WO2005050126A1

WO2005050126A1 - Orientation signalling and determination method and device

Info

Publication number: WO2005050126A1
Application number: PCT/EP2004/052517
Authority: WO
Inventors: Johan Martin Carol Zwarts; Herman Benthem De Grave
Original assignee: Thales Nederland B.V.
Priority date: 2003-10-28
Filing date: 2004-10-13
Publication date: 2005-06-02
Also published as: ES2626004T3; EP1680643B1; EP1680643A1; NL1024644C2

Abstract

This invention relates to orientation signalling and determination methods and devices adapted for beam guidance. In particular, these orientation methods could be applied in course correction system. It proposes an offset based orientation determination method to resolve the orientation ambiguity associated with the use of linearly polarised waves for its determination independently from the circumstances of use. The orientation signalling method, adapted for beam guided objects using a guidance beam for indicating a route to be followed to a target, is characterised in that the relative position of the guidance beam with respect to the guided object is offset in a predetermined direction during a predetermined duration. In a first realisation mode the offset is implemented by moving the guided object from the indicated route in the predetermined direction during the predetermined duration. In a second realisation mode, the offset is implemented by moving the guidance beam in the predetermined direction during the predetermined duration.

Description

Orientation signalling and determination method and device

This invention relates to orientation signalling and determination methods and devices adapted for beam riding guidance. In particular, these orientation methods could be applied in course correction system.

In beam riding guidance, a guided object has to follow a guidance beam aimed in the desired direction. In flight, the guided object measures its own position with respect to the guidance beam and translates these measurements into appropriate control signals for its own control means. For this purpose, the orientation (roll angle) of the guided object has to be known. Beam riding guided objects can determine their orientation by measurement of the polarisation of the beam also used as, for example, the course correction system of the EP 0354608. Thus, this technique gives a measure with an orientation ambiguity (also called "up-down" ambiguity). It is easily understandable that with such ambiguity, a guided object instead of flying up could be directed to crash over the ground or the sea surface, causing the destruction of the guided object.

In the state of the art, some solutions have been proposed to solve this "up-down" ambiguity.

One of these solutions is based on the use of sunlight. The guided object is equipped with light sensors. These light sensors are connected to "up-down" determination means. The "up-down" determination means is provided with a memory comprising the distribution of the light sensors over the guided object. So, the "up-down" determination means could compare the light intensity measured by each of the light sensors, and amalgamate the light sensors in two different groups : the light exposed group, which comprises the light sensors which measure the highest light intensities, and the light non exposed group, which comprises the light sensors which measure the lowest light intensities. Thus, the "up-down" determination means, knowing the distribution of the light sensors over the guided object, gives the "up-down" direction as the direction from the light exposed group to the light non exposed group. Unfortunately, such light based "up-down" determination method does not work under all circumstances. It needs a sufficient difference in light intensity between the measurements of the light sensors. So, the "up-down" ambiguity resolution with such determination method is null at night. In addition, even during daylight hours, a dark weather could cause a low or even null "up-down" ambiguity resolution. Another proposed solution known in the state of the art is based on the measurement of the earth magnetic field using a magnetic sensor. For example, the EP 0503214 patent relates to an orientation device including a magnetic sensor. The orientation device is suitable for providing an observer with his indicative positioning error with respect to a preset direction. In this purpose, an external unit provides a preset direction to a computer that compares it with an alignment data and calculates an alignment error data. The alignment data, measured with respect to the magnetic north, is provided in the form of an electric signal by the magnetic sensor. However, such earth magnetic field based "up-down" determination method does not work under all circumstances. When the guided object moves in parallel with the magnetic field lines, the "up-down" ambiguity resolution obtained using a magnetic sensor is null. Moreover, both the light based "up-down" determination method and the magnetic field based "up-down" determination method are expensive to implement.

This invention solves the above-mentioned drawbacks by proposing an offset based orientation determination method to raise the orientation ambiguity independently from the circumstances of use.

An object of this invention is an orientation signalling method, adapted for beam riding guidance using a guidance beam for indicating the guided object a route to be followed to a target, characterised in that the relative position of the guidance beam with respect to the guided object is offset in a predetermined direction during a predetermined duration.

In a first realisation mode the offset is implemented by moving the guided object from the indicated route in the predetermined direction during the predetermined duration.

In a second realisation mode the offset is implemented by moving the guidance beam in the predetermined direction during the predetermined duration.

