Tactile Perception and Haptic Interaction Cecilia R Aragon

Tactile Perception and Haptic Interaction Cecilia R. Aragon IEOR 170 UC Berkeley Spring 2006 IEOR 170

Acknowledgments • Andrew Green, www. uwm. edu/~ag/teach_pdf/ lecturenotes/perception/12 Touch. ppt • Dean Chang, Immersion Corp. , www. immersion. com • Stephen Wall, http: //www. dcs. gla. ac. uk/~pdg/teaching/demms 4 /notes/Haptics. pdf Spring 2006 IEOR 170 2

The Sense of Touch • Everyday Tasks – Dialing a phone – Playing a guitar or piano – Finding a light switch – Feeling your pulse • Touch is complex: tying a shoelace • Only bi-directional communication channel – both input & output Spring 2006 IEOR 170 3

Why is Touch Important? • Touch-tone phone – Rich tactile cues – Can be done without looking – Effortless • PC calculator – No tactile cues – Only visual feedback – Painstaking Spring 2006 IEOR 170 [Chang] 4

Tactile Perception • Provides information about our environment – e. g. hot, cold, smooth, rough • Provides feedback – e. g. when trying to lift an object, press buttons, etc. • Examples • Difficulties if no feedback? Spring 2006 IEOR 170 5

The Physiology of Touch Mechanoreceptors Primary Sensory Cortex (peripheral) (cortical) • Work together to inform us about pressure, texture, stretch, motion, vibration Spring 2006 IEOR 170 [Chang] 6

Peripheral Pathways of Touch • • • Mechanoreceptors - pressure, texture, vibration Proprioceptors - body position Two pathways for pain (both of which are independent from other tactile or proprioceptive pathways) – – – Spring 2006 one fast pathway for sharp pain, one slow pathway for dull pain IEOR 170 [Green] 7

Four Receptor Types a) Merkel Disks -- constant sources of stimulation over a small area, such as if you were carrying a pebble b) Meissner Corpuscles -respond best to active touch involved in object exploration c) Ruffini Endings -- constant stimulation over a larger area - also detects skin stretch d) Pacinian Corpuscles -extremely sensitive over a large receptive field -- blow gently on the palm of your hand Spring 2006 IEOR 170 [Green] 8

Cross Section of the Skin Spring 2006 IEOR 170 [Green] 9

Receptive Field • Mechanoreceptors detect skin deformations • Tactile acuity is determined by how close the mechanoreceptors are to each other and by the size of the receptive field Spring 2006 IEOR 170 [Green] 10

Receptive Field Spring 2006 IEOR 170 [Green] 11

Receptive Field The two-point threshold for any part of the body is determined by the size of the receptive fields and the extent of overlap Spring 2006 IEOR 170 12

Sensation of Touch (Cortex) • Adjacent portions of skin surface tend to be represented by adjacent portions of cortex • Cortical magnification for lips, nose and fingers [Green] Spring 2006 IEOR 170 13

Cortical Pathways of Touch Spring 2006 IEOR 170 [Green] 14

Cortical Magnification • The receptive fields and cortical representations give more acuity to fingers, mouth, nose and tongue Spring 2006 IEOR 170 [Green] 15

Cortical Plasticity for Touch Spring 2006 IEOR 170 [Green] 16

Proprioception • All muscles have nerve fibers which detect the amount the muscle is stretched • All joints have fibers which detect the relative position of each bone • Together these allow you to determine the position of every part of your body. Spring 2006 IEOR 170 [Green] 17

Proprioception Includes The Vestibular Sense Ocular Motor Spring 2006 IEOR 170 [Green] 18

Haptics Spring 2006 IEOR 170 19

What is Haptics? • adj. Of or relating to the sense of touch; tactile. [Greek haptikos, from haptesthai, to grasp, touch. ] – Haptics involves both proprioceptive and tactile senses, in concert with other senses. • adj. The science of applying touch (tactile) sensation and control to interaction with computer applications. Spring 2006 IEOR 170 20

Haptic Interfaces • Fully duplex channel. You can both transmit and receive information simultaneously. • Requires very high refresh rates of approx. 1000 Hz for realistic feel. • Requires very high spatial resolution. • Touch is a complex modality consisting of several distinct sensory channels. [Wall] Spring 2006 IEOR 170 21

Tactile Technologies • Tactile information is produced by perturbing the skin – Pins or other mechanical vibrating elements - either alone or in an array, as in devices for Braille display • typically used for fingertip stimulation – Air jets blow to produce a disturbance – Cushions of air can be inflated or deflated to vary pressure on skin – Electrical stimulation - low levels of current provide a localized tingling sensation • Typically used in gloves, or for larger body areas Spring 2006 IEOR 170 [Wall] 22

Force-Feedback Technologies • Kinesthetic (relating to the feeling of motion) info is produced by exerting mechanical forces • Technologies are easier to produce than tactile • High-end devices • Algorithms force feedback - the KX model to produce barriers – force exerted = K * X – where X is the distance beyond the barrier, K a stiffness constant Spring 2006 IEOR 170 [Wall] 23

Interaction of Touch & Vision Spring 2006 IEOR 170 [Green] 24

The Haptic Technology Spectrum • Mass/Weight • Stiffness/Detents • Viscosity/Damping • Roughness/Texture • Pulses • Waveforms • Vibrations • Simultaneous Compound Effects Spring 2006 IEOR 170 [Chang] 25

Haptics in Medical Simulation • Simulators before Haptics – – Fruit Animals Cadavers No Touch • Trends Towards More Reliance on Touch – Laparoscopy – Endoscopy Spring 2006 IEOR 170 [Chang] 26

Haptics in Medicine • • Spring 2006 Photorealistic Graphics Life-like Sounds Simulated Touch & Emotion IEOR 170 [Chang] 27

Haptics in Laparoscopy Spring 2006 IEOR 170 [Chang] 28

Haptics in Design & Simulation Spring 2006 IEOR 170 [Chang] 29