A guidance device designed to be mounted on a mortar.

Abstract

A guidance device (1) for mounting on a mortar, comprising a housing equipped with: a camera (CAM) with a wide-angle lens configured to capture a field of view greater than 120°, and with at least 2200 pixels per line; a 3-axis accelerometer having a measurement range of ±2 g and a 3-axis gyroscope with a sampling frequency of at least 200 Hz; an electronic control unit (ECU) configured to manage the data transmitted by the camera (CAM) and by the accelerometer and gyroscope; and a processing module (PM) configured to output, to a visual communication interface, the current values ​​of the azimuth, elevation, and roll angles of the device from the camera (CAM) and accelerometer and gyroscope data transmitted by the electronic control unit (ECU). Figure for the abstract: [Fig. 2]

Description

Title of the invention: Orientation device intended to be mounted on a mortar.

[0001] The invention relates to an orientation device intended to be mounted on a mortar, a light artillery weapon.

[0002] Before firing a mortar, it is essential to correctly orient the weapon barrel, i.e. to give it the correct angle in azimuth and elevation. This function has been carried out for decades by a mechanical and optical means called a goniometer. The use of this angle measuring instrument requires specific training, as well as, in the field, significant attention and operational time.

[0003] The invention aims to enable automatic measurement of the angles of the weapon barrel and to provide the operator, or soldier responsible for supplying an artillery piece, with the manipulations to be applied to achieve the objective angles.

[0004] This orientation operation is called pointing the mortar tube.

[0005] Aiming a mortar-type weapon involves giving it the correct azimuth and elevation angles.

[0006] As illustrated in [Fig.l], the azimuth angle corresponds to the angle between the horizontal projection of the gun barrel and the geographic North, and the elevation angle corresponds to the angle between the barrel axis and the horizontal plane in the vertical plane passing through the barrel axis.

[0007] These two angles are essential to allow the mortar to reach a predetermined target and their calculation is the subject of the weapon's fire control. The roll has no impact on the range of the shot, however, the tube being connected by a solid connection to the body of the mortar (base, wheels, etc.), knowledge of the roll makes it possible to know the tilt of the weapon, knowing that it is preferable to have a zero tilt when adjusting the orientation of the tube (flat adjustment for handling the goniometer).

[0008] Prior to firing a mortar, for example 81 mm or 120 mm, a team specialized in topography plants a stake about a hundred meters in front of the mortar and records the azimuth of the line passing through the goniometer and the stake. Sighting this stake in the eyepiece of the goniometer thus makes it possible to determine the azimuth of the mortar tube by means of an angularly graduated horizontal plate. The tube elevation is measured using a spirit level fixed to a graduated vertical plate of the goniometer. The adjustment of the angles of the mortar tube is therefore carried out manually using the graduated plates of the goniometer, the goniometer having to be kept flat on the mortar chassis for correct adjustment of the angles.

[0009] It is known to use a mortar orientation device comprising a go niometer, combining the use of an optical sight to detect a stake to determine the azimuth of the tube, with that of a spirit level to determine the elevation of the tube relative to the horizontal. The validity of the measurements requires that the graduated plates be respectively horizontal for the azimuth measurement and vertical for the elevation measurement. This system requires prior to firing the intervention of a team specialized in topography for the precise measurement of the azimuth of the line connecting the goniometer to the stake. In addition, this system is robust and does not require a power source to operate, with the exception of a small light source in the eyepiece to distinguish the sight from the eyepiece. The use of this system nevertheless requires prior training, and the measurement is not available electronically.

[0010] This is the historical method, relying solely on mechanics and optics. It offers good reliability and correct precision, but at the cost of mobilizing a dedicated and specialized topography team, and only if it is operated by personnel specifically trained in these meticulous and relatively complex adjustments. In addition, the pointing data cannot be transmitted to third-party systems or people via an electronic network.

[0011] Also known is document US 10444030 relating to an OptoWOM II orientation device from the company INERTIAL LABS, which combines the use of a gyro-stabilized magnetic sensor for finding and maintaining North (or INF for "Initial North Finding" in English) with inertial sensors as well as two image sensors to improve the magnetic calibration and orientation of the mortar. The use of magnetic sensors in an environment with many metal parts, such as that of a mortar, complicates the calibration phase for this type of sensor and limits the accessible precision to a few thousandths (3 thousandths announced).

[0012] One thousandth corresponds to -¾ rad « 0.982 mrad-

[0013] This device offers a precision that remains limited in azimuth: 3 thousandths despite complex magnetic calibration algorithms. Its cost does not seem compatible with mortars either.

