CA1222880A - Two axis multisensor - Google Patents
Two axis multisensorInfo
- Publication number
- CA1222880A CA1222880A CA000464062A CA464062A CA1222880A CA 1222880 A CA1222880 A CA 1222880A CA 000464062 A CA000464062 A CA 000464062A CA 464062 A CA464062 A CA 464062A CA 1222880 A CA1222880 A CA 1222880A
- Authority
- CA
- Canada
- Prior art keywords
- sensors
- vibrating
- responsive
- acceleration
- linear acceleration
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Classifications
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01C—MEASURING DISTANCES, LEVELS OR BEARINGS; SURVEYING; NAVIGATION; GYROSCOPIC INSTRUMENTS; PHOTOGRAMMETRY OR VIDEOGRAMMETRY
- G01C19/00—Gyroscopes; Turn-sensitive devices using vibrating masses; Turn-sensitive devices without moving masses; Measuring angular rate using gyroscopic effects
- G01C19/56—Turn-sensitive devices using vibrating masses, e.g. vibratory angular rate sensors based on Coriolis forces
- G01C19/5719—Turn-sensitive devices using vibrating masses, e.g. vibratory angular rate sensors based on Coriolis forces using planar vibrating masses driven in a translation vibration along an axis
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01P—MEASURING LINEAR OR ANGULAR SPEED, ACCELERATION, DECELERATION, OR SHOCK; INDICATING PRESENCE, ABSENCE, OR DIRECTION, OF MOVEMENT
- G01P15/00—Measuring acceleration; Measuring deceleration; Measuring shock, i.e. sudden change of acceleration
- G01P15/02—Measuring acceleration; Measuring deceleration; Measuring shock, i.e. sudden change of acceleration by making use of inertia forces using solid seismic masses
- G01P15/08—Measuring acceleration; Measuring deceleration; Measuring shock, i.e. sudden change of acceleration by making use of inertia forces using solid seismic masses with conversion into electric or magnetic values
Landscapes
- Physics & Mathematics (AREA)
- General Physics & Mathematics (AREA)
- Engineering & Computer Science (AREA)
- Radar, Positioning & Navigation (AREA)
- Remote Sensing (AREA)
- Gyroscopes (AREA)
- Measuring Volume Flow (AREA)
Abstract
A two axis rate and linear acceleration detecting multisensor is formed by mounting a pair of accelerometers of the constrained mass type within a case. The accelerometers are mounted orthogonal to each other in vibratory units responsive to an electromagnet therebetween Rate is determined from the coriolis acceleration force experienced by the accelerometers which vibrate 180 degrees out of phase to minimize signal distortions resulting from transference of vibrational energy to the case and mountings.
Description
Page I ~ GCD 82-le TWO AXIS M~lLTISENSOR
BACKGR~UND OF THE DISCLOSURE
FIELD OF THE INVENTION
The present invention relates to inertial guidance instrumentation. More particularly, this invention pertains to multisensors for measuring both the linear acceleration and rate of rotation of a moving body.
A number of attempts have been made to utilizé an inertial mass to detect the rate of rotation of a bodyu Generally, such attempts have been based upon the coriolis acceleration experienced by a vibrating or rotating body fixed to a second body whose rotation is to be sensed. Coriolis acceleration is described by the following equation:
~ A = 2~ x v;
where: A = coriolis acceleration;
- angular rate of rotating coordinate system (second body) to be measured; and v ~ velocity component perpendicular to the axis of rotation.
.. .
As reEerenced above, the foregoing expresses the basic principle on which all vibratory gyros as well as spinning wheel gyros are based; namely, the acceleration experienced by a mass having a component of velocity perpendicular to the axis of rotation of the rotating coordinate system to which it is attached~ The sensing of angular rate with an oscillating pendulum was first demonstrated by Leon Foucault in the early 1850's. Since then a number of attempts have been made to apply coriolis acceleration principles tb the design of rate and rate integrating gyros.
Prominent among the attempts to develop a rate sensing ~; , , i ~22~880 ~CD-82-l~
p ,~ y ~
gyro in accordance with the foregoing principles have been the fGllo~ing ~all referred to by trademarlc name): "Gyrotron" of the Sperry Gyroscope Corporation (1940); the "A5 Gyro" of Royal Aircraft Establishment, the "Vibrating String Gyro" of ~orth American Rockwell Corporation (Au~onetics Division, Anaheim, California); "Viro" of the General Electric Corporation and the "Sonic Bell Gyro" of General Motors Corporation ~Delco Division).
All of the above-mentioned, with ~he exception of Gyrotron, began development in the early 1~60's.
