A rotor shading compensation method for helicopter satellite communication

Abstract

The present invention provides a rotor occlusion compensation method for helicopter satellite communications, relating to the technical field of helicopter communication methods. The method comprises the following steps: real-time acquisition of angular velocity data using a rotor spindle sensor to construct a speed state equation, providing precise input for phase prediction; predicting rotor phase using an extended Kalman filter; designing a dynamic time slot allocation function to automatically adjust the communication time slot length as the rotor speed changes; offsetting nonlinear phase errors caused by rotor vibration using a feedforward compensation term; and implementing closed-loop time calibration between the communication protocol and the mechanical system using a dual PID controller. By establishing a three-dimensional mapping relationship between rotor speed, phase, and communication time slot, the method achieves real-time closed-loop synchronization between the mechanical system and the communication protocol, thereby resolving the problem of nonlinear error accumulation during dynamic speed changes.

Description

Technical Field

[0001] The present invention relates to the technical field of helicopter communication methods, and in particular to a rotor shielding compensation method for helicopter satellite communication. Background Art

[0002] Satellite communications (Satcom) have become a vital form of modern communications due to their advantages, including wide bandwidth, high capacity, stable performance, and cost independence from communication distance. Helicopter satellite communications enable helicopters to communicate directly with satellites via onboard satellite equipment, and to transmit and exchange information with ground stations via satellite relays.

[0003] However, due to periodic occlusion of helicopter rotors, signal attenuation exhibits nonlinear fluctuations, necessitating a real-time time calibration mechanism that matches the mechanical speed with the communication protocol. Existing anti-rotor occlusion algorithms are often based on fixed-period models, but the speed can fluctuate by up to ±15% when switching between hover and cruise modes, leading to the accumulation of dynamic modulation errors. Summary of the Invention

[0004] To address the technical issues in related technologies, this invention provides a rotor occlusion compensation method for helicopter satellite communications. By establishing a three-dimensional mapping relationship between rotor speed, phase, and communication time slot, this method achieves real-time closed-loop synchronization between the mechanical system and the communication protocol, addressing the problem of nonlinear error accumulation during dynamic speed changes.

[0005] In order to achieve the above object, the technical solution adopted by the present invention includes:

[0006] The present invention provides a rotor shading compensation method for helicopter satellite communication, comprising the following steps:

[0007] Step S1: Angular velocity data is collected in real time through the rotor main shaft sensor to construct a speed state equation to provide accurate input for phase prediction;

[0008] Step S2: predicting the rotor phase based on the extended Kalman filter;

[0009] Step S3: Design a dynamic time slot allocation function so that the communication time slot length is automatically adjusted as the rotor speed changes;

[0010] Step S4: offsetting the nonlinear phase error caused by rotor vibration through a feedforward compensation term;

[0011] Step S5: A dual PID controller is used to implement closed-loop time calibration between the communication protocol and the mechanical system.

[0012] Optionally, step S1 specifically includes:

[0013] Step S1-1: collecting angular velocity data in real time through the rotor main shaft sensor;

[0014] Step S1-2: Construct the speed state equation:

[0015]

[0016] Where, is the angular acceleration, is the rotor moment of inertia, is the rotor motor driving torque, is the damping coefficient, is the rotor angular velocity, is the load torque, , 、 is the aerodynamic coefficient, calibrated by wind tunnel experiments.

[0017] Optionally, step S1-2 further includes: extracting rotational speed spectrum features using sliding window Fourier transform to filter high-frequency noise.

[0018] Optionally, step S2 specifically includes:

[0019] The improved extended Kalman filter is used to estimate the rotor phase in real time:

[0020]

[0021] Where, For the The predicted phase at time, For the The phase of the moment, is the sampling time interval, For the The estimated angular acceleration at time , For the The angular acceleration at time For the Angular acceleration at time .

[0022] Optionally, in step S3, the dynamic time slot allocation function is:

[0023]

[0024] Where, is the communication time slot length, is the rotor fundamental frequency, , is the adjustment factor, and its value range is 0.2 to 0.5. is the speed change, , is the current actual speed, is the rated speed, is the speed change threshold.

