Safe Physical Human-Robot Interaction: Measurements, Analysis … · 2016. 2. 1. · Alin...

Motivation Crash-Tests Clamping Singularity Forces Soft-tissue Synopsis

Safe Physical Human-RobotInteraction: Measurements, Analysis &

New Insights

Sami HaddadinAlin Albu-Schäffer

Gerd Hirzinger

Institute of Robotics and MechatronicsGerman Aerospace Center

2007 International Symposium on Robotics Research, November, 26.-29.Hiroshima, Japan

29.11.2007

Haddadin, Albu-Schäffer & Hirzinger @ 2007 ISRR, November, 26.-29 Hiroshima, Japan


Table of contents

1 Motivation



Table of contents

1 Motivation

2 Crash-Tests



Table of contents

1 Motivation

2 Crash-Tests

3 Clamping



Table of contents

1 Motivation

2 Crash-Tests

3 Clamping

4 Singularity Forces



Table of contents

1 Motivation

2 Crash-Tests

3 Clamping


5 Soft-tissue



Table of contents

1 Motivation

2 Crash-Tests

3 Clamping


5 Soft-tissue

6 Synopsis



Motivation



Why safety evaluation?

Industrial robots

Intuitition: These robots are dangerous!

This is not generally true!




Der Kanzler



The DLR Lightweightrobot III

DLR LWRIII:7DOF - Torque-controlled - LWR=1



The DLR Humanoid Justin

Justin:43DOF - Torque-controlled

Based on DLR-LWR III & DLR-Hand II




Goal

Environment

Safety

Requirements

safe physical

HRI

Potential

Threats

System of interest

Safe mechanical design

HW-level safety design

Safe controller design

Safe Planning

High-level safety

Safety-design level

Abst

ract

ion

leve

l

Weight, actuation, . . .

Secure data transmission,redundant sensors . . .

Collision detection, reactive control

Path planning, Velocity profile

“Around the lady”

Example



Crash-Testing in Robotics



Crash-tests at ADAC



The Head Injury Criterion

Head: Head Injury Criterion

HIC36 = maxΔt

{Δt

(1

Δt

∫ t2t1

ẍHdt)( 5

2)}

≤ 650

Δtmax = max {t2 − t1} ≤ 36ms



Evaluation of HIC

serious,

but

not

life

thre

ate

nin

g

5% AIS≥ 3

20% AIS≥ 3

Very low

Low

Medium

High

Very high

InjuryLevel

HICLevel

HIC36-Level of the LWRIII

650

1000

0 0.5 1.0 1.5 2.0 2.50

5

10

15

20

25

30

��

�

��

HIC36

TCP-Velocity [m/s]



confidence



What are the consequences?

0 50 100 150 200 250 300 350 400 450 5000

50

100

150

200

250

300

350

400HIC36(mrobot)

Robot mass mrobot[kg]

HIC

36

0.2m/s0.5m/s1.0m/s1.5m/s2.0m/s2.5m/s3.0m/s

5 10 15 20 25 30 35 40 45 500

50

100

150

200

250

300HIC36(mrobot)


HIC

36

0.2m/s0.5m/s1.0m/s1.5m/s2.0m/s2.5m/s3.0m/s

Intuition heavy ≡ dangerous does not applyStriking result! Why is that?

Running against a wall with 2m/s (≡ 7.2km/h)



Zidane



Dummy-dummy

Triaxial acceleration sensor

Average human neck length

Compliant skin covering

Neck stiffness

Emergency stoptrigger

Mimicks a HIII-dummy head

Verify saturation effect

0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 20

5

10

15

20

25

Robot velocity ẋR[m/s]

HIC

36

HIC Verification of Dummy-dummy

HybridIII dummyDummy-dummy

Very similar numerical values to HIII-dummy

From now on: Reference basis for comparison



Investigated robots

q̇1

q̇4

HIII-dummy

Dummy-dummyImpactor

q̇1

Impactor

Dummy-dummyq̇1

Impactor Dummy-dummy

q̇1



Crash-tests: All robots



Results of Head Injury Criterion

serious,

but

not

life

thre

ate

nin

g

5% AIS≥ 3

20% AIS≥ 3

Very low

Low

Medium

High

Very high

InjuryLevel

HICLevel

650

1000

0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 20

10

20

30

40

50

60

70Head Injury Criterion HIC36(ẋR)

Robot velocity ẋR[m/s]

HIC

36

LWRIIIKR3-SIKR6KR500

[email protected]/s×

[email protected]/s

×

All robots at top speed in the green area!



