Development of a Haptic Device

Using a 2-DOF Linear Oscillatory

Actuator

Osaka University, JAPAN

Masayuki Kato* Yoshinori Kono

Katsuhiro Hirata Takamichi Yoshimoto

7th May 2014

• Introduction(background, prior research)

• Purpose

• Basic Structure and Operating Principle

• Proposed New Target Waveform

• Analysis and Experiment

• Subject Experiment

• Summary

2

Outline

Background

What is Haptics?

Tactile feedback technology that artificially reproduces

the feeling of being pushed or pulled.

Grounded Haptic Device

Eyes-free

Navigation

Computer

Game

3

Prior Research and Device

4

Human perception model

Acceleration WaveformSlider Crank model

➢The mover is driven under this asymmetric

acceleration waveform.

Prior Research and Device

5

Symmetric accelerationFeel both forces

Asymmetric accelerationFeel only right force

Human perception is not linear.Only large acceleration can be perceived.

Prior Research and Device

6

Acceleration WaveformSlider Crank model

Disadvantage

1: Large size

2: One degree-of-freedom

7

Reproduction

-8.0

-6.0

-4.0

-2.0

0.0

2.0

4.0

6.0

8.0

0.05 0.10 0.15 0.20 0.25Vo

ltag

e[V

], A

ccel

erat

ion[

m/s

2]

time(s)

x-volt x-accel y-volt y-accel

Our actuator can reproduce the acceleration

waveform of the slider crank model.

Target waveform

8

Purpose

Improvement of the proposed Haptic Device

Approach

•Propose a more suitable acceleration

waveform

•Conduct subject experiment to verify

its performance

• Introduction(background, prior research)

• Purpose

• Basic Structure and Operating Principle

• Proposed New Target Waveform

• Analysis and Experiment

• Subject Experiment

• Summary

9

Outline

Structure of 2-DOF Oscillatory Actuator

x

yz

Magnet

NbFeB=1.42T

Magnetization

Stator yoke (SUY)

Y-coil

X-coil

Stator

Mover

Spring

10

Cross section X-Y

Mover yoke (SUY)

x

yz

Structure of 2-DOF Oscillatory Actuator

Cross section X-Y

Stator yoke (SUY)

Y-coil

X-coil

Stator

11

Structure of 2-DOF Oscillatory Actuator

x

yz

Magnetization

Stator yoke (SUY)

Y-coil

X-coil

Stator

Spring

Cross section X-Y

Magnet

NbFeB=1.42T

MoverMover yoke (SUY)

12

Force

Z

Y

X X-drive Y-drive

N

N S

S

Force

N N

S S

S

N

13

Operating Principle

• Introduction(background, prior research)

• Purpose

• Basic Structure and Operating Principle

• Proposed New Target Waveform

• Analysis and Experiment

• Subject Experiment

• Summary

14

Outline

Change of the Target Waveform

Slider Crank Model

• This waveform is dependent on the mechanical

structure of the slider crank.

• So it is actually not necessary to use it for our

actuator.

Acceleration Waveform

15

Proposed Target Waveform

Propose square wave

as a new target waveform

Slider Crank Model

Square wave with a high duty cycle

16

t[s]n m+n

a

-b

T

High Acceleration

Low Acceleration

0

a(t)

• Peak values

• Ratio of peak values

• Time period

Arbitrary acceleration can be generated

≒

Advantage

Proposed Target Waveform

( ) 00

= dttaT

( ) ( )=

=

N

k

tT

kdk

kTta

1

cossin12

Square wave is expressed by using Fourier series:

Constraint :

T : time period

d : duty cycle

N : harmonic order

17

t[s]n m+n

a

-b

T

High Acceleration

Low Acceleration

0

a(t)

Power Consumption of Each Order

( ) ( )=

=

N

k

tT

kdk

kTta

1

cossin12

T : time period

d : duty cycle

N : harmonic order

18

The power consumption of each harmonic order

component is calculated.

00.5

11.5

22.5

33.5

4

1 2 3 4 5 6 7 8 9 10 11

Pow

er[W

]

Harmonic order

Obviously, the first order component consumes almost all the power.

Modify the Target Waveform

( ) ( )=

=

N

k

tT

kdk

kkTta

2

cossin12

0.00 0.05 0.10 0.15 0.20

accele

rati

on

(m/s

2)

0.0

19

modified target waveform

➢ The first order component is removed.

➢ 𝑘 is added to the denominator to avoid

resonance. (𝑓0 = 120Hz)

t[s]n m+n

a

-b

T

High Acceleration

Low Acceleration

0

a(t)

20

FEM model

Analysis Condition

Ｚ Drive pattern

1.X-axis only

2.Biaxial (45 degree drive)

Analysis Condition

Magnets Magnetization of magnets [T] 1.4

Coil 1 (X axis) Resistance [W] 5

Coil 2 (Y axis) Resistance [W] 5.4

Coil 1 Maximum Voltage [V] 7.8

Coil 2 Maximum Voltage [V] 8.5

Number of turns [turn] 193

X axis Mass of mover [g] 64.5

Y axis Spring constant [N/mm] 74.9

Coils

21

Analysis Results [X-axis]

The actuator moves only in the x-axis.

The acceleration waveform is asymmetric.

Target waveform

0.00 0.05 0.10 0.15 0.20

accele

rati

on

(m/s

2)

0.0High Acceleration

-8.0

-6.0

-4.0

-2.0

0.0

2.0

4.0

6.0

8.0

0.00 0.05 0.10 0.15 0.20 0.25

Vo

ltag

e[V

], A

ccel

erat

ion

[m/s

2]

time[s]

x-volt x-accel y-volt y-accel

Time period 100ms

Duty cycle 90%

Harmonic order 14

22

Analysis Results [Biaxial]

Both axes acceleration waveforms are asymmetric.

