DE2818202C2 - Navigation device for land, air or sea vehicles - Google Patents

Description

characterized in that

(d) the inertial navigation system is a vehicle-mounted (atrap down) inertial navigation system is,

(e) the non-inertial speed measuring device vehicle-mounted speed sensors (12,14) contains,

(f) to support the inertial velocity signals and then to generate optimized ones No speed signals from that inertial speed signals acted upon Kalman filter (82) is specially designed,

(g) a coordinate transformation computer (94) serving to transform these optimized speed signals into transformed speed signals is provided, and

(h) a for the formation of the position signals reproducing the position of the vehicle from the Position computer (96) provided downstream of transformed speed signals is.

The invention relates to a navigation device for land, air or sea vehicles, containing

(a) an inertial navigation system with accelerometers providing signals generated by the depend on the inertial velocity derived from acceleration signals,

(b) a non-inertial velocity measuring device which provides signals consistent with said Inertial navigation system signals comparable to and in the same way as these are speed dependent,

(c) a Kalman filter,

(ei) to which the differences in the signals of the Inertial navigation system and the speed measuring device switched on are and that

(C2) supplies correction signals for the measured speed

s The task of a navigation device is to indicate the position of the vehicle in a suitable earth-fixed coordinate system.

Inertial navigation devices are known in which a gimbal-mounted and durc, '-; Spinning top Platform stabilized in relation to the vehicle carries accelerometers, which respond to linear accelerations along fixed-platform axes. By integrating the acceleration signals twice, signals are obtained which correspond to the

is the reference point to show the distance covered in the different directions. Since the tops are the Strive to stabilize the platform in inertial space, while usually the platform with one axis held perpendicular to the earth's surface should be, the output signals are fed back to the platform for re-rotation (Richard H. Parvin "Inertial Navigation" D. von Nostrand Comp, inc, 1962). Such inertial navigation devices with gimbaled and stabilized and the earth's surface

■ ^; tracked platform are extremely complex. The speed * and position signals obtained by integrating the acceleration signals are subject to certain characteristic errors. It is also known the accelerometer

ν not to be placed on a stabilized platform, but to be fixed to the vehicle. Changes in the position of the vehicle are detected by turning gyros, which are used to calculate transformation parameters that determine the mutual position of the vehicle-fixed

) 5 Describe the measuring system and the fixed reference system. Be in a coordinate transformation calculator the acceleration signals measured in the vehicle-fixed coordinate system can be transformed into the earth-fixed coordinate system through integration

«Ο then speed and position signals in one earth-fixed coordinate system can be obtained. Such devices are called »Strapdownw inertial navigation devices (V. Wetzig» To determine the Directional reference in strapdown navigation systems

"Men" DFVLR, IFF, 1974).

It is also in the not previously published, older patent application P 27 41 274.4-52 a device for automatically determining the north direction in one Land vehicle has been proposed in which a

w biaxial, electrically tied gyroscope with his The twist axis is arranged essentially vertically and at its perpendicular to each other and to the twist axis Each input axis has a position tap and a torque generator. The signal of each one The position pickup assigned to the input axis is crossed on the torque generator of the respective other input axis switched. The signals fed to the two torque generators are at the same time on a Norda deviation calculator switches which of the ratio of the signals on the Deviation of a device-fixed reference direction of North provides a signal reproducing. In a preferred embodiment of the patent application P 27 41 274.4-52 is a pair of with the gyro unit

(> 5 accelerometers connected whose sensitivity axes are perpendicular to each other and parallel to the two input axes and which are a pair of error signals according to the deviation of the

Deliver gyroscopic axis from the vertical. From the Signals from the north deviation calculator and the accelerometer are used to determine the angle of the Gyro unit and especially the north deviation are calculated. When used in a vehicle, the Accelerometer fixed to the vehicle and the housing of the gyro is 90 ° around one of the Swiveling input axes of the gyro. A computer calculates from the information provided by the accelerometer about the location of the Vehicle to the horizontal and the angular velocities supplied by the gyro around the vehicle-mounted input axes of the gyro the true course.

