Closed-loop frequency response parameter identification method of electric steering engine

Abstract

The invention provides a method for identifying closed-loop frequency response parameters of an electric steering engine, and aims to solve the common practical difficulties of many links, particularly complex friction and rotational inertia analysis, numerous influence factors and the like in the modeling process of the electric steering engine and abandon a traditional scheme for directly identifying specific electrical and mechanical parameters of the electric steering engine. And the parameter identification problem is merged into the identification problem of the sum of two comprehensive parameters. Establishing a proportional control closed-loop model and parameter representation of a transfer function by adopting a closed-loop identification method based on a frequency response technology; constructing a closed-loop system, obtaining closed-loop frequency response under sine input of each frequency, and performing nonlinear least square fitting on the frequency response of each frequency point to obtain a fitting value of a parameter sum; and the norm of the fitting residual error of each frequency point is taken as a criterion, and an identification result of the effective data group is screened out, so that the accuracy of parameter identification is ensured.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of electric rudder, in particular to a closed loop frequency response parameter identification method of electric rudder. BACKGROUND

[0002] Electric rudder is a control actuator widely used on aircraft, and its control performance directly affects the motion control ability and control accuracy of the aircraft. The control performance of electric rudder depends on the accuracy and effectiveness of its controlled model establishment, and the establishment of the model involves many aspects such as electricity and machinery. It is difficult to accurately identify and model these aspects one by one.

[0003] The traditional parameter identification usually adopts: 1) open loop frequency response technical scheme, for different frequency sinusoidal input signal, due to the large dynamic range of output signal, it is often necessary to artificially adjust the duty cycle of PWM in a large range, the signal acquisition efficiency is low; in addition, due to the problem of output signal zero drift, it brings difficulty to signal processing and the processing accuracy is difficult to guarantee. 2) closed loop step response technical scheme, taking the rise time and overshoot of the response as the target value, it is necessary to simulate according to the set range of model parameters, and compare the simulation result with the target value each time until the model parameters meeting the error requirement are searched. On the one hand, a large amount of simulation calculation is needed, on the other hand, the sensitivity of rise time and overshoot to model parameter change is low, so the model parameters obtained are often greatly deviated from the actual value. SUMMARY

[0004] Therefore, the present application aims to provide a closed loop frequency response parameter identification method of electric rudder, so as to solve the problems of low signal acquisition efficiency, low processing accuracy and large deviation of obtained model parameters from actual value in the prior art.

[0005] To achieve the above purpose, the technical scheme of the present application is as follows: A closed loop frequency response parameter identification method of electric rudder, comprising the following steps: S1, establishing the dynamic equation of electric rudder; S2, based on the dynamic equation of electric rudder, and introducing feedback, constructing a closed loop proportional control model of electric rudder; S3, based on the closed loop proportional control model, constructing a proportional control system structure block diagram of electric rudder; S4, based on the proportional control system structure block diagram, simplifying the transfer function of electric rudder, and constructing a closed loop simplified model block diagram of electric rudder; S5, based on the closed loop simplified model block diagram, obtaining the parameter representation of closed loop transfer function and frequency response; S6, based on the closed loop simplified model block diagram, constructing a closed loop system of proportional control electric rudder; S7, applying a sine signal with a set frequency and amplitude to the closed-loop system of the proportional control electric rudder, to obtain a measurement signal; S8, calculating a closed-loop frequency response based on the measurement signal; S9, fitting comprehensive parameters based on the closed-loop frequency response and ; S10, repeating the measurement and calculation process of steps S7 to S9 based on the determined proportional gain, to obtain multiple sets of measurement data and fitted values of comprehensive parameters and , screening valid measurement data sets and effective values of comprehensive parameters and based on a set fitting residual norm criterion, and obtaining an effective comprehensive parameter and by taking the statistical mean of the effective comprehensive parameters as the final parameter identification result.

[0006] Further, in step S1, the dynamic equation of the electric rudder is established, including: According to the voltage balance equation, the torque balance equation of the motor shaft, and the gear transmission equation, the dynamic equation of the electric rudder is established.

[0007] Further, in step S3, based on the closed-loop proportional control model, the proportional control system structure block diagram of the electric rudder is constructed, including: Based on the closed-loop proportional control model, Laplace transform is performed under zero initial conditions to obtain the transfer function of the electric rudder, and based on the transfer function, the proportional control system structure block diagram is constructed.

