A control method for offshore parallel stable platform based on EtherCAT bus

Abstract

The present invention relates to the field of stable platform control technology, and in particular to a control method for an offshore parallel stable platform based on an EtherCAT bus. By first using the trajectory planning function provided by the function library, when the position and speed errors between the tracking curve and the actual curve meet the requirements, the real-time tracking mode with the Kalman filter algorithm as the core is switched to improve the dynamic tracking capability of the offshore parallel stable platform. Through actual testing of the offshore parallel stable platform, the tracking error of the same 10-degree, 0.5Hz curve using the controller function module is about 0.5 degrees; after the real-time tracking algorithm is implemented, the tracking error is reduced to about 0.06 degrees, thereby improving the tracking accuracy of the platform. It not only utilizes the high reliability of mature industrial controllers, greatly shortens the R&D cycle and reduces R&D costs, but also realizes low tracking error control of the parallel stable platform.

Description

Technical Field

[0001] The present invention relates to the field of stable platform control technology, and in particular to a control method for an offshore parallel stable platform based on an EtherCAT bus. Background Art

[0002] As my country's national strength continues to grow, its maritime activities are increasing. When ships sail at sea, they are inevitably rocked by waves, severely impacting the detection and tracking of targets at sea or in the air. The parallel structure's stable platform offers high load-bearing rigidity, low power consumption, and compact construction, making it ideal for small-scale maritime applications.

[0003] There are two main types of controllers. One is a card-based controller based on high-speed buses such as CPCI, which is dedicated to certain specific fields. The core processor is generally a DSP chip. This type of controller is more flexible and can be optimized according to actual working conditions to achieve accurate dynamic tracking. However, the disadvantage is that the 15DSP operation speed is low, and it is difficult to implement complex algorithms. The development cycle and cost of self-stabilizing control applied to parallel mechanisms are very high. The other type is a mature industrial control controller based on EtherCAT.

[0004] The processing core of the industrial controller of the bus is generally the CPU of companies such as Intel. This type of control has strong computing power and is widely used in the field of industrial control. The built-in library function is simple and easy to use, but

[0005] However, its disadvantages are its lack of flexibility, inability to optimize based on specific operating conditions, and inability to guarantee 20° dynamic tracking accuracy. Because offshore parallel stabilized platforms are complex to control and extremely sensitive to dynamic tracking errors, and operate in harsh environments, adopting a self-developed controller results in a long development cycle and high R&D costs. Therefore, while adopting mature industrial controllers, it is necessary to develop self-developed algorithms to improve the system's tracking accuracy. Summary of the Invention

[0006] (1) Technical problems to be solved

[0007] 25 The embodiment of the present invention provides a control method for an offshore parallel stabilized platform based on the EtherCAT bus, which solves the technical problem that the built-in function library of a mature industrial controller based on the EtherCAT bus cannot meet the dynamic error requirements of the offshore parallel stabilized platform.

[0008] (2) Technical solution

[0009] An embodiment of the present invention proposes a control method for an offshore parallel stable platform 30 based on an EtherCAT bus, and the stabilization operation includes the following steps: S1, the inertial navigation sends the posture information of the tracked carrier to the controller; S2, the controller uses the MC_MoveAbsolute module to perform traction work in a stationary state according to the carrier posture information; S3, the controller determines whether the switching condition is met; S4, when the carrier posture is consistent with the current posture of the stable platform, the controller switches to a tracking algorithm using a Kalman filter; S5, when the carrier posture is inconsistent with the current posture of the stable platform, the controller continues to use the MC_MoveAbsolute module to perform traction work.

[0010] Furthermore, the traction work is specifically as follows: using the MC_MoveAbsolute module to drive the imaginary axis to start moving according to the inertial navigation input position, collecting the motion trajectory of the imaginary axis in real time and outputting it to the real axis, driving the actual movement of the platform, and gradually increasing the speed and acceleration of the MC_MoveAbsolute module.

[0011] Furthermore, after the speed and acceleration of the MC_MoveAbsolute module reach the maximum speed and maximum acceleration allowed by the platform, it starts to determine whether the switching condition is met.

[0012] Furthermore, if the speed difference between the carrier attitude and the current stable platform attitude is within a certain range, the carrier attitude information output by the inertial navigation is directly driven to move the platform after being processed by the tracking algorithm in the next servo cycle.

