Two transition phase control methods for hard contact

A hard contact is an impact that occurs when the robot contacts a stiff environment with a high velocity. In the pretransition phase of the hard contact, it is important to maintain stability while reducing succeeding force peaks and the duration time. For these purposes, we propose two control methods. One is a suppression controller that suppresses position rebounds in-between the impact time. The other is a flexible-damped joint with a joint damping controller. The flexible-damped joint is a new joint type designed to increase the hardware damping. It is controlled by a novel controller, called the joint damping controller, to enhance damping. The major advantage of the proposed methods is a guaranteed stability. The performance of the proposed methods is validated via several comparative experiments.