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: "a convex model of momentum dynamics for multi contact motion generation"
  Abstract: Linear models for control and motion generation of humanoid robots have received significant attention in the past years, not only due to their well known theoretical guarantees, but also because of practical computational advantages. However, to tackle more challenging tasks and scenarios such as locomotion on uneven terrain, a more expressive model is required. In this paper, we are interested in contact interaction-centered motion optimization based on the momentum dynamics model. This model is non-linear and non-convex; however, we find a relaxation of the problem that allows us to formulate it as a single convex quadratically-constrained quadratic program (QCQP) that can be very efficiently optimized. Furthermore, experimental results suggest that this relaxation is tight and therefore useful for multi-contact planning. This convex model is then coupled to the optimization of end-effector contacts location using a mixed integer program, which can be solved in realtime. This becomes relevant e.g. to recover from external pushes, where a predefined stepping plan is likely to fail and an online adaptation of the contact location is needed. The performance of our algorithm is demonstrated in several multi-contact scenarios for humanoid robot.

Connected through hyperedge HE-1 (induced by source paper "contact planning for the anymal quadruped robot using an acyclic reachability based planner"):
  with members:
    - "learning agile and dynamic motor skills for legged robots"
    - "simultaneous contact gait and motion planning for robust multi legged locomotion via mixed integer convex optimization"
    - "hierarchical planning of dynamic movements without scheduled contact sequences"
    - "planning and execution of dynamic whole body locomotion for a hydraulic quadruped on challenging terrain"

Connected through hyperedge HE-2 (induced by source paper "a robust walking controller based on online step location and duration optimization for bipedal locomotion"):
  with members:
    - "walking stabilization using step timing and location adjustment on the humanoid robot atlas"
    - "online adaptation for humanoids walking on uncertain surfaces"
    - "dynamic walking over rough terrains by nonlinear predictive control of the floating base inverted pendulum"
    - "when to make a step tackling the timing problem in multi contact locomotion by topp mpc"
    - "momentum control with hierarchical inverse dynamics on a torque controlled humanoid"
    - "structured contact force optimization for kino dynamic motion generation"
    - "step timing adjustment a step toward generating robust gaits"
    - "stepping stabilization using a combination of dcm tracking and step adjustment"

Connected through hyperedge HE-3 (induced by source paper "motion planning for quadrupedal locomotion coupled planning terrain mapping and whole body control"):
  with members:
    - "differential dynamic programming for multi phase rigid contact dynamics"
    - "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"
    - "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"

Connected through hyperedge HE-4 (induced by source paper "a receding horizon push recovery strategy for balancing the icub humanoid robot"):
  with members:
    - "a whole body software abstraction layer for control design of free floating mechanical systems"
    - "torque controlled stepping strategy push recovery design and implementation on the icub humanoid robot"
    - "trajectory generation for multi contact momentum control"

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)