The device after this previous registration delivers the Course but not the position of the vehicle.

There is also a device for navigation of land vehicles known (DE-OS 25 45 025), which a north-looking meridian gyro to determine the north direction, one after the meridian gyro adjustable free gyro as a course reference device, a speed sensor (tachometer) for generating a signal proportional to the vehicle speed and a computer, which has the course and speed provides the position of the vehicle. Determining the position of the vehicle from the Signals from a speed sensor are also subject to certain errors that are characteristic of this navigation method

From US-PS 37 02 477 a navigation device is known in which speed measurements once from an inertial navigation system and to others may be supplied by a non-inertial velocity measuring device. The differences of the Velocity measurements obtained in the various ways are switched to a Kalman filter This provides estimates of the errors in the speeds measured by the inertial navigation system at which the inertial navigation system operates is corrected.

The speed measuring device is a Doppler satellite system. A stationary satellite sends a signal with a known frequency as well signal indicating its position. The signal with the known frequency shows a Doppler shift in Dependence on the speed of the vehicle relative to the satellites. The speed determined by the inertial navigation system becomes a Signal generated whose frequency corresponds to the expected Doppler frequency These signal frequencies are compared with one another and their difference is applied to the Kalman filter. There are in Form of the Doppler frequencies the speeds of the vehicle in an earth-fixed coordinate system compared to each other.

The known method requires a speed measuring device such as a Doppler satellite system which determines the speed "from outside" in a fixed coordinate system. A theoretical value for the Doppler frequency can be obtained in a relatively complicated manner from the data of the inertial navigation system.

The invention is based on the object of providing a navigation device of the type defined at the outset with a Build up speed measuring device, which measures the speeds of the vehicle in a vehicle-fixed coordinate system.

According to the invention, this object is achieved by that

(d) the inertial navigation system is a vehicle-mounted (strap-down) inertial navigation system,

(e) the approaching inertial velocity measuring device device includes vehicle-mounted speed sensors (12, 14),

(f) to support the inertial speed signals and thus to generate optimized speed signals that of the non-inertial Speed signals acted upon Kalmanfii! Er (82) is specially designed,

(g) a coordinate transformation computer (94) serving to transform these optimized speed signals into transformed speed signals is provided, and

(h) a position computer (96) provided for generating position signals reproducing the position of the vehicle from the transformed speed signals is connected downstream

The inertial navigation system provides the "inertial speed" in vehicle-fixed coordinates. The transformation parameter initially only determines the portion of the accelerometer signals that can be traced back to the acceleration due to gravity, so that it can be compensated. Ό ^; < so related to a vehicle-fixed coordinate system inertial velocities are compared with the other way, z. B. by means of a speedometer or a log, also compared to certain speeds in the vehicle-fixed coordinate system. The optimized speed signal obtained from the Kalman filter is then transformed into the earth-fixed coordinate system by means of the transformation parameters and used to calculate the position.

The structure of the navigation device is very simple and is based on the usual non-inertial Adjusted speed measurements.

Such Kalman or optimal filters and their design are known per se (A. Gelb »Applied Optimal Estimation "MIT Press, London 1974 or U. Krogmann" Das Kaiman-Filter "in" Internationale Elektronische Rundschau "1974 issue 3, pages 45-49 and issue 4, pages 71-76).

Advantageously, transformation parameter correction signals are switched from the Kalman filter to the transformation parameter computer.

Furthermore, it is possible and advantageous that of the Kalman filter speed correction signals for correcting the output signals of the speed sensors can be generated to the aforementioned typical To compensate for error components at least partially.

The inertia measuring unit can, in the manner of patent application P 27 41 274.4-52, with a biaxial Gyroscope and two accelerometers be built up, with a rotational accelerometer with a downstream integrator being provided as a further rotationally sensitive normality sensor, the input axis of which is parallel to the spin axis of the gyroscope pivoted position.

Instead of two uniaxial accelerometers , a biaxial accelerometer can also be used. Instead of a two-axis gyro, two single-axis turning gyros can be provided. Sch! Ii;?! I can also use two single-axis rotational accelerometers with downstream integrators instead of a two-axis gyro.

