RU2803141C1 - Monopulse radar system with reduced direction finding error - Google Patents

Abstract

FIELD: radars.

SUBSTANCE: monopulse radar system installed on a rotary-wing aircraft contains an antenna system, a receiver and a digital computing device containing a command memory. The composite and the residual outputs of the antenna system are connected to the corresponding inputs of the receiving device with its composite and residual outputs connected to the corresponding inputs of the digital computing device. The system additionally includes a sensor with the output connected to an additional input of the digital computing device. The sensor generates an impulse at a certain angular position of the main rotor blades of the aircraft relative to the construction axis of the aircraft. The command memory contains a sequence of commands executed by the digital computing device during the operation of the system, the specified sequence of commands implements determination of the relative angular position of the scan axis of the directional pattern of the aircraft and the angular position of the rotor blades of the aircraft for the target direction finding time point using the time of target location, the time of receipt of the next and the previous pulses from the sensor, and the value of the angular position of the aircraft main rotor blades at the time of generation of the pulse as measured by the system . The sequence of commands implements resolution to determine the bearing to the target, if the angular position of the scan axis of the direction pattern of the antenna system differs from the angular position of each blade of the main rotor of the aircraft at the time of measuring of the bearing to the object by a value not less than the specified one.

EFFECT: reduction to acceptable values of the direction finding error associated with periodic distortion of the directional pattern of the antenna system, as well as the possibility of using the system for direction finding of a target with a direction finding error reduced to acceptable values in the range of azimuthal directions of the scan axis of the direction pattern of the antenna from 0° up to 360° and use of the additional sensor signals entered into the system by other aircraft systems.

1 cl, 3 dwg

Description

The invention relates to the field of radar and can be used in radar systems that include an antenna system (AS), the radiation pattern of which is periodically distorted due to interaction with the rotating rotor of a rotorcraft.

Various monopulse radar systems are known from the prior art, having reduced errors in target direction finding (determining the angular direction of a target).

There is a known system for determining the coordinates of a target in a request-response system, protected by patent RU 2631117 C1. The system uses an antenna made in the form of a one-dimensional antenna array, the pattern of which has the form of a round funnel, with the axis of rotation of the funnel coinciding with the direction of opening of the array, as well as angular position sensors of the antenna directed at the target, a digital computing device capable of calculating the coordinates of the target at any position of the carrier and antenna on the carrier, and a height sensor. Increasing the accuracy of determining the target coordinates is achieved by the fact that the system uses a mathematical description of the antenna pattern, the deviation in the local coordinate system of the antenna of the direction of the response signals from the plane perpendicular to the direction of the antenna opening and passing through the center of the antenna opening, and the range to the target. The specified parameters are used to determine the plane in which the target is located (target bearing plane), perpendicular to the direction of the antenna opening. The target coordinates are calculated using mathematical expressions that determine the plane in which the target is located, the sphere of equal distance to the target, and the target height plane.

A monopulse radar system with increased accuracy in determining the target bearing and preserved interchangeability of the antenna as part of the system, protected by patent RU 2755796 C2, is also known, including an AS with a storage device that stores the characteristics of an AS instance in the form of coefficients of a power polynomial, and a computing device, which extracts the coefficients of a power polynomial and uses them to determine the bearing of a target by calculating the value of the power polynomial with the extracted coefficients. This system was accepted as a prototype.

These systems have the disadvantage that when placing the systems on a rotary-wing aircraft, it is impossible to avoid distortion of the directional pattern of the aircraft due to the interaction of the electromagnetic field of the aircraft with the structural parts of the aircraft (for example, with the rotor blades of the rotary-wing aircraft). Accordingly, when the electromagnetic field of the AC interacts with the rotor blades of the aircraft, for the first system, the antenna pattern known from the prior art will differ from a round funnel, and for the second system, known from the prior art, the distorted antenna pattern will be described by other values of the coefficients of the power polynomial. Depending on the current position of the aircraft's rotor blades, the antenna pattern will be periodically distorted as each aircraft's rotor blade passes near the antenna.

When installing these monopulse radar systems on rotary-wing aircraft, a technical problem arises that makes it impossible to meet the requirements for these systems in terms of the permissible value of target direction finding error. The technical problem is that the speaker pattern is periodically distorted due to a violation of the homogeneity of the electromagnetic field of the speaker, while target direction finding is carried out with additional errors arising from distortion of the speaker pattern. Due to the presence of the main rotor blade in the sector of the AS aperture, the uniformity of the electromagnetic field of the AS is periodically disrupted, which leads to distortion of the AS pattern. It can be shown that for a five-blade main rotor aircraft, only for a range of approximately 20 to 30% of the full angular sector between the blades, the distortion of the AS pattern (“shading” of the AS by the aircraft main rotor blades) is acceptable for the correct functioning of the monopulse radar system in terms of target direction finding. Only in this range of angular directions of the equi-signal direction (RSD) of the AP AP will the target direction-finding error of the monopulse radar system be acceptable.

