Method for mechanical resonance detection of an electromechanical servo system

Abstract

The application discloses a kind of electromechanical servo system mechanical resonance detection method, belong to rudder mechanical resonance detection technical field, method includes: collection set signal, error signal of set signal and feedback signal, the differential of real-time calculation signal, when detecting signal differential zero-crossing point, there may be vibration source at this time, record the time and amplitude when differential zero-crossing point;According to historical record information, calculate the current waveform harmonic frequency, when detecting the waveform in the mechanical harmonic range, set signal frequency is much smaller than mechanical resonance frequency, then consider that feedback signal contains harmonic;When detecting that the peak value of two adjacent harmonics of feedback signal is similar, it is determined that mechanical resonance has occurred, otherwise, it is determined that mechanical resonance has not occurred, the whole detection process only involves differential calculation and simple mathematical calculation, the implementation is simple, compared with Fourier transform, the complexity is greatly reduced, and the requirement of mechanical resonance on hardware computing function is reduced.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of mechanical resonance detection of rudder mechanisms, and particularly relates to a mechanical resonance detection method for an electromechanical servo system. BACKGROUND

[0002] The electromechanical servo system usually adopts the form of a motor + a harmonic reducer + a load. Due to the existence of gaps and flexible characteristics of the transmission mechanism, the system itself has a certain resonance frequency, i.e., a mechanical resonance frequency. When the torsional frequency of the servo system is close to or the same as the mechanical resonance frequency, the system will have obvious mechanical resonance, i.e., the servo system will have serious jitter near the target value. The mechanical resonance not only affects the performance of the servo system, but also may damage the transmission device and burn the motor. In actual flight of a UAV, the safety of the electromechanical servo system is directly related to the safety of the whole machine. However, the mechanical resonance is related to the flexible characteristics of the structure of the servo system and the load inertia, and its mechanical resonance frequency is different in different working conditions. Therefore, it is difficult to test whether the servo system will have mechanical resonance in actual flight of the UAV on the ground. Therefore, it is very important to detect in real time whether the servo system has mechanical resonance for the safety of the UAV.

[0003] At present, the mechanical resonance of the rudder mechanism is mainly detected by using the Fourier transform method. The method first collects a feedback signal of the rudder mechanism and a set signal. The feedback signal is a signal detected from the actual output position of the rudder mechanism, which can reflect the actual working state of the rudder mechanism. The set signal is an ideal or expected output in a control instruction, which is used to indicate the target position that the rudder mechanism needs to reach. Then, the feedback signal and the set signal are subjected to Fourier transform, and then whether the rudder mechanism has mechanical resonance is confirmed according to the Fourier transform result. The Fourier transform calculation is complex, the control frequency of the servo system is high, and a large amount of data is generated. The real-time Fourier transform of the feedback signal and the set signal has high requirements for the hardware calculation capability. Meanwhile, there are many interference signals in the actual application scene, and the signals are not sinusoidal signals in theory. Therefore, the detection of the mechanical resonance of the rudder mechanism by using the Fourier transform is prone to misjudgment. SUMMARY

[0004] The present application aims at overcoming the problems in the prior art, and provides a mechanical resonance detection method for an electromechanical servo system.

[0005] The purpose of the present application is achieved by the following technical scheme: a mechanical resonance detection method for an electromechanical servo system, which comprises the following steps:

[0006] Collecting a given signal in a control instruction for controlling the rudder mechanism to reach a target position and a feedback signal reflecting the actual output position of the rudder mechanism, and defining the difference between the set signal and the feedback signal as an error signal;

[0007] Calculating the differential of the set signal and the error signal;

[0008] When the zero-crossing point of the derivative of the set signal or error signal is detected, the sampling time and sampling amplitude of the corresponding signal are recorded.

[0009] When the zero-crossing point of the derivative of the error signal is detected, the harmonic frequency wf(k) and the peak-to-peak value f of the error signal are calculated based on the sampling time of the error signal. pp (k);

[0010] Determine whether mechanical resonance occurs based on the harmonic frequency and the set mechanical resonance range aw~bw:

[0011] When wf(k) > bw, it is considered interference;

[0012] When bw > wf(k) > aw, the harmonic frequency ws(t) of the set signal is calculated based on the sampling time of the set signal. When kwf(k) < ws(t), no mechanical resonance occurs; when ws(t) < kwf(k), resonance occurs, and the resonance number is incremented by 1. When the resonance number is greater than 1, and the current peak-to-peak value f pp (k) and the previously recorded harmonic peak-to-peak value f pp When the absolute value of the (k-1) change ratio is less than m, mechanical resonance occurs. The resonant frequency is the harmonic frequency of the feedback signal, and the peak-to-peak value of the resonance is the peak-to-peak value of the harmonics of the feedback signal, f. pp (k); k is the resonance threshold, ranging from 0.3 to 0.9; m is the peak-to-peak value variation threshold, less than 0.2;

[0013] When aw > wf(k), resonance does not occur.

