Ionic Polymer Metallic Composite Transducers for

Ionic Polymer Metallic Composite Transducers for Biomedical Robotics Applications

Andrew J. McDaid and Kean C. Aw


International Frequency Sensor Association Publishing

Andrew J. McDaid and Kean C. Aw Ionic Polymer Metallic Composite Transducers for Biomedical Robotics Applications

Copyright © 2013 by International Frequency Sensor Association Publishing E-mail (for orders and customer service enquires): [email protected] Visit our Home Page on http://www.sensorsportal.com All rights reserved. This work may not be translated or copied in whole or in part without the written permission of the publisher (International Frequency Sensor Association Publishing, Barcelona, Spain). Neither the authors nor International Frequency Sensor Association Publishing accept any responsibility or liability for loss or damage occasioned to any person or property through using the material, instructions, methods or ideas contained herein, or acting or refraining from acting as a result of such use. The use in this publication of trade names, trademarks, service marks, and similar terms, even if they are not identifies as such, is not to be taken as an expression of opinion as to whether or not they are subject to proprietary rights.

BN-201312YY-XX BIC: TJFD

Acknowledgements I would like to extend my sincere thanks to Prof. Kean Aw, who has been an exceptional mentor to me throughout my PhD research and to this day. His enthusiasm for research has been contagious and I greatly appreciate all the time we spend bouncing ideas during intellectual (and other) discussions. His support and guidance has been incredible. I would like to thank all my colleagues at The University of Auckland who have been there for me whenever I have sought guidance or assistance. Although there are too many to name here, I would however like to make special mentions of Prof. Shane Xie and Prof. Enrico Haemmerle, who have been there throughout my research and studies; their expertise has been much appreciated. To Logan Stuart, for our many discussions and his readiness to give his advice and assistance at any time. Also to my former colleagues, Sean Manley, David Liu, Kaval Patel and Wei Yu, who I worked alongside with to carry out this research. I would like to acknowledge The University of Auckland for the financial support they have provided me with both The University of Auckland Doctoral Scholarship as well as The University of Auckland Undergraduate Scholarship which I have been awarded. Last, but far from least, I would like to thank my big family and all my friends for their continued support and encouragement. I am especially grateful for all the assertive motivation my wife Sarah constantly provides me; this has directed me to produce a piece of research work I am truly proud of, in a timely fashion! To my parents, thank you for instilling in me a desire to learn and excel in everything I do. And for everything else ...

Dr. Andrew McDaid, Auckland, NZ

About the Authors Andrew J. McDaid is a Lecturer (Assistant Professor) in the Department of Mechanical Engineering at The University of Auckland, New Zealand. His main research interests include intelligent mechatronics systems and devices, especially in rehabilitation, biomechatronics, bio-medical and surgical robotics applications. Andrew has application experience in ‘smart’ materials as well as biomedical, rehabilitation and traditional robotics fields. He is working to develop medical devices, using non-traditional sensors and actuators, which are bio-cooperative and work in harmony with the human brain and physical body. Kean C. Aw is an Associate Professor in the Department of Mechanical Engineering at The University of Auckland, New Zealand. His main research interests include micro-systems and deployment of smart/functional materials such as conducting polymers, metallic oxides, etc as sensors and actuators in various applications such as biosensors, medical/rehabilitation robots, micro-pumps, micromanipulators, MEMS, energy harvester, etc.

Contents

Contents

Preface ........................................................................................................... 15 Book Synopsis................................................................................................ 17 1. Introduction............................................................................................... 19 1.1. The Need for New Actuator Technologies........................................... 19 1.2. IPMCs: Fundamentals ........................................................................ 21 1.3. Biomedical Robotics............................................................................ 26 1.4. Objectives and Scope........................................................................... 26 1.4.1. An electro-mechanical Design Based Model of IPMC Actuators....................................................................... 26 1.4.2. Design of IPMC Actuated Biomedical Devices........................... 27 1.4.3. Development of Advanced Control Methods for IPMCs ............. 28 1.4.4. Implementation and Testing of the IPMC Actuated Biomedical Devices ..................................................................... 28 2. State of the Art: IPMC Modeling, Control and Applications ............... 29 2.1. Historic Development.......................................................................... 29 2.2. Modeling.............................................................................................. 31 2.2.1. Black Box Models........................................................................ 31 2.2.2. Physical Models ........................................................................... 31 2.2.3. Grey Box Models ......................................................................... 32 2.3. Control ................................................................................................ 33 2.3.1. Linear Control .............................................................................. 34 2.3.2. Reference Model Based Control .................................................. 34 2.3.3. Nonlinear Control (Non-adaptive) ............................................... 35 2.3.4. Robust Control (Non-adaptive) .................................................... 36 2.3.5. Adaptive Control.......................................................................... 36 2.4. Applications......................................................................................... 37 2.4.1. Biological ..................................................................................... 38 2.4.2. Other IPMC Applications............................................................. 39 2.5. Summary of the State of Art................................................................. 39 9


