# Autonomous Navigation of Underactuated Bipedal Robots in Height-Constrained Environments

arXiv: https://arxiv.org/abs/2109.05714 · HTML: https://mlsanity.com/paper/2109.05714/

## Key facts

- Cited by 5 papers in the map (data through 14 Oct 2026).
- Builds on 19 of its 62 references that are in the map.
- First posted on arXiv 13 Sep 2021.

## Builds on (most cited first, 19 of 19)

- [Reinforcement Learning for Robust Parameterized Locomotion Control of Bipedal Robots](https://mlsanity.com/paper/2103.14295/) (2021)
- [Safety-Critical Model Predictive Control with Discrete-Time Control Barrier Function](https://mlsanity.com/paper/2007.11718/) (2020)
- [Feedback Control of a Cassie Bipedal Robot: Walking, Standing, and Riding a Segway](https://mlsanity.com/paper/1809.07279/) (2018)
- [Collision-Free MPC for Legged Robots in Static and Dynamic Scenes](https://mlsanity.com/paper/2103.13987/) (2021)
- [Animated Cassie: A Dynamic Relatable Robotic Character](https://mlsanity.com/paper/2009.02846/) (2020)
- [3D Underactuated Bipedal Walking via H-LIP based Gait Synthesis and Stepping Stabilization](https://mlsanity.com/paper/2101.09588/) (2021)
- [Toward Safety-Aware Informative Motion Planning for Legged Robots](https://mlsanity.com/paper/2103.14252/) (2021)
- [Footstep Planning for Autonomous Walking Over Rough Terrain](https://mlsanity.com/paper/1907.08673/) (2019)
- [Rapid Trajectory Optimization Using C-FROST with Illustration on a Cassie-Series Dynamic Walking Biped](https://mlsanity.com/paper/1807.06614/) (2018)
- [An Efficiently Solvable Quadratic Program for Stabilizing Dynamic Locomotion](https://mlsanity.com/paper/1311.1839/) (2013)
- [Global Position Control on Underactuated Bipedal Robots: Step-to-step Dynamics Approximation for Step Planning](https://mlsanity.com/paper/2011.06050/) (2020)
- [Control Lyapunov Functions for Compliant Hybrid Zero Dynamic Walking](https://mlsanity.com/paper/2107.04241/) (2021)
- [Efficient Anytime CLF Reactive Planning System for a Bipedal Robot on Undulating Terrain](https://mlsanity.com/paper/2108.06699/) (2021)
- [Bipedal Hopping: Reduced-order Model Embedding via Optimization-based Control](https://mlsanity.com/paper/1807.08037/) (2018)
- [ZMP support areas for multi-contact mobility under frictional constraints](https://mlsanity.com/paper/1510.03232/) (2015)
- [Safe Adaptive Switching among Dynamical Movement Primitives: Application to 3D Limit-Cycle Walkers](https://mlsanity.com/paper/1810.00527/) (2018)
- [Non-Linear Trajectory Optimization for Large Step-Ups: Application to the Humanoid Robot Atlas](https://mlsanity.com/paper/2004.12083/) (2020)
- [Footstep and Motion Planning in Semi-unstructured Environments Using Randomized Possibility Graphs](https://mlsanity.com/paper/1610.00700/) (2016)
- [Capturability-based Pattern Generation for Walking with Variable Height](https://mlsanity.com/paper/1801.07022/) (2018)

## Built on by (most cited first, 5 of 5)

- [Adapting Rapid Motor Adaptation for Bipedal Robots](https://mlsanity.com/paper/2205.15299/) (2022)
- [Learning Forward Dynamics Model and Informed Trajectory Sampler for Safe Quadruped Navigation](https://mlsanity.com/paper/2204.08647/) (2022)
- [EmoBipedNav: Emotion-aware Social Navigation for Bipedal Robots with Deep Reinforcement Learning](https://mlsanity.com/paper/2503.12538/) (2025)
- [Autotuning Bipedal Locomotion MPC with GRFM-Net for Efficient Sim-to-Real Transfer](https://mlsanity.com/paper/2409.15710/) (2024)
- [SIESEF-FusionNet: Spatial Inter-correlation Enhancement and Spatially-Embedded Feature Fusion Network for LiDAR Point Cloud Semantic Segmentation](https://mlsanity.com/paper/2411.06991/) (2024)

## Abstract (arXiv)

Navigating a large-scaled robot in unknown and cluttered height-constrained environments is challenging. Not only is a fast and reliable planning algorithm required to go around obstacles, the robot should also be able to change its intrinsic dimension by crouching in order to travel underneath height-constrained regions. There are few mobile robots that are capable of handling such a challenge, and bipedal robots provide a solution. However, as bipedal robots have nonlinear and hybrid dynamics, trajectory planning while ensuring dynamic feasibility and safety on these robots is challenging. This paper presents an end-to-end autonomous navigation framework which leverages three layers of planners and a variable walking height controller to enable bipedal robots to safely explore height-constrained environments. A vertically-actuated Spring-Loaded Inverted Pendulum (vSLIP) model is introduced to capture the robot's coupled dynamics of planar walking and vertical walking height. This reduced-order model is utilized to optimize for long-term and short-term safe trajectory plans. A variable walking height controller is leveraged to enable the bipedal robot to maintain stable periodic walking gaits while following the planned trajectory. The entire framework is tested and experimentally validated using a bipedal robot Cassie. This demonstrates reliable autonomy to drive the robot to safely avoid obstacles while walking to the goal location in various kinds of height-constrained cluttered environments.