Lab Presentation

12/10/2010

Safer Human Robot Interaction through Compliance in Design

• Compliance via pneumatic actuators– Inertia reduction– Inertia decoupling

• Compliance via soft covering– Peak force reduction– Capacitative sensing skin

• Research Goal– Investigate these effects on impact forces ->injury

Robot arm

Target

System Equations of Motionint 2 1 2 2 2 2

2

int 1 int 2 1

0 2 ( ) ( )

0 2( ) 2 ( )4

head

link linkp m link

k l m l

l mk k k k I

Variable Definition

kint Interface stiffness

km Muscle stiffness f(pressure)

kp Controller stiffness

Ɵ1 Arm angle

Ɵ2 Head mass angle

L2 Pendulum length

Mhead Target mass

Llink Length of arm link

Marm Arm mass

Effect of Stiffness Source

Stiffness source Low Freq Medium Freq High FreqMotor

PAMS

Springs (expected)

6 Hz 30 Hz

Test Conclusions•Mini does not increase peak forces significantly while vastly improving performance•Pressure has little effect on peak forces

Limitations

• Fragile• One of kind• Limited travel • Limited end tip velocity (0.5 m/s)

Goals

• Does joint stiffness effect collision?• Can skin sensor pick detect collision?

Distal link

Torque spring

JR3 sensor

Piece of tape

Cushion layer

shield

Sensor strip

Preliminary Results

0 1 2 3 4 5 6 7 8 90

200

400

600

800

1000

1200

1234567

0 1 2 3 4 5 6 7 8 90

200

400

600

800

1000

1200

1234567

2 m/s, k = 27.793 N mm/deg 2 m/s, k = 0.395 N mm/deg

JR3 Data

0 0.5 1 1.5 2 2.5 3

x 104

-1.2

-1

-0.8

-0.6

-0.4

-0.2

0

0.2

0.4

0.6

0.8

FxFyFzMxMyMz

0.6 0.7 0.8 0.9 1 1.1 1.2 1.3 1.4 1.5 1.6

x 104

-0.8

-0.6

-0.4

-0.2

0

0.2

0.4

0.6

0.8

1

1.2

2 m/s, k = 27.793 N mm/deg 2 m/s, k = 0.395 N mm/deg

To do:

• Find optimal frequency division– Noise vs response

• Improve experimental setup– Ensure configuration– Stiffen target– Find optimal skin thickness