Contact forces

0 0.002 0.004 0.006 0.008 0.01 0.012 0.014−200

0

200

400

600

800

1000

time t[s]

Fext[N

]

Contact force Fext0.7m/s1.0m/s1.5m/s2.0m/s

0 0.005 0.01 0.015 0.02 0.025 0.03 0.035 0.04 0.045 0.05−500

0

500

1000

1500

2000

time t[s]

Fext[N

]

Contact force Fext0.2m/s0.7m/s1.0m/s1.5m/s2.0m/s

0 0.005 0.01 0.015 0.02 0.025 0.03−500

0

500

1000

1500

2000

2500

3000

time t[s]

Fext[N

]


0 0.005 0.01 0.015 0.02 0.025 0.03−500

0

500

1000

1500

2000

2500

time t[s]

Fext[N

]


KR3-SI DLR-LWRIII

KR6 KR500



Human head

Parietal

Occipital

Zygomatic

Temporal

Mandible

Maxilla

Lagrimal

Nasal

Ethmoid

Sphenoid

FrontalFacial bone FRACTURE FORCE

Mandible (A-P) 1.78kNMandible (lateral) 0.89kN

Maxilla 0.66kNZygoma 0.89kN

Cranial bone FRACTURE FORCE

Frontal 4.0kNTemporo-Parietal 3.12kN

Occiput 6.41kN



Contact forces: Frontal & Maxilla

0 10 20 30 40 50 60 70 80 90 1000

0.5

1

1.5

2

2.5x 10

4 Contact force Fext for Frontal


Fext[N

]

0.5m/s10m/sImpact Tolerance

Ffrac

SAFE {

DANGEROUS

0.5m/s steps

0 10 20 30 40 50 60 70 80 90 1000

1000

2000

3000

4000

5000

6000

7000Contact force Fext for Maxilla

Robot mass mrobot[kg]F

ext[N

]

0.5m/s10m/sImpact Tolerance

Ffrac

SAFE {

DANGEROUS

0.5m/s steps



Impact tests with human cadavers

Real cadaver experiments @20km/h ≡ 5.5m/s with impactor mass 23kgMaximum reported injury level was AIS = 3, i.e. serious

courtesy of Prof. D. Kallieris




Contact Force is a much better indicator for free impacts thanHIC

Relevant injuries as fractures are likely at typical robotvelocities

Force is sensitive to both: robot velocity and mass: LWRIIIcan drive faster without injury than KR3,6 or 500

Reflected inertia mrobot > 10kg disadvantageous above 1m/s

Contradicts intuition: KR500 is not life-threatening? → Truefor free impacts

Clamping enlarges injury potential: Force is able to detectthis, HIC is not



Impacts with clamping



Types of Clamping

High velocity

Dynamic Clamping

Low velocity

Quasi-static Clamping



Cracking a coconut

Fracture force is equivalent to the one of the frontal bone



Facial Impact Forces with Clamping

ROBOT Contact Force Maxilla Fracture?

LWRIII 0.6kN@1m/s NoLWRIII 1.2kN@2m/s YesKR3 2.2kN@2m/s YesKR6 (Cat.0&1) 5.1kN@2m/s YesKR500 (Cat.0&1) 23.6kN@2m/s Yes

ROBOT Contact Force Frontal Fracture?

