Joe Samosky (for being amazed with tlle \vork) and Rachel Oppenlleimer of Dr. .... 3-7 Examples of force sensor designs: (a) micro-machined piezo-rcsistjve.
Minimally Invasive Instrument for In Vivo Measurement of Solid Organ Mechanical Impedance by
Mark Peter Ottensmeyer B.Eng.Mgt Mechanical Engineering McMaster University, 1994 M.S. Mechanical Engineering Massachusetts Institute of Technology, 1996
Submitted to the Department of Mechanical Engineering in partial fulfillment of the requirements for the degree of Doctor of Philosophy in Mechanical Engineering
at the
MASSACHUSETTS INSTITUTE OF TECHNOLOGY ARCHIVES }iebruary 2001
©
Massachusetts Institute of Technology 2001. All rights r
A5
usmSfNSTITUTE
OF TECHNOLOGY
[ JUL 1 6 2001 LIBRARIES
Author .... ~.~ .....~_. -~'~"IO~."""""""""'.""""'" Department of MechaIlical Engineering January 11, 2001 Certified by
. Dr.
J. Kenneth Salis'hUry, Thesis Supervisor
Principal Research Scientis~hanicalEngineering, MIT Professor, Departments of CoIl]lJ1r~~~'I!eJ Surgery, Stanford Accepted by
,
Prof. Ain A.. Sonin Chair:man, Committee on Graduate Students
1
MinilTIally Invasive Instrument for In Vivo Measurement of Solid Organ Mechanical Impedance by
Mark Peter Ottensmeyer Submitted to the Department of Mechanical Engineering on January 11, 2001, in partial fulfillment of the requirements for the degree of Doctor of Philosophy in Mechanical Engineering
Abstract The medical field, and surgeons in particular, are turning to engineers to develop systems that help them learn their craft better. Marlnequin-based systenlS, animal labs and surgery on cadavers each have dra\rvbacks that could be addressed through realistic computer-based surgical simulatioIl systenls. To generate a silllulation tllat includes both tactile/haptic and visual feedback, one must know what tIle material properties of tissue are, so that a finite elelnellt or other model can generate the proper predictions for interactions bet\veen surgical iIlstruments and tissue. This thesis presents the design, constructioll, characterization, and use of a nlinimally invasive surgical iIlstrument designed to measure the linear visco-elastic properties of solid organs. The Tissue Material Property Sampling Tool, or TeMPeST I-D, applies a small amplitude vibration normal to the surface of an organ such as liver or spleen, and records the applied force and displacement. It has a range of motion of up to Imm, and can apply up to 300mN force with a 5mm right circular indenter. The open loop band\rvidth of the systenl is approximately 100Hz, \vhich is greater than the band\vidth of both the human visual and motor control systems. The relationships bet\Veerl indentation force and displacement and material properties such as the elastic modulus of tissue are presented, and rrlodels are developed that show the expected response to a standard tissue model. Characterization and calibration tests demonstrate the response of the prototype components. Experinlents perforrned on spring and mass elenlents and on silicone gel samples, \vhich lnimic tissue respOIlse, sho,v that the Tel\JIPeST I-D can accurately measure tlleir force-displacelTlent rcspOIlses. The TeJ\!IPeST I-D and its data acqllisition systen1 are intended to be portal)le, to be easil~y transported to and used in an operating room. The systerll ,vas used in proof-of-concept experiments perforIlled on live pigs; an exaInple of the measured properties of porcine liver is presented. The TeMPeST I-D is tIle first in a series of illstrunlents that \viII be developed to support the generation of a comprehensiYe atlas of tissue material properties.
