UNIVERSITI TEKNOLOGI MARA
TWO-AXIS POSITION-BASED IMPEDANCE CONTROL OF A 2-DOF
ROBOTIC FINGER
KHAIRUNNISA BINTI NASIR
Thesis submitted in fulfillment of the requirements for the degree of
Master of Science
Faculty of Electrical Engineering
July 2017
CONFIRMATION BY PANEL OF EXAMINERS
I certify that a panel of examiners has met on the 18th May 2017 to conduct the final examination of Khairunnisa binti Nasir on her Master of Science thesis entitled "Two- axis Position-based Impedance Cotrol of A 2-DOF Robotic Finger in accordance with Universiti Teknologi MARA Act 1976 (Akta 173). The Panel of Examiners recommends that the student be awarded the relevant degree. The Panel of Examiners was as follows:
Azita Laily Yusof, PhD Associate Professor
Faculty of Electrical Engineering Universiti Teknologi MARA (Chairman)
Mohd Hezri Fazalul Rahiman, PhD Associate Professor
Faculty of Electrical Engineering Universiti Teknologi MARA (Internal Examiner)
Norsinnira Zainul Azlan, PhD Assistant Professor
Department of Mechatronics
International Islamic University Malaysia (External Examiner)
PROF. SR. DR. HAJI ABDUL HADI HAJI NAWAWI
Dean
Institute of Graduates Studies Universiti Teknologi MARA Date :24th July, 2017
AUTHOR'S DECLARATION
I declare that the work in this thesis was carried out in accordance with the regulations of Universiti Teknologi MARA. It is original and is the results of my own work, unless otherwise indicated or acknowledged as referenced work. This thesis has not been submitted to any other academic institution or non-academic institution for any degree or qualification.
I, hereby, acknowledge that I have been supplied with the Academic Rules and Regulations for Post Graduate, Universiti Teknologi MARA, regulating the conduct of my study and research.
Name of Student Student I.D. No.
Programme Faculty Thesis
Signature of Student Date
Khairunnisa binti Nasir 2014464044
Master of Science (Electrical Engineering) - EE 750 Electrical Engineering
Two-axis Position-based Impedance Control of A 2-DOF Robotic Finger
July 2017
iii
ABSTRACT
In a previous work, a functional prototype of a custom three-fingered robotic hand has been successfully developed and verified for a grasping task using PID position control alone. However, it was very rigid in its motion which made it prone to damage when dealing with hard surface or when receiving external force from the environment. Thus, this study introduced the design of an impedance type of force control that considers the dynamic of the robotic rigorously to improve its current grasping capability by enabling the sense of touch which could produce softness like human hand to the robotic finger. As the preparation to enable the position-based impedance control development in two individual directions namely x-axis and z-axis, a calibration was done to the fabricated fingertip in both axes to produce a reference for converting the measured signal voltage (V) to the equivalent force value in Newton (N) for the two embedded force sensors inside the fingertip. The position- based impedance control algorithm was designed by regulating the mechanical impedance of the robotic finger based on force measurements from the two embedded force sensors. The proposed position-based control was implemented sequentially with an existing PID position control through robot's kinematics. Initially, direct kinematics was derived for generating the targeted position within the finger's reachability range to the position-based impedance control. Inverse kinematics was also derived to convert the modified position resulted from the position-based impedance control into angle references for actuation of DC-micro motors located at each joint of the robotic finger. The proposed position-based impedance control and the developed kinematics were programmed using Matlab Simulink and tested in real- time experiments. The validation result has proven that the proposed position-based impedance control could modify the initial fingertip position according to the amount and direction of the applied external force, thus produced softness to the robotic finger.
TABLE OF CONTENTS
Page
CONFIRMATION BY PANEL OF EXAMINERS ii
AUTHOR'S DECLARATION iii
ABSTRACT iv ACKNOWLEDGEMENTS v
TABLE OF CONTENTS vi LIST OF TABLES ix LIST OF FIGURES x LIST OF SYMBOLS xii LIST OF ABBREVIATIONS xiii
CHAPTER ONE: INTRODUCTION 1
1.1 Research Background 1 1.2 Problem Statement 3 1.3 Research Objectives 4 1.4 Scope and Limitation of Study 5
1.5 Significance of the Study 6
1.6 Thesis Outline 7
CHAPTER TWO: LITERATURE REVIEW 8
2.1 Overview of Robot Hand Study 8
2.2 Force Control 9 2.3 Importance of Calibration 12
2.4 Robot Kinematics 13 2.5 Chapter Summary 14
CHAPTER THREE: ROBOTIC HAND SYSTEM AND IMPEDANCE
CONTROL 16
3.1 Previous Works 16 3.2 Three-fingered Robotic Hand System 17
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