In general, the above-narned systems rely upon either a rotating body or an unconstrained vibrating body to supply the velocity component v perpendicular to the axis of rotation of the second body. The acceleration force experienced by such rotating or vibrating body is then measured in some manner to provide the coriolis acceleration A. Knowing the coriolis acceleratioh and the velocity of a force-sensing element~ one can then simply determine the rate of rotation of the body.
Vibrating bodies offer obvious advantages over rotating assinblages in terms of mechanical simplicity. In order to arrange a rotatable inertial instrument having sensitivity to coriolis acceleration, such as an accelerometer, ball bearings~
slip rings, spin motors and the lilce must be provided~ Further, a rotational arrangement must be referenced in phase with the case in which it is mounted to resolve the input angular rate into two orthogonal sensitive axes.
Present day attempts to measure rotation via the use of a vibrating inertial sensor have been implemented by means of open loop vibrating mechanical systems in which the displacement of an unconstrained vibrating inertial mass upon experiencing coriolis acceleration generates an electrical signal proportional to the coriolis force. Such systems operate as tuning forks wherein the tines ~ibrate at frequency v and are deflected in a perpendicular plane by an amount ~roportional to A. Such systems, while less complex mechanically than rotating systems, have proven to be subject to inaccuracies resulting from the orthogonal movements required of the vibrating open loop forc~
~Z ~2 880 ~J GCD-B2-18 detecting mechanisms of the "vibrating string" variety.
SUMMARY OF THE INVE~TION
The foregoing and othee disadvantages of the prlor art are overcome by the present invention that provides apparatus for sensing both the rate of rotation and the linear acceleration o a body. Such apparatus includes constrained mass sensors responsive to linear acceleration along first and second preselected axes. Means are provided for arranging such sensors so that the first preselected axis is orthogonal to the second.
Means are further provided for vibrating the sensors. Means is further provided that is responsive to the coriolis acceleration forces exerted upon the sensors.
In a further aspect, the present invention provides a method for sensing the acceleration and the rate of rotation of a body. Such method includes the step of providing first and second constrained mass inertial sensors responsive to linear acceleration and arranging such sensors so that each is responsive to linear acceleration forces experienced by said body along orthogonal axes. The sensors are then vibrated at a preselected frequency and the linear and coriolis acceleration forces exerted upon the sensors are measured.
The invention will become further apparent from the following detailed description~ This description is accompanied by a set of drawing figures including a reference set of numerals, like numerals of the figures corresponding to like figures of the written description and like features of the invention throughout.
.. .
: . ,. : .
.
~_, Page ~ L2228~0 GCD-82-lB
B~IEF DESCRIPTION OF THE DRAWINGS
Figure 1 is a partial Vi~!W, in exploded perspective, that illustrates the relative arr~ngement of accelerometers in accordance with ~he invention; and Figure 2 is a side sectional view of a multisensor in accordance wi~h the invention.
DE~AILED DESCRIPTION
Turning now to the drawings, Figure 1 is an exploded pers~ective view of an essential portion of the invention, that pertaining to the preferred rela/l:ive orientations of the inertial force-sensing means that comprise the heart of multisensor. The force sensing means comprises an orthogonal arrangement of upper and lower accelerome~ers 10 and 1~ respectively. Each accelerometer is preferably of the force balance type in which a mass, such as a pendulous mass, is oriented to react to an acceleration force acting along a predetermined axis, known as its input axis. Unlike an open loop type of force detection mechanism, such mass is constrained by the action of reactive "forcers" so that, rather than effecting a measurable displacement, the force acting on the mass is a measurable function of the energy required to enable the forcers to maintain the null position of the mass as it experiences acceleration forces. The pickoff sensors, any of a number of conventional electro-mechanical transducers, produce resultant electrical signals proportional to ~he force ~acceleration) sensed by the reacti~e inertial mass within the accelerometer.
While a wide range of inertial acceleration-sensing instruments may be accomodated and function within the scope of the inYention, the apparatus as illustrated in Figure 1 utilizes two A4 MOD IV accelerometers of the pendulous, force balance type. This accelerometer is in production and presently available from Litton Systems, Inc. of Beverly Hills, Califor~a.
, ,~ : - .
.
i ~2;22~3~3C3 GC r~- 8 2 - l ~
ach of the upper and lower accelerometers lO and 12 is shown to be fixed to a corresponding upper or lower bracket 14, 16 comprising (in the instance oE th? illustrated lower bracket 16) a central backing member lB sandwiched between two transversely~
oriented flanges 20 and 22. The height of each overall bracket structure exceeds that the accelerometer fixed to it and each is mounted so that it extends both below and above such accelerometer. As will be seen, such arrangement allows the accelerometers to be mounted within the case of the mul~isensor in su~h a way that a suspension is effected, minimizing the possibility of deleterious mechanical feedback between accelerometer ~n~ case. Holes 24, 26, 2B, 30, 32, and~34 are provided within the elements of the bracket assemblage for bolts that secure bracket to accelerometer and to an armature/
diaphragm, disclosed in the following figure.
