Development of a Super-thin and Fast Omnidirectional Treadmill through a Novel Helical Transmission Mechanism

To effectively enhance the spatial sensation for an immersive user experience (UX) in virtual reality (VR), the locomotion interface (LI) is one of the most critical factors. To offer a room-scale LI suitable for use in typical office or home environments, it is imperative that the LI device enables a natural walking experience while occupying minimal space. To realize LI for all directions, an omnidirectional treadmill (ODT) can successfully achieve 2-dimensional holonomic motion (X and Y axes) and provide the most natural walking experience, such as walking on real ground. However, a problem arises due to the excessive system thickness caused by the torus structure of a large treadmill (X-axis) carrying several small treadmills (Y-axis), along with the installation of a complex power transmission mechanism inside the ODT. To reduce the thickness of its double-layer and complex structure, we propose an ODT with a novel transmission mechanism. The proposed ODT utilizes helical timing pulleys (HTPs) to generate Y-axis motion and helical gears (HGs) to synchronized-actuate the HTPs. As a result, the proposed ODT achieves a super-thin configuration and fast actuation performance. A pilot test of the proposed ODT was conducted to assess its maximum performance. The results indicate achievable speeds of 3.175 m/s and 4 m/s, along with an acceleration of 5 m/s<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> for both the X and Y axes, respectively.