CA1167669A - Inertial platforms - Google Patents
Inertial platformsInfo
- Publication number
- CA1167669A CA1167669A CA000384629A CA384629A CA1167669A CA 1167669 A CA1167669 A CA 1167669A CA 000384629 A CA000384629 A CA 000384629A CA 384629 A CA384629 A CA 384629A CA 1167669 A CA1167669 A CA 1167669A
- Authority
- CA
- Canada
- Prior art keywords
- gimbal
- axis
- platform
- sensitive
- sensitive axes
- 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
- G01C21/00—Navigation; Navigational instruments not provided for in groups G01C1/00 - G01C19/00
- G01C21/10—Navigation; Navigational instruments not provided for in groups G01C1/00 - G01C19/00 by using measurements of speed or acceleration
- G01C21/12—Navigation; Navigational instruments not provided for in groups G01C1/00 - G01C19/00 by using measurements of speed or acceleration executed aboard the object being navigated; Dead reckoning
- G01C21/16—Navigation; Navigational instruments not provided for in groups G01C1/00 - G01C19/00 by using measurements of speed or acceleration executed aboard the object being navigated; Dead reckoning by integrating acceleration or speed, i.e. inertial navigation
- G01C21/18—Stabilised platforms, e.g. by gyroscope
Landscapes
- Engineering & Computer Science (AREA)
- Radar, Positioning & Navigation (AREA)
- Remote Sensing (AREA)
- Automation & Control Theory (AREA)
- Physics & Mathematics (AREA)
- General Physics & Mathematics (AREA)
- Gyroscopes (AREA)
- Navigation (AREA)
Abstract
A B S T R A C T
An inertial platform comprises a frame secured to a vehicle, an outer gimbal supported by the frame, and a second gimbal supported by the first gimbal. The two gimbal axes are perpendicular, and each have a pick-off and a torque motor.
Gyroscopic means are carried on the inner gimbal and have three mutually perpendicular sensitive axes. Circuit means are provided which ensure that, in operation, the inner gimbal is maintained in an attitude in which first and second sensitive axes are horizontal and the third sensitive axis is vertical. Accelerometers are carried on the inner gimbal.
An inertial platform comprises a frame secured to a vehicle, an outer gimbal supported by the frame, and a second gimbal supported by the first gimbal. The two gimbal axes are perpendicular, and each have a pick-off and a torque motor.
Gyroscopic means are carried on the inner gimbal and have three mutually perpendicular sensitive axes. Circuit means are provided which ensure that, in operation, the inner gimbal is maintained in an attitude in which first and second sensitive axes are horizontal and the third sensitive axis is vertical. Accelerometers are carried on the inner gimbal.
Description
~ ~67669 Inertial Platforms M~ny types of inertial platforms exist, each different type being intended to operate under a particular set of conditions. At one extreme is the pLItform having three, or probably four, gimbals and carrying on the inner gimbal the gyros ne oe ssary for stabilisation and a set of acceler eters.
m is type of platform is very camplex and expensive from a mechanical viewpoint, requiring slip-ring connections, and gimbal bearings, and being of increased size and weight. The other extreme is the so-called "strapdown" system in which the gyros and accelerometers are fixed rigidly to the vehicle frame.
This arrangement is more robust and is simpler mechanically, but the computing complexity is cQnsiderably greater.
Neither of the two alternatives described above is particularly cheap, and there is a requirement for a simple law-cost inertial platform. It is an object of the present invention to provide such a platform.
According to the present invention there is provided an inertial platform which includes a frame arranged to be secured to a vehicle, an outer gimbal supported from the frame about a first gimbal axis, an inner gimbal sup-ported from the outer gimbal about a secand gimbal axis perpendicular to the first gimbal axis, a pickoff and a torque motor on each gimbal axis, gyroscopic means mounted rigidly on the inner gimbal and having three mutually perpendicu-lar sensitive axes, circuit means respQnsive to outputs from the pickoffs and from the gyroscopic apparatus when the platform is in operation to maintain the inner gimbal in an attitude in which first and second sensitive axes of the gyroscopic means are horizontal and the third sensitive axis is vertical, and a numker of accelerometers carried Qn the inner gimbal and having sensitive axes parallel to some or all of the sensitive axes of the gyroscopic means.
.~ ~
~ i67669 T~e invention ~ill now be described with reference to the accompanying drawings, in which:-Figure 1 is a schematic view of a platform, showing an arrangement of the hardware;
Figure 2 is a block circuit diagram of the circuit means and other components of the platform; and Figure 3 illustrates the operation of the ciruit means.