Thesis Supervisor: Dr. J. Kenneth Salisbury Title: Principal Research Scientist, Mechanical Engineering, MIT Professor, Departments of Computer Science and Surgery, Stanford
Thesis Committee: Dr. .1. Kenneth Salisbury, Chairperson Principal Research Sticntist, :Nlechanical Engineering, MIT Professor, Departments of Computer Science and Surgery, Stanford Dr. Mandayam A. Srinivasan Principal Research Scientist, Department of Mechanical Engineering, rv1IT Dr. David L. Trumper Associate Professor of Mechanical Engineering, MIT
Acknowledgments This 'York ,vas supported in part by: tIle Center for Inllovative NIininlall:r Invasive Therapy (CIMIT) at 11assachusetts General Hospital (l\1GH), \vith funding from the Department of tIle ..t\.rmy, under
COll--
tract number DAivlD12-99-2-9001. TIle vie\vs and opinions expressed do not necessarily reflect the position or the policy of the government, and no official endorsement should be inferred;
a National Scierlce and EIlgineering Research Council (NSERC) of Canada PGS-B scholarship.
There are probal)ly more people
thall
I can say
\VI10
have helped me to complete
tllis \vork and keep nle on track. In particular, I'd like to thank: Iny committee members, Prof.
I(en Salisbllry, Dr.
rv1anda~yam
SriIli'vasan and
Prof. Dave Trllnlper, for their support, advice, and good icleas, and especiall.y for helping to defille a realistic scope for this research; Dr. Karen tv'Ioodie, Prof. Joe Rosen and Dr. \rVilliam Laycock of Dartnlollth rvledical School anel Onux IVledical, Inc. for their assistance in gaining access to the Dartmouth Anilnal Resources Center pigs; alld !(aren agaiIl (especially for llelp \vith the papervvork), Greg Burke an(l Sam WeinsteiIl for taking care of the pigs ,vhile
IllY
data "vas being acquired; Joe Samosky (for being amazed with tlle \vork) and Rachel Oppenlleimer of Dr. l\JIartha Gray's cartilage 1)ion1echanics and irnaging laboratory at the Harvard Institutes of lvledicine, for assistance in measllring the properties of my standard materials; Dr. Robert Howe of Harvard University anel Dr. Parris vVellmall for the idea for and data on the silicone gel that I useel as a prelude to real tissue;
Professors Chris Scott anel
:\JlnC
IvI ayes , and You-Yean v\TO ll , of the
D~partIrlcnt
of IvlateriaJ Science and Engineering, for !)roviclillg access to their rnaterials testing apparatus and help in measuring the properties of the standard gels; Dr.
David Schloerb for assistance with the MIT Laboratory for HUIllan and
Machine Haptics tactile stirnulator.
Dr. Steven Dawson and Dr. Stephane Cotin of the Simulation Group of CIMIT at MGH for their support and interest tilfOUghout tIle research, and CIMIT fOf the funding that supported it; Ela, Jesse, Arrin, Andrew and Brian and the other Haptics Lab members who've passed through and made the stay more enjoyable - movie night
an~yone?
Ron Wiken of the i\rtificial Intelligence Lab, for advice, assistance, and keeping the shop facilities in such great shape - it's been a joy to l)uild stuff here; all of the other people \vhose paths I've crossed a!ld have hell)ed me get just that much farther; arId last, bllt certainly not least, my parents, Peter and Erika, my sisters, Susan and Andrea, and my girlfriend, Rene, \vho have seen me through the last
fOUf
half years with love and understanding - I'm finally done!
~'O
frabjolls day! Callooh! Callay!"
He chortled in his joy. Lewis Carroll, J abber\vocky
and a
Contents
1
Introduction
21
2
Background
29
2.1
Basics of visco-elastic behavior. .
30
2.2
Geometric Effects . . . . . . . . .
35
2.2.1
38
Semi-infinite body approximation
42
2.3
Tissue prOI)erty revie\v . .
.
2.4
Tissue property measurement techniques
44
2.4.1
Non-invasive tissue property measurement techniques
44
2.4.2
Invasive tissue property measuremellt techniques.
