This paper presents a hierarchical controller and extracts the singular configurations based on underactuated system and optimal distribution of forces. Unlike multi-legged and large-sole robots, biped robot with point contact cannot maintain a stable standing state, much less to adjust attitude and resist external impact. The support domain of point-foot bipedal robot degenerates into a line segment consisting of two footholds, introducing the underdactuated characteristic that challenges traditional algorithms based on polygonal domains and full variable optimization. To fully exploit the dynamic connection between support line and balance control, the accurate model is established as feedforward terms using virtual leg and floating reference system. The dynamics model is decomposed into an underactuated module and a force distribution module for hierarchical control, in which the former determines the control forces of base and the singularity corresponding to robot configuration, and the latter distributes forces on each leg according to its capability by solving a quadratic programming with constraints. The results verify the advanced stability of attitude adjustment and impact from external force of biped robot with point contact comparing to model predictive control, which is improved based on robot’s singular configuration.

中文翻译：

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点接触双足机器人的奇异配置和欠驱动平衡控制

本文提出了一种分层控制器，并基于欠驱动系统和最佳力分布提取奇异配置。与多足、大底机器人不同，点接触的双足机器人不能保持稳定的站立状态，更不用说调整姿态和抵抗外部冲击。点足双足机器人的支撑域退化为由两个立足点组成的线段，引入了欠驱动特性，挑战了基于多边形域和全变量优化的传统算法。为了充分利用支撑线和平衡控制之间的动态联系，使用虚拟腿和浮动参考系统建立了准确的模型作为前馈项。将动力学模型分解为欠驱动模块和力分布模块进行分层控制，其中前者确定机器人配置对应的基座控制力和奇异点，后者通过求解根据其能力分配每条腿上的力。有约束的二次规划。结果验证了点接触双足机器人姿态调节和外力冲击的先进稳定性，与基于机器人奇异构型改进的模型预测控制相比。