These notes are going to be quite brief for the time being, relative to what we have learned, but will endevour to place more complete rendition here in the near future.

Click for enlarged versions:

ProtoTouchTest.jpgg

1, 2, 3

• Design prototypes force feedback.
• Sense touch pressure at each taxel (tactile pixel).
• Transmit touch to opposing taxel..
• Force may be conveyed rigidly or compliantly by opposing taxel.
• Opposing taxel extends significantly (by up to 7 cm or so).
• Touched taxel relaxes to an equilibrium position.
• A surprising range in the quality of response is possible, depending on:
  • Hardware configuration (air pressure, leak rate, spring stiffness)
  • Software settings (response shape, response time, relaxation time)
• Prototype system response time limited by:
  • Serial communication rate with Atmel micro.
  • Prototype protocol inefficiencies.
  • Actuator response rate, which depends on:
    • Air pressure in system
    • Drive characteristic relative to maximum
    • Leak rate
    • Muscle length
    • Weave dimensions
• Sound
  • A relatively high-frequency noise is produced
  • For fixed hardware, this depends on: air pressure, leak rate, valve state
  • Amount and quality of the noise which is produced depends heavily on the shape of the leaking valve, and on any materials which may be near to it.

• Second revision leaky muscle prototype design from Merlin Systems
• 25 cm muscles
• Single, proportional SMA valve
• Adjustable leak rate
• 3-5 bar pressure

• Mini control board with electronics (Merlin)
• 8-bit microprocessor (Atmel)
• Serial connection to PC (Keyspan USB serial adapter)
• ASCII command protocol over RS232.
• Responsive interaction design (Max/MSP)

• Pressure sensors : Interlink FSRs
• Additional voltage to current converting circuit (as recommended in FSR application notes)

• MDF (1 cm)
• Dowels (pine, 50 cm)
• Assorted hardware
• Benchtop regulated 30A power supply set at 5V

• 2 active taxels.
• 10 cm taxel spacing on a rectangular grid.
• 2 x 4 construction.
• 40 cm x 40 cm x 20 cm.

– Yon Visell - 22 Jul 2004