Haptic Interfaces for Virtual Reality and
Teleoperation
Haptics
‘The sensibility of the world adjacent to the body by use of
the body’
(Gibson, 1966)
Terminology
Proprioceptive Relating to sensory information about the state of the body (including cutaneous,kinesthetic and vestibular sensations).
Vestibular Pertaining to the perception of head position, acceleration and deceleration.Kinesthetic The feeling of motion. Relating to sensations originating in muscles, tendons and
joints.Cutaneous Pertaining to the skin itself as a sense organ. Includes sensations of pressure,
temperature and pain.Force Feedback The mechanical production of information sensed by the human kinesthetic
system.
Kinesthetic Feedback
• Golgi tendon organs (force)
• Muscle Spindles (position and velocity)
• Experimental data ambiguous
• Bandwidth estimates 20-30 Hz. (Brooks, 1990)
The Cutaneous Sense
Receptor Type Field
Diameter(mm)
Frequency at which
most easily
excited(Hz)
Amplitude
Threshold (m)
Probable Sensed
Correlate
RAI 3-4 8-64 30 Tickle, Vibration,
Tap
SAI 3-4 2-32 15 Pressure
RAII >20 >64 1 Vibration, Tickle
SAII >10 <8 60 Stretch, Tension
Haptic Interfaces
• Constrained Motion Devices
• Tactile Displays
Constrained Motion Devices
• Force Feedback
• DOF constrained to portray contract.
•‘Virtual free space’
• ‘Virtual constraint’
Device Limitations
• Sampling Period
• Device Dynamics
• Power Limitations
Ideal Equivalent Performance
|Z|, dBVirtual Constraint
Virtual Free Space
Max Impedance for Free Space
Min. Impedance For Hard Contact
FORBIDDEN REGION
Freq.
Low Inherent Impedance
• Nominally displays Virtual free space.
• Position feedback increases impedance.
• High gain servos constrain motion.
• Limitations:
• Stability & power
The PHANToM
High Inherent Impedance
• Nominally displays Virtual Constraint.
• Impedance reduced by force feedback.
• Framework conveys stiffness.
• Limitations:
• Dynamics & Stability
The HapticMASTER
TextureShape
High FrequencyLow Frequency
Region of Ambiguity
Bandwidth & The Haptic Spectrum
Temporal & Spatial Relationships
t = s v
• t = Temporal frequency (Hz.)• s = Spatial Frequency (Cycles/m.)• v = Exploration velocity (m/s).
Vibrotactile Display
Bonded Neodymium Magnets, Radially Polarised Magnetic Field
LVDT
Spring
Retaining Plate
200 Turns of 0.6mm Diameter Copper Wire
37mm
20mm
110mm
15mm
Multi Modal Interaction
• HCI Occurs Using:
• Haptic
• Visual
• Auditory
• Smell ?!?
• Overcome limitations using other modes.