DE4342596A1 - Electronic magnetic compass for compensation of course indication errors caused by ship's inclination - Google Patents

Abstract

The compensating vertical ship's field strength is varied by systematic testing so that the sum of the squares of the measurement values of three mutually perpendicular magnetic field probes is independent of the ship's inclination. The magnetic field probes are rigidly attached wrt each other to form a triple probe which is suspended as a unit from a gimbal suspension. The vertical ship's field strength so determined is used as the compensating field strength for the course indication error.

Description

The invention relates to a device for electronic Magnetic compasses used to compensate for heading errors serves the inclination of the ship about its longitudinal and transverse axis (heel or trim) arise.

Electronic magnetic compasses are known. Electronic senso Ren provide information about the components of the magnetic Earth field in relation to certain fixed directions. Out This information can be obtained through suitable electronic Further processing the information you are looking for the ship's course, d. H. the angle that the ship's alignment forms with the horizontal component of the earth field vector. These Course information is displayed on a display device or in other plants, e.g. B. self-steering systems, entered.

A commonly used arrangement uses sensors det, the longitudinal ship component, designated 1 in future, and the transept component, in the future designated q, mes sen. H is the horizontal component of the earth's magnetic field and z the adjacent ship course, then is:

1 = H _* cos z and g = -H _* sin z Eq. (1)

After dividing q by 1, the tangent of z and from it the ship course z.

In the case of electronic magnetic compasses, as with conventional magnetic compasses, there are false indications when the ship is tilted about its longitudinal axis (heel) and about its transverse axis (trim) as a result of the high ship component R of the magnetic ship field. These are eliminated within the scope of the usual com paßregulierung that at the location of the Magnetkompas ses the opposite direction of the highship field R is generated the same compensating highship field R _k , so that the prevailing at the compass location total (with the ship inclining) highship component R ' (R ′ = R + R _k ) is zero. (Compensation of the heeling error, also called K compensation).

R _k is usually generated with conventional magnetic compasses with one or more compensating magnets, with electronic magnet compasses often with the aid of a coil through which direct current flows, the coil axis of which points in the direction of the nave (so-called K coil).

To recognize the compensated state, i.e. H. to see if the total high field strength R 'is zero, at conventional magnetic compasses used the so-called K-scale. she is located in a magnetically undisturbed location near the com pensierplatzes - at which the ship field is not effective - so adjusted that it is in equilibrium if only that undisturbed vertical component Z of the magnetic earth field is effective. Then to compensate on board the ship the K scale to the location of the compass rose magnet system brought and the compensation device adjusted (by Position, number and strength of the K-magnets) that the K-scale in Balance is. (The compass has to be removed from its holder be removed!). This way the entire high Ship field strength R 'made zero.

In the case of electronic magnetic compasses, the K compensation cannot be carried out in the manner described because the sensors are mechanically integrated into the course scanning element in such a way that they cannot be removed from it in the simple manner necessary for compensation. In addition, due to its size, a K-scale cannot be brought to the location of the sensors. Usually, therefore, in addition to the two sensors in the longitudinal and transversal direction, a third sensor is attached to this perpendicular sensor, which measures the tall ship component of the superposition of the earth field vector with the magnetic field originating from the ship. In future we will call this measured value h. The K compensation is carried out by using the associated compensating device for K to select the compensating highship field R _k (e.g. by adjusting the current flowing in the K compensating coil) that the measured value when the ship is not inclined h becomes the vertical component Z of the undisturbed earth field prevailing at the compensation location (ie in particular: without being superimposed by the magnetic field generated by the ship). This method has the disadvantage that it must be assumed that

• - that Z is sufficiently well known, and
• - That the display of the high ship sensor is not only right is relative but also absolutely sufficiently precise, because this procedure is - in contrast to that with the conventional K-scale - not a "zero method".

This means that the K compensation does not go through everywhere can be led, because the usual nautical charts do not contain Specification of the vertical component Z; Information material about this size is generally not available on board. Because of The highships meet the demand for absolute accuracy sensor more complex and therefore more expensive or it will - if this The requirement is not met - the compensation is imprecise.

In the method according to the invention, those are described Disadvantages avoided in that the natural movements of the Vessel can be used to compensate for K in the sea. To is first by electronic processing of the measurement values l, q and h from these the sum of squares S = l² + q² + h² educated. S is then and only then from the heel angle i (Tilt angle of the ship's vertical axis around the ship's longitudinal axis against the vertical direction) independently when the tall ships field strength R ′ is zero.

The following relationships result from Fig. 1:

l = H _* cos z

q = -H _* sin z - R ′ _* sin i Eq. (2)

h = Z + R ′ _* cos i

By squaring and adding the squares one obtains some transformations:

S = 1² + q² + h² = Eq. (3)

= (Z² + R′² + H² + 2 _* Z _* R ′ _* cosi) + 2 _* H _* R ′ _* sini _* sinz.

