A narrowband transducer broadband driving system and method based on variable structure control

Abstract

The present invention relates to a narrowband transducer broadband driving system based on variable structure control and a method thereof. The system comprises: a signal source, an amplifier module, a comparator module, a negative feedback gain module, a positive feedback gain module, a narrowband transducer module, a feedback signal gain module and a decision module; wherein the amplifier module, the comparator module, the positive feedback gain module, the narrowband transducer module and the feedback signal gain module constitute a positive feedback loop of the system; the amplifier module, the comparator module, the negative feedback gain module, the narrowband transducer module and the feedback signal gain module constitute a negative feedback loop of the system; by switching the positive feedback loop and the negative feedback loop at high speed, the transient response generated by the narrowband transducer during operation is close to the ideal transient response, thereby achieving the purpose of effectively reducing the transient response time, improving the data transmission rate and having strong robustness.

Description

Technical Field

[0001] The present invention relates to the technical field of narrowband transducer broadband driving, and in particular to a narrowband transducer broadband driving system based on variable structure control and a method thereof. Background Art

[0002] With the complex changes in the international situation, more and more attention has been paid to the advanced waveform design of low-frequency active (LFA) sonar. The attenuation coefficient of low-frequency sound waves in seawater is smaller than that of high-frequency sound waves, and its propagation distance is farther. Therefore, in order to increase the detection range of active sonar and improve the distance of underwater detection, hydroacoustic equipment needs a lower operating frequency and processes signals in a wider frequency band, which requires hydroacoustic transducers to develop in the direction of low frequency and broadband. Due to its strong concealment, coded waveform sonar has multi-path robustness and the ability of high-speed and high-resolution underwater networks, making phase-coded waveforms a high-quality option for modern sonar systems. However, as a key component of the system, the mechanical quality factor of the low-frequency transducer must be high enough to take into account the transmission efficiency, and the low-frequency transducer usually works in a resonant state, which is bound to cause the bandwidth of the low-frequency transducer to be relatively narrow, thereby affecting the bandwidth of the entire sonar transmission system. Therefore, solving the problem of broadband transmission of narrowband transducers has become a task of outstanding practical significance.

[0003] Common acoustic transducers based on piezoelectric technology today utilize a narrow bandwidth around the resonant frequency due to transients in the transducer that have a long decay time due to electromechanical inertia within the sensor. In most cases, resonant transducers do not allow for short broadband pulses to be achieved on a stable front end, which would result in significant errors in the signal delay measurement. Figure 1 The experimental system structure shown in the figure is used to observe the transient response time of the narrowband transducer under broadband transmission. Figure 2 The frequency of the signal source in (a) is adjusted to Figure 3 The signal source frequency is shown, Figure 3 The signal source frequency is about 73Hz. Figure 3 It can be seen from the figure that under the excitation of the signal source, the transducer enters a steady-state response after nearly 10 carrier cycles after oscillation. Figure 3 It can be seen that after the signal source changes its phase once, it takes nearly 15 carrier cycles for the acoustic output of the transducer to be synchronized with the driving message signal. Therefore, it can be determined that the transient response time of the measured transducer is as long as 1.67-2.5 milliseconds. This long transient limit the performance of the underwater acoustic system.

[0004] In order to overcome the transient response of narrowband transducers under broadband transmission, Wang and Tang et al. tried to use a specially designed pulse amplitude modulation drive signal to excite the transducer, which is an application of feedforward control. The defects of this method are: the damping of resonance depends entirely on the dynamic characteristics of the transducer, and is easily affected by the differences in different transducer parameters and the changes in the parameters of the surrounding environment over time, resulting in the inability to reduce the transient response. Since there is no feedback signal prompt, the control signal cannot be corrected in time when the dynamic characteristics of the transducer change; F. Tong et al. suggested designing a complementary transducer transfer function to pre-filter the drive signal. In theory, this is an effective solution. The compensated transducer response has a certain delay, but the defects of this method are: when the complementary model parameters change or are inaccurately estimated, the dynamic characteristics of the transducer cannot be completely offset. In practical applications, there are changes with the sound wave propagation environment, and the transducer impedance cannot be dynamically measured. Therefore, the complementary model cannot be corrected, resulting in matching failure; LF Brown et al. used broadband transducers to implement coding and modulation schemes, and improved the transducer process manufacturing, including thin films (polymer films), micro-electromechanical (EMFi ) and improvements in micromachined sensors. These devices can be used in applications requiring short pulse widths and high resolution and shorter paths. They demonstrated digital data air communications in the United States over several meters. The modulation was based on binary coding and used a polymer film transducer with a center frequency of 250kHz, with an approximate available bandwidth of 200kHz. The structure of these sensors is similar, that is, they can only be driven by applying a high voltage to them through contact electrodes; the defects of this method are: the 200V peak-to-peak electrical excitation on the transmitter produces a received signal with an amplitude of 5mV within a range of 1.2 meters. Some applications actually obtain wider bandwidth at the expense of gain. Due to its low energy electromechanical conversion efficiency, the practicality of this technology for use in target applications is low.

