346
`
`Sensors for Mobile Robot:
`
`Ella) and current swing of the oscillator circuit (Kim & Hawks, 1989). The
`square—wave oscillator output of each of three identical channels is fed directly to
`the onboard microprocessor without the need for complicated interface circuitry.
`
`
`
`Figure 12-18. The TCM' compass employs a three-axis strap-down magnetometer in conjunction
`with a twoaxis tilt sensor to compensate for variations in vehicle attitude (courtesy Precision
`Navigation. Incl.
`
`Automatic distortion-detection algorithms are incorporated that raise a warning
`flag when magnetic disturbances {i.e., close-proximity metallic objects or
`electrical cabling) are compromising compass accuracy. Pitch-and-roll outputs
`are available for external use with 0.1-degree resolution at an accuracy of i022
`degrees. Ambient temperature information is also provided War a range of -20 to
`+70°C. with an accuracy of $0.5 degrees. Both digital outputs (RS-232 or
`NMEA-0183) and linear quadrature analog outputs (0-5 volts} are standard.
`Vcc
`Vcc
`Sensor
`A
`
`T
`R2
`Coil
`ZS
`
`if»
`_m
`
`
`
`.
`—)- Lruipul
`
`Ucc
`A
`
`Ft‘
`
`1
`
`T
`
`
`
`R5
`
`Figure 12-19. Block diagram of a single-axis sense element as implemented on the TCM compass
`(adapted from Kim & Hawks. 1989).
`
`Power requirements for the TCM compass are 5 to 25 volts DC at 6 to 12
`milliamps, depending on user configuration. The DEM circuit board measures 2.5
`
`
`SilverStar Exhibit 1016 - 361
`SilverStar Exhibit 1016 - 361—
`
`

`

`Chapter 12 Magnetic Compasses
`
`34?
`
`by 2 inches wide by 1.1 inches high. weighs 1.6 ounces. and with a tilt range of
`:25 degrees costs only $700. (Additional tilt ranges of 60 and 90 degrees are also
`available at slightly higher cost.) The moderate price, extremely low power
`consumption, elimination of gimbal-induced measurement errors, small size and
`weight. plus availability of pitch, roll, and ambient temperature outputs make the
`TCM—Serr’es
`a
`strong contender
`for mobile
`robotic
`applications.
`Field
`performance evaluations are currently underway for early prototypes installed on
`both ROBART III and the MDARS Interior robot (Chapter 1).
`tilt
`An extremely low-cost
`[$50)
`two-axis electronic compass without
`compensation. the Vector-2X. is available as well for less demanding applications.
`with an overall accuracy of :2 degrees.
`
`12.4 Hall—Effect Compasses
`
`Recall from Section 3.2.1 that Hall—efiecr sensors in the presence of an external
`magnetic field develop a DC voltage across a semiconductor region that
`is
`proportional to the magnetic field component at right angles to the direction of
`current flow (Wood. [986). One advantage of this technology (i.e.. relative to the
`fluxgate) is the inherent ability to directly sense a static flux. resulting in much
`simpler readout electronics.
`Early Hall magnetometers could not match the
`sensitivity and stability of the fluxgate (Primdahl, [979), but the sensitivity of
`Hall devices has improved significantly. The more recent indium—antimonidide
`devices have a lower sensitivity limit of 10'3 Gauss (Lenz. 1990).
`The Navy in the early 19605 showed considerable interest in a small solid—state
`Hall-effect compass for low-power extended operations in sonobuoys (Wiley.
`1964). A number of such prototypes were built and delivered by Motorola for
`evaluation. The Motorola compass employed two orthogonal Hall-effect devices
`for temperature-mulled non—ambiguous resolution of the geomagnetic field vector.
`Each sensor element was fabricated from a 2- by I by 0.1-tnillimeter indiumw
`arseniderferrite sandwich and inserted between two wing—like mumem!
`flux
`concentrators as shown in Figure 12—20.
`It
`is estimated the 2minch magnetic
`concentrators increased the flux density through the sensing elements by two
`orders of magnitude (Wiley. 1964). The output of the Motorola unit was a
`variable-width pulse train. the width of the pulse being proportional to the sensed
`magnetic heading.
`Excellent response linearity was reported down to flux
`densities of 0.01 Gauss (Wiley, 1962).
`Maenaka. et a1. (1990) report on the development of a monolithic silicon
`magnetic compass at the Toyohashi University of Technology in Japan, based on
`two orthogonal Hall-effect sensors. Their use of the terminology “magnetic
`compass" is perhaps an unfortunate misnomer. in that the prototype device was
`tested with an external field of 1,000 Gauss. Contrast this field strength with that
`of the earth's magnetic field. which varies from only about 0.1 Gauss at
`the
`equator to about 0.9 Gauss at the poles. Silicon-based Hall-effect sensors have a
`
`
`SilverStar Exhibit 1016 - 362
`SilverStar Exhibit 1016 - 362
`
`

