Abstract: To realize stable underactuated biped walking on uneven ground, a stabilized control strategy was proposed based on the motion state of CoM of a robot. Considering ground compliance, a compliant contact model was used to describe foot-ground interaction, and a robot–ground coupling dynamic model of sagittal and lateral planes was established through decoupling modelling.Based on the gait characteristics of human variable-speed walking, a feedforward control strategy was proposed based on the motion state of CoM. Underactuated bipedal walking control was decoupled into sagittal and lateral master-slave control. The velocity of robot CoM was considered as a system output, the control was achieved by controlling the displacement of CoM, and thus stable walking was realized. Finally, the underactuated bipedal walking with the average walking speed of 0.216 m/s and the step of 0.31 leg length was realized on uneven ground where the ground height is less than 0.032 m. The experimental results show that the underactuated stable walking on uneven ground may be realized by using the proposed control strategy to control robot CoM velocity.

Key words: underactuated biped walking, state of center-of-mass(CoM), uneven ground, compliant connect, velocity control

摘要： 为实现双足机器人在不平地面上的欠驱动步行，提出一种基于质心运动状态的稳定步行控制策略。考虑地面柔性，使用柔性接触模型描述“机器人足部地面”柔性接触，并通过解耦建模的方式建立了“机器人地面”前向与侧向耦合动力学模型。根据人类变速步行特征，提出基于机器人质心速度控制的步行控制策略，将三维步行解耦为前向和侧向的主从控制，通过控制质心位移实现质心速度控制，进而实现稳定步行。搭建三维欠驱动双足步行机器人样机，在地面高度变化不大于0.032 m的不平地面上成功实现了平均步行速度0.216 m/s、步幅为0.31倍腿长的欠驱动步行。试验结果表明，所提控制策略可通过质心速度控制来实现不平地面上的欠驱动稳定步行。

关键词: 双足欠驱动步行, 质心状态, 不平地面, 柔性接触, 速度控制