[0005] Currently, broadband transmission of narrowband transducers is a challenging problem, and broadband transducers are usually required to achieve the fast phase changes required for phase encoding (such as BPSK). Higher frequency broadband sensors can provide sufficient bandwidth, but they are more expensive and require high-voltage drive circuits, which are very costly. Narrowband transducers are more common and cheaper, and have many applications in communication and positioning systems. If the basic ringing problem can be solved, high-Q resonant narrowband transducers can have a significant performance improvement in related field applications. The present invention designs a narrowband transducer broadband drive system and method based on variable structure control, which reduces the transient response time of system dynamics in the target application through feedback control, is robust to parameter changes, has direct application in improving the performance of all communication and detection systems, and is physically realized. Summary of the invention

[0006] The technical problem to be solved by the present invention is to provide a narrow-band transducer broadband driving system and method based on variable structure control, which can effectively reduce transient response, improve system robustness and applicability, and reduce costs.

[0007] In a first aspect, the technical solution adopted by the present invention is a narrowband transducer broadband driving system based on variable structure control, comprising:

[0008] A signal source; the signal source is used to provide an electrical signal;

[0009] Amplifier module; the amplifier module is used to receive the electrical signal and amplify the electrical signal to obtain an initial signal Fr;

[0010] Comparator module; the comparator module is used to receive the initial signal Fr and the feedback signal Hy * and the initial signal Fr and the feedback signal Hy * Perform subtraction to obtain the error signal e;

[0011] Negative feedback gain module; the negative feedback gain module is used to receive the error signal e and apply negative feedback gain to the error signal e to obtain a negative feedback signal u1;

[0012] Positive feedback gain module; the positive feedback gain module is used to receive the error signal e and apply a positive feedback gain to the error signal e to obtain a positive feedback signal u2;

[0013] Narrowband transducer module; the narrowband transducer module is used to receive the negative feedback signal u1 or the positive feedback signal u2, and output the acoustic signal y and the equivalent electrical signal y of the acoustic signal y * ;

[0014] Feedback signal gain module; the feedback signal gain module is used to receive the equivalent electrical signal y * And amplify to obtain the feedback signal Hy * , and the feedback signal Hy * Feedback to the comparator module;

[0015] Wherein, the amplifier module, the comparator module, the positive feedback gain module, the narrowband transducer module and the feedback signal gain module constitute a positive feedback loop of the system; the amplifier module, the comparator module, the negative feedback gain module, the narrowband transducer module and the feedback signal gain module constitute a negative feedback loop of the system;

[0016] A decision module; the decision module is used to receive the error signal e, calculate the error speed estimate Δe / ΔT and the ideal system response sw according to the error signal e, and switch the positive feedback loop and the negative feedback loop in the system according to the error speed estimate Δe / ΔT and the ideal system response sw; the error speed estimate is expressed as: Δe / ΔT≡(e(n)–e(n–1)) / ΔT, wherein e(n) represents the discrete expression after sampling the error signal e, and the sampling interval is ΔT, that is, e(n)≡e(nΔt); e(n-1) represents the sample point of the previous sampling period relative to e(n); the ideal system response sw is expressed as: sw≈(int(e(n))-e(n–1)) / ΔT+ctran*e(n–1); wherein the constant ctran represents the slope of the ideal system transient response sw on the phase plane.

[0017] The beneficial effects of the present invention are as follows: by adopting the above-mentioned narrow-band transducer broadband driving system based on variable structure control, the transient response generated during the operation of the narrow-band transducer is made close to the ideal transient response through a high-speed switching variable structure mechanism, thereby achieving the purpose of effectively reducing the transient response time, improving the data transmission rate, and having strong robustness; and, the system is based on broadband transmission realized by a narrow-band transducer, and has low cost and a wide range of applications.