`

`348
`
`Sensors for Mobile Robots
`
`lower sensitivity limit of around 10 Gauss (Lenz. 1990). It is likely the Toyohashi
`University device was intended for other than geomagnetic applications. such as
`remote position sensing of rotating mechanical assemblies.
`
` /
`
`Fe
`
`’
`
`Fe
`
`\
`
`Fe
`Indium. #
`Arsemde
`
`
`
`Fe 1—— Indium
`
`4'
`Arsenide
`
`
`
`Figure [2-20. A pair of indium‘arsenide-ferrite Hall-effect sensors (one shown) are positioned
`between flux concentrating wings of numeral in this early Motorola prototype (adapted from
`Wiley‘ 1964).
`
`This prototype Hall-effect magnetometer is still of interest in that it represents
`one of the first fully self-contained implementations of a two-axis magnetometer
`in integrated circuit form. Two vertical Hall cells {Maenaka, et al, 1987) are
`arranged at right angles as shown in Figure 12-21 on a 4.7-n1illimeter square chip,
`with their respective outputs coupled to a companion signal processing IC of
`identical size.
`(Two separate chips were fabricated for the prototype instead of a
`single integrated unit
`to enhance production yield.) The sensor and signal
`processing [Cs are interconnected {along with some external variable resistors for
`calibration purposes) on a glass-epoxy printed circuit board.
`
`By Ls.“em
`
`
`
`
`
`
`
`
`
`Figure 12-21. Two venical Hall cells are arranged at right angles on a 4.?—mi|limeter~square chip
`in this two-axis magnetometer developed at the Toyohashi University of Technology in Japan
`(adapted from Maenaka, et al.. l990).
`
`The dedicated signal-processing circuitry converts the B—field components Bt
`and By measured by the Hall sensors into an angle 6 by means of the analog
`operation (Maenaka, et al. 1990):
`
`
`SilverStar Exhibit 1016 - 363
`SilverStar Exhibit 1016 :363
`
`

`

`Chapter 12 Magnetic Compasses
`
`349
`
`1
`
`9 = arclan
`
`where:
`
`B = angle between B-field axis and sensor
`litr = .r—component of B field
`B}. = ykcomponent of B field.
`
`The analog output of the signal-processing IC is a DC voltage that varies
`linearly with vector orientation of the ambient magnetic field in a plane parallel to
`the chip surface. Reported test results show a fairly straight—line response (i.e.. :2
`percent full scale) for external field strengths ranging from 3,000 Gauss down to
`500 Gauss; below this level performance begins to degrade rapidly (Maenaka, e1
`31.. 1990). A second analog output on the IC provides an indication of the
`absolute value of field intensity.
`While the Toyohashi “magnetic compass” prototype based on silicon Hallv
`effect
`technology is incapable of detecting the earth's magnetic field.
`it
`is
`noteworthy nonetheless.
`A two—axis monolithic device of similar nature
`employing the more sensitive indium-antimonide Hall devices could potentially
`have broad appeal for low-cost applications on mobile robotic platforms. For
`increased sensitivity, an alternative possibility would be to use magnetoresistive
`sensor elements. to be discussed in the next section.
`
`12.5 Magnetoresisrive Compasses
`
`The general theory of operation for anisotropic magnetorei‘isrive (AMI?) and giant
`magneroresisrive (GMR) sensors as used in short-range proximity detection was
`previously presented in Chapter 3. Recall three properties of the magneroresistt've
`magnetometer make it well suited for application as a geomagnetic sensor:
`l)
`high sensitivity,
`2) directionality, and
`3)
`in the case of AMR sensors, the
`characteristic
`“flipping“
`action associated with the direction of
`internal
`magnetization.
`AMR sensors have an open-loop sensitivity range of 10'1 to 50 Gauss (which
`easily covers the 0.1- to Ill—Gauss range of the earth's horizontal magnetic field
`component), and limited-bandwidth closed-loop sensitivities approaching 10'“
`Gauss (Lena, 1990). Excellent sensitivity, low power consumption, small package
`size, and decreasing cost make both AMR and GMR sensors increasingly popular
`alternatives to the more conventional fluxgate designs used in robotic vehicle
`applications.
`
`
`SilverStar Exhibit 1016 - 364
`SilverStar Exhibit 1016 - 364
`
`

