Trajectory-free dynamic locomotion using key trend states for biped robots with point feet

Han L Q, Chen X C, Yu Z G, et al

Sci China Inf Sci, 2023, 66(8): 189201

Biped robots can not only cross complex environment such as ravines and rocks, but can also interact in more diverse activities with people. A biped robot with point feet is called an underactuated biped robot (UBR) because there is no driving device at the contact point between the foot and the ground. The dynamic walking of a UBR usually requires gait planning and its trajectory generation methods often use simplified models. However, the joint coupling effect caused by dynamic attributes is prominent in the dynamic motion of the robot. To solve this problem, full model optimization was studied. Optimization of the whole body dynamic (WBD) model consumes more computing resources with an increase in the degrees of freedom (DoFs). In addition to the above problems, the uncontrollability of the DoFs of UBR requires the motion trajectory adjusted online. In the dynamic walking control of a UBR, it was found that the influence of the joint trajectory tracking error on walking stability is not serious. Yin et al. proposed a robot control framework based on a trajectory-free and realized computer animation design. Because the dynamic constraints of the actual robot were not considered, it could not be directly used in an experiment. Besides, upper-body attitude control and foothold adjustment are key to making the robot balanced. The traditional method makes it difficult to achieve stable attitude control for robots with little difference in mass distribution among parts. The foothold adjustment is limited by the state of the previous step and the kinematic singularity.

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