Low frequency electromagnetic vibration table system based on induction coil feedback control

Abstract

The invention discloses a low-frequency electromagnetic vibration table system based on induction coil feedback control, the low-frequency electromagnetic vibration table system includes a signal generator, a speed feedback control device, a power amplifier and a low-frequency electromagnetic vibration table; the dynamic coil of the low-frequency vibration table is provided with a driving coil and an induction coil, the speed feedback control device includes a feedback part and a control part, the induced voltage of the induction coil is input into the feedback part, the reference signal output by the signal generator and the feedback signal output by the feedback part are respectively input into the control part, and the control part uses the reference signal and the feedback signal to form a control signal and input into the driving coil. The invention adds an induction coil to the dynamic coil of the vibration table, realizes the vibration table speed extraction by detecting the induced voltage of the induction coil, does not need to directly detect the equivalent resistance of the driving coil, and the speed detection network constructed by the method does not need to connect a resistor in series on the driving coil and build a corresponding analog circuit, thereby simplifying the structure of the speed extraction device.

Description

Technical Field

[0001] The invention relates to a low-frequency electromagnetic vibration table system. Background Art

[0002] Electromagnetic vibration tables have the advantages of wide frequency range, good controllability, and high output waveform accuracy. They are widely used in the fields of simulated vibration environment testing of products and calibration of vibration sensors. In order to further improve the accuracy of the output waveform of the vibration table in the low-frequency range (reduce distortion), it is usually necessary to build a negative feedback control system. Negative feedback control first needs to detect the output vibration signal of the electromagnetic vibration table through a vibration sensor (acceleration, velocity or displacement sensor) or other motion detection device, and then use this signal as a feedback signal to find the difference with the input signal. The deviation signal excites the vibration table after passing through the controller and power amplifier, and finally completes the construction of a closed-loop control system to achieve negative feedback control of the distortion of the vibration table output waveform.

[0003] Chinese patent 201210544489.X proposes a low-frequency electromagnetic vibration table system based on an autonomous relative speed feedback control device, which constructs a negative feedback control system based on a relative speed extraction device. The signal extracted by the relative speed extraction device is passed through a low-pass filter and a first proportional amplifier, and then the difference is calculated with the output signal of the signal generator. The deviation signal is adjusted by a PID controller and then input into a power amplifier. The output of the power amplifier is used as a driving signal of the low-frequency electromagnetic vibration table to drive the vibration table to output vibration.

[0004] The disadvantages of this patent are:

[0005] 1. Since the equivalent DC resistance R of the vibration table drive coil cannot be accurately measured, the acquisition of the parameter K1 in the relative speed extraction device requires a relatively complex adjustment process, which increases the difficulty of using the system; 2. The device extracts the movement of the vibration table by constructing an analog circuit network. Since the resistor must be connected in series in the drive circuit, the heat loss is large and it is not suitable for vibration tables with large acceleration output. In addition, the system is relatively complex, and the low-frequency noise of the analog circuit will cause the vibration table to produce low-frequency drift during movement, reducing the movement accuracy. 3. The output signal size of the relative speed extraction device depends on the parameters of the drive coil. Since the number of turns of the drive coil is limited, the output voltage reflecting the relative speed is relatively low, especially in the lower frequency band, which affects the control effect. Summary of the invention

[0006] The object of the present invention is to provide a low-frequency electromagnetic vibration table system with high motion control accuracy.

[0007] The invention discloses a low-frequency electromagnetic vibration table system based on induction coil feedback control, which is characterized in that: the low-frequency electromagnetic vibration table system includes a signal generator, a speed feedback control device, a power amplifier and a low-frequency electromagnetic vibration table; the moving coil of the low-frequency vibration table is provided with a driving coil and an induction coil, the speed feedback control device includes a feedback part and a control part, the induced voltage of the induction coil is input into the feedback part, the reference signal output by the signal generator and the feedback signal output by the feedback part are respectively input into the control part, and the control part uses the reference signal and the feedback signal to form a control signal which is input into the driving coil.