3. A Comprehensive Scalable Model for the Complete Actuation Response of IPMCs ................................................................................... 41 3.1. Electro-mechanical IPMC Model........................................................ 42 3.1.1. Nonlinear Electric Circuit ............................................................ 45 3.1.2. Electromechanical Coupling Transfer Function........................... 51 3.1.3. Mechanical Beam Model ............................................................. 52 3.2. Parameter Identification and Results .................................................. 56 3.3. Model Validation ................................................................................. 62 4. Bio-inspired Compliant IPMC Stepper Motor....................................... 69 4.1. Stepper Motor Mechanical Design...................................................... 70 4.2. Model Integration and Simulation....................................................... 72 4.3. Experimental Validation...................................................................... 74 4.4. Extension to Many IPMCs................................................................... 75 4.5. Discussion ........................................................................................... 77 5. Iterative Feedback Tuning: Fundamental Theory and Application to IPMCs........................................................................ 79 5.1. Iterative Feedback Tuning Background .............................................. 80 5.2. Motivation for Iterative Feedback Tuning with IPMCs....................... 81 5.3. Formulation of the Iterative Feedback Tuning Algorithm................... 82 5.3.1. Minimizing a Performance Criteria.............................................. 84 5.3.2. Standard Iterative Feedback Tuning algorithm ............................ 87 5.3.3. An Unbiased Gradient Estimate ................................................... 90 5.3.4. Convergence, Stability and Robustness ....................................... 90 5.3.5. Search Direction........................................................................... 92 5.3.6. Update Rate.................................................................................. 92 5.3.7. Issue with the Gradient Experiment ............................................. 93 5.3.8. Extensions to Nonlinear, Time-varying and Multivariable Systems .......................................................... 93 5.4. Iterative Feedback Tuning Implementation on an IPMC ................... 94 5.4.1. Experimental Setup...................................................................... 94 5.4.2. IPMC Control System .................................................................. 95 5.4.3. Iterative Feedback Tuning settings .............................................. 97 5.4.4. Results.......................................................................................... 99 5.5. Discussion ......................................................................................... 100 5.6. Iterative Feedback Tuning Summary................................................. 101 10

Contents 6. Robotic Rotary Finger Joint with Iterative Feedback Tuning Gain Scheduled Control ......................................................................... 103 6.1. Mechanism Design ............................................................................ 105 6.1.1. Extension to Full Hand Exoskeleton/prosthesis......................... 105 6.2. Gain Scheduled Nonlinear Control ................................................... 107 6.2.1. Background ................................................................................ 107 6.2.2. Proposed Gain Scheduled Controller ......................................... 109 6.3. Experimental IPMC Results .............................................................. 110 6.3.1. Tuning for Different Target References ..................................... 111 6.3.2. Development of the Gain Schedule............................................ 113 6.3.3. Comparison of GS Controller with Linear Controller................ 116 6.4. Mechanism Experiments.................................................................... 118 6.5. Discussion ......................................................................................... 120 6.6. Rotary Finger Joint and Iterative Feedback Tuning Gain Scheduled Summary........................................................................... 122 7. Microfluidic Pump with Online IFT Control ....................................... 125 7.1. Micro-pump Application ................................................................... 126 7.1.1. Mechanical Design..................................................................... 127 7.1.2. Modeling and Simulation ........................................................... 128 7.1.3. Prototype .................................................................................... 129 7.1.4. Open-loop Characterization ....................................................... 130 7.2. Control and Tuning of Micropump Actuating Mechanism................ 130 7.2.1. Control System........................................................................... 130 7.2.2. Controller Tuning....................................................................... 131 7.2.2.1. Model Based Tuning........................................................... 133 7.2.2.2. IFT Extension to Online Tuning ......................................... 134 7.2.3. Tuning Comparison in Simulation ............................................. 137 7.2.4. Experimental Tuning.................................................................. 138 7.2.4.1. Experimental Setup............................................................. 138 7.2.4.2. Results................................................................................. 138 7.2.4.2.1. Frequency 0.1 Hz, Amplitude 100 μm ........................ 139 7.2.4.2.2. Frequency 0.1 Hz, Amplitude 300 μm ........................ 139 7.2.4.2.3. Frequency 0.05 Hz, Amplitude 100 μm ...................... 141 7.2.4.2.4. Frequency 0.05 Hz, Amplitude 300 μm ...................... 143 7.3. Experiments with Pump..................................................................... 143 7.4. Discussion ......................................................................................... 145 7.5. Micropump Summary ........................................................................ 147

