Incremental PID anti-saturation control method and system for fast-reflection mirrors for satellite laser communication

Abstract

This application provides an incremental PID anti-saturation control method and system for a satellite laser communication fast-reflection mirror. This application dynamically determines the state of the PID module based on the satellite's status. When the PID module is in an over-limit state, its output control quantity is reduced to zero, and the unexecuted PID module control quantity is latched. Then, a corresponding proportion of the unexecuted PID module control quantity is gradually released according to an increasingly amplified release coefficient α(k) until the normal output of the PID module control quantity is restored. This application, based on an FPGA-based PID controller hardware architecture, achieves a microsecond-level over-limit response of no more than 0.5 μs through a fully hardware-based, radiation-hardened PID anti-integral saturation scheme. Furthermore, it dynamically adapts to various operating conditions in space while effectively suppressing oscillations during the recovery phase. The laser alignment error fluctuation of this application is less than 5%.

Description

Technical Field

[0001] This application relates to the field of satellite laser communication technology, and more specifically to an incremental PID anti-saturation control method and system for a fast-reflecting mirror in satellite laser communication. Background Technology

[0002] Satellite communications utilize fast mirrors (FSMs) to achieve dynamic, sub-micro-radius control of the light beam direction, enabling wireless communication between transmitting and receiving stations using information carried by laser modulation. Fast mirrors require precise and rapid angular adjustments to guide light energy towards a small receiver on a satellite hundreds of kilometers away, facilitating information transmission in space.

[0003] However, the space environment is complex and ever-changing, and the PID control technology used in existing fast-reflecting mirrors often faces integral saturation problems, affecting the mirror's positioning and tracking, and thus impacting laser communication. To address this issue, existing technologies often employ software anti-saturation schemes such as integral separation, or some hardware-based fixed-threshold schemes. However, with software anti-saturation schemes, the interrupt response delay typically exceeds 100 μs, failing to meet inter-satellite communication requirements and potentially causing software state machine errors and poor PID output stability when exposed to space radiation. Hardware fixed-threshold schemes cannot dynamically adjust the threshold based on satellite operating conditions (such as orbital altitude and thermal deformation), and their method of directly resetting the integral value can cause fast-reflecting mirror jitter, leading to secondary communication loss. Furthermore, incremental PID control systems also face implicit saturation problems, such as control quantity stagnation caused by continuous unidirectional increments when the actuator is physically saturated, resulting in an inability to quickly recover. Summary of the Invention

[0004] This application addresses the shortcomings of existing technologies by providing a fully hardware-based, radiation-hardened PID anti-integral saturation scheme to solve the problems of synchronization loss and communication interruption caused by output exceeding limits in satellite laser communication. The specific technical solution adopted in this application is as follows.

[0005] First, to achieve the above objectives, an incremental PID anti-saturation control method for a fast-reflecting mirror in satellite laser communication is proposed. The steps include: dynamically determining whether the PID module is in an over-limit state based on the satellite status; when the PID module is in an over-limit state, resetting the control output of the PID module to zero and latching any unexecuted PID module control values; after the over-limit state is resolved, entering a dynamic reset state, and sequentially adjusting the release coefficient according to the current cycle. Gradually release a corresponding proportion of the unexecuted PID module control quantity until the release coefficient reaches 1, then enter the normal state and resume the normal output of the PID module control quantity; wherein, the release coefficient for any k-th cycle after the over-limit state is released is ,in, is the preset release rate coefficient, and k is the current output cycle of the PID module.

[0006] Optionally, the incremental PID anti-saturation control method for satellite laser communication fast-reflecting mirrors as described above includes the step of dynamically determining whether the PID module is in an over-limit state based on the satellite status, which includes: dynamically adjusting the threshold range based on the satellite's design limitations, satellite orbit data, and satellite energy status, and determining that the PID module is in an over-limit state when the control quantity output by the PID module exceeds or falls below the dynamically adjusted threshold range.

[0007] Optionally, the incremental PID anti-saturation control method for satellite laser communication fast-reflecting mirrors as described above, wherein the release rate coefficient The system is dynamically adjusted based on the satellite's vibration spectrum. ,in, This refers to the vibration frequency of the satellite or the motor inside the satellite.

