Motion Planning of Emergency Stop for Humanoid Robot by State Space Approach

Abstract

Abstract-A motion planner of emergency stop must make an operating humanoid robot to a stationary state under the emergency signal. It plays an important role in prevention of falling over because humanoid robots fall over easily. Immediately after the emergency signal, it must generate the emergency stop motion in real-time. We modeled a humanoid robot as a simple dynamic system consists of ZMP (Zero-Moment Point) and COG (Center of Gravity) as its states. The emergency stop motion is generated by a state feedback. We determined optimal feedback gains in terms of the initial conditions and the pole assignment. The proposed method realized a reliable emergency stop with low computational cost. Furthermore, it can easily predict the possibility of the successful emergency stop at any time. The validity of the proposed method is confirmed by an experiment using humanoid robot HRP-2.

Stability Controller on the Atlas Robot Example

“…Works, that addressed the balance control in response to unexpected disturbances from the environment, tackled such tasks as: keeping upright posture on a changing slope [6], keeping balance on unstable ground [1], walking on uneven terrain [13], maintaining balance when an obstacle appears suddenly in front of the robot [14,16,22]. The main task of [4].…”

Experimental evaluation of a trajectory/force tracking controller for a humanoid robot cleaning a vertical surface

“…Recently, the focus is gradually shifting toward problems related to whole body motion generation and control. Various classes of tasks have been tackled, such as pushing motion tasks [2], [3], [4], lifting/carrying heavy objects [5], cooperative carrying of objects with a human [6] and response to unexpected external forces [7]- [11].…”

Falling avoidance of biped robot using state classification

“…They detect a state of the biped robot from the sensory input and select a action to prevent falling or reduce a damage when a biped robot is fallen. A emergency stop method for walking humanoid is suggested by Morisawa et al [6], [7]. It models a biped robot as a simple dynamic system that has states in terms of a ZMP and a COG.…”