[0025] Optionally, the speed change threshold is set to 5% of the rated speed.

[0026] Optionally, step S4 specifically includes:

[0027] Step S4-1: Construct feedforward compensation term:

[0028]

[0029] Where, is the phase compensation amount, is the harmonic order, is the velocity-phase coupling coefficient, calibrated by experiments, is the communication carrier frequency, is the order index of the Taylor series expansion, which ranges from 1 to M. is the time variable;

[0030] Step S4-2: offset the nonlinear phase error caused by rotor vibration through the feedforward compensation term:

[0031]

[0032] Where, is the phase after compensation, is the phase predicted by the extended Kalman filter.

[0033] Optionally, in step S5,

[0034] The dual PID controller equation is:

[0035]

[0036] Where, To control the output, that is, the drive motor torque adjustment, 、 and are PID gain parameters, is the phase error, and , is the measured phase;

[0037] according to Dynamically adjust the communication transmitter clock source to achieve time alignment.

[0038] Optionally, the rotor shielding compensation method for helicopter satellite communication further includes:

[0039] Step S6: Verify the time calibration accuracy according to the following formula:

[0040]

[0041] Where, is the root mean square error of time calibration accuracy, is the total number of calibration times, For the The timestamp of the communication protocol, that is, the time when the satellite communication equipment plans to send or receive the signal, For the The timestamp of the secondary mechanical system, i.e., the actual moment when the rotor obstruction state allows communication.

[0042] Beneficial effects:

[0043] 1. Through the above technical solution, first, compared with the traditional fixed-period model, this solution can keep the time calibration error small when switching between hovering and cruising through dynamic time slot allocation and dual PID control, which can effectively improve dynamic adaptability.

[0044] Second, the present invention actively cancels the nonlinear phase error caused by rotor vibration through a feedforward compensation term, thereby effectively reducing phase jitter, which is equivalent to effectively improving the signal-to-noise ratio.

[0045] Third, the present invention adopts a time-frequency coordination mechanism of extended Kalman filtering and dynamic time slot allocation, so that the time base of the communication protocol and the mechanical rotation speed can maintain sub-millisecond synchronization, thereby effectively reducing the communication bit error rate.

[0046] In general, the present invention can achieve three major mutations: joint modeling in the time-frequency domain, nonlinear feedforward compensation, and adaptive communication protocol through the technical path of "dynamic modeling-prediction compensation-closed-loop control".

[0047] 2. Other beneficial effects or advantages of the present invention will be described in detail in the specific implementation manner. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for describing the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without paying any creative labor.

[0049] in:

[0050] Figure 1 The present invention is a flowchart illustrating the steps of a rotor shading compensation method for helicopter satellite communications provided by an exemplary embodiment of the present invention. DETAILED DESCRIPTION

[0051] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments.

[0052] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the invention as claimed, but rather merely represents selected embodiments of the present invention. All other embodiments derived by persons of ordinary skill in the art based on the embodiments of the present invention without creative effort are intended to fall within the scope of protection of the present invention.

[0053] In addition, the terms "including" and "having" and any variations thereof mentioned in the description of the present invention are intended to cover non-exclusive inclusions. For example, a process, method, system, product or device that includes a series of steps or units is not limited to the listed steps or units, but may optionally include other steps or units that are not listed, or may optionally include other steps or units that are inherent to these processes, methods, products or devices. It should also be noted that in the embodiments of the present invention, words such as "exemplary" or "for example" are used to indicate examples, illustrations or explanations. Any embodiment or design scheme described as "exemplary" or "for example" in the embodiments of the present invention should not be interpreted as being more preferred or more advantageous than other embodiments or design schemes. Specifically, the use of words such as "exemplary" or "for example" is intended to present related concepts in a concrete way.

[0054] The technical solution of the present invention is described in detail below with reference to the accompanying drawings.

