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

inside

outside

Robot controller Internal E-stop Dead mans handle Mode Teach Automatic 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

Figure 1 Lathe E-stop Key Mill Robot door Key Pallet Pallet Light curtain

Modular Safety System PNOZmulti PNOZmulti Configurator Getting Started The XOR gate (Exclusive OR gate) is a digital logic gate that is, a true output (1/HIGH) results if one, and only one, of the inputs to the gate is true. If both inputs are false (0/LOW) or both are true, a false output results. RS flip flop – A RS-flipflop is the simplest possible memory element. To understand the operation of the RS-flipflop (or RS-latch) consider the following scenarios: S=1 and R=0: So SET, Q'=0 and Q=1, Hence, the input combination S=1 and R=0 leads to the flipflop being set to Q=1. S=0 and R=1: Similar to the arguments above, the outputs become Q=0 and Q'=1. We say that the flipflop is reset. S=0 and R=0: Assume the flipflop is set (Q=0 and Q'=1), then the output of the top NOR gate remains at Q=1 and the bottom NOR gate stays at Q'=0. Similarly, when the flipflop is in a reset state (Q=1 and Q'=0), it will remain there with this input combination. Therefore, with inputs S=0 and R=0, the flipflop remains in its state. S=1 and R=1: This input combination must be avoided.

Key interchange Internal Laser Estop Robot K Door switch Door Robot Estop Key interchange external