10 17 2008 A Wireless Flexible Temperature And Tactile Sensing Array For Robot Applications

MEMS LaboratoryDepartment of Mechanical Engineering

ISPMM’2008, Aug. 25~29, 2008, Anhui, China National Taiwan University

A Wireless Flexible Temperature and Tactile Sensing Array for Robot Applications

Department of Mechanical Engineering, National Taiwan University, Taipei, Taiwan

Presenter: Dr. Yao-Joe Yang


National Taiwan UniversityISPMM’2008, Aug. 25~29, 2008, Anhui, China

The schematic of the proposed artificial skin

Temperature sensor

Pressuresensor

Flexible substrateSkin receptors

Inner Side of the skin

Outer Side of the skin

• Flexible substrate• Copper-PI (polyimide) film

skin receptor• The outer side of the skin

• Tactile sensor array• The inner side of the skin

• Temperature sensor array• The sensing elements

• Conductive polymer for tactile sensing

• Discrete sensor chips for temperature sensing.

Presenter

Presentation Notes

The schematic of artificial skin is shown in the figure. In this work, we present a low-cost artificial skin which is manufactured by implementing tactile sensing elements and the temperature sensing elements on a flexible substrate. The flexible substrate is copper-PI (polyimide) film. The artificial skin is just like a skin receptors. On the outer side of the substrate, we implemented tactile sensor array. On the inner side of the skin, we implemented temperature sensor array. For the sensing elements, conductive polymer is dispensed on interdigital electrode-pair for tactile sensing, On the other hand, discrete temperature sensor chips are used for temperature sensing.



PI-film

-20~80°C

50~500g

Specifications of the proposed artificial skin

Artificial Skin

Force range

> 4/cm2

< 3 mm Thickness

Sensor density

Temperature range

Flexible substrate

Specifications

Presenter

Presentation Notes

The Specifications of the propose artificial skin is follows as: The sensing range of applied force is 50-500g The temperature sensing range is during minus twenty to Eighty Celsius degree. The density of the sensing array is four sensors per centimeter square. The total thickness of artificial skin is smaller than 5mm. The material of flexible substrate is the copper-PI (polyimide) film.



The fabricated artificial skin

• In (a), the outer side of the artificial skin• Tactile sensor array

• In (b), the inner side of the artificial skin• Temperature sensor array

(a) The outer side of the skin8x8 tactile sensing array

(c) The flexibility of the artificial skin

Tactile sensor

Temperature sensor

Tactile sensor

Temperature sensor

Tactile s ens ing E lem ent

10m m

Tem peratu re sensing pad

Te m p er atu re s e ns o r 1 0 m m

(b) The inner side of the skin8x8 temperature sensing array

Presenter

Presentation Notes

The fabricated artificial skin is shown here. The dimension of 8x8 sensing array is 4 cm x 4 cm. In Fig. (a), the outer side of the artificial skin, the 8x8 tactile sensor array is shown. In Fig. (b), the inner side of the artificial skin, the 8x8 temperature sensor array is shown. Fig. (c) shows the flexibility of the fabricated artificial skin with temperature and tactile sensing elements.



Tactilesensing

40mm

Temperature sensing pad

40mm

Temperaturesensor



Temperature sensor

Tactile sensor





The heaters of different shapes

(a)

(c) (d)

(b)

• The different shapes of heaters• (a) Bar shape• (b) Circular shape• (c) Triangular shape• (d) Square shape

• The heaters • shaped using 1mm metal

wire

Presenter

Presentation Notes

We also made several heaters of different shapes which will be used to create the temperature patterns for testing the temperature sensing array. The heaters are made by thin metal wire with 1mm in diameter



Measured Temperature Patterns Induced by the Heaters of Different Shapes

80℃

11℃

Temperature Colorbar

Heat source

(a)

80℃

11℃


Heat source

(b)

80℃

11℃


Heat source

80℃

11℃


Heat source

(d)

(c)

Presenter

Presentation Notes

The viewgraph shows the measured temperature patterns created by the heaters of different shapes These red geometry shapes indicate the heat sources Obviously, the heaters of different heater shapes can be clearly resolved by the our temperature sensing array.



The Stamps of Different Shapes

4mm 4m

m(a)

(c) (d)

(b)

• The different shapes of acrylic stamps

• (a) T shape• (b) Circular shape• (c) Bar shape• (d) Triangular shape

• The applied pressure • T-shape

1kg weight• The other shapes

500g weight

Presenter

Presentation Notes

We also made acrylic stamps of different shapes for testing the tactile sensing array. We have T-shape, ……. For Fig. (a), the applied pressure is produced by placing a 1kg weight on the top of the T-shaped stamp. Similarly, a 500g weight is used for Figs. (b), (c) and (d).



Pressure distributions of different solid stamps

(c)

300 kPa

(d)

300 kPa

300 kPa

(a) (b) 300 kPa

0 kPa0 kPa

0 kPa 0 kPa

Applied pressure

Applied pressure

Applied pressure

Applied pressure

3 cm

3 cm 2 cm

3 cm

3 cm

Presenter

Presentation Notes

The slide shows the measured pressure distributions by using these acrylic stamps of different patterns The red dotted lines in this figures are the shapes of the stamps Again, the stamps with different shapes can be clearly resolved by the tactile sensing array



The interdigital electrode pairs and tactile sensing element

• Two different types of interdigital electrodes for the tactile sensing elements are fabricated.

• In (a), two different pre-defined inter-digital copper electrodes

• In (b), the sensing elements with dispensed conductive polymer

(a)

(b)

Conductive polymer

Conductive polymer

Presenter

Presentation Notes

this viewgraph shows two different types of fabricated interdigital electrodes for the tactile sensing elements. In Fig. (a), the major difference between these two electrode patterns is the numbers of finger pairs. In Fig. (b), the electrode pairs are dispensed with conductive polymer. The purpose of these two electrode-pair designs is to provide two different initial resistance of the sensing element. The sensing element with smaller number of finger pairs has higher initial resistance. These two designs provide two different dynamic ranges for the scanning read-out circuit. We have demonstrated that the devices of both electrode designs worked correctly.



Analog Temperature Sensor

Analog Temperature SensorMaxim (www.maxim-ic.com)

MAX6607

Sensitivity

Transfer fnc.

Supply voltage 1.8V~3.6V

Temp. range -20~80℃

Package SC70

Size 2.4 x 2.0 x 1.0 (mm)

( ) ( )( )CmV

mVVCT OUT

°−

=°/10

500

Cmv °/10

Presenter

Presentation Notes

Discrete temperature sensor chips (MAX6607) are employed as the temperature sensing elements. The sensitivity of chip is 10mv per Celsius degree. The temperature-to-voltage transfer function has an approximately linear positive slope. The supply voltage is from 1.8V to 3.6V. The temperature sensing range is during minus twenty to Eighty Celsius degree. The chip package is 5-pin SC70. The size of temperature chip MAX6607 is 2.4 by 2 by 1 (mm)



Temperature Scanning Circuit

Tactile Scanning Circuit RS-232 Switch Circuit

Technology

10 17 2008 A Wireless Flexible Temperature And Tactile Sensing Array For Robot Applications