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: "fast trajectory optimization for legged robots using vertex based zmp constraints"
  Abstract: This paper combines the fast Zero-Moment-Point (ZMP) approaches that work well in practice with the broader range of capabilities of a Trajectory Optimization formulation, by optimizing over body motion, footholds and Center of Pressure simultaneously. We introduce a vertex-based representation of the support-area constraint, which can treat arbitrarily oriented point-, line-, and area-contacts uniformly. This generalization allows us to create motions such quadrupedal walking, trotting, bounding, pacing, combinations and transitions between these, limping, bipedal walking and push-recovery all with the same approach. This formulation constitutes a minimal representation of the physical laws (unilateral contact forces) and kinematic restrictions (range of motion) in legged locomotion, which allows us to generate various motion in less than a second. We demonstrate the feasibility of the generated motions on a real quadruped robot.

Connected through hyperedge HE-1 (induced by source paper "learning agile and dynamic motor skills for legged robots"):
  with members:
    - "learning symmetric and low energy locomotion"
    - "sim to real transfer of robotic control with dynamics randomization"
    - "sim to real learning agile locomotion for quadruped robots"
    - "feedback control for cassie with deep reinforcement learning"
    - "control of a quadrotor with reinforcement learning"
    - "an efficient optimal planning and control framework for quadrupedal locomotion"
    - "learning locomotion skills using deeprl does the choice of action space matter"
    - "emergence of locomotion behaviours in rich environments"

Connected through hyperedge HE-2 (induced by source paper "application of wrench based feasibility analysis to the online trajectory optimization of legged robots"):
  with members:
    - "simultaneous contact gait and motion planning for robust multi legged locomotion via mixed integer convex optimization"
    - "the actuation consistent wrench polytope awp and the feasible wrench polytope fwp"
    - "dynamic walking over rough terrains by nonlinear predictive control of the floating base inverted pendulum"

Connected through hyperedge HE-3 (induced by source paper "contact implicit optimization of locomotion trajectories for a quadrupedal microrobot"):
  with members:
    - "an efficient optimal planning and control framework for quadrupedal locomotion"
    - "trajectory optimization through contacts and automatic gait discovery for quadrupeds"
    - "planning and execution of dynamic whole body locomotion for a hydraulic quadruped on challenging terrain"

Connected through hyperedge HE-4 (induced by source paper "simultaneous contact gait and motion planning for robust multi legged locomotion via mixed integer convex optimization"):
  with members:
    - "motion planning for quadrupedal locomotion coupled planning terrain mapping and whole body control"
    - "the actuation consistent wrench polytope awp and the feasible wrench polytope fwp"
    - "trajectory optimization through contacts and automatic gait discovery for quadrupeds"
    - "hierarchical planning of dynamic movements without scheduled contact sequences"
    - "planning and execution of dynamic whole body locomotion for a hydraulic quadruped on challenging terrain"

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)