阅读说明：本技术 一种激光架束制导编码盘及编码器 (Laser frame beam guidance coding disc and encoder ) 是由 范哲源 韩飞 刘西站 吕园成 李粉利 刘改化 于 2021-07-19 设计创作，主要内容包括：本发明涉及光电编码盘,具体涉及一种激光架束制导编码盘及编码器,用于解决现有编码盘码道宽度固定不变,若只接收到一种频率,无法进行位置解算,以及现有编码盘根据接收到的频率信息,只能定性判断光斑偏离情况,无法精确判断光斑位置偏差的不足之处。该激光架束制导编码盘,包括编码盘基体,以编码盘基体中心为圆心,定义逆时针方向为正向,在编码盘基体内码道一端的连线为0°刻线；所述内码道位于编码盘的(0°～180°),外码道位于编码盘的(90°～270°)；内码道上设有宽度不等的第一码道和第二码道,外码道上设有宽度不等的第三码道和第四码道,并且内码道和外码道上均设有抗干扰的第五码道。同时,本发明还提供一种采用上述激光架束制导编码盘的编码器。(The invention relates to a photoelectric coding disc, in particular to a laser frame beam guidance coding disc and an encoder, which are used for solving the defects that the width of a code channel of the existing coding disc is fixed, position calculation cannot be carried out if only one frequency is received, and the existing coding disc can only qualitatively judge the light spot deviation condition and cannot accurately judge the light spot position deviation according to the received frequency information. The laser frame beam guidance coding disc comprises a coding disc base body, wherein the center of the coding disc base body is taken as the circle center, the anticlockwise direction is defined as the forward direction, and a connecting line at one end of a code channel in the coding disc base body is scribed at an angle of 0 degrees; the inner code channel is positioned at (0-180) degrees of the coding disc, and the outer code channel is positioned at (90-270) degrees of the coding disc; the inner code channel is provided with a first code channel and a second code channel which are different in width, the outer code channel is provided with a third code channel and a fourth code channel which are different in width, and the inner code channel and the outer code channel are provided with anti-interference fifth code channels. Meanwhile, the invention also provides an encoder adopting the laser frame beam guidance encoding disk.)

1. A laser frame beam guidance code disc comprising a code disc base body (10), characterized in that: the center of the coding disc base body (10) is taken as the circle center, the anticlockwise direction is defined as the forward direction, and the line connecting one end of the code channel in the coding disc base body (10) is scribed at 0 degree;

the inner code channel is positioned on the coding disc (0-180 degrees), the inner diameter of the inner code channel is a, and the width of the inner code channel is c;

the outer code channel is positioned on the coding disc (90-270 degrees), the inner diameter of the outer code channel is b, and the width of the outer code channel is c;

the distance between the inner code channel and the outer code channel is d;

the inner code channel and the outer code channel are both provided with a fifth code channel (5) with e width and fixed frequency, and the fifth code channel (5) is provided with X₅For the transparent areas and the non-transparent areas, the angles of the transparent areas and the non-transparent areas in each pair are the same;

e is less than or equal to (c/2);

the inner code channel is also provided with a first code channel (1) and a second code channel (2); x is arranged on the first code channel (1)₁For the light-transmitting areas and the non-light-transmitting areas, the angles occupied by the light-transmitting areas and the non-light-transmitting areas in each pair are the same, and the first code channel (1) is fixed in frequency and comprises a first equal-width code channel and a first width gradually-changing code channel which are sequentially arranged in the forward direction; x is arranged on the second code channel (2)₂To the light transmission regionThe light-transmitting areas and the non-light-transmitting areas in each pair occupy the same angle, the frequency of the second code channel (2) is fixed, and the second code channel comprises a second width gradually-changing code channel and a second equal-width code channel which are sequentially arranged in the forward direction;

the first equal-width code channel is positioned in a range of (0-A DEG); the first code channel, the fifth code channel (5) and the second code channel with gradually changing widths are positioned in an (A-B DEG) interval; the second equal-width code channel is positioned at (B-180 degrees); the 0 ° < a ° < B ° <180 °;

the first code channel, the fifth code channel (5) and the second code channel are distributed in sequence from outside to inside; wherein, the inner diameter of the first width gradually-changing code track is smoothly transited from (a + e) to (a + c) along the positive direction; the inner diameter of the second width gradually-changed code channel is smoothly transited from a to (a + c-e) along the positive direction; the rest area is a fifth code channel (5);

