Configuration design and prototype development of a remote-centered parallel welding robot

•A 2URR-RRC parallel mechanism is proposed for vacuum chamber welding and cutting.•Prototype motion experiments confirm the design's rationality and feasibility.•The correctness of the design is validated through prototype experiments. The vacuum chamber is one of the main components of the fusion device, which is used to support the internal components of the vacuum chamber and the mechanical loads caused by its operation. The vacuum chamber is generally processed by double-layer stainless steel plate welding process to ensure the vacuum requirement. To effectively weld and repair the inner weld of a double-layer vacuum chamber, this paper proposes a design method for a remote-centered parallel welding robot (RPWR) system suitable for remote operation. The remote motion center mechanism is used to realize the robot's welding and repairing tasks around the inside of the vacuum chamber with fixed repair holes. The validity of the configuration design was established through spiral theory. According to the characteristics of this remote center welding mechanism, the forward and reverse kinematic equations are derived by using chain length constraints and vector method. And the correctness of the derivation of the forward and reverse kinematic equations is verified through numerical examples. To verify the correctness of the design method of the RPWR system, a test prototype was built and trajectory control experiments around the fixed repair holes were carried out, which verified the correctness of the whole system design.