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8. Cell Microtool/gripper and Micromanipulator with Precise and Robust Control................................................................................ 149 8.1. Single Cell Micromanipulation ......................................................... 151 8.1.1. Current Techniques.................................................................... 151 8.1.2. IPMCs for Micromanipulation................................................... 153 8.2. Micromanipulator System Design ..................................................... 155 8.2.1. Microtool/gripper Design........................................................... 155 8.2.2. Micromanipulator Design .......................................................... 156 8.2.2.1. Specifications for Proposed Manipulator ........................... 156 8.2.2.2. Mechanical Mechanism Design.......................................... 157 8.2.2.3. IPMC Actuators for the Manipulator.................................. 160 8.2.2.4. Manipulator Optimization and Validation.......................... 161 8.2.3. Complete Manipulation System................................................. 165 8.3. Micromanipulation Control .............................................................. 165 8.3.1. 2DOF Control Structure............................................................. 167 8.3.2. Stability...................................................................................... 168 8.3.3. Tuning Procedure....................................................................... 169 8.3.4. IFT for 2DOF Controller ........................................................... 170 8.3.5. Comparison with 1DOF Controller............................................ 172 8.4. Micromanipulator Simulation and Validation .................................. 174 8.4.1. Procedure ................................................................................... 174 8.4.2. Simulated DR Tuning ................................................................ 175 8.4.3. Simulated SP Tuning ................................................................. 175 8.5. Microtool/gripper Experiments and Results...................................... 178 8.5.1. IPMC Actuator and Test Setup .................................................. 178 8.5.2. Procedure ................................................................................... 179 8.5.3. Results........................................................................................ 180 8.5.4. Validation of 2DOF Controller .................................................. 182 8.6. Micromanipulator Experimental Results .......................................... 185 8.6.1. Procedure ................................................................................... 185 8.6.2. DR Tuning ................................................................................. 186 8.6.3. SP Tuning .................................................................................. 188 8.6.4. 1DOF Tuning............................................................................. 191 8.6.5. Comparison of IFT Tuned 2DOF and 1DOF Controllers for Tracking .............................................................................. 192 8.6.6. Range and Accuracy .................................................................. 194 8.6.7. 2 - Axis Tracking Performance .................................................. 195 8.6.8. Tracking Performance with an External Disturbance ................ 196 8.7. Discussion ......................................................................................... 198 8.8. Micromanipulation Summary............................................................ 201

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Contents 9. Force Compliant Surgical Robotic Tool with IPMC Actuator and Integrated Sensing ........................................................................... 203 9.1 Surgical Tool Design.......................................................................... 204 9.1.1. Mechanical Design..................................................................... 204 9.1.2. Mechanical Analysis .................................................................. 206 9.2. Integrated Sensor Design .................................................................. 206 9.3. Characterizing the Cutting Depth Versus Force ............................... 209 9.4. Control Design .................................................................................. 211 9.4.1. Open Loop Modeling ................................................................. 211 9.4.2. Controller Design....................................................................... 212 9.4.3. Force Feedback Control ............................................................. 213 9.4.4. Force Controlled Cutting ........................................................... 214 9.5. Surgical Robotic End Effector Summary........................................... 216 10. Conclusions............................................................................................ 217 10.1. Research Outcomes ......................................................................... 217 10.1.1. New Design Based Model of IPMC Actuators ........................ 217 10.1.2. Design Novel IPMC Biomedical Devices................................ 218 10.1.3. Advanced Control Methods for IPMCs ................................... 219 10.1.4. Implement and Test the Biomedical Devices........................... 219 10.2. Contributions to Current State of the Art ........................................ 219 References.................................................................................................... 221 Index ............................................................................................................ 243