[0008] Furthermore, the diameter of the induction coil is much smaller than the diameter of the driving coil, thereby increasing the number of turns and the total length of the induction coil and improving the signal-to-noise ratio of the induced voltage generated by the induction coil.

[0009] Furthermore, the induction coil is connected in parallel with the voltage divider unit, and the voltage divider of the voltage divider unit is input into the feedback part. The input impedance of the voltage divider unit tends to infinity. At the same time, the voltage divider resistance is also very large, so as to avoid parasitic current in the induction coil and uncouple the parasitic current in the driving coil, thereby making the induced current flowing through the induction coil as close to 0 as possible, avoiding the interference of the introduction of the induction coil on the current in the driving coil.

[0010] Furthermore, the feedback part of the speed feedback control device includes a signal correction module, a feedback signal adjustment module, and a filter; the control part includes a subtractor and a proportional regulator. The induced voltage of the induction coil is input into the signal correction module after voltage division to obtain a correction signal, and the correction signal is input into the feedback signal adjustment module. The feedback signal adjustment module performs phase compensation and amplitude adjustment on the correction signal in frequency bands in turn to form a system feedback signal. The system feedback signal is input into the subtractor as a subtrahend through the filter, and the signal output by the signal generator is input into the subtractor as a minuend. The output signal of the subtractor enters the proportional regulator, and the output signal of the proportional regulator is used as the control signal of the low-frequency station.

[0011] Furthermore, the feedback signal adjustment module includes a frequency detection unit, an adjustable phase shifter and an adjustable amplifier; the frequency detection unit is composed of a comparator, a counter and a frequency controller connected in sequence, the correction signal and the reference signal are input to the comparator together, the comparator outputs a square wave signal formed by the system input signal and the reference signal, the square wave signal and the digital clock pulse signal are input to the counter together, and the counter outputs the number of cycles N of the system input signal f and the number of cycles N of the digital clock pulse signal s , the frequency controller calculates the frequency value f of the square wave signal f , where f s Indicates the frequency value of the digital clock pulse signal. The frequency controller outputs a phase shift control pulse and an amplitude modulation control pulse; the phase shift control pulse is input into an adjustable phase shifter; and the amplitude modulation control pulse is input into an adjustable amplifier.

[0012] Furthermore, the adjustable phase shifter is composed of two stages of all-pass filters in series, and the frequency detection unit is based on the frequency value f of the system input signal. f Output phase shift control pulse, the phase shift control pulse controls the adjustable phase shifter to perform phase compensation on the feedback signal, reduce the phase difference between the input signal and the feedback signal, and improve the feedback control effect. The steps for determining the phase shift value of the adjustable phase shifter in different frequency bands are as follows:

[0013] S1: Within the working frequency range, input excitation signals of different frequencies to the vibration table and build a negative feedback control system. At different frequencies, adjust the feedback signal in different phases, and detect the accuracy characteristics of the vibration table output signal under the corresponding frequency and feedback signal phase conditions. According to the feedback signal phase that meets the vibration table accuracy requirements, the required phase shift value of the feedback signal at different frequencies can be obtained. The working frequency range of the vibration table is divided into k-1 segments, expressed as f n ≤f<f n+1 , n=1,2,3,...k-1, the segmentation standard is that the phase shift value of the correction signal in this segment is the same; the same phase shift value here means that the difference between the phase shift values ​​of each frequency in the frequency segment is within the allowable deviation range;

[0014] S2: For each frequency segment in turn, take the average value of the phase shift value of each frequency in the frequency segment as the phase shift value of the frequency segment by As f n Phase shift value of frequency segmented adjustable phase shifter;

[0015] S3: For f n The phase shift value of the frequency segment is expressed as:

[0016]

[0017] ; Wherein: R2 is the resistance value of the digital potentiometer in the first stage all-pass filter, and R3 is the resistance value of the digital potentiometer in the second stage all-pass filter;

[0018] S4: Let R2=R3 and combine steps S2 and S3 to obtain the R2 and R3 values ​​corresponding to each frequency segment. For each frequency segment, use the R2 and R3 values ​​as reference to calculate the number of phase shift control pulses that need to be input into the digital potentiometer in the first-stage all-pass filter and the digital potentiometer in the second-stage all-pass filter. The number of phase shift control pulses controls the phase shift value of the corresponding frequency segment generated by the adjustable phase shifter.