As speed sensors in the air

A Doppler radar is used, a sonar log for seafaring and a laser or electromechanical log for land vehicles Distance or speed sensors may be provided.

The invention is described below using an exemplary embodiment with reference to the associated Drawings explained in more detail:

F i g. FIG. 1 is a perspective view schematically showing a vehicle and the arrangement of FIG various sensors on this vehicle.

F i g. Fig. 2 shows in perspective the inertia measuring unit when determining the north direction.

Fig.3 shows the arrangement and circuit of the biaxial. Gyro in the inertia measuring unit of FIG.

4 shows the inertia measuring unit in its "navigation" operating position.

F i g. Fig. 5 is a circuit diagram showing signal processing for navigation.

F i g. FIG. 6 shows a block diagram of a Kalman filter as it is used in the arrangement of FIG. 5 is used.

In Fig. 1, 10 denotes a vehicle. Speed sensors 12, 14 are attached to the vehicle 10, for example electromechanical speed sensors, which supply the vehicle speed in the direction of the vehicle longitudinal axis x ^F and the vehicle transverse axis y ^7. An inertia measuring unit 16 is also attached to the vehicle. The inertia measuring unit 16 contains a two-axis gyro 20 in a frame (housing) 18, which is pivotable relative to the frame 18 about an axis 22 parallel to the vehicle transverse axis Gyro 20 is the spin axis parallel to the vehicle longitudinal axis x ^F. The two input axes of the gyro 20 are parallel to the vehicle transverse axis y? and to the vertical axis of ^{the vehicle z F.} Two accelerometers 28 and 30 are also attached to the frame 18 of the inertia measuring unit. The input axis of the accelerometer 28 is parallel to the vehicle longitudinal axis x ^F and the input axis of the accelerometer 30 is parallel to the vehicle transverse axis y ⁷ . The inertia measuring unit 16 also contains a rotational accelerometer 32, the input axis of which is parallel to the vehicle longitudinal axis x ^F and to the spin axis of the gyro 20. The rotational accelerometer 32 thus measures rotational accelerations about the vehicle longitudinal axis x ^F.

The gyro 20 can with its housing between the in F i g. 2 position shown and one against it be pivoted by 90 ° rotated position, which is shown in Fig.4 This pivoting takes place by means of the servo motor 24, which can be controlled via servo electronics 34 controlled by the angle encoder 26 Depending on the position of a switch 36, the servo electronics controls the servomotor to the position shown in FIG. 2 position shown or in the position of FIG. 4th

In the position of FIG. 2, the gyro 20 delivers Signals that allow the north direction to be determined. This is the subject of the Ilteren patent application P 27 41 274.4-52 and in F i g. 3 again shown schematically

The gyro 20 is shown in FIG. 3 positioned with its spin axis H parallel to the vertical axis Xg of the housing or frame 18. The input shaft Yc of the gyro fäiit with the axis together 22 (Fig. 1), while the input axis xc perpendicular to the spin axis of the gyroscope and the input axis Y _a extends. The gyro 20 is rotatably mounted in a cardan frame 38 about the input axis xc. A tap 40 and a torque generator 42 are seated on the input axis xo . The cardan frame 38 is rotatably mounted on the frame 18 about the input axis y _G. A tap 44 and a torque generator 46 are seated on the input axis ya.
The output of the tap 44 is via a

ίο amplifier 48 switched to torque generator 42. The signal from tap 40 is switched to torque generator 46 via an amplifier 50. The degrees of amplification of the amplifiers 48 and 50 are chosen so high that the gyro 20, the cardan frame 38 and the frame 18 are practically electrically connected to the ones shown in FIG. 3 relative positions shown are tied. If the axis ze is arranged exactly vertically, then the ratio of the signals tapped at the outputs 52 and 54 and switched to the torques 42 and 46 is proportional to the tangent of the angle ψ between the input axis yc and the north direction. In the event of a deviation between the vertical axis zg and the vertical, which can be determined by the accelerometers 28 and 30, the output signals of the accelerometers 28 and 30 and the signals from the outputs 52 are processed in a signal processing circuit 56 (FIG. 2) and 54 are supplied, the attitude angles and the true course of the vehicle 10 are determined

In this way, the north direction and the true heading of the vehicle will be determined at the start of the journey Determined in relation to this north direction. The gyro 20 is then rotated 90 "into the positions shown in FIGS. 4 and 5 position shown pivoted. According to the teaching of patent application P 27 41 274.4-52, the gyro works then as a course top.