47
3 TeMPeST I-D 3.1
53
Design COllsiderations for minimally invasive linear property measurement
3.2
3.3
54
.
Actuator options: linear actuators . .
56
3.2.1
Voice coil actuators and solenoids
56
3.2.2
Piezo-electric actuators ..
58
Position sensor optiOllS .
59
3.3.1
Optical encoders
60
3.3.2
Laser interferometry
60
3.3.3
Linear variable differential transformers (IJVDTs)
62
3.4
Force sensor options
3.5
System layout options
62
..
..... 7
64
3.6
4
66
3.6.1
Voice coil and suspension design.
69
3.6.2
LVDT . . . .
74
3.6.3
Force senser
75
3.6.4
TeMPeS'I' I-D electronics
75
3.6.5
Flexible arm and fine positioning cam .
80
System modeling and characterization
83
4.1
TeNIPeST I-D System Modeling.
83
4.1.1
Voice coil actuator model
84
4.1.2
Tissue contact I . . . . . .
84
4.1.3
TeMPeST 1-D in free motion
88
4.1.4
Tissue contact II ......
89
4.2
5
.
TeMPeST I-D design details
.....
TeMPeST 1-D Characterization 4.2.1
Warm-up characteristics
92
4.2.2
LVDT calibration . . . .
93
4.2.3
Force sensor calibration
95
4.2.4
Voice coil calibration . . .
95
4.2.5
Position sensor frequency response
97
4.2.6
Force sensor frequency response . . .
98
4.2.7
Flexure stiffness; actuator effective damping and mass.
5.2
101
105
G UI and controller development 5.1
92
TIDgui: graphical user interface for the TeMPeST I-D . . . . . . . . . .
105
5.1.1
Waveform type selection
106
5.1.2
Sampling and wavefornl parameters .
108
5.1.3
Function buttons
109
.
TID.exe: real-time control and data acquisition for the TeMPeST 1-D 111 8
6
Validc.\tion Tests and Tissue Property Measurements
113
6.1
114
Testing on Mechanical Springs . . '3.1.1
6.2
6.3
6.4
115
Spring testillg apparatus
Testing on Inertial Load . . . . .
119
6.2.1
Inertial load testing method
119
Testing on Silicone Gel Samples . .
121
6.3.1
ARES standard testing of gels ..
122
6.3.2
Cartilage press standard testing of gels
124
6.3.3
TeMPeST 1-D testing of gels. .
126
In Vivo Solid Organ Measurements
128
6.4.1
Laparoscopic testing
129
6.4.2
Open surgical testing
131
6.4.3
In vivo solid organ test results . . . . . .
131
7 Contributions, Discussion and Further Directions
135
135
7.1
Summary
7.2
Instrument and measurement comnlents
137
7.3
Future \vork . . . . . . . . . . . . . . . . . .
142
4
• • • • • •
A N cmenclature
145
B Flexure masks and etch sequence
147
C TeMPeST 3-D
151
D TIDgui
155
9
10
List of Figures 1-1
Tissue :lvlaterial Property Sampling Tool.
24
1-2
TeMPeST I-D sensor/actuator package..
25
1-3
Laparoscope view of TeMPeST I-D testing liver response...
26
2-1
(a) lvIax"vell and (b) Voigt body lumped pararrleter models
30
2-2
Maxwell and Voigt body responses to step loads and displacelneIlts. Note contirluous change in displacement of Maxwell body to step load, and impulse force response of Voigt body to step displacenlent. .
31
2-3
Kelvin body. . . . . . . . . . . . . . . . . . . . . . . .
33
2-4
Kelvin body responses to step load and displacement.
33
2-5
Kelvin body Bode plots. . . . . . . . . . . . . . . . .
33
2-6
Prismatic element uncler sinlple loading and equivalent spring model.
