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General haptics and localzied haptic sfor ROKR E8
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Haptics for Mobile Communication Devices
Steve Dai, Device Technology, Motorola
Steve Dai, Haptics Purdue October 21, 2008
Outline
Haptics Overview
Haptics for Mobile Devices
Localized Piezo Haptics
Haptics Characterization
Summary
Steve Dai, Haptics Purdue October 21, 2008
Haptics Overview
Definition: tactile feedback, more specifically active feedback
Dominant Types of Active Feedback
VibrotactileVibration sensed by nerves in the skin
KinestheticSensations associated with body position, movement, or weight sensed by the nerves
in muscles, tendons, or joints
current focus
Steve Dai, Haptics Purdue October 21, 2008
Haptics Overview
Sample applications
mice
gaming controllers
BMW I-drive
vibrating call alert
medical training
3D Design & Interaction
Braille displays
Steve Dai, Haptics Purdue October 21, 2008
Haptics Overview
Comparison with other senses
Neurons “Data” rate(bits/s)
Temporal Acuity
Touch ~106 102 5 ms
Hearing ~104-105 104 0.01 ms
Sight ~106 106-109 25 ms
Lynette Jones, MIT
Steve Dai, Haptics Purdue October 21, 2008
Haptics Overview
Frequency Dependence of Perception
Fletcher-Munson curves, 1933 Minimum audible=threshold
SOUND: 20~20,000 HzSIGHT: 540 THz
Verrillo-RT. Subjective Magnitude Functions for Vibrotaction. IEEE Transactions on Man-Machine Systems MMS-11(1): 19-24. (1970
TOUCH: 20~1000 Hz
Steve Dai, Haptics Purdue October 21, 2008
Haptics Overview
ReceptorsSOUNDLight TOUCH
Steve Dai, Haptics Purdue October 21, 2008
Haptics for Mobile Devices
Why haptics?
“Data” rate(bits/s)
Temporal Acuity
Human to device Input
Touch –fingertip
102 5 ms
Audio – voice 104 0.01 ms
Sight – eye 106-109 25 ms
Steve Dai, Haptics Purdue October 21, 2008
Haptics for Mobile Devices Value to users
FUNCTION SAMPLE USE CASES HAPTICS REQUIREMENTS
Notification Vibe alert Simple vibration or patterns
Confirma- tion
Key pressstatus change
Short click-like responseLow latencyLocalized preferred over global?
AmusementEntertain- ment
Base boostTouchscreen UI eventGaming
Rich variety of haptic contents Visual/audio synchronization“Essential but unnoticed”
haptics
Communi- cation
Sensorial communication
Standards and infrastructure“Hapton”
capable phones
Incr
easi
ng C
ompl
exity
Steve Dai, Haptics Purdue October 21, 2008
Haptics for Mobile Devices
Global vs. Localized hapticsGlobal: vibrates the entire device
(phone)
Localized: vibration is localized to an input surface (keypad, display)
ROKR E8 (2008)
Samsung F700 & SCH-W559(2007)
Samsung Anycall
2008Mot A1000(2004)
RAZR2(2007)
LG Voyager(2008)Mot
Krave(2008)
Steve Dai, Haptics Purdue October 21, 2008
Haptics for Mobile Devices
Actuation Technologies
USE CASE & IMPLEMENTATION
VIBE ALERT
ADVANCED HAPTICS
KEYPRESS
YES YES NO NO
Global Localized
NO
OK OK GOOD EXLTGOOD
LMTD LMTD LMTD EXLTOKINTEGRATIONCOMPLEXITY
NO NO LO MODLO
Rotary Linear Linear F Reactor Piezo
Steve Dai, Haptics Purdue October 21, 2008
POKR E8 Haptics The review
“This new type of haptics really works, and quite well. The effect is best described as "spooky". It works so well that if Motorola had told us it had real keys under the surface -
and wasn't a touch keypad at all -
we would have believed them and never doubted it…. ”
Eric Lin, Eric M. Zeman and Rich BromeJanuary 7, 2008 www.phonescoop.com
Steve Dai, Haptics Purdue October 21, 2008
Localized Piezo Haptics The challenge
“Morphing” keypad= Display?
Lack of keyclick feedback for key press
Sample photo placement
ROKR E8 ModeShiftTM
keypad
Steve Dai, Haptics Purdue October 21, 2008
Localized Piezo Haptics The solution
Direct bonding of piezo element on phone chassis behind keypad
Shrinkage/expansion of piezo under electrical field translates to “buckling” motion of keypad
haptics to fingertip
Proof-of-concept
Force sensing resistor
Steve Dai, Haptics Purdue October 21, 2008
Localized Piezo Haptics Why piezo?