[0008] Optionally, the incremental PID anti-saturation control method for satellite laser communication fast-reflecting mirrors as described above, wherein the latched, unexecuted PID module control quantity is denoted as... In the dynamic reset state, the PID module control quantity output in any k-th cycle is: Among them, the unexecuted PID module control quantities It is stored in a register using Hamming encoding.

[0009] Optionally, the incremental PID anti-saturation control method for satellite laser communication fast-reflection mirrors as described above further includes the following steps: updating and recording, at a preset period, whether the PID module is in a normal state, an over-limit state, or a dynamic reset state in several state machine replicas; and performing the following steps based on the state stored most frequently in the state machine replicas: when the PID module is in an over-limit state, resetting the control quantity output by the PID module to zero and latching the unexecuted PID module control quantity. When the PID module is in dynamic reset state, the current output cycle of the PID module is used sequentially. Calculate the corresponding release coefficient Gradually release the corresponding proportion of unexecuted PID module control inputs. When the PID module is in normal state, it outputs the control quantity of the PID module based on the laser offset.

[0010] To achieve the above objectives, this application also provides an incremental PID anti-saturation control system for a satellite laser communication fast-reflection mirror, comprising: an error calculation module for detecting laser offset and outputting a corresponding deviation; a PID module for outputting a control quantity based on the deviation under normal conditions; a threshold management module for dynamically adjusting a threshold based on the satellite status and determining whether the control quantity output by the PID module exceeds the limit based on the threshold; and an anti-integral saturation module that performs the following steps when the control quantity output by the PID module exceeds the limit: switching the PID module to an over-limit state, resetting the control quantity output by the PID module to zero in the over-limit state, and latching the unexecuted PID module control quantity; and switching the PID module to a dynamic reset state after releasing the over-limit state, in the dynamic reset state sequentially according to the release coefficient corresponding to the current cycle. Gradually release a corresponding proportion of the unexecuted PID module control quantity until the release coefficient reaches 1, at which point the PID module is switched to normal state, restoring the normal output of the PID module control quantity; wherein, in dynamic reset state, the release coefficient for any k-th cycle is... ,in, This is the preset release rate coefficient.

[0011] Optionally, the incremental PID anti-saturation control system for the satellite laser communication fast-reflecting mirror as described above further includes several registers, which are used to store latched, unexecuted PID module control quantities. The current state of the PID module; wherein the content to be stored is Hamming encoded before being stored in the register and Hamming decoded before being output.

[0012] Optionally, in the incremental PID anti-saturation control system of the satellite laser communication fast reflector as described above, at least three sets of registers are provided for storing the current state of the PID module, and each set of registers updates and stores the current state of the PID module at a frequency of 1 kHz.

[0013] Optionally, the incremental PID anti-saturation control system for the satellite laser communication fast-reflection mirror as described above further includes a state machine module, used to: trigger the system to execute the following steps based on the state stored in the register: when the PID module is in an over-limit state, reset the control quantity output by the PID module to zero and latch the unexecuted PID module control quantity. When the PID module is in dynamic reset state, it sequentially operates according to the current cycle. The corresponding release coefficient Gradually release a corresponding proportion of the unexecuted PID module control input. When the PID module is in normal state, it outputs the control quantity of the PID module based on the laser offset.

[0014] Optionally, in the incremental PID anti-saturation control system of the satellite laser communication fast-reflecting mirror as described above, the preset release rate coefficient... Based on the satellite's vibration spectrum Adjusted to: , where is the vibration frequency of the satellite or the motor in the satellite; the threshold used to determine whether the control quantity output by the PID module exceeds the limit is determined as follows: when the satellite voltage exceeds 24V, the upper limit of the threshold is set to 10V, and when the satellite voltage does not reach 24V, the upper limit of the threshold is set to 8V, or the upper limit of the threshold is determined according to the satellite's orbital altitude and temperature, and the lower limit of the threshold is determined according to the satellite's battery voltage and temperature.

