KR102128548B1 - Line of sight stabilization system with canceling disturbance - Google Patents

Abstract

The present invention relates to a gaze stabilization system for controlling an object to stably follow a target gaze by canceling the disturbance applied to the object.
The gaze stabilization system according to an embodiment of the present invention includes a gimbal driven in the first and second axes, an angular velocity sensor for measuring the gaze angular velocity of the object, and a servo outputting a signal for controlling the gimbal Includes a controller. At this time, the angular velocity disturbance includes a disturbance flowing into the third axis rather than the driving axis of the gimbal.
In the present invention, since the angular velocity disturbance is analytically calculated and a servo controller for canceling it is configured, it is possible to completely remove the angular velocity disturbance and the camera module can stably shoot an image.

Description

Line of sight stabilization system with canceling disturbance}

The present invention relates to a system for controlling an object to stably follow a target gaze by canceling the disturbance applied to the object.

For long-distance observation, the camera system is mounted on an aircraft and operated. The camera system consists of a camera module that incorporates an image sensor and an optical system, a stabilizing driver consisting of a gimbal and a servo controller to support the camera module and move the camera's gaze in a desired direction, and a system controller that combines them. The stabilized driver consists of a gimbal as a machine frame, a gyro for sensing the angular velocity of the inertial plane, a servo controller generating a drive signal, and a servo amplifier and servo motor.

The camera system is mounted on an aircraft flying at a high altitude to secure a long-range field of view for long-distance observation, and uses a high magnification optical system in the camera module to enlarge a small target at a long distance. Since the optical system of high magnification reacts sensitively to the shaking of the camera, the shaking of the image occurs due to vibration introduced from the outside, so to prevent this, the camera module is supported by a stabilizing driver including gimbal.

Vibration from the outside includes not only aircraft vibration but also vibration due to wind pressure, explosion, and the like. Vibration from the outside may be transmitted to the camera module with angular oscillation disturbance, which causes angular displacement in the camera module. Since the quality of the image may be deteriorated due to such disturbance, a stabilization system capable of completely removing the disturbance is required.

[1] J.M. Hikert, “Inertially Stabilized Platform Technology”, IEEE Control Systems Magazine, pp26-46, Feb. 2008 [2] Seongsu Kim et al., “Analysis of image stabilization impact of aircraft pitch fluctuation,” 2017 Conference Papers, pp247-248, Korean Military Science and Technology Society, 2017.6 [3] Richard L. Pio, “Symbolic Representation of Coordinate Transformations”, IEEE Tractions on Aerospace and Navigational Electronics, Vol. ANE-11, June, 1964, pp128-134 [4] BERTIL EKSTRAND, “Equations of Motion for a Two-Axes Gimbal System,” IEEE TRANSACTIONS ON AEROSPACE AND ELECTRONIC SYSTEMS VOL. 37, NO. 3 JULY 2001 [5] Xia Yun-xia et al, 2-Port Internal Model Control for Gyro Stabilized Platform of Electro-Optical Tracking System, “Acquisition, Tracking, Pointing, and Laser Systems Technologies XXVI, Proc. of SPIE Vol. 8395, 83950M, 2012

The problem to be solved by the present invention is to provide a system capable of stabilizing the gaze of an object from angular velocity disturbances that cause unwanted angular displacement in the object. The angular velocity disturbance includes a disturbance flowing along an axis other than the drive shaft of the gimbal, and the present invention is to provide a gaze stabilization system capable of completely removing even the angular velocity disturbance.

Another problem to be solved by the present invention is to provide a method for analytically calculating the angular velocity disturbance. Furthermore, the present invention is to provide a gaze stabilization system capable of completely removing the angular velocity disturbance by configuring a controller to cancel the analyzed angular velocity disturbance.

The problems of the present invention are not limited to the problems mentioned above, and other problems not mentioned will be clearly understood by those skilled in the art from the following description.

As a means for solving the above-described technical problem, the gaze stabilization system of an object according to an embodiment includes a gimbal driven in a first axis and a second axis; An angular velocity sensor for measuring the gaze angular velocity of the object; And a servo controller outputting a signal for controlling the gimbal, wherein the servo controller is configured to follow the gaze targeted by the object according to a command input and a feedback input of the angular velocity of the gaze of the object. A follower controller for outputting a follower control signal for controlling the; And a disturbance controller that outputs a disturbance control signal for controlling the gimbal so as to cancel the angular velocity disturbance applied to the object, and the angular velocity disturbance is a disturbance flowing into the third axis rather than the driving axis of the gimbal.

In the gaze stabilization system according to an embodiment, the disturbance controller receives the gaze angular velocity of the measured object and outputs the disturbance control signal to cancel the angular velocity disturbance.

In the gaze stabilization system according to an embodiment, the disturbance controller is designed to cancel the angular velocity disturbance calculated analytically.

