A servo loop boundary switching variable structure control method for a four-axis inertial stabilization platform

Abstract

A servo loop boundary switching variable structure control method for a four-axis inertial stabilization platform includes: setting a restricted area near the singular point; obtaining the angular velocity of the platform in the X-axis region based on the output angular velocity of the gyroscope mounted on the platform. p Axis, Y p Axis and Z p The angular velocity components on the axes are used to obtain the internal relative rotation angle and angular velocity of the four-axis inertial stabilized platform system. Using the restricted area boundary as a marker, different control strategies are adopted inside and outside the restricted area. Based on the angular velocity components and the internal relative rotation angle, the Z-axis position of the platform is calculated. p The resultant rotational angular velocity ω of the shaft z The inner frame in Y p1 The resultant rotational angular velocity ω of the shaft y The framework in X p2 The resultant rotational angular velocity ω of the shaft x and outer frame in Y p3 The resultant rotational angular velocity ω of the shaft yk′ This invention can avoid the occurrence of singular values ​​during the servo loop decoupling process, ensuring the stability of the platform body relative to the inertial space, and has the advantages of full attitude control and high precision.

Description

Technical Field

[0001] This invention relates to a servo loop boundary switching variable structure control method for a four-axis inertial stabilization platform, which relates to the field of inertial measurement technology and is used for high-precision navigation in all attitudes in the aviation and aerospace fields. Background Technology

[0002] Because three-axis inertial platform systems suffer from "frame locking," making it difficult to meet the requirements of large-scale maneuvering of the platform, four-axis inertial platform systems were developed. Compared to three-axis inertial platform systems, four-axis inertial platform systems add an outer frame to the platform body, inner frame, and middle frame. The outer frame is located between the middle frame and the base of the platform.

[0003] To stabilize the platform relative to inertial space, the existing technology provides the following solution: the servo loop is based on the inner frame angle β. yk and the angle β of the middle frame xk Different decouplers are used in different regions, see the reference "Variable Structure Partition Control of Four-Axis Gyroscope Stabilized Platform, Tsinghua University Journal Vol.50, No.7, 2010". The reason for using partition control is that when controlling the four axis motors in conjunction with the outputs of the three gyroscopes and any frame angle, there is a region where the motor driving torque is infinite, which may cause control failure.

[0004] When the platform moves, the angles of the inner frame and the middle frame will be in different ranges. When using zoned control, there will be switching between different control signals. Even with switching conditions using hysteresis relay characteristics, the platform will still experience instantaneous vibration at the moment of switching, resulting in swaying of the platform relative to space. Therefore, the division of zones should be minimized as much as possible, provided that the platform is stable relative to inertial space. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to overcome the shortcomings of the prior art and solve the problem of frequent shaking caused by excessively fine interval switching.

[0006] The objective of this invention is achieved through the following technical solutions:

[0007] A servo loop boundary switching variable structure control method for a four-axis inertial stabilization platform includes:

[0008] Based on the angular velocity output by the gyroscope mounted on the platform, the position of the platform in the X direction is obtained. p Axis, Y p Axis and Z p angular velocity components on the axis

[0009] Measuring the X-axis of the outer frame around the coordinate system of the middle frame p2 The angle β of the shaft rotation xkThe Y-axis of the middle frame around the inner frame's body coordinate system p1 The angle β of the shaft rotation yk Z-axis of the inner frame around the body coordinate system p The angle β of the shaft rotation zk ;

[0010] Set the critical parameter r for the variable structure;

[0011] Based on the measured β zk and Determine the rotational angular velocity of the platform and the inner frame;

[0012] Based on the measured β xk β yk β zk , and And the critical parameter r, calculate the rotational angular velocities of the middle frame and the outer frame:

[0013] When cos 2 β xk sin 2 β yk When <1-r, we have

[0014]

[0015]

[0016] When cos 2 β xk sin 2 β yk ≥1-r, and β yk Must satisfy ||β yk |-90°|≤1.2° or β yk When -270°|≤1.2°, we have

[0017] ω x =0;

[0018] ω yk′ =(β) yk -β yk0 )secβ xk ;

[0019] When cos 2 β xk sin 2 β yk ≥1-r, and β yk Must satisfy ||β yk |-90°|>1.2° and β yk When -270°|>1.2°, there is

[0020]

[0021] ω yk′ =(β) yk -β yk0 )secβ xk ;

[0022] Where, ω x For the medium frame X p2 The resultant rotational angular velocity of the shaft; ω yk′ For the outer frame Y p3 The resultant rotational angular velocity of the shaft.