[0014] In one example, the differential calculation expressions for the signal and the error signal are set as follows:

[0015]

[0016] in, x(k) represents the derivative of the signal over time; x(k) represents the sampled value of the set signal or error signal at sampling time k; x(k-1) represents the sampled value of the set signal or error signal at sampling time k-1. This represents the sampling time difference.

[0017] In one example, the expression for calculating the zero-crossing point of the derivative of the set signal or error signal is:

[0018]

[0019] in, This represents the differential of the set signal or error signal at sampling time k; This represents the derivative of the set signal or error signal at sampling time k-1.

[0020] In an example, the calculation expression of the harmonic frequency wf(k) is:

[0021]

[0022] Wherein, dataf_t(k) is the sampling time of the error signal at sampling time k; dataf_t(k-1) is the sampling time of the error signal at sampling time k-1.

[0023] In an example, the calculation expression of the harmonic frequency ws(t) is:

[0024]

[0025] Wherein, datas_t(k) represents the sampling time of the setting signal at sampling time k; datas_t(k-t) represents the sampling time of the setting signal at sampling time k-t; t is a natural number.

[0026] In an example, the calculation expression of the peak-to-peak value f pp (k) is:

[0027] f pp (k) = |dataf_f(k) - dataf_f(k-1)|

[0028] Wherein, dataf_f(k) represents the amplitude of the error signal at sampling time k; dataf_f(k-1) represents the amplitude of the error signal at sampling time k-1.

[0029] In an example, before collecting the setting signal and the feedback signal of the steering engine, it further includes judging whether the mechanical resonance exists in the servo system, including the following sub-steps:

[0030] Establishing a mathematical model of the servo system:

[0031]

[0032] Wherein, J1 is the equivalent inertia of the servo motor, lead screw, reducer and coupling converted into the primary side; J2 is the equivalent secondary side inertia of the load; Ks and Cs are the equivalent transmission stiffness and damping coefficient, respectively; B1 and B2 represent the viscous friction coefficients of the two sides, respectively; Tc1 and Tc2 are the Coulomb friction torques of the two sides; Te is the electromagnetic torque output by the motor; Ts is the torsional torque of the shaft system, which is affected by the angle difference (θ1-θ2) and the speed difference (ω1-ω2) of the primary side and the secondary side;

[0033] According to the mathematical model of the servo system, the transfer function G(s) is calculated:

[0034]

[0035] According to the transfer function, it is known that the servo system has a conjugate pole, and the resonance frequency ω is:

[0036]

[0037] It should be further explained that the technical features corresponding to the above examples can be combined or replaced to form new technical solutions.

[0038] Compared with the prior art, the present application has the following advantages:

[0039] The present application acquires the set signal, the error signal of the set signal and the feedback signal, calculates the differential of the signal in real time, records the time and amplitude when the differential zero-crossing point is detected, and calculates the current waveform harmonic frequency according to the historical record information. When the waveform in the mechanical harmonic range is detected, it is detected whether the set and error harmonic frequencies are similar. If the frequencies are similar, mechanical resonance does not occur at this time, otherwise, it is determined that mechanical resonance has occurred. The whole detection process only involves differential calculation and simple mathematical calculation, the implementation is simple, the complexity is greatly reduced compared with Fourier transform, mechanical resonance can be quickly detected, the requirement of mechanical resonance on the hardware calculation function is reduced, it is universal and can be transplanted to other servo systems, and it is popularized. Further, the present application uses differential identification and judgment of mechanical resonance, does not need to rely on Fourier transform for frequency domain analysis of the signal, and therefore has high anti-interference ability and is not easy to misjudge, and has better robustness and accuracy. BRIEF DESCRIPTION OF DRAWINGS

[0040] The specific embodiments of the present application will be further described in detail below with reference to the accompanying drawings, which are used to provide further understanding of the present application, and form a part of the present application. The same reference numerals are used to represent the same or similar parts in the accompanying drawings, the schematic embodiments of the present application and the description thereof are used to explain the present application, and do not constitute an improper limitation on the present application.

[0041] Figure 1 The transmission relationship diagram of the servo control system provided for an example of the present application is shown in the figure.

