Inside Logistics

Safety First: Mobile robots in the DC

Collaboration between humans and robots can introduce some unique safety challenges


May 7, 2018
by Rob Vomiero

Rob Vomiero is a professional mechanical engineer, and is a Technical Specialist–Machine and Robot Safety with the Workplace Safety and Prevention Services.

The ever-increasing popularity of online shopping is leading to a revolution in distribution centre operations. Companies are increasingly turning to automation and robotics to boost order fulfillment in order to keep up with booming consumer demand.

The manner in which goods and products are picked is one of the main aspects of distribution centre operations that directly affects order fulfillment capability. In an effort to achieve higher picking rates, technologies and automation are being implemented that shift the picking process from ‘Person to Goods’ (PTG) picking, to ‘Goods to Person’ (GTP) picking. Rather than having human order-pickers walking throughout the distribution centre, product racks are now being transported by autonomous mobile robots to stationary human order-pickers.

In addition to increasing efficiencies, GTP picking operations allow mobile robots to take over the more demanding and repetitive tasks in an effort to reduce the incidence of musculoskeletal injuries in human workers. This enables people to focus on the portion of the order-picking process for which they are more ideally suited – those involving recognition and decision-making abilities.

Human-robot collaboration

In today’s distribution centres the increased collaboration between humans and robots can introduce some unique safety challenges. Currently there are two standards that provide guidance and direction with regards to mobile robots. The CAN/CSA Z434-14 Industrial Robot and Robot Systems Standard is the Canadian industrial robot standard (its American counterpart is the ANSI/RIA R15.06-2012), and the ANSI/ITSDF B56.5-2012 Safety Standard for Driverless, Automatic Guided Industrial Vehicles and Automated Functions of Manned Industrial Vehicles which is an American standard on Automatic Guided Vehicles (AGVs).

Unfortunately, neither of them fully addresses all aspects of mobile robots. CSA Z434-14 really only addresses multi-purpose articulating arm robots, while the ANSI/ITSDF B56.5-2012 leaves gaps regarding specific technologies that increase the autonomous nature of today’s mobile robots. Also, there is little direction provided in the B56.5-2012 on specific safety performance requirements of AGV safety-related functions.

New standards coming

On the horizon, The Robotic Industries Association (RIA) (www.robotics.org) indicates that they have assembled the R15.08 Committee to write safety standards for industrial mobile robots. In the meantime however, the CSA Z434-14 industrial robot standard does provide significant direction with regards to developing a safety strategy for safeguarding robotic equipment and other automation that can be applied to DC operations and mobile robots.

The importance of completing a comprehensive task-based risk assessment for identification of specific hazards is a cornerstone of the CSA Z434-14 robot standard, as well as many other equipment safety standards. Specifically CSA Z434-14, Part 2-Clause 4 provides direction on the risk assessment process, and Part 2-Annex DVA suggests a formalized risk assessment methodology that may be employed for documenting a risk assessment.

Risk assessment

Some specific risk and hazard considerations associated with mobile robots include: stopping capability and impact/crushing hazards due to collisions with humans; hazards/risks associated with tipping of product/product racks being transported; on-board pinch, crush or entanglement hazards due to lifting or other moving mechanical components; and hazards/risks associated with loss of control and collisions between mobile robots themselves.

Here are some tips for performing an effective risk assessment for robotics operation:

  • Initiate as early in the design/project phase as possible.
  • Assemble a team that includes all key stakeholders (engineering, maintenance, health and safety, operators, etc.); project lead (or other appropriate person) should facilitate the risk assessment meeting.
  • Identify all tasks and hazards under guidance of facilitator – see risk assessment model found in CSA Z434-14 – Part 2, Annex DVA (another suitable model could be utilized).
  • Assign risk level for each identified hazard.
  • Decide on control/safeguarding measures, and performance level or safety-related parts of the control system that achieve adequate risk reduction for each hazard.

Although new standards are in the works, existing standards do provide concrete approaches and direction for managing safety within distribution centres. Also, health and safety associations can provide significant assistance in the navigation of existing standards, as well as new upcoming standards, and in the application of best safety practices.