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: "combining simulations and real robot experiments for bayesian optimization of bipedal gait stabilization"
  Abstract: Walking controllers often require parametrization which must be tuned according to some cost function. To estimate these parameters, simulations can be performed which are cheap but do not fully represent reality. Real-robot experiments, on the other hand, are more expensive and lead to hardware wear-off. In this paper, we propose an approach for combining simulations and real experiments to learn gait stabilization parameters. We use a Bayesian optimization method which selects the most informative points in parameter space to evaluate based on the entropy of the cost function to optimize. Experiments with the igus Humanoid Open Platform demonstrate the effectiveness of our approach.

Connected through hyperedge HE-1 (induced by source paper "nimbro robots winning robocup 2018 humanoid adultsize soccer competitions"):
  with members:
    - "grown up nimbro robots winning robocup 2017 humanoid adultsize soccer competitions"
    - "hierarchical and state based architectures for robot behavior planning and control"
    - "fused angles a representation of body orientation for balance"
    - "omnidirectional bipedal walking with direct fused angle feedback mechanisms"
    - "robocup 2016 humanoid teensize winner nimbro robust visual perception and soccer behaviors"
    - "a monocular vision system for playing soccer in low color information environments"
    - "nimbro op2x adult sized open source 3d printed humanoid robot"
    - "online visual robot tracking and identification using deep lstm networks"

Connected through hyperedge HE-2 (induced by source paper "nimbro op2x adult sized open source 3d printed humanoid robot"):
  with members:
    - "on the convergence of adam and beyond"
    - "grown up nimbro robots winning robocup 2017 humanoid adultsize soccer competitions"
    - "fused angles a representation of body orientation for balance"
    - "omnidirectional bipedal walking with direct fused angle feedback mechanisms"
    - "a ros based software framework for the nimbro op humanoid open platform"
    - "a monocular vision system for playing soccer in low color information environments"
    - "child sized 3d printed igus humanoid open platform"
    - "nimbro op2 grown up 3d printed open humanoid platform for research"

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)