[0042] Figure 2 The method flowchart provided for an example of the present application is shown in the figure.

[0043] Figure 3 The measured rudder mechanical resonance data schematic diagram provided for an example of the present application is shown in the figure.

[0044] Figure 4 The amplitude-frequency curve diagram after Fourier transform provided for an example of the present application is shown in the figure. DETAILED DESCRIPTION

[0045] The technical solutions of the present application will be described clearly and completely below in conjunction with the drawings. Obviously, the described embodiments are part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative efforts fall within the scope of protection of the present application.

[0046] In the description of the present application, it should be noted that the directions or positional relationships indicated by "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc. are the directions or positional relationships described based on the drawings, and are only for the convenience of describing the present application and simplifying the description, and therefore cannot be understood as indicating or implying that the devices or elements referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as limiting the present application. In addition, the ordinal numbers (such as "first and second", "first to fourth", etc.) are used to distinguish objects, and are not limited to the order, and cannot be understood as indicating or implying relative importance.

[0047] In the description of the present application, it should be noted that, unless otherwise explicitly specified and limited, the terms "mounting", "connecting", and "connecting" should be understood broadly, for example, can be fixedly connected, can be detachably connected, or integrally connected; can be mechanically connected, or electrically connected; can be directly connected, or indirectly connected through an intermediate medium; or can be the communication between two elements. For those skilled in the art, the specific meanings of the above terms in the present application can be understood according to the specific circumstances.

[0048] In addition, the technical features involved in the different embodiments of the present application described below can be combined with each other as long as there is no conflict.

[0049] A mechanical resonance detection method of an electromechanical servo system, before performing the mechanical resonance detection step, it is necessary to determine that the servo system has mechanical resonance, the present application is realized by establishing the mathematical model of servo system, the implementation is as follows:

[0050] S11: Establishing a mathematical model of a servo system: The transmission relationship of a servo control system can usually be adopted as Figure 1The dynamic model of the two-mass structure is shown. The servo motor, screw, reducer and coupling are converted into the equivalent inertia of the primary side, denoted as J1; and the load is equivalent to the inertia of the secondary side, denoted as J2; Ks and Cs are the equivalent transmission stiffness and damping coefficient respectively; b is the equivalent transmission gap. B1 and B2 represent the viscous friction coefficients of the two sides respectively; Tc1 and Tc2 are the Coulomb friction torques of the two sides; Te is the electromagnetic torque output by the motor; and Ts is the torsional torque of the shaft system, which is affected by the angle difference (θ1-θ2) and the speed difference (ω1-ω2) of the primary side and the secondary side.

[0051] Without considering the gap effect, according to the dynamics principle, the following can be obtained:

[0052]

[0053] S12: The transfer function G(s) is calculated according to the above formula:

[0054]

[0055] In actual working conditions, the viscous friction coefficient is small and can be ignored, and the transfer function is as follows:

[0056]

[0057] S13: According to the transfer function, the servo system has a conjugate pole, and the resonance frequency ω is:

[0058]

[0059] By establishing the mathematical model of the servo system, it can be proved that the servo system has mechanical resonance, but the specific numerical value cannot be calculated. Therefore, the present application further adopts differential identification and judgment of mechanical resonance.

[0060] In an example, a mechanical resonance detection method of an electromechanical servo system, the method comprising the following steps:

[0061] S21: Collecting a set signal and a feedback signal.

[0062] Assuming that the bandwidth of the servo system is w, and the mechanical resonance range is between aw and bw, according to the Shannon theorem, the sampling frequency can be set to 10bw. After the signal is collected, the differential is calculated. Further, the set signal is the ideal or desired output in the control command, which indicates the target position that the steering engine needs to reach. The feedback signal is the signal detected from the actual output position of the steering engine, which can reflect the actual working state of the steering engine. The difference between the set signal and the feedback signal is defined as the error signal.

[0063] S22: Calculating the differential of the set signal and the error signal.

[0064] S23: When the differential zero-crossing point of the set signal or the error signal is detected, the sampling time and the sampling amplitude of the corresponding signal are recorded.

[0065] The presence of a vibration source is determined by analyzing the differential zero-crossing point of the signal, so changes in the vibration source often produce characteristic signals near the zero-crossing point.

[0066] S24: When the differential zero-crossing point of the error signal is detected, the harmonic frequency wf(k) and the harmonic peak-to-peak value f pp (k) of the error signal are calculated according to the sampling time of the error signal.