[0015] Beneficial Effects: The incremental PID anti-saturation control method and system for satellite laser communication fast-reflection mirrors provided in this application can dynamically determine the state of the PID module based on the satellite status. When the PID module is in an over-limit state, its output control quantity is reduced to zero, and the unexecuted PID module control quantity is latched. Then, in each cycle, a corresponding proportion of the unexecuted PID module control quantity is released gradually according to an increasingly amplified release coefficient α(k) until the normal output of the PID module control quantity is restored. This application, based on an FPGA-based PID controller hardware architecture, achieves a microsecond-level over-limit response of no more than 0.5 μs through a fully hardware-based, radiation-hardened PID anti-integral saturation scheme. Furthermore, it dynamically adapts to various operating conditions in space while effectively suppressing oscillations during the recovery phase. The laser alignment error fluctuation of this application is less than 5%.

[0016] Other features and advantages of this application will be set forth in the following description, and will be apparent in part from the description, or may be learned by practicing this application. Attached Figure Description

[0017] The accompanying drawings are provided to further illustrate the present application and form part of the specification. Together with the embodiments of the present application, they serve to explain the present application but do not constitute a limitation thereof. In the drawings:

[0018] Figure 1 This is a schematic diagram of the control flow of the incremental PID anti-saturation control system for the satellite laser communication fast reflector of this application;

[0019] Figure 2 This is a schematic diagram of the system in this application;

[0020] Figure 3 This is a flowchart illustrating the dynamic determination method in this application;

[0021] Figure 4This is a block diagram illustrating the principle of the triple redundancy voting mechanism adopted in this application;

[0022] Figure 5 This is a block diagram illustrating the register protection mechanism employed in this application. Detailed Implementation

[0023] To make the objectives and technical solutions of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this application. All other embodiments obtained by those skilled in the art based on the described embodiments of this application without creative effort are within the scope of protection of this application.

[0024] Those skilled in the art will understand that, unless otherwise defined, all terms used herein (including technical and scientific terms) have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains. It should also be understood that terms such as those defined in general dictionaries should be understood to have the same meaning as in the context of the prior art, and should not be interpreted in an idealized or overly formal sense unless defined as herein.

[0025] The term "connection" as used in this application can mean a direct connection between components or an indirect connection between components through other components.

[0026] This invention belongs to the field of aerospace control technology, and provides a control system for high-precision, high-reliability alignment of fast mirrors (FSMs) particularly suitable for low-Earth orbit satellite inter-satellite laser communication, to overcome the following challenges faced in existing satellite laser communication:

[0027] Beam alignment accuracy requirement: ≤0.1 μrad (equivalent satellite platform vibration compensation accuracy);

[0028] Real-time requirements: Control cycle ≤ 10 μs, delay ≤ 1 μs;

[0029] Space environment constraints: Single event flip (SEU), thermal deformation, and energy limitations lead to dynamic saturation of actuators.

[0030] Unlike existing technologies that add fixed coefficients to the integral term, this application provides a dynamic mechanism to gradually release frozen increments to address the integral saturation problem. This overcomes the issues of poor quantification and environmental adaptability associated with adding fixed coefficients. Furthermore, unlike some existing technologies that simply remove the integral term when the error is small without addressing output overshoot, this application uses a state machine-driven mechanism to release coefficients. The dynamically adjusted anti-integral saturation mechanism can solve the problem of control over-limit under extreme space conditions through exponential smooth release, ensure the stability of the laser link, and limit the instability of the connection between the front and back ends as much as possible.

[0031] Figure 1 The incremental PID anti-saturation control system for a satellite laser communication fast reflector provided in this application is implemented based on a very large-scale integrated circuit FPGA and includes:

[0032] The error calculation module is used to detect the laser offset and output the corresponding deviation.

[0033] The PID module uses an incremental algorithm to output control input based on the deviation in normal state (S0).

[0034] The threshold management module dynamically adjusts the threshold according to the satellite status, updates the output limit values ​​Umax and Umin, and determines whether the control quantity output by the PID module exceeds the limit based on the threshold.

[0035] The anti-integral saturation module performs the following steps when the control output of the PID module exceeds the limit:

[0036] Switch the PID module to the over-limit state (S1). In the over-limit state, the control quantity output by the PID module is set to zero, and the unexecuted PID module control quantity is latched. This freezes the actual output increment when the PID output exceeds the limit, and uses the latched unexecuted increment as the calculation basis for dynamic release on a cycle-by-cycle basis.