In the gaze stabilization system according to an embodiment, the angular velocity disturbance is calculated by the following equation,

(Mathematics)

wR1z = wLOSz*cosΘ-wLOSx*sinΘ

The wR1z is the angular velocity disturbance, the wLOSz is the gaze angular velocity of the object with respect to the third axis of the gaze coordinate system, the wLOSx is the gaze angular velocity of the object with respect to the first axis of the gaze coordinate system, and the Θ is the It represents the driving angle of the gimbal with respect to the second axis.

In the gaze stabilization system according to an embodiment, the tracking control signal and the disturbance control signal are signals that control the angular velocity at which the gimbal rotates about the first axis.

In the gaze stabilization system according to an embodiment, the disturbance control signal output from the disturbance controller is input to the following controller.

In the gaze stabilization system according to an embodiment, the tracking controller and the disturbance controller are configured independently.

In the gaze stabilization system according to an embodiment, the disturbance control signal output from the disturbance controller is summed with the tracking control signal output from the following controller.

In the gaze stabilization system according to an embodiment, the gaze angular velocity of the object is directly measured by the angular velocity sensor, or is indirectly measured by calculating coordinates of other measured angular velocity to calculate the gaze angular velocity of the object.

In the gaze stabilization system according to an embodiment, the angular velocity sensor may include a 1-axis sensor capable of sensing angular velocity on 1 axis, a 2-axis sensor capable of sensing angular velocity on 2 axes, or a 3-axis capable of sensing angular velocity on 3 axes. It consists of sensors.

The gaze stabilization system according to an embodiment further includes at least one external gimbal mounted on the outside of the gimbal and having one or more degrees of freedom.

In the gaze stabilization system according to an embodiment, the first axis and the second axis are azimuth axis and elevation axis, and the third axis is a roll axis (horizontal axis).

In the gaze stabilization system according to an embodiment, the first axis, the second axis, and the third axis are composed of a roll axis, a pitch axis, and a yaw axis.

The gaze stabilization system according to an embodiment is mounted on an aircraft together with the object.

In the gaze stabilization system according to an embodiment, the object is a camera module.

As a means for solving the above-described technical problem, a method for stabilizing a gaze of an object using gimbals driven in a first axis and a second axis, the method comprising: measuring a gaze angular velocity of the object; Outputting a tracking control signal controlling the gimbal so that the object follows a target gaze according to a command input and a feedback input of the angular velocity of the gaze of the object; And outputting a disturbance control signal for controlling the gimbal to cancel the angular velocity disturbance applied to the object, wherein the angular velocity disturbance is a disturbance flowing into the third axis rather than the driving axis of the gimbal.

In the gaze stabilization method according to an embodiment, the step of outputting the disturbance control signal includes: calculating the angular velocity disturbance from the gaze angular velocity of the measured object; And configuring the disturbance control signal to cancel the calculated angular velocity disturbance.

In the gaze stabilization method according to an embodiment, the angular velocity disturbance is calculated by the following equation,

(Mathematics)

wR1z = wLOSz*cosΘ-wLOSx*sinΘ

The wR1z is the angular velocity disturbance, the wLOSz is the gaze angular velocity of the object with respect to the third axis of the gaze coordinate system, the wLOSx is the gaze angular velocity of the object with respect to the first axis of the gaze coordinate system, and the Θ is the first It represents the driving angle of the gimbal with respect to the two axes.

As a means for solving the above-described technical problem, the gaze stabilization method is recorded on a recording medium in which a program for execution on a computer is recorded.

In the present invention, an angular velocity disturbance flowing into an axis other than the drive axis of the gimbal is analytically calculated, and a servo controller for canceling it is constructed. That is, in the present invention, since the angular velocity disturbance is analytically calculated, it is possible to completely remove the angular velocity disturbance by outputting a control signal for canceling it. Therefore, it is possible for the camera module to stably shoot an image.

In addition, in the present invention, the tracking controller for tracking the eye and the disturbance controller for removing the disturbance are configured independently. Therefore, the design of the tracking controller does not become complicated or the performance of the tracking controller does not deteriorate due to the addition of the disturbance controller.

The effect according to the present invention is not limited by the contents exemplified above, and more various effects are included in the present specification.

1 shows a gaze stabilization system according to an embodiment.
2 shows the aircraft's body frame.
FIG. 3 shows a body frame, an internal and external coordinate system of gimbal, and a LOS frame of a camera module.
4 to 7 illustrate a process in which angular velocity disturbance flows into the camera module.
8 is a block diagram showing a control structure for following a target line of sight for a roll axis.
9 and 10 are block diagrams showing a control structure of a gaze stabilization system according to an embodiment.
11 shows a gimbal coordinate system in a gaze stabilization system according to another embodiment.
12 is a view illustrating a process in which angular velocity disturbance is introduced into a camera module in a gaze stabilization system according to another embodiment.
13 is a block diagram showing a control structure for following a target line of sight with respect to an azimuth axis.
14 and 15 are block diagrams showing a control structure of a gaze stabilization system according to another embodiment.
16 and 17 are flowcharts illustrating a method for stabilizing the gaze.

