Levitas

An embodied interface that allows both physical and virtual displacement within an Immersive Virtual Environment (IVE) was proposed and implemented. It consists of a modular wearable used to control a mechanical motion base from which a user is suspended. The motion base is able to navigate in 3D through seven wires whose length is adjusted via a parallel link manipulator. Three sets of interactions were designed:

1. A multimodal interaction using brain and muscle activity, pressure and head movement to simulate swimming. If people relaxed, they started to float.
2. An embodied interaction using head movements to navigate, emulating the head anticipation phenomenon during locomotion.
3. A haptic-aided embodied interaction using head movements to navigate, and vibrations to predict the detected movement direction.

The results of several evaluations showed that:

1. It is difficult for people to relax while having a flying experience, therefore, behavioral markers are best for interaction.
2. Natural 2D locomotion embodied cues were successfully used to extend movement control to 3D space.
3. Head movement cues alone led to 100% completion rate in navigation tasks.
4. When compared to a Joystick, Levitas’ hedonic qualities and attractiveness are superior, even though the efficiency of target reach of the Joystick-based interaction is still higher.
5. With more practice, users might navigate with a performance comparable with the Joystick.
6. Haptic feedback to forecast machine detection of head movements did not provide significant improvements.

Our proposed interface uses two Inertial Measurement Units (IMU) integrated in a headband and a clip for the clothes. They are used to detect head and torso rotations which are intended to act as passive control inputs. Passive modalities are those that require no explicit input command. This design choice was made in an effort to create a perceptual interface based on body movements and states which people inherently perform.

We capitalized on the head anticipation phenomena during locomotion in 2D displacements where a rotation of the head anticipates the desired direction of movement. We expected to see it generalized in 3D navigation.

A bracelet providing haptic feedback with vibration was added to the Embodied Levitas to overcome the delay between the body command and the actual flying movement. Its purpose was to signal the users when the head movement command is recognized, so that they do not change positions while the motors are preparing the movement. The haptic feedback consists of a simple pulse of vibration lasting less than 500 ms.

Besides the aforementioned head movements mentioned, two new movements to navigate sideways were added. By reclining their heads on one shoulder or the other, users were able to move to sideways. Moreover, the wearable design and the harness were changed to improve mobility of the torso forwards and backwards.