Referring now to Figure 1, a frame fixed rigidly to the vehicle and shown schematically at lO supports an outer gimbal 11 for rotation about an axis 12. The outer gimbal is provided with a pickoff 13 and a torque motor 14 for controlling its attitude relative to the frame 10. The outer gimbal 11 supports an inner gimbal 15 for rotation about an axis 16 which is perpendicular to the axis 12. The inner gimbal i9 provided with a pickoff 17 and a torque motor 18 for controlling its attitude relative to the outer gimbal 11.
The inner gimbal 15 forms a platform on which are mounted gyroscopes, or gyros, having three sensitive axes.
As shown in Figure 1, a first gyro 19 has two mutually perpendicular sensitive axes both of which are parallel to the plane of the inner gimbal 15. A second gyro 20 has its single sensitive axis arranged perpendicular to the two sensitive axes of gyro 19. Each gyro has the usual pickoff and torquer on each sensitive axis.
Also carried on the inner gimbal are the accelerometers required to provide outputs from the platform. Two accelerometers 21 and 22 are shown, having their sensitive axes aligned with those of the two-axis gyro 19.
The various electrical connections to and from the platform are shown schematically in Figure 2 in which a block diagram of the necessary circuit means to which these connections are supplied.
~ 3 ~ `116766~
Pickoff signals from the 2-axis gyro 19 are applied to separate servo amplifiers 30 and 31. The outputs from these amplifiers are applied to the torque motors 14 and 18 on the inner and outer gimbal axes respecively. The outputs from the corresponding gimbal pickoffs 13 and 17 are applied to a central processor 32 which derives pitch and roll outputs. The processor also provides outputs to the torquers on the two axes of the gyro 19.
The second gyro 20 has its pickoff and torquer connected in a conventional capture loop. The pickoff output is connected through 2 capture amplifier 33 to an integrating encoder 34. The output from the encoder is applied both to the processor 32 and to the torquer of the gyro 20.
The two accelerometers are connected in a similar way to gyro 20. The output of accelerometer 21 is applied through a capture amplifier 35 to an integrating encoder 36.
The encoder output is applied to the processor 32 and to the force coil of the accelerometer. Similarly, the pickoff output from accelerometer 22 is applied through a capture amplifier 37 to an integrating encoder 38. The output of the encoder is applied to the processor 32 and to the force coil of the accelerometer 22.
The function of the processor 32 is illustrated schematically in Figure 3, This drawing shows the inputs to and outputs from the processor shown in Figure 2, and indicates the functions to be performed. Many of these are conventional to the inertial platform field and need not be described in detail. The function may be performed by hardware or by software.
Referring to Figure 3, the pickoff output from the gyro 20 of Figure 2 is applied to a capture amplifier 37 and integrator 38, and this integrator produces an output which represents increments of azimuth angle of the platform relative to some datum. This signal is applied via an input A to the processor to a further integrator 40, the output of ~ 4 ~ ~ 167669 which represents the absolute platform azimuth angle, or heading H. A correction signal is applied to the integrator 40 as will be described later.
The two accelerometers 21 and 22 of Figure 2 also have capture loops containing integrators, and the outputs of these integrators are applied to inputs B and C of the processor. Assuming the axes 12 and 16 of Figure 1 to represent the X and Y direction respectively then the output of integrator 36 applied to input B represents increments of X velocity, whilst the output of integrstor 34 applied to input C represents increments of Y velocity. Further integrators 41 and 42 produce outputs representing total velocity in the X and Y directions. These are modified by azimuth resolver 43 which produces output representing North and East velocities. The resolver 43 has an input from the integrator 40, and thus effects a continuous transformation on the X and Y velocities applied to it in dependence upon the heading of the platform.
The North and East velocities from resolver 43 are applied to a conventional Schuler loop circuit 44 which produces output signals representing latitude LA and longitude L0, as well as the North and East velocities ~V and EV. Inputs CR to tbe Schuler loop circuit 44 may provide corrections for gyro drift, instrument bias etc, and an output from the circuit provides the azimuth rate corrections for the integrator 40 already mentioned. These corrections are conventional, and relate to the earth's rate and velocity.
Outputs from the processor are required for the torquer of the accelerometer 19 of Figure 1, and these are obtained at D
and E. These are derived from the Schuler loop circuit 43 by way of a further azimuth resolver 45, performing the reverse function to the resolver 43. Resolver 45 derives from the corrected Schuler loop output the necessary X and Y gyro torquing signals.
