Ordnance – Mounts – Training mechanisms
Reexamination Certificate
1998-09-16
2001-03-20
Johnson, Stephen M. (Department: 3641)
Ordnance
Mounts
Training mechanisms
C089S041140
Reexamination Certificate
active
06202535
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention concerns the field of sighting or aiming instruments. Its subject matter is more particularly a device capable of determining the direction of a target in a predefined frame of reference, the device having sighting means and means for processing signals derived from the sighting means, the processing means being capable of determining the direction between the sighting means and the target and transmitting them to imaging means or to external means.
Numerous devices exist which are capable of determining, in particular, the elevation and azimuth of a target.
For example EP 557 591 describes a device capable of determining the orientation of an object with respect to a reference orientation, and comprises a movable orientation unit and a reference sensor unit, each one of them having a three-axis gyroscopic unit, a calculation unit receiving measured values from the aforesaid units, and an output unit.
Many of these devices require substantial logistics. However, in certain circumstances it may prove necessary or indeed vital to use a lightweight and manageable device that can be used by a single operator.
Such devices exist, and use magnetic field sensors.
Among these devices, the binoculars sold under the LEICA trade name are capable of determining the elevation and azimuth of a target, and give complete satisfaction when used outdoors. They cannot be used, however, in an environment having magnetic disturbances.
Other devices analyze electrostatic or electromagnetic fields and, by reading their cartography, determining the position and direction of a target.
The devices are satisfactory in environments which are completely known and of small dimensions. They are difficult to use, however, and do not tolerate changes in the electrical environment.
Also known is U.S. Pat. No. 4,012,989, which describes a helicopter having a device for determining the direction of a target so as to direct a movable weapon system. The device for determining the direction of a target has a movable sighting member equipped with two integrated inertial gyroscopes, resetting means integral with the helicopter equipped with two gyroscopes, and means for slaving the direction of the weapon as a function of the data supplied by the gyroscopes. The resetting means serve to immobilize the four gyroscopes in a first reference position to define a frame of reference. When the sighting means are disengaged from the resetting means, the four gyroscopes are released. The gyroscope pair integrated with the resetting means then rotates as a function of the movements of the helicopter. The gyroscope pair integrated with the sighting member rotates as a function of the movements of the helicopter and the movements of the gunner controlling the sighting member. The weapon is directed in real time toward the target as a function of the difference in rotation between the two gyroscope pairs.
This device has numerous drawbacks. For example, the gunner is obliged to keep the sighting means continuously pointed toward the target until the weapon system is fired, which limits firing capabilities and makes the helicopter vulnerable if multiple targets are present. Because of helicopter vibrations and uncontrolled wrist movement, the two gyroscopes of the sighting means transmit to the processing means sequences of signal changes which cause an accumulating measurement error which impairs the accuracy with which the target direction is determined. On a ship, if the sea is rough and there is thus severe pitching and rolling, it would be almost impossible to orient the weapon system toward the target with such a device.
SUMMARY OF THE INVENTION
One of the purposes of the invention is to propose a lightweight and manageable device capable of accurately and rapidly determining the elevation and azimuth of a target, and usable regardless of the type of environment.
The solution proposed is a device capable of determining the direction of a target in a predefined frame of reference, and of the type having sighting means, means for resetting those sighting means, and means for processing signals derived from the sighting means, those processing means being capable of determining representative values of the direction between the sighting means and the target and transmitting them to imaging means or to external means, the device being characterized in that the sighting means have a sighting member, three gyrometers arranged along three axes that are substantially perpendicular to one another, and means for controlling the transmission, to the imaging means or external means, of values representing the direction between the sighting means and the target.
According to a particular advantageous characteristic, the device has three optical gyrometers, for example fiber-optic gyrometers.
According to a characteristic which limits the risk of damage to these gyroscopes, only their coils are arranged on the sighting means.
According to a particular characteristic which allows accurate positioning of the sighting means in the resetting means, the sighting means have elements capable of coacting with elements of the resetting means.
According to an additional characteristic, the first elements are constituted by three pads, one with a conical recess, the second having a plane surface, while the other elements are constituted by pins of conical shape.
According to one characteristic, the processing means have a source of electrical power and calculation and information management means using a software program which performs several functions.
According to a particular characteristic, the software program performs three principal functions:
the target designation function, which acquires data from the sighting instrument and processes the data obtain the desired elevation and azimuth;
the transmission function, which sends azimuth and elevation data for display on the imaging means and/or to a weapon system;
the resetting function, which allows the drift of the sighting instrument due to the utilization of gyrometers to be corrected at regular intervals.
According to a particular characteristic, the software program additionally performs the function of displaying the operational state of the elements of the invention.
It is also known that the values emitted by the gyroscopes drift (change), particularly in terms of time and temperature, and the gyroscopes require static and dynamic calibration.
Patents EP 717 264 and EP 496 172 describe methods for correcting gyrometer biases and means for implementing them.
The former concerns the correction of gyrometer biases on an aircraft, and the latter on a vehicle. In both cases, gyroscopic calibration is performed when the aircraft or vehicle is in a stationary position.
To obtain good accuracy, however, it is necessary to compensate for gyroscopic drift at all times, and not just in a stationary position.
It is also known that a complex model of the trajectory of the gyroscopic data is needed to obtain good integration results. Signal processing means that are powerful and bulky, and thus not transportable, are used for that purpose.
One of the purposes of the invention is to propose a method for processing signals derived from gyroscopes which yields good results and does not require powerful signal processing means.
The solution consists in proposing a method for integrating gyroscope data consisting in performing in succession, based on gyroscope values obtained between a time t0 and time t1, first calculations using a complex model which, given the processing capacity of the processing means, cannot function in real time but does yield accurate results, and then, based on gyroscope values obtained between time t1 and t2, second calculations using a simplified model that can be implemented in real time.
According to another characteristic, the software program performs a function to correct the drift of the gyrometers between two successive resetting.
According to an additional characteristic, the sighting means have at least one temperatur
Alhadef Bernard
Philibert Guy
Johnson Stephen M.
L'Etat Francais, represente par le Delegue Ministeriel pour
Oliff & Berridg,e PLC
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