Hereinafter, exemplary embodiments will be described in detail with reference to the accompanying drawings. It goes without saying that the following description is only for the purpose of embodying the embodiments and does not limit or limit the scope of the invention. From the detailed description and examples, what can be easily inferred by experts in the art is interpreted as belonging to the scope of rights.

As used herein, terms such as'consist of' or'comprises' should not be construed as including all of the various components or various steps described in the specification, and some components or some of them. It should be construed that they may not be included, or may further include additional components or steps.

The terms used in the present specification have selected general terms that are currently widely used as possible while considering functions in the present invention, but this may be changed according to intentions or precedents of a person skilled in the art or the appearance of new technologies. In addition, in certain cases, some terms are arbitrarily selected by the applicant, and in this case, their meanings will be described in detail in the description of the applicable invention. Therefore, the term used in the present invention should be defined based on the meaning of the term and the entire contents of the present invention, not a simple term name.

1 shows a gaze stabilization system according to an embodiment. The gaze stabilization system 100 according to an embodiment includes a gimbal 110, an angular velocity sensor 120, a servo controller 130, a servo amplifier (not shown), and a servo motor (not shown).

In one embodiment, the object to which the gaze stabilization system 100 is applied is a camera module. In one embodiment, the camera module is mounted on the gimbal 110 and mounted on the back of the aircraft to shoot directly and sideways of the aircraft.

The camera module may be an electro optical infra-red (EO/IR) camera module in which a high magnification optical system capable of enlarging and capturing a small target over a long distance is used. The camera module mounted on the rear of the aircraft can be used for long range oblique photography (LOROP).

Alternatively, the camera module may be various types of camera modules such as a charge-coupled device camera (CCD) camera module, a zoom type camera module, a dome type camera module, a PTZ (pan-tilt-zoom) camera module, and a fisheye camera module. Is not limited to.

In this way, specifying the target of the gaze stabilization system 100 as a camera module is for convenience of description and does not limit the target. The gaze stabilization system 100 is applicable to any object that requires gaze stabilization, such as a satellite antenna or a space telescope.

In addition, specifying that the camera module is mounted on the aircraft is only for convenience of description, and even when the camera module is mounted on another fuselage or a fixed body, the gaze stabilization system 100 can be applied.

The gaze stabilization system 100 is a system for stabilizing the line of sight (LOS) of the camera module from angular velocity disturbance. Vibration may be introduced into the camera module due to various factors from the outside. For example, vibration may be generated by the resonance mode of the gimbal itself, or by the rotation mode generated by the anti-vibration hole in the gimbal. Among these vibrations, the angular velocity disturbance that causes angular displacement in the camera module affects the gaze of the camera module. In the case of linear vibration, it can also be converted into angular velocity disturbance in the process of being transmitted to gimbal. The gaze stabilization system 100 compensates for this angular velocity disturbance, so that the camera module can acquire a stable image.

The gimbal 110 is composed of an internal gimbal where the camera module is mounted and an external gimbal to protect the camera module from the external environment. The external gimbal may be configured to be integral with a shroud to protect the camera module from the external environment.

The inner gimbal consists of two drive shafts, and the outer gimbal consists of one drive shaft. The internal gimbal can be driven by the roll axis and the pitch axis, but not by the yaw axis. In addition, the external gimbal can be driven by a roll shaft.

As such, specifying the structure of the gimbal 110 is also for convenience of explanation, and does not limit the structure of the gimbal 110. Hereinafter, in this specification, a method of analyzing the angular velocity disturbance and designing a controller based on the specified structure of the gimbal 110 will be described. Although it will be described later in the present specification, the present invention can be applied to gimbals of other structures, and the structure of the gimbal 110 specified according to an embodiment is only one of applicable structures.

The angular velocity sensor 120 is a sensor for measuring the gaze angular velocity of the camera module. The angular velocity sensor 120 is mounted on the camera module to directly measure the gaze angular velocity. Alternatively, the angular velocity sensor 120 may be configured to indirectly measure the angular velocity of the camera module by measuring the angular velocity of the fuselage and converting coordinates to calculate the gaze angular velocity.

The angular velocity sensor 120 is a sensor that measures angular velocity with respect to an inertia frame, and may be configured with an inertial sensor such as a gyro sensor.

In addition, the angular velocity sensor 120 may be configured as a 3-axis sensor capable of sensing angular velocity with respect to 3 axes. Alternatively, the angular velocity sensor 120 may be composed of three single-axis sensors capable of sensing angular velocity about one axis, or may be composed of a two-axis sensor capable of sensing angular velocity about two axes and a single axis sensor.

The servo controller 130 outputs a signal that controls the gimbal 110 so that a stable image can be obtained while following the target gaze of the camera module.

The servo controller 130 receives a command from a user, and a tracking controller 131 outputting a tracking control signal to follow a target line of sight of the camera module, and a disturbance controller 132 outputting a disturbance control signal for canceling the angular velocity disturbance. It includes.

