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: "rigid vs compliant contact an experimental study on biped walking"
  Abstract: In this paper, the main goal is to present an experimental comparison of the two prevailing contact modeling approaches of bipedal locomotion, i. e. rigid versus compliant contact model. To do this, first, an explicit dynamics model for the robot multibody with rigid model of contact for various phases of walking is developed. Then, in order to develop a model with compliant contact, a physically oriented software is exploited and using its tools the robot multibody is modeled. To model the unilateral contact in interaction points in this software, a nonlinear compliant contact model is proposed. Finally, the drive mechanism dynamics is modeled through a linear identification routine. By adding the drive system dynamics to both models, the procedure of modeling is completed. In order to compare the performance of the developed models, obtained results from these models are compared to the empirical measurements from bipedal walking of the human-size humanoid robot SURENA III, which has been designed and fabricated at CAST, university of Tehran. This comparison shows the merit of both models in estimating dynamic behavior, while the model with rigid contact with less complexity can be employed for model-based motion optimization, analysis as well as control, and the model with compliant contact with more complexity is suitable for more realistic simulation scenarios.

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)