[0023] In one embodiment of the present invention, based on the measured β zk and Calculate the rotational angular velocity of the platform and inner frame:

[0024]

[0025]

[0026] Where, ω z For Taiwan Z p The resultant rotational angular velocity of the shaft; ω y For the inner frame Y p1 The resultant rotational angular velocity of the shaft.

[0027] In one embodiment of the present invention, the relative rotation angle inside the four-axis inertial stabilized platform system is measured by the following method:

[0028] X in the outer frame p2 An angle sensor is mounted on the axis to measure the X-axis of the outer frame around the coordinate system of the middle frame. p2 The angle β of the shaft rotation xk ; in the inner frame Y p1 An angle sensor is installed on the axis to measure the Y-axis of the middle frame around the inner frame's coordinate system. p1 The angle β of the shaft rotation yk ; in Taiwan Z p A sensor mounted on the axis measures the Z-axis coordinate of the inner frame around the body coordinate system of the stage. p The angle β of the shaft rotation zk .

[0029] In one embodiment of the present invention, the rotation angle β yk The value range is -90 to 270°; rotation angle β zk β xk β yk′ The value range is -180 to 180°.

[0030] In one embodiment of the present invention, the four-axis inertial stabilization platform includes a base, an outer frame, a middle frame, an inner frame, and a platform body, with corresponding body coordinate systems of the base body coordinate system X1Y1Z1 and the outer frame coordinate system X... p3 Y p3 Z p3 , Medium frame body coordinate system X p2 Y p2 Z p2 The inner frame body coordinate system X p1 Y p1 Z p1 and the X coordinate system of the platform body p Y p Z p The origins of the five coordinate systems coincide, and: the Z-axis of the platform body coordinate system... p Z-axis and the coordinate system of the inner frame p1 The axes coincide, and the Y-axis of the body coordinate system of the middle frame is... p2 Y-axis and the coordinate system of the inner frame p1 The axes coincide, and the X coordinate of the outer frame body coordinate system is... p3 The X-axis of the axis and the body coordinate system of the middle frame p2 The axes coincide, the X1 axis of the base body coordinate system and the Y axis of the outer frame body coordinate system. p3 The axes coincide; wherein, the base is fixedly connected to the carrier, and when the stable platform system undergoes internal relative rotation under the drive of the carrier, the base revolves around the Y-axis of the outer frame's body coordinate system. p3 The axis rotates, and the outer frame revolves around the X coordinate system of the middle frame. p2 The axis rotates, and the middle frame rotates around the Y-axis of the inner frame's body coordinate system. p1 The axis rotates, and the inner frame rotates around the Z-axis of the platform's coordinate system. p The shaft rotates.

[0031] In one embodiment of the present invention, the four-axis inertial stabilization platform has multiple singularities. A circular exclusion zone is used to remove the singularities to avoid frame locking in the control method.

[0032] In one embodiment of the present invention, the condition for a singularity is 1-cos 2 β xk sin 2 β yk =0.

[0033] In one embodiment of the present invention, the singularity includes (β) yk ,β xk ) = (90°, 0°), (90°, 180°), (90°, -180°), (270°, 0°), (270°, 180°), (270°, -180°), (-90°, 180°), (-90°, 0°), (-90°, -180°).

[0034] Compared with the prior art, the present invention has the following advantages:

[0035] (1) The present invention provides a servo loop boundary switching variable structure control method for a four-axis inertial stabilization platform. The single decoupler can adapt to the frame angle state at non-singular points, reducing the density of interval division, which helps to reduce the frequent shaking caused by excessively fine interval switching.

[0036] (2) This invention provides a servo loop boundary switching variable structure control method for a four-axis inertial stabilization platform. By setting a control method to drive away the restricted area near the singular point to avoid the occurrence of singular values, the "frame lock" is overcome, thereby realizing the full attitude adaptability of the inertial platform body relative to the inertial space. Attached Figure Description

[0037] Figure 1 A schematic diagram of a four-axis platform structure when the angles of the four frames are zero.

[0038] Figure 2 This is a schematic diagram showing the relationship between the five body coordinate systems in a four-axis inertial stabilization platform system.

