Optical Fiber Sensors for the Next Generation of Rehabilitation Robotics

Preface ix Part I Introduction to soft robotics and rehabilitation systems 1. Introduction and overview of wearable technologies 1.1 Motivation 3 1.2 Wearable robotics and assistive devices 10 1.3 Wearable sensors and monitoring devices 14 1.4 Outline of the book 18 References 21 2. Soft wearable robots 2.1 Soft robots: definitions and (bio)medical applications 27 2.2 Soft robots for rehabilitation and functional compensation 30 2.3 Human-in-the-loop design of soft structures and healthcare systems 34 2.3.1 Human-in-the-loop systems 34 2.3.2 Human-in-the-loop applications and current trends 37 2.3.3 Human-in-the-loop design in soft wearable robots 39 2.4 Current trends and future approaches in wearable soft robots 43 References 46 3. Gait analysis: overview, trends, and challenges 3.1 Human gait 53 3.2 Gait cycle: definitions and phases 56 3.2.1 Kinematics and dynamics of human gait 57 3.3 Gait analysis systems: fixed systems and wearable sensors 58 References 61 Part II Introduction to optical fiber sensing 4. Optical fiber fundaments and overview 4.1 Historical perspective 67 4.2 Light propagation in optical waveguides 69 4.3 Optical fiber properties and types 72 4.4 Passive and active components in optical fiber systems 76 4.4.1 Light sources 77 4.4.2 Photodetectors 77 4.4.3 Optical couplers 79 4.4.4 Optical circulators 80 4.4.5 Spectrometers and optical spectrum analyzers 81 4.5 Optical fiber fabrication and connection methods 83 4.5.1 Fabrication methods 84 4.5.2 Optical fiber connectorization approaches 87 References 89 5. Optical fiber materials 5.1 Optically transparent materials 93 5.2 Viscoelasticity overview 96 5.3 Dynamic mechanical analysis in polymer optical fibers 101 5.3.1 DMA on PMMA solid core POF 103 5.3.2 Dynamic characterization of CYTOP fibers 107 5.4 Influence of optical fiber treatments on polymer properties 111 References 115 6. Optical fiber sensing technologies 6.1 Intensity variation sensors 119 6.1.1 Macrobending sensors 120 6.1.2 Light coupling-based sensors 125 6.1.3 Multiplexed intensity variation sensors 127 6.2 Interferometers 129 6.3 Gratings-based sensors 133 6.4 Compensation techniques and cross-sensitivity mitigation in optical fiber sensors 138 References 143 Part III Optical fiber sensors in rehabilitation systems 7. Wearable robots instrumentation 7.1 Optical fiber sensors on exoskeleton's instrumentation 151 7.2 Exoskeleton's angle assessment applications with intensity variation sensors 152 7.2.1 Case study: active lower limb orthosis for rehabilitation (ALLOR) 156 7.2.2 Case study: modular exoskeleton 157 7.3 Human-robot interaction forces assessment with Fiber Bragg Gratings 160 7.4 Interaction forces and microclimate assessment with intensity variation sensors 166 References 172 8. Smart structures and textiles for gait analysis 8.1 Optical fiber sensors for kinematic parameters assessment 175 8.1.1 Intensity variation-based sensors for joint angle assessment 175 8.1.2 Fiber Bragg gratings sensors with tunable filter interrogation for joint angle assessment 178 8.2 Instrumented insole for plantar pressure distribution and ground reaction forces evaluation 183 8.2.1 Fiber Bragg grating insoles 183 8.2.2 Multiplexed intensity variation-based sensors for smart insoles 188 8.3 Spatiotemporal parameters estimation using integrated optical fiber sensors 198 References 199 9. Soft robotics and compliant actuators instrumentation 9.1 Series elastic actuators instrumentation 201 9.1.1 Torque measurement with intensity variation sensors 202 9.1.2 Torque measurement with intensity variation sensors 206 9.2 Tendon-driven actuators instrumentation 212 9.2.1 Artificial tendon instrumentation with highly flexible optical fibers 213 References 217 Part IV Case studies and additional applications 10. Wearable multifunctional smart textiles 10.1 Optical fiber embedded-textiles for physiological parameters monitoring 223 10.1.1 Breath and heart rates monitoring 224 10.1.