Typical Popple Click (Press Only)
-15
-10
-5
0
5
10
15
0 10 20 30 40 50 60
Time (ms)
Acc
eler
atio
n (g
)
2.0 4.0
Time (ms)
Popple switch Optimized DC rotary motor
Piezo Actuator vs. Click
5
5
5
5
0 10 20 30 40 50 60Time (ms)
Popple Click
Piezo Actuator
Optimized linear motor
Linear Motor with Reverse Drive vs. Popple Click
-15
-10
-5
0
5
10
15
0 10 20 30 40 50 60Time (ms)
Acc
eler
atio
n (g
) - P
oppl
e Popple ClickLinear (Rev. Drive)
Immersion VibeTonz vs. Click
0 10 20 30 40 50
Time (ms)
Popple Click
VibeTonz
MARGINAL GOOD BEST
Piezoelectric actuator
Global
Localized
Steve Dai, Haptics Purdue October 21, 2008
Haptics Characterization What to measure for a keyclick?
Virtual tapping study (J Feine, Stanford Univ, Haptics2006)
–
Haptic simulations of tapping on a hard object feels most real when hand acceleration produced by virtual contact are matched to those of contact with real object
Key click profile–
Push and release acceleration pulses–
Each pulse: <5 ms, 40~100 g Accel_pp
Impact other than acceleration needs to be further studied
2.0 4.0
Time (ms)
Steve Dai, Haptics Purdue October 21, 2008
Haptics Characterization Passive vibrotactile
0
50
100
150
200
250
300
0 100 200 300 400 500
Frequency (Hz)
Disp
lace
men
t (μm
)
Max_dMin_d
0
2
4
6
8
10
12
0 100 200 300 400 500Frequency (Hz)
Acce
l_pp
(g)
Max_g
Min_g
Acceleration Comparizon
0.0
0.1
0.2
0.3
0.4
0.5
0.6
0 100 200 300 400
Frequency (Hz)
Acc
eler
atio
n (g
)
SSRCAverageMountcastle1972
Displacement Comparizon
0
2
4
6
8
10
0 100 200 300 400
Frequency (Hz)
Dsi
plac
emen
t (μ
m)
SSRCAverageMountcastle1972
Thre
shol
dC
omfo
rt ra
nge
Steve Dai, Haptics Purdue October 21, 2008
Haptics Characterization Click threshold and comfort level
Test setup
Subjects control test processesUp/down key to adjust voltage levelSpace bar to register the desired voltage level
6 data points for each wave setting, 3 runs starts from low and other 3 runs from high
Alternated test sequence on threshold and comfort level for counter balance
Total 12 test subjects
12 levels at 2 dB a step
Steve Dai, Haptics Purdue October 21, 2008
Haptics CharacterizationWaveforms and resultant acceleration profiles:
Step, sin300_1, sin300_2, sing150_1 and sing 150_2 generated in Audition
Audio signal (Vpp = 0 ~ 2 V) to 20x piezo amplifier for threshold (max Vpp ~ 40 V)100x Kepco voltage amplifier for comfort level (max Vpp ~ 200 V)Wave forms played at both press and release of FSR
step w ave
-50
0
50
100
150
200
250
-0.005 0 0.005 0.01 0.015 0.02
Time (s)
Volta
ge (v
)
step w ave p-p acceleratoin
-15
-10
-5
0
5
10
15
-0.005 0 0.005 0.01 0.015 0.02
Time (s)
Acc
eler
atio
n (g
)
Sin300_1 w ave
-50
0
50
100
150
200
250
-0.005 0 0.005 0.01 0.015 0.02
Time (s)
Volta
ge (v
)
sin300_1 w ave p-p acceleratoin
-15
-10
-5
0
5
10
15
-0.005 0 0.005 0.01 0.015 0.02
Time (s)
Acc
eler
atio
n (g
)Sin300_2 w ave
-50
0
50
100
150
200
250
-0.005 0 0.005 0.01 0.015 0.02
Time (s)
Volta
ge (v
)
sin300_2 w ave p-p acceleratoin
-15
-10
-5
0
5
10
15
-0.005 0 0.005 0.01 0.015 0.02
Time (s)
Acc
eler
atio
n (g
)
Sin150_1 w ave
-50
0
50
100
150
200
250
-0.005 0 0.005 0.01 0.015 0.02
Time (s)
Volta
ge (v
)
sin150_1 w ave p-p acceleratoin
-15
-10
-5
0
5
10
15
-0.005 0 0.005 0.01 0.015 0.02
Time (s)
Acc
eler
atio
n (g
)
Sin150_2 w ave
-50
0
50
100
150
200
250
-0.005 0 0.005 0.01 0.015 0.02
Time (s)
Volta
ge (v
)
sin150_2 w ave p-p acceleratoin
-15
-10
-5
0
5
10
15
-0.005 0 0.005 0.01 0.015 0.02
Time (s)
Acc
eler
atio
n (g
)
Steve Dai, Haptics Purdue October 21, 2008
Haptics Characterization Click threshold
Step waveAccel_pp ~ 2 g Single pulse?
