Mechanical resonance detection method for electromechanical servo system

Abstract

The invention discloses a mechanical resonance detection method for an electromechanical servo system, and belongs to the technical field of steering engine mechanical resonance detection, and the method comprises the steps: collecting a setting signal, setting an error signal of the signal and a feedback signal, calculating the differential of the signal in real time, and when the signal differential zero crossing point is detected, a vibration source possibly exists at the moment. Recording the time and the amplitude when the differential crosses the zero point; calculating a current waveform harmonic frequency according to historical record information, and when a waveform in a mechanical harmonic range is detected and a set signal frequency is far less than a mechanical resonant frequency, considering that a feedback signal contains harmonic waves; when two adjacent harmonic peak values of the feedback signal are detected to be close, it is judged that mechanical resonance has occurred, otherwise, it is judged that no mechanical resonance has occurred, the whole detection process only relates to differential calculation and simple mathematical calculation, the implementation mode is simple, and compared with Fourier transform, the calculation complexity is greatly reduced, and the detection accuracy is improved. And the requirement of mechanical resonance on a hardware calculation function is reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of mechanical resonance detection of steering gears, and in particular to a mechanical resonance detection method of an electromechanical servo system. Background Art

[0002] Electromechanical servo systems usually adopt the form of motor + harmonic reducer + load. Due to the gap and flexibility of the transmission mechanism, the system itself has a certain resonant frequency, that is, the 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, that is, the servo system will have severe jitter near the target value. Mechanical resonance not only affects the performance of the servo system, but may even damage the transmission device and burn the motor. When the UAV is actually flying, the safety of the electromechanical servo system is directly related to the safety of the entire machine, but the mechanical resonance is related to the flexibility of the servo system structure and the load inertia. Under different working conditions, its mechanical resonance frequency is different. It is difficult to test on the ground whether the servo system will have mechanical resonance when the UAV is actually flying. Therefore, real-time detection of whether the servo system has mechanical resonance is very important for the safety of the UAV.

[0003] At present, the detection of mechanical resonance of the servo mainly adopts the Fourier transform method. This method first collects the feedback signal and setting signal of the servo. The feedback signal is the signal detected from the actual output position of the servo, which can reflect the actual working state of the servo. The setting signal is the ideal or expected output in the control command, which is used to indicate the target position that the servo needs to reach. Then, the feedback signal and the setting signal are Fourier transformed, and then the result of the Fourier transform is used to confirm whether the servo has mechanical resonance. The Fourier transform calculation is complex. The servo system has a high control frequency and generates a lot of data. The real-time Fourier transform of the feedback signal and the setting signal requires high hardware computing power. At the same time, there are many interference signals in the actual application scenario, which are not theoretical sinusoidal signals. It is easy to misjudge the detection of mechanical resonance of the servo through Fourier transform. Summary of the invention

[0004] The purpose of the present invention is to overcome the problems of the prior art and provide a method for detecting mechanical resonance of an electromechanical servo system.

[0005] The object of the present invention is to achieve the following technical solution: a method for detecting mechanical resonance of an electromechanical servo system, the method comprising the following steps:

[0006] Collect the given signal in the control command used to control the servo to reach the target position, and the feedback signal reflecting the actual output position of the servo, and define the difference between the set signal and the feedback signal as the error signal;

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

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

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

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

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

[0012] 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), no mechanical resonance occurs. When ws(t)<kwf(k), resonance occurs and the resonance number is increased by 1. When the resonance number is greater than 1 and the current resonance peak value f pp (k) and the peak value of the harmonics recorded last time f pp When the absolute value of the change ratio (k-1) is less than m, mechanical resonance occurs, 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 of the feedback signal. pp (k); k is the resonance threshold, ranging from 0.3 to 0.9; m is the peak-to-peak change threshold, less than 0.2;

[0013] When aw>wf(k), no resonance occurs.

[0014] In one example, the differential calculation expressions of the setting signal and the error signal are:

[0015]

[0016] in, represents the differential of a signal over time; x(k) represents the sampling value of a setting signal or an error signal at sampling time k; x(k-1) represents the sampling value of a setting signal or an error signal at sampling time k-1; Indicates the sampling time difference.