`

`350
`
`Sensors for Mobile Robots
`
`12.5.1 Philips AMI-I Compass
`
`One of the earliest magnetoresistive sensors to be applied to a magnetic compass
`application is
`the KMZIOB offered by Philips Semiconductors BV. The
`Netherlands (Dibbum & Petersen, 1983; Kwiatkowski & Tumanski. 1986;
`Petersen. 1989).
`The limited sensitivity of this device [approximately 0.1
`mV/Nm with a supply voltage of 5V DC) in comparison to the earth’s maximum
`horizontal magnetic field (15 Aim) means that considerable attention must be
`given to the error—inducing effects of temperature and offset drift (Petersen, [989).
`One way around these problems is to exploit
`the “flipping“ phenomenon
`(Chapter 3) by driving the device back and forth between its two possible
`magnetization states with square—wave excitation pulses applied to an external
`coil (Figure 1242). This switching action toggles the sensor’s axial magnetic
`field as
`shown in Figure 12-22A.
`resulting in the alternating response
`characteristics depicted in Figure 12~22B.
`Since the sensor offset
`remains
`unchanged while the signal output due to the external magnetic field H,
`is
`inverted (Figure 12—22A).
`the undesirable DC offset voltages can be easily
`isolated from the weak AC signal.
`
`Huantitm Cuttenl
`
`
` Mn Mllmllflfl
`
` B
`
`
`l— — —— — —(llfsel
`one
`
`Figure 12-22. External current pulses set and reset the direction of magnetization. resulting in the
`"flipped" response characteristics shown by the dashed line. Note the DC offset of the device
`remains constant. while the signal output is inverted (adapted from Petersen. [939].
`
`A typical implementation of this strategy is shown in Figure 1223. A lOO-Hz
`square-wave generator is capacitively coupled to the external excitation coil L
`which surrounds two orthogonally mounted magnetoresistive sensors.
`The
`sensors‘ output signals are amplified and AC-coupled to a synchronous detector
`driven by the same square—wave source. The rectified DC voltages V3; and V”;
`are thus proportional to the measured magnetic field components H; and H2.
`Determination of applied field direction is dependent on the ratio as opposed to
`absolute values of these output signals, and so as long as the two channels are
`calibrated to the same sensitivity, no temperature correction is required (Fraden,
`1993).
`
`
`SilverStar Exhibit 1016 - 365
`_Si|verStar Exhibit 1016 - 365
`
`

`

`Chapter 12 Magnetic Compasses
`
`351
`
`
`
`H
`
`I
`
`
`
`L
`
`
`
`
`
`
`
`
`
`
`
`I
`lienernlor
`Square—wave
`
`V B
`
`
`
`> new
`
`—r
`S nchmnous
`Dgteclur
`
`Amplifier
`
`D—eww
`
`Figure 12-23. Block diagram of a two-axis magnetic compass system based on a commercially
`available anisotropic magnetoresistive sensor such as the Philips KMZICPB (Petersen. 1989).
`
`12.5.2 Space Electronics AMR Compass
`
`The Space Electronics Micro-Mag sensor introduced in Chapter 3 (SE1, 1994;
`Lao, 1994) can be configured as shown in Figure [2-24 to function as an
`anisotropic magnetoresistive (AMR) compass. The integral BSD-ohm temperature
`compensation resistor (RTD) is connected in the lower arm of a Wheatstonc
`bridge in series with a IOU—ohm [O-turn trimming resistor.
`Two identical
`channels are required, with their associated AMR sensors mounted in an
`orthogonal fashion to yield output voltages proportional to the sine and cosine of
`magnetic field azimuth.
`
`
`jail]
`
`
`
`
`
`
`
`
`
`
`
`Sterner
`
`rife}:
`Past
`
`
`File;
`Figure 12-24. Typical application circuit for the SE1 MMSIOJ‘ Mir-rolling that provides an output
`voltage proportional to the cosine of magnetic azimuth for a gimbaled sensor in the horizontal
`plane (mnrtesy Space Electronics, Inc.)‘
`
`
`
`SilverStai Exhibit 1016 - 366
`SilverStar Exhibit 1016 - 366
`
`

