New rapid convergence method for helicopter body vibration adaptive control

Abstract

The invention discloses a novel rapid convergence method for self-adaptive control of helicopter body vibration, and belongs to the field of active control of helicopter vibration. The method aims at solving the problems that in the helicopter vibration control process, a feed-forward control method is low in convergence speed, a feedback control method is difficult in full-state recognition, recognition errors easily cause control effect decline and the like, and the method is based on convergence characteristics of self-adaptive harmonic control and a linear matrix inequality method. According to the novel rapid convergence method for helicopter body vibration self-adaptive control, self-adaptive harmonic feedforward-sliding mode output feedback combined control is adopted, and the purpose of rapidly reducing helicopter body vibration is achieved. The control method provided by the invention has low requirement on modeling precision of a control system, does not need full-state identification of the system, has good control effect and convergence characteristic, and has excellent self-adaptability when the vibration load of the helicopter changes.

Description

Technical Field

[0001] The invention belongs to the technical field of helicopter vibration control, and specifically refers to a new fast convergence method for helicopter body vibration adaptive control. Background Art

[0002] The frequency components of the vibration load of the helicopter rotor are mainly the main passing frequency of the rotor and its multiples, and the vibration response of the fuselage is mainly reflected in the superposition of multi-order harmonic vibration responses. Therefore, active control of the vibration of the rotor passing frequency can effectively reduce the vibration response of the fuselage. Among many frequency domain feedforward algorithms, the harmonic synchronization identification and correction algorithm realizes the control of the steady-state harmonic response by identifying the harmonic coefficients of the control system error response and correcting the harmonic coefficients of the control signal. Compared with the control method based on discrete Fourier transform and its inverse transform, there is no problem of insufficient frequency sampling resolution and asynchronous sampling, which can effectively avoid the problems of control input signal delay and control effect degradation. However, in the case of sudden changes in the excitation of the helicopter rotor, since the control harmonic coefficient cannot be adjusted quickly, the fuselage will produce a large transient response and the convergence speed is slow. Moreover, since the convergence of the harmonic synchronization identification and correction algorithm is determined by the correction step size and the transfer function between the control input point and the observation output point, there is a design upper limit for the correction step size, which limits the convergence performance of the control system.

[0003] The time-domain feedback control method can effectively improve the convergence performance of the control system. Among them, the sliding mode feedback control algorithm is a variable structure control algorithm that adjusts the control input in real time according to the motion state of the control system. It has strong robustness. Once the system is driven into the sliding mode state, the transfer of the system state is not affected by the system parameters and external disturbances. However, the traditional sliding mode control algorithm relies on the real-time acquisition of the full state data of the control system, which is very difficult for vibration control of complex models. The introduction of the state observer not only puts forward high requirements on the modeling accuracy of the control system, but also increases the complexity and computational complexity of the control system. In addition, the error introduced by the state observation may reduce the control effect of the control system, and even cause control divergence. Summary of the invention

[0004] In view of the above-mentioned deficiencies in the prior art, the purpose of the present invention is to provide a new method for rapid convergence of adaptive control of helicopter body vibration, which adopts adaptive harmonic feedforward-sliding mode output feedback combined control to achieve efficient and rapid control of helicopter body vibration under rotor vibration load excitation.

[0005] To achieve the above object, the technical solution adopted by the present invention is as follows:

[0006] A novel fast convergence method for adaptive control of helicopter body vibration of the present invention adopts adaptive harmonic feedforward-sliding mode output feedback joint control, comprising the following steps:

[0007] S1. Establish a transfer function from control input to control output point, and establish a helicopter body vibration adaptive harmonic control method based on harmonic identification and synchronization correction algorithm;

[0008] S2. Calculate the convergence condition of the adaptive harmonic control algorithm and determine the design range of the harmonic correction step size;

[0009] S3. Establish the state space model of the helicopter airframe vibration active control system and design the sliding mode switching function to make the system motion in the sliding mode asymptotically stable;

[0010] S4. Based on the control system state space model established in S3, design the sliding mode output feedback control law to realize the sliding mode feedback control based on finite output;

[0011] S5, collecting the error response signal at the control point, generating the feedforward control input signal at the current moment based on the adaptive harmonic control algorithm, generating the feedback control input signal based on the sliding mode output feedback control law, and superimposing it with the feedforward control input signal to generate a hybrid control time domain signal;

[0012] Preferably, in S3, according to the state space model of the active vibration control system established in S3, a linear matrix inequality method is adopted to design a sliding mode switching function based on the stability criterion of the sliding mode of the control system.