An advantageous embodiment of this invention is the orientation signalling method described wherein the predetermined direction is parallel to sea or ground surface.

So, the orientation signalling method could be also implemented without the risk that the guided object crashes in the case the target is, for example, a low height flying object or an over sub marine ground skimming object.

Moreover, as usually in order to reduce the influence of multipath, the guidance beam is wider in the horizontal direction than in the vertical direction, this embodiment has a smaller risk that the guided object during execution of the invention goes outside the guidance beam.

A further object of this invention is an orientation signalling device in which the above orientation signalling method is implemented. Said orientation signalling device comprises offset means for modifying the relative position of the guidance beam with respect to the guided object in a predetermined direction during a predetermined duration.

In the first mode of realisation, in which the guided object is moved from the indicated route in the predetermined direction during the predetermined duration, the offset means: - receives a direction information data comprised in a guided object control signal and corresponding to the indicated route; - offsets said direction at a predetermined time, during the predetermined duration; and - transmits said offset guided object control signal to a guided object control means.

In the second mode of realisation, in which the guidance beam is moved in the predetermined direction during the predetermined duration, the offset means: - receives a direction information data comprised in a guidance beam control such as the guidance beam indicating the route to be followed; - offsets said direction at a predetermined time, during the predetermined duration; and - transmits said offset guidance beam control to a guidance beam control means.

Moreover, this invention relates to an orientation determination method adapted for beam riding guidance using a guidance beam for indicating a route to be followed to a guided object characterised in that the orientation is determined as a function of an offset in the relative position of the guidance beam with respect to the guided object in a predetermined direction during a predetermined duration. In addition, another object of this invention is an orientation determination device in which the above orientation determination method is implemented. Said orientation determination device comprises:

- Offset direction reading means receiving a detected beam direction corresponding to the route indicated by the guidance beam and detecting an offset in said detected beam direction associated with the offset in the relative position of the guidance beam with respect to the guided object; and

- Orientation evaluation means connected to said offset direction reading means, implementing a function of the direction of the detected offset and the predetermined direction. The above objects of this invention could be combined in an orientation system comprising the above orientation signalling device and the above orientation determination device which detects the offset implemented by the orientation signalling device.

Another object of this invention is a beam riding guidance system comprising:

- A beam projector transmitting linearly polarised waves; - Guidance beam control means connected to said beam projector, orientating the beam projector in a guidance beam direction given by the guidance beam control signal;

- At least one beam receiver placed in the rear of said guided object capable of receiving the projected beam; - Alignment determination means connected to the at least one beam receiver, deducting from the projected beam received a detected beam direction and providing said detected beam direction to guided object control means;

- The above orientation system, ■ whose orientation signalling device offsets the relative position of the guidance beam with respect to the guided object in a predetermined direction during a predetermined duration; and ^■ whose orientation determination device detects the offset of the relative position of the guidance beam with respect to the guided object implemented by the orientation signalling device and deduces the orientation from this said detected offset and the predetermined direction.

Further features and advantages of the invention will be apparent from the following description of examples of embodiments of the invention with reference to the drawing, which shows details essential to the invention, and from the claims. The individual details may be realised in an embodiment of the invention either severally or jointly in any combination. - Figure 1, a principle scheme of the beam riding guidance system implementing the invention, - Figure 2, a time diagram showing the principle of the first embodiment of the orientation signalling according to the invention, - Figure 3, a time diagram showing the principle of the second embodiment of the orientation signalling according to the invention, - Figures 4a and 4b, an example of flow charts of the orientation method, respectively, the orientation signalling method and the orientation determination method, according to the invention, - Figures 5a and 5b, an example of the orientation system, respectively, the orientation signalling device and the orientation determination device, according to the invention, - Figure 6, an example of the beam riding guidance system in which the first embodiment of the orientation system according to the invention is implemented, - Figure 7, an example of the beam riding guidance system in which the second embodiment of the orientation system according to the invention is implemented. Figure 1 shows a principle scheme of the beam riding guidance system. A beam emitter P sends a guidance beam B in the direction of the target T to guide the guided object G to this target T. So, the guided object G enters the guidance beam B and follows the route the guidance beam B indicates.