[0018] Preferably, the specific principle of switching the positive feedback loop and the negative feedback loop in the system according to the error speed estimate Δe / ΔT and the ideal system response sw is as follows: when the error speed estimate Δe / ΔT is greater than 0 and the ideal system response sw is greater than 0, the system switches to the negative feedback loop operation; when the error speed estimate Δe / ΔT is greater than 0 and the ideal system response sw is less than or equal to 0, the system switches to the positive feedback loop operation; when the error speed estimate Δe / ΔT is less than or equal to 0 and the ideal system response sw is greater than 0, the system switches to the positive feedback loop operation; when the error speed estimate Δe / ΔT is less than or equal to 0 and the ideal system response sw is less than or equal to 0, the system switches to the negative feedback loop operation; by adopting this principle, the transient response generated in the working process of the narrow-band transducer can be made close to the ideal transient response through the variable structure mechanism of high-speed switching, so as to achieve the purpose of effectively reducing the transient response time.

[0019] In a second aspect, the technical solution adopted by the present invention is a method for driving a narrowband transducer with broadband based on variable structure control, the method comprising the following steps:

[0020] S1, obtain the error signal e through the comparator module, the error signal e is the result of the initial signal Fr and the feedback signal Hy *The initial signal Fr is obtained by amplifying the electrical signal provided by the signal source through the amplifier module, and the feedback signal Hy * The equivalent electrical signal y output by the narrowband transducer module * After magnification, we get:

[0021] S2, the decision module receives the error signal e, calculates the error speed estimate Δe / ΔT and the ideal system response sw according to the error signal e, and determines the switching between the positive feedback loop and the negative feedback loop in the system according to the error speed estimate Δe / ΔT and the ideal system response sw: when the error speed estimate Δe / ΔT is greater than 0 and the ideal system response sw is greater than 0, the system switches to the negative feedback loop and enters step S3; when the error speed estimate Δe / ΔT is greater than 0 and the ideal system response sw is less than or equal to 0, the system switches to the positive feedback loop and enters step S6; when When the error speed estimate Δe / ΔT is less than or equal to 0 and the ideal system response sw is greater than 0, the system switches to a positive feedback loop and enters step S6; when the error speed estimate Δe / ΔT is less than or equal to 0 and the ideal system response sw is less than or equal to 0, the system switches to a negative feedback loop and enters step S3; wherein the positive feedback loop is composed of an amplifier module, a comparator module, a positive feedback gain module, a narrowband transducer module and a feedback signal gain module; the negative feedback loop is composed of an amplifier module, a comparator module, a negative feedback gain module, a narrowband transducer module and a feedback signal gain module;

[0022] S3, when the system switches to negative feedback loop operation, the negative feedback gain module receives the error signal e, and applies negative feedback gain to the error signal e to obtain a negative feedback signal u1;

[0023] S4, the narrowband transducer module receives the negative feedback signal u1, and outputs the acoustic signal y and the equivalent electrical signal y of the acoustic signal y * ;

[0024] S5. The feedback signal gain module receives the equivalent electrical signal y * And amplify to obtain the feedback signal Hy * , the feedback signal Hy * Feedback to the comparator module, and return to step S1;

[0025] S6. When the system switches to the positive feedback loop operation, the positive feedback gain module receives the error signal e, and applies the positive feedback gain to the error signal e to obtain the positive feedback signal u2;

[0026] S7, the narrowband transducer module receives the positive feedback signal u2, and outputs the acoustic signal y and the equivalent electrical signal y of the acoustic signal y* ;

[0027] S8, the feedback signal gain module receives the equivalent electrical signal y * And amplify to obtain the feedback signal Hy * , the feedback signal Hy * Feedback is sent to the comparator module, and the process returns to step S1.

[0028] By adopting the above-mentioned narrow-band transducer broadband driving method based on variable structure control, the transient response generated in the working process of the narrow-band transducer is made close to the ideal transient response through the variable structure mechanism of high-speed switching, so as to achieve the purpose of effectively reducing the transient response time, improving the data transmission rate, and having strong robustness; moreover, the system is based on broadband transmission realized by a narrow-band transducer, and its cost is low and its application range is wide. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 It is a system block diagram of a narrowband transmitting transducer based on phase modulation and a broadband receiving front end described in the background technology of the present invention;

[0030] Figure 2 It is a schematic diagram of the time domain response of the narrowband transducer described in the background technology of the present invention when driven by a high symbol rate signal;

[0031] Figure 3 It is a schematic diagram of the time domain response of the narrowband transducer described in the background technology of the present invention after reducing the symbol rate;

[0032] Figure 4 A system block diagram of a narrowband transducer broadband driving system based on variable structure control according to the present invention;