`

`352
`
`Sensors for Mobile Robots
`
`12.5.3 Honeywell HMR Series Smart Digital Magnetometer
`
`The Honeywell Magnetoresistive (HMR) Series of magnetometers incorporates
`three orthogonal sensor axes, each consisting of a permalloy thinAfilm Wheatstone
`bridge configuration deposited on a silicon substrate as discussed in Chapter 3
`(Honeywell, 1994b). Changes in bridge resistance are converted to a digital
`output signal (prespecified 118—232 or RS485) by internal AID converters and a
`dedicated microprocessor, with 12-bit output resolution (ll bits plus sign). A
`switching technique is employed to “flip" the sensor characteristics back and forth
`between the two possible magnetic states {see again Chapter 3), thus canceling the
`DC offset and past magnetic history of the pemtailoy bridges, in addition to any
`offset
`introduced by the sensor electronics (Honeywell, 1994a). The unit
`is
`packaged in a compact rectangular enclosure measuring [.12 by L75 by 3 inches
`as shown in Figure 12—25.
`
`
`
`is a three-axis
`The Honeywell HMR-Series Smart Digital Magnetometer
`Figure 12-25.
`magnetoresistive magnetometer Willi a sensitivity of I milliGauss over a measurement range of :l
`Gauss (courtesy Honeywell Solid State Electronics Center).
`
`Output values for the three axes (X. Y. and Z) are transmitted in two-byte
`hexadecimal format upon request from the external host processor. where they can
`be combined widt extemally supplied information regarding vehicle attitude to
`calculate a tilt-compensated magnetic heading solution. At 38.4 kilobaud. the
`maximum update rate is 54 Hz. The current bridge temperature reading is also
`made available with 8-bit resolution. The magnetometer has a measurement range
`of i1 Gauss {each axis} with a sensitivity level of l milliGauss and provides a
`digital resolution of 0.5 milliGauss per least-significant bit. Overall accuracy is
`:1 percent of full scale. Power requirements are 12 to 15 volts DC (single supply)
`at 40 miiliamps. An HMR Series Development Kit is now available from the
`Honeywell Solid State Electronics Center. Plymouth, MN.
`that
`includes the
`
`
`SilverStar Exhibit 1016 - 367
`SilverStar Exhibit 1016 - 367
`
`

`

`Chapter 12 Magnetic Compasses
`
`353
`
`magnetometer, power supply. cabling, operating manual, and IBM-compatible PC
`software.
`
`12.6 Magneroeiastic Compasses
`
`A number of researchers have recently investigated the use of magneroetasric
`(also known as magnetostn‘ctive) materials as
`sensing elements for high-
`resolution magnetometers. The principle of operation is based on the changes in
`Young’s modulus experienced by magnetic alloys when exposed to an external
`magnetic field. The modular of elasticity E of a given material is basically a
`measure of its stiffness, and directly relates stress to strain as follows:
`
`where :
`
`E = Young’s modulus of elasticity
`0' = applied stress
`a = resulting strain.
`
`Any ferromagnetic material will experience some finite amount of strain
`(expansion or shrinkage)
`in the direction of magnetization due
`to this
`magnetcstriction phenomenon.
`It stands to reason that if the applied stress 6
`remains the same, strain 8 will vary inversely with any change in Young’s
`modulus E. In certain amorphous metallic alloys. this effect is very pronounced.
`Barrett, et a1. (1973] propose a qualitative explanation, wherein individutfl
`atoms in the crystal lattice are treated as tiny magnetic dipoles. The forces exerted
`by these dipoles on one another depend upon their mutual orientation within the
`lattice; if the dipoles are aligned end to end. the opposite poles attract, and the
`material shrinks ever so slightly. The crystal
`is said to exhibit a negative
`magnetosrricrion constant in this direction. Conversely. if the dipoles are rotated
`into side-by-side alignment through the influence of some external field,
`like
`poles will repel, and the result is a small expansion.
`It follows the strength of an unknown magnetic field can be accurately
`measured if suitable means is employed to quantify the resulting change in length
`of some appropriate material displaying a high magnetostn’ctt‘on constant. There
`are currently at least two measurement technologies with the required resolution
`allowing the magnetoelastic magnetometer to be a realistic contender for high-
`sensitivity low-cost performance: 1) interferometric displacement sensing and 2)
`tunneling-tip displacement sensing.
`Lenz (1990) describes a magnetoelastic magnetometer which employs a Mach-
`Zender
`fiber-optic interferometer
`to measure the change in length of a
`magnetostricrr‘w material when exposed to an external magnetic field. A laser
`
`Silver’star Exhibit 1016 - 368
`SilverStar Exhibit 1016 - 368
`
`

