Development and Testing of Force-Sensing Forceps Using FBG for Bilateral Micro-Operation System

Regarding the bilateral operation system, the precise force sensing system is necessary to reduce intervening impedance. The force sensing system needs to be unaffected by machine vibration during robot motion because it is difficult to improve force control gain sufficiently due to the noise. Thus, it is desirable to mount a force sensor as close as possible to the contact point to sense applied force directly. Many researchers have studied the microend effector equipped with fiber Bragg grating (FBG) based force sensors. These studies mainly focus on the aspect of the manipulators, and it is required to validate the benefits when combining the FBG-based force sensors into the bilateral control system and driving it. This letter proposes a bilateral micro-operation system equipped with a 4-DOF force/torque sensor using FBG sensors (4D-FBG): mounted near the tip of forceps. 4D-FBG is designed with the following three points to achieve the bilateral micro-operation system: First, low force sensing delay; second, the force sensing is hardly affected by gripping force and temperature change-in case, a gripper is actuated by wire and a sensor mounted between the actuator and the gripper, the actuating force interferes with force sensing structurally in general; and third, the force sensing is hardly affected by machine vibration during robot motion. A bilateral micro-operation system equipped with 4D-FBG is set up and has been tested. The result shows 4D-FBG works well at the above three points, and significantly reduces intervening inertia compared to the conventional force sensing method using the universal force/torque sensor mounted at the base of the end-effector. Furthermore, it is confirmed that lower intervening inertia can reduce the contact force when driving the system.