[0033] Figure 5 Schematic diagram of discrete phase plane trajectory and corresponding error-time response expected in the present invention; wherein, Figure 5 (a) Schematic diagram of the expected discrete phase plane trajectory. Figure 5 (b) shows the corresponding error-time response diagram;

[0034] Figure 6 It is a schematic diagram of the effect of the error signal phase plane trajectory after adjusting the sw slope three times in the present invention;

[0035] Figure 7 It is a schematic diagram of the convergence speed of the system error transient response corresponding to the error signal phase plane trajectory after adjusting the sw slope three times in the present invention;

[0036] Figure 8 A flow chart of a narrowband transducer broadband driving method based on variable structure control according to the present invention;

[0037] Fig. 9 It is a schematic diagram of performing feedback switching by acquiring the phase trajectory of the sampling error in the present invention;

[0038] Fig.10 is a schematic diagram of an equivalent circuit model of a conventional narrow-band transducer;

[0039] Fig.11 is a schematic diagram of an equivalent circuit model of a narrow-band transducer in the present invention;

[0040] Fig.12 It is a circuit diagram of a feedback signal gain module in the driving system of the present invention;

[0041] Fig.13 It is a schematic diagram of the structure of a digital system for sampling an error signal in the present invention;

[0042] Fig.14 This is a schematic diagram of the test results of the SW algorithm in the present invention;

[0043] Fig.15 Schematic diagram of the hardware structure of the switch driver in the present invention;

[0044] As shown in the figure: 1. Reference signal generator; 2. Signal source; 3. Carrier; 4. Narrowband transducer; 5. Broadband hydrophone; 6. Signal source; 7. Amplifier module; 8. Decision module; 9. Negative feedback gain module; 10. Narrowband transducer module; 11. Positive feedback gain module; 12. Feedback signal gain module; 13. Comparator module. DETAILED DESCRIPTION

[0045] The invention will be further described below with reference to the accompanying drawings and in combination with specific implementations, so that those skilled in the art can implement the invention with reference to the description. The protection scope of the invention is not limited to the specific implementations.

[0046] In the description of the embodiments of the present application, it is also necessary to explain that, unless otherwise clearly specified and limited, the terms "set", "install", "connect", and "connect" 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 this application can be understood according to specific circumstances.

[0047] The present invention relates to a narrowband transducer broadband driving system based on variable structure control, such as Figure 4 As shown, including:

[0048] A signal source; the signal source is used to provide an electrical signal;

[0049] Amplifier module; the amplifier module is used to receive the electrical signal and amplify the electrical signal to obtain an initial signal Fr;

[0050] Comparator module; the comparator module is used to receive the initial signal Fr and the feedback signal Hy * and the initial signal Fr and the feedback signal Hy * Perform subtraction to obtain the error signal e;

[0051] Negative feedback gain module; the negative feedback gain module is used to receive the error signal e and apply negative feedback gain to the error signal e to obtain a negative feedback signal u1;

[0052] Positive feedback gain module; the positive feedback gain module is used to receive the error signal e and apply a positive feedback gain to the error signal e to obtain a positive feedback signal u2;

[0053] Narrowband transducer module; the narrowband transducer module is used to receive the negative feedback signal u1 or the positive feedback signal u2, and output the acoustic signal y and the equivalent electrical signal y of the acoustic signal y * ;

[0054] Feedback signal gain module; the feedback signal gain module is used to receive the equivalent electrical signal y * And amplify to obtain the feedback signal Hy * , and the feedback signal Hy * Feedback to the comparator module;

[0055] Wherein, the amplifier module, the comparator module, the positive feedback gain module, the narrowband transducer module and the feedback signal gain module constitute a positive feedback loop of the system; the amplifier module, the comparator module, the negative feedback gain module, the narrowband transducer module and the feedback signal gain module constitute a negative feedback loop of the system;

[0056] A decision module; the decision module is used to receive the error signal e, calculate the error speed estimate Δe / ΔT and the ideal system response sw according to the error signal e, and determine the switching between the positive feedback loop and the negative feedback loop in the system according to the error speed estimate Δe / ΔT and the ideal system response sw; the error speed estimate is expressed as: Δe / ΔT≡(e(n)–e(n–1)) / ΔT, where e(n) is a discrete expression of the error signal e after sampling, and the sampling interval is ΔT, that is, e(n)≡e(nΔt); e(n-1) is a sample point relative to the sampling period before e(n). The ideal system response sw is expressed as: sw≈(int(e(n))-e(n–1)) / ΔT+ctran*e(n–1); where the constant ctran is the slope of the ideal system transient response sw on the phase plane.