[0014] Also known is a Vingpos orientation device from Vinhog AS (Rheinmetall), which combines a dual GPS antenna for initial north search, with inertial sensors for measuring current angular displacements, as well as a telescope for aligning the second GPS antenna with the mortar tube. This dual GPS antenna technology requires the availability of the GNSS system but allows to achieve 2 thousandths for the initial azimuth. This system is subject to drift of the inertial sensors.

[0015] Subject to the availability of the GNSS system, this device provides an interesting azimuth accuracy of 2 thousandths announced. However, the measurement of current angles is ensured by inertial sensors (gyrometers) subject to their temporal drift, and for which the figures are not communicated.

[0016] Also known is document US 9052159 B2 disclosing the use of optical angle of arrival (OAOA) sensors, for the acronym "Optical Angle Of Arrival" in English, coupled to point sources, at least one of which has a perfectly known orientation thanks to the use of a North / Vertical search means. The device presented in this document allows the spatial orientation of the device on which one or more OAOA sensors are mounted, the number of OAOA sensors being able to obtain coverage of up to 360° of field of view or FOV for the acronym "Field Of View" in English. The stationary sources can be multiplied and are equipped with OAOA sensors to allow the control of the intervisibility of the OAOA sensors.

[0017] This device is based on the networking of OAOA sensors, with a certain complexity in the device and in the processing used. An initial search module for the North and Vertical directions is essential, and the calculation of the current angles of the mortar tube is dependent on the entire chain (harmonization on a source stake, optical measurement of the laser cross, and processing). Document US 9052159 B2 does not give figures as to the precisions obtained, whether in azimuth or in elevation. In addition, this device requires at least the harmonization of two objects: - an OAOA sensor mounted on the tube, to be harmonized with the latter, - an OAOA sensor mounted on at least one source stake, to be harmonized with the initial search module for the North and Vertical directions which will be temporarily mounted on the stake during initialization.

[0018] This last observation is not neutral with regard to the cost of the final orientation system. In addition, the proposed system remains complex and seems complicated to implement in a military context where the aspects of robustness, simplicity, lightness and minimal maintenance are very important.

[0019] An aim of the present invention is to provide in real time a direct measurement of the angles of the tube of a mortar, as well as the instructions to be applied (i.e. cranks to turn) to reach the angles planned for the future shot.

[0020] According to one aspect of the invention, there is provided an orientation device intended to be mounted on a mortar, comprising a housing provided with: - a camera equipped with a wide-angle lens configured to capture a field angle greater than 120°, and at least 2200 pixels per line; - a 3-axis accelerometer with a measurement range of ±2 g and a gyrometer

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[0030] three-axis sampling rate of at least 200 Hz; - an electronic control unit configured to manage the data transmitted by the camera and by the inertial unit; and - a calculation module configured to output, to a visual communication interface, the current values ​​of the azimuth, elevation and roll angles of the device from the data from the camera and the accelerometer and gyrometer, transmitted by the electronic control unit. 1g corresponds to 9.806 65 m.s2. According to one embodiment, the accelerometer and the gyrometer are integrated into an inertial unit without a magnetometer. In one embodiment, the electronic control unit is configured to: - perform processing of images provided by the camera, matching points of interest in different images making it possible to calculate azimuth, elevation and roll angle values; and - merge azimuth, elevation and roll angle values ​​obtained by image processing and provided by the accelerometer and gyrometer. In one embodiment, the calculation module is configured to output respective deviations between the values ​​of the azimuth, elevation and roll angles delivered by the electronic control unit, and the firing setpoint values ​​of the azimuth, elevation and roll angles, to enable firing correction maneuvers. According to one embodiment, the device further comprises an antenna for receiving GNSS signals. In one embodiment, the device comprises at least one stake intended to be a reference element in the images transmitted by the camera. According to one embodiment, the device comprises at least three stakes each provided with a light source, intended to be reference elements in the images transmitted by the camera. According to one aspect of the invention, there is also provided a mortar equipped with an orientation device as previously described, and a visual communication interface. According to one embodiment, the calculation module is included in the electronic control unit. Alternatively, the calculation module is external to the electronic control unit. According to one aspect of the invention, there is also proposed a method for managing the operation of a mortar equipped with an orientation device, as previously described, comprising a prior step of angular calibration in the factory of the camera, of the accelerometer and the gyrometer.

[0031] In one embodiment, the method comprises the steps of: - planting at least one stake between 30 and 100 meters in front of the mortar in the camera's field of vision; - installation of the orientation device on the mortar; - Identification of the azimuth of the camera / stake line(s); - Switching on the orientation device: information via an interface of the azimuth of the line(s) (camera / stake); - Detection of the stake(s) by the camera and azimuth measurement, and elevation measurement from the accelerometer and gyrometer data; - Measurement of current angles by fusion of data from the camera and the accelerometer and gyrometer; and - Provision of firing instructions for azimuth, elevation and roll angles, to enable fire correction maneuvers.