While the conventional inner workings of the accelerometers lO and 12 are not shown, input axes 36 and 38 define the orientations of sensitivity to acceleration forces.
Double headed arrows 40 and 42 in~icate the collinear directions of vibration of the accelerometers while rotation of the body to which the multisensor case is fixed is measured about the indicated orthogonal rotation-sensitive axes 44 and 45. Thus, referring back to the equation for coriolis acceleration, the system comprised of a multisensor in accordance with the invention is seen to impose a predetermined vibratory velocity v upon force-detecting accelerometers lO and 12 along collinear axes 40 and 42, sense orthogonal rotations ~ about accelerometer axes 44 and 46 an~ experience coriolis acceleration forces A
along input axes 36 and 380 Additionally, the multisensor system will, of course, detect non-coriolis induced linear acceleration forces along the input axes 36 and 38. Such accelerations can be dis~1nguished from the rate measuring coriolis forces by appropriate selection of the freauency of vibration of the accelerometers coupled ~ith convehtional demodulation techniques, discussod below.
_ GCD-&2-18 The functional system ~s illustrated and discussed above is shown fully implemented in Figure 2, a cross-section of the case 48 of a multisensor incorporating the teachings of the invention and including an assemblage within that as shown in the preceding figure. The instrumentation within the cylindrical case 48 is essentially orthogo-symmetrical about a horizontal axis 50; that is, corresponding elements of the instrumentation abo~e the axis 50 are rotated by ninety degrees from those below the line. This is shown clearly, of course, in the preceding figure.
Covers 52 and 54 seal the multisensor. As is seen in Figure 2~ the bracket 14 securing the upper aecelerometer 10 includes a central backing member 56 joined to transverseley-oriented flanges 5~ and 60.
Each accelerometer-and-bracket assembly is bolted at top and bo~tom to a substantially disc-shaped diaphragm/armature having reinforced center and edge portions separated by a relatively thin annular diaphragm formed therewith to form independent double diaphragm suspensions both above and below the horizontal axis 50. Armature/diaphragms 62 and 64 are bolted to, and supply the sole support of, the upper bracket-and-accelerometer assembly while armature/diaphragms 66 and 58 provide the sole support for the lower bracket-and-accelerometer assembly.
Cylindrical spacers 70 ~nd 72 separate the edges of the armature/diaphragms, completing a pair of independent vibratory units within the case 48, the upper vibratory unit comprising upper accelerometer lO and-bracket assembly sandwiched between armature/diaphragms 62 and 64 and surrounded by the cylindrical spacer 70 and the lower vibratory unit comprising lower accelerometer 12-and-bracket assembly sandwiched between armature/diaphragms 66 and 68 and surrounded by the cylindrical spacer 72.
An electromagnet 74 is positioned in the center of the case 48 by means of an inwardly-extending radia] flange 75 and cup 78 formed therewith. A conventional acceleration restoring ~_ Page 7 1~28~30 G~ D- ~ 2 -1~
amplifier ~0 mounted on thP Elang~ 76 receives pickofE sign~ls c~eneratecl within th2 accelerometers and, in response, provides ccritrol signals to forcers within the acceleromcters that act upon the pendulous mass. Th~ necessary conductors for the aforesaid are not shown in Figure 2; however, electrical communication is provided exterior to the multisensor by means, of upper and lo~er con~uctors 82 and ~4 which are in electrical communication with the sensing apparatus of the upper and lower accelerometers 10 and 12 respectively through soldered contact pads a6 and 88. Each conductor includes six individual conducitors; one pair of conductors relates to the excitation oF
the light emitting dio~e portion oE the pickoff sensor; another pair is associated with the oucput of the photodiode portion of the pickofE; and the third pair provides current to the accelerometer forcer mechanism~
The electrornagnet 74 drives the upper and lower double-diaphragm vibratorv units ~efined above by actjvatinS and deactivating electromagnetic fields which alternately attract and release the diaphragms 64 and 66. As a consequence of the driving of the diaphragmsl the vibratory units, including associated a_celerometers, are ca~sed to oscillate in the vertical plane. Further, in accordance with the positioning of the electromagnet 74 between the diaphragms 54 and 66 the two units, and associated accelerometeLs, vibrate out of phase by 1~0 degrees. By vibrating out of phase, the units, each having identical resonant feequencies, exert egual and opposite vibrational forces thereby minimizin~ the vibrational energy coupled to the case 48 to avoid mounting sensitivities.