[0037] After removing the over-limit state according to the above steps, switch the PID module to dynamic reset state (S2). In dynamic reset state, proceed according to the current cycle number. Determine the corresponding release coefficient Thus, in each control cycle, according to the release coefficient The corresponding proportion of unexecuted PID module control quantities are released gradually until the release coefficient reaches 1, at which point the PID module is switched to normal state, restoring the normal output of the PID module control quantities.

[0038] Therefore, this application can gradually correct the output increment by dynamically calculating the release coefficient. During the gradual release correction process, the frozen, unexecuted PID module control quantity remains constant until... At that time, the frozen amount is completely released and the system returns to normal control mode. This application, through the aforementioned dynamic release process, can easily utilize a preset release rate coefficient. Control the release speed to ensure that the frozen, unexecuted PID module control quantities in this system can fully return to the normal incremental mode after the release is terminated, without residual compensation.

[0039] This approach enables this application to:

[0040] (a) Through a pioneering incremental release mechanism: utilizing an exponential function Smoothly release the frozen increment to completely eliminate step disturbance;

[0041] (b) Utilizing a full-cycle dynamic update method: The release amount is refreshed in each control cycle (in typical application environments, the frequency can reach once every 10μs), and the system accurately judges whether it has smoothly exited the saturation state, thereby achieving accurate identification and rapid response to integral saturation.

[0042] (c) By means of As a quantitative condition for termination of release, in the release coefficient When the value reaches 1, exit the anti-saturation state promptly to ensure continuous control;

[0043] (d) Based on the above implementation, this application can further improve the release rate. It is configured to dynamically adjust based on the satellite's vibration spectrum, thereby achieving in-depth optimization for space scenarios and suppressing the impact of satellite platform jitter.

[0044] In practical implementation, the system of this application can dynamically adjust the threshold range according to the satellite's design limitations, satellite orbit data and satellite energy status. Thus, when the control quantity output by the PID module exceeds or falls below the dynamically adjusted threshold range, it is determined that the PID module is in an over-limit state.

[0045] For example, according to Figure 3 The method shown involves setting the upper limit of the threshold to 10V when the satellite's voltage exceeds 24V, and setting the upper limit of the threshold to 8V when the satellite's voltage does not reach 24V. Alternatively, the upper limit of the threshold can be determined based on the satellite's orbital altitude and temperature, and the lower limit of the threshold can be determined based on the satellite's battery voltage and temperature.

[0046] Furthermore, this application may also, on this basis, adopt... Figure 4 The TMR (Triple Mode Redundancy) technology shown provides single-event flip protection for the entire state machine; EDAC encoding and decoding technology is used to protect all critical registers from single-event flips, and the register data is refreshed at a frequency of 1KHz.

[0047] Specifically, this application can be made through Figure 2 As shown, based on the incremental PID anti-saturation control system of the satellite laser communication fast-reflection mirror described above, several registers are set up to store:

[0048] Latched unexecuted PID module control values And the current state of the PID module; and through Figure 5 The method involves Hamming encoding the content to be stored before storing it into the register and Hamming decoding the content before outputting it to avoid ion flipping affecting the control of the system.

[0049] The system includes at least three sets of registers for storing the current state of the PID module. Each set of registers is updated at a frequency of 1 kHz in each control cycle and stores the current state of the PID module. This allows the state machine module to trigger the system to execute the following control strategy based on the state stored in the register:

[0050] When the PID module is in state S0 (normal state): it normally outputs the control quantity of the PID module based on the laser offset. ;

[0051] When the PID module is in state S1 (over-limit state): that is, after detecting that the output exceeds the limit, the output increment is reset to 0. Simultaneously, it latches the unexecuted increment and stores it in the register. After the output limit is cleared, it transitions to state S2.

[0052] When the PID module is in state S2 (dynamic reset state): Calculate the release coefficient. According to the current cycle The corresponding release coefficient Gradually release a corresponding proportion of the unexecuted PID module control input. ; and, in When transitioning to state S0, normal output occurs. .

