It’s a multi-year project to better worker safety in high radiation fields, while advancing the field of nuclear site decommissioning – a robotic arm with six degrees-of-freedom (DoF) capable of obtaining the needed radiological data from sites workers can’t access (or access safely). It’s called the Portable, High-Precision, Modular Manipulator (or simply referred to as the portable manipulator) designed by the newly established Electro-Mechanical Equipment Development (EMED) Division at Canadian Nuclear Laboratories (CNL). Led by Acting Manager, Scott Read, for the first three years of the project, and more recently by EMED’s senior Software and Instrumentation Technologist, Guy Leblond, the project team is now getting set to build and test a full-scale prototype of the field-deployable technology.
Over the last year, the project funded by Atomic Energy of Canada Limited’s Federal Nuclear Science & Technology (FNST) Work Plan, transitioned from concept to build. The team has been steadily refining the design by constructing and testing prototypes for key aspects of the design and gathering feedback from other teams at CNL who could deploy the portable manipulator in their work. They have also completed the detailed design of the electro-mechanical subsystems and made significant progress on the manipulator’s control system. Part of this work includes the design and development of “the mini arm”, a simplified and scaled down version of the portable manipulator, primarily being used to test out developments made to the control system.
One of the most significant challenges the team faced this year was achieving the desired motion and accuracy of the end effector or the tool attached at the end of the robotic arm. The portable manipulator utilizes electric motors to drive the motion of the robotic joints, and these must be commanded simultaneously to position the end effector to work effectively. This is no small feat with a control system comprised of multiple pieces of software needing to work together to provide real-time, smooth motion of the end effector(s).
To give you a sense of the manipulator’s functionality, seven custom end effectors have been designed to-date, including: a modified off-the-shelf robotic gripper for general purpose dexterous tasks, three radiation measurement tools for measuring beta and gamma radiation and gathering gamma spectroscopy data, a contamination swipe tool to understand loose contamination hazards, as well as modified drill and oscillating saw end effectors for acquiring material samples.
The team also made significant progress on the integration of the mechanical and electrical hardware, sensors and both off-the-shelf and custom software. Given the portable manipulator needs to be controlled remotely, without direct operator viewing, feedback on the position of the portable manipulator is performed entirely through position feedback sensors, onboard cameras, the use of a digital twin, and digital haptic feedback. This is where the mini arm was fully leveraged to demonstrate coordinated motion of all six DoFs, real-time coordination of the mini arm and the digital twin, motion of the mini arm through pre-planned motion paths, and real-time control of the mini arm using a haptic-feedback input device.
So what’s next? As the project enters its final year within its current FNST funding allotment, all focus is on building and testing a full-scale prototype. This 1-to-1 scale prototype will be assembled at Chalk River Laboratories where the team can refine their design even further and demonstrate their system. One of the great advantages to this system is its flexibility, which can lead to faster deployment of tools into the field.
“The portable manipulator is innovating the field of decommissioning,” says Read. “Instead of designing a fully custom suite of remote tooling for a new application, we can potentially design a simple end effector to address that custom application. The major advantage here is schedule improvement since designing a custom end effector requires significantly less effort than designing a fully customized articulating arm.”
The portable manipulator can acquire characterization data with minimal modifications to a facility. It can be assembled and deployed through a six-inch diameter cored hole in the surrounding walls or ceiling, giving teams a six DoF robotic arm in the high-hazard environment, while the worker operates it remotely from a low-hazard area. A second cored hole supports the deployment of the tool elevator, which is used to shuffle custom end effectors into the high-hazard area where the portable manipulator can pick up the end effector and progress to the next stage of work.
Learn more about the portable manipulator from when it was first introduced at CNL https://www.cnl.ca/could-space-be-the-final-frontier-for-this-novel-robotic-manipulator/
