Implementation of trot-to-gallop transition and subsequent gallop on the MIT Cheetah I
Implementation of trot-to-gallop transition and subsequent gallop on the MIT Cheetah I
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DOI：
10.1177/0278364916640102
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发表时间：
2016-11-01
影响因子：
9.2
通讯作者：
Kim, Sangbae
中科院分区：
文献类型：
--
作者：
Hyun, Dong Jin;Lee, Jongwoo;Kim, Sangbae
本文演示了四足机器人从小跑到飞奔的过渡和随后的稳定飞奔。麻省理工学院的Cheetah I是一个平面四足平台，用于高速跑步，在跑步机上以3.2米/秒的速度完成这些任务（弗劳德数为2.1）。该控制器受益于生物学发现的线索，它结合了(1)步态模式调制，通过本体感觉触地反馈强加预定义的步态模式，(2)可调的四肢平衡点脚端轨迹，有意调节地面反作用力，以及(3)可编程的腿部顺应性，为腿-地交互提供瞬时反射。在控制器中集成了一个惯性测量单元传感器，以便在着陆时调节腿的攻角。对描述四足运动时空特征的控制参数进行降维，并通过动态仿真和实验对参数值进行调优。给定给定的虚拟腿柔度和期望的腿攻角，分别求出稳定小跑和飞奔步态的平衡点足端轨迹和四腿之间的相位关系。我们提出了一种简单的抛接步态转换策略，该策略通过线性变化过渡期间的控制参数连接两个稳定的极限环，即小跑和飞奔。仿真和实验均取得了成功的步态转换。综合分析了麻省理工学院猎豹I型实验小跑-飞奔过渡的特点。相位图表明，该控制器在小跑和疾驰中均实现了稳定的极限环，实现了从小跑到疾驰的高速步态转换。
This paper presents a demonstration of the trot-to-gallop transition and subsequent stable gallop in a robotic quadruped. The MIT Cheetah I, a planar quadruped platform for high-speed running, achieves these tasks with a speed of 3.2 m/s (Froude number of 2.1) on a treadmill. The controller benefits from clues from biological findings and it incorporates (1) a gait pattern modulation that imposes predefined gait patterns with a proprioceptive touchdown feedback, (2) tunable equilibrium-point foot-end trajectories for four limbs that intentionally modulate ground reaction forces, and (3) programmable leg compliance that provides instantaneous reflexes to leg-ground interaction. An inertial measurement unit sensor is integrated with the controller in order to regulate leg angles of attack at touchdown. We reduce the dimension of the control parameters which describe temporal/spatial characteristics of quadruped locomotion, and the values are tuned via dynamic simulation and then experiment. Given a pre-defined virtual leg compliance and a desired angle of attack of legs, the equilibrium-point foot-end trajectories and phase relationships between four legs for stable trot and gallop gaits are found independently. We propose a simple throw-and-catch gait transition strategy which connects two stable limit cycles, the trot and the gallop, by linearly varying control parameters during the transition period. Successful gait transition is achieved in both simulation and experiment. Comprehensive analysis on the characteristics of the MIT Cheetah I experimental trot-to-gallop transition is provided. The phase portraits imply that stable limit cycles are achieved with the proposed controller in both trot and gallop, which enables the trot-to-gallop gait transition at high speed.