[0017] In one example, the calculation expression of the differential zero crossing point of the setting signal or the error signal is:

[0018]

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

[0020] In one 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 one example, the calculation expression of the harmonic frequency ws(t) is:

[0024]

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

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

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

[0028] Among them, 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 one example, before collecting the setting signal and feedback signal of the servo, it is also included to determine whether there is mechanical resonance in the servo system, including the following sub-steps:

[0030] Establishing the mathematical model of servo system:

[0031]

[0032] Among them, J1 is the equivalent inertia of the servo motor, screw, reducer and coupling converted to the primary side; J2 is the load equivalent secondary side inertia; Ks and Cs are the equivalent transmission stiffness and damping coefficient respectively; B1 and B2 represent the viscous friction coefficients on both sides respectively; Tc1 and Tc2 are the Coulomb friction torques on both 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 speed difference (ω1-ω2) between the primary and secondary sides;

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

[0034]

[0035] According to the transfer function, the servo system has conjugate poles and the resonant frequency ω is:

[0036]

[0037] It should be further explained that the technical features corresponding to the above examples can be combined or replaced with each other to form a new technical solution.

[0038] Compared with the prior art, the present invention has the following beneficial effects:

[0039] The present invention collects the setting signal, the error signal of the setting signal and the feedback signal, calculates the differential of the signal in real time, and when the signal differential passes through zero, there may be a vibration source at this time, and records the time and amplitude when the differential passes through zero. According to the historical record information, the harmonic frequency of the current waveform is calculated. After the waveform that meets the mechanical harmonic range is detected, the setting and error harmonic frequencies are detected to be similar. If the frequencies are similar, mechanical resonance does not occur at this time, otherwise it is determined that mechanical resonance has occurred. The entire detection process only involves differential calculations and simple mathematical calculations, and the implementation method is simple. Compared with Fourier transform, the calculation complexity is greatly reduced, and it can quickly detect whether mechanical resonance occurs, which reduces the requirements of mechanical resonance on hardware calculation functions. It has versatility and can be transplanted to other servo systems, and has extensibility. Further, the method of the present invention uses differential identification and judgment of mechanical resonance, and does not need to rely on Fourier transform to perform frequency domain analysis on the signal. Therefore, for complex interference signals existing in actual application scenarios, it has high anti-interference ability, is not easy to misjudge, and has better robustness and accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] The specific implementation methods of the present invention are further described in detail below in conjunction with the accompanying drawings. The accompanying drawings described herein are used to provide a further understanding of the present application and constitute a part of the present application. The same reference numerals are used in these drawings to represent the same or similar parts. The schematic embodiments of the present application and their descriptions are used to explain the present application and do not constitute improper limitations on the present application.

[0041] Figure 1 A transmission relationship diagram of a servo control system provided as an example of the present invention;

[0042] Figure 2 A method flow chart provided for an example of the present invention;

[0043] Figure 3 A schematic diagram of measured mechanical resonance data of a steering gear provided as an example of the present invention;

[0044] Figure 4 An amplitude-frequency curve diagram after Fourier transformation provided for an example of the present invention. DETAILED DESCRIPTION

[0045] The technical solution of the present invention is described clearly and completely below in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0046] In the description of the present invention, it should be noted that the directions or positional relationships indicated by "center", "up", "down", "left", "right", "vertical", "horizontal", "inside", "outside", etc. are directions or positional relationships based on the drawings, which are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention. In addition, the use of ordinal numbers (e.g., "first and second", "first to fourth", etc.) is to distinguish objects, and is not limited to this order, and cannot be understood as indicating or implying relative importance.

[0047] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, "installation", "connection" and "connection" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0048] In addition, the technical features involved in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0049] A method for detecting mechanical resonance of an electromechanical servo system. Before executing the mechanical resonance detection step, it is necessary to determine whether the servo system has mechanical resonance. The present invention is implemented by establishing a mathematical model of the servo system. The implementation method is as follows:

[0050] S11 Establish the mathematical model of the servo system: The transmission relationship of the servo control system can usually be adopted as follows Figure 1The two-mass structure shown in the figure is used for dynamic modeling. The servo motor, screw, reducer and coupling are converted into the equivalent inertia of the primary side, denoted as J1; 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 clearance. B1 and B2 are used to represent the viscous friction coefficients on both sides respectively; Tc1 and Tc2 are the Coulomb friction torques on both 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 speed difference (ω1-ω2) between the primary and secondary sides.