[0057] Furthermore, the specific principle of switching the positive feedback loop and the negative feedback loop in the system according to the error speed estimate Δe / ΔT and the ideal system response sw is as follows: when the error speed estimate Δe / ΔT is greater than 0 and the ideal system response sw is greater than 0, the system switches to the negative feedback loop; when the error speed estimate Δe / ΔT is greater than 0 and the ideal system response sw is less than or equal to 0, the system switches to the positive feedback loop; when the error speed estimate Δe / ΔT is less than or equal to 0 and the ideal system response sw is greater than 0, the system switches to the positive feedback loop; when the error speed estimate Δe / ΔT is less than or equal to 0 and the ideal system response sw is less than or equal to 0, the system switches to the negative feedback loop; by adopting this principle, the transient response generated during the operation of the narrowband transducer can be made close to the ideal transient response through a variable structural mechanism of high-speed switching, thereby effectively reducing the transient response time.

[0058] Figure 4 The narrowband transducer broadband driving system based on variable structure control proposed by the present invention is presented in the form of a block diagram, which consists of two proportional feedback control loops and a decision module. One proportional feedback control loop is composed of a loop consisting of an amplifier module, a comparator module, a negative feedback gain module, a narrowband transducer module and a feedback signal gain module, which is used to provide negative feedback, and the other proportional feedback control loop is composed of a loop consisting of an amplifier module, a comparator module, a positive feedback gain module, a narrowband transducer module and a feedback signal gain module, which is used to provide positive feedback.

[0059] In the present invention, the realization of the ideal system response sw is based on the discrete phase plane design. Defined by the error signal e≡(Fr–Hy*), the error signal e is discretized with a sampling period ΔT, and the trajectory of the sample points (Δe / ΔT, e(n-1))) forms a discrete phase plane trajectory, as shown in Figure 5 The diagram shows the expected discrete phase plane trajectory and time response. Where Δe / ΔT is the error velocity estimate, Δe / ΔT≡(e(n)–e(n–1)) / ΔT, where e(n)≡e(nΔt); the sampling frequency should be much higher than the system resonant frequency to obtain a full description of the system dynamics; the ideal system response sw is the boundary of the decision module: sw≈(int(e(n))-e(n–1)) / ΔT+ctran*e(n–1); where the constant ctran is a positive slope related to the decay time of the first-order transient response; as shown in Figure 5 As shown, sw is located in the second and fourth quadrants of the phase plane, which is divided by the boundary conditions e(n–1) = 0 and sw = 0 and has four regions. Negative feedback is applied in the first and third quadrants, and positive feedback will be activated if the trajectory is detected in the second and fourth quadrants. Figure 6 and Figure 7 The comparison diagrams of the phase plane and the corresponding time domain response are given respectively. Figure 6 and Figure 7 It can be seen that in order to make the phase error of the variable structure control transducer drive system follow the designed first-order system response to decay to the minimum, the transducer error convergence speed is improved by increasing the SW slope ctran. The larger the SW slope, the faster the transient decay speed.

[0060] In order to achieve the minimum delay of the system, the present invention also proposes a narrowband transducer broadband driving method based on variable structure control, such as Figure 8 As shown, the method comprises the following steps:

[0061] S1, obtain the error signal e through the comparator module, the error signal e is the result of the initial signal Fr and the feedback signal Hy * The initial signal Fr is obtained by amplifying the electrical signal provided by the signal source through the amplifier module, and the feedback signal Hy * The equivalent electrical signal y output by the narrowband transducer module * After magnification, we get:

[0062] S2, the decision module receives the error signal e, calculates the error speed estimate Δe / ΔT and the ideal system response sw according to the error signal e, and determines the switching between the positive feedback loop and the negative feedback loop in the system according to the error speed estimate Δe / ΔT and the ideal system response sw: when the error speed estimate Δe / ΔT is greater than 0 and the ideal system response sw is greater than 0, the system switches to the negative feedback loop and enters step S3; when the error speed estimate Δe / ΔT is greater than 0 and the ideal system response sw is less than or equal to 0, the system switches to the positive feedback loop and enters step S6; when When the error speed estimate Δe / ΔT is less than or equal to 0 and the ideal system response sw is greater than 0, the system switches to a positive feedback loop and enters step S6; when the error speed estimate Δe / ΔT is less than or equal to 0 and the ideal system response sw is less than or equal to 0, the system switches to a negative feedback loop and enters step S3; wherein the positive feedback loop is composed of an amplifier module, a comparator module, a positive feedback gain module, a narrowband transducer module and a feedback signal gain module; the negative feedback loop is composed of an amplifier module, a comparator module, a negative feedback gain module, a narrowband transducer module and a feedback signal gain module;