The output of each accelerometer is a signal containing both rate information and linear acceleration (along each accelerometer's input axis) information. ~he in3ividual ~emodulation of the two ty~es of information is relatively strai3htforward as a consequence of the differing frequencies of the rate of rotation and acceleration signals. The output rate information is modulated at the preselected freguency of accelerometer vibration while linear acceleration of interestjcan be expected to be elther constant or to lie within a relatively ~:2;~ GC D~ ~ 2 - 1 8 Page 8 ~' low and predictable frequency ran~e. The frequency of vibration of the douhle diaphragm suspensions is chosen to be high relative to system bandwidth requirements to permit the filtering of the modulated rate signal from the accelerometer output. Angular rate information is obtained by capacitively coupling the accelerometer output to a bandpass amplifier cen~ered about the modulation frequency. The output of the bandpass amplifier is appl'ed to the input of the demodulator, the reference signal for the demodulator being chosen to be in phase with the velocity oE
the vibrating unit. The output of the demodulator is then filtered to provide a d.c, voltage proportional in amplitude to the angular rate applied with polarity sensitive to direction of applied angular rate.
Thus it is sQen that there has been provided to the inertial instrumentation art new and improved apparatus that is capable of measuring rotation in two orthogonal planes and acceleration in two orthogonal directions~ By incorporating a multisensor in accordance with the invention, one is able to obtain the advantages of a vibratory apparatus in terms of lesser complexity than that obtainable with a rotary oscillatory arrangement while avoiding the inherent drawbacks of former vibrating arrangements.
While the invention has been described ln its presently preferred embodiment, its scope is not to be so limited. Rather the invention is intended to encompass that defined in the fo:Llowing set of claims and all e~uivalents thereof.
_ .. _ _ _ .. , . . . . , ., , .. . .. . . . _ . ~
BACKGR~UND OF THE DISCLOSURE
FIELD OF THE INVENTION
The present invention relates to inertial guidance instrumentation. More particularly, this invention pertains to multisensors for measuring both the linear acceleration and rate of rotation of a moving body.
A number of attempts have been made to utilizé an inertial mass to detect the rate of rotation of a bodyu Generally, such attempts have been based upon the coriolis acceleration experienced by a vibrating or rotating body fixed to a second body whose rotation is to be sensed. Coriolis acceleration is described by the following equation:
~ A = 2~ x v;
where: A = coriolis acceleration;
- angular rate of rotating coordinate system (second body) to be measured; and v ~ velocity component perpendicular to the axis of rotation.
.. .
As reEerenced above, the foregoing expresses the basic principle on which all vibratory gyros as well as spinning wheel gyros are based; namely, the acceleration experienced by a mass having a component of velocity perpendicular to the axis of rotation of the rotating coordinate system to which it is attached~ The sensing of angular rate with an oscillating pendulum was first demonstrated by Leon Foucault in the early 1850's. Since then a number of attempts have been made to apply coriolis acceleration principles tb the design of rate and rate integrating gyros.
Prominent among the attempts to develop a rate sensing ~; , , i ~22~880 ~CD-82-l~
p ,~ y ~
gyro in accordance with the foregoing principles have been the fGllo~ing ~all referred to by trademarlc name): "Gyrotron" of the Sperry Gyroscope Corporation (1940); the "A5 Gyro" of Royal Aircraft Establishment, the "Vibrating String Gyro" of ~orth American Rockwell Corporation (Au~onetics Division, Anaheim, California); "Viro" of the General Electric Corporation and the "Sonic Bell Gyro" of General Motors Corporation ~Delco Division).
All of the above-mentioned, with ~he exception of Gyrotron, began development in the early 1~60's.
In general, the above-narned systems rely upon either a rotating body or an unconstrained vibrating body to supply the velocity component v perpendicular to the axis of rotation of the second body. The acceleration force experienced by such rotating or vibrating body is then measured in some manner to provide the coriolis acceleration A. Knowing the coriolis acceleratioh and the velocity of a force-sensing element~ one can then simply determine the rate of rotation of the body.
Vibrating bodies offer obvious advantages over rotating assinblages in terms of mechanical simplicity. In order to arrange a rotatable inertial instrument having sensitivity to coriolis acceleration, such as an accelerometer, ball bearings~
slip rings, spin motors and the lilce must be provided~ Further, a rotational arrangement must be referenced in phase with the case in which it is mounted to resolve the input angular rate into two orthogonal sensitive axes.