The purpose of the orientation signalling method is to offset O the relative position of the guidance beam B with respect to the guided object G in a predetermined direction during a predetermined direction. Hereinafter will be described two embodiments of the orientation signalling. Whereas in the first embodiment, it is the guided object G that is moved from the indicated route to get said offset, in the second embodiment, it is the guidance beam B that is moved to get said offset. The predetermined direction could be parallel to sea or ground surface. In this manner, the orientation signalling method could be also implemented without crashing risks in beam riding guidance system whose target T is, for example, a low height flying object or an over sub marine ground skimming object.

Moreover, as usually the beam is wider in the horizontal direction than in the vertical direction, so the second embodiment has a smaller risk that the guided object G during execution of the invention goes outside the guidance beam B.

The following examples show a sole offset but, if necessary, the relative position could be offset more than one time. Figure 2 shows a time diagram illustrating the route of the guided object G. The guided object G moves mostly in a direction d_g(t) given by the guidance beam B. In order to indicate the orientation, the guided object G will be moved from this route during a predetermined duration T in a predetermined direction O. The example shows an offset O at a predetermined time t₀.

Figure 3 shows a time diagram illustrating the route indicated by the guidance beam B. The guidance beam B moves mostly in a direction d_b(t). In order to indicate the orientation, the guidance beam B will be moved during a predetermined duration T in a predetermined direction O. The example shows an offset O at a predetermined time to.

In this second embodiment, the predetermined duration T could be short enough not to be taken into account by the guided object G such as the offset is a small offset.

Figure 4a shows a flow chart of an example of the orientation signalling method. In the first embodiment, the control signal c(t) provides the guided object control means 80 with the direction d_g(t) to followed. Whereas, in the second embodiment the control signal c(t) provides the guidance beam emitter P control means with the direction d_b(t) in which the guidance beam B has to be emitted. So, the control signal c(t), whatever the embodiment is, provides a direction d^t), as called original direction hereinafter.

One way to achieve the orientation signalling is in a first step S1 to receive said control signal c(t) = [dι(t) ...] and to extract said direction dι(t). At a predetermined time t₀, during a predetermined duration T, said direction dι(t) is offset in a second step S2. In the third step S3, the direction d(t) is reintroduced in said control signal c(t) such as c(t) now comprises the offset direction d₂(t) during said duration T from said predetermined time tn. The predetermined time t₀ could be such that the offset is introduced shortly after the guided object has been fired in this direction dι(t).

So, the orientation signalling device 20,70 provides a modified control signal c(t) = [d(t) ...] wherein the direction d(t) corresponds to the original direction dι(t) except in the following time interval [t₀, t₀+T] and to the offset direction d₂(t) except in this time interval [t₀, t₀+T].

In addition, offset direction d₂(t) could be calculated in step S2 by adding to the original direction d1(t) given by the first step S1, an offset o(t). Said offset o(t) gives the predetermined direction in which said original direction dι(t) is to be offset.

The guided object orientation ORT is determined as function of an offset direction ό(t) read from the detected direction d(t) and the predetermined direction of the offset o(t) applied to the direction d-ι(t).

Figure 4b shows a flow chart of an example of the orientation determination method. The orientation signalling method treats a detected direction d(t). In a first step D1, a detected offset direction 6(t) is read from said detected direction d(t) . For example, this offset could be determined at the predetermined time to and/or during the predetermined duration T. In a second step D2, said detected offset direction ό(t) is compared to the predetermined offset direction o(t) providing a guided object orientation ORT.

An example of orientation signalling device 20, 70 not illustrated comprises an offset means which receives the control signal c(t) comprising the original direction dι(t) and modifying directly the original direction d-ι(t) into d₂(t) corresponding to the offset direction dι(t)+o(t) at the predetermined time to during the predetermined duration T within the control signal c(t).

Figure 5a shows another example of the orientation signalling device

20,70 in which the orientation signalling method is implemented. The orientation signalling device of the first embodiment 20 and the orientation signalling device of the second embodiment 70 have the same principle as shown by Figure 5a.

The control signal c(t) is received by the receiving means 21,71 which extract the original direction d-ι(t) from the control signal c(t). Substitution means 23,73 are connected to said receiving means 21 ,71 for receiving the control signal c(t). Said substitution means 23, 73 replace in said control signal c(t) = [d-ι(t)...] said original direction d-ι(t) by a direction d(t). So, the orientation signalling device 20,70 provides a modified control signal c(t) = [d(t) ...] where d(t) = dι(t), the original direction for t ≠ [t₀, t₀+T] and d₂(t), the offset direction for t = [t₀, t₀+Tj.