[0063] S3, when the system switches to negative feedback loop operation, the negative feedback gain module receives the error signal e, and applies negative feedback gain to the error signal e to obtain a negative feedback signal u1;

[0064] S4, the narrowband transducer module receives the negative feedback signal u1, and outputs the acoustic signal y and the equivalent electrical signal y of the acoustic signal y * ;

[0065] S5. The feedback signal gain module receives the equivalent electrical signal y * And amplify to obtain the feedback signal Hy * , the feedback signal Hy * Feedback to the comparator module, and return to step S1;

[0066] S6. When the system switches to the positive feedback loop operation, the positive feedback gain module receives the error signal e, and applies the positive feedback gain to the error signal e to obtain the positive feedback signal u2;

[0067] S7, the narrowband transducer module receives the positive feedback signal u2, and outputs the acoustic signal y and the equivalent electrical signal y of the acoustic signal y * ;

[0068] S8, the feedback signal gain module receives the equivalent electrical signal y * And amplify to obtain the feedback signal Hy * , the feedback signal Hy *Feedback is sent to the comparator module, and the process returns to step S1.

[0069] like Fig. 9 As shown, the need for real-time computation in the design of variable structure control systems based on error sampling samples is explained. Here, the case where sw is steep to achieve faster transient convergence is mainly considered. As sw is steepened, the angle between sw and the saddle point asymptote (dashed-dotted line) becomes narrower. In the figure, x represents the sampling error phase trajectory mapped on the coordinates (e(n-1), ed(n)). The detection sensitivity to time delay in samples based on feedback dynamic switching is a key parameter for the performance of variable structure control systems.

[0070] The equivalent circuit model of a conventional narrowband transducer consists of two parts: the electrical branch and the acoustic branch. Fig.10 As shown. The electric branch is the plate of the transducer's electroacoustic conversion, and the acoustic branch is a lumped element model of a quartz crystal, represented by a basic series resonant circuit. In the implementation of the system, in order to provide error measurement for the decision module, the parallel plate capacitor in the electric branch is used to offset the influence of the acoustic output measurement in the transducer equivalent circuit model, so the Fig.11 The design in is used as the equivalent circuit model of the narrowband transducer in the present invention, that is, the parallel equivalent electric branch is constructed by adopting the idea of ​​instrument amplifier, the complete current passing through the transducer is compared with the current of the equivalent electric branch, and the current signal of the acoustic branch is extracted as the equivalent acoustic output signal; Fig.12 As shown, in order to realize the feedback signal gain module in the driving system, a circuit schematic diagram of the feedback signal gain module in the driving system is specifically given.

[0071] In the process of system implementation, a digital system is used to complete the sampling of the error signal e and implement the switching line algorithm (SW algorithm) in the variable structure control method, such as Fig.13 As shown, the internal AD of the single-chip microcomputer is used to complete the sampling of the error signal e, and the feedback switching decision signal of the digital system is output by the general IO of the single-chip microcomputer.

[0072] SW algorithm is based on Figure 8 The algorithm is implemented in the process, and the function of the algorithm is mainly reflected in the quadrant division of the required feedback dynamic characteristics on the phase plane. The sw algorithm uses a sinusoidal signal with the same center frequency as the transducer, such as Fig.14 (a). By adjusting the sampling frequency, find a suitable sampling rate, such as Fig.14 (c) The error signal gradient required to construct the phase diagram is obtained by first-order backward difference. Fig.14 (d) It can be seen that the dynamic range of the gradient signal that can be generated by a 12-bit AD is only 7 bits long. Therefore, the dynamic range of the error signal and its gradient is balanced by the sampling period ΔT, thereby improving the effective resolution of the error gradient estimation.