`

`354
`
`Sensors for Mobile Robots
`
`source directs a beam of light along IWo optical fiber paths by way of a beam
`splitter as shown in Figure 12-26. One of the fibers is coated with a material
`(nickel iron was used) exhibiting a high magnetostrictiue constant. The length of
`this
`fiber
`therefore is
`stretched or compressed in conjunction with any
`magneroelastic expansion or contraction of its coating. The output beam from
`this fiber-optic cable is combined in a light coupler with the output beam from the
`uncoated reference fiber and fed to a pair of photodetectors.
`
`Optical
`Fiber ‘x
`
`4— —_
`Loser
`Diode
`
`—
`
`
`Sensing Leg
`
`
`Fri—-
`Liqht Cooper
`‘-—-—_._.____
`
` 3'
`
`Phclodeiectnrs
`
`
`
`a
`fim—/
`7—
`Figure til-26. Fiber—optic magnetometers. basically a Mach-Zender interferometer with one fiber
`coated or attached to a magnetoelastic material. have a sensitivity range of 10'? to IE Gauss
`(adapted from Lenz. ”390. ea IEEE)‘
`
`Constructive and destructive interferences caused by differences in path lengths
`associated with the two fibers will cause the final output intensity as measured by
`the photodetectors to vary accordingly. This variation is directly related to the
`change in path length of the coated fiber, which in turn is a function of the
`magnetic field strength along the fiber axis. The prototype constructed by Lenz
`(1990} at Honeywell Corporation measured 4 inches long by | inch wide and was
`able to detect fields ranging from 10':f Gauss up to 10 Gauss.
`Cantilever
`
`
`
` Sudoce
`Figure 12-27. Scanning tunneling microscopy. invented at IBM Zurich in 1982, uses quantum
`mechanical
`tunneling of electrons across a barrier to measure separation distance at the gap
`(courtesy T.W. Kenny. NASA IPLJ.
`
`the Naval Research Laboratory (NRL) have developed a
`Researchers at
`prom! pc magnetoelastic magnetometer capable of detecting a field as small as 6
`X 10' Gauss using the tunneling-tip-Iransducer approach (Brizzolara. et 31.,
`1989). This new displacement sensing technology. invented in 1982 at IBM
`Zurich. is based on the measurement of current generated by quantum mechanical
`tunneling of electrons across a narrow gap (Figure 12-27). An analog feedback
`circuit compares the measured tunnel current with a desired setpoint and outputs a
`drive signal to suitably adjust the distance between the tunneling electrodes with
`an electromechanical actuator (Kenny. et al.. 1991}. The instantaneous tunneling
`
`
`SilverStar Exhibit 1016 - 369
`SilverStar Exhibit 1oi6 - 369
`
`

`

`Chapter 12 Magnetic Compasses
`
`355
`
`current is directly proportional to the exponential of electrode displacement. The
`most common actuators employed in this role are pieZOelectric and electrostatic.
`the latter lending itself more readily to silicon micromachining techniques.
`The active sense element
`in the NRL magnetometer is a
`ill-centimeter
`metallic~glass ribbon made from METGLAS 260532. annealed in a transverse
`magnetic field to yield a high magnetomechanical coupling (Brizzolara. et al..
`[989). The magnetoelastic ribbon elongates when exposed to an axial magnetic
`field, and the magnitude of this displacement
`is measured by a tunneling
`transducer as illustrated in Figure [2-28.
`
`
`'—-_I
`
`
`lecrny
`véiiahg i—fl FeEdWCR
`35.jpg
`.I‘imp‘ii
`l'letunnics
`
` Solenoid Coils
`
`
`
`Tunneling
`llp
`
`Approach
`lunnelinq
`”gummy“
`“p
`
`
`
`Uuerlr Tube
`
`uncnelusluctwe
`ther
`
`The NRL tunneling~nansducer magnetometer employed a
`Iii—centimeter
`Figure 12-28.
`magnetoeiastic ribbon vertically supported in a quartz tube (Brizzolara. et al., 1989).
`
`An electrochemically etched gold tip is mounted on a tubular piezoelectric
`actuator and positioned within about
`1 nanometer of the free end of the
`METGLAS ribbon. The ribbon and tip are electrically biased with respect to each
`other, establishing a tunneling current that is fed back to the piezo actuator to
`maintain a constant gap separation.
`The degree of magnetically induced
`elongation of the ribbon can thus be inferred from the driving voltage applied to
`the piezoelectric actuator. The solenoidal coil shown in the diagram supplies a
`bias field of 0.85 oersted to shift
`the sensor into its region of maximum
`sensitivity.
`The NRL group in collaboration with the Jet Propulsion Laboratory. Pasadena,
`CA. has more recently developed an alternative magnetic sensor that uses a
`tunneling transducer to measure the induced torque on a suspended magnet due to
`low—frequency field changes (DiLelIa, et al.. 1995). The sensor consists of two
`micromachined
`silicon wafers
`assembled
`into
`a
`structure measuring
`approximately 1
`inch by 1
`inch by 0.] inch (Figure 12—29). The upper wafer
`includes a permanent magnet attached to a rectangular support suspended from a
`pair of torsion beams. The underside of the magnet faces the tunneling tip and
`serves as both the tunneling counter electrode and one of two rotation control
`electrodes. The lower component consists of the other rotation control electrode
`and the tunneling tip as illustrated below.
`
`
`SilverStar Exhibit 1016 - 370
`SilverStar Exhibit 1016 - 370
`
`