Present day attempts to measure rotation via the use of a vibrating inertial sensor have been implemented by means of open loop vibrating mechanical systems in which the displacement of an unconstrained vibrating inertial mass upon experiencing coriolis acceleration generates an electrical signal proportional to the coriolis force. Such systems operate as tuning forks wherein the tines ~ibrate at frequency v and are deflected in a perpendicular plane by an amount ~roportional to A. Such systems, while less complex mechanically than rotating systems, have proven to be subject to inaccuracies resulting from the orthogonal movements required of the vibrating open loop forc~
~Z ~2 880 ~J GCD-B2-18 detecting mechanisms of the "vibrating string" variety.
SUMMARY OF THE INVE~TION
The foregoing and othee disadvantages of the prlor art are overcome by the present invention that provides apparatus for sensing both the rate of rotation and the linear acceleration o a body. Such apparatus includes constrained mass sensors responsive to linear acceleration along first and second preselected axes. Means are provided for arranging such sensors so that the first preselected axis is orthogonal to the second.
Means are further provided for vibrating the sensors. Means is further provided that is responsive to the coriolis acceleration forces exerted upon the sensors.
In a further aspect, the present invention provides a method for sensing the acceleration and the rate of rotation of a body. Such method includes the step of providing first and second constrained mass inertial sensors responsive to linear acceleration and arranging such sensors so that each is responsive to linear acceleration forces experienced by said body along orthogonal axes. The sensors are then vibrated at a preselected frequency and the linear and coriolis acceleration forces exerted upon the sensors are measured.
The invention will become further apparent from the following detailed description~ This description is accompanied by a set of drawing figures including a reference set of numerals, like numerals of the figures corresponding to like figures of the written description and like features of the invention throughout.
.. .
: . ,. : .
.
~_, Page ~ L2228~0 GCD-82-lB
B~IEF DESCRIPTION OF THE DRAWINGS
Figure 1 is a partial Vi~!W, in exploded perspective, that illustrates the relative arr~ngement of accelerometers in accordance with ~he invention; and Figure 2 is a side sectional view of a multisensor in accordance wi~h the invention.
DE~AILED DESCRIPTION
Turning now to the drawings, Figure 1 is an exploded pers~ective view of an essential portion of the invention, that pertaining to the preferred rela/l:ive orientations of the inertial force-sensing means that comprise the heart of multisensor. The force sensing means comprises an orthogonal arrangement of upper and lower accelerome~ers 10 and 1~ respectively. Each accelerometer is preferably of the force balance type in which a mass, such as a pendulous mass, is oriented to react to an acceleration force acting along a predetermined axis, known as its input axis. Unlike an open loop type of force detection mechanism, such mass is constrained by the action of reactive "forcers" so that, rather than effecting a measurable displacement, the force acting on the mass is a measurable function of the energy required to enable the forcers to maintain the null position of the mass as it experiences acceleration forces. The pickoff sensors, any of a number of conventional electro-mechanical transducers, produce resultant electrical signals proportional to ~he force ~acceleration) sensed by the reacti~e inertial mass within the accelerometer.
While a wide range of inertial acceleration-sensing instruments may be accomodated and function within the scope of the inYention, the apparatus as illustrated in Figure 1 utilizes two A4 MOD IV accelerometers of the pendulous, force balance type. This accelerometer is in production and presently available from Litton Systems, Inc. of Beverly Hills, Califor~a.
, ,~ : - .
.
i ~2;22~3~3C3 GC r~- 8 2 - l ~
ach of the upper and lower accelerometers lO and 12 is shown to be fixed to a corresponding upper or lower bracket 14, 16 comprising (in the instance oE th? illustrated lower bracket 16) a central backing member lB sandwiched between two transversely~
oriented flanges 20 and 22. The height of each overall bracket structure exceeds that the accelerometer fixed to it and each is mounted so that it extends both below and above such accelerometer. As will be seen, such arrangement allows the accelerometers to be mounted within the case of the mul~isensor in su~h a way that a suspension is effected, minimizing the possibility of deleterious mechanical feedback between accelerometer ~n~ case. Holes 24, 26, 2B, 30, 32, and~34 are provided within the elements of the bracket assemblage for bolts that secure bracket to accelerometer and to an armature/
diaphragm, disclosed in the following figure.
While the conventional inner workings of the accelerometers lO and 12 are not shown, input axes 36 and 38 define the orientations of sensitivity to acceleration forces.
Double headed arrows 40 and 42 in~icate the collinear directions of vibration of the accelerometers while rotation of the body to which the multisensor case is fixed is measured about the indicated orthogonal rotation-sensitive axes 44 and 45. Thus, referring back to the equation for coriolis acceleration, the system comprised of a multisensor in accordance with the invention is seen to impose a predetermined vibratory velocity v upon force-detecting accelerometers lO and 12 along collinear axes 40 and 42, sense orthogonal rotations ~ about accelerometer axes 44 and 46 an~ experience coriolis acceleration forces A
along input axes 36 and 380 Additionally, the multisensor system will, of course, detect non-coriolis induced linear acceleration forces along the input axes 36 and 38. Such accelerations can be dis~1nguished from the rate measuring coriolis forces by appropriate selection of the freauency of vibration of the accelerometers coupled ~ith convehtional demodulation techniques, discussod below.