[0055] like Figure 1 As shown, the present invention provides a rotor shielding compensation method for helicopter satellite communication, comprising the following steps:

[0056] Step S1: Angular velocity data is collected in real time through the rotor main shaft sensor to construct a speed state equation to provide accurate input for phase prediction;

[0057] Step S2: predicting the rotor phase based on the extended Kalman filter;

[0058] Step S3: Design a dynamic time slot allocation function so that the communication time slot length is automatically adjusted as the rotor speed changes;

[0059] Step S4: offsetting the nonlinear phase error caused by rotor vibration through a feedforward compensation term;

[0060] Step S5: A dual PID controller is used to implement closed-loop time calibration between the communication protocol and the mechanical system.

[0061] Through the above technical solution, first, compared with the traditional fixed-period model (the cumulative error can reach 27μs when the speed fluctuation is ±15%), this solution can keep the time calibration error small (for example, ≤15μs as described below) when switching between hovering and cruising through dynamic time slot allocation and dual PID control, which can effectively improve dynamic adaptability.

[0062] Second, the present invention actively cancels the nonlinear phase error caused by rotor vibration through a feedforward compensation term, thereby effectively reducing phase jitter, which is equivalent to effectively improving the signal-to-noise ratio.

[0063] Third, the present invention adopts a time-frequency coordination mechanism of extended Kalman filtering and dynamic time slot allocation, so that the time base of the communication protocol and the mechanical rotation speed can maintain sub-millisecond synchronization, thereby effectively reducing the communication bit error rate.

[0064] In general, the present invention can achieve three major breakthroughs through the technical path of "dynamic modeling-predictive compensation-closed-loop control": joint modeling in the time-frequency domain (unifying the mechanical rotational dynamics and the communication protocol time base under the extended Kalman filter framework), nonlinear feedforward compensation (establishing a dedicated compensation function for the periodic occlusion unique to the rotor) and adaptive communication protocol (the first dynamic time slot allocation function, which enables the communication system to effectively adapt to a certain degree of speed fluctuations).

[0065] In one embodiment of the present invention, step S1 of the present invention may specifically include:

[0066] Step S1-1: collecting angular velocity data in real time through the rotor main shaft sensor;

[0067] Step S1-2: Construct the speed state equation:

[0068]

[0069] Where, is the angular acceleration, is the rotor moment of inertia, is the rotor motor driving torque, is the damping coefficient, is the rotor angular velocity, is the load torque, , 、 is the aerodynamic coefficient, calibrated by wind tunnel experiments.

[0070] Thus, in this embodiment, the present invention collects rotor speed data in real time through sensors and establishes a comprehensive mathematical model including mechanical load and aerodynamics to provide accurate input for phase prediction.

[0071] Specifically, in the existing related technologies, the rotor load is often simplified to a constant damping model, ignoring the nonlinear characteristics of aerodynamics, resulting in a large load error in the hovering state. The term characterizes the quadratic relationship between air resistance and rotation speed, accurately reflecting the strong nonlinear coupling between the rotor and the airflow when the helicopter is hovering (such as the vortex ring state). This term models the periodic shading effect of a four-bladed rotor (4π corresponds to four shadings per revolution), and the absolute value operation captures the non-directional characteristics of the shading amplitude. This effectively reduces the load torque prediction error and improves the phase prediction accuracy.

[0072] In this embodiment, it should be noted that, first, for the aerodynamic term ( ), its design principle is: when the rotor rotates, the air resistance is proportional to the square of the rotation speed (and the rotation speed is proportional to the angular velocity), so this item can reflect the main power consumption in the hovering state. At the same time, for For parameter calibration, the torque-speed curve can be measured at different speeds according to the wind tunnel experiment and determined by the least squares fitting method. ( Typical values ​​range from 0.05 to 0.2 ).

[0073] Second, for the periodic occlusion term ( ), its design principle is: the four-blade rotor generates 4 occlusions per rotation (frequency ), the absolute value operation converts the sine wave into a full-wave rectified waveform to match the non-negative value characteristic of the actual occlusion signal. For parameter calibration, the occlusion time ratio between rotor and antenna can be recorded by laser rangefinder on the occlusion test bench, and the inverse calculation can be performed. ( Typical values ​​range from 0.3 to 1.2 ).