the outer code channel is also provided with a third code channel (3) and a fourth code channel (4); x is arranged on the third code channel (3)₃For the light-transmitting areas and the non-light-transmitting areas, the angles occupied by the light-transmitting areas and the non-light-transmitting areas in each pair are the same, and the frequency of the third code channel (3) is fixed and comprises a third code channel with equal width and a third code channel with gradually changed width which are sequentially arranged in the forward direction; x is arranged on the fourth code channel (4)₄For the light-transmitting areas and the non-light-transmitting areas, the angles occupied by the light-transmitting areas and the non-light-transmitting areas in each pair are the same, and the frequency of the fourth code channel (4) is fixed and comprises a fourth code channel with gradually changed width and a fourth code channel with equal width which are sequentially arranged in the forward direction;

the third equal-width code channel is positioned in a (90-C) range; the third code channel, the fifth code channel (5) and the fourth code channel are positioned in a (C-D) degree interval; the second equal-width code channel is positioned at (D-270 degrees); the 90 ° < C ° < D ° <270 °;

the third width gradient code channel, the fifth code channel (5) and the fourth width gradient code channel are sequentially distributed from outside to inside; wherein, the inner diameter of the third width gradually-changing code track is smoothly transited from (b + e) to (b + c) along the positive direction; the inner diameter of the fourth width gradually-changed code channel is smoothly transited from b to (b + c-e) along the positive direction; the other areas are the fifth code channel;

the (B-A) is equal to the (D-C);

said X₁、X₂、X₃、X₄、X₅Are all not equal.

2. A laser frame beam guidance encoding disk as defined in claim 1, wherein:

the first width gradient code track has an outer diameter of (a + c), an inner diameter obtained by fitting Q points and point coordinatesIs determined by the following formula:

n₁＝0,1,2……Q

the inner diameter of the second width gradient code channel is a, the outer diameter of the second width gradient code channel is obtained by Q point fitting, and the point coordinates Is determined by the following formula:

n₂＝0,1,2……Q

the outer diameter of the third width gradient code track is (b + c), the inner diameter of the third width gradient code track is obtained by fitting Q points, and the third width gradient code track is positioned on the baseSign boardIs determined by the following formula:

n₃＝0,1,2……Q

the inner diameter of the fourth width gradient code channel is b, the outer diameter of the fourth width gradient code channel is obtained by Q point fitting, and the coordinates of the points are Is determined by the following formula:

n₄＝0,1,2……Q

the value of Q is (2 xX)₅)。

3. A laser frame beam guidance encoding disk as defined in claim 2, wherein: the value of A degrees is 36 degrees, the value of B degrees is 144 degrees, the value of C degrees is 126 degrees, and the value of D degrees is 234 degrees.

4. A laser frame beam guidance encoding disk as defined in claim 3, wherein: the width e of the fifth code channel (5) is 1.4 mm.

5. A laser frame beam guidance encoding disk as defined in claim 4, wherein: the value of the inner diameter a of the inner code channel is 21 mm; the inner diameter b of the outer code channel is 27 mm; the width of the inner code channel and the width c of the outer code channel are 3 mm; the distance d between the inner code channel and the outer code channel is 3 mm.

6. A laser frame beam guidance encoding disk according to any one of claims 1 to 5, wherein: the coding disc base body (10) is made of optical glass.

7. A laser frame beam guidance encoder is characterized in that: use of a laser frame beam guidance encoder disk as claimed in any one of claims 1 to 6.

Technical Field

The invention relates to a photoelectric coding disc, in particular to a laser frame beam guidance coding disc and an encoder.

Background

In the laser beam-erecting guidance process, a sighting hand firstly manually tracks and aims at a target through an observing and aiming assembly of a ground emission guidance device or a thermal image sighting device, a laser signal modulated is emitted by the laser guidance assembly to form a space information field for a projectile body to identify a coordinate position, a receiver positioned at the tail of the projectile receives the laser modulation signal and converts the laser modulation signal into an electric signal, after the information is processed, the deviation between a projectile axis and a light beam center is calculated, and the electric signal is fed back to an on-projectile control system, so that the projectile body is controlled to fly along the light beam center until the projectile body hits the target.

