Standing Balance Control Of Humanoid Robots With Passive Ankle Joints

Keeping stability is the fundamental ability for humanoid robots when work in the real environment. Robots will not work properly or even fall down if they are unable to restore their balance when suffered external disturbances. There are many researches on balance control for humanoid robot, such as standing balance control and stepping balance control. But when some actuators broke down, balance control will be a serious security problem for humanoid robots especially outside.In this paper, we study the robots how to maintain standing balance control on the humanoid robot platform KONG. We research the coordination movement of the hip and arm joints under external disturbance force when ankle joints are broken and can’t work normally. The main research contents include the following parts:1. Using multi-link model to build the dynamics model of humanoid robots. Because the multi-link model considers the mass distribution of the whole robot body, it can represent the dynamic characteristics more accurately. By using the least square estimation method to identify some unknown parameters of the robot, the paper can obtain the control law more accurately and the system will have better robustness.2. Using Lagrange mechanics equation to build dynamic equation for the system and using LQR and fuzzy control methods to realize balance recovery for the robots under external force. The paper transforms the Lagrange mechanics equation to replace the torque input variable by acceleration input variable, so that we can establish state equation for position controlled robot. The paper uses the linear and nonlinear control methods to restore balance control for robots respectively and verifies the methods by experiments on laboratory humanoid robot platforms.3. Designing a controller for passive damped ankle joints. The paper designs an integral controller for passive variable damping coefficients ankles. The controller can not only simulate passive damped characteristics of broken ankles but also simulate different damping coefficients for passive ankles by adjusting the control parameters. By conducting experiments under different damping coefficients of ankle joints, we can know the balance recovery characteristics of the passive ankle joints humanoid robot with different mechanical structure.