The tracking control signal and the disturbance control signal output from the servo controller 130 are amplified by the servo amplifier and input to the servo motor.

The configuration of the gaze stabilization system 100 according to one embodiment has been described above. Based on the configuration of the gaze stabilization system 100 described above, the following describes a process in which the angular velocity disturbance flows into the camera module, and a method of calculating the angular velocity disturbance from the gaze angular velocity of the object will be described. In addition, a control method for stabilizing the gaze of the camera module using the calculated angular velocity disturbance will be described.

First, an aspect in which the angular velocity disturbance is transmitted to the camera module will be described with reference to FIGS. 2 to 7.

2 shows the aircraft's body frame. FIG. 3 shows a body frame, an internal and external coordinate system of gimbal, and a LOS frame of a camera module. 4 to 7 illustrate a process in which angular velocity disturbance flows into the camera module.

2 to 7, B0f represents the aircraft's body frame. The aircraft coordinate system is a coordinate system fixed to the aircraft, B0x represents a roll axis of the aircraft coordinate system B0f, B0y represents a pitch axis, and B0z represents a yaw axis. wB0x, wB0y, and wB0z indicate the angular velocity of the roll axis B0x, the pitch axis B0y, and the yaw axis B0z, respectively.

In addition, R0f is an external coordinate system that is a fixed coordinate system to the external gimbal, R0x is a roll axis of the external coordinate system (R0f), R0y is a pitch axis, and R0z is a yaw axis. wR0x, wR0y, and wR0z indicate the angular velocity of the roll axis R0x, the pitch axis R0y, and the yaw axis R0z, respectively.

In addition, R1f is an internal coordinate system that is a fixed coordinate system in the internal gimbal, R1x is a roll axis of the internal coordinate system R1f, R1y is a pitch axis, and R1z is a yaw axis. wR1x, wR1y, and wR1z indicate the angular velocity of the roll axis R1x, the pitch axis R1y, and the yaw axis R1z, respectively.

In addition, LOSf is the LOS frame of the camera module, LOSx is the roll axis of the LOSf, LOSy is the pitch axis, and LOSz is the yaw axis. wLOSx, wLOSy, and wLOSz indicate the angular velocity of the roll axis (LOSx), the pitch axis (LOSy), and the yaw axis (LOSz), respectively.

In the description with reference to FIG. 1, the outer gimbal has a roll axis R0x as a drive shaft, and the inner gimbal has a roll axis R1x and a pitch axis R1y as a drive shaft. φ0 indicates the roll angle of the outer gimbal, φ1 indicates the roll angle of the inner gimbal, and Θ1 indicates the pitch angle of the inner gimbal.

In one embodiment, the roll angle and pitch angle of the gimbal may be configured to have a driving range of -85°<φ0<+85°, -5°<φ1<+5°, -15°<Θ1<15°, respectively.

The center of rotation of the gimbal is the center of the camera module, but in FIGS. 3 to 6, for convenience of explanation, the coordinate system is displayed on the part where the motor is located.

In FIG. 4, B0x and R0x are on the same axis of rotation, for example, the same as the combination of a rotor and a stator of a motor. If it is mechanically fixed without rotating freedom, wB0x = wR0x.

In consideration of the arrangement and shape of the gimbal, an angular velocity combination vector diagram between each coordinate system may be represented as in FIGS. 4 to 6. From FIG. 4 to FIG. 6, an aspect in which the angular velocity of the aircraft fuselage is combined with the gaze of the camera module through the external coordinate system R0f and the internal coordinate system R1f can be obtained as in the following Equations 1.a to 1.f. have.

Equation 1.a and Equation 1.b show that the angular velocity of the gas coordinate system B0f is coupled to the external coordinate system R0f, as shown in FIG. 4.

(Equation 1.a)

wR0z = wB0z*cos(φ0)-wB0y*sin(φ0)

(Equation 1.b)

wR0y = wB0y*cos(φ0) + wB0z*sin(φ0)

Equation 1.c and Equation 1.d indicate that the angular velocity of the external coordinate system R0f is coupled to the internal coordinate system R1f, as shown in FIG. 5.

(Equation 1.c)

wR1z = wR0z*cos(φ1)-wR0y*sin(φ1)

(Equation 1.d)

wR1y = wR0y*cos(φ1) + wR0z*sin(φ1)

Equation 1.e and Equation 1.f indicate that the angular velocity of the internal coordinate system R1f is coupled to the gaze coordinate system LOSf, as shown in FIG. 6.

(Equation 1.e)

wLOSx = wR1x*cosΘ-wR1z*sinΘ

(Equation 1.f)

wLOSz = wR1z*cosΘ + wR1x*sinΘ

When the above equations 1.a to 1.f are expressed as drawings, it becomes FIG. 7. In FIG. 7, the prefix w for expressing angular velocity is omitted. In FIG. 7, Cφ0 represents cos(φ0), Sφ0 represents sin(φ0), Cφ1 represents cos(φ1), Sφ1 represents sin(φ1), CΘ represents cosΘ, and SΘ represents sinΘ.

