Contents
1 Introduction 17
2 Smart Materials 21
2.1 Introduction . . . 21
2.1.1 State-of-the-art . . . 21
2.1.2 Phenomenology of Rheological Fluids . . . 23
2.1.3 ERFs and MRFs: Applicability to Haptic Interfaces . . . 26
3 1D and 2D Haptic Interfaces based on MRFs 29 3.1 Introduction . . . 29
3.2 Design Criteria . . . 32
3.3 The Pinch Grasp (PG) display . . . 33
3.4 The Haptic Black Box (HBB) display . . . 35
3.4.1 Mechanical design and equipments . . . 36
3.4.2 Energization of the HBB-I . . . 39
3.4.3 Hardware and Software arrangements . . . 40
4 Electromagnetic analysis of MRF-based displays 43 4.1 Introduction . . . 43
4.1.1 The inverse magnetic problem . . . 44
4.2 FEM analysis . . . 46
CONTENTS
4.2.1 Field formulation: 3D Finite Elements Method (FEM) principle 47
4.3 FEM analysis and optimization of the PG display . . . 49
4.3.1 Final PG hardware equipments . . . 50
4.4 FEM analysis of the HBB-I display . . . 53
4.5 From the HBB-I to HBB-II . . . 56
4.5.1 Design criteria . . . 56
4.5.2 Possible new design of HBB display . . . 58
4.5.3 Energization of the new HBB system . . . 61
4.5.4 The advanced FEM simulated model . . . 63
4.5.5 Main simulations results . . . 65
5 3D HBB-II for free-hand exploration 75 5.1 Introduction . . . 75
5.2 Detailed description of the HBB-II . . . 77
5.2.1 FEM analysis of the HBB-II . . . 80
5.2.2 Working procedure . . . 81
6 Interaction with the hand 87 6.1 Introduction . . . 87
6.1.1 Problem description and solutions . . . 87
6.2 The proposed solution . . . 93
6.2.1 The simulation results . . . 94
6.2.2 Discussion . . . 94
6.3 Risk analysis of MRF in VE . . . 98
6.3.1 Risks in the technological developments . . . 98
6.3.2 Safety analysis . . . 102
7 Experimental Characterization of MRF displays 105 7.1 Introduction . . . 105
7.2 MRF: model resolution and identification . . . 107
7.2.1 Parameters determination . . . 110
7.2.2 Test on Biological Tissues . . . 112
8 Psychophysical Experiments 119 8.1 Introduction . . . 119
8.2 Qualitative analysis on HBB-I . . . 119
8.2.1 Position recognition . . . 119
8.2.2 Shape recognition and orientation detection . . . 121
8.2.3 Free shape recognition and orientation detection . . . 122
8.3 Quantitative analysis: comparison between HBB-I and PG displays . 125 8.3.1 Compliance recognition . . . 125
8.3.2 Just Noticeable Difference (JND) . . . 127
8.3.3 Psychometric function . . . 130
8.4 Improvements of the HBB-II . . . 132
8.4.1 Discussion . . . 135
9 Conclusion 137
CONTENTS
List of Figures
2.1 Simplified rheology formulation of controllable fluids. . . 24 2.2 Rheological behaviour of controllable fluids non excited (left - like
Newtonian model) or excited (right - like Bingham plastic model). . 25 2.3 Phenomenology of MRFs: Internal configuration in the absence of
the magnetic field (on the left), in intermediate configuration (middle figure) and with a strong magnetic field applied (on the right). . . . 26 2.4 Magnetic and rheological properties of MRF132LD. . . 28
3.1 A possible field of application of the MRF-based haptic interface in MIS or OS where the MRF reproduces the VE in tactile domain. . . 31 3.2 Magnetization curve: setup (left) and material under testing (right). 33 3.3 Magnetization curve: results for AISI 1015 (left) and MRF 132 LD
(right). . . 34 3.4 Design of the Pinch Grasp (PG) display. . . 34 3.5 Pinch Grasp (PG) display: magnetic core without (left) and with
(right) coils. . . 35 3.6 Haptic Black Box (HBB) concept. . . 36 3.7 Basic idea of the immersive scheme HBB arranged by using horizon-
tal solenoids architecture (left) and mechanical design (right). . . 37
LIST OF FIGURES
3.8 HBB-I: simulation (left) and prototype (right) arranged by using hor-
izontal solenoids during a tactile task. . . 38
3.9 HBB-I: design (left) and prototype (right) arranged by using vertical solenoids during a tactile task. . . 38