[0019] Furthermore, the correction signal is input into an adjustable phase shifter, and an output end of the adjustable phase shifter is connected to an input end of the adjustable amplifier.

[0020] Alternatively, the correction signal is input into an adjustable amplifier, and the output end of the adjustable amplifier is connected to the input end of the adjustable phase shifter.

[0021] Furthermore, the adjustable amplifier is composed of a common-mode proportional amplifier circuit and a voltage divider potentiometer connected in series, which is used to amplify or attenuate the feedback signal and obtain a suitable feedback depth. The steps for determining the gain of the adjustable amplifier in different frequency bands are as follows:

[0022] 1) Within the working frequency range, input excitation signals of different frequencies to the vibration table and build a negative feedback control system. At different frequencies, apply different gains to the feedback signal amplitude, and detect the accuracy characteristics of the vibration table output signal under the corresponding frequency and feedback signal gain conditions. According to the feedback signal gain that meets the vibration table accuracy requirements, the required gain of the feedback signal at different frequencies can be obtained. The working frequency range of the vibration table is divided into (k′-1) segments, expressed as:

[0023] f m ≤f<f m+1 ,m=1,2,3,...k′-1;

[0024] 2) For each frequency segment in turn, take the average value of the gain of each frequency in the current frequency segment as the gain value p of the current frequency segment m ;

[0025] 3) The gain value for each frequency band is expressed as:

[0026]

[0027] Among them, R6 is the resistance value of the feedback resistor in the same-direction proportional amplifier circuit, R7 is the total resistance value of the voltage divider potentiometer, and R 7w is the voltage divider resistance of the voltage divider potentiometer;

[0028] 4) Determine the fixed resistor value R5 of the in-phase proportional amplifier circuit, and judge whether the current frequency segment needs to amplify or attenuate the signal. When the signal needs to be amplified, take R 7w = R7, find R6; with R6 value and R 7w As a reference, the number of amplitude modulation control pulses of the feedback resistor and the number of amplitude modulation control pulses of the voltage divider potentiometer that need to be input into the same-direction proportional amplifier circuit are calculated, so as to control the adjustable amplifier to adjust the amplitude of the feedback signal of the corresponding frequency band;

[0029] When the signal needs to be attenuated, take R6 = 0 and obtain the required R 7w ; With R6 value and R 7wAs a reference, the number of amplitude modulation control pulses of the feedback resistor in the same-direction proportional amplifier circuit and the number of amplitude modulation control pulses of the voltage divider potentiometer are calculated to control the adjustable amplifier to adjust the amplitude of the feedback signal in the corresponding frequency band.

[0030] Furthermore, the speed feedback control device also includes a proportional regulator, which is arranged between the subtractor and the power amplifier.

[0031] The working principle of the present invention is: by winding an induction coil on the part of the moving part in the uniform magnetic field to detect the output vibration speed of the vibration table in the low frequency band, and based on this, a speed feedback control device is constructed, which can adjust the amplitude and phase of the vibration table motion signal detected in the frequency band, and obtain a deviation signal after the difference between the adjusted signal and the input signal. The deviation signal only needs to be input into the power amplifier through a proportional amplification link to drive the vibration table to output a vibration signal that has been precisely negatively feedback controlled. Therefore, the low-frequency electromagnetic vibration table control system proposed by the present invention has a simplified speed detection device, further improves the negative feedback control effect on the accuracy of the output waveform of the low-frequency electromagnetic vibration table, and reduces the difficulty of feedback controller construction and parameter adjustment.

[0032] The advantages of the present invention are:

[0033] 1. An induction coil is added to the dynamic coil of the vibration table, and the vibration table speed is extracted by detecting the induced voltage of the induction coil. There is no need to directly detect the equivalent resistance of the driving coil. In addition, the speed detection network constructed by this method does not need to connect a resistor in series on the driving coil and build a corresponding analog circuit, which simplifies the structure of the speed extraction device. More importantly, it does not introduce low-frequency noise into the driving coil loop, reducing the low-frequency drift of the vibration table during movement.