[0039] Figure 3 This is a flowchart of the steps of a servo loop boundary switching variable structure control method for a four-axis inertial stabilization platform proposed in this invention;

[0040] Figure 4 This is the singularity of the four-axis platform of the present invention;

[0041] Figure 5 It is a region divided according to the angles of the inner frame and the middle frame in the variable structure zoning control;

[0042] Figure 6 This is the region divided according to the angles of the inner frame and the middle frame in the variable structure control of this invention;

[0043] Figure 7 This refers to the area where the inner and middle frames are located when minimum output energy control is employed;

[0044] Figure 8 This describes the change of the frame angle over time when minimum output energy control is employed.

[0045] Figure 9 This refers to the area where the angles of the inner frame and the middle frame are located when the boundary switching variable structure control of this invention is adopted;

[0046] Figure 10 This describes the change in frame angle over time when using the boundary switching variable structure control method of this invention. Detailed Implementation

[0047] To make the objectives, technical solutions, and advantages of the present invention clearer, the embodiments of the present invention will be described in further detail below with reference to the accompanying drawings.

[0048] The present invention provides a servo loop boundary switching variable structure control method for a four-axis inertial stabilization platform, which is implemented based on a four-axis inertial stabilization platform system. This four-axis stabilization platform system includes a base, outer frame, middle frame, inner frame, and platform body, as shown below. Figure 1 As shown. The corresponding body coordinate systems are the base body coordinate system X1Y1Z1 and the outer frame coordinate system X... p3 Y p3 Z p3 , Medium frame body coordinate system X p2 Y p2 Z p2 The inner frame body coordinate system X p1 Y p1 Z p1 and the X coordinate system of the platform body p Y p Z p .

[0049] like Figure 2 The diagram shows the relationship between the five coordinate systems. The origins of these five coordinate systems coincide, and they have the following relative constraints: the Z-axis of the platform body coordinate system... p Z-axis and the coordinate system of the inner frame p1 The axes coincide, and the Y-axis of the body coordinate system of the middle frame is... p2 Y-axis and the coordinate system of the inner frame p1 The axes coincide, and the X coordinate of the outer frame body coordinate system is... p3 The X-axis of the axis and the body coordinate system of the middle frame p2 The X1 axis of the base body coordinate system coincides with the Y-axis of the follower frame body coordinate system. The base is fixed to the carrier. When the stable platform system undergoes internal relative rotation under the drive of the carrier: the base rotates around the Y-axis of the outer frame body coordinate system... p3 The axis rotates by an angle β. yk′ The X coordinate system of the outer frame around the middle frame body. p2 The axis rotates by an angle β. xk ; Y-axis of the middle frame around the inner frame body coordinate system p1 The axis rotates by an angle β. yk The Z-axis of the inner frame around the body coordinate system of the platform p The axis rotates by an angle β. zk .

[0050] like Figure 3 The processing flowchart shown illustrates the following steps for implementing the servo loop boundary switching variable structure control method for the four-axis inertial platform system of this invention:

[0051] (1) Based on the angular velocity output by the gyroscope mounted on the platform, the position of the platform in the X direction is obtained. p Axis, Y p Axis and Z p angular velocity components on the axis

[0052] (2) The relative rotation angles inside the four-axis inertial stabilized platform system were measured, including: the X-axis of the outer frame around the coordinate system of the middle frame. p2 The angle β of the shaft rotation xk ; Y-axis of the middle frame around the inner frame body coordinate system p1 The angle β of the shaft rotation yk ; Z-axis of the inner frame around the body coordinate system of the platform p The angle β of the shaft rotation zk ;

[0053] (3) Set the critical parameter r of the variable structure (for example, take a value of 0.3);

[0054] (4) Based on the measured β xk β yk β zk , and And the critical parameter r, calculate the rotational angular velocity of the platform, inner frame, middle frame and outer frame. The specific calculation formula is as follows:

[0055] (4.1) Based on the measured β zk and Calculate the rotational angular velocity of the platform and inner frame:

[0056]

[0057]

[0058] Where, ω z For Taiwan Z p The resultant rotational angular velocity of the shaft; ω y For the inner frame Y p1 The resultant rotational angular velocity of the shaft;

[0059] (4.2) Based on the measured β xk β yk β zk , and And the critical parameter r, calculate the rotational angular velocities of the middle frame and the outer frame:

[0060] (4.2.1) When cos 2 β xk sin 2 β yk When <1-r, we have

[0061]