Referring to fig. 1, a laser beam guidance simulation system based on the above principle is applied to ground simulation beam guidance work process, and comprises a ground guidance irradiator, a missile tail receiver and a wireless transparent transmission system. The laser transmitting optical axis is aligned to the missile tail receiver through a sighting device on the ground guidance irradiator, laser beams continuously transmitted by a semiconductor laser are projected onto an outer code channel of a coding disc through a light condensing system, are emitted from an inner code channel through an image transfer system, and then are emitted out through a zoom projection system to form an information control field for the missile tail receiver to identify the coordinate position; the bullet tail receiver receives the laser coding signal, and after signal processing, the deviation of the position of the bullet tail receiver in the direction and the pitching direction relative to the center of the light spot is calculated; and the deviation data and the turntable data information are output to a wireless transparent transmission system and are sent to a signal processing computer at the ground guidance irradiator end through a transmitting antenna, so that closed loop of the data is completed.

Referring to fig. 2 and 3, the specific modulation process of the code disc 02 in the system is as follows: the semiconductor laser 01 outputs continuous laser, which is vertically projected to the code channel 022 of the code disk, the code disk 02 rotates at the frequency w, the laser beam is cut by the black and white grating on the code channel 022 of the code disk at different intervals, and after a certain time, the laser beam contains f₃、f₄、f₅Guided laser beam slave code of three frequenciesThe disk 02 exits to the first prism 031 and the second prism 033, passes through the code channel 021 of the encoding disk again, and contains f after a certain time₁、f₅、f₂The guided laser beams of three frequencies emerge from the code wheel 02 to the turning third prism 033 and the fourth prism 034, where the beams enter the zoom optical system 04. Finally, a laser information field containing 5 pulse frequencies is projected in space.

Referring to fig. 2 and 3, when the code wheel 02 is rotated at a frequency of 100Hz, that is, a period of 10ms, the black and white grating of the information pattern of the code wheel 02 cuts the laser beam from top to bottom at different frequencies, and after 5ms, the laser beam is cut from right to left, and therefore f is included in the 5ms upper half period₁、f₅、f₂Laser shots of three frequencies that undergo time control of yaw direction; the lower half period of 5ms contains f₃、f₅、f₄Laser shots of three frequencies, which undergo time-controlled pitch direction. Wherein, the frequency f₅The main function of (2) is to enhance the immunity of the guided laser beam to interference. And the duration of each frequency pulse signal increases as the distance of the error of the tail receiver from the center of the control field increases. Therefore, the position information of the bullet tail receiver deviating from the center of the control field at a certain moment can be obtained by measuring the duration time of the signals with different frequencies received by the laser receiver.

A mathematical model of the coded modulation technique is shown in fig. 4. Wherein MN represents the central line of the code track of the code disc, X is the error amount deviating from the optical axis, and DeltaR represents the width of the annular code track. T is a period, T₁、T₂Respectively showing the frequency f experienced by a certain light spot after the rotation of the code disc in one period₁And f₂Time of (d). According to the principle of similar triangleThenSince T and DeltaR are both constant, X is only equal to T₁、T₂The difference of (c) is linear.

As shown in fig. 5, the width of a code track is usually fixed, and when a receiver is located at an information field fixing position, as shown in a position a in the figure, if only one frequency can be received, only the one frequency can be always received, and in the absence of other frequency information, position calculation cannot be performed; in addition, the receiver receives the frequency f after the transmitted beam has passed through a conventional chopper wheel₁、f₂、f₃、f₄Is a scanning time of_f1、τ_f2、τ_f3、τ_f4Calculating a modulation factor K characterizing the position information_x、K_yThe modulation factor is calculated by the following formula:

by judging K_x、K_yWhether the deviation direction of the receiver is larger than 0 or smaller than 0 is judged, and the deviation can only be judged qualitatively, and the deviation size cannot be judged accurately.

Disclosure of Invention

The invention aims to solve the defects that the width of a code channel of the existing coding disc is fixed, if only one frequency is received, no other frequency information exists, position calculation cannot be carried out, and the existing coding disc can only qualitatively judge the light spot deviation condition according to the received frequency information and cannot accurately judge the light spot position deviation, and provides a laser frame beam guidance coding disc and an encoder.