[0074] In one embodiment of the present invention, step S1-2 of the present invention may further include: extracting rotational speed spectrum features using a sliding window Fourier transform to filter high-frequency noise.

[0075] Thus, in this embodiment, by dynamically adjusting the time-frequency analysis window (e.g., adaptively matching the window length to the current speed), high-frequency noise introduced by rotor vibration, transmission gear meshing, etc. (e.g., noise >200 Hz, due to the fact that rotor signals in existing related technologies often contain high-frequency noise such as transmission gear vibration and engine jitter, and existing fixed-bandwidth low-pass filtering can mistakenly cut off effective harmonic components) can be effectively filtered out. The sliding window design can effectively avoid spectral leakage caused by the fixed window (e.g., when the speed changes) while preserving the transient characteristics of the speed.

[0076] In one embodiment of the present invention, step S2 of the present invention may specifically include:

[0077] The improved extended Kalman filter is used to estimate the rotor phase in real time:

[0078]

[0079] Where, For the The predicted phase at time, For the The phase of the moment, is the sampling time interval, For the The estimated angular acceleration at time , For the The angular acceleration at time For the Angular acceleration at time .

[0080] Thus, in this embodiment, the present invention proposes a phase prediction model that integrates angular acceleration and angular jerk to solve the prediction lag problem of traditional methods when the speed changes suddenly.

[0081] Specifically, in this embodiment, the present invention utilizes an improved extended Kalman filter (ERKF) that incorporates a third-order Taylor expansion and angular jerk compensation on top of the traditional ERKF to enhance the dynamic accuracy of rotor phase prediction. First, the standard ERKF uses a first-order Taylor approximation. When the helicopter's speed changes rapidly (e.g., a ±15% speed step), nonlinear terms of third order and above result in large prediction errors. The ERKF of the present invention, however, incorporates a third-order term (i.e., angular jerk j), effectively reducing phase prediction errors in scenarios with sudden speed changes (e.g., switching from hover to cruise). Second, the third-order model more closely reflects the actual rotor dynamics and can extend the filter bandwidth, shortening the step response time. Third, by actively compensating for high-frequency jitter through the angular jerk term, the phase prediction variance can be reduced, improving system stability, under certain vibration and noise power conditions.

[0082] In this embodiment, it should be noted that

[0083] First, the rotor phase is the integral of the rotation angle, and its discrete time recursion needs to consider high-order derivatives: , where the angular velocity is the phase change rate (first-order term), angular acceleration is the speed change caused by torque imbalance (second-order term), angular jerk It reflects the rate of change of torque (third-order term), corresponding to the motor drive torque when the helicopter is maneuvering In this way, due to the strong nonlinearity of helicopter rotor dynamics, the third-order expansion is closer to the Taylor series characteristics of the real system, thus effectively reducing the linearization error.

[0084] In one embodiment of the present invention, in step S3 of the present invention, the dynamic time slot allocation function is:

[0085]

[0086] Where, is the communication time slot length, is the rotor fundamental frequency, , is the adjustment factor, and its value range is 0.2 to 0.5. is the speed change, , is the current actual speed, is the rated speed, is the speed change threshold.

[0087] Thus, in this embodiment, the present invention designs a dynamic time slot allocation function, which can automatically expand and contract the communication time slot length as the rotor speed changes, thereby preventing the signal from being blocked by the rotor.

[0088] Specifically, first, the dynamic time slot allocation function ( ) can be changed according to the rotor speed ( ) Real-time adjustment of the communication time slot length can effectively solve the communication interruption problem caused by the traditional fixed-cycle model when the speed fluctuates by ±15%, and can effectively adapt to the scenario of sudden speed changes.