Offset means 22, 72 could be connected to the receiving means 21, 71 and the substitution means 23, 73, for providing said direction d(t) to the substitution means 23, 73. Calculation means 23 add an offset o(t) in a predetermined direction to said original direction d-ι(t) provided by the receiving means 21 at a predetermined time t₀, during a predetermined duration T to obtain the offset direction d₂(t). Figure 5b shows an example of the orientation determination device 90 in which the orientation determination method is implemented. An offset direction ό(t) is read by the reading means 91 from the detected beam direction d (t) . Orientation evaluation means 92 are connected to said offset direction reading means 91. A function of the detected offset direction δ(t) and the predetermined direction of the offset o(t) applied to the primary beam direction d-ι(t) is implemented in the orientation evaluation means 92.

The orientation evaluation means 92 comprise comparison means connected to the offset direction reading means 91, providing the guided object orientation ORT by comparing said detected offset direction ό(t) to said predetermined offset direction o(t).

So, figures 5a and 5b show an orientation system comprising the orientation signalling device 20 or 70 and the orientation determination device 90.

Figures 6 and 7 show beam riding guidance systems with respectively the orientation system according to the first and second embodiment of the invention.

In the first embodiment of the invention, the guided object G is moved from the indicated route, so the orientation signalling device 70 is implemented within the guided object G as shown by Figure 6.

The transmitting part of the guidance beam emitter P comprises a beam projector 30. The beam projector 30 transmits linearly polarised waves. The direction of the beam projected by the beam projector 30 is controlled by a guidance beam B control means 10 connected to said beam projector 30.

The projected beam is received by at least one beam receiver 50 in the guided object G. The at least one beam receiver 50 could be placed in the rear of said guided object G. The guided object G could comprise 2 orthogonal beam receivers 5050. Alignment determination means 60 are connected to the at least one beam receiver 50. The alignment determination means 60 deduce from said projected beam received a detected direction d(t) . Said detected direction d(t) is provided to the guided object control means 80 through the orientation signalling device 70. By this way, the orientation signalling device 70 transmits the detected direction d(t) , as the original direction dι(t) mentioned in the above Figures 4a, for t ≠ [t₀, t₀+T] and d₂(t), the offset direction for t = [t₀, t₀+T] corresponding to the offset detected direction d(t)+o{t). By this way, the relative position of the guided object G with respect to the guidance beam B is offset during a predetermined duration T.

An orientation determination device 90 is connected to the alignment determination means 60. The orientation determination device 90 implements the guided object orientation determination as a function of the direction of the detected offset read δ(t) from said detected direction d(t) and the predetermined direction of the offset o(t) applied to the original direction dι(t).

In the second embodiment of the invention, the guidance beam B is moved, so the orientation signalling device 20 is implemented within the guidance beam emitter P as shown by Figure 7.

The transmitting part of the guidance beam emitter P comprises a beam projector 30. The beam projector 30 transmits linearly polarised waves. The direction of the beam projected by the beam projector 30 is controlled by a control signal c(t), which gives an original direction dι(t). The control signal c(t) is provided by a guidance beam B control means 10 connected to said beam projector 30.

The transmitting part comprises also an orientation signalling device 20 which implements the offset o(t) of said primary beam direction dι(t) in a predetermined direction during a predetermined duration T.

The projected beam is received by at least one beam receiver 50, in the receiving part of the beam riding guidance system. The at least one beam receiver 50 could be placed in the rear of said guided object G. The guided object G could comprise 2 orthogonal beam receivers 50 50.

Alignment determination means 60 are connected to the at least one beam receiver 50. The alignment determination means 60 deduce from said projected beam received a detected beam direction d(t) . Said detected beam direction d(t) is provided to the guided object control means 80.

An orientation determination device 90 is connected to the alignment determination means 60. The orientation determination device 90 implements the guided object orientation determination as a function of the direction of the detected offset ό(t) read from said detected beam direction d(t) and the predetermined direction of the offset o(t) applied to the primary beam direction dι(t).

Such orientation method and system could be used for raising the orientation ambiguity in any system transmitting a beam. In particular, it could be used in a beam riding guidance system, as for example guided ammunition control.

Claims

1. Orientation signalling method adapted for beam riding guidance using a guidance beam (B) for indicating a route to be followed by a guided object (G) characterised in that the relative position of the guidance beam (B) with respect to the guided object (G) is offset in a predetermined direction o(t) during a predetermined duration T.