[0051] Without considering the effect of the gap, according to the principle of dynamics, we can get:

[0052]

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

[0054]

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

[0056]

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

[0058]

[0059] The existence of mechanical resonance in the servo system can be proved by establishing a mathematical model of the servo system, but a specific value cannot be calculated. Therefore, the present invention further adopts differential identification and judgment of mechanical resonance.

[0060] In one example, a method for detecting mechanical resonance of an electromechanical servo system includes the following steps:

[0061] S21: Collect setting signals and feedback signals.

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

[0063] S22: Calculate the differential of the setting signal and the error signal.

[0064] S23: When the differential zero crossing point of the setting signal or the error signal is detected, the sampling time and 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 of the error signal is detected, the harmonic frequency wf(k) of the error signal and the harmonic peak-to-peak value f of the error signal are calculated according to the sampling time of the error signal. pp (k);

[0067] S25: Determine whether mechanical resonance occurs based on the harmonic frequency wf(k) and the set mechanical resonance range aw~bw:

[0068] When wf(k)>bw, it is considered as interference, and the data recorded at sampling time k and time 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), no mechanical resonance occurs and the resonance frequency f_num is reset to zero. When ws(t)<kwf(k), resonance occurs and the resonance frequency is increased by 1, that is, the resonance frequency f_num=f_num+1. When the resonance frequency f_num is greater than 1 and the current resonance peak value f pp (k) and the peak value of the harmonics recorded last time f pp When the absolute value of the change ratio (k-1) is less than m, mechanical resonance occurs, 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 of the feedback signal. pp (k); k is the resonance threshold, ranging from 0.3 to 0.9, preferably 0.7; m is the peak-to-peak change threshold, less than 0.2;

[0070] When aw>wf(k), no processing is done and no resonance occurs.

[0071] In one example, the differential calculation expressions of the setting signal and the feedback signal are:

[0072]

[0073] in, represents the differential of the signal over time; x(k) represents the sampling value of the setting signal or feedback signal at sampling time k; x(k-1) represents the sampling value of the setting signal or feedback signal at sampling time k-1; Indicates the sampling time difference.

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

[0075]

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

[0077] In one 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 sampling time k; dataf_t(k-1) is the sampling time of the error signal at sampling time k-1.

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

[0081]

[0082] Among them, datas_t(k) represents the sampling time of the signal set at sampling time k; datas_t(kt) represents the sampling time of the signal set at sampling time kt.

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

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

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

[0086] Among them, 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.

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

[0088] S21': Collect setting signals and feedback signals;

[0089] S22': Calculate the differential of the setting signal and the error signal;

[0090] S23': When the setting signal and the error signal are differentiated When the current setting signal and error signal sampling time datas_t(k), dataf_t(k) and sampling amplitude datas_f(k), dataf_f(k) are recorded respectively;

[0091] S24': When the error signal differential is detected Calculate the harmonic frequency wf(k) and the peak-to-peak value f pp (k):

[0092]

[0093] S25': Determine whether mechanical resonance occurs according to the harmonic frequency wf(k) combined with the set mechanical resonance range aw~bw:

[0094] When wf(k)>bw, it is considered as interference, and the data recorded 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, and the calculation expression is: When 0.7wf(k)<ws(t), no mechanical resonance occurs, the calculation is stopped and the previously recorded data is deleted; when ws(t)<0.7wf(k), resonance occurs, and the resonance number f_num is increased by 1, that is: f_num=f_num+1; when f_num>1 and the current resonance peak value f pp (k) and the peak value of the harmonics recorded last time f pp When the absolute value of the change ratio (k-1) is less than 0.2, mechanical resonance occurs, and the resonance frequency is the harmonic frequency wf(k) of the feedback signal, and the resonance peak-to-peak value is the harmonic peak-to-peak value of the feedback signal f pp (k);

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

[0097] To illustrate the technical effect of the method of the present invention, a certain position electromechanical servo system platform is used to test the setting signal and feedback signal during mechanical resonance. Figure 3 As shown, Figure 3 The horizontal axis is time, and the interval between each point is 1ms; the vertical axis represents the position, and 32768 corresponds to the actual 37.5°. The set signal and feedback signal are input into the mechanical resonance detection program. The output result shows that mechanical resonance has occurred at this time, with a resonance frequency of 4.5Hz and a peak-to-peak value of 107. After Fourier conversion of the data using matlab, the waveform is as follows Figure 4 As shown in the figure, the horizontal axis represents the frequency in Hz, and the vertical axis represents the amplitude after Fourier transform at the corresponding frequency. It can be seen that the resonant signal is concentrated below 4.6Hz. Figure 3-Figure 4 It can be seen that the error between the detection result of the method of the present invention and the Fourier transform test result meets the requirement and can meet the actual detection accuracy requirement.