3.10 Coil and its design for HBB-I. . . 40
3.11 The prototypal demonstrator HBB-I display. . . 42
4.1 FEMM Analysis process . . . 48
4.2 Simulation of the Pinch Grasp (PG) display. . . 50
4.3 Experimental Setup on the Pinch Grasp (PG) display. . . 51
4.4 Model and optimization of the Pinch Grasp (PG) display. . . 51
4.5 Preliminary HBB-I prototype. . . 53
4.6 The whole FE model (left) and 14of the FE model (right) of the HBB-I. 54 4.7 Flux density B in the system (left) and profile of B along two different line (right) in air. . . 56
4.8 Flux density B in the system with MRF (left) and profile of B along two different line with MRF (right). . . 57
4.9 The modified HBB device (left) and profile of B along two different lines (right). . . 58
4.10 Schematic representation of a possible new HBB device. . . 59
4.11 The main dimensions of the new system HBB in cm. . . 60
4.12 Schematic representation of the new HBB device without coils. . . . 61
4.13 Particular of the A − A0 part during the energization. . . 62
4.14 The equivalent magnetic circuit of new HBB design. . . 63
4.15 Plastic box for MRF-based displays with a latex glove. . . 64
4.16 3D view of the simulated device (left) and a cut inside the system (right). . . 65
4.17 Perspective view of the pistons distribution. . . 66
4.18 The device with a ferromagnetic sheet. . . 67
4.19 1/8 of the FEM model of the device. . . . 68
4.20 Particular of the pistons with the conic shape head. . . 69
4.21 Flux density in the fluid at z = 0, without ferromagnetic sheet. . . . 69
4.22 Flux density in the fluid at z = 0, with ferromagnetic sheet. . . . 70
4.23 Vector B in the whole space occupied by the device. . . . 70
4.24 The operation of ferromagnetic sheet. . . 71
4.25 Flux density in the fluid at z = 0, with ferromagnetic sheet and with the hand inside it. . . 71
4.26 Vector B in the volume near the fluid in presence of the ferromagnetic sheet and of the hand. . . 72
4.27 Flux density in the fluid at z = 0 with 3 active pistons. . . . 72
4.28 Architecture of a new design of HBB. . . 73
4.29 Symmmetry of the new design of HBB. . . 73
4.30 Simulation of the new design of HBB. . . 74
5.1 Haptic Black Box I (HBB-I) prototype during experimental session. 76 5.2 Architecture of the new HBB-II device without coils. . . 77
5.3 Mechanical design of the HBB2 with coils. . . 78
5.4 FEM modeling and partial representation of HBB-II display. . . 79
5.5 Numerical simulation of HBB-II display: flux density in a generic plane of the fluid when 2 pistons operate. . . 81
5.6 Numerical simulation of HBB-II display: flux density at the middle plane of the fluid when 2 opposite pistons operate. . . 82
5.7 MRF energization principle of HBB-II: particular of pistons mechanism. 83 5.8 Particular of secondary-coils system equipped with auxiliary system. 84 5.9 Numerical simulation of HBB-II display: flux density at the base of the fluid when the central vertical piston operate. . . 84
5.10 Numerical simulation of HBB-II display: flux density at the middle plane of the fluid when all the pistons of the plane operate. . . 85
LIST OF FIGURES
5.11 HBB-II: Visual C++ GUI screenshot. . . 85 5.12 HBB-II: picture of the final prototype. . . 86
6.1 Induction B along x-direction when an object with different magnetic permeability is inserted in the fluid. . . 88 6.2 Induction B along z-direction when an object with different magnetic
permeability is inserted in the fluid. . . 89 6.3 Model of PG display with two fingers inserted inside the fluid. . . 89 6.4 Model of PG display with one finger inserted inside the fluid. . . 90 6.5 Induction B along x-direction when two fingers are inserted in the
fluid. . . 90 6.6 Induction B along z-direction when two fingers are inserted in the
fluid. . . 91 6.7 Induction B along x-direction when two fingers are inserted in the