[0034] 2. The number of turns of the induction coil added to the dynamic coil of the vibration table is large, the output speed voltage signal has a large amplitude, and has a high signal-to-noise ratio, which is conducive to feedback control.

[0035] 3. The correction signal is phase-shifted and amplitude-modulated to form a feedback signal. The feedback signal has a certain degree of phase compensation and an appropriate feedback depth at different frequencies, which improves the accuracy of the output waveform of the vibration table.

[0036] 4. The operating frequency of the vibration table is divided into segments, and each frequency segment is phase-shifted and amplitude-modulated separately. There is no need to perform phase-shifting and amplitude-modulation on each frequency independently, which reduces the difficulty of building the feedback controller and adjusting the parameters. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 It is a structural schematic diagram of the present invention.

[0038] Figure 2It is a schematic diagram of the present invention.

[0039] Figure 3 It is a schematic diagram of the structure of the feedback signal adjustment module of the present invention.

[0040] Figure 4 It is a structural diagram of the adjustable phase shifter and the adjustable amplifier of the present invention. DETAILED DESCRIPTION

[0041] The present invention is further described below in conjunction with specific embodiments, but the present invention is not limited to these specific embodiments. Those skilled in the art should recognize that the present invention covers all possible alternatives, improvements and equivalents within the scope of the claims.

[0042] See also Figure 1 , Figure 2 In Example 1, a low-frequency electromagnetic vibration table system based on induction coil feedback control includes a signal generator, a speed feedback control device, a power amplifier and a low-frequency electromagnetic vibration table; the dynamic coil of the low-frequency vibration table has a driving coil and an induction coil.

[0043] The driving coil and the induction coil are wound together in the same winding groove of the vibration table moving part 1, or the induction coil and the driving coil are wound side by side in different winding grooves of the vibration table moving part, and the induction coil and the driving coil are ensured to be coaxial and in a uniform air gap magnetic field. The speed feedback control device includes a feedback part and a control part, the induced voltage of the induction coil is input to the feedback part, the reference signal output by the signal generator and the system feedback signal u output by the feedback part fb The reference signal and the system feedback signal u are input into the control unit respectively. fb The control signal is input to the driving coil. The diameter of the induction coil is much smaller than the diameter of the driving coil, thereby increasing the number of turns and the total length of the induction coil, and improving the signal-to-noise ratio of the induced voltage generated by the induction coil. The induction coil is connected in parallel with the voltage divider unit, and the voltage divider of the voltage divider unit is input to the feedback part, and the input impedance of the voltage divider unit tends to infinity. The voltage divider unit is used to extract the induced voltage generated at both ends of the induction coil, and process it through the signal correction module to obtain the speed signal u of the vibration table. o The voltage-dividing resistance tends to infinity, avoiding parasitic current in the induction coil and making the driving coil uncoupled from the parasitic current, so that the induced current flowing through the induction coil is as close to 0 as possible, avoiding the interference of the induction coil on the current in the driving coil.

[0044] The principle of detecting the output vibration speed of the low-frequency electromagnetic vibration table based on the induction coil is:

[0045] For a conventional low-frequency electromagnetic vibration table, the drive coil (coil length is l d) can be simplified to resistor R d With inductance L d Series structure. When a sinusoidal voltage u is applied to both ends of the drive coil i , a sinusoidal current i will be generated on the driving coil d Under the action of the uniform air gap magnetic field (magnetic induction intensity is B) generated by the magnetic circuit structure of the vibration table, the driving coil is subjected to the sinusoidal Ampere force and produces sinusoidal vibration. Since the driving coil is fixedly installed with the moving part of the vibration table, the moving part of the vibration table outputs a vibration signal. Considering that the electromagnetic vibration table is a typical electromechanical coupling system, when the moving part of the vibration table outputs vibration, the driving coil generates a vibration signal that is consistent with the vibration speed. is the displacement of the moving parts of the vibration table, The induced electromotive force is proportional to the first derivative of x