[0008] Further, in step S7, based on the measurement signal, the closed-loop frequency response is calculated, including: Based on the set proportional gain selection principle, the proportional gain is determined in a trial-and-error manner, and the measurement signal is subjected to fast Fourier transform to calculate the frequency response corresponding to the proportional gain.

[0009] Further, in step S8, based on the closed-loop frequency response, comprehensive parameters and are fitted, including: Based on the closed-loop frequency response, nonlinear least squares fitting is performed according to the closed-loop transfer function to obtain fitted values of comprehensive parameters and , and thus the closed-loop transfer function is obtained.

[0010] Further, in step S5, the expression of the closed-loop transfer function is as follows: ; In the formula, and is a comprehensive parameter, is a proportional gain.

[0011] Further, in step S5, the expression of the frequency response characteristic is as follows: ; In the formula, is a sine input frequency, is an amplitude characteristic, is a corresponding phase characteristic, and is a comprehensive parameter, is a proportional gain.

[0012] With respect to the prior art, the method for identifying the closed-loop frequency response parameters of an electric rudder according to the present application has the following beneficial effects: (1) Instead of directly identifying the specific electrical and mechanical parameters of the electric rudder, the method according to the present application combines the identification of these parameters into the identification of two comprehensive parameters and , which significantly reduces the difficulty of parameter identification and provides convenience for the subsequent design of the rudder control scheme.

[0013] (2) The method according to the present application combines the frequency response technology with the closed-loop scheme of proportional control, solves the problems of the output signal zero drift and the need for manual adjustment of the PWM duty cycle in the open-loop scheme, and avoids the problems of the step response scheme, such as the dependence on a large number of simulation searches for model parameters and the low sensitivity to changes in the model parameters, which may result in low accuracy of parameter identification.

[0014] (3) The method according to the present application is simple to operate, fast in iteration, and high in identification efficiency. The frequency response characteristics at each frequency point are obtained from one-time measurement signals, and the accuracy of parameter identification can be effectively guaranteed by parameter fitting on the frequency characteristics at multiple frequency points.

[0015] (4) The method according to the present application is highly universal and almost does not depend on computer simulation, and is suitable for DC electric rudders of various transmission forms. BRIEF DESCRIPTION OF DRAWINGS

[0016] The accompanying drawings, which form a part of this application, are included to provide a further understanding of the application and are incorporated in and constitute a part of this application. The embodiments of the present application illustrated in the drawings and their descriptions are used to explain the present application and are not intended to limit the present application unduly. Figure 1 is a structural block schematic diagram of the proportional control system of the electric rudder according to the embodiment of the present application; Figure 2 is a structural block schematic diagram of the closed-loop simplified model of the electric rudder according to the embodiment of the present application; Figure 3Typical experimental measurement signal schematic diagram of the electric rudder closed loop system according to the embodiment of the present application; Figure 4 Experimental measurement curve schematic diagram of the frequency response characteristics of the electric rudder closed loop system according to the embodiment of the present application under different proportional gain; Figure 5 Schematic diagram of the frequency response compared with the frequency response calculated by parameters according to the embodiment of the present application. DETAILED DESCRIPTION

[0017] It should be noted that the embodiments in the present application and the features in the embodiments can be combined with each other without conflict.

[0018] In the description of the present application, it should be understood that the terms "center", "longitudinal", "transverse", "upper", "lower", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer" and the like indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, and are only for the purpose of facilitating the description of the present application and simplifying the description, and do not indicate or imply that the device or element referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation of the present application. In addition, the terms "first", "second" and the like are only for the purpose of description and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the technical features indicated. Therefore, the features defined with "first", "second" and the like can explicitly or implicitly include one or more of the features. In the description of the present application, unless otherwise specified, the meaning of "a plurality of" is two or more.

[0019] In the description of the present application, it should be noted that unless otherwise explicitly specified and limited, the terms "mounting", "connecting", "connection" should be understood in a broad sense, for example, it can be fixed connection, or detachable connection, or integrally connected; it can be mechanical connection, or electrical connection; it can be directly connected, or indirectly connected through intermediate medium, or the communication inside two elements. For those skilled in the art, the specific meaning of the above terms in the present application can be understood through specific circumstances.

[0020] The present application will be described in detail below with reference to the accompanying drawings and in conjunction with embodiments.

