The Biomechanics of the Tactile Perception of Friction

Description

Humans rely on their sense of touch to perceive subtle movements and micro slippages to manipulate an impressive range of objects. This incredible dexterity relies on fast and unconscious adjustments of the grip force that holds an object strong enough to avoid a catastrophic fall yet gentle enough not to damage it. The Biomechanics of the Tactile Perception of Friction covers how the complex mechanical interaction is perceived by the nervous system to quickly infer the state of the contact for a swift and precise regulation of the grip. The first part focuses on how humans assess friction at the contact initialization and the second part highlights an efficient coding strategy that the nervous system might use to continuously adjust the grip force to keep a constant safety margin before slippage. Taken together, these results reveal how the perception of frictional information is encoded in the deformation of our skin. The findings are useful for designing bio-inspired tactile sensors for robotics or prosthetics and for improving haptic human-machine interactions. Series Editors’ Foreword Preface Acknowledgements Contents Abbreviations 1 Introduction 1.1 Motivations 1.2 Overview References 2 State of the Art 2.1 How Do Humans Interact: Bio-Tribology of Skin 2.1.1 Finger Anatomy 2.1.2 Mechanical Properties of Skin 2.1.3 Frictional Properties of the Skin 2.1.4 Mechanical Models of Skin Tissue 2.2 How Do Humans Encode the Mechanical Deformation: Mechanotransduction 2.2.1 Four Types of Afferents 2.2.2 Summary 2.3 How Do Humans Perceive 2.3.1 Tactile Sensitivity 2.3.2 Slip Detection 2.3.3 Friction Perception 2.4 How Do Humans Manipulate: Human Hand's Action 2.4.1 Action and Perception 2.4.2 Grip Force Control 2.4.3 Passive Versus Active Sensing 2.4.4 Predictive Coding 2.5 Conclusion References 3 Mechanical Model of Skin Deformation 3.1 Introduction 3.2 Finite-Difference Mechanical Model 3.2.1 Dynamic Equation 3.2.2 Sizing of the Model 3.2.3 Contact Modeling 3.3 Results of the Simulation 3.3.1 Static Deformation: Comparison with the Waterbed Model 3.3.2 Ultrasonic Click Caused by Rapid Changes in Friction 3.3.3 Stick-Slip Transition 3.3.4 Bump Exploration 3.4 Discussion 3.5 Conclusion References 4 Mechanics of Friction Perception 4.1 Introduction 4.2 Materials and Methods 4.2.1 Participants and Protocol 4.2.2 Setup 4.2.3 Data Analysis 4.3 Results 4.3.1 Empirical Skin Deformation 4.3.2 Friction Discrimination Performance 4.3.3 Friction Influences Skin Deformation 4.3.4 Skin Deformation and Friction Perception 4.3.5 Influence of the Kinematics of the Exploratory Procedure 4.3.6 Strain Energy and Mechanoreceptors Thresholds 4.3.7 Ideal Observer Analysis 4.4 Predictions from the Mechanical Model 4.5 Discussion 4.6 Conclusion References 5 The Mechanical Basis Encoding Stick-Slip Transition 5.1 Introduction 5.1.1 Encoding of Slippage 5.1.2 Efficient Coding Hypothesis 5.1.3 Rationale Behind Dimensionality Reduction 5.2 Materials and Methods 5.2.1 Data Collection 5.2.2 Dataset of Spatio-Temporal Skin Deformation 5.3 Results 5.3.1 Empirical Strain Patterns 5.3.2 Model Validation 5.3.3 Dimensionality Reduction of the Strain Field 5.3.4 Tactile Encoding Efficiency of the Safety Margin 5.4 Discussion 5.5 Conclusion References 6 Space-Time Fusion of Discrete Tactile Events 6.1 Introduction 6.2 Viscoelastic Model of the Skin 6.2.1 Spatial Stress Distribution 6.2.2 Temporal Attenuation of Strain 6.3 Mechanical Stresses and Strains at the Depth of the Mechanoreceptors 6.3.1 Influence of Friction on Strains During a Simple Press 6.3.2 Evolution of Strains During the Transition from Stick to Slip 6.4 Tactile Persistency 6.4.1 Spatio-Temporal Model 6.4.2 Materials and Methods 6.4.3 Results 6.5 Conclusion References 7 Conclusion 7.1 Summary of the Contributions 7.2 Applications to Robotics 7.3 Future Directions References Appendix A Additional Results of the Friction Perception Experiment A.1 Motivations A.2 Strain Components A.3 Individual Performance Appendix B Skin Strains During Incipient Slippage Appendix C Dimensionality Reduction Technique Reference