The technical result achieved by the invention is to reduce to acceptable values the target direction finding error associated with periodic distortion of the monopulse radar system's aircraft pattern due to the periodic influence of the main rotor blade of a rotary-wing aircraft on the electromagnetic field of the aircraft. The technical result is achieved by the fact that at the development stage, including when testing prototypes of a rotary-wing aircraft, the angular value (specified value) of the deviation of the aircraft's DN from the angular direction of the aircraft's main rotor blade is determined (set) by calculation and/or experimentally, if it exceeds such that the blade does not have an unacceptable effect on the NPP bottom line. The monopulse radar system installed on a rotary-wing aircraft uses the specified specified value to determine the admissibility of target direction finding: if the current angular position of the aircraft's target direction finding system differs from the current angular position of each rotor blade of the aircraft by a value not less than the specified value, then the aircraft's target direction finding system is located in one from the “pure” angular intervals between the blades and direction finding of the target is possible if the current angular position of the aircraft's target navigation system differs from the current angular position of one of the aircraft's main rotor blades by a value less than the specified value, then the aircraft's target direction finding is located in the angular interval shaded by this blade (in “shaded” angular interval), and target direction finding is not performed.

An unexpected technical result achieved by the invention is the possibility of using a system for direction finding of a target with a direction finding error reduced to acceptable values in the range of azimuthal directions of the antenna pattern from 0° to 360° relative to the aircraft's construction axis.

Another unexpected technical result achieved by the invention is the possibility of using the signal from an additional sensor introduced into the system by other aircraft systems, for example, as a rotation angle converter with a pulse-forming element when implementing a method for assessing the technical condition of a mechanism with gears according to the author's certificate SU 1688658 A1.

During operation of the system, at the current moment, which is the time of target direction finding, the monopulse radar system determines the angular position of the aircraft's main rotor blades relative to the aircraft's construction axis and the angular position of the “shaded” angular intervals associated with the blades. Taking into account the angular position of the aircraft's target navigation system relative to the aircraft's construction axis at the time of target direction finding, the system determines the relative angular position of the aircraft's aircraft's aircraft's main rotor blades with the angular position of the aircraft's main rotor blades. The system determines whether the current angular position of the AS RP falls into one of the “shaded” angular intervals in which the corresponding blade unacceptably distorts the RP, and based on the results of the determination, it carries out or does not carry out direction finding of the target (or allows or does not allow direction finding of the target).

To determine the current position of the “shaded” angular intervals relative to the aircraft’s construction axis, an additional sensor connected to the system’s computing device is introduced into the system. The sensor generates a pulse (for example, electrical or light, followed by conversion into a form to which the system’s computing device is sensitive) at the moment the rotating rotor of the aircraft passes through the known angular position of the main rotor of the aircraft, determined by the design of the rotary-wing aircraft, relative to the construction axis of the aircraft. The system records (measures) the times of occurrence of the next and previous pulses from the sensor; from the measured values of the time of occurrence of pulses, it determines the time interval between the current moment, for which the possibility of direction finding of the target is determined, and the next pulse, and the time interval between the next and previous pulses. The system determines the current position of the “shaded” angular intervals relative to the aircraft’s construction axis using the value of the time interval between the current moment in time and the next received pulse, the value of the time interval between the next and previous received pulses, the known position of the aircraft’s main rotor blades at the moment the pulse was generated, and the specified value , which determines the angular interval within which the distortion of the electromagnetic field of the AC by the aircraft's main rotor blades exceeds the permissible limits.

The system checks the possibility of determining the angular direction to the target (the possibility of target direction finding) for the current moment in time, determining the current angular position of the aircraft's RSN relative to the current position of the aircraft's main rotor blades and the associated "shaded" angular intervals for each aircraft's main rotor blade. If the current direction of the RSN DN AS does not fall into any of the “shaded” angular intervals, then direction finding of the target at the current time is possible and carried out, and the system uses the results of direction finding to determine the angular coordinates of the target, otherwise signals from the target can be used for obtaining other characteristics of the target.

Thus, the inventive system ensures direction finding of a target exclusively during periods of time in which the aircraft's RPIN does not fall into any of the “shaded” angular intervals between the rotor blades of the aircraft, and the direction finding error caused by the distortion of the aircraft’s RP by the aircraft’s rotor blades, turns out to be acceptable for direction finding purposes.

The essence of the invention and its implementation is illustrated by the drawings of Fig. 1, Fig. 2 and Fig. 3.

In FIG. Figure 1 shows a block diagram of the system. In FIG. 1 depicts:

- antenna system AC 1, which has a total “out_Σ” and a difference “out_Δ” outputs;

- receiving device PrU 2, which has a total “in_Σ” and a difference “in_Δ” inputs, and a total “out_Σ” and a difference “out_Δ” outputs;

- digital computing device TsVU 3, which has a total “in_Σ” and a difference “in_Δ” inputs and an additional “in_dat” input for receiving an electrical pulse from the sensor;

- command storage device ZUK 4, which is part of the digital computing device 3;

- sensor 5;

- connections between the components of the system.

In FIG. 2, which explains the symbols of the main rotor blades of the aircraft and their relative position at the moment of impulse generation, are presented:

- rotary-wing aircraft;

- blades l1-l5 of the main rotor of a rotary-wing aircraft in a position corresponding to the moment of pulse generation;

- antenna system of the AS of a monopulse radar system, the antenna pattern of which or the AS itself is deployed in the direction of the target;

- angle ε of the position of the blade l1 of the main rotor of the aircraft at the moment of generation of the impulse and the direction of rotation of the blades;

- “shaded” angular intervals α, within which the influence of “shading” of the AS by the aircraft’s main rotor blades on the target direction finding error exceeds the permissible limits;

- “pure” angular intervals β, within which the influence of “shading” of the AS on the target direction finding error does not exceed acceptable limits.

In FIG. 3, which explains the position of the main rotor blades of the aircraft at the time of target direction finding, are presented:

- rotorcraft aircraft;

- blades l1-l5 of the main rotor of a rotary-wing aircraft at the time of target direction finding;

- antenna system of the AS of a monopulse radar system, the antenna pattern of which or the AS itself is deployed in the direction of the target;

- “shaded” angular intervals α, within which the influence of “shading” of the AS by the aircraft’s main rotor blades on the target direction finding error exceeds the permissible limits;

- “pure” angular intervals β, within which the influence of “shading” of the AS on the target direction finding error does not exceed acceptable limits;

- current angular position θ1 of the aircraft main rotor blade l1 relative to the aircraft’s construction axis;

- angular direction ϕ_рсн RSN DN AS relative to the construction axis of the aircraft.

The essence of the invention is that:

- into a monopulse radar system installed on a rotary-wing aircraft, wherein the AS pattern is periodically distorted as a result of the interaction of the AS with the rotor blades of the aircraft, containing the AS, a receiving device and a digital computing device (DCU) containing a command memory device (CMU), while the total and difference outputs of the AC are connected to the corresponding inputs of the receiving device, the total and difference outputs of which are connected to the corresponding inputs of the digital control unit, an additional sensor is introduced, the output of which is connected to the additional input of the digital digital control unit, generating a pulse at a certain angular position of the main rotor blades of the aircraft relative to the construction axis of the aircraft;

- the ZUK includes a sequence of commands executed by the central control unit during operation of the system, which implement the determination of the mutual angular position of the equi-signal direction (RSD) of the directional pattern (DP) of the AS and the angular position of the aircraft's main rotor blades for the moment of time of target direction finding using the time point of target direction finding measured by the system , the time instants of receipt of the next and previous pulses from the sensor and the value of the angular position of the aircraft's main rotor blades at the moment of generation of the pulse, and allowing the determination of the angular direction to the target, if the angular position of the aircraft's DN RP differs from the angular position of each aircraft's main rotor blade at the time of determination angular direction to the object to a value not less than the specified one. The sequence of commands executed by the digital control unit during system operation implements the following actions:

1. When the next pulse is generated by the sensor, the system records the moment in time t1 of the appearance of the next pulse, corresponding to the angle ε of the position of the aircraft’s main rotor blade l1 relative to the aircraft’s construction axis.

2. Using the previously recorded time t2 of the appearance of the previous pulse, the system calculates the difference

T=t1-t2,

which corresponds to the period of the previous full rotation of the main rotor of the aircraft.

3. When finding a target, the system records the current time (time of target direction finding) tcur and calculates the difference:

T2=tcur-t1,

proportional to the rotation of the main rotor blades of the aircraft from a fixed position corresponding to the angle ε (the position at which the sensor generates a pulse), to the position of the blades at the target direction finding time tcur at the current rotation of the main rotor of the aircraft (Fig. 3 shows the current angular position 01 of the blade l1 ).

4. The system calculates the angular positions of the aircraft's main rotor blades relative to the aircraft's construction axis at the target direction finding time tcur, using the difference T2 between the current target direction finding time and the time of receiving the next impulse from the sensor, as well as the period T of the previous full rotation of the aircraft's main rotor. The error introduced by the angular acceleration of the main rotor of the aircraft when using the time of the previous revolution on the current revolution of the main rotor of the aircraft is negligible, because the angular acceleration of the main rotor of the aircraft is insignificant due to the large moment of inertia of the main rotor, and is not taken into account by the system.

For a five-bladed (N=5) aircraft main rotor, the system calculates the angular positions for each blade as follows:

- angular position of blade l1:

θ1=(ε+0*(2*π/N)+(2*π/T)*T2) mod (2*π);

- angular position of the blade l2:

θ2=(ε+1*(2*π/1M)+(2*π/T)*T2) mod (2*π);

- angular position of the blade l3:

θ3=(ε+2*(2*π/N)+(2*π/T)*T2) mod (2*π);

- angular position of the blade l4:

θ4=(ε+3*(2*π/N)+(2*π/T)*T2) mod (2*π);

- angular position of the blade l5:

θ5=(ε+4*(2*π/N)+(2*π/T)*T2) mod (2*π);

With a different number of aircraft main rotor blades, the formulas for calculating the angular positions of each blade change accordingly.

The first term of the submodular expression of each formula reflects the angular position of the first blade at the moment of generation of the impulse, the second term reflects the angular displacement of the corresponding blade relative to the first blade, the third term reflects the angular displacement of the blades at the time of direction finding of the target relative to their known angular position at the time of generation of the next impulse. The calculation of the modulo expression (2*π) is performed to limit the value of the angular position of the blades to the range from 0 to (2*π).

5. The system calculates the boundaries βx1, βx2 (where x is the number of the angular interval) of “pure” angular intervals (within which the influence of the “shading” of the AS on the target direction finding error does not exceed acceptable limits) at time tcur as follows:

- boundaries of the first “pure” angular interval between blades l1 and l2:

β11=θ1+α/2;

β12=θ2-α/2;

- boundaries of the second “pure” angular interval between blades l2 and l3:

β21=θ2+α/2;

β22=θ3-α/2;

- boundaries of the third “pure” angular interval between blades l3 and l4:

β31=θ3+α/2;

β32=θ4-α/2;

- boundaries of the fourth “pure” angular interval between blades l4 and l5:

β41=θ4+α/2;

β42=θ5-α/2;

- boundaries of the fifth “pure” angular interval between blades l5 and l1:

β51=θ5+α/2;

β52=θ1-α/2;

In the above expressions, α/2 is the specified value of the deviation of the aircraft's bottom level from the direction of the aircraft's main rotor blade, above which the blade does not have an unacceptable effect on the aircraft's bottom.

With a different number of aircraft main rotor blades, the formulas for calculating the boundaries of angular intervals change accordingly.

6. In accordance with the algorithm performed for the angular intervals between each pair of blades, the system determines whether the current RSN of the AS is in one of the “pure” angular intervals:

7. In accordance with the results of the analysis according to clause 6, at the current moment in time the system carries out direction finding of the target if the ASR of the aircraft is located in one of the “pure” angular intervals between the blades of the rotating main rotor of the aircraft (i.e. the angular position of the ASR of the aircraft is different from the angular position of each main rotor blade of the aircraft to a value not less than the specified one), otherwise the system does not carry out direction finding of the target at the current moment in time.

Claims (1)

A monopulse radar system installed on a rotary-wing aircraft (AC), containing an antenna system (AS), a receiving device and a digital computing device (DCU) containing a command memory device (CMU), while the total and difference outputs of the AS are connected to the corresponding inputs of the receiving a device, the total and difference outputs of which are connected to the corresponding inputs of the central digital device, characterized in that the system additionally includes a sensor, the output of which is connected to an additional input of the digital digital device, generating a pulse at a certain angular position of the main rotor blades of the aircraft relative to the construction axis of the aircraft, and the composition ZUK introduced a sequence of commands executed by the central control unit during operation of the system, which implement the determination of the mutual angular position of the equi-signal direction (RSN) of the directional pattern (DP) of the AS and the angular position of the aircraft's main rotor blades for the time instant of target direction finding, using the time instant of target direction finding measured by the system, instants of time receiving the next and previous pulses from the sensor and the value of the angular position of the aircraft's main rotor blades at the moment the pulse is generated, and allowing the determination of the angular direction to the target, if the angular position of the aircraft's DN RP differs from the angular position of each aircraft's main rotor blade at the time of determining the angular direction on object to a value not less than the specified one.

Images