[0013] Furthermore, the Kalman filter tracking algorithm includes processing the inertial navigation output signal containing noise.

[0014] Furthermore, the controller needs to automatically return the platform to zero position before receiving the start stabilization instruction.

[0015] Furthermore, the controller needs to automatically return the platform to the lowest position after receiving the end stabilization instruction.

[0016] Furthermore, a self-checking program is also included before stable operation, and the platform is self-checked through the self-checking program.

[0017] (3) Beneficial effects

[0018] In summary, the present invention improves the dynamic tracking capability of the offshore parallel-stabilized platform by first using the trajectory planning function provided by the function library. Once the position and velocity errors between the tracking curve and the actual curve meet the requirements, the real-time tracking mode based on the Kalman filter algorithm is switched to. Actual testing of the offshore parallel-stabilized platform shows that the tracking error of the controller function module is approximately 0.5 degrees when tracking a 10-degree, 0.5Hz curve. After implementing the real-time tracking algorithm, the tracking error is reduced to approximately 0.06 degrees, improving the platform's tracking accuracy. This not only leverages the high reliability of mature industrial controllers, significantly shortening the R&D cycle and reducing R&D costs, but also achieves low tracking error control for the parallel-stabilized platform. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for use in Example 5 of the present invention. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0020] Figure 1 The invention discloses a workflow of a control method for an offshore parallel stable platform based on EtherCAT bus.

[0021] Figure 2 The present invention is a stable working flow chart of a control method of an offshore parallel stable platform based on EtherCAT bus. DETAILED DESCRIPTION

[0022] The following detailed description of the embodiments of the present invention is provided in conjunction with the accompanying drawings and examples. The following detailed description of the 15 embodiments and the accompanying drawings are intended to illustrate the principles of the present invention, but are not intended to limit the scope of the present invention. That is, the present invention is not limited to the described embodiments, and any modifications, substitutions, and improvements without departing from the spirit of the present invention are contemplated.

[0023] It should be noted that, in the absence of conflict, the embodiments and features of the embodiments in this application can be combined with each other. The present application will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0024] 20Please refer to Figures 1 and 2 The embodiment of the present invention proposes a control method for an offshore parallel stabilization platform based on an EtherCAT bus, wherein the stabilization operation includes the following steps:

[0025] S1, the inertial navigation sends the tracked carrier attitude information to the controller;

[0026] S2, the controller uses the MC_MoveAbsolute module to perform traction work in a stationary state according to the carrier posture information;

[0027] 25S3, the controller determines whether the switching condition is met;

[0028] S4, when the carrier posture is consistent with the posture of the current stable platform, the controller switches to the tracking algorithm using Kalman filtering;

[0029] S5: When the carrier posture is inconsistent with the current posture of the stable platform, the controller continues to use the MC_MoveAbsolute module to perform traction.

[0030] 30 By first using the built-in trajectory planning function in the function library and issuing instructions, when the position and velocity errors between the tracking curve and the actual curve meet the requirements, the real-time tracking mode based on the Kalman filter algorithm is switched to improve the dynamic tracking capability of the offshore parallel-stabilized platform. In actual testing of an offshore parallel-stabilized platform, tracking a 10-degree, 0.5Hz curve, the tracking error using the controller function module was approximately 0.5 degrees. After implementing the real-time tracking algorithm, the tracking error was reduced to approximately 0.06 degrees, improving the platform's tracking accuracy. This system leverages the high reliability of mature industrial controllers, significantly shortening the R&D cycle and reducing R&D costs, while achieving low tracking error control for the parallel-stabilized platform.

[0031] In some embodiments, the traction work is specifically the traction work performed by the function module of TwinCAT3 in a static state. The core is to use the MC_MoveAbsolute module to drive the virtual axis to start moving according to the inertial navigation input position, collect the motion trajectory of the virtual axis in real time and output it to the real axis, drive the actual movement of the platform, and gradually increase the speed and acceleration of the MC_MoveAbsolute module. In this way, the platform can achieve a relatively smooth tracking of the carrier shaking. When the speed and acceleration reach the maximum speed and maximum acceleration allowed by the platform, it begins to determine whether the switching conditions are met.

