Gravity estimation and compensation of grasped object for bilateral teleoperation

This paper describes a design method of a master-slave system for grasping and manipulation. A human operator directly touches and manipulates the master manipulator while the slave manipulator grasps an object. A bilateral control method is applied for the system. 4ch controller with disturbance observer and workspace observer is adapted to the system. This controller realizes stable contact with the object and accurate transmission of reaction force from it. Human force and reaction force are estimated by reaction force observer without any force sensor. With this bilateral control method, a human operator feels grasping force, manipulating force and gravity of the grasped object. However, gravity interferes with his manipulation of the object when it is too large. Therefore, a method for gravity estimation and compensation of a grasped object is proposed. A human operator doesn´t feel gravity of the object, but feels grasping and manipulating sensation with this method. Simulation and experimental results show the validity of the proposed method