LWRIII 3.5kN@2m/s NoKR3 6.9kN@2m/s YesKR6 (Cat.0&1) 16.3kN@2m/s YesKR500 (Cat.0&1) 86.3kN@2m/s Yes



Chest Impacts with Clamping

ROBOT CC[mm] VC[m/s] F xext[N]

LWRIII@2m/s 14.4(0.0) 0.035 741.6(1.3)KR3@2m/s (Cat.0) 31.2(0.0) 0.1 851.9(1.4)KR6@2m/s (Cat.0) 65.5(2.0) 0.25 2836.1(2.7)KR6@2m/s (Cat.1) 66.6(2.1) 0.25 2904.6(2.7)KR500@2m/s (Cat.0) 228.0(6.0) 0.84 14282.0(6.0)KR500@2m/s (Cat.1) 245.0(6.0) 0.89 15491.0(6.0)




Intuition heavy ≡ dangerous applies now!Confirmation by some published injury data

Relation between motor torque and inertia scalesdisadvantageous, when increasing dimensions

Human is not able anymore to widthstand such loads



Singularity Forces during Clamping




0.75 0.8 0.85 0.9 0.95 1 1.05 1.10

500

1000

1500

2000

2500

3000

3500

4000

4500

5000Clamping of the human head

TCP position [m]

F[N

]

FmaxFdetUnstoppable

1

2

3

4

5

liFfrac

dangerous

x

y

�

�

�

�

�

�

ẋ =

(vx0

)

TCP position




0.75 0.8 0.85 0.9 0.95 1 1.05 1.10

500

1000

1500

2000

2500

3000

3500

4000

4500

5000Clamping of the human head

TCP position [m]

F[N

]

FmaxFdetUnstoppable

1

2

3

4

5

liFfrac

dangerous

x

y

�

�

�

�

�

�

ẋ =

(vx0

)

TCP position

1○:2○:3○:4○:5○:

Start of critical region

Fracture forceNo hypothetical equilibrium

Reduced critical region

Limit safe configuration




Even low-inertia robots can be dangerous for some cases

Collision detection is an adequate countermeasure



Soft-tissue injuries caused by sharpviolence



Common soft-tissue injuries

Abrasion Laceration (cuts, gashes, contused wounds)

Contusion (bruises, crushes) Stab wounds



Possible Injuries: Synopsis




Quasi-static loading

With clamping Without clamping

Blunt contact Sharp contact

Near-singular configuration


Non-singular configuration


No injury

Blunt injury

1. Fractures2. Secondary injuries*

3. Shearing*

PI

WCF

WCR

IM F, CC

Soft-tissue injury

1. Laceration (cut)*

2. Laceration (stab)*

PI

WCF

WCR

IM F

Blunt injury

1. None

2. Fractures3. Secondary injuries*

τmax

PI

WCF

WCR

IM F, CC

Soft-tissue injury



τmax

PI

WCF

WCR

IM F

Soft-tissue injury

1. None2. Laceration (cut)*

τmax

PI

WCF

WCR

IM F

Physical contact




Dynamic loading

With clamping


Without clamping


Blunt injury

1. Fractures2. Internal injuries

3. Shearing*

4. Secondary injuries*

5. Laceration (crush)*

6. Laceration (gash)*

vR mR τmax

PI

WCF

WCR

IM F, CC, eA

Soft-tissue injury



3. Abrasion*

vR mRτmax

PI

WCF

WCR

IM E, F

Blunt injury

1. None

2. Fractures3. Secondary injury*

4. Laceration (crush)*

5. Laceration (gash)*

vR mRPI

WCF

WCR

IM F, CC, eA

Soft-tissue injury



3. Abrasion*

vR mRτmax

PI

WCF

WCR

IM E, F

Physical contact



The next steps

What happens if the robot is

equipped with a dangerous tool?



The next steps



Thank you very much!



Asimov’s 1st Law

”A robot may not harm a human being, or, through inaction,

allow a human being to come to harm.”

Isaac Asimov - The Caves Of Steel, p. 177-179, 1942



What about Soft-tissue Injury with SharpTools?

Soft-tissue


MotivationCrash-TestsClampingSingularity ForcesSoft-tissueSynopsis

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