add paper

README.md

@@ -56,6 +56,7 @@
 - [Enhancing Quadruped Robot Locomotion on Deformable Terrains Through Contact Perception and Terrain Classification](https://papers.ssrn.com/sol3/papers.cfm?abstract_id=4682648)
 - [Fast Traversability Estimation for Wild Visual Navigation](https://arxiv.org/abs/2305.08510)
 - [GeRM: A Generalist Robotic Model with Mixture-of-experts for Quadruped Robot](https://arxiv.org/abs/2403.13358)
+- [Hierarchical Open-Vocabulary 3D Scene Graphs for Language-Grounded Robot Navigation](https://arxiv.org/pdf/2403.17846.pdf)
 - [Learning Quadrupedal High-Speed Running on Uneven Terrain](https://www.mdpi.com/2313-7673/9/1/37)
 - [Learning Risk-Aware Quadrupedal Locomotion using Distributional Reinforcement Learning](https://arxiv.org/abs/2309.14246)
 - [Learning to walk in confined spaces using 3D representation](https://arxiv.org/abs/2403.00187)