In order to solve the defects, the invention provides the following technical solutions:

a laser frame beam guidance coding disc comprises a coding disc base body, and is characterized in that:

the center of the coding disc matrix is taken as the center of a circle, the anticlockwise direction is defined as the forward direction, and a connecting line at one end of a code channel in the coding disc matrix is a 0-degree scribed line;

the inner code channel is positioned on the coding disc (0-180 degrees), the inner diameter of the inner code channel is a, and the width of the inner code channel is c;

the outer code channel is positioned on the coding disc (90-270 degrees), the inner diameter of the outer code channel is b, and the width of the outer code channel is c;

the distance between the inner code channel and the outer code channel is d;

the inner code channel and the outer code channel are both provided with a fifth code channel with e width and fixed frequency, and the fifth code channel is provided with X₅For the transparent areas and the non-transparent areas, the angles of the transparent areas and the non-transparent areas in each pair are the same;

e is less than or equal to (c/2);

the inner code channel is also provided with a first code channel and a second code channel; x is arranged on the first code channel₁For the light-transmitting areas and the non-light-transmitting areas, the angles occupied by the light-transmitting areas and the non-light-transmitting areas in each pair are the same, and the first code channel has fixed frequency and comprises a first equal-width code channel and a first width gradually-changing code channel which are sequentially arranged in the forward direction; x is arranged on the second code channel₂For the light-transmitting areas and the non-light-transmitting areas, the angles occupied by the light-transmitting areas and the non-light-transmitting areas in each pair are the same, and the frequency of the second code channel is fixed and comprises a second width gradually-changing code channel and a second equal-width code channel which are sequentially arranged in the forward direction;

the first equal-width code channel is positioned in a range of (0-A DEG); the first code channel, the fifth code channel and the second code channel with gradually changed widths are positioned in an (A-B DEG) interval; the second equal-width code channel is positioned at (B-180 degrees); the 0 ° < a ° < B ° <180 °;

the first code channel, the fifth code channel and the second code channel are distributed in sequence from outside to inside; wherein, the inner diameter of the first width gradually-changing code track is smoothly transited from (a + e) to (a + c) along the positive direction; the inner diameter of the second width gradually-changed code channel is smoothly transited from a to (a + c-e) along the positive direction; the other areas are the fifth code channel;

the outer code channel is also provided with a third code channel and a fourth code channel; the third code channel is provided with X₃For the light-transmitting area and the non-light-transmitting area, the angles occupied by the light-transmitting area and the non-light-transmitting area in each pair are the same, the frequency of the third code channel is fixed, and the third code channel comprises a third code channel with equal width and a third code channel with gradually changed width which are sequentially arranged in the forward directionCode channel; the fourth code channel is provided with X₄For the light-transmitting areas and the non-light-transmitting areas, the angles occupied by the light-transmitting areas and the non-light-transmitting areas in each pair are the same, and the frequency of the fourth code channel is fixed and comprises a fourth code channel with gradually changed width and a fourth code channel with equal width which are sequentially arranged in the forward direction;

the third equal-width code channel is positioned in a (90-C) range; the third code channel, the fifth code channel and the fourth code channel with gradually changed widths are positioned in a (C-D) range; the second equal-width code channel is positioned at (D-270 degrees); the 90 ° < C ° < D ° <270 °;

the third width gradient code channel, the fifth code channel and the fourth width gradient code channel are sequentially distributed from outside to inside; wherein, the inner diameter of the third width gradually-changing code track is smoothly transited from (b + e) to (b + c) along the positive direction; the inner diameter of the fourth width gradually-changed code channel is smoothly transited from b to (b + c-e) along the positive direction; the other areas are the fifth code channel;

the (B-A) is equal to the (D-C);

said X₁、X₂、X₃、X₄、X₅Are all not equal.

Further, the first width gradient code track has an outer diameter of (a + c), an inner diameter of the first width gradient code track is obtained by fitting Q points, and coordinates of the points are obtainedIs determined by the following formula:

n₁＝0，1，2……Q

the inner diameter of the second width gradient code channel is a, the outer diameter of the second width gradient code channel is obtained by Q point fitting, and the point coordinates Is determined by the following formula:

n₂＝0,1,2……Q

the outer diameter of the third width gradient code track is (b + c), the inner diameter of the third width gradient code track is obtained by fitting Q points, and the coordinates of the points areIs determined by the following formula:

n₃＝0，1,2……Q

the inner diameter of the fourth width gradient code channel is b, the outer diameter of the fourth width gradient code channel is obtained by Q point fitting, and the coordinates of the points are Is determined by the following formula:

n₄＝0,1,2……Q

the value of Q is (2 xX)₅)。

Further, the value of a ° is 36 °, the value of B ° is 144 °, the value of C ° is 126 °, and the value of D ° is 234 °.