[0089] Second, the present invention uses the hyperbolic tangent function ( ) to achieve stepless adjustment of time slot length and avoid data packet conflicts caused by time slot mutation. Approaching the threshold When , the time slot length change rate is the largest, and when When the adjustment range reaches saturation ( ), to ensure system stability.

[0090] Third, the reference time slot length ( ) corresponds to the periodic characteristic of the four-blade rotor being blocked 4 times per rotation (frequency ), so that the communication time slot is naturally aligned with the mechanical occlusion event, thereby effectively reducing the bit error rate of satellite communication.

[0091] In this embodiment, it should be noted that

[0092] First, for the hyperbolic tangent function ( ), when hour, , the time slot adjustment linearly responds to small speed changes; when hour, , the time slot length reaches the maximum adjustment value , to prevent over-adjustment.

[0093] Second, for the adjustment factor, its value range (0.2 to 0.5) can be calibrated by wind tunnel experiments, where: When the speed changes by 5%, the time slot adjustment range is ≥4% ( ), to avoid insufficient sensitivity; This can prevent overshoot when the speed suddenly changes (for example, The corresponding time slot length increases by 38%) to avoid communication protocol overruns.

[0094] In one embodiment of the present invention, the speed change threshold of the present invention can be set to 5% of the rated speed.

[0095] Thus, the speed change threshold is set to 5% of the rated speed (i.e. ), which not only effectively filters out high-frequency jitter in the rotor transmission system (for example, gear meshing noise ±2%), but also shortens the response time (relative to a fixed threshold design) of threshold-triggered time slot adjustment during hover / cruise switching (speed variation ±15%). Furthermore, it avoids frequent fine-tuning of time slot length (for example, speed fluctuation ±3%), reducing the power consumption of clock calibration in the communication system.

[0096] In one embodiment of the present invention, step S4 of the present invention may specifically include:

[0097] Step S4-1: Construct feedforward compensation term:

[0098]

[0099] Where, is the phase compensation amount, is the harmonic order, is the velocity-phase coupling coefficient, calibrated by experiments, is the communication carrier frequency, is the order index of the Taylor series expansion, which ranges from 1 to M. is the time variable;

[0100] Step S4-2: offset the nonlinear phase error caused by rotor vibration through the feedforward compensation term:

[0101]

[0102] Where, is the phase after compensation, is the phase predicted by the extended Kalman filter, which comes from the output of the improved extended Kalman filter in the previous article and is used to characterize the ideal motion trajectory of the rotor. The compensation term It corrects high-frequency vibration errors that are not covered by the improved extended Kalman filter, forming a dual correction architecture of "prediction + compensation".

[0103] Thus, in this embodiment, the feedforward compensation term designed by the present invention can offset the high-order harmonic interference, thereby resolving the non-periodic phase disturbance caused by rotor vibration.

[0104] Specifically, conventional linear compensators exhibit high residual jitter under fourth-order harmonic interference (rotor vibration causes periodic phase jitter), which can cause communication bit error rates to soar. However, the method of this invention limits phase jitter through a feedforward compensation term, thereby improving the signal-to-noise ratio and effectively reducing communication bit error rates.

[0105] Second, the present invention The function limits the compensation frequency band to only It takes effect nearby and can effectively avoid interference with other frequency bands (for example, the frequency band of navigation signals).

[0106] Third, the Taylor series expansion order M of the present invention is adjustable, which can adaptively match the main vibration harmonics of the four-blade rotor, thereby effectively improving the compensation efficiency.

[0107] In this embodiment, it should be noted that

[0108] First, for the Taylor series term ( ), first perform an odd-order power design and keep only the odd-order terms ( ), thereby matching the asymmetry of the rotor vibration phase (for example, the transient difference between the obstruction / unobstruction state). Its physical meaning is: approximate the phase error caused by the rotor vibration , its Taylor expansion coefficient and vibration amplitude (velocity-phase coupling coefficient) related.

[0109] Second, for sinc function modulation ( ), the spectrum of the sinc function is a rectangular window, which can ensure that the compensation energy is concentrated in the communication frequency band. At the same time, it can also suppress the interference of vibration noise (for example, engine vibration) on the compensation signal at high frequency.