[0021] As Figures 1 to 5As shown, the application provides a frequency response based closed loop parameter identification method for electric rudder, aiming at the practical difficulties such as too many links in the modeling process of electric rudder, especially the complex analysis of friction and rotational inertia, and many influencing factors, the traditional scheme of directly identifying the specific electrical and mechanical parameters of electric rudder is abandoned, and the parameter identification problem is merged into the identification problem of two comprehensive parameters a and b. The closed loop identification method based on frequency response technology is adopted to establish the parameter representation of the closed loop model and the transfer function of proportional control; the closed loop system is constructed, the closed loop frequency response under each frequency sinusoidal input is obtained, the frequency response of each frequency point is nonlinear least square fitted to obtain the fitting value of parameters a and b; the norm of each frequency point fitting residual is taken as the criterion to screen out the identification result of the effective data set to ensure the accuracy of parameter identification.

[0022] The application effectively solves the problems of output signal zero drift and PWM duty cycle needing artificial adjustment of the open loop frequency response method, and can identify parameters a and b at one time, which can significantly improve the parameter identification efficiency. In addition, the application is also different from the method of indirectly obtaining model parameters through rise time and overshoot in the step response technology scheme, but directly identifies the comprehensive parameters a and b, which can ensure the accuracy of parameter identification, and the identification result can be directly used for the design of the control scheme.

[0023] A closed loop frequency response parameter identification method of an electric rudder, comprising the following steps: (1) establishing an electric rudder model and reasonably simplifying, and concentrating each electrical and mechanical parameter into two comprehensive parameters and , so that the parameter identification problem of the electric rudder is reduced to the identification problem of parameters and .

[0024] (2) establishing a proportional control electric rudder closed loop transfer function model and constructing an experimental system, on the basis of which, frequency response technology is adopted for parameter identification.

[0025] (3) combining the sinusoidal input signals of each frequency and amplitude in time, and applying them to the closed loop system, due to the existence of feedback signals, the zero point of the output signal can be stabilized and the PWM duty cycle of the measurement process can be automatically adjusted, and the frequency response of each frequency point can be obtained at one time.

[0026] (4) selecting a suitable proportional gain, performing fast Fourier transform on the obtained measurement signals to obtain the amplitude and phase of the corresponding frequency point; according to the parameter representation of the closed loop transfer function (taking the transfer function with and as the to-be-determined parameters), the frequency response of each frequency point is nonlinear least square fitted to obtain the parameters and the fitting value.

[0027] (5) taking the statistical mean of the fitting parameters of several groups of effective measurement data as the final parameter identification result.

[0028] According to the specific performance of the parameter identification rudder and the signal acquisition mode, the amplitude and frequency range of the input sinusoidal signal, the effectiveness judgment of the measurement data, and the selection principle of the proportional gain are as follows: The preferred frequency and amplitude range of the sinusoidal input signal is shown in Table 1, with a period of 1ms sampling, 10000 sampling points per frequency point, and a total signal length of 150000 points (150s).

[0029] Table 1

[0030] The preferred criterion for determining the effectiveness of the measurement data is that the norm of the fitting residual at each frequency point is not greater than 1, which can reduce the influence of random factors such as mechanical processing and assembly on the fitting accuracy as much as possible.

[0031] The preferred selection principle of the proportional gain is that the amplitude-frequency resonance peak in the full frequency range is not more than 2dB and the amplitude attenuation at the highest frequency is not more than 20dB, which can not only satisfy the higher sensitivity of the amplitude to the parameter (a, b) change but also ensure sufficient signal-to-noise ratio at high frequency. and

[0032] The present application has the following beneficial effects: The present application does not directly identify the specific electrical and mechanical parameters of the electric rudder, but identifies these parameters as the identification of two comprehensive parameters a and b, which significantly reduces the difficulty of parameter identification and provides convenience for subsequent rudder control scheme design.

[0033] The present application combines the frequency response technology with the closed-loop scheme of proportional control, solves the problems of output signal zero drift and PWM duty cycle requiring manual adjustment in the open-loop scheme, and avoids the problems of relying on a large number of simulation searches for model parameters and the low sensitivity to changes in model parameters, which may lead to low accuracy of parameter identification.

[0034] The present application is simple to operate, fast in iteration, high in identification efficiency, and obtains the frequency response characteristics of each frequency point from a one-time measurement signal, which can effectively ensure the accuracy of parameter identification by fitting the frequency characteristics of multiple frequency points.