Further, the value of the fifth code channel width e is 1.4 mm.

Furthermore, the value of the inner diameter a of the inner code channel is 21 mm; the inner diameter b of the outer code channel is 27 mm; the width of the inner code channel and the width c of the outer code channel are 3 mm; the distance d between the inner code channel and the outer code channel is 3 mm.

Furthermore, the coding disc base body is made of optical glass.

Meanwhile, the invention also provides a laser frame beam guidance encoder which is characterized in that: and adopting the laser frame beam guidance coding disc.

Compared with the prior art, the invention has the beneficial effects that:

(1) in the invention, the first code channel, the second code channel, the third code channel and the fourth code channel are designed by combining the code channels with the same width and the code channels with gradually changed widths, and the positions of the code channels with gradually changed widths on the coded disc base body are overlapped, so that the position of a projectile body deviating from a light spot can be accurately calculated when only one frequency information is received in the pitching or yawing direction; in addition, the fifth code channel adopts an asymmetric design, so that the anti-interference performance of the guided laser beam is further enhanced.

(2) The invention adopts the design of gradually changing the frequency width of the inner code channel and the outer code channel, and only when the frequency numbers are accurate and equal, the position is the center of the facula, thereby improving the guidance precision.

Drawings

FIG. 1 is a flow chart of a prior art laser beam steering guidance simulation system;

FIG. 2 is a schematic diagram of the operation of the system of FIG. 1;

fig. 3 is a schematic diagram of the operation principle of the code wheel in the system of fig. 1.

The reference numerals of fig. 2 to 3 are explained as follows: 01-a semiconductor laser; 02-code disc, 021-code disc inner code channel and 022-code disc outer code channel; 031-first prism, 032-second prism, 033-third prism, 034-fourth prism; 04-zoom optical system.

FIG. 4 is a mathematical model of the code wheel of FIG. 3;

FIG. 5 is a schematic structural diagram of a conventional encoder disk.

FIG. 6 is a schematic structural diagram of an embodiment of a laser frame beam guidance encoding disk of the present invention;

the reference numerals of fig. 6 are explained as follows: 10-code disc base body, 1-first code channel, 2-second code channel, 3-third code channel, 4-fourth code channel and 5-fifth code channel.

Detailed Description

The invention will be further described with reference to the drawings and exemplary embodiments.

Referring to fig. 6, the laser frame beam guidance encoding disc comprises an encoding disc substrate 10 made of quartz, wherein the center of the encoding disc substrate 10 is taken as the center of a circle, the anticlockwise direction is defined as the forward direction, and a connecting line at one end of a code channel in the encoding disc substrate 10 is a 0-degree reticle; the inner code channel is positioned on the coding disc (0-180 degrees), the inner diameter of the inner code channel is 21mm, and the width of the inner code channel is 3 mm; the outer code channel is positioned at (90-270 degrees), the inner diameter of the outer code channel is 27mm, and the width of the outer code channel is 3 mm; the distance between the inner code channel and the outer code channel is 3 mm.

The inner code channel and the outer code channel are both provided with a fifth code channel 5 with the width of 1.4mm and the frequency fixed, and the fifth code channel 5 is provided with an X₅For the transparent region and the non-transparent region, the transparent region and the non-transparent region in each pair occupy

The inner code channel is also provided with a first code channel 1 and a second code channel 2; x is arranged on the first code channel 1₁For the transparent region and the non-transparent region, the transparent region and the non-transparent region in each pair occupyThe first code channel 1 is fixed in frequency and comprisesThe first equal-width code channel and the first gradient-width code channel are arranged in sequence in the forward direction; x is arranged on the second code channel 2₂For the transparent region and the non-transparent region, the transparent region and the non-transparent region in each pair occupyThe second code channel 2 is fixed in frequency and comprises a second code channel with gradually changed width and a second code channel with equal width which are sequentially arranged in the forward direction; the first equal-width code channel is located at (0-36 degrees); the first code channel, the fifth code channel 5 and the second code channel with gradually changed width are positioned at (36-124 degrees); the second equal-width code channel is positioned at (124-180 degrees); the first code channel with gradually changed width, the fifth code channel 5 and the second code channel with gradually changed width are distributed from outside to inside in sequence; wherein, the inner diameter of the first width gradient code channel is smoothly transited from 22.4mm to 24mm along the positive direction, the inner diameter of the second width gradient code channel is smoothly transited from 21mm to 22.6mm along the positive direction, and the rest area is the fifth code channel 5.