[0062]

[0063] (4.2.2) When cos 2 β xk sin 2 β yk ≥1-r, and β yk Must satisfy ||β yk |-90°|≤1.2° or |β yk When -270°|≤1.2°, we have

[0064] ω x =0;

[0065] ω yk′ =(β) yk -β yk0 )secβ xk ;

[0066] (4.2.3) When cos 2 β xk sin 2 β yk ≥1-r, and β yk Must satisfy ||β yk |-90°|>1.2° and |β yk When -270°|>1.2°, there is

[0067]

[0068] ω yk′ =(β) yk -β yk0 )secβ xk ;

[0069] Where, ω x For the medium frame X p2 The resultant rotational angular velocity of the shaft; ω yk′ For the outer frame Y p3 The resultant rotational angular velocity of the shaft.

[0070] In step (2), the relative rotation angles inside the four-axis inertial stabilized platform system are measured using the following method:

[0071] X in the outer frame p2 An angle sensor is mounted on the axis to measure the X-axis of the outer frame around the coordinate system of the middle frame. p2 The angle β of the shaft rotation xk ; in the inner frame Y p1An angle sensor is installed on the axis to measure the Y-axis of the middle frame around the inner frame's coordinate system. p1 The angle β of the shaft rotation yk ; in Taiwan Z p A sensor mounted on the axis measures the Z-axis coordinate of the inner frame around the body coordinate system of the stage. p The angle β of the shaft rotation zk .

[0072] In step (2), the rotation angle β yk The value range is -90 to 270°; rotation angle β zk β xk β yk′ The value range is -180 to 180°.

[0073] Figure 4 The dots in the diagram represent singularities indicating "frame locking" on the four-axis platform. (β) yk ,β xk ) = (90°, 0°), (90°, 180°), (90°, -180°), (270°, 0°), (270°, 180°), (270°, -180°), (-90°, 180°), (-90°, 0°), (-90°, -180°).

[0074] To illustrate the variable structure control method for the servo loop of the four-axis inertial platform provided by this invention, the schematic diagram is as follows: Figure 5 and Figure 6 As shown. Figure 5 This is a method described in the literature "Variable Structure Partition Control of a Quad-Axis Gyro Stabilized Platform, Tsinghua University Journal Vol.50, No.7, 2010", which is based on the inner frame angle β. yk and the angle β of the middle frame xk The intervals are partitioned using different decouplers, resulting in a total of 16 intervals and 4 types of controllers.

[0075] Figure 6 This invention is based on the inner frame angle β yk and the angle β of the middle frame xk The partitioning method uses different decouplers for each region, resulting in 10 regions (including 9 restricted areas with singularities and 1 non-singular region) and 3 types of controllers. The main purpose of setting up circular restricted areas at singularities is to avoid "frame locking".

[0076] Example:

[0077] Let β yk′ β xk β yk β zk The initial values ​​are 0°, 40°, 90°, and 0°, respectively, and the angular velocity of the platform base is... The servo circuit uses a minimum output energy decoupler.

[0078]

[0079]

[0080]

[0081]

[0082] The result of decoupling control is as follows Figure 7 and Figure 8 As shown. Among them, Figure 7 This refers to the area where the inner and middle frames are located when minimum output energy control is employed; Figure 8 This shows the change of the frame angle over time when minimum output energy control is used. It can be seen that at time 0.8 seconds, due to 1-cos... 2 β xk sin 2 β yk =0, calculate ω x and ω yk′ When the value is odd, it becomes impossible to continue controlling it.

[0083] Therefore, the method of this invention is used to solve the singular value problem. First, restricted areas are set near each singular value, with r = 0.3 and a restricted area radius of 33.2°, as shown below. Figure 6 As shown. The results of variable structure control using the present invention are as follows. Figure 9 and Figure 10 As shown. Among them, Figure 9 This refers to the region where the angles of the inner frame and the middle frame are located during the variable structure control of this invention; Figure 10 This illustrates the change in frame angle over time during variable structure control according to the present invention. It can be seen that the occurrence of singular values ​​is avoided.

[0084] The above embodiments can verify the correctness of the servo loop boundary switching variable structure control method of the present invention.

[0085] The contents not described in detail in this specification are common knowledge to those skilled in the art.

[0086] Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make possible changes and modifications to the technical solutions of the present invention by utilizing the methods and techniques disclosed above without departing from the spirit and scope of the present invention. Therefore, any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solutions of the present invention shall fall within the protection scope of the technical solutions of the present invention.

