Helicopter body vibration active control method under time-varying vibration load excitation

Abstract

The invention discloses a helicopter body vibration active control method under time-varying vibration load excitation, and aims to solve the problems of poor environment tracking performance, reduced control effect and the like of helicopter vibration active control under large-range time-varying rotor vibration load. And a fluctuation harmonic control algorithm for reconstructing a fluctuation harmonic primary function by identifying an excitation response harmonic coefficient is provided, so that the aim of efficiently controlling the vibration of the machine body under the condition of large-range time variation of the vibration load of the rotor wing is fulfilled. The method has an efficient vibration environment real-time tracking capability, and can realize the control effects of high efficiency, high adaptability and high vibration environment tracking performance when the vibration load is subjected to large-range time varying.

Description

Technical Field

[0001] This invention belongs to the field of helicopter vibration control technology, specifically a method for active control of helicopter body vibration under time-varying vibration load excitation. Background Technology

[0002] Due to the harmonic characteristics of helicopter airframe vibration, traditional active vibration control for helicopters typically employs frequency domain control algorithms based on harmonic harmonic vibration (HHC). HHC algorithms rely on Fourier transform calculations, requiring long control correction time intervals and exhibiting control input time lag. Furthermore, they are only suitable for suppressing steady-state harmonic vibrations of the helicopter airframe. In reality, helicopters are subjected to various disturbances during flight, and their airframe vibrations are not ideal steady-state harmonic vibrations. When the helicopter's flight state changes, the rotor excitation load undergoes significant time-varying variations, leading to large-scale time-varying airframe vibrations and reducing the effectiveness of active vibration control.

[0003] The harmonic synchronous identification and correction time-domain algorithm identifies and corrects the harmonic coefficients of the control input in real time by recognizing the harmonic coefficients of the vibration response, thus eliminating the dependence of the traditional HHC algorithm on Fourier transform and achieving real-time correction of the control input. Furthermore, the filtered x-minimum average quadratic (Fx-LMS) control algorithm also achieves real-time updates of the control input by filtering the reference signal through a secondary channel. However, the control input correction of such algorithms relies on the steady-state harmonic basis function or steady-state reference signal. When the excitation parameters vary significantly over a wide range, the correction speed is too slow, the vibration environment tracking is insufficient, and the control effect is poor. Summary of the Invention

[0004] Purpose of the invention: In order to improve the control effect of helicopter body vibration under a wide range of time-varying rotor excitation load, this invention proposes an active control method for helicopter body vibration under time-varying vibration load excitation.

[0005] Technical Solution: This invention proposes an active control method for helicopter fuselage vibration under time-varying vibration load excitation, specifically including the following steps:

[0006] S1: System initialization, initializing the harmonic basis function z(n) and the wave harmonic basis function according to the helicopter rotor speed. Initialize the control harmonic order The frequency response function T, and the harmonic coefficients corresponding to the control input and control error;

[0007] S2: Calculate the control input signal based on the current control input harmonic coefficient, and input the signal to the actuator to drive the helicopter to generate an actuation response at the control target. The response is superimposed with the excitation response signal generated by the rotor load at the control target at the current moment to generate the control error response of the control target at the current moment. The sensor installed on the corresponding control target collects the control error response signal on the control target in real time, thereby obtaining the control error response signal at the current moment.

[0008] S3: Based on the control error response signal obtained in S2 at the current moment, the minimum mean square error method is used to identify the control error response harmonic coefficients in real time based on the harmonic basis function at the current moment, and the excitation response harmonic coefficients are calculated.

[0009] S4: Based on the harmonic basis function at the current moment and the excitation response harmonic coefficients obtained in S3, calculate the harmonic fluctuation factor at the current moment, construct the fluctuation harmonic basis function, and identify the fluctuation harmonic coefficients of the control error response.

[0010] S5: Based on the harmonic coefficients of the fluctuation control error response signal described in S4 and the fluctuation harmonic basis function, calculate the control input harmonic coefficients at the next moment, and then proceed to S2.