[0046] Similarly, the induction coil (length l s ) can also be simplified to resistor R s With inductance L s Series structure. Considering that the induction coil is coaxially installed with the driving coil, when the vibration table moving part outputs vibration, the induction coil Also produces vibration speed Proportional to the induced electromotive force

[0047] According to the steady-state magnetic circuit coupling principle, it can be assumed that the induction coil 12 and the driving coil 11 are coupled to each other through the mutual inductance M. Further, the vibration process of the vibration table moving part 1 can be simplified as the single-degree-of-freedom vibration of the mass-spring-damper system, where m, k, and c are the equivalent mass, equivalent stiffness, and equivalent damping, respectively. Figure 3 As shown, the overall electromechanical coupling relationship is

[0048]

[0049] In the formula, u s is the induced voltage generated at both ends of the induction coil 12, i s is the induced current flowing through the induction coil 12, t is a certain instant in time, and are the first-order derivative and the second-order derivative of x respectively. The voltage divider unit has a large impedance, so that the induced current i flowing through the induction coil 12 s The amplitude is as close to 0 as possible, so it can be considered that i s ≈0, further, when the vibration frequency f is low, there is di s / dt=2πfi s ≈0, avoiding the interference of the induction coil 12 on the output vibration of the vibration table moving part 1. Therefore, formula (1) can be further simplified as

[0050]

[0051] Based on equations 1 and 3 in (2), the vibration table input voltage u can be calculated: i Output vibration speed The transfer function G vi for

[0052]

[0053] In the formula, X(s), U i (s) are x and u respectively i Laplace transform. In addition, based on formula (2), the input voltage u can also be obtained i With the induced voltage u s The transfer function between

[0054]

[0055] Where U s (s) is u s Comparing equation (3) with equation (4), we can get

[0056]

[0057] make

[0058]

[0059] is the transfer function of the signal correction unit. According to formula (5), the output speed signal of the vibration table can be obtained from the output voltage of the induction coil. It can be seen from formula (6) that the signal correction unit is a second-order system, which can be easily realized by an analog circuit or a digital signal processing unit. The induced voltage is proportional to the vibration table speed after being processed by the signal correction module with the transfer function shown in formula (6), realizing the vibration table speed signal u o In the present invention, the low-frequency electromagnetic vibration table vibration speed detection device does not need to connect a pure resistor in series with the vibration table drive coil and construct a complex circuit system, thus avoiding the complex adjustment process of the system parameters, further simplifying the system structure and reducing the difficulty of vibration speed detection.

[0060] like Figure 1 As shown, the feedback part of the speed feedback control device includes a signal correction module, a feedback signal adjustment module, and a filter; the control part includes a subtractor J1 and a proportional regulator. The induced voltage of the induction coil is input into the signal correction module after voltage division to obtain a correction signal. The correction signal is input into the feedback signal adjustment module. The feedback signal adjustment module performs phase compensation and amplitude adjustment on the correction signal in frequency division bands in turn to form a system feedback signal u fb, system feedback signal u fb The signal is input into the subtractor J1 as the subtrahend after the filter, and the signal output by the signal generator is input into the subtractor J1 as the minuend. The output signal of the subtractor J1 enters the proportional regulator, and the output signal of the proportional regulator is used as the control signal of the low-frequency table. When the moving part of the low-frequency electromagnetic vibration table outputs a vibration signal, an induced voltage is generated at both ends of the induction coil. After being processed by the signal correction module, the induced voltage is proportional to the vibration speed of the moving part of the low-frequency electromagnetic vibration table. The detection of the output vibration speed of the moving part is realized by extracting the output voltage of the signal correction module.

