Event Based Haptics

duewestseaurchinAI and Robotics

Nov 14, 2013 (3 years and 6 months ago)

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EventBased Haptics
Günter Niemeyer
Stanford Telerobotics Lab
http://telerobotics.stanford.edu
Adding HighFrequency Playback
to make virtual feel real
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Very Dynamic!
Tapping
Firm Grip
Soft Grip
up to
~ 1000 Hz
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Today’s Haptics = NERF World
Need HF!
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Classic Haptics: Control like Robot
Compute forces every servo cycle
(closed-loop feedback)
MotionForce
Ke
F =-Ke
xm
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Why not realistic?
Kcontrol
Fuser
mdevice
o
Frequency content from CL poles:
mass ↔ stiffness

= √ K/m
o
Typical K = 1000 N/m
m = 100 g = 0.1 kg

= √ 10,000 = 100 rad/sec
= 16 Hz
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High gain K = 4,000,000 N/m

Amplifiers ~ 10,000 Hz

Servo rate ~ 10,000 Hz

Encoders ~ 4,000,000 lines/rev
To make it “real”… YIKES!
o
Generate frequency content
1000 Hz >60ximprovement
Fcol
Genc
K =
Robot with Im and subms resolution…
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We

Position >1 mm

Move <10 Hz

React >100 ms
o
But

Sense force up to 1000 Hz!
o
Asymmetric!
Detect Event
Signatures
Would we want to?
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EventBased Haptics
Event
=
Impact, Transition
Open-loopplayback of
characteristic force profile
POW!
M
F =-K
e
xm
+ F
event
(t,vin)
=+
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Superimpose HF
over PD (LF)
o
Uncontrolled
< 50 … 100 ms
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Library of transients
for velocity and
material
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Momentum cancellation
EventBased Haptics (cont’d)
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User Testing
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12 objects (3 real, 9 virtual)
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16 subjects
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Acceleration Matching
=
Fwood
Fmotor
astylus
astylus
Fwood
≠Fmotor
astylus
= a
stylus
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Acceleration Matching
o
Invert model to match stylus accelerations
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Surface Feature = MicroTap
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Micro Steps...
Classic:
EventBased:
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Openloop HF playback →
More real, more information
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Surface features ≈ microtaps
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Parameterized libraries
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Easier computation
(lower servo rates)
EventBased is GOOD ☺
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Telerobotics Lab
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Students:
Jesse HwangMichael Williams
Katherine KuchenbeckerJonathan Fiene
Acknowledgements / Questions?
o
Funding:
NSF Career IIS0547672
Stanford OTL Award