In Equations 1.a to 1.f, frictional coupling between the rotor and the stator of the servomotor was neglected, which is actually negligible.

The outputs of the servomotors for the three drive shafts of Gimbal are expressed by the angular velocity of the corresponding axes, that is, wR0x, wR1x, and wLOSy. In addition, the angular velocity wLOSx, wLOSy, and wLOSz of the gaze coordinate system are sensed by the angular velocity sensor attached to the camera module.

The drive shaft of the inner gimbal for stabilizing the gaze of the camera module is a roll axis and a pitch axis. In the case of the pitch axis, since the servo motor can directly control wLOSy, the incoming angular velocity disturbance is blocked by the rotational freedom of the servo motor.

On the other hand, referring to Equation 1.e, in the roll axis, the output wR1x of the servo motor is transmitted to wLOSx through cosΘ, and wR1z also flows -sinΘ. The servo motor can directly control wR1x, but cannot control wR1z directly because R1z is not the drive shaft of Kimber. Therefore, wR1z acts as an angular velocity disturbance that causes an undesired angular displacement in the gaze of the camera module.

8 is a block diagram showing a control structure for following a target line of sight for a roll axis. In FIG. 8, the servo controller is composed of only a follower controller Gc(s) without a disturbance controller.

The servo amplifier and servo motor are operated in the current driving type, and the transfer function at this time can be simplified to the torque constant Kt. In addition, the unevenness of mass within the gimbal and the coupling due to mutual motion between the axes are input as a torque disturbance expressed by Tqr_dstb in FIG. 8. The block diagram output, wLOSx, is the angular velocity of the roll axis and is sensed from the angular velocity sensor mounted on the camera module.

In order to stabilize the gaze, wLOSx must be operated so that even if an angular velocity disturbance enters the camera. However, while wR1x can be controlled by the command input (wc) of the servo controller, wR1z is not easy to remove because it is input from a different direction from the roll axis. In addition, since the bonding amount is -sinΘ, the stabilization performance of the image decreases as the pitch angle Θ increases. To avoid this, the pitch angle Θ may be fixed to 0, but this causes a problem of limiting the driving angle, resulting in limitation of the shooting angle.

The block diagram shown in FIG. 8 is expressed by Equation 2 below.

(Equation 2)

Command input (wc) is implemented in wLOSx within the bandwidth. Also, the torque disturbances (Tqr_dstb, T_d(s)) can be attenuated relatively easily by the controller according to the characteristics of the open loop transfer function as shown in Equation (2).

However, in the case of wR1z, even if Gopen(s) converges to 0 at a high frequency, the effect is not 0 and remains at wLOSx by -sinΘ. As a result, the image is shaken and the quality of the image is deteriorated.

Since the drive shaft of the inner gimbal is a roll axis and a pitch axis, it is not possible to directly control wR1z, which is an angular velocity disturbance caused by a yaw axis, rather than a drive axis. Therefore, a method for removing wR1z is required to stabilize the gaze of the camera module.

To this end, the present invention proposes a method for analytically calculating the yaw axis angular velocity wR1z.

Multiplying sinΘ and cosΘ by Equation 1.e and Equation 1.f for outputting the angular velocity of the roll axis and the angular velocity of the yaw axis of the gaze coordinate system are Equation 3.a and Equation 3.b.

(Equation 3.a)

wLOSz*cosΘ = wR1zcos ² Θ + wR1x*sinΘ*cosΘ

(Equation 3.b)

wLOSx*sinΘ = wR1x*cosΘ*sinΘ-wR1z*sin ² Θ

Subtracting Equation 3.b from Equation 3.a results in Equation 4 below.

(Equation 4)

wLOSz*cosΘ-wLOSx*sinΘ = wR1z

As shown in Equation 4, the angular velocity disturbance wR1z can be calculated from wLOSx and wLOSz. That is, the angular velocity disturbance wR1z may be calculated from the outputs of the angular velocity sensor sensing the angular velocity of the camera module (wLOSx, wLOSz).

Next, a method of generating a disturbance control signal for removing angular velocity disturbance wR1z using Equation 4 and block diagram 8 will be described.

The following equation (5) is obtained from the block diagram of FIG.

(Equation 5)

wLOSx = -wR1z*sinΘ + Gr(s)*cosΘ*(wc-wLOSx)

⇔ wLOSx*(1 + Gr(s)*cosΘ) = -wR1z*sinΘ + Gr(s)*cosΘ*wc

Here, Gr(s) = Gc(s)*Kt/(Js).

In Equation 5, the disturbance control signal wR1z*sinΘ/(Gr(s)*cosΘ) is added to the command input wc to remove wR1z*sinΘ to obtain Equation 6.

