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目的:稳定站立和姿态保持是双足机器人正常作业的前提,但各种不确定的外部扰动不可避免。机器人需要通过协调关节运动使其快速恢复到原先的稳定站立状态。创新点:本文提出一种开环bang-bang-bang控制方法,根据扰动情况设计髋关节力矩曲线,可以同时恢复欠驱动双足机器人的平衡状态和身体姿态。与闭环控制相比,本方法恢复更为迅速。方法:首先,将外力扰动情况分为3类:1)外力通过质心,扰动仅改变平衡状态不改变身体姿态;2)外力矩扰动,扰动仅改变身体姿态不改变平衡状态;3)外力不通过质心,扰动同时改变平衡状态和身体姿态(图2)。然后,针对不同扰动情况提出对应的3种开环bang-bang-bang控制方法以及对应的髋关节力矩曲线:1)针对扰动情况1的STB控制(式14),在恢复水平稳定状态的同时不改变原先的身体直立姿态;2)针对扰动情况2的ATB控制(式18),在恢复身体直立姿态的同时不改变水平稳定状态;3)针对扰动情况3的UTB控制(式32),可以同时恢复水平稳定状态以及原先的身体直立姿态。并证明了针对最大可恢复范围内的扰动,本文的控制方法都可以同时恢复双足机器人的平衡状态和身体姿态。最后,通过4组仿真实验验证了本文方法的有效性和相比闭环控制的快速性。结论:针对欠驱动双足机器人站立的扰动恢复问题,提出一种基于髋策略的bang-bang-bang控制方法。该方法可迅速同时恢复机器人的平衡状态及身体姿态。
OBJECTIVE: Stable standing and attitude keeping are the prerequisites for the normal operation of biped robot, but various uncertain external disturbances are inevitable. The robot needs to quickly restore the original stable standing state by coordinating the joint movement. Innovative point: In this paper, an open-loop bang-bang-bang control method is proposed. According to the disturbance situation, the hip moment curve can be designed to restore the balance state and body posture of under-actuated biped robot at the same time. Compared with the closed-loop control, the method recovered more quickly. Methods: First, the external disturbance is divided into three categories: 1) the external force through the center of mass, disturbance only changes the balance state does not change the body posture; 2) external torque disturbance, disturbance only changes the body posture does not change the balance state; 3) external force does not pass The center of mass, perturbation, changes both balance and body posture (Figure 2). Then, three kinds of open-loop bang-bang-bang control methods and corresponding hip joint torque curves are proposed according to different disturbance situations: 1) For the STB control of disturbance 1 (Equation 14), while restoring the horizontal steady state Changing the original body upright posture; 2) ATB control (Equation 18) for disturbance case 2, without changing the horizontal steady state while restoring body upright posture; 3) UTB control (Equation 32) for disturbance case 3, Restore the level of stability and the original body upright posture. It is also proved that the control method in this paper can restore the balance and body posture of biped robot at the same time for the disturbance in the maximum recoverable range. Finally, four groups of simulation experiments verify the effectiveness of the proposed method and the rapidity of closed-loop control. CONCLUSION: A bang-bang-bang control method based on hip strategy is proposed to solve the problem of disturbance recovery of underactuated biped robot. This method quickly and simultaneously restores the robot’s balance and body posture.