This paper studies capturability and push recovery for quadrupedal locomotion. Despite the rich literature on capturability analysis and push recovery control for legged robots, existing tools are developed mainly for bipeds or humanoids. Distinct quadrupedal features such as point contacts and multiple swinging legs prevent direct application of these methods. To address this gap, we propose a switched systems model for quadruped dynamics, and instantiate the abstract viability concept for quadrupedal locomotion with a time-based gait. Capturability is characterized through a novel specification of dynamically balanced states that addresses the time-varying nature of quadrupedal locomotion and balance. A linear inverted pendulum (LIP) model is adopted to demonstrate the theory and show how the newly developed quadrupedal capturability can be used in motion planning for quadrupedal push recovery. We formulate and solve an explicit model predictive control (EMPC) problem whose optimal solution fully characterizes quadrupedal capturability with the LIP. Given this analysis, an optimization-based planning scheme is devised for determining footsteps and center of mass references during push recovery. To validate the effectiveness of the overall framework, we conduct numerous simulation and hardware experiments. Simulation results illustrate the necessity of considering dynamic balance for quadrupedal capturability, and the significant improvement in disturbance rejection with the proposed strategy. Experimental validations on a replica of the Mini Cheetah quadruped demonstrate an up to 100% improvement as compared with state-of-the-art.
翻译:本文研究可移动性和推动四倍振动的回升。 尽管关于可移动性分析的文献丰富, 并推动对断腿机器人的恢复控制, 但现有工具主要是为双腿或人造体开发的。 点接触和多摆动腿等三重特性, 防止直接应用这些方法。 为了弥补这一差距, 我们为四倍振动的动态提出一个转换的系统模型, 并即时地将四倍振动的移动加速的抽象可行性概念化。 能力化的特征是, 动态平衡状态的新规格, 解决四倍振动的机械机器人的回升控制。 现有工具主要是针对四倍振动的四倍振动性机械化和平衡性控制。 鉴于这一分析, 一个线性倒转的双曲式的双曲性笔( LIP) 模型用来展示理论, 新的四倍振动性可调整性循环性循环性( ) 模拟后, 我们设计了一个精确的模型预测性控制(EMPC) 问题, 其最佳的解决方案充分体现了与LIP的四倍增容性。