[0013] Preferably, in S4, according to the convergence condition of the adaptive harmonic control algorithm obtained in S2, a linear matrix inequality method is adopted to design the sliding mode output feedback control rate based on the reachability of the sliding mode of the control system and the convergence of the adaptive harmonic control, with the goal of expanding the design range of the correction step size of the adaptive harmonic control algorithm and enhancing the convergence of the control system.

[0014] Preferably, the S5 comprises:

[0015] S51: Using the harmonic identification synchronous correction algorithm, calculate the control input harmonic coefficient at the current moment, multiply it with the harmonic basis function vector, and obtain the feedforward control time domain signal.

[0016] The S5 further comprises:

[0017] S52: Calculate the feedback control time domain signal according to the sliding mode switching function designed in S3 and the sliding mode output feedback control law designed in S4, and superimpose it with the feedforward control time domain signal to obtain a hybrid control time domain signal.

[0018] Beneficial effects of the present invention:

[0019] (1) The present invention realizes the adaptive harmonic feedforward-sliding mode output feedback joint control of helicopter body vibration, proposes a design criterion for improving the convergence of feedforward control, and improves the convergence performance of the active vibration control system on the basis of realizing efficient control of steady-state response.

[0020] (2) The present invention adopts a linear matrix inequality method to design a sliding mode switching function based on the sliding mode stability of the control system, and designs a sliding mode control law based on the sliding mode reachability of the control system and the convergence of the adaptive harmonic feedforward control, thereby realizing sliding mode feedback control relying only on limited output.

[0021] (3) The calculation examples using the present invention show that the machine body vibration control effect is good and the convergence is fast. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 The system block diagram of a new fast convergence method for adaptive control of helicopter body vibration according to the present invention.

[0023] Figure 2 Schematic diagram of the control error response of the helicopter body structure control point under the excitation of the rotor vibration load.

[0024] Figure 3 Schematic diagram of the control error response of the control point under the excitation of time-varying rotor vibration load.

[0025] Figure 4 The figure is a comparison diagram of the control effects of the control points when the existing adaptive harmonic control method and the new control method of the present invention are used respectively under the excitation of the time-varying rotor vibration load. DETAILED DESCRIPTION

[0026] In order to facilitate the understanding of those skilled in the art, the present invention is further described below in conjunction with embodiments and drawings. The contents mentioned in the implementation modes are not intended to limit the present invention.

[0027] Reference Figure 1 As shown, a new fast convergence method for adaptive control of helicopter body vibration of the present invention adopts adaptive harmonic feedforward-sliding mode output feedback joint control, including the following steps:

[0028] S1. Determine the control target frequency ω according to the helicopter rotor speed i , generate the harmonic basis function z(t). Establish the transfer function from the control input to the control point, where the frequency ω i The transfer function matrix T at ai for:

[0029]

[0030] Where M and K are the number of actuator actuation signals and control point output signals, Hmk (ω i ) is the distance from the mth actuator to the kth control point at frequency ω i The frequency response function at .

[0031] The control harmonic correction expression of the adaptive harmonic control algorithm is established:

[0032]

[0033] In the formula, μ i is the i-th order harmonic control correction step coefficient. e and W u are the weighting matrices of the response error signal and the actuator actuation signal, η i (t) is the harmonic coefficient of the error response corresponding to the i-th order harmonic.

[0034] S2. Order:

[0035]

[0036] The convergence condition of adaptive harmonic control is:

[0037]

[0038] In the formula, λ imax is the matrix Γ i The maximum eigenvalue of . Formula (4) is the design range of the harmonic correction step.

[0039] S3. Establish the state space model of the helicopter airframe vibration active control system:

[0040]

[0041] In the formula, is the system state vector, is the system output vector, are sliding mode feedback control, adaptive harmonic control and rotor load vector respectively. N, M and O are the state space order, the number of actuator channels and the number of rotor loads respectively. M<K<N. is the system matrix, and are the input matrices of control input and rotor load respectively, is the output matrix, and B s and C is full rank.