[0011] Furthermore, in step S1, the basis function of the i-th order wave harmonic is:

[0012]

[0013] in, , Let i be the frequency of the i-th harmonic. Let be the i-th harmonic oscillation factor.

[0014] Furthermore, step S4 specifically includes:

[0015] S41: The formula for constructing the basis function of the i-th order wave harmonic is:

[0016]

[0017] in, , Let i be the frequency of the i-th harmonic. Let be the i-th harmonic fluctuation factor, and n be the sampling time.

[0018] The calculation method is as follows:

[0019]

[0020] in, The number of samples for the excitation response is used to reduce the fluctuation error of the harmonic basis function caused by the harmonic coefficient error of a single excitation response. Let be the i-th harmonic coefficient of the k-th excitation response, and K be the number of excitation responses.

[0021] S42: Based on the i-th order wave harmonic basis function constructed in S41 and the control error response at the current moment, the LMS algorithm is used to identify the wave harmonic coefficients of the control error response signal.

[0022] Furthermore, in step S5, the steepest descent method is used to correct the fluctuation harmonic coefficient of the control input signal in real time.

[0023] Beneficial effects:

[0024] (1) This invention realizes the tracking of the vibration load characteristics of the frequency response during the vibration control of the helicopter body, thus avoiding the problem of reduced control effect caused by the time-varying vibration load;

[0025] (2) The present invention can quickly correct the control input to the theoretical optimal value under linear, sinusoidal and mixed time-varying states of vibration load amplitude, and achieve excellent control effect. Attached Figure Description

[0026] Figure 1 This is a system block diagram of the present invention;

[0027] Figure 2 shows the control effect of the body's measuring point response under sinusoidal wave harmonic load;

[0028] Figure 3 shows the control effect of the body's measuring point response under mixed wave harmonic load. Detailed Implementation

[0029] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0030] like Figure 1 The illustrated embodiment provides an active control algorithm for wave harmonic control of helicopter fuselage vibration under time-varying load excitation, specifically:

[0031] S1: System initialization, initializing the harmonic basis function z(n) and the wave harmonic basis function according to the helicopter rotor speed. Initialize the control harmonic order The frequency response function T, and the harmonic coefficients corresponding to the control input and control error;

[0032] S2: Calculate the control input signal based on the current control input harmonic coefficient, and input the signal to the actuator to drive the helicopter to generate an actuation response at the control target. The response is superimposed with the excitation response signal generated by the rotor load at the control target at the current moment to generate the control error response of the control target at the current moment. The sensor installed on the corresponding control target collects the control error response signal on the control target in real time, thereby obtaining the control error response signal at the current moment.

[0033] S3: Based on the control error response signal obtained in S2 at the current moment, the minimum mean square error method is used to identify the control error response harmonic coefficients in real time based on the harmonic basis function at the current moment, and the excitation response harmonic coefficients are calculated.

[0034] S4: Based on the harmonic basis function at the current moment and the excitation response harmonic coefficients obtained in S3, calculate the harmonic fluctuation factor at the current moment, construct the fluctuation harmonic basis function, and identify the fluctuation harmonic coefficients of the control error response.

[0035] S5: Based on the harmonic coefficients of the fluctuation control error response signal described in S4 and the fluctuation harmonic basis function, calculate the control input harmonic coefficients at the next moment, and then proceed to S2.

[0036] In this embodiment, S1 specifically involves: determining the harmonic order to be controlled based on the frequency domain characteristics of the helicopter's initial rotor pass frequency and response. Generate the i-th harmonic basis function:

[0037] (1)

[0038] in, Sampling time.