From Eq. (3) it can be seen that S is independent of the heel angle i when R 'is zero. According to the invention, this relationship is used to determine the value of R _k by systematically changing the compensating field R _k , in which S is independent of the heeling angle i. You can do that e.g. B. he know that the correlation coefficient r _{s, i} between the measured variables S and i is zero. The "correct" value of the compensating highship field strength R _k is set when this correlation coefficient is zero.

You can also see from Eq. (3) that the sum of squares S is so depends more on i, the greater the amount of sin z; that means that this K compensation on a ship course if possible should be carried out close to the east or west course. The compensation method on these courses is most accurate because here already small changes of R ′ noticeable changes of the Cause correlation coefficients.

When carrying out the K compensation according to the invention, the quantities l, q, h and i are measured and stored electronically at regular time intervals d while the ship is rolling. The time intervals d who chosen the so that several measurements (z. B. 10) are carried out during a rolling period. The measurements are carried out over several rolling periods, so that in each case n (e.g. n = 30 to 40) measured values are produced. The sum of squares S _{m is} formed from the measured values l _m , q _m and h _m (m = 1... N) and stored together with the values measured simultaneously for the heel angle. After completing the n measurements, the mean values

S _mean = (S₁ +... + S _m +... + S _n ) / n and i _mean = (i₁ +... + I _m +... + I _n ) / n Eq. (4)

calculated.

Then according to Eq. (5) the correlation coefficient r _{s, i} calculates:

To carry out the K compensation, the measurement and calculation of r _{s, i} at the existing value of the compensating field strength R _k , R _k (1) is carried out first. If the determined value of r _{s, i} , r _{s, i} (1) results in the value zero or a sufficiently small amount, the compensation process is completed and the previously used value of R _k is used further. If there is an r _{s, i} greater than zero, then R ′ is greater than zero and a smaller rer value is used as the second approximation for R _k , R _k (2) (this applies to eastern courses; to western courses is to be reversed). The described process is repeated with this value. If the value of r _{s, i} , r _{s, i} (2), which is now more determined, is zero, the compensation process is completed and R _k (2) is used as the new value for the compensating field strength. If R _k (2) is also not equal to zero, a third approximation for R _k , R _k (3), according to the following Eq. (6) calculated:

R _k (3) = [R _k (2) _* r _{s, i} (1) -R _k (1) _* r _{s, i} (2)) / [r _{s, i} (1) -r _{s, i} ( 2)]. (6)

The process described continues until the correlation coefficient becomes zero. The associated value of R _k is the determined value for the compensating highship field strength.

Any heeling knife can be used to measure i which is an electrical signal as a measure of the heel angle i delivers. In particular, the system for K compensation can the electronic magnetic compass itself for measuring i are used: A short-term current pulse of known Greatness is created by the compensating high given coil used. That from this stream generated highship field generated short in the transept sensor an additional magnetic field. This has a short-term effect a change in the measured value q. This change is a Measure for i.  

Instead of the rolling movements, the ramming movements can also be used of the ship for K compensation - analogous to the one here written procedures - are used. Instead of the crane angle i is to be used instead of the ramming angle j of the transept sensor with the measured value q the longitudinal ship sensor with the measured value l. Instead of the eastern or western comm In this case, retirement courses are northern or southern Choose courses to compensate.

Likewise, inclinations can be relative to any other axis used for the ship, e.g. B. with "intercardinal" probes arrangements. The above Formulas are then too modifiable adorn: Linear combinations of i and j correspond to Linearkom binations of q and l.

Correspondingly, the sum of squares S with the sum of squares i² + j² or the sum of squares sin² i + sin² j correlates the.

When rolling and pounding the ship in rough seas, accelerations in the horizontal direction occur in addition to the ship's inclinations (heeling and trim). These cause the gimbaled sensors for l and q to be inclined. In this case, the heeling angle i (or the trim j) is not exactly measured by the method described above, but the angle between the ship's vertical axis and the direction of the sensor for q (or l), i '(or j'). Since the angles i and i '(or j and j') are strongly correlated (see also laid-open document DE 41 24 002 A1, H.-R. Uhlig: Compensating device for compensating the dynamic errors of electronic magnets) the described method of determining R _k can be applied using the correlation coefficients.

During the described measurements of the quantities l, q, h and i (or j) with changed values of R _k , the course display and the acquisition of the course information (for input, for example, in self-steering systems) continue to run undisturbed. During the pulse duration, the course transmission is switched off and the course value before the start of the pulse is entered into the course transmission system during the pulse duration and after the pulse is switched off, the course transmission is continued as before the same was switched on (see the above-mentioned publication).

The determined improved compensation field strength R _k can be used in a known manner to compensate for the heeling error by feeding an electrical current into the K coil, which generates a magnetic high field of the size R _k at the location of the sensors for q and 1. However, it is also possible - according to the invention - to store the value R _k electronically, measure the values sin i and sin j in the manner described above by entering short current surges, multiply the values obtained by the stored value R _k and add the product to the measured value of Add q or l electronically and use the values thus obtained in a known manner to obtain information about the adjacent ship course z. This method has the advantage that significantly less electrical energy is required since no constant current has to flow through the K coil. This energy saving proves to be a significant advantage, especially when the electronic magnetic compass is operated by battery: the compass can be operated with the same battery for a much longer time, and if the ship's power supply fails, significantly longer times can be bridged before the battery needs to be replaced.

