An experimental study for grasping and pinching controls for an underactuated robotic finger using a PID controller

Abstract

The empirical position control of an underactuated robotic finger is presented in this study. A proportional integral derivative (PID) control system for a robotic finger was introduced to control grasping of cylindrical objects with sizes in the range 30 to 60 mm, as well to control pinching for a range of objects. The robotic finger was made of two four-bar linkages connected in series. The second finger phalanx was modified by adding a DC motor at the coupler link of the second four-bar linkage so that the length could be varied to achieve a similar configuration to human fingers throughout the grasping and pinching operations. The maximum length was used for the grasping configuration, while the minimum length was used for the pinching configuration. The main objective of the proposed control process was to control grasping and pinching for different objects precisely enough to avoid both slipping and damage. An Arduino Mega 2560 was used to control the position of the DC motor movement to reach a predefined position for each specified object. The PID parameters were chosen empirically based on past experience and on repeated experiments, refined through trial and error. The proposed PID controller gave appropriate responses for the control system because of the proper choice of controller parameters