Frequency effectAccel_pp ~ 0.39 g at 150_1 Hz, Accel_pp ~ 0.71 g at 300_1 Hz
Number of wave Accel_pp ~ decreases at double waves
Drive voltageVoltage lower in double waves driveVoltage lower as frequency goes up
Threshold Acceleration
0
1
2
3
Step Sin150_1 Sin150_2 Sin300_1 Sin300_2
Haptics
Thre
shol
d A
ccel
e_pp
(g)
95% CI High
95% CI Low
Mean
Vpp
0
5
10
15
20
Step Sin150_1 Sin150_2 Sin300_1 Sin300_2
Haptics
Thre
shol
d Vo
ltage
(V)
95% CI High
95% CI Low
Mean
Steve Dai, Haptics Purdue October 21, 2008
Haptics Characterization Click “Comfort”
Level
Similar acceleration and voltage profiles as threshold
Frequency effectAccel_pp ~ 3.2 g at 150_1 Hz, Accel_pp ~ 6.7 g at 300_1 Hz
Number of wave Accel_pp ~ decreases at double
waves
Drive voltageVoltage lower in double waves driveVoltage lower as frequency goes up
Comfort Acceleration Level
0
5
10
15
20
25
Step Sin150_1 Sin150_2 Sin300_1 Sin300_2Haptics
Com
fort
Acc
ele_
pp (g
) 95% CI High
95% CI Low
Mean
Comfort Voltage Level
0
50
100
150
Step Sin150_1 Sin150_2 Sin300_1 Sin300_2Haptics
Com
fort
Lev
el V
olta
ge (V
) 95% CI High
95% CI Low
Mean
Steve Dai, Haptics Purdue October 21, 2008
Haptics Characterization single, double waves and vibrotactile
Lower acceleration and displacement for multiple waves
1 wave
2 waves
…. Vibrotactile, 250 ms, 37~75 wavesPiezo Thunder Mini shaker
Threshold Accel_pp
(g)Sin150 0.39 0.25 0.03 0.03Sin300 0.71 0.51 N/A 0.12
Threshold displ* (μm)
Sin150 4.3 2.8 0.33 0.32Sin300 2.0 1.4 N/A 0.32
1 wave
2 waves
…. Vibrotactile, 250 ms, 37~75 wavesPiezo Thunder Mini shaker
Comfort level Accel_pp
(g)Sin150 3.21 2.04 0.12 ~0.9 0.92 ~ 5.37Sin300 6.71 4.48 N/A 3.2 ~ 10.3
Comfort level displ* (μm)
Sin150 35.4 22.5 4.6 ~ 34.5 10.2 ~ 60.4Sin300 18.5 12.4 N/A 8.8 ~ 28.5
Steve Dai, Haptics Purdue October 21, 2008
Haptics Characterization “Comfort”
vs threshold levels
For current interactive click feedback test, the comfort level is approximately 18~19 dB over threshold. The ratio is appx a constant, and is independent of the wave forms, frequency and number of pulses
Accel_Cmf/Accel_Thr In dB (=20*log(Cmf/Thr))Step 8.79 18.9Sin150_1 8.29 18.4Sin150_2 8.02 18.1Sin300_1 9.44 19.5Sin300_2 8.76 18.8
Steve Dai, Haptics Purdue October 21, 2008
Haptics Characterization Issues of existing in-line test fixture
200 g wt on linear sliderGood tool for production line with good R&R
Discrepancy of fixture vs handMagnitude of pk-pk accelerationTrend of frequency response
Fixture Hand
Frequency response
Steve Dai, Haptics Purdue October 21, 2008
Haptics Characterization Literature --
human finger study
Multiple joints, muscles/tendons to actuate fingerBiomimetic finger: use SMA for actuation* Vishalini
Bundhoo
and Edward J. Park, “Design of an Artificial Muscle Actuated Finger towards Biomimetic
Prosthetic
Hands”, IEEE, 2005
Steve Dai, Haptics Purdue October 21, 2008
Haptics Characterization Literature –
fingertip
Findings•
Mass m: ~ 6 g•
Stiffness k: up linearly with force•
Damping b: large zero-f value, up linearly with force
Rapid transient measurement
Model)()()( tkxtxbxmtF ++= &&&
* A. Haijun
and R. Howe, “Identification of the mechanical impedance at the human finger tip”, J Biomechanical Eng, Vol