The first width gradient code channel has an outer diameter of 24mm and an inner diameter obtained by fitting Q points, and the point coordinatesIs determined by the following formula:

n₁＝0,1,2……Q

the inner diameter of the second width gradient code channel is 21mm, the outer diameter of the second width gradient code channel is obtained by Q point fitting, and the point coordinatesIs determined by the following formula:

n₂＝0,1,2……Q

the outer code channel is also provided with a third code channel 3 and a fourth code channel 4; x is arranged on the third code channel 3₃For the transparent region and the non-transparent region, the transparent region and the non-transparent region in each pair occupyThe third code channel 3 has fixed frequency and comprises a third equal-width code channel and a third gradient code channel which are sequentially arranged in the forward direction; x is arranged on the fourth code channel 4₄For the transparent region and the non-transparent region, the transparent region and the non-transparent region in each pair occupyThe fourth code channel 4 has fixed frequency and comprises a fourth code channel with gradually changed width and a fourth code channel with equal width which are sequentially arranged in the forward direction; the third equal-width code channel is positioned at (90-126 degrees); the third, fifth and fourth code channels with gradually changed widths are positioned at (126-234 degrees); the second equal-width code channel is positioned at (234-270 degrees); the third width gradient code channel, the fifth code channel 5 and the fourth width gradient code channel are sequentially distributed from outside to inside; wherein, the inner diameter of the third width gradient code channel is smoothly transited from 28.4mm to 30mm along the positive direction, the inner diameter of the fourth width gradient code channel is smoothly transited from 27mm to 28.6mm along the positive direction, and the rest area is the fifth code channel 5.

The outer diameter of the third width gradient code channel is 30mm, the inner diameter of the third width gradient code channel is obtained by Q point fitting, and the point coordinatesIs determined by the following formula:

n₃＝0，1,2……Q

the inner diameter of the fourth width gradient code channel is 27mm, the outer diameter of the fourth width gradient code channel is obtained by Q point fitting, and the point coordinatesIs determined by the following formula:

n₄＝0,1,2……Q

the value of Q is (2 xX)₅)。

Said X₁、X₂、X₃、X₄、X₅Are not equal, and each pair of transmissive and non-transmissive regions may be sequentially alternated with transmissive and non-transmissive regions, or sequentially alternated with transmissive regions.

In this embodiment, the encoding disk rotates at a frequency of 100Hz, i.e. the period is 10ms, and when the encoding disk rotates, the black and white grating cuts the laser beams at different frequencies; in the first half period of 5ms, when the coding disc cuts the laser beam from right to left, the light spot passes through the first code channel 1, the fifth code channel 5 and the second code channel 2, and the yaw direction is controlled by the time; in the next half period of 5ms, when the coding disc cuts the laser beam from top to bottom, the light spot passes through the third code channel 3, the fifth code channel 5 and the fourth code channel 4, and the pitching direction of the light spot is controlled by time; the fifth code channel 5 adopts an asymmetric design, and the anti-interference performance of the guided laser beam is further enhanced.

In the embodiment, in the pitching or yawing direction, when only one type of frequency information is received, the position of the projectile body deviating from the light spot can be accurately calculated; in addition, on the same code channel, the inner side frequency width and the outer side frequency width are designed in a gradual change mode, and the center position of the light spot is the right center position only when the inner side frequency number and the outer side frequency number are accurately equal, so that the guidance precision is improved.

Meanwhile, the invention also provides a laser frame beam guidance encoder which adopts the laser frame beam guidance encoding disc.

The above embodiments are only used for illustrating the technical solutions of the present invention, and not for limiting the same, and it is obvious for a person skilled in the art to modify the specific technical solutions described in the foregoing embodiments or to substitute part of the technical features, and these modifications or substitutions do not make the essence of the corresponding technical solutions depart from the scope of the technical solutions protected by the present invention.