human: Given a node-centered hypergraph: <hypergraph>, where nodes represent papers and hyperedges represent sets of papers co-cited by a source paper.

Details of the hypergraph:
Center node: "a classification of 3r orthogonal manipulators by the topology of their workspace"
  Abstract: A classification of a family of 3-revolute (3R) positining manipulators is established. This classification is based on the topology of their workspace. The workspace is characterized in a half-cross section by the singular curves. The workspace topology is defined by the number of cusps and nodes that appear on these singular curves. The design parameters space is shown to be divided into nine domains of distinct workspace topologies, in which all manipulators have similar global kinematic properties. Each separating surface is given as an explicit expression in the DH-parameters.

Connected through hyperedge HE-1 (induced by source paper "cuspidal and noncuspidal robot manipulators"):
  with members:
    - "non singular assembly mode changing motions for 3 rpr parallel manipulators"
    - "classification of one family of 3r positioning manipulators"
    - "workspace and assembly modes in fully parallel manipulators a descriptive study"
    - "an exhaustive study of the workspace topologies of all 3r orthogonal manipulators with geometric simplifications"

Connected through hyperedge HE-2 (induced by source paper "singular curves in the joint space and cusp points of 3 rpr parallel manipulators"):
  with members:
    - "definition sets for the direct kinematics of parallel manipulators"
    - "singular curves and cusp points in the joint space of 3 rpr parallel manipulators"
    - "workspace and assembly modes in fully parallel manipulators a descriptive study"

Connected through hyperedge HE-3 (induced by source paper "singular curves and cusp points in the joint space of 3 rpr parallel manipulators"):
  with members:
    - "definition sets for the direct kinematics of parallel manipulators"

Connected through hyperedge HE-4 (induced by source paper "an exhaustive study of the workspace topologies of all 3r orthogonal manipulators with geometric simplifications"):
  with members:
    - "classification of one family of 3r positioning manipulators"

Question: Please tell me which class the center node belongs to. The 40 classes are: cs.NA(Numerical Analysis), cs.MM(Multimedia), cs.LO(Logic in Computer Science), cs.CY(Computers and Society), cs.CR(Cryptography and Security), cs.DC(Distributed, Parallel, and Cluster Computing), cs.HC(Human-Computer Interaction), cs.CE(Computational Engineering, Finance, and Science), cs.NI(Networking and Internet Architecture), cs.CC(Computational Complexity), cs.AI(Artificial Intelligence), cs.MA(Multiagent Systems), cs.GL(General Literature), cs.NE(Neural and Evolutionary Computing), cs.SC(Symbolic Computation), cs.AR(Hardware Architecture), cs.CV(Computer Vision and Pattern Recognition), cs.GR(Graphics), cs.ET(Emerging Technologies), cs.SY(Systems and Control), cs.CG(Computational Geometry), cs.OH(Other Computer Science), cs.PL(Programming Languages), cs.SE(Software Engineering), cs.LG(Machine Learning), cs.SD(Sound), cs.SI(Social and Information Networks), cs.RO(Robotics), cs.IT(Information Theory), cs.PF(Performance), cs.CL(Computation and Language), cs.IR(Information Retrieval), cs.MS(Mathematical Software), cs.FL(Formal Languages and Automata Theory), cs.DS(Data Structures and Algorithms), cs.OS(Operating Systems), cs.GT(Computer Science and Game Theory), cs.DB(Databases), cs.DL(Digital Libraries), cs.DM(Discrete Mathematics). Directly output the class name.

gpt: cs.RO(Robotics)