119, P 109, Feb 1997
Steve Dai, Haptics Purdue October 21, 2008
Haptics Characterization Internal Study --
finger impedance vs frequency
Model
2-spring system?•
Both response to lower frequency•
One dominates at higher frequency* C Fu and M Oliver, “Direct Measurement of Index Finger Mechanical
Impedance at Low Force”, World Haptics 2005
02468
10121416
0 100 200 300 400 500 600Frequency, Hz
|Z|,
N-s
/m
Z(ω
) = F(ω
) x& (ω
) = (mω − k ω
)j + b
Two springs?
1 DOF?
Steve Dai, Haptics Purdue October 21, 2008
Haptics Characterization Improved test fixture –
proof of concept
Schematic•
2-spring system–
Arm–
probe•
1 DOF at the joint•
Weight and position to reach 150~200 g at the probe
“Primitive” fixture•
stainless steel = spring 1•
200 g weigh: F @ contact ~ g•
Accelerometer: MS ACH-01•
Poron: Rogers 4790-92-15125-04 cellular urethane foam, 3 mm, = spring 2
•
Probe: Al block + screw with round tip
wtPoron
A-meterProbe
Phone
Springs
1 DOF
Steve Dai, Haptics Purdue October 21, 2008
Haptics Characterization Results –
Finger Press vs Fixture
Fairly good tracking at 200, 250 and 300 Hz, nearly 1:1
Good tracking at all voltage levels
Slightly off at 150 Hz
Overall the tracking is very much improved over the existing inline test fixture
Steve Dai, Haptics Purdue October 21, 2008
Summary
Haptics is an essential functionality of mobile devices
Proper developed haptics could greatly enhance device usability
Piezoelectric enabled localized haptics can provide a nearly true keyclick experience
Haptics characterization is critical for technology development
Steve Dai, Haptics Purdue October 21, 2008
Challenges
Haptics characterization–
Understanding of the physical parameter space responsible for a wide range of tactile sensations that can be communicated from a mobile device to the human hand and/or the wrist
–
Provide psychophysical evidence for the design of tactile patterns to be used with mobile devices
Haptics implementation–
Touchscreen solutions–
Novel UI enabled or enhanced by haptics in conjunction with visual and audio effects
Steve Dai, Haptics Purdue October 21, 2008
Backup slides
Steve Dai, Haptics Purdue October 21, 2008
Haptics Characterization Voltage –
Acceleration Calibration
•
Observation–
Good linearity between Vpp to piezo and Accel_pp in all driving waveforms•
For sinusoidal wave, Accel ~ ω2*Displ ~ ω2*V –
Consistent slopes in both low and high voltage ranges–
Parameters from linear curve fitting are used to calculate the actual Accel_pp
Threshold Calibrationy = 0.216x - 0.033
R2 = 0.9996
0
2
4
6
8
10
0 10 20 30 40 50Voltage (v)
Acce
lera
tion
p-p
(g)
Step
sin150_1
Sin150_2
sin300_1
Sin300_2
Linear (Step)
Comfort Level Calibration
y = 0.212x - 0.7498R2 = 0.9986
0
10
20
30
40
50
0 50 100 150 200 250Voltage (v)
Acce
lera
tion
p-p
(g)
Step
sin150_1
Sin150_2
sin300_1
Sin300_2
Linear (Step)
Microelectronics & Physical Sciences Research
Multi-Function Transducer (MFT)
DIAPHRAGM
POLE PIECE
FRAME
MAGNET
TOP PLATE COIL PROTECTOR1
SUSPENSION
SUSPENSION
FOR SOUND
FOR VIBRATIONPROTECTOR2 SPACER
ACTUATORS
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