[0061] like Figure 3 As shown, the feedback signal adjustment module includes a frequency detection unit and an adjustable phase shifter; the frequency detection unit is composed of a comparator, a counter and a frequency control connected in sequence, the correction signal and the reference signal are input to the comparator together, the comparator outputs a system input signal formed by the correction signal and the reference signal, the square wave signal and the digital clock pulse signal are input to the counter together, and the counter outputs the number of cycles N of the system input signal f and the number of cycles N of the digital clock pulse signal s , the frequency controller calculates the frequency value f of the system input signal f , where f s Indicates the frequency value of the digital clock pulse signal; the phase shift control pulse input is an adjustable phase shifter. The counter and frequency controller are implemented by a digital signal processing unit based on FPGA or DSP.

[0062] The comparator inputs the system input signal of the vibration table and the given reference input signal. When the amplitude of the system input signal is higher than the amplitude of the reference input signal, the comparator outputs a high level, otherwise the comparator outputs a low level. Thus, the comparator outputs a square wave signal, and the frequency of the square wave signal is the same as the system input signal. At this time, the frequency of the square wave signal is unknown, so the square wave signal and the digital clock pulse signal are simultaneously input into the counter. The counter counts the number of cycles of the square wave signal, and the frequency of the digital clock is known. In the same time, the frequency of the square wave can be calculated according to the ratio of the number of cycles of the square wave signal and the number of cycles of the digital clock signal. The frequency of the system input signal is known from the frequency of the square wave, and thus corresponds to the corresponding frequency segment.

[0063] See also Figure 4 The adjustable phase shifter is composed of two stages of all-pass filters in series. The filter resistor in the first stage of the all-pass filter circuit (the filter resistor refers to the resistor in the RC circuit that plays a filtering role) is the first digital potentiometer, and the resistance value is expressed as R2. The filter resistor in the second stage of the all-pass filter circuit is the second digital potentiometer, and the resistance value is expressed as R3. The first digital potentiometer and the second digital potentiometer are both adjustable digital potentiometers. The frequency detection unit detects the frequency value f of the system input signal according to the frequency value ff Output phase shift control pulses, output a corresponding number of phase shift control pulses to control the first digital potentiometer and the second digital potentiometer to output corresponding resistance values, and can achieve 0-360° phase shift for the signal input to the adjustable phase shifter. The steps for determining the phase shift value of the adjustable phase shifter in different frequency bands are as follows:

[0064] S1: Within the working frequency range, input excitation signals of different frequencies to the vibration table and build a negative feedback control system. At different frequencies, adjust the feedback signal in different phases, and detect the accuracy characteristics of the vibration table output signal under the corresponding frequency and corresponding feedback signal phase conditions. According to the feedback signal phase that meets the vibration table accuracy requirements, the required phase shift value of the feedback signal at different frequencies can be obtained. The working frequency range of the vibration table is divided into k-1 segments, represented as f n ≤f<f n+1 , n=1,2,3,...k-1, the segmentation standard is that the phase shift value of the correction signal in this segment is the same; the same phase shift value here means that the difference between the phase shift values ​​of each frequency in the frequency segment is within the allowable deviation range;

[0065] S2: For each frequency segment in turn, take the average value of the phase shift value of each frequency in the frequency segment as the phase shift value of the frequency segment by As f n Phase shift value of frequency segmented adjustable phase shifter;

[0066] S3: For f n The phase shift value of the frequency segment is expressed as:

[0067]

[0068] ; Wherein: R2 is the resistance value of the digital potentiometer in the first stage all-pass filter, and R3 is the resistance value of the digital potentiometer in the second stage all-pass filter;

[0069] S4: Let R2=R3 and combine steps S2 and S3 to obtain the R2 and R3 values ​​corresponding to each frequency segment. For each frequency segment, use the R2 and R3 values ​​as reference to calculate the number of phase shift control pulses that need to be input into the digital potentiometer in the first-stage all-pass filter and the digital potentiometer in the second-stage all-pass filter, and control the phase shift value of the corresponding frequency segment generated by the adjustable phase shifter.

