A Low Cost Linear Force Feedback Control System for a Two-fingered Parallel Configuration Gripper

This paper presents a simple linear control based force feedback for the gripper of a SCORBOT ER-4u robotic arm. The SCORBOT ER-4u is a 5 degree of freedom (DOF) dexterous robotic arm with a rigid 2-fingered parallel configuration gripper. A Flexi-Force Force Sensitive Resistor (FSR) is attached to one of the claws of the gripper and interfaced to a notebook computer using Arduino Uno microcontroller. The force sensor aids the robotic arm in three different ways: one, senses if an object has been successfully grasped, second determine the coefficient of friction of the object, and third prevent damage when the object will be grasped. The gripper along with the force sensor is calibrated prior to grasping objects. During calibration, samples of the object to be manipulated are used to establish the extents of the gripper on the basis of its grasping force. By following calibration pattern, the gripper is able to grasp objects with approximately the same coefficient of friction. Most importantly, it ensures that the object to be grasped is not damaged by applying sufficient amount of force based on the object's weight. The experimental analyses of the proposed work have shown interesting results to control both the SCORBOT ER-4u robotic arm and the force sensor for grasping masses, strictly conforming to the safety margin of the object.