(Equation 6)

wLOSx*(1 + Gr(s)*cosΘ)

= -wR1z*sinΘ + Gr(s)*cosΘ*{wc + wR1z*sinΘ/(Gr(s)*cosΘ)}

= Gr(s)*cosΘ*wc

Thus, by calculating the angular velocity disturbance (wR1z) from the output of the angular velocity sensor (wLOSx, wLOSz), and inputting a disturbance control signal for removing it, the angular velocity disturbance (wR1z) is completely removed from the gaze angular velocity (wLOSx) of the camera module. can do.

The block diagram reflecting Equation 6 is shown in FIG. 9. In FIG. 9, the disturbance control signal is generated by the shaded blocks, and the shaded blocks correspond to the disturbance controller for removing the angular velocity disturbance (wR1z).

Alternatively, Equation 6 can be rewritten as Equation 7 below.

(Equation 7)

wLOSx (1 + Gr(s)*cosΘ)

= -wR1z*sinΘ + Gr(s)*cosΘ*wc + Kt/Js*cosΘ*wR1z*sinΘ/(Kt/Js*cosΘ)

= Gr(s)*cosΘ*wc

Summarizing Equation 6 as in Equation 7 is equivalent to changing the input position of the disturbance control signal as shown in FIG. 10 in the block diagram of FIG. 9. The blocks shaded in FIG. 10 correspond to the disturbance controller.

When the servo controller is configured as shown in FIG. 10, the disturbance control signal can be applied to the input terminal of the servo amplifier regardless of the type of the tracking controller Gc(s) for target tracking. That is, there is an advantage that the design of the tracking controller (Gc(s)) to implement the angular velocity command well and the design of the disturbance controller (shaded blocks) to remove the disturbance can be performed independently.

When the disturbance controller is designed as shown in FIGS. 9 and 10, the angular velocity disturbance (wR1z) can be measured and calculated using the output of the angular velocity sensor (wLOSx, wLOSz) without the need for estimation of the disturbance by a state observer. Do. In addition, the shaded blocks of FIGS. 9 and 10 may be added in software without changing the tracking controller Gc(s) for target tracking.

The control method for canceling the angular velocity disturbance flowing into the camera module in the gaze stabilization system according to the embodiment has been described above. In the gaze stabilization system according to an embodiment, the gimbal consists of an external gimbal that can be driven by a roll axis and an internal gimbal that can be driven by a roll/pitch axis. The control method described above can be applied even if the gimbal has a different structure, and for this explanation, a gaze stabilization system equipped with a gimbal using azimuth axis and elevation axis as drive axes will be described. .

11 shows a gimbal coordinate system in a gaze stabilization system according to another embodiment. 12 illustrates a process in which angular velocity disturbance is introduced into the camera module in the gaze stabilization system according to another embodiment. The gaze stabilization system according to another embodiment differs only in the structure of the gaze stabilization system and the gimbal according to the embodiment illustrated in FIG. 1, and descriptions of overlapping parts are omitted.

11 and 12, the B0 frame (B0f) represents the aircraft's body frame. The aircraft coordinate system is a coordinate system fixed to the aircraft, B0x represents a roll axis of the aircraft coordinate system B0f, B0y represents a pitch axis, and B0z represents a yaw axis. wB0x, wB0y, and wB0z indicate the angular velocity of the roll axis B0x, the pitch axis B0y, and the yaw axis B0z, respectively.

In addition, A0 frame (A0f) is a gimbal coordinate system that is a fixed coordinate system in gimbal, A0x is a roll axis of the gimbal coordinate system (A0f), A0y is an elevation axis, and A0z is an azimuth axis. wA0x, wA0y, and wA0z are the angular speeds of the roll axis A0x, the elevation axis A0y, and the azimuth axis A0z, respectively.

In addition, E0 frame (E0f) is the LOS frame of the camera module, E0x is the roll axis of the gaze coordinate system (E0f), E0y is the pitch axis, and E0z is the yaw axis. wLOSx, wLOSy, and wLOSz represent the angular velocity of the roll axis E0x, the pitch axis E0y, and the yaw axis E0z, respectively.

As for the gimbal, the elevation axis (A0y) and the azimuth axis (A0z) are composed of drive shafts. η0 is the azimuth angle of the gimbal, and ε0 is the elevation angle of the gimbal.

The aspect in which the angular velocity of the aircraft fuselage from FIG. 12 is combined with the gaze of the camera module through the gimbal coordinate system (A0f) can be obtained as shown in Equations 8.a to 8.d. In FIG. 12, Cη0 represents cos(η0), Sη0 represents sin(η0), Cε0 represents cos(ε0), and Sε0 represents sin(ε0).

Equations 8.a and 8.b show that the angular velocity of the gas coordinate system B0f is combined into the gimbal coordinate system A0f.

(Equation 8.a)

wA0x = wB0x*cos(η0) + wB0y*sin(η0)

(Equation 8.b)

wA0y = wB0y*cos(η0)-wB0x*sin(η0)

Equation 8.c and Equation 8.d indicate that the angular velocity of the gimbal coordinate system A0f is combined into the gaze coordinate system E0f.