An approximation - first for Z and from it for the ge searched value R ′ - can calculate the device by the ship is on a north or south course (according to the course display of the electronic magnetic compass). The control of this Courses can be done by hand or using a self steering system done by the electronic magnetic compass as a course information provider is controlled. In these cases, through reached the control process that the measured value q is zero. (Because of possible simultaneous superimposed tamping and yawing gears is not necessarily the exact one Course 0 ° or 180 °.)

From the equations (2) one obtains after a few transformations:

(hZ) ² + q² + l² - R′² + H² + 2 _* H _* R ′ _* sin z _* sin i Eq. (7)

If one assumes that sin z and sin i are small against one then the last summand of Eq. (7) vernach casual and it follows that the left side is independent of i is. Furthermore, q = 0 if there are two different heel angles the associated values of h (h₁ and h₂), and measured by l (l₁ and l₂). This results in following relationships:

(h₁-Z) ² + l₁² = R′² + H²

(h₂-Z) ² + l₂² = R′² + H².

If you subtract the second from the first equation, you get after some transformations Z:

The device according to the invention calculates with the measured value h using the last of the equations (2) and the heeling angle i the searched approximation R '.

Similarly, you can steer the ship on the east or west course and use the pounding movements to determine Z. The Equation for the determination of Z can be obtained from Eq. (8) by each replaced size l with size q. As before described one obtains R '.

Claims (16)

1. Device for electronic magnetic compasses to compensate for the course display errors caused by ship inclination, characterized in that the compensating high field strength R _{k is changed} by systematic testing so that the sum of the measured values of three mutually perpendicular magnetic field measuring probes, which are firmly connected to form a triple probe are gimbal-mounted as a whole, is independent of the ship's inclination, and that the high ship field strength R _k determined in this way is used as a compensating field strength for the course display error caused by the ship's inclination. 2. Device according to claim 1, characterized in that the natural movements of the ship at sea with the related changes in ship inclination to Er averaging the compensating highship field strength be used. 3. Device according to claim 1 and 2, characterized in that that the three probe directions in the longitudinal, transverse and show the direction of the nave (measured values l and q obtained or h). 4. The device according to claim 1, characterized in that the systematic search is carried out by the correlation coefficient r _{s, i} between the sum of squares S and the heeling angle i for different values of the compensating high ship field strength from the measured values of the three probes and the associated heeling angles i be calculated and that value of R _{k is used} for further compensation for which this correlation coefficient becomes zero. 5. Apparatus according to claim 1 and 4, characterized in that Eq. (6) is used.   6. The device according to claim 1, 4 and 5, characterized net that instead of the heel angle i the trim j ver is applied. 7. The device according to claim 1, 4 and 5, characterized net that i instead of the heel angle any Linear combination of i and j is used. 8. The device according to claim 1, 4 and 5, characterized net that instead of the heel angle the sum of squares i² + j² is used. 9. The device according to claim 1, 4 and 5, characterized net that instead of the heel angle the sum of squares sin² i + sin² j is used. 10. The device according to claim 1 to 9, characterized in that that the angle i and / or j using an outside of the Device attached device measured according to the invention be that an electrical signal as a measure of i or j enters into the device. 11. The device according to claim 1 to 9, characterized in that the angles i and / or j measured using the Kompensiervor direction of the electronic magnetic compass who the by

• - A short-term pulse of known height is generated in the K coil and
• - The change in the measured value caused by this pulse t and / or l - this change is proportional to the sine of the angle i or j - measured and used for further calculation and evaluation.

12. The apparatus according to claim 1 to 11, characterized net that during the measurements the transfer of the course information is switched off and before the measurement current course value during the measuring process in the course transmission system is entered, and after completion of the The course transfer as before the measuring process  is continued. 13. The apparatus according to claim 1 to 12, characterized in that the determined value of R _{k is} electronically stored, the values sin i and / or sin j measured according to the method described in claim 10, the products R _{k *} sin i and / or R _{k *} sin j are calculated electronically and then added to the measured values q or l. The values obtained in this way are then used to determine the ship's course z. 14 Device according to claim 1 to 12, characterized in that the determined value of R _{k is} stored electronically, the values sin i and / or sin j measured according to the method described in claim 11, the products R _{k *} sin i and / or R _{k *} sin j are calculated electronically and then added to the measured values q or l. The values obtained in this way are then used to determine the ship's course z. 15. The apparatus according to claim 1 and 2, characterized in that an approximate value for R 'is determined in that the ship is steered to the north or south course and the Heelings of the ship can be exploited to, according to Eq. (8th) the vertical component Z of the magnetic earth field and from it with Eq. (2) to get an approximate value for R ′. 16. The apparatus according to claim 1 and 2, characterized in that an approximation for R 'is determined by the fact that Ship is steered on the east or west course and the Pounding movements of the ship can be exploited in accordance with Eq. (8) - there the measured value 1 by the measured value q replaced - the vertical field strength Z and from it with Eq. (2) to get an approximation for R '.