fluid. . . 92 6.8 Induction B along z-direction when two fingers are inserted in the
fluid. . . 92 6.9 2D model of the system used to characterize the magnetic permeabil-
ity of the auxiliary material. . . 93 6.10 Induction B along x-direction when a finger covered with a material
of different magnetic permeability is inserted in the fluid (see model in fig.6.4). . . 95 6.11 Induction B along z-direction when a finger covered with a material
of different magnetic permeability is inserted in the fluid (see model in fig.6.4). . . 95 6.12 Induction B along x-direction when two fingers covered with a mate-
rial of magnetic permeability=10 are inserted in the fluid (see model in fig.6.3). . . 96
6.13 Induction B along y-direction when two fingers covered with a mate- rial of magnetic permeability=10 are inserted in the fluid (see model in fig.6.3). . . 96 6.14 Induction B along z-direction when two fingers covered with a mate-
rial of magnetic permeability=10 are inserted in the fluid (see model in fig.6.3). . . 97 6.15 Magnetic field maps inside the fluid when two fingers covered with a
material of magnetic permeability=10 are inserted in the fluid. . . . 97 6.16 Three-dimensional excitation with different values of field. . . 101 6.17 Rheological properties vs applied field. . . 101
7.1 Experimental apparatus used to identify the MRF. . . 107 7.2 MRF response to stepwise strain of 10% for increasing magnetic field
up to saturation phenomenon. . . 108 7.3 Final generalized Kelvin model. . . 109 7.4 An example of the response of MRF submitted to a stepwise strain
and a given magnetic field suitably fitted with an exponential inter- polation. . . 112 7.5 The haptic device for Pinch Grasp manipulation during the psy-
chophysical session in a manipulation task. . . 113 7.6 Comparison between stress relaxation curves of biological tissues,
spleen, and MRF specimen. . . 115 7.7 Comparison between stress relaxation curves of biological tissues,
brain, and MRF specimen. . . 116 7.8 Comparison between stress relaxation curves of biological tissues,
liver, and MRF specimen. . . 117
LIST OF FIGURES
8.1 Psychophysical experimental setup: top-view of the HBB-I workspace with alphanumeric coordinates of 16 quantized points (left) and real
activation of one point having coordinate B2 (right). . . 120
8.2 Psychophysical experimental setup: set of solenoids activated in or- der to reproduce different shapes in HBB-I workspace: square (left) and triangle (right). . . 122
8.3 Psychophysical experimental setup: pie charts showing the percent- age of shapes recognized by volunteers when four contiguous solenoids (left) and three contiguous (not aligned) solenoids (right) are activated.123 8.4 Psychophysical experimental setup: Set of figures from which sub- jects could chose the perceived shape differently oriented during the tactile manipulation of the MRF. . . 124
8.5 Picture of the prototype during the simulation of a virtual object belonging the set reported in fig.8.4. . . 124
8.6 Experimental Setup: training on 4 specimens. . . 126
8.7 Experimental Setup: softness blind recognition (a) and (b). . . 126
8.8 Experimental setup: HBB-I softness recognition. . . 126
8.9 Compliance estimation: percentage of successful recognition on 6 virtual objects for HBB-I display, PG display and direct exploration. 127 8.10 Just noticeable difference versus stimulus intensity for HBB-I and Pinch Grasp displays. Standard deviation relative to average value is reported as well. . . 129
8.11 Psychometric Function of HBB-I and PG displays: level S is the referenced stimulus and X is the value of electric current stimulus to be compared. . . 130
8.12 Prototype HBB-II during the experimental setup. . . 133
8.13 Simulation of a cylinder shape with the HBB-II display when 2 op- posite pistons operate. . . 134