[0035] The present application is highly versatile and almost independent of computer simulation, and is suitable for various transmission forms of DC electric rudders. ​

[0036] Embodiment 1 The present application is further described with an example of an air vane of a direct current servo motor. A closed loop frequency response parameter identification method of an electric rudder includes the following steps: Step one, establishing the dynamics equation of the electric rudder system According to the voltage balance equation of the direct current motor, the torque balance equation of the motor shaft and the gear transmission equation, the dynamics equation of the electric rudder is established, and the expression is as follows: (1) ; In the formula, L is the armature inductance, R is the armature resistance, I is the armature current, V is the voltage applied to the armature, K is the back electromotive force constant, T is the motor torque constant, when the international unit system is used, it has , J is the total moment of inertia converted to the motor shaft, B is the total viscous friction coefficient converted to the motor shaft, T is the load torque, G is the reduction ratio of the transmission mechanism, ω is the angular velocity of the motor shaft, θ is the motor shaft angle, θ is the output angle, t is the time variable.

[0037] Step two, establishing the closed loop proportional control model of the electric rudder Based on the dynamics equation of the electric rudder, the feedback is introduced, and the closed loop model of proportional control is established, that is, the following expression is added to formula (1): (2) ; In the formula, V is the voltage applied to the armature, θ is the output angle, t is the time variable, K is the proportional gain, θ is the reference input of the angle.

[0038] Step three, obtaining the block diagram representation of the electric rudder Based on the entire closed loop model composed of formula (1) and formula (2), the Laplace transform is carried out under the zero initial condition, and the transfer functions of each part are as follows: (3) ; In the formula, s is a complex variable, K is the proportional gain Laplace transform, The input signal in equation (2) Laplace transform, The output rotation angle in equation (2) The Laplace transform of the variables is similar, and the correspondence of the other variables is similar.

[0039] like Figure 1 As shown, the block diagram of the proportional control system corresponding to equation (3) is shown in the figure. This indicates an error signal.

[0040] Step 4: Simplify the block diagram of the proportional control system and separate the parameters to be identified. Based on the characteristics of DC motors, armature inductance is ignored. and load Move to At the same summation point, such as Figure 2 As shown in the simplified model block diagram, the simplified transfer function of the electric servo motor is as follows: (4); In the formula, Let be the transfer function of the electric servo motor. For complex variables, and These are comprehensive parameters.

[0041] Among them, parameters , Process parameters The relationship between the mechanical and electrical parameters is expressed as follows: ; ; ; In the formula, and For comprehensive parameters, The torque constant of the motor. This is the reduction ratio of the transmission mechanism. For armature resistance, For process parameters, The total moment of inertia referred to the motor shaft, The total viscous friction coefficient referred to the motor shaft, is the back electromotive force constant.

[0042] Step 5: Obtain the parameter representations of the closed-loop transfer function and frequency response. based on Figure 2 The simplified model block diagram is shown below. The closed-loop transfer function from the reference input to the corner output is calculated, and the expression is as follows: (5); In the formula, For closed-loop transfer function For complex variables, and For comprehensive parameters, This is the proportional gain.

[0043] Under sinusoidal input conditions, the frequency response is expressed as follows: (6); In the formula: The input frequency is a sine wave. For amplitude characteristics, For the corresponding phase characteristics, and For parameters, This is the proportional gain.

[0044] Step 6: Construct an electric servo motor closed-loop system and acquire the output signal. according to Figure 2 A simplified block diagram is used to construct a proportionally controlled electric servo motor closed-loop system. Sine signals of various frequencies and amplitudes as shown in Table 1 are applied continuously at once, and the output rotation angle signal is recorded. Typical measurement signals include... Figure 3 As shown, the zero point of the output sine signal is stable.

[0045] Step 7: Calculate the closed-loop frequency response Based on the selection principle of proportional gain, a suitable proportional gain is determined through trial and error. A fast Fourier transform is then performed on the measured signal to obtain the system's frequency response characteristics. For example... Figure 4 As shown, the frequency responses are for proportional gains of 8, 10, and 12. Figure 4 In the diagram, the vertical axis represents Magnitude and the horizontal axis represents Frequency.

[0046] Step 8: Fitting Parameters and

[0047] Using the amplitude-frequency data of the frequency response, nonlinear least-squares fitting is performed on each frequency point according to equation (6) to obtain the parameters. and The fitted value is obtained, and thus the closed-loop transfer function described by equation (5) is obtained.

[0048] like Figure 5 As shown, when the proportional gain is 8, a comparison is made between the frequency response obtained from measurement and the frequency response calculated from the fitted transfer function. Figure 5 In the diagram, the vertical axis represents Magnitude and the horizontal axis represents Frequency.