[0053] In the above control mechanism, This represents the normal output increment of the PID when it is in a normal, non-over-limit state. This is the increment of the actual output of the PID during the dynamic release phase of this application; During the release phase, the PID output increment is frozen; release rate coefficient. Based on the satellite's vibration spectrum, the dynamic adjustment and optimization are as follows: ,in, This refers to the vibration frequency of the satellite or the motor inside the satellite. Based on the satellite vibration spectrum: high-frequency vibrations are assigned a smaller value (0.1), and low-frequency vibrations are assigned a larger value (0.3). During the control process, the release period... The control cycle is consistent with that of the PID controller. The number of dynamic release cycles, k_max, required for complete release using this application can be obtained as follows:

[0054] set up , The dynamic reset process is shown in the table below:

[0055] exist (k→∞, engineering implementation takes) When the value is ≥0.999, the dynamic reset is complete. At this point, the cache can be cleared. The register is then switched, and the state machine is switched to the normal output mode of S0. Simultaneously, the cycle counter is reset. Reset to 0.

[0056] Table 1 Dynamic Reset Process:

[0057]

[0058] In summary, this application can achieve a gradual release mechanism through an exponential function, and through the dual protection mechanism of EDAC+TMR, and using a general FPGA reconstruction and refresh protection mechanism, reduce the single-event upset rate to 1e^-9 errors / bitday. That is, the probability of a single-event upset error occurring once per day for each memory bit in the device is controlled to within one in a billion. The hardware encoding and decoding latency is compressed to within 0.1μs without affecting the 10μs PID control cycle.

[0059] Compared to traditional solutions that address implicit integral accumulation by output clamping or directly clearing the increment, this application can latch the current increment and gradually release it to avoid control drift and ensure that the satellite fast mirror quickly exits saturation. This avoids the control stagnation caused by existing technologies and the problem of unexecuted increments being discarded, which leads to the control being stuck at the saturation point when there is a continuous same-direction error.

[0060] Compared to the traditional method in existing technologies that eliminates recovery-stage oscillations by releasing the freeze increment in a single step after saturation release, this application decomposes step disturbances into micro-adjustments through exponential smooth release (e.g., release over 16 cycles when β=0.2). The standard deviation of beam jitter is reduced from 0.38 μrad to 0.04 μrad (a reduction of 89%). Therefore, this application effectively solves the problem of step jitter (>0.5 μrad) in fast-reflecting mirrors, leading to secondary beam misalignment, faced by existing technologies.

[0061] Furthermore, compared to existing technologies that rely on software to determine exceedance and release, this application utilizes a fully hardware state machine for exceedance determination, reducing latency to ≤0.5 μs and limiting the entire release cycle to updates every 10 μs. Additionally, this application employs the CORDIC algorithm within the FPGA to calculate the release coefficient. It can complete exponential calculations in a single cycle, effectively overcoming the real-time requirements of microsecond-level control cycles in inter-satellite communication under traditional methods, where software latency exceeds 50 μs.

[0062] The above are merely embodiments of this application, and their descriptions are quite specific and detailed, but they should not be construed as limiting the scope of this patent application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application.

Claims

1. An incremental PID anti-saturation control method for a fast-reflecting mirror for satellite laser communication, characterized in that the steps are as follows: include: The system dynamically determines whether the PID module is in an over-limit state based on the satellite status. When the PID module is in an over-limit state, the control quantity output by the PID module is reset to zero, and the unexecuted PID module control quantity is latched. After the over-limit state is released, it enters the dynamic reset state, and releases according to the release coefficient corresponding to the current cycle. Gradually release the corresponding proportion of the unexecuted PID module control quantity until the release coefficient reaches 1, then enter the normal state and restore the normal output of the PID module control quantity. Wherein, the release coefficient for any k-th period after the overlimit state is lifted is ,in, is the preset release rate coefficient, and k is the current output cycle of the PID module.

2. The incremental PID anti-saturation control method for a fast-reflecting mirror for satellite laser communication as described in claim 1, characterized in that, The steps for dynamically determining whether the PID module is in an over-limit state based on satellite status include: The threshold range is dynamically adjusted based on the satellite's design limitations, orbital data, and energy status. When the control output of the PID module exceeds or falls below the dynamically adjusted threshold range, the PID module is determined to be in an over-limit state.