- 5 - 116~66~
Signals from the two gimbal pickoffs 13 and 17 are applied to inputs F and G of the processor. These are applied to a third resol~er 46 along with a fixed quantity representing the angle in the horizontal plane between the platform XY axes and the pitch-roll axes from integrator 4.
This resolver converts the X and Y outputs from the pickoffs into pitch and roll angle outputs from the processor.
The three resolvers and the Schuler loop circuit perform fairly simple transformation operations of a type which are well-known in the inertial navigation field. Such transformations are explained in detail in a number of reference books and will not therefore be described further.
As already stated, the functions of the processor may be provided by circuitry or by programming. The desired results may be obtained by different methods to those described. The three sensitive gyro axes may be provided by three separate single-axis gyros, or by two two-axis gyros with one redundant axis. A third accelerometer could be provided if required. The two gimbal pickoffs 13 and 17 are only necesgary if the platform is required to give outputs indicating pitch and roll angle. The processor could be used to resolve the X and Y velocity increments rather than operating on the integrated increments.
m is type of platform is very camplex and expensive from a mechanical viewpoint, requiring slip-ring connections, and gimbal bearings, and being of increased size and weight. The other extreme is the so-called "strapdown" system in which the gyros and accelerometers are fixed rigidly to the vehicle frame.
This arrangement is more robust and is simpler mechanically, but the computing complexity is cQnsiderably greater.
Neither of the two alternatives described above is particularly cheap, and there is a requirement for a simple law-cost inertial platform. It is an object of the present invention to provide such a platform.
According to the present invention there is provided an inertial platform which includes a frame arranged to be secured to a vehicle, an outer gimbal supported from the frame about a first gimbal axis, an inner gimbal sup-ported from the outer gimbal about a secand gimbal axis perpendicular to the first gimbal axis, a pickoff and a torque motor on each gimbal axis, gyroscopic means mounted rigidly on the inner gimbal and having three mutually perpendicu-lar sensitive axes, circuit means respQnsive to outputs from the pickoffs and from the gyroscopic apparatus when the platform is in operation to maintain the inner gimbal in an attitude in which first and second sensitive axes of the gyroscopic means are horizontal and the third sensitive axis is vertical, and a numker of accelerometers carried Qn the inner gimbal and having sensitive axes parallel to some or all of the sensitive axes of the gyroscopic means.
.~ ~
~ i67669 T~e invention ~ill now be described with reference to the accompanying drawings, in which:-Figure 1 is a schematic view of a platform, showing an arrangement of the hardware;
Figure 2 is a block circuit diagram of the circuit means and other components of the platform; and Figure 3 illustrates the operation of the ciruit means.
Referring now to Figure 1, a frame fixed rigidly to the vehicle and shown schematically at lO supports an outer gimbal 11 for rotation about an axis 12. The outer gimbal is provided with a pickoff 13 and a torque motor 14 for controlling its attitude relative to the frame 10. The outer gimbal 11 supports an inner gimbal 15 for rotation about an axis 16 which is perpendicular to the axis 12. The inner gimbal i9 provided with a pickoff 17 and a torque motor 18 for controlling its attitude relative to the outer gimbal 11.
The inner gimbal 15 forms a platform on which are mounted gyroscopes, or gyros, having three sensitive axes.
As shown in Figure 1, a first gyro 19 has two mutually perpendicular sensitive axes both of which are parallel to the plane of the inner gimbal 15. A second gyro 20 has its single sensitive axis arranged perpendicular to the two sensitive axes of gyro 19. Each gyro has the usual pickoff and torquer on each sensitive axis.
Also carried on the inner gimbal are the accelerometers required to provide outputs from the platform. Two accelerometers 21 and 22 are shown, having their sensitive axes aligned with those of the two-axis gyro 19.
The various electrical connections to and from the platform are shown schematically in Figure 2 in which a block diagram of the necessary circuit means to which these connections are supplied.
~ 3 ~ `116766~
Pickoff signals from the 2-axis gyro 19 are applied to separate servo amplifiers 30 and 31. The outputs from these amplifiers are applied to the torque motors 14 and 18 on the inner and outer gimbal axes respecively. The outputs from the corresponding gimbal pickoffs 13 and 17 are applied to a central processor 32 which derives pitch and roll outputs. The processor also provides outputs to the torquers on the two axes of the gyro 19.