In the present arrangement, the inertia measuring unit 16 also contains the rotational accelerometer 32, which is followed by an integrator 58 and which in this way supplies the angular velocity around the vehicle longitudinal axis x ^F , while the gyro 20 emits signals which the angular velocities around the axes y ″ and ^, as the vehicle transverse axis and the vehicle vertical axis, reproduce.

The angular velocities tv ^ and w ^ about the vehicle transverse axis ^ respectively, supplied by the gyro 20. the vehicle vertical axis zF and the angular velocity vf supplied by the rotary accelerometer 32 and integrator 58 about the vehicle longitudinal axis x ^F are switched to a transformation parameter computer 60 an input 64 is supplied with the initial values Cf (O) of the direction cosine matrix, which are determined according to the teaching of patent application P 27 41 274.4-52. From this and from the angular velocities ω ^ ΐ, a ^F y, (O ^F _X, the computer unit forms the time derivative C ^{+ n} f of the direction cosine matrix according to the relationship

where (^ is the speed of rotation divisor

or

is. Df.'rei the elements of the rotational speed tensor are calculated from the measured rotational speed signals as follows:

Η ''

1 '·>
LJL

-c ^F

cos Φ +

ok

15th

20th

where w ^F _t , w ^F " H ^ ₇ the speed of rotation signals , Qe the speed of the earth's rotation, Φ the latitude, Vf, Vs the east and north speed of the vehicle, R the radius of the earth and H the height of the vehicle above sea level. The matrix C ~ ^F ν thus obtained, represented by nine elements, is integrated by an integrator 66, ie the integrator integrates each of the nine elements of the matrix C ~ ^f n, whereby the nine elements of the direction cosine matrix C, which is changed by the rotational speeds compared to the initial state \ v will be obtained. As indicated by the connection 68, these elements are connected to the computer unit 62 which, with digital signal processing, now forms C ~ ⁿ f in the next computing cycle with the new direction cosine matrix (^.

In the case of analog signal processing, the computer unit 62 would be a circuit arrangement with multipliers and adders, which form nine linear combinations from nine input signals from the connection 68 and the three angular velocity signals m ^F r, m ^F y, <u ^F i according to the rules of multiplication of matrices. These nine linear combinations are connected to nine analog integrators in integrator 66, the outputs of which are fed back to computer unit 62 via connection 68. Via input 64, the elements of the direction cosine matrix Cf, namely the outputs of the integrators, are reset to specified initial values for the time f-0 "

Instead of using the elements of the direction cosine matrix as transformation parameters, the matrixing can also be done with the four elements of a rotational quaternion or directly with three Euler angles.

The transformation parameters for transforming a vector from a vehicle-fixed coordinate system (F-system) into an earth-fixed coordinate system (MSystem), for example with the coordinates north, east and vertical, are thus constantly available at the output of the transformation parameter computer 60, in the form of the elements Gt of the directional cosine matrix O ⁴ F available.

If the vehicle vertical axis zf and thus the vertical axis 2P of the inertia measuring unit 16 is not exactly vertical, then components of the acceleration due to gravity g act on the two accelerometers 28 and 3G. These components in the output signals of the accelerometers 28, 30 are compensated for by the output signals of correction signal generators 70 and 72, respectively. _{The direction cosines Cn and C 32 are} fed to these correction signal generators 70 and 72 from the output of the transformation parameter computer 60, the correction signal generators 70 and 72 supplying output signals gCu and gCn, respectively. These output signals are superimposed on the signals from the accelerometers 28, 30 in summing points 74 and 76, respectively, as a result of which pure translational accelerations of the vehicle are reproduced in the coordinate system fixed to the vehicle.