`

`356
`
`Sewers for Mobile Robots
`
`lorsmn Beam
`
`
`
`
`
`Deflection
`
`Electrode
`
`Figure 12—29. Cross-sectional diagram of the NRUJ'PL micromachined magnetic-field sensor
`based on an electron-tunneling displacement transducer (courtesy Naval Research Lab].
`
`Because of the offset placement of the lower rotation control electrode with
`respect to the longitudinal axis of the torsion beams, an electrostatic torque is
`generated by the voltage difference between the electrodes, rotating the magnet
`assembly into tunneling range of the tip. This electrostatic torque about the
`torsion~bearn axis is balanced by the resulting torsional stress in the beams and a
`magnetically induced torque generated by the ambient magnetic field acting upon
`the permanent-magnet dipole. Once the desired tunneling current is established
`and maintained by a simple feedback control circuit, any subsequent change in
`electrode voltage can be attributed to variations in the ambient magnetic field.
`The calculated sensitivity limit of this sensor configuration based on fundamental
`noise sources is 0.002 nTNHz at
`I Hz, while the actual measured sensitivity of
`the prototype is 0.3 nT/v'llz at 1 Hz (DiLclia, et al., 1995.).
`Fenn, et a]. (1992} propose yet another tunneling mgnetoetasttc configuration
`with a predicted sensitivity of 2 x 10'11 Gauss, along the same order of magnitude
`as the cryogenjcally cooled SQUID. A small cantilevered beam of METGLAS
`260552. excited at its resonant frequency by a gold-film electrostatic actuator. is
`centered between two highvpermeability magnetic flux concentrators as illustrated
`in Figure 12—30. Any changes in the modulus of elasticity of the beam will
`directly affect its natural frequency;
`these changes in natural frequency can then
`be measured and directly related to the strength of the ambient magnetic field.
`The effective shift in natural frequency is rather small, however ('Fenn reported
`only a 6-H: shift at saturation), again necessitating a very precise method of
`measurement.
`
`*"J
`'
`MEGLAS
`0.7mm
`r
`Cantilever
`
`
`l
`flu]:
`4
`Flu:
`
`
`
`l” l 3? Guide
`Guide %§
`l
`lM 5- 1H
`
`
`|
`‘I or from
`3"
`Figure 12—30. Top view of the single cantilevered design (adapted from Fun at at. [992}
`
`Substrate
`
`j
`mm
`1
`
`
`
`
`SilverStar Exhibit 1016 - 371
`SilverStar Exhibit 1016— - 371
`
`