The second gyro 20 has its pickoff and torquer connected in a conventional capture loop. The pickoff output is connected through 2 capture amplifier 33 to an integrating encoder 34. The output from the encoder is applied both to the processor 32 and to the torquer of the gyro 20.
The two accelerometers are connected in a similar way to gyro 20. The output of accelerometer 21 is applied through a capture amplifier 35 to an integrating encoder 36.
The encoder output is applied to the processor 32 and to the force coil of the accelerometer. Similarly, the pickoff output from accelerometer 22 is applied through a capture amplifier 37 to an integrating encoder 38. The output of the encoder is applied to the processor 32 and to the force coil of the accelerometer 22.
The function of the processor 32 is illustrated schematically in Figure 3, This drawing shows the inputs to and outputs from the processor shown in Figure 2, and indicates the functions to be performed. Many of these are conventional to the inertial platform field and need not be described in detail. The function may be performed by hardware or by software.
Referring to Figure 3, the pickoff output from the gyro 20 of Figure 2 is applied to a capture amplifier 37 and integrator 38, and this integrator produces an output which represents increments of azimuth angle of the platform relative to some datum. This signal is applied via an input A to the processor to a further integrator 40, the output of ~ 4 ~ ~ 167669 which represents the absolute platform azimuth angle, or heading H. A correction signal is applied to the integrator 40 as will be described later.
The two accelerometers 21 and 22 of Figure 2 also have capture loops containing integrators, and the outputs of these integrators are applied to inputs B and C of the processor. Assuming the axes 12 and 16 of Figure 1 to represent the X and Y direction respectively then the output of integrator 36 applied to input B represents increments of X velocity, whilst the output of integrstor 34 applied to input C represents increments of Y velocity. Further integrators 41 and 42 produce outputs representing total velocity in the X and Y directions. These are modified by azimuth resolver 43 which produces output representing North and East velocities. The resolver 43 has an input from the integrator 40, and thus effects a continuous transformation on the X and Y velocities applied to it in dependence upon the heading of the platform.
The North and East velocities from resolver 43 are applied to a conventional Schuler loop circuit 44 which produces output signals representing latitude LA and longitude L0, as well as the North and East velocities ~V and EV. Inputs CR to tbe Schuler loop circuit 44 may provide corrections for gyro drift, instrument bias etc, and an output from the circuit provides the azimuth rate corrections for the integrator 40 already mentioned. These corrections are conventional, and relate to the earth's rate and velocity.
Outputs from the processor are required for the torquer of the accelerometer 19 of Figure 1, and these are obtained at D
and E. These are derived from the Schuler loop circuit 43 by way of a further azimuth resolver 45, performing the reverse function to the resolver 43. Resolver 45 derives from the corrected Schuler loop output the necessary X and Y gyro torquing signals.
- 5 - 116~66~
Signals from the two gimbal pickoffs 13 and 17 are applied to inputs F and G of the processor. These are applied to a third resol~er 46 along with a fixed quantity representing the angle in the horizontal plane between the platform XY axes and the pitch-roll axes from integrator 4.
This resolver converts the X and Y outputs from the pickoffs into pitch and roll angle outputs from the processor.
The three resolvers and the Schuler loop circuit perform fairly simple transformation operations of a type which are well-known in the inertial navigation field. Such transformations are explained in detail in a number of reference books and will not therefore be described further.
As already stated, the functions of the processor may be provided by circuitry or by programming. The desired results may be obtained by different methods to those described. The three sensitive gyro axes may be provided by three separate single-axis gyros, or by two two-axis gyros with one redundant axis. A third accelerometer could be provided if required. The two gimbal pickoffs 13 and 17 are only necesgary if the platform is required to give outputs indicating pitch and roll angle. The processor could be used to resolve the X and Y velocity increments rather than operating on the integrated increments.
Claims (4)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. An inertial platform which includes a frame arranged to be secured to a vehicle, an outer gimbal supported from the frame about a first gimbal axis, an inner gimbal supported from the outer gimbal about a second gimbal axis perpendi-cular to the first gimbal axis, a pickoff and a torque motor on each gimbal axis, gyroscopic means mounted rigidly on the inner gimbal and having three mutually perpendicular sensitive axes, circuit means responsive to outputs from the pick-offs and from the gyroscopic apparatus when the platform is in operation to main-tain the inner gimbal in an attitude in which first and second sensitive axes of the gyroscopic means are horizontal and the third sensitive axis is vertical, and a number of accelerometers carried on the inner gimbal and having sensitive axes parallel to some or all of the sensitive axes of the gyroscopic means.
