-- KarlinBark - 9 July 2004

The question Mark has posed is, what's more effective when it comes to skin stretch intensity, applying different forces to stretch the skin, or stretching the skin at various displacements?

My initial thought was that skin displacement would be more effective, because from our initial "testing" of skin stretch, we used the servo motor to basically twist the skin...and obviously, as the servo motor rotated more, the pain of the skin stretching increased, and pinched the skin on my forearm. Obviously force and displacement are related, yet in Srinivasan?s experiment, because of the varying "spring" properties of the skin at the fingertip and skin at the forearm, the force necessary at the fingertip in the tangential direction, to match the intensity of the normal indentation was much greater. Even though the displacement in the tangential direction was still smaller than the displacement in the normal direction.

Li has come up with a reason to use force as a measurement (instead of displacement). He says that if you apply a force, which can sense the reaction force from your skin, you don?t have to worry about slip, because the actuator will keep twisting/stretching skin if it slips...but the nominal point will move...so a downside is that this method doesn?t have as much variety in how we can stretch someone?s skin (no directionality- just magnitude)

Keep in mind that people have already completed research that show that people can detect what direction their skin is being stretched...

Questions:

When multi-tasking (not concentrating solely on skin stretch) can people still distinguish what direction their skin is being stretched?

How can we prevent/minimize slip?

What information (what is intuitive) can we provide using skin stretch?

How many varying directions can we stretch skin?

What forces are reasonable to activate skin stretch and provide some sort of acknowledgement?

How does movement effect the directional perception of the user (i.e. if your arm is raised up and you feel your skin stretching towards your hand, does the user think of upward movement, and if your arm is down at your side, and your skin is stretched in the same direction, does the user think of downward movement?)

How much does having a visual/audio cue, in addition to the haptic cue help? For example, if you want to give a haptic command that tells someone to 'duck', does the person respond faster to someone yelling 'duck', someone pushing their shoulder, someone motioning to duck, or some combination of these possibilities?

How do we conduct a test? Is it worth doing so?

Does background noise affect haptic cues? (perhaps it helps- lack of clear auditory commands may make a person more sensitive to the senses they are able to use, such as touch and visual?)

What we need to do:

Figure out what range of motion we have for skin stretching, that people can perceive while completing different tasks.

Think of information that can be transferred using skin stretch (direction, alerts,