There is no interference.

-8.0

-6.0

-4.0

-2.0

0.0

2.0

4.0

6.0

8.0

10.0

0.05 0.10 0.15 0.20 0.25

Vo

ltag

e[V

], A

ccel

erat

ion

[m/s

2]

time[s]

X-volt Y-volt X-accel Y-accel Target waveform

0.00 0.05 0.10 0.15 0.20

accele

rati

on

(m/s

2)

0.0

Time period 100ms

Duty cycle 90%

Harmonic order 14

23

Experiment Condition

Equipment Setup

Acceleration waveform is calculated by

displacement.

Laser displacement sensor

Experimental Condition

Magnets Magnetization of magnets [T] 1.4

Coil 1 (X axis) Resistance [W] 5

Coil 2 (Y axis) Resistance [W] 5.4

Coil 1 Maximum Voltage [V] 7.8

Coil 2 Maximum Voltage [V] 8.5

Number of turns [turn] 193

X axis Mass of mover [g] 64.5

Y axis Spring constant [N/mm] 74.9

Coils

X-Axis Drive Y-Axis Drive

Biaxial-Drive [45degree]

Experiment Video

24

Z

Y

X

25

Experimental Results [X-axis]

The actuator moves only in the x-axis.

The acceleration waveform is asymmetric.

-8.0

-6.0

-4.0

-2.0

0.0

2.0

4.0

6.0

8.0

0.00 0.05 0.10 0.15 0.20

Vo

ltag

e[V

], A

ccel

erat

ion

[m/s

2]

time[s]

x-volt x-accel y-volt y-accel

26

Experimental Results [Biaxial]

Both axes acceleration waveforms are asymmetric.

There is no interference.

-8.0

-6.0

-4.0

-2.0

0.0

2.0

4.0

6.0

8.0

10.0

0.05 0.10 0.15 0.20 0.25

Vo

ltag

e[V

], A

ccel

erat

ion

[m/s

2]

time[s]

x-volt y-volt x-accel y-accel

27

Comparison [Analysis and Experiment]

-8.0

-6.0

-4.0

-2.0

0.0

2.0

4.0

6.0

8.0

10.0

0.05 0.10 0.15 0.20 0.25

Vo

ltag

e[V

], A

ccel

erat

ion

[m/s

2]

time[s]

x-volt y-volt x-accel y-accel

Analysis Experiment

Experimental results agree with

analysis results.

-8.0

-6.0

-4.0

-2.0

0.0

2.0

4.0

6.0

8.0

10.0

0.05 0.10 0.15 0.20 0.25

Vo

ltag

e[V

], A

ccel

erat

ion

[m/s

2]

time[s]

x-volt y-volt X-accel Y-accel

28

Comparison [Acceleration property]Proposed square wave

x-axis y-axis x-axis y-axis x-axis y-axis x-axis y-axis

Positive peak aP[m/s2] 3.3 3.1 2.1 2.2 2.4 2.6 2.5 2.6

Negative peak aN[m/s2] 7.9 8.2 7.6 8.1 7.2 7.2 7.2 7.2

Ratio aN/aP 2.4 2.6 3.6 3.7 3.0 2.8 2.9 2.8

Acceleration of slider

crank model

Acceleration of proposed

square wave

Analysis Experiment Analysis ExperimentThe acceleration properties are

similar.

Slider crank model

-10.0

-8.0

-6.0

-4.0

-2.0

0.0

2.0

4.0

0.05 0.10 0.15 0.20 0.25

Acc

eler

atio

n [

m/s

2]

time [s]

X-axis Y-axis

-10.0

-8.0

-6.0

-4.0

-2.0

0.0

2.0

4.0

0.05 0.10 0.15 0.20 0.25

Acc

eler

atio

n[m

/s2]

time[s]

X-axis Y-axis

29

Comparison [Power Consumption]

The proposed waveform achieves lower power

consumption.

Proposed square waveSlider crank model

Decreased by roughly 40%

x-axis biaxial x-axis biaxial x-axis biaxial x-axis biaxial

Power[W] 3.2 6.4 3.3 6.5 2 4.2 2 4.1

Acceleration of slider crank model Acceleration of proposed square wave

Analysis Experiment Analysis Experiment

-8.0

-6.0

-4.0

-2.0

0.0

2.0

4.0

6.0

8.0

10.0

0.05 0.10 0.15 0.20 0.25

Vo

ltag

e[V

]

time [s]

Y-axis X-axis

-8.0

-6.0

-4.0

-2.0

0.0

2.0

4.0

6.0

8.0

10.0

0.05 0.10 0.15 0.20 0.25Vo

ltag

e[V

]

time[s]

Y-axis X-axis

• Introduction(background, prior research)

• Purpose

• Basic Structure and Operating Principle

• Proposed New Target Waveform

• Analysis and Experiment

• Subject Experiment

• Summary

30

Outline

31

Human Subject Experiment

Number of

subjects

10

Correct answer

feedback

None

Number of tests 25 times each

hand

Output direction 4

Operating time 3sec

Interval 3~6sec

Experiment condition

• Blindfolded• Headphones

32

Experimental Result[subject]

Average 69% correct.

In the experiment, probability for random correct answer is 25%.

→It is good result

Percentage of Correct Answer

0

10

20

30

40

50

60

70

80

90

100C

orr

ect an

swer

[%

]

Human subjects

A

B

C

D

E

F

G

H

I

J

33

Summary

➢Proposed a new general square acceleration

waveform

➢Modified the waveform to realize lower power

consumption (40% reduction).

➢In subject experiment, the percentage of correct

answer is 69%.