Subtlety is not always the answer for haptic feedback

MIT has discovered haptic feedback can be too subtle in research into preventing people tripping over objects.

MIT haptic feedback shoes Jose-Luis OlivaresIn particular, the team was finding ways to help astronauts step over things in their bulky space suits – which have big boots and poor downward visibility.

The idea is to have sensors in the boot as well as vibration motors to relay back processed sense data in a way that non-expert users can understand.

Researcher Alison Gibson spaced six vibration motors around the feet of volunteers – one each at the heel, big toe, and instep, and three motors along the outer edge of the foot. Vibration intensity was continuously variable.

A computer programme asked subjects to indicate when they felt vibrations and at what locations on the foot under two sets of conditions – while they concentrated on their feet, and while they ran thought a distracting cognitive test. Over 500 vibration stimuli were presented all-told to each subject.

Haptic feedback findings are that:

  • When distracted, subjects had difficulty identifying steady increases in intensity.
  • Even when concentrating on their feet, they had difficulty identifying decreases in intensity.
  • Subjects had difficulty distinguishing between stimuli locations on the outer edge of the foot.

In 20 percent of cases, distributed across all study participants, they were unable to discern low-intensity stimuli to the middle location on the outer edge of the right foot.

This meant that linking obstacle distance and direction to vibration intensity and six positions was out of the question.

Instead, Gibson is developing a boot with vibrators at three locations: toe, heel, front outside.

Stimuli will jump from low to high intensity when the wearer is at risk of colliding with an obstacle.

High-intensity stimuli will also be pulsed to distinguish them from low-intensity.

“In principle, the motor at the side of the foot could help guide the user around obstacles, but the first trial of the boot will concentrate entirely on the problem of stepping over obstacles of different heights,” said MIT. “The researchers will also be evaluating the haptic signals in conjunction with, and separately from, visual signals, to determine the optimal method of conveying spatial information.”


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