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: "walking on partial footholds including line contacts with the humanoid robot atlas"
  Abstract: We present a method for humanoid robot walking on partial footholds such as small stepping stones and rocks with sharp surfaces. Our algorithm does not rely on prior knowledge of the foothold, but information about an expected foothold can be used to improve the stepping performance. After a step is taken, the robot explores the new contact surface by attempting to shift the center of pressure around the foot. The available foothold is inferred by the way in which the foot rotates about contact edges and/or by the achieved center of pressure locations on the foot during exploration. This estimated contact area is then used by a whole body momentum-based control algorithm. To walk and balance on partial footholds, we combine fast, dynamic stepping with the use of upper body angular momentum to regain balance. We applied this method to the Atlas humanoid designed by Boston Dynamics to walk over small contact surfaces, such as line and point contacts. We present experimental results and discuss performance limitations.

Connected through hyperedge HE-1 (induced by source paper "biped stabilization by linear feedback of the variable height inverted pendulum model"):
  with members:
    - "stair climbing stabilization of the hrp 4 humanoid robot using whole body admittance control"
    - "capturability based pattern generation for walking with variable height"
    - "dynamic walking over rough terrains by nonlinear predictive control of the floating base inverted pendulum"
    - "multi contact walking pattern generation based on model preview control of 3d com accelerations"
    - "zmp support areas for multi contact mobility under frictional constraints"

Connected through hyperedge HE-2 (induced by source paper "stair climbing stabilization of the hrp 4 humanoid robot using whole body admittance control"):
  with members:
    - "tilt estimator for 3d non rigid pendulum based on a tri axial accelerometer and gyrometer"
    - "balance control using both zmp and com height variations a convex boundedness approach"

Connected through hyperedge HE-3 (induced by source paper "robust bipedal locomotion control based on model predictive control and divergent component of motion"):
  with members:
    - "push recovery of a humanoid robot based on model predictive control and capture point"
    - "step timing adjustment a step toward generating robust gaits"
    - "stepping stabilization using a combination of dcm tracking and step adjustment"

Connected through hyperedge HE-4 (induced by source paper "unsupervised contact learning for humanoid estimation and control"):
  with members:
    - "momentum control with hierarchical inverse dynamics on a torque controlled humanoid"
    - "state estimation for a humanoid robot"

Connected through hyperedge HE-5 (induced by source paper "walking stabilization using step timing and location adjustment on the humanoid robot atlas"):
  with members:
    - "step timing adjustment a step toward generating robust gaits"
    - "an efficiently solvable quadratic program for stabilizing dynamic locomotion"

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)