`

`Chapter 12 Magnetic Compasses
`
`35'?
`
`is employed to track the
`A second (non-magnetic) cantilever element
`displacement of the METGLAS reed with subangstrom resolution using tunneling-
`transducer displacement sensing as illustrated in Figure 12-31.
`A pair of
`electrostatic actuator plates dynamically positions the reed follower to maintain
`constant
`tunneling current
`in the probe gap,
`thus ensuring a constant
`lateral
`separation between the probe tip and the vibrating reed. The frequency of the
`excitation signal applied to the reed-follower actuator
`is
`therefore directly
`influenced by any resonant frequency changes occurring in the METGLAS reed.
`The magnetometer provides an analog voltage output which is proportional to this
`excitation frequency, and therefore indicative of external magnetic field
`amplitude.
`
`
`
`
`
`
`- #955443, "
`¢ Met
`
`
`
`
`
`£g£fl$fl$
`figfiéfl
`
`
`
`
`
`
`
`tail?"
`METOLAS Reed
`
`_ Tunneling-Tip
`Cantelever
`
`
`
`
`
`- "fifigfié
`
`
`Figure 12-31. Side View of the double cantilevered design (adapted from Penn. 6! 31.. 1992).
`
`
`
`
`
`Reed-Following
`Aciuoior
`
`One anticipated problem associated with such magnetoelastic devices is that
`changes in Young‘s modulus also occur due to temperature shifts. Fenn, et a1.
`(1992) report a 1-Hz bandwidth sensor would require a temperature stability of
`10'7°K during the measurement period and suggest thermal
`isolation using a
`vacuum jacket and multilayer insulation.
`
`12.7 References
`
`Acuna, M.H., Pellerin, (3.1.. "A Miniature Two-Axis Fluxgate Magnetometer. ”
`IEEE Transactions on Geosct’ence Electronics, Vol. GEv7. pp. 252-260, 1969
`Barrett. C.R.. Nix. W.D., Tetelman. A.S.. The Principles of Engineering
`Materials, Prentice Hall, Englewood Cliffs, NJ, 1973.
`Bola, R,E_, Tuve, G.L., eds, CRC Handbook of Tables for Applied Engineering
`Science. CRC Press, Boca Raton, FL, 1979.
`Bozorth, R.M., Chapin, D.M.. “Dernagneiizing Factors of Rods." Journal of
`Applied Physics, Vol. 13, pp. 320—326, May, 1942.
`Brizzolara, R.A., Coiton. R.J., Won-Fogie. M., Savage, H.T.. “A Tunneling-tip
`Magnetometer,” Sensors and Actuators, Vol. 20, pp. 199205, 1989.
`
`
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`Sewers for Mobile Robots
`
`Carlson. A.B., Gisser, D.G., Electrical Engineering: Concepts and Applications,
`Addison-Wesley. Reading, MA. p. 644, 1931.
`Carter, E.F., ed. Dictionary of Inventions and Discoveries, Crane, Russak, and
`Co., NY, 1966.
`Dahlin. T., Krantz, D.. “Low-Cost, Medium Accuracy Land Navigation System,”
`Sensors, pp. 26-34. February, 1938.
`Dibburn, U., Petersen. A., “The Magnetoresistive Sensor - a Sensitive Device for
`Detecting Magnetic Field Variations,” Electronic Components and
`Applications. Vol. 5. No. 3. June. 1983.
`DiLella, D., Colton, R.J.. Kenny, T.W., Kaiser, W..l., Vote, E.C., Podosek, J.A.,
`Miller. L.M.. “A Micromachined Magnetic-Field Sensor Based on an
`Electron Tunneling Displacement Transducer." to be published in Sensors
`ondAcmotors, 1995.
`Dinsmore. 1490 and 1525 Magnetic Sensors. Product Literature. Dinsmote
`Instrument Company, Flint, MI. January, 1991.
`Fenn, R.C., Gerver. M..l., Hockney, R.L., Johnson, B.G., “Microfabricated
`Magnetometer Using Young’s Modulus Changes in Magneloelastic
`Materials," SP'LE Vol. E694, 1992.
`Fraden. J ., AIP Handbook ofModem Sensors, ed., Radebangh, 11.. American
`Institute of Physics, New York, 1993.
`Foster, M.. "Vehicle Navigation Using the Plessy Adaptive Compass," RIN
`Conference Proceedings, Land Navigation and Location for Mobile
`Applications. York, England, 1985.
`Geyger. W.A., Magnetic Amplifier Circuits, 2”6 ed., McGraw-Hill, New York.
`1957.
`
`chger. W.A., J. Appl. Phys, Vol. 33, suppl., pp. 1280-1281, 1962.
`Gilbert. W.. “De Magnete." 1600. (Translation: P.F. Mottelay, John Wiley,
`1893.}
`Gordon. D.l., Lunsten, R.H.. Rev. Phys. Appl.. Vol. 5, pp. 175-177. 1970.
`Grenoble. 3., “Sensor and Logic Form Digital Compass,“ Electronic Design
`News. pp. 228-229, 6 December, 1990.
`Halliday. D., Resnick, R.. Fundamentals ofPhyst‘cs. John Wiley, New York, NY,
`1974.
`
`Hine, A., Magnetic Compasses and Magnetomerers. Adam Hilger Ltd.. London.
`1963.
`
`Honeywell, “Smart Digital Magnetometer," l-[MR Series Product Literature