[0070] The frequency detection unit outputs a corresponding number of amplitude modulation control pulses according to the detected system input signal frequency value to control the third digital potentiometer and the fourth digital potentiometer to output corresponding resistance values, thereby adjusting the input adjustable amplifier signal amplitude. The counter outputs the number of cycles N of the system input signal f and the number of cycles N of the digital clock pulse signals , the frequency controller calculates the frequency value f of the system input signal f , where f s Indicates the frequency value of the digital clock pulse signal. The frequency controller outputs the amplitude modulation control pulse; the amplitude modulation control pulse is input into the adjustable amplifier. The adjustable amplifier is formed by connecting the in-phase proportional amplifier circuit and the voltage divider potentiometer in series. The steps for determining the gain of the adjustable amplifier in different frequency bands are as follows:

[0071] 1) Within the working frequency range, input excitation signals of different frequencies to the vibration table and build a negative feedback control system. At different frequencies, apply different gains to the feedback signal amplitude, and detect the accuracy characteristics of the vibration table output signal under the corresponding frequency and feedback signal gain conditions. According to the feedback signal gain that meets the vibration table accuracy requirements, the required gain of the feedback signal at different frequencies can be obtained. The working frequency range of the vibration table is divided into (k′-1) segments, expressed as:

[0072] f m ≤f<f m+1 ,m=1,2,3,...k′-1;

[0073] 2) For each frequency segment in turn, take the average gain of each frequency in the current frequency segment as the gain p of the current frequency segment m ;

[0074] 3) The gain of each frequency band is expressed as:

[0075]

[0076] Among them, R6 is the resistance value of the feedback resistor in the same-direction proportional amplifier circuit, R7 is the total resistance value of the voltage divider potentiometer, and R 7w is the voltage divider resistance of the voltage divider potentiometer;

[0077] 4) Determine the fixed resistor value R5 of the in-phase proportional amplifier circuit, and judge whether the current frequency segment needs to amplify or attenuate the signal. When the signal needs to be amplified, take R 7w = R7, find R6; with R6 value and R 7w As a reference, the number of amplitude modulation control pulses of the feedback resistor and the number of amplitude modulation control pulses of the voltage divider potentiometer that need to be input into the same-direction proportional amplifier circuit are calculated, so as to control the adjustable amplifier to adjust the amplitude of the feedback signal of the corresponding frequency band;

[0078] When the signal needs to be attenuated, take R6 = 0 and obtain the required R 7w ; With R6 value and R 7wAs a reference, the number of amplitude modulation control pulses of the feedback resistor in the same-direction proportional amplifier circuit and the number of amplitude modulation control pulses of the voltage divider potentiometer are calculated to control the adjustable amplifier to adjust the amplitude of the feedback signal in the corresponding frequency band.

[0079] In one embodiment, the correction signal is input to an adjustable phase shifter, and an output end of the adjustable phase shifter is connected to an input end of the adjustable amplifier.

[0080] In another embodiment, the correction signal is input to an adjustable amplifier, and an output terminal of the adjustable amplifier is connected to an input terminal of the adjustable phase shifter.

[0081] The feedback signal adjustment module proposed in the present invention can adaptively adjust the feedback signal of the vibration table control system in frequency bands, so that the feedback signal has an amplitude and phase that meet the needs of the negative feedback control system. The signal adjusted by this device is used as a feedback signal and the difference between it and the input signal from the signal generator is used to obtain a deviation signal. The deviation signal only needs to be input into the power amplifier through a proportional amplification link to drive the vibration table to output a vibration signal that has been precisely negatively feedback controlled. The control system constructed based on this can further improve the negative feedback control effect on the accuracy of the vibration table output waveform, reducing the difficulty of feedback controller construction and parameter adjustment.

[0082] The speed feedback control device further comprises a proportional regulator, which is arranged between the subtractor and the power amplifier.

[0083] The working principle of the present invention is: by winding an induction coil on the part of the moving part in the uniform magnetic field to detect the output vibration speed of the vibration table in the low frequency band, and based on this, a speed feedback control device is constructed, which can adjust the amplitude and phase of the vibration table motion signal detected in the frequency band, and obtain a deviation signal after the difference between the adjusted signal and the input signal. The deviation signal only needs to be input into the power amplifier through a proportional amplification link to drive the vibration table to output a vibration signal that has been precisely negatively feedback controlled. Therefore, the low-frequency electromagnetic vibration table control system proposed by the present invention has a simplified speed detection device, further improves the negative feedback control effect on the accuracy of the output waveform of the low-frequency electromagnetic vibration table, and reduces the difficulty of feedback controller construction and parameter adjustment.