[0039] Initialize the i-th harmonic fluctuation factor Initialize the i-th order wave harmonic basis function:

[0040] (2)

[0041] In this embodiment, S2 specifically involves: obtaining the harmonic coefficient vector of the control signal input to the m-th actuator based on the harmonic coefficient of the control signal currently input to the actuator. And calculate the time-domain control signal input to the m-th actuator. :

[0042] (3)

[0043] In this embodiment, S3 specifically refers to: based on the current control error response. Harmonic basis functions and control error response harmonic coefficient Identify the harmonic coefficients of the control error response at the next moment:

[0044] (4)

[0045] Control input harmonic coefficients based on the current moment Control error response harmonic coefficient and control system frequency response function matrix Calculate the harmonic coefficients of the excitation response at the current moment:

[0046] (5)

[0047] In this embodiment, S4 specifically refers to:

[0048] Step A: Calculate the harmonic fluctuation factor at the current moment based on the historical values ​​of the excitation response harmonic coefficients. The basis function of the i-th wave harmonic is:

[0049] (6)

[0050] in, The number of samples for the excitation response is used to reduce the fluctuation error of the harmonic basis function caused by the harmonic coefficient error of a single excitation response. Let be the i-th harmonic coefficient of the k-th excitation response, and K be the number of excitation responses.

[0051] Based on the harmonic fluctuation factor and harmonic basis function at the current moment, construct the fluctuation harmonic basis function at the current moment:

[0052] (7)

[0053] Step B: Based on the wave harmonic basis function constructed in Step A, the control error response at the current moment, and the wave harmonic coefficients of the control error response, the LMS algorithm is used to identify the wave harmonic coefficients of the control error response signal.

[0054] (8)

[0055] In this embodiment, S5 specifically involves: calculating the wave harmonic coefficients of the control input at the next time step using the LMS algorithm based on the harmonic coefficients of the wave control error response signal identified in S4 and the constructed wave harmonic basis function.

[0056] (9)

[0057] in, Set the harmonic correction step size. Obtain the fluctuation harmonic coefficients of the actuator control input, and return to S2.

[0058] Figure 2 shows the control effect of the helicopter body's measuring point response under sinusoidal harmonic load. It illustrates the control effect of the proposed control method and the traditional high-order harmonic control algorithm on the mean square value of the helicopter body's measuring point response when the rotor vibration load amplitude fluctuation ratio is 50% and the fluctuation frequency is 0.5Hz. Figures 2(a) and (b) show the mean square values ​​of the helicopter body's measuring point response when the rotor vibration load amplitude fluctuation ratio is 50% and the fluctuation frequency is 0.5Hz, respectively, using the proposed control method and the traditional high-order harmonic control algorithm. Due to the long control input delay, the high-order harmonic control algorithm cannot track the load fluctuation, thus always exhibiting amplitude error and phase delay compared to the optimal control, resulting in continuous large fluctuations in the converged body response. In contrast, the proposed control method has the ability to track the time-varying characteristics of the vibration load, effectively correcting the control input, and achieving a vibration level suppression effect of over 93% after convergence.

[0059] Figure 3 shows the control effect of the airframe measuring point response under mixed time-varying harmonic loads. It illustrates the control effect of the mean square value of the helicopter airframe measuring point response when the rotor vibration load amplitude fluctuation ratio is 50%, the fluctuation frequency is 0.5Hz, and it decreases by 90% in 30 seconds, using the proposed control method and the traditional high-order harmonic control algorithm, respectively. Figures 3(a) and (b) show the mean square values ​​of the helicopter airframe measuring point response when the rotor vibration load amplitude fluctuation ratio is 50%, the fluctuation frequency is 0.5Hz, and it decreases by 90% in 30 seconds, using the proposed control method and the traditional high-order harmonic control algorithm, respectively. Under the control of the high-order harmonic control algorithm, the airframe vibration response fluctuates continuously and significantly. The proposed control method, however, decays to a quasi-steady state after 3 seconds at the start of control, with a very low fluctuation amplitude, indicating that the proposed method still has strong active vibration control capability and effect under mixed time-varying load excitation.

