String Walker

A locomotion interface that uses eight strings actuated by motor-pulley mechanisms mounted on a turntable. String Walker enables users to maintain their positions while walking in various directions in virtual environments.

Enhanced Life

Proprioceptive feedback for walking is not provided in most virtual environments. Research on locomotion interfaces is still in a preliminary state, but some virtual-environment applications, such as training or visual simulation, require good locomotion sensation. Over the next decade, effective locomotion devices will be developed for these applications.


To develop a string-based locomotion interface that enables users to maintain position while engaging in omni-directional walking. In order to achieve this goal, string tension must be generated effectively and consistently.


The major innovation of this work is a new actuation mechanism that cancels the displacement of the walker. It is the latest in a series of attempts to create a realistic, practical locomotion interface:
  • Treadmills. This is the easiest way to realize an infinite floor, but a treadmill can not support omni-directional walking.

  • A motion foot-pad can simulate omni-directional walking and uneven surfaces, but it is very difficult to use.

  • The CirculaFloor (SIGGRAPH 2004 Emerging Technologies), which was developed to overcome the drawbacks of treadmills and foot-pads, but it is so complicated that it does not support sufficient walking momentum.

  • Powered Shoes (SIGGRAPH 2006 Emerging Technologies), which employs roller skates that are actuated by motors and flexible shafts, supports omni-directional walking, but the walker can not perform a variety of gaits.

In the String Walker, four strings connected to each shoe are actuated by motor-pulley mechanisms. Each motor is equipped with a rotary encoder, and the motor-pulley mechanisms measure shoe position and orientation. When the shoes move, the strings pull them in the opposite direction and cancel the step. The position of the walker is fixed in the real world by this computer-controlled tension of the strings. The motor-pulley mechanisms are mounted on a motor-driven turntable that rotates with the direction of the walker, which enables omni-directional walking. The four strings can pull the shoes in any direction, so the walker can perform a variety of gaits, including side-walking or backward walking.


This is the first relatively simple locomotion interface that allows users to enjoy omni-directional walking while maintaining a consistent position in the real world.


Hiroo Iwata
University of Tsukuba
iwata (at)


Hiroaki Yano
Masaki Tomiyoshi
University of Tsukuba