[0073] The following is an explanation of the implementation of the SW algorithm (taking a 40kHz transducer as an example):

[0074] For a sinusoidal error signal:

[0075] e(t)= A*cos(ωo*t) (1)

[0076] Among them, A is Fig.14 The peak amplitude of the test signal sampled in. Specifically, it is expressed as A*1LSB (mV); ωo is the center frequency of the sensor (radians), and its gradient is also sinusoidal with a phase shift of 90 degrees; derivative:

[0077] de / dt = -A*sin(ωo*t) (2)

[0078] Using the Taylor series (truncated after the linear term), the gradient estimate is given by:

[0079] e(n) – e(n–1) ≈ ΔT*(de / dt)|t=nΔT (3)

[0080] Amplitude of the sine wave:

[0081] Δemax = ΔT*A*ωo (4)

[0082] Given sampling frequencies fs = 1 / ΔT = 40 MHz, 20 MHz and 10 MHz, ωo = (2*π*40 kHz) rad / sec, A = 1241 (decimal), this means that for 40 MHz, Δemax = 7.79≈8, for 20 MHz it is 15.59≈16, and for 10 MHz it is 31.18≈31. These values ​​are consistent with Fig.14 (a)~ Fig.14 (c) Consistent. Fig.14 (e) shows the phase plane trajectory before scaling the velocity estimate by the sampling frequency. In order for control to be feasible, the sampling frequency must be much larger than the sensor frequency, i.e., ΔT<<(2*π) / ωo. Therefore, the magnitude of the gradient estimate will usually be much smaller than the error dynamic range. The dynamic range distribution of the error signal conversion result is shown in Fig.14 (d) where the difference (gradient) between adjacent samples of the system error signal is very small. By using the sampling period as a scaling factor in conjunction with the switching line gradient ΔT and ctran, a similar dynamic range can be obtained for the error signal and its velocity. Since the feedback switching condition is based on the sign change of sw, it can be scaled arbitrarily. By dividing by the constant ctran, the sw condition can be redefined as:

[0083] sw=ed / (ctran*ΔT)+e(n-1) (5)

[0084] Here, from Fig.14 In (a), a sampling period ΔT of 25ns is selected. The sw constant represents the time required for the error signal to recover to almost zero when a phase change occurs. The transient time Ttran of the error in the sensor system reflects the phase difference between the demand signal and the sensor output. In this design, the time constant is selected as half of the carrier signal period. Therefore, the resulting value of ctran can be calculated by substituting the center frequency fo = 40kHz of the transducer circuit model into equation (6):

[0085] ctran=1 / (2*To)=2*fo≈80 kHz (6)

[0086] For equation (5), this produces a coefficient of about 500. Due to the fixed-point microprocessor, this coefficient is an integer value. Therefore, the final switching line equation becomes:

[0087] sw = 500*ed + e(n–1) (7)

[0088] The above content introduces the implementation and functions of digital system microcontrollers, focusing on the impact of limited precision and the balanced application of system sampling frequency to phase plane resolution.

[0089] In the present invention, the negative feedback gain A of the negative feedback gain module is functionally implemented by an inverting amplifier. Symmetrically, the implementation of the positive feedback gain B of the positive feedback gain module can be a non-inverting amplifier. In this design, two driver structures are integrated together using a single operational amplifier to reduce design complexity. The electronic control switch device between the two feedback system structures. Fig.15 As shown in Figure 1, the single-pole double-position analog switch selected in this design includes a control input (IN) and two switch terminals, normally open (NO) and normally closed (NC), which are connected to the inputs of the two signal paths of the driver, and the common port (COM) of the analog switch is grounded.

[0090] Based on the idea of ​​transient elimination, the present invention proposes a simplified variable structure control method with strong robustness to improve the dynamic characteristics of low-frequency narrowband transducers in underwater acoustic systems. The narrowband ultrasonic technology based on transient elimination can effectively improve the problem of data rate reduction caused by transients under the premise of meeting a relatively long transmission coverage range. In high-performance active and passive joint detection systems, the pulse width directly affects the vertical resolution of detection. The narrower the pulse width, the higher the detection resolution. A few detection systems use modulation and coding schemes commonly used in radio communications, but only achieve very limited detection accuracy. The primary influencing factor is the narrowband characteristics of the transducer. This narrowband characteristic is generated by the inertia of the transducer itself, and brings a delay of up to more than a dozen carrier cycles to the instantaneous phase change of the response of the phase modulation coding detection system, and leads to a reduction in detection resolution. Existing literature shows that low-frequency narrowband acoustic transducers used for long-distance underwater acoustic communication and detection have the same transient problem. Research on narrowband sound source emission technology based on transient elimination can effectively improve the problem of pulse width caused by transients and improve detection accuracy under the premise of meeting a relatively long transmission coverage range, and has great application value in the field of deep-sea detection.