[0067] S25: According to the harmonic frequency wf(k) and the set mechanical resonance range aw~bw, it is judged whether mechanical resonance occurs:

[0068] When wf(k) > bw, it is determined as interference, and the recorded data at sampling times k and k-1 are deleted;

[0069] When bw > wf(k) > aw, the harmonic frequency ws(t) of the set signal is calculated according to the sampling time of the set signal, when kwf(k) < ws(t), mechanical resonance does not occur at this time, and the resonance frequency f_num is cleared; when ws(t) < kwf(k), resonance occurs at this time, and the resonance frequency f_num is increased by 1, that is: resonance frequency f_num = f_num + 1; when the resonance frequency f_num is greater than 1, and the change absolute value of the current resonance peak-to-peak value f pp (k) and the last recorded harmonic peak-to-peak value f pp (k-1) is less than m, mechanical resonance occurs at this time, the resonance frequency is the harmonic frequency of the feedback signal, and the resonance peak-to-peak value is the harmonic peak-to-peak value f pp (k) of the feedback signal; k is a resonance threshold value, and the value range is 0.3-0.9, preferably 0.7; m is a peak-to-peak value change threshold, less than 0.2;

[0070] When aw > wf(k), no processing is done at this time, and resonance does not occur.

[0071] In an example, the differential calculation expression of the set signal and the feedback signal is:

[0072]

[0073] Wherein, represents the differential of the signal with respect to time; x(k) represents the set signal or feedback signal sampling value at sampling time k; x(k-1) represents the set signal or feedback signal sampling value at sampling time k-1; represents the sampling time difference.

[0074] In an example, the calculation expression of the differential zero-crossing point of the setting signal or the error signal or the feedback signal is:

[0075]

[0076] wherein, represents the differential of the setting signal or the error signal or the feedback signal at the sampling time point k; represents the differential of the setting signal or the error signal or the feedback signal at the sampling time point k-1.

[0077] In an example, the calculation expression of the harmonic frequency wf(k) is:

[0078]

[0079] wherein, dataf_t(k) is the sampling time of the error signal at the sampling time point k; dataf_t(k-1) is the sampling time of the error signal at the sampling time point k-1.

[0080] In an example, the calculation expression of the harmonic frequency ws(t) is:

[0081]

[0082] wherein, datas_t(k) represents the sampling time of the setting signal at the sampling time point k; datas_t(k-t) represents the sampling time of the setting signal at the sampling time point k-t.

[0083] In an example, when the differential zero-crossing point of the setting signal or the error signal is detected, the sampling amplitude of the corresponding signal is recorded;

[0084] When the mechanical resonance occurs, the peak-to-peak value f pp (k) of the resonance frequency is calculated according to the amplitude of the error signal. Optionally, the calculation expression of the peak-to-peak value f pp (k) is:

[0085] f pp (k) = |dataf_f(k) - dataf_f(k-1)|

[0086] wherein, dataf_f(k) represents the amplitude of the error signal at the sampling time point k; dataf_f(k-1) represents the amplitude of the error signal at the sampling time point k-1.

[0087] Preferably, the above mechanical resonance detection example is combined, and the preferred example is as follows:

[0088] S21’: Collect the setting signal and the feedback signal;

[0089] S22': Calculate the derivatives of the setpoint signal and the error signal;

[0090] S23': When the set signal and error signal differential... At the same time, record the sampling time datas_t(k), dataf_t(k) and sampling amplitude datas_f(k), dataf_f(k) of the current setting signal and error signal respectively;

[0091] S24': When the differential of the error signal is detected At that time, calculate the harmonic frequency wf(k) and peak-to-peak value f. pp (k):

[0092]

[0093] S25': Determine whether mechanical resonance occurs based on the harmonic frequency wf(k) and the set mechanical resonance range aw~bw.

[0094] When wf(k) > bw, it is considered interference, and the data at sampling time k and time k-1 are deleted.

[0095] When bw > wf(k) > aw, calculate the harmonic frequency ws(t) of the set signal. The calculation expression is: When 0.7wf(k) < ws(t), no mechanical resonance occurs, so the calculation stops and the previously recorded data is deleted; when ws(t) < 0.7wf(k), resonance occurs, and the resonance number f_num is incremented by 1, i.e., f_num = f_num + 1; when f_num > 1 and the current resonance peak value f pp (k) and the previously recorded harmonic peak-to-peak value f pp When the absolute value of the (k-1) change ratio is less than 0.2, mechanical resonance occurs. The resonant frequency is the harmonic frequency wf(k) of the feedback signal, and the peak-to-peak value of the resonance is the peak-to-peak value of the harmonic of the feedback signal, f. pp (k);

[0096] When aw > wf(k), no action is taken and no resonance occurs.

