Design concepts and implementation of the Lightweight Advanced Robotic Arm Demonstrator (LARAD)

Beyond the current ExoMars programme, the European Space Agency (ESA) is investigating a range of technology developments and exploration mission opportunities leading to a future Mars Sample Return Mission (MSR), a critical next in the exploration of Mars. To fulfil their scientific objectives, all of these missions require an arm with a long reach capable of performing a variety of tasks in stringent environmental conditions, such as low gravity sampling and precise sample handling and insertion. As part of a CREST-2 project supported by the UK Space Agency (UKSA), a consortium of UK companies have co-founded and developed LARAD, a new Lightweight Advanced Robotic Arm Demonstrator to address some of the underlying challenges related both to the design as well as operation of long arms to perform the payload deployment and sample return operations of future missions. The 15kg terrestrial demonstrator is built as a 2m long arm with 6 degrees of freedom. This arm is capable of deploying a payload with a mass up to 6kgs or operating a 4kg end-effector at 2m. It is using cutting edge technologies on both the hardware and software levels. The mechanical structure of the arm has been manufactured using an array of new processes such as optimised 3D printed titanium Additive Layer Manufactured (ALM) joints, Titanium/Silicon carbide metallic composites, and 3D printed harness routing drums. A modular joint design has been produced, featuring three mechanical sizes of joints each with integrated low level communication and motor drive. The electronics, software and sensors used in the joints are common across all sizes, increasing modularity. To achieve precise positioning, very high resolution absolute position sensing is used on-board. The arm uses novel collision avoidance and path-planning strategies combined with classical control loops. The On-board Control System?s state machine combines different control strategies/modes (i.e. joint trajectory tracking, direct motor control, autonomous placement) depending on the high level user operation requirements. The high level On Board Computer (OBC) is Robot Operating System (ROS) based, enabling a flexible software approach. This project will provide a unique and representative platform to plan and rehearse science operations with full mass payload and instruments, unlike typical planetary arm developments that require scaled-mass end-effector. This paper describes the current state-of-the-art in planetary robotics and provides an overview of the top-level architecture, implementation and laboratory testing phases for the LARAD robotic arm.Peer reviewe

European Radioisotope Thermoelectric Generators (RTGs) and Radioisotope Heater Units (RHUs) for Space Science and Exploration

Radioisotope power systems utilising americium-241 as a source of heat have been under development in Europe as part of a European Space Agency funded programme since 2009. The aim is to develop all of the building blocks that would enable Europe to launch and operate deep space and planetary missions in environments where use of solar power or alternative power generation technologies is challenging. Although some technical and policy work activity predate the ESA programme, the maturity of the technology has now reached a level that it can be incorporated in mission studies and roadmaps targeting the period from the mid 2020s onwards. This paper describes the state of the art in European radioisotope thermoelectric generators and radioisotope heater units. This paper includes: the evolution of the technical programme in detail; descriptions of the design; evolution of RTG and RHU devices from laboratory prototypes to more advanced fully functional systems; and experimental data obtained to date. This paper also outlines the technical challenges and multidisciplinary skills required to develop what is a world leading, original, significant and transformative technology solution for planetary science and exploration missions from the mid 2020s onwards.JRC.G.I.3-Nuclear Fuel Safet