A collaborative robot is a robot that can work with humans in a shared workspace. It is expected that collaborative robots improve productivity and compensate for the shortage of working population. To make safe contact with the external environment, back-drivability is necessary. For high back-drivability, a robot with a joint torque sensor or a load-side encoder has been developed. Control methods using sensors effectively and improving collaborative robots performance are needed. It is known that disturbance suppression performance can be enhanced by disturbance observer (DOB). Disturbance suppression can make back-drivability higher by eliminating the effect of the contact force. However, a simple DOB cannot improve the disturbance suppression performance for a two-mass system like a robot joint. In this paper, we propose a method to enhance back-drivability significantly by simple filter design considering the structure of a two-mass system. The performance of the proposed method is evaluated by simulation and experiment.

This paper proposes a new torque sensing method, Cr-N alloy strain sensitive thin-film based torque sensors and distributed joint torque servo systems that enable human support robots to have capabilities to make physical interaction in adaptive and safe operation tasks. Stiffer torque sensing with stable and high-resolution sensing to meet practical level of the developed torque sensors have been achieved. We have developed the joint torque control based 4-DOF arm models in order to verify practical effectiveness of the proposed joint torque servo systems. We also demonstrated the joint torque control based bilateral master slave system exploring future applications.

In this paper we propose a new robust force and position control method for property-unknown objects grasping. The proposed control method is capable of selecting the force control or position control, and smooth and quick switching according to the amount of the external force. The proposed method was applied to adaptive grasping by three-fingered hand which has 12 DOF, and the experimental results revealed that the smooth collision process and the stable grasping is realized even if the precise surface position, the mass and the stiffness are unknown. In addition a new algorithm determines the grasp force according to the "slip" measured with the tactile sensor and the viscoelastic media on the fingertip. This algorithm works at starting and stationary state, so the friction and mass unknown object grasping is realized by the effectual force.

SDR-4X II is the latest prototype model which is a small biped entertainment robot. Formerly we reported the outline of SDR-4X II, and mechanical system, control system and sensor system. In this paper we report about analysis of various important motions of this small biped entertainment robot which is used in home environment. Humanoid type robot basically has very small foot area and the standing stability is essentially very low. Therefore we do not try that the robot never falls down, but we have to think that the robot sometimes surely falls down by some reasons. And when it falls down, the robot should not be damaged and stand up by himself. In this paper, we describe the method of falling-over and standing up motions and analyze the measured joint angle data and confirm the successfulness of our measures. The major point of the shock absorbing method is the motion of effective joints and the real-time servo loop gain modification control. Lastly as one of the important motions, the wide-angle turn motion analysis is explained.