`900133, Rev. A. Honeywell Solid Slate Electronics Center, Plymouth, MN,
`August, 1994a.
`Honeywell, “Permalloy Magnetic Sensors," Technical Note, 901XX, Honeywell
`Solid State Electronics Center. Plymouth, MN. September, I994b.
`[LC. Synchro Conversion Handbook. lLC Data Device Corporation. Bohemia,
`NY. April, 1982.
`
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`359
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`Kenny, T.W., Waltman, S.B., Reynolds. J.K., Kaiser. W1, “Micromachined
`Silicon Tunnel Sensor for Motion Detection.” Applied Physics letters, Vol.
`58, No. 1,January, 1991.
`Kim, N .H., Hawks, T., “Digital Compass and Magnetometer Having a Sensor
`Coil Wound on a High Permeability Isotropic Core,“ US Patent 4,851,775,
`25 July, 1989.
`KVH, C100 Compass Engine, Product Literature, KVI-I Industries, Middletown,
`RI, April, 1993.
`Kwiatkowski, W., Tumanski, S., “The Permalloy Magnetoresistive Sensors ,
`Properties and Applications.“ Journal of Physics E: Scientific Instruments,
`Vol. 19, pp. 502-515, 1986.
`Lao. R., “A New Wrinkle in Magnetoresistive Sensors," Sensors, pp. 63-65,
`October. 1994.
`Lenz, .T.E., “A Review of Magnetic Sensors,“ Proceedings oftne IEEE, Vol. 78,
`No. 6, June, 1990.
`Maenaka, K., Ohgusu, T., Ishida, M., Nakamura, T., “Novel Vertical Hall Cells
`in Standard Bipolar Technology," Electronic Letters, Vol. 23, pp.
`1 104-1 105,
`1987'.
`Maenaka, K., Tsukahara, M., and Nakamura, T., “Monolithic Silicon Magnetic
`Compass,” Sensors and Actuators, pp. 747—750, 1990.
`Petersen, A., "Magnetoresistive Sensors for Navigation,“ Proceedings, 7th
`International Conference on Automotive Electronics, London, England, pp.
`87-92, October, 1989.
`PNI, “TCMI Electronic Compass Module: User‘s Manual,“ Rev. 1.01, Precision
`Navigation. Inc., Mountain View. CA, March, 1994
`Primdabl. F., “The Fluxgatte Mechanism, Part I: The Gating Curves of Parallel
`and Orthogonal Fluxgates," IEEE Transactions on Magnetics, Vol. MAG-6,
`No. 2, June, 1970.
`Primdahl, F., “The Fluxgale Magnetometer,” Journal of Physics E: Scientific
`Instruments, Vol. 12, pp. 241-253, 1979.
`Rahim, W., “Feedback Limited Control System on a Skid-Steer Vehicle," ANS
`Fifth Topical Meeting on Robotics and Remote Systems, Knoxville, TN, Vol.
`1, pp. 37-42, April, 1993.
`Ramsden. E., "Measuring Magnetic Fields with Fluxgate Sensors,” Sensors, pp.
`37—90, September, 1994.
`SE1, "High-Sensitivity Magnetoresistive Magnelometer," Product Literature,
`MMSIOI, Space Electronics, Inc., San Diego, CA, June, 1994.
`Stuart, W.F., “Earth’s Field Magnetometry, Reports on Progress in Physics, J.M.
`Zinman, Editor, Vol. 35, Part 2, pp. 803-381, 1972.
`Udd, E., “Fiber Optic Sensors Based on the Sagnac Interferometer and Passive
`Ring Resonator," in Fiber Optic Sensors: An Introduction for Engineers and
`Scientists, E. Udd, Editor, John Wiley, New York, pp. 233-269, 1991.
`Wiley, C.M.. “Technical Review of Next Week’s National Electronics
`Conference," Electronics, p. 39-41, October 5, 1962.
`
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`Wiley, C.M.. “Navy Tries Solid—Slate Compass," Electronics, pp. 57-58.
`February 14, 1964.
`Wood. T., "Tth-Iall»Effect Sensor," Sermon, pp. 27-36. March. 1986.
`
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`13
`Gyroscopes
`
`insensitive to the electromagnetic and
`the most part
`Gyroscopes are for
`ferromagnetic anomalies that affect the accuracy of compasses and are particularly
`useful in applications where there is no geomagnetic field present at all (i.e., deep
`space), or in situations where the local field is disturbed. Two broad categories of
`gyroscopes will be discussed:
`1) mechanical gyroscopes and
`2} option!
`gyroscoper
`
`Mechanical gyroscope: Operate by sensing the change in direction of some
`actively sustained anguiar or linear momentum. which in either case can be
`continuous or oscillatory in nature (Cochin, I963). Probably the most well-known
`mechanical configuration is the flywheel gyroscope. a reliable orientation sensor
`based on the inertial properties of a rapidly spinning rotor. first demonstrated in
`1810 by G.C. Bohnenberger of Germany.
`In 1852. the French physicist Leon
`Foucault showed that such a gyroscope could detect
`the rotation of the earth
`(Carter. 1966). More recently there has be