locomotion. Research topics include, but are not limited to: walking behavior, speed perception during walking, statistics of natural walking behavior, multisensory integration, and human navigation. The user wears a Head Mouted Display /HMD) which shows the Virutal Environment., Both the head and the body of the user are tracked. The head position and orientation are used to update the view of the Virtual Environment in the HMD, so that is corresponds to the way the user moves the head. The body position is used to control the treadmill, keeping the user close to the centre of the treadmill. Changes in treadmill speed and direction are kept below levels that would interfere with normal walking.
 
Together with CyberWalk partners from the Technical University in Munich, from the University La Sapienza of Rome and from the Swiss Federal Institute of Technology in Zürich, we have developed a revolutionary omnidirectional treadmill. It is the first omnidirectional treadmill in the world that allows for near-natural walking through arbitrarily large virtual environments and that can be used for basic research. The basic mechanism consists of 25 belts (0.5m wide) that are mounted on two big chains. The chains constitute one motion direction (1.4 m/s), while the belts run in the orthogonal direction (1.4 m/s). Together, they can generate motion in any direction. The chains move 7 tons, driven by 4 large 10 kW frequency-coupled engines. The treadmill measures 6.5 x 6.5 x 1.45m (LxWxH), with an active walking surface of 4.0 x 4.0m. Position of the person on the treadmill is measured with a Vicon tracking system and used to adjust the treadmill velocity as a function of walking speed. Together with a head-mounted display or panoramic projection screen (planned), the treadmill system allows users to walk through large virtual environments in a natural way.

CyberCarpet

The ball bearing CyberCarpet was the first prototype of an omnidirectional treadmill developed within the CyberWalk research project. It is based on a ball array design and combines the different components envisioned in the CyberWalk project: markerless position tracking, optimal control and omnidirectional capabilities. Upscaling to the desired size for real walking (at least 4x4 m) turned out to be difficult, however. Currently, this prototype is still used for demonstrations and as a testbed for different controllers and image-based tracking algorithms. The CyberCarpet device consists of a conveyor belt, mounted on top of a turntable. This turntable is actuated by a servo motor via a toothed belt. Thus, the platform has two degrees of freedom, namely a linear and a rotational one. Rotations and linear movements are transferred to the  user by means of an array of balls. These balls are mounted within the top surface and are passively driven by the conveyor belt. The system was tested with a model car, representing a person walking on the platform. GPS data from real walking was used to define movement trajectories.  Position of the car was estimated by markerless tracking and benchmarked against triangulation by means of strings.

Large Linear Treadmill

The linear treadmill setup consists of three main components: the treadmill itself, a four camera Vicon optical tracking system, and a visualization system that displays 3D graphics in a headmounted display. All three components are controlled by separate dedicated computers. The linear treadmill measures 6 x 2.4 m (L x W) and is capable of speeds up to 40 km/h. It is controlled from a PC via a CANbus connection. The treadmill can be controlled in either open loop or closed loop mode. For the closed loop control, the position of the user on the treadmill is measured with the Vicon system, which trackes infraredreflecting markers on the helmet worn by the user. Based on the position of the helmet and its change over time the speed of the treadmill is adjusted in order to keep the user on the treadmill. The Vicon data are also used to update the visual input, matching the head movements made by the user.

Robotic Wheelchair

The Robotic wheelchair (BlueBotics, Lausanne, Switzerland) can be used to transport people who weigh up to 150kg. The wheelchair can rotate about the center of the person?s head and can translate at a speed up to 5 km/h. In addition, the wheelchair has a built-in laser scanner that can help to determine the location of the wheelchair within a predefined space. The robotic wheelchair was modified with an ergonomic seat (Recaro, Kirchheim unter Teck, Germany) and can be used either autonomously with ANT® navigation or manually driven with a standard wheelchair joystick. Experimenters can therefore have wireless control over the behavior of the wheelchair, while in all cases participants have access to an emergency stop button near their left hand.

Last updated: Wednesday, 08.05.2013