The translational acceleration signals obtained in this way are applied to integrators 78 and 80, respectively, which supply inertial velocity signals v? / Or yfiy. Further speed signals v ^ ßrund v ^ oy are supplied by the speed sensors 12 and 14. These speed signals v ^ / ,, ν * Ό * or v ^ v * Dy are fed to a Kalman filter 82.

The Kalman filter 82 determines from the speed signals v ^ / " V ¹ Ox, ^ iy and v ^ p, optimized speed signals V ^ _x and v ^ for the components of the speed in a coordinate system fixed to the vehicle. Furthermore, the Kalman filter 82 yeasts correction signals Ckoo- for the transformation parameters Cf and correction signals Ckoh- for the transformation parameters Cf and correction signals ^, Km and cfyKorr for the speeds measured by the speed sensors (12, 14). The signals CW are sent via a connection 84 to a correction computer 88, which forms part of the transformation parameter computer 60. The correction signals VxKorr and VyKorr are fed to correction circuits 88 and 90, respectively, which correct the speed signals supplied by the speed sensors 12, 14. In this way, for example, the slippage of chains or wheels in land vehicles with electromechanical speed sensors can be taken into account.

In the case of land vehicles, one can assume that the lateral speed is ν ^ ρ, -Ο. The speed sensor 14 can then be omitted, so that the value v ^ py-O is fed to the Kalman filter 82.

With the speed components νΊ, ν * ⁷ supplied by the Kalman filter 82, as well as the vertical speed ν ' ⁷ supplied from a vertical channel 92 ! be in a coordinate transformation Rechner94, which also includes the corrected transformation parameters CT ¹ F by the transformation parameter calculator 60 are supplied, the velocity components vn Vss vp in a space- or earth-based coordinate system according to the relation

These speed components v _s vm Vo are connected to a position computer 96, which uses the usual methods of dead reckoning to calculate the position of the vehicle to north (N) east (E) and altitude f / #. East position, latitude Φ can be calculated as specified in P 25 45 0253. Φ is required for the calculation of the rotational speed tensor

Although this is not necessary for the navigation method according to the invention, the curve φ as well as pitch and roll angles ν or φ can also be determined and displayed from the elements of the direction cosine matrix by a position angle calculator 98, as is the case, for example, in patent application P27274.4-52

is revealed.

For ships and land vehicles, V ^ = O can be set will.

The structure of the Kalman filter 82 is shown in FIG.

The speed signals ν * / _χ and \ * ox are switched against each other at a summing point 100. Likewise, the speed signals v ^ and ^ oy 'are switched against one another at a summing point 102. Feedback signals are superimposed on the difference signals in summing points 104 and 106, respectively. The signals thus obtained at the summing points are fed to a linearized dynamic model 108 of the system, which forms the core of the Kalman filter 82, with time-dependent factors Kx (t) and Ky (t) .

The model 108 thus receives a two-dimensional state vector as an input variable. It delivers as an

ίο

transition a state vector χ with the components

ί = Wx, / y, CfCn, / xATorr, / j * ""]

The block F (t) contains the coefficients of the linearized dynamic model as a time-dependent matrix, the order of which corresponds to the number of elements in the state vector χ. The block labeled Jd t forms the state vector x through integration and linear combination of the components from the time-dependent weighted input signals. This state vector χ forms the output variables of the Kalman filter 82 and is also converted via block 110, which symbolizes a matrix with two rows and a number of columns according to the order of χ , into a two-dimensional vector which represents the two feedback signals.

In addition 6 sheets of drawings

Claims (1)

Claim: Containing navigation device for land, air or sea vehicles (a) an inertial navigation system with accelerometers providing signals transmitted by depend on the inertial speed derived from acceleration signals, (b) a non-inertial velocity measuring device which provides signals related to the said inertial navigation system signals are comparable and in the same way how these are speed dependent, (c) a Kalman filter, (ei) to which the differences in the signals of the Inertial navigation system and the speed measuring device are switched on and that (C ₂ ) J supplies correction signals for the measured speed,