36
2-7
Equivalent magnitude-phase and complex modulus representations of visco-elastic responses. y-axes are linear scale. Derived from IlOOHz) is of interest, the actuators, sensors and
the system as a whole need to have steady DC response, and band\vidth preferably larger tllan the maximum frequency to be cOllsidered. These values represent minimum design goals. Because the tool is intended for use in a minimally invasive en\rironrnent, two further constraints must be taken into account. First, a device will typically take the form of a long shaft with an outside diameter corresponding \vi th a stanclard size for surgical trocars and cauIlulas. 2 l'vlany conlmercial instruments (e.g. shears, grippers, laparoscopes, surgical staplers)
COIne
in 5
2 Trocar: sharp-pointed instrument used to pierce abdominal wall to pertuit placetnent of cannula. Cannula: tube \vith "trap-door" seal, inserted through abdominal wall to permit passage of sur~lcal instrUll1ents, while maintaining elevated pressure inside abdolninal cavity.
55
or lOmm sizes, but 12mm devices are also fairly conlffion, and 12mm cannulas were available in the animal testing facilities that will be described in section 6.4.. Second, if a device will eventually be used to measure human tissue properties, any element that enters the body must be sterilizable, impl~ying that eitller the ,vhole tool, or some detachable part of it must be tolerant of one or more sterilization techniques. Some of these include autoclaving (high temperature saturated steam "bath") and placement in an anoxic en"ironlnent with special gases (such as ethylene oxide [13]) to destroy pathogenic organisms.
Actuator options: linear actuators
3.2
Based on the requirements jllst discussed, a number of candidate classes of actuators that support small deformations and forces are imInediately apparent.
Voice
coil nlotors and solenoids, shape melnory alloy (SivI..r\), and piezoelectric and nlagnetostrictive actuators, among others, \vcre examined to deternline \vhether they could be used to gellerate Inations
011
the order of those considered here. SrvL.t\ \vire actu-
ators are limited by the thermal tinle constant of the \\I'ire, and provide only tellsile loading, however strains of up to approximatel~y 5% can be achieved. Piezoelectric and magnetostrictive nlaterials respond up to very lligh frequencies, but can onI)! generate strains on the order of parts per million; the)r \vould be difficult to use to create an actuator \vith millimeter-scale displacements. Voice coils and solenoids can be designed to have large displacements, reasonable band,vidth, and apply both tellsile and compressive loading. They ,viII be examined in
additi("r~al detail
as the:r \vere the
prime candidates for use in the TeMPeST I-D. Piezoelectrics ,viII also be illustrated as a representative of the class of solid state actuators.
3.2.1
Voice coil actuators and solenoids
Voice coil actuators convert electric Cllrrent to applied force throngh the relation
d} d}
I .
ill
x
13,
appropriately cast for the particular geometry of the actuator.
is the force applied to conductor element 56
ill,
I is the current passing through
f
B
B
Figure 3-1: Force on current carrying conductor in magnetic field: (a) single conductor (b) coil in radial magnetic field
the element, and
B
is the flux density in the region of the conductor element (see
figure 3-1). Voice coil actuators typically employ permanent magnets to generate the B field, and a coil placed such that the B field is perpendicular to its conductors. Running a current through the coil creates a force on the coil. If the coil (or the magnet) is mounted to bearings, it will move under the influence of the applied force, and this motion could be used in this case, to deforrn the tissue. i\lternating current passed through the coil would therefore generate
all
oscillating force a11d displacenlent.
