PID position control of 7-DOF three-fingered robotic hand for grasping task

Abstract

This paper presents the tuning of PID control parameters for position feedback control of motor and the position reference design for grasping task by a 7-degree of freedom (DOF) three-fingered robotic hand. The system of the robotic hand consists of DC-motors, magnetic encoder and a motion controller unit. The robotic hand has three fingers where each finger has two joints and two links made of perspective plastic material. The PID tuning is implemented to all six motors that are used to move all joints of the three fingers. Trial and error method is used for tuning the parameter of PID control to improve the transient response performance of the motors. For the position reference design, a set of position data is identified to produce the grasping trajectory for all finger joints. The trajectory for the robotic hand performs two types of finger configuration for grasping two different shapes of household solid objects. Both works were implemented via programming in Motion Manager Application. It has been observed that the robot hand has performed well with the tuned PID parameters by reducing the overshoot, rise time (T <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">r</sub> ), peak time (T <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">p</sub> ), settling time (T <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">s</sub> ) and steady state error (e <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">ss</sub> ). Besides, the robot hand has also succeeded the grasping task with the proposed position reference trajectory.