JOURNAL OF COMPUTERS (JCP)
ISSN : 1796-203X
Volume : 3    Issue : 8    Date : August 2008

A ZMP Feedback Control for Biped Balance and its Application to In-Place Lateral Stepping Motion
Satoshi Ito, Shinya Amano, Minoru Sasaki, and Pasan Kulvanit
Page(s): 23-31
Full Text:
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Abstract
Many biped robot control schemes adopt a zero moment point (ZMP) criterion, where the motion is
initially planned as the positional trajectories such that ZMP stays within the support polygon, while
the feedback control of each joint is later applied to follow the planned reference motion. Although this
method is powerful, the ZMP is not always controlled in a feedback manner. Namely, when the
environment such as the gradient of the ground varies, the planned motion may cause the tumble
and so replanning or modification is sometimes required in order to avoid it. With respect to the
environmental variations, the ZMP trajectory is invariant in the lateral plane of the biped robot, in which
the ZMP moves from the one side to the other and vice versa. From this point of view, we propose a
biped control method for the frontal plane motion based on the ZMP position feedback . It does not
required the reference motion of the upper body and the motion replanning or modification of the
reference motion are free against environmental variation. This method is applied in the in-place
stepping motion and the stability of this method is examined analytically as well as by computer
simulations. Finally, the effectiveness of this method is demonstrated by the robot experiment with
some improvement points.

Index Terms
biped robot, stepping motion, Center of pressure, motion planning, adaptive behavior