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: "structured contact force optimization for kino dynamic motion generation"
  Abstract: Optimal control approaches in combination with trajectory optimization have recently proven to be a promising control strategy for legged robots. Computationally efficient and robust algorithms were derived using simplified models of the contact interaction between robot and environment such as the linear inverted pendulum model (LIPM). However, as humanoid robots enter more complex environments, less restrictive models become increasingly important. As we leave the regime of linear models, we need to build dedicated solvers that can compute interaction forces together with consistent kinematic plans for the whole-body. In this paper, we address the problem of planning robot motion and interaction forces for legged robots given predefined contact surfaces. The motion generation process is decomposed into two alternating parts computing force and motion plans in coherence. We focus on the properties of the momentum computation leading to sparse optimal control formulations to be exploited by a dedicated solver. In our experiments, we demonstrate that our motion generation algorithm computes consistent contact forces and joint trajectories for our humanoid robot. We also demonstrate the favorable time complexity due to our formulation and composition of the momentum equations.

Connected through hyperedge HE-1 (induced by source paper "accelerated admm based trajectory optimization for legged locomotion with coupled rigid body dynamics"):
  with members:
    - "differential dynamic programming for multi phase rigid contact dynamics"
    - "trajectory generation for multi contact momentum control"

Connected through hyperedge HE-2 (induced by source paper "data efficient and safe learning for locomotion via simplified model"):
  with members:
    - "dynamic locomotion for passive ankle biped robots and humanoids using whole body locomotion control"
    - "tossingbot learning to throw arbitrary objects with residual physics"
    - "end to end safe reinforcement learning through barrier functions for safety critical continuous control tasks"
    - "learning symmetric and low energy locomotion"
    - "model ensemble trust region policy optimization"
    - "stair climbing stabilization of the hrp 4 humanoid robot using whole body admittance control"
    - "fast kinodynamic bipedal locomotion planning with moving obstacles"
    - "a general safety framework for learning based control in uncertain robotic systems"

Connected through hyperedge HE-3 (induced by source paper "an open torque controlled modular robot architecture for legged locomotion research"):
  with members:
    - "stanford doggo an open source quasi direct drive quadruped"
    - "quasi direct drive for low cost compliant robotic manipulation"
    - "learning a structured neural network policy for a hopping task"
    - "sim to real learning agile locomotion for quadruped robots"
    - "oncilla robot a versatile open source quadruped research robot with compliant pantograph legs"
    - "cable driven actuation for highly dynamic robotic systems"
    - "momentum control with hierarchical inverse dynamics on a torque controlled humanoid"

Connected through hyperedge HE-4 (induced by source paper "robust humanoid contact planning with learned zero and one step capturability prediction"):
  with members:
    - "unified multi contact fall mitigation planning for humanoids via contact transition tree optimization"
    - "efficient humanoid contact planning using learned centroidal dynamics prediction"
    - "capturability based pattern generation for walking with variable height"
    - "walking stabilization using step timing and location adjustment on the humanoid robot atlas"
    - "simultaneous contact gait and motion planning for robust multi legged locomotion via mixed integer convex optimization"
    - "a mpc walking framework with external contact forces"
    - "step timing adjustment a step toward generating robust gaits"

Connected through hyperedge HE-5 (induced by source paper "feasible region an actuation aware extension of the support region"):
  with members:
    - "heuristic planning for rough terrain locomotion in presence of external disturbances and variable perception quality"
    - "application of wrench based feasibility analysis to the online trajectory optimization of legged robots"
    - "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"
    - "minkowski sum of polytopes defined by their vertices"
    - "minkowski sum of hv polytopes in rn"

Connected through hyperedge HE-6 (induced by source paper "on the hardware feasibility of nonlinear trajectory optimization for legged locomotion based on a simplified dynamics"):
  with members:
    - "feasible region an actuation aware extension of the support region"
    - "efficient humanoid contact planning using learned centroidal dynamics prediction"
    - "application of wrench based feasibility analysis to the online trajectory optimization of legged robots"
    - "passive whole body control for quadruped robots experimental validation over challenging terrain"
    - "real time motion planning of legged robots a model predictive control approach"

Connected through hyperedge HE-7 (induced by source paper "learning a structured neural network policy for a hopping task"):
  with members:
    - "whole body nonlinear model predictive control through contacts for quadrupeds"
    - "emergence of locomotion behaviours in rich environments"
    - "proximal policy optimization algorithms"
    - "hierarchical planning of dynamic movements without scheduled contact sequences"
    - "trust region policy optimization"
    - "learning contact rich manipulation skills with guided policy search"
    - "fast and accurate deep network learning by exponential linear units elus"
    - "end to end training of deep visuomotor policies"

Connected through hyperedge HE-8 (induced by source paper "efficient humanoid contact planning using learned centroidal dynamics prediction"):
  with members:
    - "simultaneous contact gait and motion planning for robust multi legged locomotion via mixed integer convex optimization"
    - "a generalized mixed integer convex program for multilegged footstep planning on uneven terrain"
    - "multi contact walking pattern generation based on model preview control of 3d com accelerations"

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)