_ GCD-&2-18 The functional system ~s illustrated and discussed above is shown fully implemented in Figure 2, a cross-section of the case 48 of a multisensor incorporating the teachings of the invention and including an assemblage within that as shown in the preceding figure. The instrumentation within the cylindrical case 48 is essentially orthogo-symmetrical about a horizontal axis 50; that is, corresponding elements of the instrumentation abo~e the axis 50 are rotated by ninety degrees from those below the line. This is shown clearly, of course, in the preceding figure.
Covers 52 and 54 seal the multisensor. As is seen in Figure 2~ the bracket 14 securing the upper aecelerometer 10 includes a central backing member 56 joined to transverseley-oriented flanges 5~ and 60.
Each accelerometer-and-bracket assembly is bolted at top and bo~tom to a substantially disc-shaped diaphragm/armature having reinforced center and edge portions separated by a relatively thin annular diaphragm formed therewith to form independent double diaphragm suspensions both above and below the horizontal axis 50. Armature/diaphragms 62 and 64 are bolted to, and supply the sole support of, the upper bracket-and-accelerometer assembly while armature/diaphragms 66 and 58 provide the sole support for the lower bracket-and-accelerometer assembly.
Cylindrical spacers 70 ~nd 72 separate the edges of the armature/diaphragms, completing a pair of independent vibratory units within the case 48, the upper vibratory unit comprising upper accelerometer lO and-bracket assembly sandwiched between armature/diaphragms 62 and 64 and surrounded by the cylindrical spacer 70 and the lower vibratory unit comprising lower accelerometer 12-and-bracket assembly sandwiched between armature/diaphragms 66 and 68 and surrounded by the cylindrical spacer 72.
An electromagnet 74 is positioned in the center of the case 48 by means of an inwardly-extending radia] flange 75 and cup 78 formed therewith. A conventional acceleration restoring ~_ Page 7 1~28~30 G~ D- ~ 2 -1~
amplifier ~0 mounted on thP Elang~ 76 receives pickofE sign~ls c~eneratecl within th2 accelerometers and, in response, provides ccritrol signals to forcers within the acceleromcters that act upon the pendulous mass. Th~ necessary conductors for the aforesaid are not shown in Figure 2; however, electrical communication is provided exterior to the multisensor by means, of upper and lo~er con~uctors 82 and ~4 which are in electrical communication with the sensing apparatus of the upper and lower accelerometers 10 and 12 respectively through soldered contact pads a6 and 88. Each conductor includes six individual conducitors; one pair of conductors relates to the excitation oF
the light emitting dio~e portion oE the pickoff sensor; another pair is associated with the oucput of the photodiode portion of the pickofE; and the third pair provides current to the accelerometer forcer mechanism~
The electrornagnet 74 drives the upper and lower double-diaphragm vibratorv units ~efined above by actjvatinS and deactivating electromagnetic fields which alternately attract and release the diaphragms 64 and 66. As a consequence of the driving of the diaphragmsl the vibratory units, including associated a_celerometers, are ca~sed to oscillate in the vertical plane. Further, in accordance with the positioning of the electromagnet 74 between the diaphragms 54 and 66 the two units, and associated accelerometeLs, vibrate out of phase by 1~0 degrees. By vibrating out of phase, the units, each having identical resonant feequencies, exert egual and opposite vibrational forces thereby minimizin~ the vibrational energy coupled to the case 48 to avoid mounting sensitivities.
The output of each accelerometer is a signal containing both rate information and linear acceleration (along each accelerometer's input axis) information. ~he in3ividual ~emodulation of the two ty~es of information is relatively strai3htforward as a consequence of the differing frequencies of the rate of rotation and acceleration signals. The output rate information is modulated at the preselected freguency of accelerometer vibration while linear acceleration of interestjcan be expected to be elther constant or to lie within a relatively ~:2;~ GC D~ ~ 2 - 1 8 Page 8 ~' low and predictable frequency ran~e. The frequency of vibration of the douhle diaphragm suspensions is chosen to be high relative to system bandwidth requirements to permit the filtering of the modulated rate signal from the accelerometer output. Angular rate information is obtained by capacitively coupling the accelerometer output to a bandpass amplifier cen~ered about the modulation frequency. The output of the bandpass amplifier is appl'ed to the input of the demodulator, the reference signal for the demodulator being chosen to be in phase with the velocity oE
the vibrating unit. The output of the demodulator is then filtered to provide a d.c, voltage proportional in amplitude to the angular rate applied with polarity sensitive to direction of applied angular rate.