2. Orientation signalling method according to claim 1, characterised in that the offset is implemented by moving the guided object (G) from the indicated route in the predetermined direction o(t) during the predetermined duration T.

3. Orientation signalling method according to the preceding claim characterised in that a direction dι(t) comprised in a guided object control signal c(t) and corresponding to the indicated route, is offset at a predetermined time to, during the predetermined duration T.

4. Orientation signalling method according to claim 1 characterised in that the offset is implemented by moving the guidance beam (B) in the predetermined direction o(t) during the predetermined duration T.

5. Orientation signalling method according to the preceding claim characterised in that a direction dι(t) comprised in a guidance beam control signal c(t) such as the guidance beam (B) indicating the route to be followed, is offset at a predetermined time to, during the predetermined duration T.

6. Orientation signalling method according to claim 4 or 5 characterised in that the predetermined duration T is short enough not to be taken into account by the guided object (G).

7. Orientation signalling method according to anyone of the preceding claims characterised in that the predetermined direction o(t) can be any direction including the direction parallel to sea or ground surface.

8. Orientation signalling device in which the orientation signalling method of anyone of the preceding claims is implemented characterised in that it comprises offset means (23,73) for modifying the relative position of the guidance beam (B) with respect to the guided object (G) in a predetermined direction o(t) during a predetermined duration T.

9. Orientation signalling device according to claim 7, characterised in that the offset means (23,73): - receives a direction d-ι(t) comprised in a guided object control signal c(t) and corresponding to the indicated route; - offsets said direction dι(t) at a predetermined time to, during the predetermined duration T; and - transmits said direction d(t) corresponding to the direction dι(t) outside the time interval [to, to+T] and to the offset direction d₂(t) during the time interval [to, to+T].

10. Orientation signalling device according to the claim 7 characterised in that the offset means: - receives a direction dι(t) comprised in a guidance beam control signal c(t) such as the guidance beam (B) indicating the route to be followed; - offsets said direction dι(t) at a predetermined time to, during the predetermined duration T; and - transmits said direction d(t) corresponding to the direction d-i(t) outside the time interval [t₀, to+T] and to the offset direction d₂(t) during the time interval [to, to+T.

11. Orientation determination method adapted for beam riding guidance using a guidance beam (B) for indicating a route to be followed by a guided object (G) characterised in that the orientation is determined as a function of an offset in the relative position of the guidance beam (B) with respect to the guided object (G) in a predetermined direction during a predetermined duration T.

12. Orientation determination method according to claim 10 characterised in that the detected offset ό(t) in the relative position of the guidance beam (B) with respect to the guided object (G) is determined and compared to the predetermined direction o(t) to deduce the orientation (ORT).

13. Orientation determination device in which the orientation determination method of anyone of claims 10 or 11 is implemented characterised in that it comprises: - Offset direction reading means (91) receiving a detected direction d(t) corresponding to the route indicated by the guidance beam (B) and detecting an offset ό(t) in said detected direction d t) corresponding to the offset (O) in the relative position of the guidance beam (B) with respect to the guided object (G); and - Orientation evaluation means (92) connected to said offset direction reading means (91 ), implementing a function of the direction of the detected offset ό(t) and the predetermined direction o(t).

14. Orientation system comprising the orientation signalling device (20,70) of anyone of claims 7 to 9 and the orientation determination device (90) of claim 12 which determines the guided object orientation using the offset o(t) implemented by the orientation signalling device (20,70).

15. Beam riding guidance system comprising: - A beam projector (30) transmitting linearly polarised waves; - Guidance beam control means (10) connected to said beam projector (30), orientating the beam projector (30) in a guidance beam direction d_b(t) given by beam riding guidance control signal c(t); - At least one beam receiver (50) placed in the rear of said guided object (G) and capable of receiving the projected guidance beam (B); - Alignment determination means (60) connected to the at least one beam receiver (50), deducting from said projected beam received a detected direction rf(t)and providing said detected direction to guided object control means (80); characterised in that it comprises an orientation system according to claims 12 or 13, - whose orientation signalling device (20,70) offsets the relative position of the guidance beam (B) with respect to the guided object (G) in a predetermined direction during a predetermined duration T; and - whose orientation determination device (90) detects the offset of the relative position of the guidance beam (B) with respect to the guided object (G) implemented by the orientation signalling device (20,70) and deduces the orientation from this said detected offset ό(t) and the predetermined direction o(t).

16. Beam riding guidance system according to the preceding claim comprising 2 orthogonal beam receivers (50).