The Development of the Preview-Control walking method for a stable bipedal walking of an adult size humanoid robot
- The Development of the Preview-Control walking method for a stable bipedal walking of an adult size humanoid robot
- YITAEK KIM
- Alternative Author(s)
- Jeakweon Han
- Issue Date
- The purpose of this study is to develop a stable bipedal walking method based on preview control for a humanoid robot. In order for a humanoid robot to engage in stable bipedal walking, zero moment point (ZMP) must exist within the support polygon of the robot's feet. In this study, we propose a new ZMP-based walking control method to ensure the ZMP remains in the support polygon when the robot is walking. To realize this, we conducted a kinematics analysis of the humanoid robot, gait algorithm implementation, simulations and experiments with a humanoid robot (named ALICE).
In an experiment, when an online walking pattern generator using the preview control of the ZMP was applied to our robot ALICE, the robot overturned. The causes of this instability problem were identified as follows.
To begin with, because of hardware limitations, the robot was unable to meet the required acceleration and velocity in the center of mass (COM) trajectory according to the square waveform of the reference ZMP. Second, the actual ZMP of the robot did not meet the reference ZMP accurately. In addition, the actual ZMP of the robot was not present in the support polygon during the single stance phase (SSP). In this study, we propose two methods to solve these problems.
The first method is to change the traditional shape of the reference ZMP, which is the input value of the preview controller, from a square wave to a fifth-order polynomial. This reduces the required acceleration and velocity in the center of mass (COM) trajectory based on the square wave form of the reference ZMP, and thus improves the stability of the robot during the act of walking.
The second method is to change the value of the reference ZMP during SSP. We call this method the shifted displacement control of ZMP. With these two methods, preventing the ZMP of the robot from leaving the support polygon is possible, which in turn prevents the robot from overturning. Based on the robot operating system (ROS), the effectiveness of these methods was verified through simulations in Gazebo and experiments performed with ALICE.
Therefore, stable bipedal walking with ALICE was achieved through our modified pattern generation using a preview control of the ZMP.
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- GRADUATE SCHOOL[S](대학원) > INTERDISCIPLINARY ENGINEERING SYSTEMS(융합시스템학과) > Theses (Master)
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