dPAMT has focused on the precise, automated assembly process of high-fidelity segmented mirrors with individual adjustment capability in lab conditions and reduced scale. The segmented mirror tiles are equipped with a mechanism allowing precise adjustment of the mirror surface with respect to the base. Such mechanism is used to demonstrate the possibility to correct the mirror positioning errors induced by the robotic assembly process. The tripod mechanism coupled to flexure elements is able to perform an extremely accurate adjustment of each individual tile. HOTDOCK is a standard robotic mating interface supporting mechanical, data, power and thermal transfer. The core assembly process handles 3 types of connexions: single, double or triple simultaneous matings. Thanks to navigation skills of the platform and the skill-based planning, the Robotic Assembly System is able to successfully address these three types of connections. The key concept shown by dLSAFFE is its representativeness of the real assembly process with respect to scale. In a word, it demonstrates the ability to autonomously perform the assembly of a large structure with full-scale 1.5m diameter mirror tiles with a limited manipulator workspace, executed in a zero-buoyancy facility to mimic microgravity. A modular underwater manipulator was developed, and integrated with a purpose-built linear rail on the demonstrator mockup structure. This robotic assembly system is controlled by motion planning and control software components. The concept of standard interface enabling the segmented mirror tiles assembly was reused here with a set of controllable magnetic interfaces based on the HOTDOCK geometry. The software architecture of dLSAFFE is based on the concepts developed under the previous PERASPERA operational grants. Perception sensors are based on I3DS, while the perception algorithms are derived from InFuse and the overall system is integrated under the TASTE framework. dISAS was designed and implemented as a tool to support the process of in-space robotic assembly mission specification and rapid-prototyping of new concepts. It allows the user to simulate the software and hardware architectures via a powerful simulation engine. Each hardware or software component, such as structural elements, sensors, actuators, standard interfaces, or robotic manipulator is represented in this environment with a high-fidelity, user-customizable model. Generic software components such as the Assembly Manager, maintaining an internal model of the geometry of the demonstrator, and the Sequencer, encoding the assembly sequence in a behaviour tree formalism, have been developed and reused successfully across multiple demonstrators. dISAS has been used to rapidly iterate on the design of efficient AOCS controllers capable of preserving the required pointing accuracy of the spacecraft during the telescope deployment phase, despite the slow evolution of the inertia and frequency modes of the system as well as the disturbances torques that are induced by the motions of the robotic arm. Over the last 2 years, PULSAR has worked to develop, mature and demonstrate key technologies enabling next-generation concepts where large structures are autonomously assembled in orbit. This opens up new possibilities for higher-performance, more cost-effective and more ambitious future space exploration missions.