Thus it is sQen that there has been provided to the inertial instrumentation art new and improved apparatus that is capable of measuring rotation in two orthogonal planes and acceleration in two orthogonal directions~ By incorporating a multisensor in accordance with the invention, one is able to obtain the advantages of a vibratory apparatus in terms of lesser complexity than that obtainable with a rotary oscillatory arrangement while avoiding the inherent drawbacks of former vibrating arrangements.
While the invention has been described ln its presently preferred embodiment, its scope is not to be so limited. Rather the invention is intended to encompass that defined in the fo:Llowing set of claims and all e~uivalents thereof.
_ .. _ _ _ .. , . . . . , ., , .. . .. . . . _ . ~
Claims (8)
1. A multisensor responsive to the linear acceleration and rate of rotation of a body comprising, in combination:
a) a constrained mass sensor responsive to linear acceleration along a first pleselected axis;
b) a constrained mass sensor responsive to linear acceleration along a second preselected axis;
c) means for arranging said constrained mass sensors so that said first preselected axis is orthogonal to said second preselected axis;
d) means for vibrating said sensors; and e) means responsive to the coriolis acceleration forces exerted upon said sensors.
a) a constrained mass sensor responsive to linear acceleration along a first pleselected axis;
b) a constrained mass sensor responsive to linear acceleration along a second preselected axis;
c) means for arranging said constrained mass sensors so that said first preselected axis is orthogonal to said second preselected axis;
d) means for vibrating said sensors; and e) means responsive to the coriolis acceleration forces exerted upon said sensors.
2. Apparatus as defined in Claim 1 further characterized in that:
a) said sensors responsive to linear acceleration comprise a first accelerometer and a second accelerometer; and b) said means for arranging comprises a pair of double diaphragm suspensions.
a) said sensors responsive to linear acceleration comprise a first accelerometer and a second accelerometer; and b) said means for arranging comprises a pair of double diaphragm suspensions.
3. Apparatus as defined in Claim 2 wherein said means for vibrating is arranged so that said sensors are vibrated out-of-phase.
4. Apparatus as defined in Claim 3 wherein said means for vibrating includes an electromagnet mounted intermediate said pair of double diaphragm suspensions.
5. Apparatus as defined in Claim 4 wherein the vibration frequency of said double diaphragm suspensions is high relative to system bandwidth.
6. Apparatus as defined in Claim 5 wherein said first and second accelerometers are A4 MOD IVs.
7. A method for sensing the rate of rotation and acceleration of a body comprising the steps of:
a) providing first and second constrained mass inertial sensors responsive to linear acceleration forces; and b) arranging said first and second sensors with respect to said body so that each is responsive to linear acceleration forces experienced by said body along orthogonal axes; then c) vibrating said first and second sensors at a preselected frequency; and d) measuring the linear and coriolis acceleration forces exerted upon each of said constrained mass inertial sensors.
a) providing first and second constrained mass inertial sensors responsive to linear acceleration forces; and b) arranging said first and second sensors with respect to said body so that each is responsive to linear acceleration forces experienced by said body along orthogonal axes; then c) vibrating said first and second sensors at a preselected frequency; and d) measuring the linear and coriolis acceleration forces exerted upon each of said constrained mass inertial sensors.