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Preface

Preface Robotic devices have traditionally been developed for industrial applications for tasks which are repetitive, inhospitable and even unachievable by humans. The natural progression then for future robotic devices is to be intelligent so they can work closely with humans in their own environment. This book is written for leading edge engineers and researchers, working with non-traditional or smart material based actuators, to help them develop such real world biomedical applications. Electrical, mechanical, mechatronics and control systems engineers will all benefit from the different techniques described in this book. The book may also serve as a reference for advanced research focused undergraduate and postgraduate students. Specifically, this book describes a cluster of research which aims to not only advance the state of art through scientific progress in a specific smart material actuator, namely IPMC, but also serve as a guideline to demonstrate the techniques in which many more issues around developing future smart material actuators can be solved. Traditionally actuators are well known and understood and so designing mechanical devices is almost trivial, however developing ‘smart’ devices for complex medical applications requires designing from a fundamental standpoint. This research-design-development process is described in this book. To this end, six biomedical device prototypes have been developed, by first creating a new physics based, design oriented model of the IPMC actuators themselves, in order to be able to completely simulate the system and prove the design before committing to implementation. Following from this, new controller algorithms (specific for each application) are developed, which use the fundamental IPMC model coupled with the mechanism dynamics model, in order to control the extremely complex, nonlinear and time-varying IPMC system. Overall, IPMCs (and typically all smart materials) have many advantages over traditional actuators and in my opinion are the key to advancing from the current state of the art to a new level of biocompatible systems which work in harmony with the human body. However, much in-depth research, both fundamental and applied, is 15


needed into the development of such systems to make them viable. Simply selecting an ‘off the shelf’ actuator and designing a system around the chosen actuator, as is done in most current system design, will simply not work. The framework in this book outlines a method of system design, with smart material actuators, in order to develop smart devices which have the potential to improve the health of society in the future, which is what I am really passionate about.

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Book Synopsis

Book Synopsis To start, the background of this research is introduced and the great need for new actuator technologies is discussed. Fundamentals of IPMCs and biomedical robotics are also presented, followed by the objectives and scope of the research published in this book. A thorough survey of the state of art in IPMCs is reported in Chapter 2. This review uncovers the areas of IPMC research which are lacking and hence require further investigation to further knowledge in this field. After this review the contributions of the research in this book are fully justified. Chapter 3 describes the development of a new comprehensive scalable electro-mechanical IPMC model which has been created specifically for designing mechanical systems. This is used as an invaluable tool for the remainder of the research as it is used to evaluate the performance of all the devices before they are implemented as well as for determining a suitable stable starting state for the controller tuning algorithms. A bio-inspired rotary device which replicates the performance of a traditional stepper motor is presented in Chapter 4. First the motor design with open-loop control is simulated using the IPMC model to verify its performance and then experimental validation is presented on the real system. An extension to the motor mechanical design to improve performance is also proposed. The fundamentals and state of the art in iterative feedback tuning is presented in Chapter 5 along with experiments demonstrating the capabilities of the existing iterative feedback tuning algorithm to tune IPMC performance. The iterative feedback tuning approach is the basis for the new closed-loop control system architectures developed and used for the remaining applications. Chapter 6 presents the design and implementation of an artificial muscle actuator driving a rotary joint which is envisaged for use as a prosthetic finger joint or a hand rehabilitation device. As the human finger joint requires large deflections, the IPMC becomes highly 17


nonlinear and as such a gain scheduled (GS) controller tuned with iterative feedback tuning is developed. Experimental results show its superior performance to a linear proportional-integral-derivative (PID) controller. In Chapter 7 an IPMC actuated micropump for dispensing drugs to humans is presented. The micropump has the ability to be embedded into a human. A modification to the iterative feedback tuning algorithm which enables the system to be tuned online is developed to adaptively tune the micropump throughout its operation. Chapter 8 describes a microtool/gripper and micromanipulator. The devices are first designed to meet their required specifications through a thorough design process utilizing the new IPMC model and dynamic mathematical models of the mechanical systems to simulate their performances. New robust controllers, which are adaptively tuned using a modified iterative feedback tuning algorithm, are developed for the devices. The devices are then implemented and experimental results of the entire system to verify its performance are presented. Chapter 9 demonstrates the use of IPMC as a surgical robot end effector. The use of IPMC that is compliant can add safety to delicate surgery. A simple force compliant surgical robotic tool has been implemented and the experiments conducted show promising results for using IPMCs in real world applications. The conclusions and summary of this work are presented in the final chapter.

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