Claims

1. A method for servo loop boundary switching variable structure control of a four-axis inertial stabilization platform, characterized in that, include: Based on the angular velocity output by the gyroscope mounted on the platform, the position of the platform in the X direction is obtained. p Axis, Y p Axis and Z p angular velocity components on the axis , , ; Measuring the X-axis of the outer frame around the coordinate system of the middle frame p2 Angle of rotation of the shaft The Y-axis of the middle frame around the inner frame's body coordinate system p1 Angle of rotation of the shaft Z-axis of the inner frame around the body coordinate system p Angle of rotation of the shaft ; Setting the critical parameters of the variable structure r ; Based on the measurement and , , Determine the rotational angular velocity of the platform and the inner frame; Based on the measurement , , , and and critical parameters r Calculate the rotational angular velocities of the middle frame and the outer frame: when Sometimes, ； ； when ,and Must meet or Sometimes, ； ； when ,and Must meet and Sometimes, ； ； in, For the medium frame X p2 The resultant rotational angular velocity of the shaft; For the outer frame Y p3 The resultant rotational angular velocity of the shaft; The four-axis inertial stabilization platform has multiple singularities. A circular exclusion zone is used to eliminate these singularities to prevent frame lock-up in the control method. The conditions for singularities are as follows: .

2. The boundary switching variable structure control method according to claim 1, characterized in that, Based on the measurement and , , Calculate the rotational angular velocities of the platform and the inner frame: ； ； in, For Taiwan Z p The resultant rotational angular velocity of the shaft; For the inner frame Y p1 The resultant rotational angular velocity of the shaft.

3. The boundary switching variable structure control method according to claim 1, characterized in that, The relative rotation angles inside the four-axis inertial stabilized platform system were measured using the following method: X in the outer frame p3 An angle sensor is mounted on the axis to measure the X-axis of the outer frame around the coordinate system of the middle frame. p2 Angle of rotation of the shaft ; in the inner frame Y p1 An angle sensor is installed on the axis to measure the Y-axis of the middle frame around the inner frame's coordinate system. p1 Angle of rotation of the shaft ; in Taiwan Z p A sensor mounted on the axis measures the Z-axis coordinate of the inner frame around the body coordinate system of the stage. p Angle of rotation of the shaft .

4. The boundary switching variable structure control method according to claim 1, characterized in that, Rotation angle The value range is -90 to 270°; rotation angle , The value range is -180 to 180°.

5. The boundary switching variable structure control method according to any one of claims 1 to 4, characterized in that, The four-axis inertial stabilization platform consists of a base, an outer frame, a middle frame, an inner frame, and a platform body. The corresponding body coordinate systems are the base body coordinate system (X1Y1Z1) and the outer frame body coordinate system (X...). p3 Y p3 Z p3 , Medium frame body coordinate system X p2 Y p2 Z p2 The inner frame body coordinate system X p1 Y p1 Z p1 and the X coordinate system of the platform body p Y p Z p The origins of the five coordinate systems coincide, and: the Z-axis of the platform body coordinate system... p Z-axis and the coordinate system of the inner frame p1 The axes coincide, and the Y-axis of the body coordinate system of the middle frame is... p2 Y-axis and the coordinate system of the inner frame p1 The axes coincide, and the X coordinate of the outer frame body coordinate system is... p3 The X-axis of the axis and the body coordinate system of the middle frame p2 The axes coincide, the X1 axis of the base body coordinate system and the Y axis of the outer frame body coordinate system. p3 The axes coincide; wherein, the base is fixedly connected to the carrier, and when the stable platform undergoes internal relative rotation under the drive of the carrier, the base revolves around the Y-axis of the outer frame's body coordinate system. p3 The axis rotates, and the outer frame revolves around the X coordinate system of the middle frame. p2 The axis rotates, and the middle frame rotates around the Y-axis of the inner frame's body coordinate system. p1 The axis rotates, and the inner frame rotates around the Z-axis of the platform's coordinate system. p The shaft rotates.

6. The boundary switching variable structure control method according to claim 1, characterized in that, Singularities include ( , = (90°, 0°), (90°, 180°), (90°, -180°), (270°, 0°), (270°, 180°), (270°, -180°), (-90°, 180°), (-90°, 0°), (-90°, -180°).

Images