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: "differential dynamic programming for multi phase rigid contact dynamics"
  Abstract: A common strategy to generate efficient locomotion movements is to split the problem into two consecutive steps: the first one generates the contact sequence together with the centroidal trajectory, while the second step computes the whole-body trajectory that follows the centroidal pattern. While the second step is generally handled by a simple program such as an inverse kinematics solver, we propose in this paper to compute the whole-body trajectory by using a local optimal control solver, namely Differential Dynamic Programming (DDP). Our method produces more efficient motions, with lower forces and smaller impacts, by exploiting the Angular Momentum (AM). With this aim, we propose an original DDP formulation exploiting the Karush- Kuhn-Tucker constraint of the rigid contact model. We experimentally show the importance of this approach by executing large steps walking on the real HRP-2 robot, and by solving the problem of attitude control under the absence of external contact forces.

Connected through hyperedge HE-1 (induced by source paper "learning how to walk warm starting optimal control solver with memory of motion"):
  with members:
    - "memory of motion for warm starting trajectory optimization"
    - "crocoddyl an efficient and versatile framework for multi contact optimal control"
    - "passive whole body control for quadruped robots experimental validation over challenging terrain"
    - "simultaneous contact gait and motion planning for robust multi legged locomotion via mixed integer convex optimization"
    - "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-2 (induced by source paper "accelerated admm based trajectory optimization for legged locomotion with coupled rigid body dynamics"):
  with members:
    - "structured contact force optimization for kino dynamic motion generation"
    - "trajectory generation for multi contact momentum control"

Connected through hyperedge HE-3 (induced by source paper "robust humanoid locomotion using trajectory optimization and sample efficient learning"):
  with members:
    - "locomotion planning through a hybrid bayesian trajectory optimization"
    - "walking control based on step timing adaptation"
    - "pattern generation for walking on slippery terrains"
    - "bayesian optimization using domain knowledge on the atrias biped"
    - "automatic lqr tuning based on gaussian process global optimization"
    - "sample efficient optimization for learning controllers for bipedal locomotion"
    - "robots that can adapt like animals"
    - "trajectory generation for multi contact momentum control"

Connected through hyperedge HE-4 (induced by source paper "crocoddyl an efficient and versatile framework for multi contact optimal control"):
  with members:
    - "whole body nonlinear model predictive control through contacts for quadrupeds"
    - "simultaneous contact gait and motion planning for robust multi legged locomotion via mixed integer convex optimization"
    - "motion planning for quadrupedal locomotion coupled planning terrain mapping and whole body control"
    - "a family of iterative gauss newton shooting methods for nonlinear optimal control"
    - "an efficient optimal planning and control framework for quadrupedal locomotion"
    - "trajectory optimization through contacts and automatic gait discovery for quadrupeds"
    - "balancing experiments on a torque controlled humanoid with hierarchical inverse dynamics"

Connected through hyperedge HE-5 (induced by source paper "motion planning for quadrupedal locomotion coupled planning terrain mapping and whole body control"):
  with members:
    - "simultaneous contact gait and motion planning for robust multi legged locomotion via mixed integer convex optimization"
    - "structured contact force optimization for kino dynamic motion generation"
    - "a convex model of momentum dynamics for multi contact motion generation"
    - "planning and execution of dynamic whole body locomotion for a hydraulic quadruped on challenging terrain"
    - "on line and on board planning and perception for quadrupedal 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)