[0032] In some embodiments, the judgment condition for switching the tracking algorithm is specifically to determine whether the posture of the tracked carrier is consistent with the posture of the current stable platform, that is, the speed difference between the carrier posture and the posture of the current stable platform is within a certain range. Then, in the next servo cycle, the carrier posture information output by the inertial navigation will be processed by the tracking algorithm and directly drive the platform movement.

[0033] In some embodiments, the Kalman filter tracking algorithm includes processing the noisy inertial navigation system output signal. This method can be used to obtain an estimate of the true attitude with minimal error, on average. Kalman filtering further improves tracking accuracy when the attitude information output by the inertial navigation system contains discontinuities and interference.

[0034] In some embodiments, the controller is required to automatically return the platform to a zero position before receiving a start stabilization command.

[0035] In some embodiments, the controller is required to automatically return the platform to the lowest position after receiving the end stabilization instruction.

[0036] In some embodiments, a self-test program is included before stabilization operation, and the platform is self-tested through the self-test program. The self-test program first determines whether there is a fault, and if so, determines whether it can be eliminated by itself. If it can be eliminated, the fault is cleared and the system is restarted, and the self-test program is re-entered. If it cannot be eliminated by itself, the stabilization platform fault information is reported to the staff for inspection and resolution.

[0037] It should be noted that the various embodiments in this specification are described in a progressive manner. References to the same or similar parts between the various embodiments are sufficient. Each embodiment focuses on the differences from the other embodiments. The present invention is not limited to the specific steps described above and shown in the figures. Furthermore, for the sake of brevity, detailed descriptions of known methods and techniques are omitted here.

[0038] The foregoing is merely an embodiment of the present application and is not intended to limit the present application. Various modifications and variations are possible for those skilled in the art without departing from the scope of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present application shall be included within the scope of the claims of the present application.

Claims

1. A control method for an offshore parallel stabilized platform based on EtherCAT bus, characterized in that: Stabilization work includes the following steps: S1, the inertial navigation sends the tracked carrier attitude information to the controller; S2, the controller uses the MC_MoveAbsolute module to perform traction work in a stationary state according to the carrier posture information; S3, the controller determines whether the switching conditions are met; S4, when the carrier posture is consistent with the posture of the current stable platform, the controller switches to the tracking algorithm using Kalman filtering; S5: When the carrier posture is inconsistent with the current posture of the stable platform, the controller continues to use the MC_MoveAbsolute module to perform traction.

2. The control method of an offshore parallel stabilized platform based on EtherCAT bus according to claim 1, characterized in that: The traction work is specifically as follows: using the MC_MoveAbsolute module to drive the imaginary axis to start moving according to the inertial navigation input position, collecting the motion trajectory of the imaginary axis in real time and outputting it to the real axis to drive the actual movement of the platform, and gradually increasing the speed and acceleration of the MC_MoveAbsolute module.

3. The control method of an offshore parallel stabilized platform based on EtherCAT bus according to claim 2, characterized in that: After the speed and acceleration of the MC_MoveAbsolute module reach the maximum speed and maximum acceleration allowed by the platform, it starts to determine whether the switching conditions are met.

4. The control method of an offshore parallel stabilized platform based on EtherCAT bus according to claim 1, characterized in that: If the speed difference between the carrier attitude and the current stable platform attitude is within a certain range, the carrier attitude information output by the inertial navigation will be processed by the tracking algorithm in the next servo cycle to directly drive the platform movement.

5. The control method of an offshore parallel stabilized platform based on EtherCAT bus according to claim 1, characterized in that: The Kalman filter tracking algorithm includes processing the inertial navigation output signal containing noise.

6. The control method of an offshore parallel stabilized platform based on EtherCAT bus according to claim 1, characterized in that: The controller needs to automatically return the platform to zero position before receiving the start stabilization instruction.

7. The control method of an offshore parallel stabilized platform based on EtherCAT bus according to claim 1, characterized in that: The controller needs to automatically return the platform to the lowest position after receiving the end stabilization instruction.

8. The control method of an offshore parallel stabilized platform based on EtherCAT bus according to claim 1, characterized in that: Before stable operation, a self-checking program is also included, through which the platform is self-checked.

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