[0049] Step 9: Repeated measurements and calculations to obtain parameters. and Identification results Based on the selected proportional gain, repeat steps six through eight of the above measurement and calculation process to obtain multiple sets of measurement data and parameter fitting values. Based on the fitting residual norm criterion, select the valid data and calculate the parameters for each valid data set. and The statistical mean is used as the final parameter identification result.

[0050] For each channel of the two servos (each servo has 4 independent channels, numbered I) IV markings) respectively in no bias and With a 12° bias, the sinusoidal input signal as shown in Table 1 was applied, and signal acquisition and processing were performed. The fitted parameters are shown in Table 2. In order to interpret the fitting effect, the norm of the fitting residuals (denoted as Nres in the table) is also given in the table.

[0051] Table 2. Parameter identification results for each channel of the two servos ( )

[0052] After discarding invalid data (residuals greater than 1), the parameters in Table 2 are... and Statistical analysis yielded the following parameter identification values ​​(mean) and standard deviations: ; ; ; ; In the formula, and Parameters and The statistical mean and The standard deviation of the corresponding parameter, This represents the number of valid data sets.

[0053] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for identifying closed-loop frequency response parameters of an electric actuator, characterized in that: The method comprises the following steps: S1, establishing a dynamic equation of the electric rudder; S2, based on the dynamic equation of the electric rudder, and introducing feedback, constructing a closed-loop proportional control model of the electric rudder; S3, based on the closed-loop proportional control model, constructing a proportional control system structure block diagram of the electric rudder; S4, based on the proportional control system structure block diagram, simplifying the transfer function of the electric rudder, and constructing a closed-loop simplified model block diagram of the electric rudder; S5, based on the closed-loop simplified model block diagram, obtaining the parameter expression of the closed-loop transfer function and the frequency response; S6, based on the closed-loop simplified model block diagram, constructing a proportional control electric rudder closed-loop system; S7, applying a sine signal with a set frequency and amplitude to the proportional control electric rudder closed-loop system to obtain a measurement signal; S8, based on the measurement signal, calculating the closed-loop frequency response; S9. Based on the closed loop frequency response, fit the comprehensive parameters and ; S10, based on the determined proportional gain, repeating the measurement and calculation process of steps S7 to S9 to obtain multiple sets of measurement data and comprehensive parameters and fitting values, based on a set fitting residual norm criterion, screening effective measurement data sets and comprehensive parameters therefrom and effective values, obtaining effective comprehensive parameters and statistical mean values as the final parameter identification results.

2. The closed-loop frequency response parameter identification method of an electric actuator according to claim 1, characterized in that: In step S1, the dynamic equation of the electric rudder is established, including: According to the voltage balance equation, the torque balance equation of the motor shaft and the gear transmission equation, the dynamic equation of the electric rudder is established.

3. The method of claim 1, wherein: In step S3, based on the closed-loop proportional control model, the proportional control system structure block diagram of the electric rudder is constructed, including: Based on the closed-loop proportional control model, Laplace transform is carried out under zero initial condition to obtain the transfer function of the electric rudder, and based on the transfer function, the proportional control system structure block diagram is constructed.

4. The closed-loop frequency response parameter identification method of an electric actuator according to claim 1, characterized in that: In step S7, based on the measurement signal, the closed-loop frequency response is calculated, including: Based on the set proportional gain selection principle, the proportional gain is determined in a trial-and-error manner, and the measurement signal is subjected to fast Fourier transform to calculate the frequency response corresponding to the proportional gain.

5. The closed loop frequency response parameter identification method of an electric actuator according to claim 1, wherein: In step S8, based on the closed loop frequency response, the synthesis parameters are fitted and comprising: Based on the closed-loop frequency response, a nonlinear least square fitting is performed according to a closed-loop transfer function to obtain the comprehensive parameters and the fitting values, and thus the closed-loop transfer function.

6. The closed-loop frequency response parameter identification method of an electric actuator according to claim 1, wherein: In step S5, the expression of the closed-loop transfer function is as follows: ； wherein and is an integrated parameter, is a proportional gain, is a complex variable.

7. The method of claim 1, wherein: In step S5, the expression of the frequency response characteristic is as follows: ； wherein is the sinusoidal input frequency, is the amplitude characteristic, is the corresponding phase characteristic, and is the integrated parameter, is the proportional gain.

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