(Equation 8.c)

wLOSx = wA0x*cos(ε0)-wA0z*sin(ε0)

(Equation 8.d)

wLOSz = wA0z*cos(ε0) + wA0x*sin(ε0)

The output of the servomotor for the two drive shafts of Gimbal is expressed by the angular velocity of the corresponding axis, that is, wA0z and wLOSy. In addition, the angular velocity wLOSx, wLOSy, and wLOSz of the gaze coordinate system are sensed by the angular velocity sensor attached to the camera module.

Referring to Equation 8.d, the angular velocity disturbance wA0x due to the roll axis rather than the drive axis flows by sin(ε0). In order to analytically calculate the angular velocity disturbance (wA0x), when Equation 8.c and Equation 8.d are multiplied by cos(ε0) and sin(ε0), respectively, Equation 9.a and Equation 9.b do.

(Equation 9.a)

wLOSx*cos(ε0) = wA0xcos ² (ε0)-wA0z*sin(ε0)*cos(ε0)

(Equation 9.b)

wLOSz*sin(ε0) = wA0z*cos(ε0)*sin(ε0) + wA0x*sin ² (ε0)

When Equation 9.b is added to Equation 9.a, Equation 10 below is derived.

(Equation 10)

wLOSx*cos(ε0) + wLOSz*sin(ε0) = wA0x

As shown in Equation 10, the angular velocity disturbance wA0x can be calculated from wLOSx and wLOSz. That is, the angular velocity disturbance wA0x may be calculated from the outputs of the angular velocity sensors sensing the angular velocity of the camera module (wLOSx, wLOSz).

The gaze stabilization system according to another embodiment differs only in the structure of the gaze stabilization system and the gimbal according to the embodiment illustrated in FIG. 1. Therefore, the control structure of the gaze stabilization system according to another embodiment may be configured as the block diagram of FIG. 13 similarly to FIG. 8, from which the following Equation 11 can be obtained.

(Equation 11)

wLOSz = wA0x*sin(ε0) + Gr(s)*cos(ε0)*(wc-wLOSz)

⇔ wLOSz*(1 + Gr(s)*cos(ε0)) = wA0x*sin(ε0) + Gr(s)*cos(ε0)*wc

Here, Gr(s) = Gc(s)*Kt/(Js).

Equation 12 is obtained by adding a disturbance control signal (-wA0x*sin(ε0)/(Gr(s)*cosΘ)) to the command input wc to remove wA0x*sin(ε0) from Equation (11).

(Equation 12)

wLOSz*(1 + Gr(s)*cos(ε0))

= wA0x*sin(ε0) + Gr(s)*cos(ε0)*{wc -wA0x*sin(ε0)/(Gr(s)*cosΘ)}

= Gr(s)*cos(ε0)*wc

As described above, by calculating the angular velocity disturbance (wA0x) from the outputs of the angular velocity sensor (wLOSx, wLOSz) and adding the disturbance control signal (-wA0x*sin(ε0)/(Gr(s)*cosΘ)) to remove it , The angular velocity disturbance (wA0x) can be completely removed from the gaze angular velocity (wLOSz) of the camera module.

14 is a block diagram reflecting Equation 12. In FIG. 14, the disturbance control signal is generated by the shaded blocks, and the shaded blocks correspond to the disturbance controller.

Alternatively, Equation 12 can be rewritten as Equation 13 below.

(Equation 13)

wLOSz*(1 + Gr(s)*cos(ε0))

= wA0x*sin(ε0) + Gr(s)*cos(ε0)*wc

-Kt/Js*cos(ε0)*wA0x*sin(ε0)/(Kt/Js*cos(ε0))}

= Gr(s)*cos(ε0)*wc

Summarizing Equation 12 as shown in Equation 13 is equivalent to changing the input position of the disturbance control signal as shown in FIG. 15 in the block diagram of FIG. 14. The blocks shaded in FIG. 15 correspond to the disturbance controller.

Thus, the angular velocity disturbance (wA0x) flowing into the azimuth axis (A0z), which is the driving axis of the gimbal, can be calculated using the outputs of the angular velocity sensors (wLOSx, wLOSz), and the angular velocity disturbance (wA0x) can be completely eliminated.

In the case of a 4-axis gimbal composed of an internal 2-axis and an external 2-axis, the angular velocity coupling degree can be configured in a manner in which the angular velocity coupling structure of the 2-axis gimbal is repeated twice. In this case, the part where the final stabilization works is the internal gimbal 2 axis, so the same discussion can be applied.

So far, the configuration of the gaze stabilization system according to the embodiments and the control method for stabilizing the gaze of the camera module from angular velocity disturbances have been described. The method for stabilizing the gaze according to the above discussion is as shown in FIGS. 16 and 17.

16 and 17, when the angular velocity sensor measures the gaze angular velocity of the object (S11), the tracking controller receives the measured gaze angular velocity of the object and outputs a tracking control signal (S12). The disturbance controller outputs a disturbance control signal that can completely cancel the angular velocity disturbance (S13), and the angular velocity disturbance is analytically calculated from the gaze angular velocity of the measured object (S131), and removes the analytically calculated angular velocity disturbance. The disturbance control signal is configured to be possible (S132). As the follower control signal and the disturbance control signal are applied to the servo amplifier and the servomotor to drive the gimbal (S14), the camera module can take a stable image without shaking the gaze.