[0032] The invention will be better understood by studying some embodiments described as non-limiting examples and illustrated by the appended drawings in which: - [Fig.l] schematically illustrates the characteristic angles of a mortar tube, according to the state of the art; - [Fig.2] schematically illustrates an orientation device intended to be mounted on a mortar, according to one aspect of the invention; - [Fig.3] schematically illustrates an orientation device of [Fig.2] mounted on a mortar, according to one aspect of the invention; - [Fig.4] schematically illustrates a method of operating a device, according to one aspect of the invention; and - [Fig.5] schematically illustrates an example of an interface for providing angular instructions.

[0033] Throughout the figures, elements having identical references are similar.

[0034] In [Fig.2], an orientation device 1 intended to be mounted on a mortar, according to one aspect of the invention, comprises a housing 2 provided with: - a CAM camera equipped with a wide-angle lens configured to capture a field angle greater than 120°, and at least 2200 pixels per line; - an IMU_AG inertial unit comprising a 3-axis accelerometer having a measurement range of ±2 g, a three-axis gyrometer with a sampling frequency of at least 200 Hz, and without a magnetometer; - an electronic control unit ECU configured to manage the data transmitted by the CAM camera and by the IMU_AG inertial unit; and - an MC calculation module configured to deliver output to a visual communication interface, the current values ​​of the azimuth, elevation and roll angles of the device from the data of the CAM camera and the IMU_AG inertial unit transmitted by the electronic control unit UCE.

[0035] In the examples described, the orientation device comprises an inertial unit IMU_AG, comprising a 3-axis accelerometer, a three-axis gyrometer, and without a magnetometer, but as a variant, the device can comprise only such an accelerometer and such a gyrometer, without them being in an inertial unit, and transmit their measurement data to the calculation module MC.

[0036] The electronic control unit ECU is configured to: - perform processing of images provided by the camera (CAM), matching points of interest in different images to calculate azimuth, elevation and roll angle values; and - merge azimuth, elevation and roll angle values ​​obtained by image processing and provided by the IMU_AG inertial unit.

[0037] This data fusion makes it possible to ensure the redundancy of measurements and guarantee the reliability of the system, which is a very important characteristic for a weapon system.

[0038] The advantages of this orientation device are as follows: - remain compatible with the current guidance system of existing mortars (principle and mechanical mounting on the weapon); - provide direct measurement of mortar tube angles (azimuth, elevation and roll) without requiring any manipulation by the crew (no aiming in an eyepiece, no manipulation of the graduated screws of a goniometer); - provide clear and simple orders to achieve the target firing angles (provided by an external firing control system, which is not the subject of this patent); - make this real measurement available to higher command (connected electronic object). - have a measurement accuracy higher than the current accuracy. - improve the reliability of input data: the fusion of image / inertial unit data makes input data more reliable.

[0039] The orientation device 1 may further comprise an antenna ANT for receiving GNSS signals, and its support S_ANT.

[0040] This orientation device 1 can be fixed in place of the current goniometer on existing mortars as illustrated in [Fig.3]. The procedure for obtaining the current angles of the mortar is illustrated in [Fig.4].

[0041] A first step El includes planting at least one stake P between 30 and 100 meters in front of the mortar in the camera's field of vision or FOV for acronym of "Field Of View" in English.

[0042] A second step E2 comprises the installation of the orientation device 1 on the mortar in place of the current goniometer. The orientation of the orientation device 1 relative to the mortar tube M is known (factory harmonization).

[0043] A third step E3 comprises the orientation of the line connecting the camera CAM to each stake P relative to the geographic North (The method for obtaining the azimuth of the camera / stake line can be easily obtained by GNSS surveys with one or two antennas, the second antenna then being on the stake. In the absence of a GNSS antenna on the orientation device 1, the measurement can be made with an external GNSS, by temporarily placing an external antenna above the stake and above the orientation device. For a night measurement, at least three stakes P equipped with a light source are required. The azimuth of these two additional camera / stake lines will not necessarily be known, but may allow obtaining better precision with regard to knowledge of the North, by averaging over the at least three azimuths obtained.

[0044] A fourth step E4 comprises the starting or switching on of the orientation device 1, and the information via a visual communication interface of the azimuth of the camera line(s) CAM / stake P. As a variant, it is also possible to implement an automatic transmission of the GNSS coordinates of the stake(s) to the calculation module MC.