-~
common example of a voice coil actuator is a loudspeaker. When mounted on flexural bearings (as is the case for a loud speaker), the actllator can generate motion in either direction from the rest position and may have nanometer resolution witll proper control. Other applications include disk drive head positioning and wafer stepper fine positioning. Range of motion is typically in the millimeter to centimeter range, depending on the design of the actuator [29]. Constant force can be generated~ and the bandwidth is limited by the coil/actuator mass and the spring constant of any suspension. One drawback is the heat generated in the coils when large forces nlust be generated. Some examples of coil and nlagnet arrangements are shown in figure 3-2. Solenoids use a current carrying coil, but typically have the coil fixed in place, and have a moving ferrous core piece, which is drawn into the coil when current is applied. Force is inversely proportional to the square of the air gap \vidth bet,veen pole pieces. A spring is used to return the core piece to its rest position wilen the current is turlled off. Solenoi::Is are often used in switchillg applications, so that OI11:y the end points of
57
(a)
(b)
(c)
[II]
permanent magnet
•
soft iron pole pieces
D
current carrYlng coil
~ non-ferrous structure
Figure 3-2: \;Ioving-coil voice coil designs: (a) radially Inagnetized ring magnet. (b) flux focusing design~ (c) boncled \vindings design (coil is load-l)earing) motion are irrlportant [29]. Ho\vever. l)y varying the applied current ~ posi tion control can be achieved. Since the rest positioIl corresponds vvith one end of the range of motion, to achieve oscillatory rrlotion~ a nOll-zero offset current can be applied. and an oscillation imposed
OIl
top of that. ~.:.\s \\·ith the voice coil actuators~ Joule heating
occurs in the \vinclings, potentially raising the ternperatllre of the clevice. RJange of rrlotion depends on the length of the coil anel core piece. and can be IOem or greater. i\s with voice coils, static forces can be applied~ and hand\Yidth is deternlined b.y the mass of the core plece aIlfj the stiffness of the return spring. RJotary solenoids and voice coil- type n1otors can also be genera ted ~ as \\'ell as galvanorneter-like actllators~ but these \volllcl require
S0I11e rotar~v
to linear transrnis-
sian to genprate the desired linear indentation lllotioll.
3.2.2
Piezo-electric actuators
Piezoelectric materials undprgo mechanical stra.ins \vhrn electric fields are applied across them. Con1rnon geometries include st.acks of elenlPnts~ \vhose total displace58
ment is the
SUITl
of the elemellts in series, and cantilevered elements which flex, pro-
viding comparatively large amplitude motions at the cantilever end (figure 3-3). Range of motioIl is typicall~y very small, as strains are typically less than 0.1 %.3
.l\S
a result, stacks of electrically parallel and series mechanical piezoelectric elements are asselnbled, so that net deformation is increased, but even so deflections are typically on the order of tens of microns. Further, large voltages (/"'VIDa - lOOOV) typically need to be applied to generate the maximum strain values [29J. Steady displacements can be generated, and band\vidth carl be extremely high. This is partially due to tIle high stiffness of the material. \\lith respect to tissue prop-
erty measurement, ho\vever, high stiffness and lo\v range of motion are disadvantages. As \vas
ShOVlIl
earlier, to achieve a reaction force in the lOOmN range, displacenlents
of approxinlately lmm are necessary (and greater for softer tissues). To generate such a displacelllent \vith a piezo-stack, the stack \vould have to be over one meter long! The smaller forces that \vould be generated \vith sIllaller clisplacernents \vQuld
be increasingly difficult to rneasure accurately. Flexing, binlorph elcnlents can achieve larger clisplacenlents, but typically only
do so \Vherl they' are clrivcn at
resonance~
so that the tip Illation is arnplified. Since
examination of properties over a range of frequencies is of interest, binlorphs "/ould not be apI)fopriate either (anel could be difficult to fit into a
12Illnl
sllaft and still
generate motion in a useful direction).
3.3
Position sensor options
To Illeasure the defornlation of t.he tissue, it Inay be sufficient to IllCclSure the displaceInent of the tip of the tool. To as
I>lots of figure' 4--1, at lo,y fr(~(lUcncy~
the calculatccl cOJll!)liance is slightly higher than th0 IlIOtlcl cornpliance. \'''"'hile not as large as at arrll resonanCcnds 011 accnratp Il1PasurenlPnt of position alIt! for("t:'. but is fairly indelJendcnt of the prpcis(' trajectory· follo\\·f'd
b~· t he
Figure 4-6 sho\vs plots of forcfl and position
actuator.