Although the embodiments have been described in detail above, the scope of the present invention is not limited thereto, and various modifications and improvements of those skilled in the art using the basic concept of the present invention defined in the following claims are also provided. Belongs to

100: gaze stabilization system
110: Kim Beol
120: angular velocity sensor
130: servo controller
131: tracking controller
132: disturbance controller

Claims (19)

In the gaze stabilization system of the object,
A gimbal driven by the first and second axes;
An angular velocity sensor for measuring the gaze angular velocity of the object; And
And a servo controller outputting a signal for controlling the gimbal,
The servo controller,
A tracking controller that outputs a tracking control signal for controlling the gimbal to follow the target gaze, according to a command input and a feedback input of the angular velocity of the gaze of the object; And
And a disturbance controller outputting a disturbance control signal for controlling the gimbal to cancel the angular velocity disturbance applied to the object,
The angular velocity disturbance is a disturbance flowing into the third axis rather than the driving axis of the gimbal,
The tracking controller and the disturbance controller are configured independently,
The disturbance control signal output from the disturbance controller is summed with the following control signal output from the following controller,
The combined disturbance control signal and tracking control signal are provided to a servo amplifier and a servo motor to drive the gimbal, a gaze stabilization system. According to claim 1,
The disturbance controller,
A gaze stabilization system that receives the measured angular velocity of the measured object and outputs the disturbance control signal to cancel the angular velocity disturbance. According to claim 1,
The disturbance controller,
A gaze stabilization system designed to cancel the analytically calculated angular velocity disturbance. According to claim 3,
The angular velocity disturbance is calculated by the following equation,
(Mathematics)
wR1z = wLOSz*cosΘ-wLOSx*sinΘ
The wR1z is the angular velocity disturbance, the wLOSz is the gaze angular velocity of the object with respect to the third axis of the gaze coordinate system, the wLOSx is the gaze angular velocity of the object with respect to the first axis of the gaze coordinate system, and the Θ is the A gaze stabilization system indicating the driving angle of the gimbal with respect to the second axis. According to claim 1,
The tracking control signal and the disturbance control signal are signals that control the angular velocity at which the gimbal rotates with respect to the first axis. delete delete delete According to claim 1,
The gaze angular velocity of the object is measured directly by the angular velocity sensor, or indirectly measured in a manner of calculating the gaze angular velocity of the object by converting coordinates of other measured angular velocity. According to claim 1,
The angular velocity sensor,
A gaze stabilization system consisting of a 1-axis sensor capable of sensing angular velocity on 1 axis, a 2-axis sensor capable of sensing angular velocity on 2 axes, or a 3-axis sensor capable of sensing angular velocity on 3 axes. According to claim 1,
A gaze stabilization system further comprising at least one external gimbal mounted on the outside of the gimbal and having at least one axis of freedom. According to claim 1,
The first axis and the second axis is an azimuth axis and an elevation axis, and the third axis is a roll axis (horizontal axis). According to claim 1,
The first axis, the second axis, and the third axis is a roll axis (roll axis), a pitch axis (pitch axis), and yaw axis (yaw axis), the gaze stabilization system. According to claim 1,
A gaze stabilization system mounted on the aircraft together with the object. According to claim 1,
The object is a camera module, gaze stabilization system. In the method of stabilizing the gaze of an object using gimbal driven in the first axis and the second axis,
Measuring the gaze angular velocity of the object;
Outputting a tracking control signal controlling the gimbal so that the object follows a target gaze according to a command input and a feedback input of the angular velocity of the gaze of the object; And
And outputting a disturbance control signal for controlling the gimbal to cancel the angular velocity disturbance applied to the object,
The angular velocity disturbance is a disturbance flowing into the third axis rather than the driving axis of the gimbal,
Summing the disturbance control signal and the following control signal; And
And providing the combined disturbance control signal and tracking control signal to a servo amplifier and a servo motor to drive the gimbal. The method of claim 16,
The step of outputting the disturbance control signal,
Calculating the angular velocity disturbance from the measured angular velocity of the object; And
And constructing the disturbance control signal to cancel the calculated angular velocity disturbance. The method of claim 17,
The angular velocity disturbance is calculated by the following equation,
(Mathematics)
wR1z = wLOSz*cosΘ-wLOSx*sinΘ
The wR1z is an angular velocity disturbance, the wLOSz is the gaze angular velocity of the object with respect to the third axis of the gaze coordinate system, the wLOSx is a gaze angular velocity of the object with respect to the first axis of the gaze coordinate system, and the Θ is the first A gaze stabilization method, which represents the driving angle of the gimbal with respect to the two axes. A recording medium recording a program for executing a method according to any one of claims 16 to 18 on a computer.

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