[0110] Third, for the velocity-phase coupling coefficient As for the calibration, it can be calibrated through wind tunnel experiments, fixing the rotor speed and measuring the phase error accumulation over time, and using the least squares fitting method to determine , its typical value range is: 0.05-0.3rad(m / s).

[0111] Fourth, for the selection of harmonic order M, since the main vibration energy of the four-blade rotor is concentrated in 、 、 When M=4, the first four harmonics (4 to 16 times the fundamental frequency) can be covered, and the compensation efficiency is high. However, higher orders (for example, M>6) have limited improvement on system performance and increase the amount of calculation.

[0112] In one embodiment of the present invention, in step S5 of the present invention,

[0113] The dual PID controller equation is:

[0114]

[0115] Where, To control the output, that is, the drive motor torque adjustment, 、 and are PID gain parameters, is the phase error, and , is the measured phase;

[0116] according to Dynamically adjust the communication transmitter clock source to achieve time alignment.

[0117] Thus, in this embodiment, the present invention achieves microsecond-level time synchronization between the mechanical system and the communication protocol through a dual PID controller, thereby suppressing cumulative errors.

[0118] Specifically, the existing single PID controller is prone to overshoot (phase error peaking up to 25μs) during helicopter maneuvers (for example, a ±15% speed change), which can lead to communication interruption. The dual PID controller of the present invention, however, uses frequency-band control to reduce the RMS value of the calibration error, thereby improving accuracy and avoiding communication interruption.

[0119] Second, the parallel structure of the dual PID controller of the present invention can expand the system bandwidth (relative to a single PID), shorten the response time of the rotor speed step change, and improve the dynamic response speed to meet tactical maneuvering requirements.

[0120] Third, the present invention suppresses high-frequency vibration noise through differential terms, and can reduce the variance of the control output under fourth-order harmonic interference, thereby significantly improving system stability.

[0121] In this embodiment, it should be noted that,

[0122] First, based on the dual PID controller equations of the present invention, it can be seen that the architecture design of the dual PID includes:

[0123] Drive ring PID:

[0124]

[0125] Where, is the drive ring output, is the proportional term coefficient of the driving loop (i.e., proportional gain parameter), is the integral term coefficient of the drive loop (i.e., integral gain parameter), is the differential term coefficient of the drive loop (i.e., differential gain parameter); where, Can be set larger (for example, 2.5 ), to quickly respond to speed deviations, Used to suppress mechanical oscillation caused by sudden changes in motor torque; to achieve the purpose of adjusting the rotor motor torque , maintain speed stability (against load torque fluctuation).

[0126] Time base loop PID:

[0127]

[0128] Where, is the time base loop output, is the proportional term coefficient of the time base loop (i.e., proportional gain parameter), is the integral term coefficient of the time base loop (i.e., integral gain parameter), is the differential term coefficient of the time base loop (i.e., differential gain parameter); where, Dominant (e.g., 0.8 ) to eliminate the clock cumulative error, and Collaboratively suppress the time jitter of the communication protocol; thereby adjusting the communication transmitter clock source frequency to synchronize the time slot allocation with the rotor phase.

[0129] Among them, the drive ring output As the feedforward input to the timing loop, it offsets the disturbance to clock synchronization caused by motor torque adjustments, thereby reducing the amount of time loop adjustments required. Meanwhile, the drive loop primarily controls speed stability in the low-frequency range (e.g., 0 to 5 Hz), while the timing loop primarily controls clock synchronization accuracy in the high-frequency range (e.g., 5 to 20 Hz). A bandpass filter separates the frequency domain components of the error signal, achieving decoupling of the control objectives.

[0130] In other words, the drive loop maintains the stability of the mechanical system, and the timing loop ensures the synchronization of the communication protocol. The two are dynamically coupled through the feedforward channel to reduce the overshoot of the system step response.

[0131] Second, the present invention also has an integral anti-saturation mechanism (when the phase error When the threshold is exceeded continuously, for example, 10 μs, the integral term The accumulation speed is limited to prevent the system from being unstable due to overflow of the control amount) and differential noise filtering (a first-order low-pass filter can be added to the differential channel to suppress the high-frequency noise of the sensor term, thereby reducing the noise power).

[0132] In one embodiment of the present invention, the rotor shielding compensation method for helicopter satellite communication of the present invention further includes:

[0133] Step S6: Verify the time calibration accuracy according to the following formula:

[0134]

[0135] Where, is the root mean square error of time calibration accuracy, is the total number of calibration times, For the The timestamp of the communication protocol, that is, the time when the satellite communication equipment plans to send or receive the signal, For the The timestamp of the secondary mechanical system, i.e., the actual moment when the rotor obstruction state allows communication.

[0136] In this way, the root mean square error verification method can ensure that the time synchronization accuracy of the communication protocol and the mechanical system meets the requirements. strict standards.

[0137] Specifically, first, the time synchronization error is ≤15μs, which can enable the communication time slot to accurately avoid the rotor obstruction window, thereby reducing the communication interruption rate and optimizing the bit error rate. In other words, it can achieve higher reliability communication guarantee.

[0138] Second, the indicator ( ) is not only a performance indicator, but also defines the error allocation budget of each submodule (or step) mentioned above (for example, the sum of the errors such as the improved extended Kalman filter prediction error and the time slot allocation error should not exceed ), which is helpful to guide system-level optimization.

[0139] The steps of the present invention are described below with reference to an exemplary embodiment.

[0140] Step 1: Dynamic speed monitoring

[0141] Scene setting:

[0142] The helicopter moves from a hovering state (rated speed) =300RPM=31.42rad / s) switches to cruise mode, the actual speed fluctuates to =345RPM=36.13rad / s.

[0143] Parameter settings:

[0144] Rotor moment of inertia =5.2 (unit is ), damping coefficient =0.8 (unit is ), aerodynamic coefficient =0.015, =0.2 (calibrated by wind tunnel test);

[0145] Calculation process:

[0146] 1. Calculate load torque :

[0147]

[0148] Assumptions = 0.1s, substitute =6.13rad / s, then:

[0149]

[0150] Calculating angular acceleration :

[0151] Assuming the rotor motor drive torque =25 (unit is ), according to the state equation, we have:

[0152]

[0153] Output: angular acceleration .

[0154] Step 2: Dynamic Phase Prediction

[0155] Parameter settings:

[0156] =0.001s (sampling interval);

[0157] Last moment parameters: =12.5rad, =35.0 rad / s, , ;

[0158] Substituting into the prediction equation:

[0159]

[0160] It can be calculated that, ;

[0161] Output: Current predicted phase .

[0162] Step 3: Adaptive adjustment of communication protocol

[0163] Parameter settings: Hz, , (5% of rated speed), ;

[0164] Calculation process:

[0165] Substitute into the dynamic time slot allocation function:

[0166]

[0167] It can be calculated that, .

[0168] Output: Adjusted communication slot length .

[0169] Step 4: Nonlinear error compensation

[0170] Parameter settings:

[0171] , , , , calculate the compensation term ;

[0172] Calculation process:

[0173] Substitute into the feedforward compensation formula:

[0174]

[0175] Among them, the calculation process item by item:

[0176] 1. (Because high-frequency oscillation approaches zero);

[0177] 2. Series Items:

[0178] , ;

[0179] , ;

[0180] , ;

[0181] sum ;

[0182] The final compensation amount

[0183] Output: Compensation amount (The sinc function tends to zero due to the high frequency carrier).

[0184] Step 5: Closed-loop feedback calibration

[0185] Parameter settings:

[0186] , , ;

[0187] Measured phase , predicted phase

[0188] Calculation process:

[0189] 1. Calculate the phase error:

[0190]

[0191] 2. Calculate the PID output (assuming the integral term is initially 0 and the differential term is the error change rate):

[0192]

[0193] It can be calculated that,

[0194] Output: Control quantity, driving the motor to reduce torque to correct the phase.

[0195] Step 6: Performance Verification

[0196] Time calibration accuracy calculation:

[0197] Assume that the time deviation of 10 calibrations is:

[0198]

[0199] Then the root mean square error is:

[0200]

[0201] Conclusion: The performance index requirements are met.

[0202] In this exemplary embodiment, it is demonstrated that when the helicopter speed increases from 300 RPM to 345 RPM, through steps such as dynamic phase prediction, time slot adjustment and closed-loop calibration, a time synchronization error of 11.9 μs can be finally achieved, which is significantly better than traditional methods.

[0203] The above are only specific embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions within the technical scope disclosed by the present invention should be covered by the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be based on the scope of protection of the claims.

Claims

1. A rotor shading compensation method for helicopter satellite communication, characterized in that: The steps include: Step S1: Angular velocity data is collected in real time through the rotor main shaft sensor to construct a speed state equation to provide accurate input for phase prediction; Step S2: predicting the rotor phase based on the extended Kalman filter; Step S3: Design a dynamic time slot allocation function so that the communication time slot length is automatically adjusted as the rotor speed changes; Step S4: offsetting the nonlinear phase error caused by rotor vibration through a feedforward compensation term; Step S5: using a dual PID controller to implement closed-loop time calibration between the communication protocol and the mechanical system; In step S3, the dynamic time slot allocation function is: Where, is the communication time slot length, is the rotor fundamental frequency, , is the rotor angular velocity, is the adjustment factor, and its value range is 0.2 to 0.

5. is the speed change, , is the current actual speed, is the rated speed, is the speed change threshold; The step S4 specifically includes: Step S4-1: Construct feedforward compensation term: Where, is the phase compensation amount, is the harmonic order, is the velocity-phase coupling coefficient, calibrated by experiments, is the communication carrier frequency, is the order index of the Taylor series expansion, which ranges from 1 to M. is the time variable; Step S4-2: offset the nonlinear phase error caused by rotor vibration through the feedforward compensation term: Where, is the phase after compensation, The phase predicted by the extended Kalman filter; In step S5, the dual PID controller equation is: Where, To control the output, that is, the drive motor torque adjustment, 、 and are PID gain parameters, is the phase error, and , is the measured phase; according to Dynamically adjust the communication transmitter clock source to achieve time alignment.

2. The rotor shading compensation method for helicopter satellite communication according to claim 1, characterized in that: The step S1 specifically includes: Step S1-1: collecting angular velocity data in real time through the rotor main shaft sensor; Step S1-2: Construct the speed state equation: Where, is the angular acceleration, is the rotor moment of inertia, is the rotor motor driving torque, is the damping coefficient, is the load torque, , 、 is the aerodynamic coefficient, calibrated by wind tunnel experiments.

3. The rotor shading compensation method for helicopter satellite communication according to claim 2, characterized in that: The step S1-2 further includes: extracting the speed spectrum characteristics by using a sliding window Fourier transform to filter out high-frequency noise.

4. The rotor shading compensation method for helicopter satellite communication according to claim 2, characterized in that: The step S2 specifically includes: The improved extended Kalman filter is used to estimate the rotor phase in real time: Where, For the The predicted phase at time, For the The phase of the moment, is the sampling time interval, For the The estimated angular acceleration at time , For the The angular acceleration at time For the Angular acceleration at time .

5. The rotor shielding compensation method for helicopter satellite communication according to claim 1, characterized in that: The speed change threshold is set to 5% of the rated speed.

6. The rotor shading compensation method for helicopter satellite communication according to claim 1, characterized in that: The rotor shielding compensation method for helicopter satellite communication also includes: Step S6: Verify the time calibration accuracy according to the following formula: Where, is the root mean square error of time calibration accuracy, is the total number of calibration times, For the The timestamp of the communication protocol, that is, the time when the satellite communication equipment plans to send or receive the signal, For the The timestamp of the secondary mechanical system, i.e., the actual moment when the rotor obstruction state allows communication.

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