2. A platform as claimed in Claim 1 in which the gyroscopic means includes a first gyroscope providing the first and second sensitive axes, and a second gyroscope providing the third sensitive axis.
3. A platform as claimed in Claim 1 in which the gyroscopic means includes three single-axis gyroscopes, each providing a separate one of the sensitive axes.
4. A platform as claimed in any one of Claims 1 to 3 in which the circuit means is operable to provide navigational output signals.
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
GB8027726A GB2082801B (en) | 1980-08-27 | 1980-08-27 | Inertial platform |
GB80.27726 | 1980-08-27 |
Publications (1)
Publication Number | Publication Date |
---|---|
CA1167669A true CA1167669A (en) | 1984-05-22 |
Family
ID=10515677
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
CA000384629A Expired CA1167669A (en) | 1980-08-27 | 1981-08-26 | Inertial platforms |
Country Status (6)
Country | Link |
---|---|
JP (1) | JPS5773615A (en) |
CA (1) | CA1167669A (en) |
DE (1) | DE3132799A1 (en) |
FR (1) | FR2489505A1 (en) |
GB (1) | GB2082801B (en) |
IT (1) | IT1148016B (en) |
Families Citing this family (4)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
GB2146776B (en) * | 1983-09-16 | 1986-07-30 | Ferranti Plc | Accelerometer systems |
JP2528299Y2 (en) * | 1990-11-05 | 1997-03-05 | 株式会社スギノマシン | Floor reaction force support structure |
CN102878996B (en) * | 2012-10-07 | 2015-04-29 | 北京航空航天大学 | High-accuracy and heavy-load bearing support system for inertially stabilized platform |
WO2021019683A1 (en) * | 2019-07-30 | 2021-02-04 | 三菱電機株式会社 | Virtual securities collection device, virtual securities collection program, and virtual securities collection method |
Family Cites Families (9)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US3284617A (en) * | 1962-05-15 | 1966-11-08 | Gen Precision Inc | Hybrid strapdown inertial navigation system |
GB1299822A (en) * | 1971-02-01 | 1972-12-13 | Singer Co | Self-calibrating system for navigational instruments |
DE2118662A1 (en) * | 1971-04-17 | 1972-10-26 | Bodenseewerk Geratetechmk GmbH, 7770 Überlingen | Gyro stabilized all-layer platform |
US3746281A (en) * | 1971-08-04 | 1973-07-17 | Us Army | Hybrid strapdown guidance system |
US3931747A (en) * | 1974-02-06 | 1976-01-13 | Sperry Rand Corporation | Gyroscopic stable reference device |
JPS5218592A (en) * | 1975-08-05 | 1977-02-12 | Nippon Kokan Kk <Nkk> | Control rod scram method |
US4136844A (en) * | 1976-03-15 | 1979-01-30 | General Dynamics Corporation | Quasi-inertial attitude reference platform |
JPS54126571A (en) * | 1978-03-24 | 1979-10-01 | Tokyo Keiki Kk | Attitude standard device |
FR2428819A1 (en) * | 1978-06-14 | 1980-01-11 | Sagem | IMPROVEMENTS ON NAVIGATION DEVICES FOR SURFACE VEHICLES |
-
1980
- 1980-08-27 GB GB8027726A patent/GB2082801B/en not_active Expired
-
1981
- 1981-08-19 DE DE19813132799 patent/DE3132799A1/en not_active Ceased
- 1981-08-24 JP JP56131680A patent/JPS5773615A/en active Granted
- 1981-08-26 FR FR8116285A patent/FR2489505A1/en active Granted
- 1981-08-26 CA CA000384629A patent/CA1167669A/en not_active Expired
- 1981-08-26 IT IT49176/81A patent/IT1148016B/en active
Also Published As
Publication number | Publication date |
---|---|
IT1148016B (en) | 1986-11-26 |
FR2489505A1 (en) | 1982-03-05 |
GB2082801A (en) | 1982-03-10 |
FR2489505B1 (en) | 1984-12-07 |
JPS5773615A (en) | 1982-05-08 |
IT8149176A0 (en) | 1981-08-26 |
JPH0131568B2 (en) | 1989-06-27 |
GB2082801B (en) | 1983-12-21 |
DE3132799A1 (en) | 1982-04-29 |
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Legal Events
Date | Code | Title | Description |
---|---|---|---|
MKEX | Expiry |