Robot Safety

Dr Emma Rushforth (originally by Prof Ken Young/ Margret Low)

University of Warwick

Hazard identification & Risk Assessment

• Operational Characteristics of robots can be significantly different from other machines and equipment.– capable of high energy movements through a large

operational space.– Initiation of movement & path of robot arm different to

predict and can vary– Operating space can overlap other robots operating space or

other machines work zones– Operators can be required to work in close proximity to the

robot system.

Key Elements

• Fail safe• Reliable

– minimal down time

• Cheap• Fast implementation / modification

How it is done traditionally

• Relays• Redundancy• Physical barriers• Interlocks

Physical barriers

• Walls & interlocked gates• Barriers to material movement and maintenance• Impair view of process• Tend to cause large cells• Keep machine in as well as people out

– machining spindles– lasers

Robot controller

• Internal E-stop• Dead mans handle• Mode

– Teach• Slow• Fast

– Automatic– External

Large Cell / Multiple Access Points

• Maintenance key• All personnel

outside before system runs

Hardwired relay systems

• Inflexible• Expensive to install• Limited reusability

Modern Method

• Modular hardware• Modular software• Programmable /

configurable systems• Networks

– minimal wiring

Pilz SafetyBUS p and SafetyNET p

Light curtains

Machine access guarding Transmitter, receiver and two corner mirrors used for machine guarding

Radar detectors/Light curtains

• Can be active or inactive• Programmable for coverage• Allow increased safety during certain parts of

cycle• Require fast response to incursion

Radar/Light curtains

Variable protection zones Light curtain blanking/muting

Tool pallet/AGV variable protection zone

Programmable systems

• Function block based• Dual/Triple redundant• Programming requires direct contact with a

specialist tool & original program code for program development/alteration

• Monitoring/maintenance software tool does not permit programming

What are the Dangers

• Functionality hidden in software• Easy to program could mean easy to bypass

– software management (passwords, access, historical records)

• What is the effect of a device or network failure– not all networks are safe & some will mix safe &

unsafe devices together on a single network

Control Networks

I n f o r m a t i o n

C o n t r o l

2 4 v d c

5 0 9 - B O D

D e v i c e S a f e t y

I N F O R M A T I O N L A Y E RM E S , M I S , D a t aL o g g i n g

C O N T R O L L A Y E RH M I , P r o g r a m m i n g , A l a r m i n g ,R o b o t s

S e n s o r s , D r i v e s , R e m o t e I / OP n e u m a t i c V a l v e s

D E V I C E L A Y E R S

S A F E T Y - L i g h t C u r t a i n s , L a s e rS c a n n e r s , R e m o t e I / O - D o o rI n t e r l o c k s , E m e r g e n c y S t o p s ,

E t h e r n e t

C o n t r o l N e t

D e v i c e N e t S a f e t y b u s p

R o b o t c o n t r o l l e r s

D e v i c e N e t

Lathe

MillRobot

Light curtain

door

Key

Key

Pallet

PalletFigure 1

E-stop

Modular Safety System PNOZmultiPNOZmulti Configurator Getting Started

Robot

DoorKey interchangeexternal

KDoor switch

Key interchangeInternal

RobotEstop

LaserEstop