SPIlSO[
voltap;p output (or
IIlOr(' pr0-
cisely, output of thf' instrulllcntat.ion aU1l)liHer and thr I.J\·O'T' signal conditioning hard\\"are) versus t inlP aft(lr apI)I~"ing po\\"pr. F'rorn this plot, t hp forc(\ SflIlsor al)ppars
92
0.4
r------r---~---__r_, - ---...----~----,
G----€>
0.35
I+---+ ._~
force sensor f LVDT
,
Q)
en c 0.15 ~ (
~
~
15 >
01°
.
()
0.05
-0.05 -0.1
-1' ~
o
_ _--"
--""'
5
10
settle
-
-""'
---'--
15 time (min)
20
......lo-_ _. - - - J
25
30
Figure 4-6: Initial zero-forcejzero-displacenlent \.varrrl-Up response of position and force sensors. Force sensor 5% settling tirne is approx. 12 min.
to have a heavily damped second order response with a 5% settling time of approximately 12 minutes, \vhile the position sensor settles almost ilnmediately. The L\tDT users manual recomrrlends a IS-minute \varm-up period, \\t"hich is on tIle same order as the settling time of the force sensor, so this period is recomn1ended to ensure that the Te::'vIPeST 1-0 ha..f.) reached a condition that can l)c considered stea(ly st.ate.
4.2.2
LVDT calibration
The Schaevitz 099 XS-B Lv'D1"' is nlanufactured to have a linearit.y of ±l.O% of the
f1111 range maximum. The initial calibration sequence described in the user's lllanual for the Schaevitz .A.Ti\ 2001 signal conditioner uses the neutral rest- and full scale positions to set the gain ancl offset. To verify the calibration constant and linearity, a micrometer-bae,ed calibration jig was developed. as
ShO\VIl
in figllre 4- T. \\lith the
system \varn1ed up, Ineasurerrlents of output voltage were taken at
O.002~~
increments,
the results of which are presented in figure 4-8. "'fhe calil)ration constant for position sensing is approxinlatel~/ lO.2\l/mm. 93
.,
.
:
--:..-
'"'I. ~I
••
..
-:
" .. "'
__-
: ",
.f
...
.. 1' ......
••
nll Lr()met eor
L\'rrr,
F'igllrp -1-7: (~alil)J'at l(dl .il(~ fur i('( i 1 all (i fl) I (. ~ S l Il ~ I q .
\' I )
t
(' ()
I
10
;t:--;
I
I
i i
...
""- 'tions of their true responses.
e-:3.27 E-4s
H(s) - - - · - 211"3808 + 1
100
(4.17)
4.2.7
Flexure stiffness; actuator effective damping and ITlass
As was described in the second order model earlier, the actuator can be modeled as a three parameter systern, with stiffness, a damping elernent and a mass. These parameters can be extracted from the free motion frequency response as follows. The combined stiffness of the two flexures (and the force sensor/voice coil wires) can be determined in
t\VO
ways. The first uses tIle LVDT calibration jig micrometer
to push against the tip of the indenter, while recording the force sensor output. The alternate approach is to pass current through the voice coil, using the known currentforce constant to calculate force, and record the position response with the LVDT.