3. The incremental PID anti-saturation control method for a fast-reflecting mirror for satellite laser communication as described in claim 1, characterized in that, The release rate coefficient The system is dynamically adjusted based on the satellite's vibration spectrum. ,in, This refers to the vibration frequency of the satellite or the motor inside the satellite.

4. The incremental PID anti-saturation control method for a fast-reflecting mirror for satellite laser communication as described in claim 1, characterized in that, Let the latched, unexecuted PID module control quantity be... , In the dynamic reset state, the PID module control quantity output in any k-th cycle is: ; Among them, the unexecuted PID module control quantities It is stored in a register using Hamming encoding.

5. The incremental PID anti-saturation control method for a fast-reflecting mirror for satellite laser communication as described in claim 4, characterized in that, It also includes the following steps: In several copies of the state machine, the following are updated and recorded at preset intervals: whether the PID module is in a normal state, an over-limit state, or a dynamic reset state. Perform the following steps based on the state that is most frequently stored in the state machine replica: When the PID module is in an out-of-limit state, the control output of the PID module is reset to zero, and the unexecuted PID module control output is latched. ; When the PID module is in dynamic reset state, it is sequentially based on the current output cycle of the PID module. Calculate the corresponding release coefficient Gradually release the corresponding proportion of unexecuted PID module control inputs. , When the PID module is in normal mode, it outputs the control quantity of the PID module based on the laser offset.

6. An incremental PID anti-saturation control system for a fast-reflecting mirror for satellite laser communication, characterized in that, include: The error calculation module is used to detect the laser offset and output the corresponding deviation. The PID module is used to output control input based on the deviation under normal conditions. The threshold management module dynamically adjusts the threshold according to the satellite status and determines whether the control quantity output by the PID module exceeds the limit based on the threshold. The anti-integral saturation module performs the following steps when the control output of the PID module exceeds the limit: Switch the PID module to the over-limit state. In the over-limit state, the control quantity output by the PID module is set to zero, and the unexecuted PID module control quantity is latched. After the over-limit state is lifted, the PID module is switched to dynamic reset state. In dynamic reset state, the release coefficient corresponding to the current cycle is used sequentially. Gradually release the corresponding proportion of the unexecuted PID module control quantity until the release coefficient reaches 1, then switch the PID module to the normal state and restore the normal output of the PID module control quantity. In the dynamic reset state, the release coefficient for any k-th cycle is: ,in, This is the preset release rate coefficient.

7. The incremental PID anti-saturation control system for a satellite laser communication fast-reflecting mirror as described in claim 6, characterized in that, It also includes several registers, which are used to store: Latched unexecuted PID module control values And the current state of the PID module; The content to be stored is Hamming encoded before being stored in the register and Hamming decoded before being output.

8. The incremental PID anti-saturation control system for a satellite laser communication fast-reflecting mirror as described in claim 6, characterized in that, There are at least three sets of registers used to store the current state of the PID module. Each set of registers is updated and stores the current state of the PID module at a frequency of 1 kHz.

9. The incremental PID anti-saturation control system for a satellite laser communication fast-reflecting mirror as described in claim 6, characterized in that, It also includes a state machine module, used for: The system is triggered to execute the following steps based on the state that is most frequently stored in the register: When the PID module is in an out-of-limit state, the control output of the PID module is reset to zero, and the unexecuted PID module control output is latched. ; When the PID module is in dynamic reset state, it sequentially operates according to the current cycle. The corresponding release coefficient Gradually release a corresponding proportion of the unexecuted PID module control input. , When the PID module is in normal mode, it outputs the control quantity of the PID module based on the laser offset.

10. The incremental PID anti-saturation control system for a satellite laser communication fast-reflecting mirror as described in claim 6, characterized in that, The preset release rate coefficient Based on the satellite's vibration spectrum Adjusted to: , where is the vibration frequency of the satellite or the motor in the satellite; The threshold used to determine whether the control output of the PID module exceeds the limit is determined as follows: When the satellite's voltage exceeds 24V, the upper limit of the threshold is set to 10V; when the satellite's voltage does not reach 24V, the upper limit of the threshold is set to 8V. Alternatively, the upper limit of the threshold can be determined based on the satellite's orbital altitude and temperature, and the lower limit of the threshold can be determined based on the satellite's battery voltage and temperature.

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