A fusion control of impedance and vibration suppression for a manipulator with flexible base

Accidents caused by a collision between an environment and a robot become a problem, so safety strategies of robots are indispensable. Since the impact force sharply increases at the time of a collision, position-based impedance control which has low responsiveness to the collision can not sufficiently reduce the damage. This paper proposes the manipulator with passive and flexible base for collision force suppression. The proposed flexible base has a rotating structure and it is possible to suppress the collision from any direction when an environment contacts the working manipulator. When a large external force is applied, the variable impedance control according to the strain amount of the base spring in order to avoid the strain limit of flexible base is proposed. Also, when the external force is estimated with force sensorless, the estimation error increases due to the friction model error of the motor, and the position followability deteriorates. Therefore, the contact state is judged by the strain amount of the flexible base, and correction is added to the estimated reaction force, thereby improving the position followability of the impedance control in non-contact.