[0045] In a fifth step E5, the orientation device 1 equipped with its wide-angle camera automatically detects the stake(s) in its field of vision and measures the azimuth. The inertial unit IMU_AG directly provides the data necessary for determining the elevation.

[0046] The detection of the stake(s) P allows the orientation device 1 to know the geographic North, the inertial unit IMU_AG provides the knowledge of the vertical. The image processing and the accelerometer processing are done in the control unit UCE or in the calculation module MC, which can be on board the orientation device 1 or remoted on a computer external to the orientation device 1 (PDA type for example), with a data link (wired or aerial) between the two.

[0047] A sixth step E6 comprises a measurement of the current angles. From the initialization step E5, the orientation device continuously provides the three angles of the mortar M (azimuth, elevation and roll) without action on the part of the crew. This measurement is carried out using image processing which matches characteristic elements of the environment of the mortar M (stakes P, points of interest, etc.) from one image to another. The image processing used can be of the SIFT type, which stands for "Scale Invariant Feature Transform". The changes in orientation detected between each image and calculated by the system are confirmed by the IMU_AG inertial unit by data fusion. This aspect of data fusion is very important to guarantee the reliability of the measurements obtained, especially since this is a measuring instrument used to carry out a shot. The angles are provided before and after the shot (the orientation device 1 must survive the shocks or strong accelerations of the shots). It should be noted that the orientation device 1 is not sensitive to the drift of its sensors because the main principle of the measurement is the difference between two images of the environment of the mortar M: the orientation device 1 can even be switched off during a shot, the post-shot image compared to the pre-shot image gives information on the angular differences between these two images.

[0048] A seventh step E7 comprises providing instructions. Knowledge of the current angles of the mortar M at each instant makes it possible to provide the crews with clear indications for reaching the target angles of the next shot of the mortar M. The target angles are given by the Fire Control (Computer external to the orientation device), the instructions for reaching these angles can be displayed on the screen of the computer external to the orientation device 1, or on the visual communication interface, as illustrated in [Fig.5].

[0049] The present invention makes it possible to meet the need for measuring the current angles of a mortar (azimuth, elevation and roll) in its environment, by providing ease of use for the operators. The orientation device of the present application allows automatic and precise measurement of the angles without specific action by the operators, which is not the case with the use of a goniometer.

[0050] The present invention is at least as precise as the method with goniometer, an accuracy of less than 3 thousandths has been simulated. In addition, the orientation device is installed in place of the current goniometer and remains compatible with the old pointing procedure.

Claims

1.

2.

3. Claims Orientation device (1) intended to be mounted on a mortar, comprising a housing provided with: - a camera (CAM) equipped with a wide-angle lens configured to capture a field angle greater than 120°, and at least 2200 pixels per line; - a 3-axis accelerometer with a measurement range of ±2 g and a three-axis gyrometer with a sampling frequency of at least 200 Hz; - an electronic control unit (ECU) configured to manage the data transmitted by the camera (CAM) and by the accelerometer and the gyrometer; and - a calculation module (CM) configured to output, to a visual communication interface, the current values ​​of the azimuth, elevation and roll angles of the device from the data of the camera (CAM) and the accelerometer and gyrometer, transmitted by the electronic control unit (ECU) the accelerometer and the gyrometer being integrated into an IMU_AG inertial unit without a magnetometer, the device comprising an antenna (ANT) for receiving GNSS signals, and at least one stake (P) intended to be a reference element in the images transmitted by the camera (CAM). Device according to claim 1, wherein the electronic control unit (ECU) is configured to: - perform processing of images provided by the camera (CAM), matching points of interest in different images to calculate azimuth, elevation and roll angle values; and - merge azimuth, elevation and roll angle values ​​obtained by image processing and provided by the accelerometer and gyrometer. Device according to one of the preceding claims, in which the The calculation module (CM) is configured to output respective deviations between the values ​​of the azimuth, elevation and roll angles delivered by the electronic control unit (ECU), and the firing setpoint values ​​of the azimuth, elevation and roll angles, to enable firing correction maneuvers.

4. Device according to one of the preceding claims, comprising at least three stakes (P) each provided with a light source (L), intended to be reference elements in the images transmitted by the camera (CAM).

5. Mortar (M) equipped with an orientation device (1) according to one of the preceding claims, and with a visual communication interface.

6. Mortar (M) according to claim 5, wherein the calculation module (MC) is included in the electronic control unit (ECU), or is external to the electronic control unit (ECU).

7. Method for managing the operation of a mortar (M) equipped with an orientation device (1), according to one of claims 5 or 6, comprising a prior step of angular calibration in the factory of the camera (CAM), the accelerometer and the gyrometer.

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