Claims

1. A low-frequency electromagnetic vibration table system based on induction coil feedback control, characterized in that: The invention discloses a low-frequency electromagnetic vibration table system based on induction coil feedback control, characterized in that: the low-frequency electromagnetic vibration table system comprises a signal generator, a speed feedback control device, a power amplifier and a low-frequency electromagnetic vibration table; the dynamic coil of the low-frequency vibration table is provided with a driving coil and an induction coil; the speed feedback control device comprises a feedback part and a control part; the induction voltage of the induction coil is input into the feedback part; the reference signal output by the signal generator and the feedback signal output by the feedback part are respectively input into the control part; the control part uses the reference signal and the feedback signal to form a control signal which is input into the driving coil; the feedback part of the speed feedback control device comprises a signal correction module, a feedback signal adjustment module and a filter; the control part comprises a subtractor and a proportional regulator; the induction voltage of the induction coil is input into the signal correction module after voltage division to obtain a correction signal; the correction signal is input into the feedback signal adjustment module; the feedback signal adjustment module performs phase compensation and amplitude adjustment of the frequency division bands on the correction signal in sequence to form a system feedback signal; the system feedback signal is input into the subtractor as a subtrahend via the filter; the signal output by the signal generator is input into the subtractor as a minuend; the output signal of the subtractor enters the proportional regulator; the output signal of the proportional regulator serves as the control signal of the low-frequency table.

2. The low-frequency electromagnetic vibration table system based on induction coil feedback control according to claim 1 is characterized in that: The diameter of the induction coil is much smaller than the diameter of the driving coil.

3. The low-frequency electromagnetic vibration table system based on induction coil feedback control according to claim 2, characterized in that: The induction coil is connected in parallel with the voltage dividing unit, the voltage divided by the voltage dividing unit is input into the feedback part, and the input impedance of the voltage dividing unit tends to infinity.

4. The low-frequency electromagnetic vibration table system based on induction coil feedback control according to claim 3 is characterized in that: The feedback signal adjustment module includes a frequency detection unit, an adjustable phase shifter and an adjustable amplifier; the frequency detection unit is composed of a comparator, a counter and a frequency controller connected in sequence, the correction signal and the reference signal are input to the comparator together, the comparator outputs a square wave signal formed by the system input signal and the reference signal, the square wave signal and the digital clock pulse signal are input to the counter together, and the counter outputs the number of cycles N of the system input signal f and the number of cycles N of the digital clock pulse signal s , the frequency controller calculates the frequency value f of the square wave signal f , , where f s Indicates the frequency value of the digital clock pulse signal. The frequency controller outputs a phase shift control pulse and an amplitude modulation control pulse; the phase shift control pulse is input into an adjustable phase shifter; and the amplitude modulation control pulse is input into an adjustable amplifier.

5. The low-frequency electromagnetic vibration table system based on induction coil feedback control according to claim 4, characterized in that: The adjustable phase shifter is composed of two stages of all-pass filters connected in series.

6. The low-frequency electromagnetic vibration table system based on induction coil feedback control according to claim 5, characterized in that: The correction signal is input into the adjustable phase shifter, and the output end of the adjustable phase shifter is connected to the input end of the adjustable amplifier; or, the correction signal is input into the adjustable amplifier, and the output end of the adjustable amplifier is connected to the input end of the adjustable phase shifter.

7. The low-frequency electromagnetic vibration table system based on induction coil feedback control according to claim 6, characterized in that: The adjustable amplifier is composed of a common-phase proportional amplifier circuit and a voltage divider potentiometer connected in series.

8. The low-frequency electromagnetic vibration table system based on induction coil feedback control according to claim 7, characterized in that: The speed feedback control device further comprises a proportional regulator, which is arranged between the subtractor and the power amplifier.

Images