Robot safety: Compliance matters

WITH THEIR enhanced capabilities, robots can be the key to innovative processes and new services and have become a key part of many modern industrial facilities. While they are largely deployed in the production of goods, they can also be found in construction, healthcare and service industries. 

ISO 8373 defines an Industrial Robot as: 'An automatically controlled, reprogrammable, multipurpose manipulator programmable in three or more axes, which may be either fixed in place or mobile for use in industrial automation applications'.

Depending on the task and the selected solution, a robot can work in collaboration with the user, or work completely autonomously. 

Safety is of the highest priority when humans and robots are working side by side. Consequently, robot manufacturers are faced with a broad set of safety requirements, as reflected in numerous technical guidelines and standards. To ensure reliable performance and safety, manufacturers, suppliers, integrators and operators must assess and validate robot compliance against a range of different standards, as well as considering application-specific requirements. For example, combinations of AGVs or AMRs with collaborative robots (cobots) necessitate particularly stringent safety requirements.

Cobots (Collaborative applications)

Cobot systems can combine manual and automated assembly operations to form a hybrid system, thereby uniting the strengths of humans and robots. If wisely deployed, cobots can increase process efficiencies and product quality, as well as relieve humans from physically exhausting and repetitive work. In its 2020 report summary, the International Federation of Robotics stated: “There are still many “4d” (dull, dirty, dangerous and/or delicate) tasks that could be done by robots, improving worker health, safety and job satisfaction."

A barrier-free environment where the safety of the employee is always guaranteed is a basic requirement for a collaborative application, and technical specification ISO/TS 15066 – 'Robots and robotics – Collaborative robots' should be followed. 

ISO/TS 15066 covers:

- The design of the collaborative workspace

- The design of the collaborative operation

- Methods of collaborative working

- Changing between:

              • Collaborative/non-collaborative

              • Different methods of collaboration

- Operator controls for different applications.

The methods of collaborative working ‘speed and separation monitoring’ and ‘power and force limiting’ are particularly elaborated on in ISO/TS 15066. This includes recommendations for ‘biomechanical limits’ of pain thresholds for specific parts of the human body.

Risk assessment according to EN ISO 12100 can also be used to define the safety requirements for collaborative industrial robot applications and their working environment.

An essential component of a cobot application is the robot end effector. Obviously, it is not possible to process and handle any items without it, but it does represent a possible risk. The force required for gripping and the specific handling of the work piece are crucial safety factors. ISO TR 20218-1 outlines the interface and safety requirements for gripper systems.

Industrial robots

Successful certification of industrial robots, robotic systems, and control systems demands compliance to all applicable technical guidelines and standards, and testing should cover the following aspects:

- Heavy loads and high speeds

- Unexpected start-up or behaviour

- Collision with work pieces or the surroundings

- Ejecting work piece items

- Presence of humans in the critical area

Personal assistant & service robots

Service robots and personal assistant robots profoundly differ from industrial robots, as this robot category typically performs high-value, individual and often (semi-)autonomous actions. This means it is usually characterised by great flexibility and a high level of autonomy. To perform their tasks – which often include  replacing or supplementing human activity – personal assistant and service robots must utilise learning and re-programming features to determine and analyse their environment.

Requirements for humans and robots to work together safely include:

- Uniform standards for hardware and software components

- Industrial security and aligned communication protocols

- Efficient determination of the environment

- Short reaction times

- High intelligence of the service robot systems

- Easy and intuitive operations (such as speech and gesture control)

Mobile robots 

Mobile robots help to automate and optimise logistics processes. As they provide continuous service around the clock and can be flexibly assigned for a variety of applications, their contribution to increased efficiency and productivity is significant. 

AGVs form a floor-based conveyor network which follow fixed routes, usually along wires or magnets embedded in the ground, helping to automate and optimise logistics processes. They therefore play a major role in process automation and materials transportation across a range of sectors, including manufacturing, logistics and hospitals. In smart factories and the Industry 4.0 environment, AGVs are particularly critical for sustainably enhancing efficiency in intralogistics. However, their extremely diverse applications pose distinct challenges to manufacturers and system integrators.

Autonomous Mobile Robots (AMR) are more sophisticated and packed with sensors and powerful on-board computers that allow them to navigate dynamically using a map. They are smart enough to recognise and react to obstacles to safely perform their function in a busy environment

As AGVs and AMRs provide continuous service around the clock and can be flexibly assigned for a variety of applications, their contribution to increased efficiency and productivity is significant. While their application within industry can be varied, AGVs and AMRs all have essential subsystems in common:

Transport vehicle(s):

- Powertrain

- Energy accumulator

- Safety controls

- Positioning devices

- Data-transmission interfaces

- Charging infrastructure plus further peripheral equipment if necessary

- Guidance control system.

An Industrial Mobile Robot (IMR) is a combination of an AGV and AMR with an ‘Industrial Manipulator’ (robot). Market specific requirements that must be taken into consideration include U.S. standard ANSI/RIA R15.08 – 'Safety Standard for Autonomous Mobile Robots', and international standards ISO 10218 parts 1 and 2 – 'Robots and robotic devices - Safety requirements for industrial robots'. ANSI/RIA R15.08 divides these vehicles into different categories:

- IMR Type A – a basic type of Autonomous Mobile Robot (AMR) without any attachment

- IMR Type B - an IMR Type A plus an attachment (active or passive, e.g. conveyors, roller tables, lifting devices, fixed totes, etc., excluding manipulators).

- IMR Type C – a AMR or AGV base with a robotic manipulator

In the European Economic Area (EEA) IMRs are required to comply with the Machinery Directive, which for the UK market aligns with the Supply of Machinery (Safety) Regulations 2008. This requires a task-based risk assessment, for which the guidance in the international standard ISO 12100 – “Safety of machinery - General principles for design - Risk assessment and risk reduction” can be used, although it does not explicitly mention collaborative applications. 

Today, original equipment manufacturers, as well as other tier suppliers, are making use of new technologies for collaborative robot applications. The challenge is to guarantee safety and minimise the chance of injury when people and machines work together.

So, while robots offer exciting possibilities, it is vital that a complete risk assessment is undertaken before deployment, as you would with any machinery in the workplace. This must cover the intended use of the robot, as well as any reasonably foreseeable misuse, with the basis for this risk assessment being EN ISO 12100, in order to provide a presumption of conformity with the Machinery Directive. Manufacturers would therefore be advised to seek the support of an accredited international testing and certification body to clarify applicable international requirements, right from the specification phase.

Stewart Robinson MIET MInstMC is principal engineer and functional safety expert at TÜV SÜD

www.tuvsud.com/uk