[0097] To illustrate the technical effects of the method of the present invention, a certain position electromechanical servo system platform is used to test the set signal and feedback signal at mechanical resonance, such as... Figure 3 As shown, Figure 3 The horizontal axis represents time, with each point spaced 1ms apart; the vertical axis represents position, with 32768 corresponding to an actual 37.5°. The setpoint and feedback signals are input into the mechanical resonance detection program. The output shows that mechanical resonance has occurred, with a resonant frequency of 4.5Hz and a peak-to-peak value of 107. The waveform after Fourier transform of the data using MATLAB is shown below.Figure 4 As shown in the figure, the horizontal coordinate represents frequency in Hz, and the vertical coordinate represents the amplitude after Fourier transform at the corresponding frequency. It can be seen that the resonance signals are concentrated below 4.6 Hz. In combination with the above-mentioned test results, it can be seen that the method of the present application can be used to detect the resonance signals of the target object. Figures 3-4 It can be seen that the error of the detection result of the method of the present application and the Fourier transform test result meets the requirement, and can meet the actual detection accuracy requirement.

[0098] The above specific embodiments are detailed descriptions of the present application, and cannot be considered as limitations of the specific embodiments of the present application. For ordinary skilled persons in the art to which the present application belongs, without departing from the concept of the present application, a number of simple deductions and substitutions can be made, which should be considered as falling within the protection scope of the present application.

Claims

1. A method of mechanical resonance detection for an electromechanical servo system, the method comprising: The method comprises the following steps: Collecting a set signal in a control instruction for controlling the rudder to reach a target position and a feedback signal reflecting an actual output position of the rudder, and defining a difference between the set signal and the feedback signal as an error signal; Calculating a differential of the set signal and the error signal; When a differential zero point of the set signal or the error signal is detected, recording a sampling time and a sampling amplitude of a corresponding signal; When a differential zero crossing of the error signal is detected, the harmonic frequency wf(k) and the harmonic peak-to-peak value f pp (k) are calculated from the sampling time of the error signal. According to a harmonic frequency and a set mechanical resonance range aw~bw, judging whether mechanical resonance occurs: When wf(k)>bw, it is determined that interference occurs; When bw> wf(k)> aw, the harmonic frequency ws(t) of the set signal is calculated according to the sampling time of the set signal, when kwf(k)<ws(t), mechanical resonance does not occur at this time; when ws(t)<kwf(k), resonance occurs at this time, the resonance number is increased by 1, when the resonance number is greater than 1, and the current harmonic peak-peak value f pp (k) is greater than the last recorded harmonic peak-peak value f pp (k-1), the absolute value of the change ratio is less than m, mechanical resonance occurs at this time, the resonance frequency is the harmonic frequency of the feedback signal, and the harmonic peak-peak value is the harmonic peak-peak value f pp (k) of the error signal; k is a resonance threshold value, and the value range is 0.3-0.9; m is a peak-peak value change threshold value, and is less than 0.

2. When aw>wf(k), it is determined that resonance does not occur.

2. The electromechanical servo system mechanical resonance detection method according to claim 1, characterized by, A calculation expression of the differential of the set signal or the error signal is: wherein, represents a differential of the signal with respect to time; x(k) represents a set signal or an error signal sample value at a sampling time k; x(k-1) represents a set signal or an error signal sample value at a sampling time k-1; and represents a sampling time difference value.

3. The method of claim 1, wherein the mechanical resonance detection is performed by the electromechanical servo system. A calculation expression of the differential zero point of the set signal or the error signal is: wherein denotes the derivative of the setpoint signal or error signal at the sampling instant k; denotes the derivative of the setpoint signal or error signal at the sampling instant k-1.

4. The method of claim 1, wherein the mechanical resonance detection is performed by the electromechanical servo system. A calculation expression of the harmonic frequency wf(k) is: Wherein, dataf_t(k) is a sampling time of the error signal at a sampling time k; dataf_t(k-1) is a sampling time of the error signal at a sampling time k-1.

5. The method of claim 1, wherein, A calculation expression of the harmonic frequency ws(t) is: Wherein, datas_t(k) represents a sampling time of the set signal at a sampling time k; datas_t(k-t) represents a sampling time of the set signal at a sampling time k-t; t is a natural number.

6. The method of claim 1, wherein, Peak-to-peak value f pp The calculation expression of (k) is: f pp (k) = |dataf_f(k) - dataf_f(k-1)| Wherein, dataf_f(k) represents an amplitude of the error signal at a sampling time k; dataf_f(k-1) represents an amplitude of the error signal at a sampling time k-1.

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