[0042] Further, formula (5) is simplified to:

[0043]

[0044] In the formula, B d =B w-B a (T a T W e T a +W u ) -1 (T a T W e T w ), T a is the frequency response function matrix of the control system. Define the sliding mode switching function s(t):

[0045] s(t)=SCx(t) (7)

[0046] Through the coordinate transformation relationship z = T z x makes the system (A,B s ,B d ,C) converted to the following form:

[0047]

[0048] In the formula, is a non-singular matrix, is a positive definite matrix.

[0049] Define the linear matrix inequality adjustment parameters α, β, δ, and the adjustment matrix Define a symmetric positive definite matrix And the matrix and Define the following linear matrix inequality:

[0050]

[0051] In the formula, the symbol "*" represents the element of the symmetric matrix, and

[0052]

[0053] By adjusting α>0, β>0, δ and the matrix make Q 11 , Q 12 , Q 22 , R exists, and the linear matrix inequality (9) holds, then the motion of the system in the sliding mode is asymptotically stable. The system sliding mode switching function matrix is:

[0054] S=[KI]H -1 (11)

[0055] S4. Based on the control system state space model established in S3, design the sliding mode output feedback control law. Define the following transformation: Then x r1(t) = z1(t), x r2 (t) = s(t). z ,B sz ,B dz ,C z ) to the following form:

[0056]

[0057] In the formula, A r11 =A 11 -A 12 KC1, Define the sliding mode control law:

[0058] u s (t)=-Gy(t)-v(t) (13)

[0059] Where G is the sliding mode output feedback matrix, and

[0060]

[0061] In the formula, ρ>0, δ>0. Let

[0062] A r Re-divided into in Defining the Matrix

[0063] Let the matrix λ ψimax and λ ψimin They are i The largest and smallest eigenvalues. Define the linear matrix inequality tuning parameters τ, α r , β r , define a positive definite real symmetric matrix Defining the Matrix Define linear matrix inequalities:

[0064]

[0065] By adjusting the parameters α r >0,β r >0, so that P r , P r2 , L1, L2 exist and inequality (16-18) holds, then the system has exponential convergence stability, and the correction step of the adaptive harmonic feedforward control has a larger design range and a shorter convergence time. The system sliding mode output feedback matrix is:

[0066]

[0067] S5, measure the error response signal at the control point, calculate the switching function value according to the sliding mode switching function designed in S3, and then calculate the sliding mode output feedback control signal u according to the sliding mode control law designed in S4 according to formula (13): s (t).

[0068] The error response signal is used to identify the error response harmonic coefficients, and the harmonic identification synchronous correction algorithm is used to calculate the harmonic coefficients of the adaptive harmonic feedforward control. The correction equation is shown in formula (4). Based on the control harmonic coefficients and the harmonic basis function vector sampling values, the adaptive harmonic feedforward control time domain signal u is calculated. a (t):

[0069] u a (t) = z(t) T γ(t) (19)

[0070] The adaptive harmonic feedforward control time domain signal and the sliding mode feedback control time domain signal are superimposed to obtain the hybrid control time domain signal u at the current moment. h (t):

[0071] u h (t) = u a (t)+u s (t) (20)

[0072] The generated hybrid control time domain signal is input to the actuator to drive the helicopter body to produce an actuation response, which offsets the rotor vibration excitation response, thereby realizing active control of the helicopter body vibration response.

[0073] Figure 2 The control error response of the helicopter airframe structure control point under the dual-frequency harmonic rotor vibration load excitation is given. After the control is turned on, the response of the measurement point drops to less than 0.005g within 4s and remains stable, which is 94% lower than the response before the control, indicating that the fast convergence method of helicopter airframe vibration adaptive harmonic feedforward-sliding mode output feedback control can effectively reduce the vibration of the control target point, and has strong convergence performance.