[0060] The embodiments of the present invention have been described in detail above with reference to the accompanying drawings. However, the present invention is not limited to the above embodiments. Within the scope of knowledge possessed by those skilled in the art, various changes can be made without departing from the spirit of the present invention.

Claims

1. A method for active control of helicopter fuselage vibration under time-varying vibration load excitation, characterized in that, Specifically, the steps include the following: S1: System initialization, initializing the harmonic basis function z(n) and the wave harmonic basis function according to the helicopter rotor speed. Initialize the control harmonic order The frequency response function T, and the harmonic coefficients corresponding to the control input and control error; S2: Calculate the control input signal based on the current control input harmonic coefficient, and input the control input signal to the actuator to drive the helicopter to generate an actuation response at the control target. The response is superimposed with the excitation response signal generated by the rotor load at the control target at the current moment to generate the control error response of the control target at the current moment. The sensor installed on the corresponding control target collects the control error response signal on the control target in real time to obtain the control error response signal at the current moment. S3: Based on the control error response signal obtained in S2 at the current moment, the minimum mean square error method is used to identify the control error response harmonic coefficients in real time based on the harmonic basis function at the current moment, and the excitation response harmonic coefficients are calculated. S4: Based on the harmonic basis function at the current moment and the excitation response harmonic coefficients obtained in S3, calculate the harmonic fluctuation factor at the current moment, construct the fluctuation harmonic basis function, and identify the fluctuation harmonic coefficients of the control error response. S5: Based on the harmonic coefficients of the fluctuation control error response signal described in S4 and the fluctuation harmonic basis function, calculate the control input harmonic coefficients at the next moment, and then proceed to S2.

2. The active control algorithm for helicopter fuselage vibration under time-varying load excitation and wave harmonic control according to claim 1, characterized in that, In step S1, the i-th order wave harmonic basis function in the wave harmonic basis function is: ； in, , Let i be the frequency of the i-th harmonic. Let be the i-th harmonic fluctuation factor, and n be the sampling time.

3. The active control algorithm for helicopter fuselage vibration under time-varying load excitation and wave harmonic control according to claim 1, characterized in that, Step S2 specifically involves: obtaining the harmonic coefficient vector of the control signal input to the m-th actuator based on the harmonic coefficients of the control signal currently input to the actuator. And calculate the time-domain control signal input to the m-th actuator. : (3)。 4. The active control algorithm for wave harmonic control of helicopter fuselage vibration under time-varying load excitation as described in claim 1, characterized in that, Step S3 specifically involves: based on the current control error response... Harmonic basis functions and control error response harmonic coefficient Identify the harmonic coefficients of the control error response at the next moment: (4) Control input harmonic coefficients based on the current moment Control error response harmonic coefficient and control system frequency response function matrix Calculate the harmonic coefficients of the excitation response at the current moment: (5)。 5. The active control algorithm for helicopter fuselage vibration under time-varying load excitation and wave harmonic control according to claim 1, characterized in that, Step S4 specifically involves: S41: The formula for constructing the basis function of the i-th order wave harmonic is: ； in, , Let i be the frequency of the i-th harmonic. Given the i-th order harmonic fluctuation factor, calculate the i-th order wave harmonic basis function: ； in, The number of samples for the stimulus response, Let be the i-th harmonic coefficient of the k-th excitation response, and K be the number of excitation responses; S42: Based on the i-th order wave harmonic basis function constructed in S41, the control error response at the current moment, and the wave harmonic coefficients of the control error response, the LMS algorithm is used to identify the wave harmonic coefficients of the control error response signal. (8)。 6. The active control algorithm for helicopter fuselage vibration under time-varying load excitation and wave harmonic control according to claim 1, characterized in that, In step S5, the steepest descent method is used to correct the fluctuation harmonic coefficient of the control input signal in real time. (9) in, To correct the harmonic step size, obtain the fluctuation harmonic coefficient of the actuator control input, and return to S2.

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