If a series of sinusoids of different frequencies, or a chirp signal covering a range of frequencies is used to drive the voice coil, the resonant frequency, and therefore the effective mass, of the actuator cal1 also be determined. Figure 4-14 shows data points for the static and quasi-static compliance of the flexure. The quasi-static data are taken in t,vo forms: tb.e slope of the least-squares
fit of the force-displacement data; and also as the ratio of the FFT magnitudes of the force and position at O.05Hz 1 . As shown in the figure, they overlay each other precisely. Taking the ratio of the FFTs also yields a phase value for the quasi-static case, showing that there is no lag bet\veen force and displacement. The low frequency asymptote of the chirp response also corresponds \vith the static and quasi-static data. From these results, the equivalent stiffness of the flexures is found to be 276N/m. The damping ratio (and damping coefficient, b) due to air motion within the actuator; material damping, and friction bet\veen the moving and stationary parts can be determined from the ratio bet\veen the resonant and static compliance (!vIp)
by using equation 4.18 (and 4.20). It can also be determined by performing a best fit on the phase lag to that of an ideal second order system \vith dalnping as an unknown parameter. The resonant and static compliances and daulped natural frequency are shown in figure 4-14.
1 well
below the dominant system resonances.
101
(4.18)
With a value for (, the effective mass can be found using the damped natural frequency,
Wd
(see equation 4.19).
Using a chirp signal on the (rigidly clamped)
TeMPeST I-D, the damped natural frequency was found to be 65.8Hz, yielding an equivalent mass of 1.6 grams. This value is on the same order as an estimate based on the designs for the individual components of approximately 1.2g. This estimate, however, did not include the effective mass of the moving part of the flexures, small amounts of epoxy used to bond parts together, and sllort lengths of copper \vire connecting the ITloving force sensor and voice coil to the fixed housing.
Wn
-
=}m
-
"
If
Wd
Jl -
2(2
k(l - 2(2) f.N1 2
d
1.6g
(4.19)
Comparing the de?ominators of the transfer functions of a normalized form of equation 4.1 and a unity gain second order system permits calculation of the damping coefficient (equation 4.20):
2 S
b k + -8+m m
8
+ 2(w n s + w~
2m(wn
=>b -
2
O.20Ns/m
102
(4.20)
10-4
~---",----rr._ _"""","",-~_--'---'---A.............."""""",,-,_-.a..-
--'--''-''''''''~_--A..-
--'''''''''''''''''''''''''''''''----'
10- 1
~.
o +
+
•
•
•
•
..
..
•
f'
static (calibration) O.05Hz xlf O.05Hz XlF 1
10 frequency (rad· S-1)
Figure 4-14: Static, quasi-static and dynamic force-displacement response for the indenter. Ideal second order response overlaid over data. Figure 4-14 shows the frequency response of an ideal second order system with these parameters overlaid on the non-parametric tranfer function determined from the ratio of the position and force FFTs.
103
104
Chapter 5 G VI and controller development A graphical user interface (figure 5-1), developed 11sing MATLAB, v5.0 and the QUI Design Environment (GUIDE), provides a convenient interface to generate open-loop current trajectories for the TeMPeST I-D and perform post-processing. Real-time control of the TeMPeST I-D, including commanding voice coil current and performing data acquisition from the force sensor and LVDT, is performed by a console application written in C++ with Microsoft Visual
C++ v5.0. Detailed descriptions
of the function of these elements follow.
5.1
l.'lDgui: graphical user interface for the TeMPeST I-D
Since the physical input for the TeMPeST I-D is the current driven in the voice coil actuator, a means for generating the current trajectory is required. Similarly, after position and force data are acquired, some basic post-processing is desired to ensure that no errors or failures occurred during acquisition, and to provide guidance as to which additional experiments should be performed (e.g. different range of frequencies, different amplitudes). The MATLAB-based graphical user interface shown in figure 51
provid~s
all of this functionality.
105
gTl'Ogui
"
lie1-t?e.5rt-p Control Panel
L~dData
I
I!lIiIEi
"
I
S~mp6ng Rate 1500Hz
Wav\:form
r Sinu!l:oid r Square r
Amplitude (mA)
Unear Chirp
Offset (ITA)
Extract F(l '"Tt::..'?~;'~:~l ,~ ~.::"".~r~~~ :V,.1~ ,yP?, ~';'f '?~;:{L:~.~~;:";~7':~ ,.~;,:.:,:~ :.. ,~::"
