<p>Mobile platforms with mounted manipulators, according to the R15.08-1-2020 standard “Autonomous Mobile Robots Type C” (AMR-C), are gaining interest in the industry due to their flexibility. However, because AMR-Cs operate in dynamic, heterogeneous and sometimes unstructured environments, safety is still a major concern. Compared to statically mounted manipulators, they move very slowly. One of the main reasons is the limited monitoring space. To address this issue, we propose external monitoring tools that span a virtual safety cage around the manipulator. By placing the tool at any position, the AMR-C can close its blind spots and increase safety by adding the tool's perspective. Not only does this approach allow for the expansion of machining speed, but tasks such as gripping a workpiece from a pile become much easier. However, placing the tool in an unfamiliar environment takes time and introduces additional potential risks. Thus, actually, the problem of gripping and positioning a variable workpiece in a partially known environment is divided into positioning a known tool, specifically designed for placement in a partially known environment, at an arbitrary position, gripping, and positioning a variable workpiece in a well-monitored environment at a predefined position. We argue that the additional degrees of freedom reduce cumulative risk. To find an efficient strategy that meets the safety requirements, a simulation cumulates the risks of tool assembly and the risk of collisions due to the reduced monitoring space, and weighs the effort required to install the tools against the higher operating speed. The result of the simulation is a trade-off between the effort and risk of installing more monitoring tools and the gained speed and safety due to the increased monitoring space. After the number and position of the monitoring tools have been determined, the robot arm positions the tools one after the other. During positioning, the monitoring tools switch to positioning mode and provide additional visibility of the workspace. During positioning, the monitoring tools calibrate themselves using reference marks, providing precise position information. When completed with a task, the monitoring tools are simply collected and stored on the AMR-C. Examining a case study of a Kuka Youbot AMR-C, which supports the refurbishment of customer returns, we prototype such a monitoring tool and evaluate its use. We achieved gripping point monitoring accuracy down to the millimeter range, reliable information on whether a workpiece can be gripped or not, and reliable protection of the workspace from intruders. This makes a significantly higher working speed justifiable, which certainly overcompensates the positioning of the tool. Moreover, due to modularity and reusability paradigm applied to its development, the tool is cost-efficient and flexible in terms of extension and adaption.</p>

An Approach for Safeguarding Autonomous Mobile Robots Using Monitoring Tools

Paper Proceedings: https://asmedigitalcollection.asme.org/IMECE/IMECE2021/volume/85543

ASME 2021 International Mechanical Engineering Congress and Exposition (IMECE2021)

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