[0074] Figure 3The control error response of the vibration of the fuselage structure under the adaptive harmonic feedforward-sliding mode output feedback control when the amplitude, phase and frequency of the rotor vibration load change is given. The adaptive harmonic feedforward-sliding mode output feedback control is turned on at 20s, the excitation signal increases by 25% at 40s, the excitation signal phase increases by 0.5π at 60s, and the excitation signal frequency increases by 5% at 80s. After turning on the adaptive harmonic feedforward-sliding mode output feedback control, the response of the measuring point drops to about 0.005g within 4s and remains stable; when the excitation changes, the fuselage response can converge to within 10% of the uncontrolled response within 4s. It shows that the control method of the present invention has strong robustness and adaptability to changes in the helicopter vibration environment.

[0075] Figure 4 The control effect comparison diagram of the helicopter body vibration when the amplitude, phase and frequency of the rotor vibration load change respectively by using the existing adaptive harmonic control method and the adaptive harmonic feedforward-sliding mode output feedback control fast convergence method of the present invention. The control is turned on at 20s, the excitation signal increases by 25% at 40s, the excitation signal phase increases by 0.5π at 60s, and the excitation signal frequency increases by 5% at 80s. Compared with the adaptive harmonic control method, the control method of the present invention has a faster convergence speed in the time-varying load process. In addition, the ability to suppress the fuselage response after convergence is also stronger. The measurement point response can be maintained within 0.01g in each state after convergence. In contrast, the system using only adaptive harmonic control can only reduce the measurement point response to 0.015g. This is mainly because compared with the adaptive harmonic control method that only controls the steady-state response of the target frequency, the sliding mode output feedback module introduced by the control method of the present invention can have a certain suppression effect on the response outside the harmonic control target. It shows that the control method of the present invention has the advantages of both the adaptive harmonic control algorithm and the sliding mode output feedback algorithm, has good control effect, good convergence performance and strong adaptability.

[0076] The present invention has many specific application paths. The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements can be made without departing from the principle of the present invention. These improvements should also be regarded as the protection scope of the present invention.

Claims

1. A new method for rapid convergence of helicopter airframe vibration adaptive control, characterized in that Adaptive harmonic feedforward-sliding mode output feedback joint control is adopted, including the following steps: S1. Establish a transfer function from control input to control output point, and establish a helicopter body vibration adaptive harmonic control method based on harmonic identification and synchronization correction algorithm; S2. Calculate the convergence condition of the adaptive harmonic control algorithm and determine the design range of the harmonic correction step size; S3. Establish the state space model of the helicopter airframe vibration active control system and design the sliding mode switching function to make the system motion in the sliding mode asymptotically stable; S4. Based on the control system state space model established in S3, design the sliding mode output feedback control law to realize the sliding mode feedback control based on finite output; S5. Collect the error response signal at the control point, generate the feedforward control input signal at the current moment based on the adaptive harmonic control algorithm, generate the feedback control input signal based on the sliding mode output feedback control law, and superimpose it with the feedforward control input signal to generate a hybrid control time domain signal.

2. A new method for rapid convergence of helicopter airframe vibration adaptive control according to claim 1, characterized in that: In the above-mentioned S3, according to the state space model of the active vibration control system established in S3, a linear matrix inequality method is adopted to design a sliding mode switching function based on the stability criterion of the sliding mode of the control system.

3. A new fast convergence method for helicopter airframe vibration adaptive control according to claim 2, characterized in that: In the S4, according to the convergence condition of the adaptive harmonic control algorithm obtained in S2, the linear matrix inequality method is adopted, based on the reachability of the sliding mode of the control system and the convergence of the adaptive harmonic control, with the goal of expanding the design range of the correction step size of the adaptive harmonic control algorithm and enhancing the convergence of the control system, to design the sliding mode output feedback control rate.

4. The novel fast convergence method for helicopter airframe vibration adaptive control according to claim 1 is characterized in that: The S5 includes: S51: Using the harmonic identification synchronous correction algorithm, calculate the control input harmonic coefficient at the current moment, multiply it with the harmonic basis function vector, and obtain the feedforward control time domain signal.

5. A new method for rapid convergence of helicopter airframe vibration adaptive control according to claim 4, characterized in that: The S5 further comprises: S52: Calculate the feedback control time domain signal according to the sliding mode switching function designed in S3 and the sliding mode output feedback control law designed in S4, and superimpose it with the feedforward control time domain signal to obtain a hybrid control time domain signal.

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