[0098] The above specific implementation methods are detailed descriptions of the present invention. It cannot be determined that the specific implementation methods of the present invention are limited to these descriptions. For ordinary technicians in the technical field to which the present invention belongs, several simple deductions and substitutions can be made without departing from the concept of the present invention, which should be regarded as belonging to the protection scope of the present invention.

Claims

1. A method for detecting mechanical resonance of an electromechanical servo system, characterized in that: The following steps are involved: Collect the given signal in the control command used to control the servo to reach the target position, and the feedback signal reflecting the actual output position of the servo, and define the difference between the set signal and the feedback signal as the error signal; Calculate the differential of the set signal and error signal; When the differential zero crossing point of the set signal or error signal is detected, the sampling time and sampling amplitude of the corresponding signal are recorded; When the differential zero crossing point of the error signal is detected, the harmonic frequency wf(k) of the error signal and the harmonic peak-to-peak value f are calculated according to the sampling time of the error signal. pp (k); Determine whether mechanical resonance occurs based on the harmonic frequency combined with the set mechanical resonance range aw~bw: When wf(k)>bw, it is considered as interference; 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), no mechanical resonance occurs. When ws(t)<kwf(k), resonance occurs and the resonance number is increased by 1. When the resonance number is greater than 1 and the current resonance peak value f pp (k) and the peak value of the harmonics recorded last time f pp When the absolute value of the change ratio (k-1) is less than m, mechanical resonance occurs, 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 of the feedback signal. pp (k); k is the resonance threshold, ranging from 0.3 to 0.9; m is the peak-to-peak change threshold, less than 0.2; When aw>wf(k), no resonance occurs.

2. The method for detecting mechanical resonance of an electromechanical servo system according to claim 1, characterized in that: The differential calculation expressions of the setting signal and error signal are: in, represents the differential of a signal over time; x(k) represents the sampling value of a setting signal or an error signal at sampling time k; x(k-1) represents the sampling value of a setting signal or an error signal at sampling time k-1; Indicates the sampling time difference.

3. The method for detecting mechanical resonance of an electromechanical servo system according to claim 1, characterized in that: The calculation expression of the differential zero crossing point of the set signal or error signal is: in, represents the differential of the setting signal or error signal at sampling time k; Represents the differential of the setting signal or error signal at sampling time k-1.

4. The method for detecting mechanical resonance of an electromechanical servo system according to claim 1, characterized in that: The calculation expression of the harmonic frequency wf(k) is: 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.

5. The method for detecting mechanical resonance of an electromechanical servo system according to claim 1, characterized in that: The calculation expression of the harmonic frequency ws(t) is: Wherein, datas_t(k) represents the sampling time of the signal set at sampling time k; datas_t(kt) represents the sampling time of the signal set at sampling time kt; and t is a natural number.

6. The method for detecting mechanical resonance of an electromechanical servo system according to claim 1, characterized in that: Peak-to-peak value f pp The calculation expression of (k) is: f pp (k)=|dataf_f(k)-dataf_f(k-1)| Among them, 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.

7. The method for detecting mechanical resonance of an electromechanical servo system according to claim 1, characterized in that: Before collecting the setting signal and feedback signal of the servo, it is also necessary to determine whether there is mechanical resonance in the servo system, including the following sub-steps: Establishing the mathematical model of servo system: Among them, J1 is the equivalent inertia of the servo motor, screw, reducer and coupling converted to the primary side; J2 is the load equivalent secondary side inertia; Ks and Cs are the equivalent transmission stiffness and damping coefficient respectively; B1 and B2 represent the viscous friction coefficients on both sides respectively; Tc1 and Tc2 are the Coulomb friction torques on both 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 speed difference (ω1-ω2) between the primary and secondary sides; According to the mathematical model of the servo system, the transfer function G(s) is calculated: According to the transfer function, the servo system has conjugate poles and the resonant frequency ω is:

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