8. A method as defined in Claim 7 wherein the vibrating step further comprises the step of vibrating said first and second sensors out-of-phase.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US55805583A | 1983-12-05 | 1983-12-05 | |
| US558,055 | 1983-12-05 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1222880A true CA1222880A (en) | 1987-06-16 |
Family
ID=24228010
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000464062A Expired CA1222880A (en) | 1983-12-05 | 1984-09-26 | Two axis multisensor |
Country Status (8)
| Country | Link |
|---|---|
| JP (1) | JPS60135815A (en) |
| CA (1) | CA1222880A (en) |
| DE (1) | DE3444142A1 (en) |
| FR (1) | FR2556100B1 (en) |
| GB (1) | GB2151022B (en) |
| IT (1) | IT1178446B (en) |
| NO (1) | NO844244L (en) |
| SE (1) | SE457189B (en) |
Families Citing this family (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CA1217648A (en) * | 1984-01-23 | 1987-02-10 | Robert E. Stewart | Single axis multisensor |
| US4744249A (en) * | 1985-07-25 | 1988-05-17 | Litton Systems, Inc. | Vibrating accelerometer-multisensor |
| DE3702824A1 (en) * | 1987-01-30 | 1988-08-11 | Bayerische Motoren Werke Ag | Acceleration pick up |
| US4782700A (en) * | 1987-07-17 | 1988-11-08 | Sundstrand Data Control, Inc. | Frame assembly and dither drive for a coriolis rate sensor |
| US4821572A (en) * | 1987-11-25 | 1989-04-18 | Sundstrand Data Control, Inc. | Multi axis angular rate sensor having a single dither axis |
| DE4335219B4 (en) * | 1993-10-15 | 2004-06-03 | Robert Bosch Gmbh | Rotation rate sensor and method for producing a rotation rate sensor |
| GB2300047B (en) * | 1995-04-19 | 1999-04-14 | Smiths Industries Plc | Inertial sensor assemblies |
| US5880368A (en) * | 1995-04-19 | 1999-03-09 | Smiths Industries Public Limited Company | Inertial sensors |
Family Cites Families (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3206986A (en) * | 1963-01-04 | 1965-09-21 | Western Electric Co | Apparatus for sensing selected movements of a body |
| US3744322A (en) * | 1970-12-07 | 1973-07-10 | Space Res Corp | Angular velocity sensors |
| US4512192A (en) * | 1983-09-02 | 1985-04-23 | Sundstrand Data Control, Inc. | Two axis angular rate and specific force sensor utilizing vibrating accelerometers |
-
1984
- 1984-09-26 CA CA000464062A patent/CA1222880A/en not_active Expired
- 1984-10-18 FR FR8415975A patent/FR2556100B1/en not_active Expired
- 1984-10-24 NO NO844244A patent/NO844244L/en unknown
- 1984-11-02 GB GB08427822A patent/GB2151022B/en not_active Expired
- 1984-11-26 JP JP59248291A patent/JPS60135815A/en active Pending
- 1984-12-04 IT IT49241/84A patent/IT1178446B/en active
- 1984-12-04 DE DE19843444142 patent/DE3444142A1/en active Granted
- 1984-12-05 SE SE8406148A patent/SE457189B/en not_active IP Right Cessation
Also Published As
| Publication number | Publication date |
|---|---|
| DE3444142C2 (en) | 1990-11-29 |
| GB8427822D0 (en) | 1984-12-12 |
| GB2151022B (en) | 1988-04-07 |
| IT8449241A0 (en) | 1984-12-04 |
| DE3444142A1 (en) | 1985-07-11 |
| SE8406148D0 (en) | 1984-12-05 |
| JPS60135815A (en) | 1985-07-19 |
| FR2556100B1 (en) | 1989-01-13 |
| NO844244L (en) | 1985-06-06 |
| IT1178446B (en) | 1987-09-09 |
| SE457189B (en) | 1988-12-05 |
| GB2151022A (en) | 1985-07-10 |
| SE8406148L (en) | 1985-06-06 |
| FR2556100A1 (en) | 1985-06-07 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| US4744248A (en) | Vibrating accelerometer-multisensor | |
| US4744249A (en) | Vibrating accelerometer-multisensor | |
| US4381672A (en) | Vibrating beam rotation sensor | |
| US4930351A (en) | Vibratory linear acceleration and angular rate sensing system | |
| US5987986A (en) | Navigation grade micromachined rotation sensor system | |
| US4841773A (en) | Miniature inertial measurement unit | |
| US4590801A (en) | Apparatus for measuring inertial specific force and angular rate of a moving body | |
| CA1215244A (en) | Two axis angular rate and specific force sensor utilizing vibrating accelerometers | |
| US3486383A (en) | Vibrating beam transducer | |
| US5428995A (en) | Counterbalanced vibratory triaxial angular rate sensor with open loop output | |
| US6557415B2 (en) | Counterbalanced silicon tuned multiple accelerometer-gyro | |
| US5007289A (en) | Three axis inertial measurement unit with counterbalanced, low inertia mechanical oscillator | |
| JPH06510604A (en) | rotation sensor | |
| US5168756A (en) | Dithering coriolis rate and acceleration sensor utilizing a permanent magnet | |
| CA1222880A (en) | Two axis multisensor | |
| US20020104378A1 (en) | Micromachined silicon gyro using tuned accelerometer | |
| EP0586437A1 (en) | Improvements in or relating to gyroscopic devices. | |
| CA1117786A (en) | Angular accelerometer stabilized pendulum | |
| US3413859A (en) | Digital rate gyro | |
| CA1217648A (en) | Single axis multisensor | |
| CA2195667C (en) | Two axis navigation grade micromachined rotation sensor system | |
| US5339690A (en) | Apparatus for measuring the rate of rotation and linear accelleration of a moving body in two perpendicular axes | |
| US4445375A (en) | Tuned coriolis angular rate measuring device | |
| NO843479L (en) | APPARATUS FOR AA MAKING A SIGNAL REPRESENTING THE ANGLE MOVEMENT SPEED OF A CONSTRUCTION |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |