RU2211462C2 - Follow-up optoelectronic system - Google Patents

Abstract

FIELD: systems for surveillance and follow up of objects in space, predominantly from mobile base. SUBSTANCE: follow-up optoelectronic system includes guidance and stabilization unit and optoelectronic direction finder connected in series, converter of coordinates from measurement system of direction finder to stabilized coordinate system, circuit of smooth entry of error, correction unit, converter of stabilized coordinates to actuating system of coordinates of guidance and stabilization unit connected in series. Input of converter of coordinates from measurement system of direction finder to stabilized system of coordinates is connected to output of optoelectronic direction finder and output of converter of stabilized coordinates to actuating system of coordinates of guidance and stabilization unit is connected to input of guidance and stabilization unit. EFFECT: increased probability for transfer to automatic tracking, raised maximum range of possible transfer to automatic tracking and enhanced precision of tracking of objects by follow-up optoelectronic system. 3 cl, 3 dwg

Description

 The invention relates to the field of systems for monitoring and tracking objects in space, mainly from a moving base.

 Known television-optical tracking system with a tracking strobe containing a television camera, a television machine, which includes a video signal processing device, a solver, an integrator and a driver, as well as an actuator (guidance drive) ([1] p. 232, Fig. 7.17 )

 The disadvantage of this system is the rather large discrepancies between the position of the optical axis of the optoelectronic device (camera) and the line of sight when tracking dynamic objects from a moving base due to the lack of a stabilization system for the optical line of sight and the inertia of the actuator.

 An optoelectronic device is also known ([2] p. 110-112, Fig. 3.23), which consists of interconnected optoelectronic direction finder and a drive with a power amplifier. This system has inputs for receiving an optical signal, external target designation and correction. In the process of tracking, the direction finder to the object is driven by signals from the direction finder. The disadvantage of this system is the lack of quality meters, which makes it difficult to use this system on media exposed to quality. In addition, the lack of functional blocks for issuing the exact coordinates of the object relative to the optical axis of the optoelectronic direction finder does not allow for the automatic capture of the object for tracking.

 A known tracking system ([2] p. 228, 229, Fig. 6.7), consisting of series-connected translational motion sensor, calculator, gyrostabilizer, direction finder and power amplifier, the output of which is connected to the second input of the gyrostabilizer. This system allows you to work with a swinging base. However, due to the fact that a gyro drive is used for stabilization, there is no practical possibility of stabilizing massive optical devices, i.e. devices with large focal lengths and diameters of the entrance pupil. This does not allow tracking objects located at long range or having low contrast relative to the background. This system is also incapable of automatically capturing an object for tracking.

 The literature also describes a tracking system ([2] p. 229, 230, Fig. 6.8), consisting of series-connected angular velocity sensor, adder, power amplifier, engine and direction finder. The direction finder output is connected to the second adder input. In this system, the angular velocity sensor, adder, power amplifier, and motor act as guidance and stabilization devices. In this system, capturing an object for auto tracking is possible only by accurately combining the image of the object with a strobe (analysis window), which is difficult when the position of the object and strobe in the picture plane of the direction finder is significantly mismatched. In addition, the lack of devices for dynamic correction does not allow to sufficiently realize the capabilities of the actuator.

 Closest to the proposed invention is a television optical system ([3] p. 8 and 9, Fig. 4), containing a series-connected television sensor, a signal amplification and processing device, a computing device (together forming a direction finder) and an actuator. The executive body, which performs the functions of the guidance and stabilization unit, is kinematically connected with an optical-electronic (television) direction finder device.

In the known system, the transition to automatic mode is carried out by preliminary deploying the direction finder to the object intended for tracking so that it is within the capture window within the field of view. Moreover, in the known system, unacceptable transients occur when switching to auto tracking. This is due to the fact that with increasing angular velocities and accelerations of moving the image of the object relative to the photodetector (optical axis of the direction finder), the probability of transition to the automatic tracking mode decreases. This is explained by a decrease in the contrast of the image of an object moving relative to the raster (see [3], pp. 209-212). This circumstance can lead to a breakdown in auto tracking and significantly affects tracking accuracy due to distortion of the image of the object (the appearance of a loop behind the image of the object moving relative to the raster). Transients are caused by the following circumstances. Let the target designation data come from one of the systems of the complex, which includes the optoelectronic system, for example, a location station. Moreover, at the time of autocapture by the optoelectronic system, there is always an initial mismatch between the position of the image of the object and the optical axis of sight of the optoelectronic device (3 mrad or more) due to unavoidable errors of both target designation and dynamic errors of the guidance and stabilization unit when parrying the quality of the base . The direction finding machine determines the coordinates of the image of the object and gives out signals proportional to the magnitude of the mismatch with respect to the center of the television raster. These mismatch signals are sent to the guidance and stabilization unit, which seeks to combine the position of the image of the object (line of sight) with the optical axis of the optical-electronic direction finder device. Even with a relatively small open loop coefficient K _times = 25-30 1 / s ^{2, the} initial mismatch leads to an unacceptable speed of the image of the object relative to the photodetector. Due to image blurring and loss of contrast, auto-tracking may fail (see [1] p.137, 138). A similar effect can occur even when using relatively inertialess receivers, if interframe signal accumulation in the direction finder is used. As a result, to ensure a stable transition to auto tracking, at least an excess signal / noise ratio from the image of the object is required, which, in addition to the above disadvantages, also leads to a decrease in the range at which the transition to auto tracking is possible.

 The objective of the invention is to increase the likelihood of switching to auto tracking, increasing the maximum range of a possible transition to auto tracking and improving the accuracy of tracking objects with a tracking optical-electronic system.

 To achieve this task, a servo-connected coordinate converter from a measuring system of a direction finder to a stabilized coordinate system, a smooth error input circuit, a correction device, a stabilized coordinate converter and an actuator are introduced into the optoelectronic system containing the serially connected guidance and stabilization unit and the optoelectronic direction finder. coordinate system of the guidance and stabilization unit. In this case, the input of the coordinate converter from the measuring system of the direction finder to the stabilized coordinate system is connected to the output of the optoelectronic direction finder, and the output of the stabilized coordinate converter to the executive coordinate system of the guidance and stabilization unit is connected to the input of the guidance and stabilization unit.

 In FIG. 1 shows a functional diagram for one channel of the proposed tracking optical-electronic system. Figure 2 shows a possible implementation of the smooth error input scheme (keys are in the position for auto tracking). Functional diagram of a possible implementation of the corrective device shown in figure 3.

 The tracking optical-electronic system consists of a series-connected optical-electronic direction finder 1, a coordinate transducer from the measuring system of the direction finder to a stabilized coordinate system (PK1) 2, a smooth error input circuit (CVT) 3, a correction device (KU) 4, a stabilized coordinate converter executive coordinate system of the guidance and stabilization unit (PK2) 5, guidance and stabilization unit (BNS) 6, the output of which is kinematically connected to the direction finder.

 All used components of the tracking system are known or can be obtained from known devices by combining them by known methods.

 The optical-electronic direction finder can be performed as described in the prototype or [1] (an optical-electronic device, in particular a television camera, and a television machine in the aggregate are a direction finder). The guidance and stabilization unit can be implemented as in the prototype based on pneumatic, hydraulic, electrical [4], including based on two- and three-coordinate torque motors, etc. servos. The application and construction of coordinate transformers are described in detail in [5]. A correcting device with known requirements for the tracking circuit can be formed according to the rules set forth in [6], with the implementation of the hardware based on the methods given in [7]. A smooth error input circuit can be implemented on the basis of switches, storage devices, summing amplifiers, and below we will describe how this can be done.

 The work of the tracking optical-electronic system (SOES) is as follows. Data on target designation (preferably at the input of KU 4, since this provides more convenient memorization of the initial conditions when switching to auto tracking) comes from the complex, which includes the SOES. The guidance and stabilization unit 6 processes target designation signals in the vertical and horizontal planes, combining the image with the optical axis of the direction finder sighting with some angular mismatch, but such that the image of the object is within the part of the field of view (strobe) in which the video signal is analyzed. Direction finder 1 determines the signal of the mismatch in the position of the image of the object relative to the center of the strobe δβ, δε, the coordinates of which are formed in the driver of the television automaton (see [1]). If there is an image of the object in the gated portion of the field of view by the direction finder, the sign of “readiness” is formed, after which the contour of the direction finding television machine processes the measured mismatch, combining the center of the strobe with the image of the object. With this centering of the strobe relative to the image at the output of the resolver of the television automaton, the error signal is canceled (after which the image of the reference is stored), and at the output of the television automaton electrical signals β, ε are generated, which are proportional to the position of the center of the strobe relative to the optical axis of the camera, and a sign of transition to auto tracking ( AC). Signs of readiness and auto-tracking are used to control ATMS 3.

где ε_c, β_c - сигналы рассогласования в стабилизированной системе координат;
γ - угол скрутки измерительной системы координат (см. [5] с.138).In the prototype in automatic mode, these signals are sent directly to the input of the guidance and stabilization unit 6, which leads to unacceptable transients and a very likely breakdown of auto tracking, including due to the fact that stabilization of the position of the line of sight is not provided. Therefore, the coordinates from the direction finder 1 initially enter the coordinate converter from the measuring system of the direction finder to the stabilized coordinate system 2. Its operation can be, in particular, described by the system of equations

where ε _c , β _c are the mismatch signals in a stabilized coordinate system;
γ is the twist angle of the measuring coordinate system (see [5] p. 138).

 As a result of the transformation of coordinates into a stabilized system, it is possible to take into account the rolling of the carrier. It should be noted that for the operation of coordinate converters, it is necessary to measure the qualities of the medium, but since this is obvious, the corresponding blocks and their relationships with the converters are not specifically considered. However, taking into account the qualities, although it allows to reduce the mismatch between the line of sight and the optical axis, does not eliminate all possible reasons for their initial mismatch. And as already indicated, such a mismatch leads to a transitional mode, during which the breakdown of auto tracking is possible.

 Thus, in order to avoid disruption, it is necessary to reduce the speed of movement of the image relative to the photodetector in transition mode. This task is performed by the smooth input circuit of error 3. It performs the following operations. During the centering period of the strobe (from the moment of receipt of the sign of readiness for AC), the inputs of the smoothing 10 and the storage device 7 (see figure 2) are connected to the output of PC1. At the output of the storage device 7, a signal is generated proportional to the position of the center of the strobe relative to the optical axis of the direction finder 1 in the stabilized coordinate system, which is input to the adder 9. Due to the fact that the storage device has some inertia, the equivalent input to the adder 9 through the smoothing device 10 the signal from the output of PC1, having the opposite sign with respect to the output signal of the storage device 7. Therefore, when centering the strobe, the output signal with the ummator 9 is equal to zero and the guidance and stabilization unit 6 moves the optical axis of the direction finder 1 at a speed remembered at the beginning of auto-capture. After the centering is completed (AC sign is received or the time assigned for centering has passed), the switch 8 disconnects the input of the storage device 7 from PC1 (i.e., the switch does not work at the time of autocapture, but only after the centering and storing of the reference are completed) and transfers the storage device 7 to mode of slow resetting of the output signal to zero (such a function is possible when using, for example, a sampling-storage device with the corresponding discharge rate in the storage mode or a reversible counter). At the same time, at the output of the adder 9, the signal gradually increases to a value equal to the output signal of the television automaton. As a result, it is possible to switch to automatic mode of operation at almost any initial mismatch of the target image relative to the center of the raster (within the field of view), including the presence of a centering algorithm relative to the strobe.

причем Т₁ > Т₂.As a rule, high precision tracking by an optoelectronic automatic system is provided only in the central part (10-15%) of the field of view. With a large deviation of the target image from the center of the raster, the nonlinear distortions of the optical system, the nonlinearity of the characteristics of the sensitive element of the television camera, and the nonlinearity of the raster begin to significantly influence the accuracy of determining the coordinates. Therefore, to reduce the standard deviation of the error in determining the coordinates of the object, it is advisable that the image is kept as long as possible in the central part of the raster, i.e. so that the speed of combining the image of the object with the center of the raster is maximum. But for the above reasons, when the image of the object is relatively moving relative to the photodetector, image blur occurs, which manifests itself in a loss of image contrast and blurring. (For the VIDICON LI-479, for example, the maximum speed of moving the image of a point object should not exceed 2 mm / s). That is, the speed of combining the image of the object with the center of the raster should be selected from the condition of non-disruption of auto tracking in the presence of a blur effect. On the other hand, even if tracking is performed without disruption, but due to the high quality factor in the contour, the rate of change of the position of the line of sight relative to the center of the raster is high, an exact determination of the coordinates of the object is impossible, because due to blurring, its image differs from the reference one and the direction finder does not determine the coordinate of the object, but the coordinate of the image most similar to the originally recorded reference image of the object. Therefore, when accompanying the image of the object in the central part of the raster, it is necessary to ensure that the movement of the line of sight relative to the center of the raster is not accompanied by distortion of the image due to blurring. The fulfillment of both of these conditions is ensured by the corrective device 4. A signal is received at its input from the output of the smooth input circuit of error 3 and passes through two parallel branches first. In one of the branches a differentiating filter (DF) 13 is installed, for example, with a transfer function

where T ₁ > T ₂ .

причем Т₃ < Т₁.In another branch there are sequentially mounted unit 11 with a dead band (BNch) 11 and an integro-differentiating filter (IDF) 12, for example, with a transfer function

and T ₃ <T ₁ .

в противном случае W_НКБ=W_ДФ, т.е. обеспечивается более высокая добротность при больших рассогласованиях между линией визирования и оптической осью, чем при малых. Благодаря реализации переключения структуры с использованием зоны нечувствительности, обеспечивается изменение сигнала на выходе сумматора 14 без скачка в момент переключения.The outputs of the differentiating 13 and integro-differentiating filters 12 are connected respectively to the first and second input of the adder 14. Thus, if the object is followed by a mismatch from the center of the raster exceeding the dead band, the equivalent transfer function from the input of KU 4 to the output of its adder 14 takes the form

otherwise, W _NKB = W _DF , i.e. higher quality factor is ensured for large discrepancies between the line of sight and the optical axis than for small ones. Due to the implementation of the switching of the structure using the deadband, the signal at the output of the adder 14 is changed without a jump at the time of switching.

 In order to reduce the static and speed component of the error, it is advisable to follow the loop of the tracking system with astatism. For this, a correcting device uses a series-connected isodromic filter (ISF) 15, with an input connected to the output of the adder 14, and an integrator (In) 16, the output of which is also the output of KU 4. Using a second-order astatism circuit also simplifies the solution of the motion problem with at a constant speed during the time when auto-capture is carried out, since at zero output signal from the FSS, movement will be carried out at a speed corresponding to the output signal from the isodromic filter 15 ( Y) 4, but in steady state, zero input signal at a constant value corresponds to the integral action at the outlet.

где ε_н q_н - углы наведения БНС в исполнительной системе координат;
ε_cc, β_cc - углы наведения БНС в стабилизированной системе координат;
α, ψ, θ - углы соответственно курса, тангажа и крена носителя.From the output of the correcting device 4, the signal is fed to the input of the stabilized coordinate converter into the executive coordinate system of the guidance and stabilization unit (PC2) 5. PC2 can, in particular, be described by the dependencies

where ε _n q _n are the angles of guidance of the BNS in the executive coordinate system;
ε _cc , β _cc — BNS pointing angles in a stabilized coordinate system;
α, ψ, θ - angles of the course, pitch and roll of the carrier, respectively.

 Under the action of the control signal from the output of PC2, the guidance and stabilization unit 6 deploys the optical axis of the direction finder in the direction of the object. This provides support for moving and stationary objects from a swinging base.

 Thus, increasing the probability of switching to auto tracking, increasing the maximum range of a possible transition to auto tracking and improving tracking accuracy is ensured by introducing a first coordinate converter, a smooth error input circuit, and a correction device into the servo optical-electronic system between the direction finder and the guidance and stabilization unit and a second coordinate transformer. Additional quality improvement is achieved by introducing a delay when the storage device is disconnected from the output of the first coordinate transformer, using non-linear correction and second-order astatism in a closed loop.

SOURCES OF INFORMATION
1. Barsukov F.I., Velichkin A.I., Sukharev A.D. Television systems of aircraft. - M .: Soviet Radio, 1979, p. 232, Fig. 7.17 - analogue.

 2. Maximov M.V., Gorgonov G.I. Electronic homing systems. - M .: Radio and communication, 1982, p.110-112, 228-230 - analogue.

 3. Gryazin G. N. Optoelectronic systems for the review of space: Television systems. - L.: Engineering, Leningrad Department, 1988, p. 8 and 9, Fig. 4 - prototype.

 4. Chilikin M.G., Sandler A.S. General course of electric drive. - M.: Energoizdat, 1981.

 5. Rivkin S.S. Stabilization of measuring devices on a swinging base. - M.: Science, 1978.

 6. Besekersky V. A., Popov EP Theory of automatic control systems. - M .: Nauka, 1973.

 7. Tetelbaum II, Schneider Yu.R. 400 schemes for AVM. - M .: Energy, 1978.

Claims (4)

 1. Tracking optoelectronic system containing a serially connected guidance and stabilization unit and an optoelectronic direction finder, characterized in that it includes a serially connected coordinate converter from the measuring system of the direction finder to a stabilized coordinate system, a smooth error input circuit, a corrective device, converter of stabilized coordinates to the executive coordinate system of the guidance and stabilization unit, and the input of the coordinate converter from the measuring of the direction finder system to the stabilized coordinate system is connected to the output of the optoelectronic direction finder, and the output of the stabilized coordinate converter to the executive coordinate system of the guidance and stabilization unit is connected to the input of the guidance and stabilization unit.  2. The optical-electronic tracking system according to claim 1, characterized in that the smooth error input circuit consists of a switch, a storage device, and a smoothing device and an adder connected in series, the input of the smoothing device being connected to the output of the coordinate transformer from the measuring system of the direction finder to the stabilized system coordinates, the input of the storage device is connected via a switch to the output of the coordinate converter from the measuring system of the direction finder to a stabilized coordinate system inat, the output of the storage device is connected via a switch to the second input of the adder, and the output of the adder is connected to the input of the correction device.  3. The optical-electronic tracking system according to claim 1, characterized in that the corrective device consists of a differentiating filter, a series-connected unit with a dead zone, an integro-differentiating filter and an adder, a series-connected isodromic filter and an integrator, and the output of the smooth error input circuit is connected to unit inputs with a dead zone and a differentiating filter, the output of the differentiating filter is connected to the second input of the adder, the output connected to the input of the isodrom th filter, and the output of the integrator is connected to the input of inverter stabilized coordinates to coordinate actuation system aiming and stabilization unit.  4. The tracking optoelectronic system according to claim 2, characterized in that the switch is configured to disconnect the storage device from the output of the coordinate transformer from the measuring system of the direction finder to a stabilized coordinate system with a delay equal to the centering and storing time of the reference image.

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