Claims

1. A narrowband transducer broadband driving system based on variable structure control, characterized in that: include: Signal source; The signal source is used to provide an electrical signal; Amplifier module; The amplifier module is used to receive the electrical signal and amplify the electrical signal to obtain an initial signal Fr; Comparator module; the comparator module is used to receive the initial signal Fr and the feedback signal Hy * and the initial signal Fr and the feedback signal Hy * Perform subtraction to obtain the error signal e; Negative feedback gain module; the negative feedback gain module is used to receive the error signal e and apply negative feedback gain to the error signal e to obtain a negative feedback signal u1; Positive feedback gain module; the positive feedback gain module is used to receive the error signal e and apply a positive feedback gain to the error signal e to obtain a positive feedback signal u2; Narrowband transducer module; the narrowband transducer module is used to receive the negative feedback signal u1 or the positive feedback signal u2, and output the acoustic signal y and the equivalent electrical signal y of the acoustic signal y * ; Feedback signal gain module; the feedback signal gain module is used to receive the equivalent electrical signal y * And amplify to obtain the feedback signal Hy * , and the feedback signal Hy * Feedback to the comparator module; Wherein, the amplifier module, the comparator module, the positive feedback gain module, the narrowband transducer module and the feedback signal gain module constitute a positive feedback loop of the system; the amplifier module, the comparator module, the negative feedback gain module, the narrowband transducer module and the feedback signal gain module constitute a negative feedback loop of the system; A decision module; the decision module is used to receive the error signal e, calculate the error speed estimate Δe / ΔT and the ideal system response sw according to the error signal e, and switch the positive feedback loop and the negative feedback loop in the system according to the error speed estimate Δe / ΔT and the ideal system response sw; the error speed estimate is expressed as: Δe / ΔT≡(e(n)–e(n–1)) / ΔT, wherein e(n) represents the discrete error signal e after sampling, the sampling interval is ΔT, that is, e(n)≡e(nΔt), and e(n-1) is the sample point of the sampling period before e(n); the ideal system response sw is expressed as: sw≈(int(e(n))-e(n–1)) / ΔT+ctran*e(n–1); wherein the constant ctran represents the slope of the ideal system transient response sw on the phase plane; The specific principle of switching the positive feedback loop and the negative feedback loop in the system according to the error speed estimate Δe / ΔT and the ideal system response sw is as follows: when the error speed estimate Δe / ΔT is greater than 0 and the ideal system response sw is greater than 0, the system switches to the negative feedback loop operation; when the error speed estimate Δe / ΔT is greater than 0 and the ideal system response sw is less than or equal to 0, the system switches to the positive feedback loop operation; when the error speed estimate Δe / ΔT is less than or equal to 0 and the ideal system response sw is greater than 0, the system switches to the positive feedback loop operation; when the error speed estimate Δe / ΔT is less than or equal to 0 and the ideal system response sw is less than or equal to 0, the system switches to the negative feedback loop operation; by adopting this principle, the transient response generated in the working process of the narrowband transducer can be made close to the ideal transient response through the variable structure mechanism of high-speed switching, so as to achieve the purpose of effectively reducing the transient response time.

2. A method for broadband driving a narrowband transducer based on variable structure control, the method being implemented by a broadband driving system for a narrowband transducer based on variable structure control as claimed in claim 1, the method comprising the following steps: S1, obtain the error signal e through the comparator module, the error signal e is the result of the initial signal Fr and the feedback signal Hy * Make a difference and get; among them, The initial signal Fr is obtained by amplifying the electrical signal provided by the signal source through the amplifier module, and the feedback signal Hy * The equivalent electrical signal y output by the narrowband transducer module * After magnification, we get: S2, the decision module receives the error signal e, calculates the error speed estimate Δe / ΔT and the ideal system response sw according to the error signal e, and determines the switching between the positive feedback loop and the negative feedback loop in the system according to the error speed estimate Δe / ΔT and the ideal system response sw: when the error speed estimate Δe / ΔT is greater than 0 and the ideal system response sw is greater than 0, the system switches to the negative feedback loop and enters step S3; when the error speed estimate Δe / ΔT is greater than 0 and the ideal system response sw is less than or equal to 0, the system switches to the positive feedback loop and enters step S6; when When the error speed estimate Δe / ΔT is less than or equal to 0 and the ideal system response sw is greater than 0, the system switches to a positive feedback loop and enters step S6; when the error speed estimate Δe / ΔT is less than or equal to 0 and the ideal system response sw is less than or equal to 0, the system switches to a negative feedback loop and enters step S3; wherein the positive feedback loop is composed of an amplifier module, a comparator module, a positive feedback gain module, a narrowband transducer module and a feedback signal gain module; the negative feedback loop is composed of an amplifier module, a comparator module, a negative feedback gain module, a narrowband transducer module and a feedback signal gain module; S3, when the system switches to negative feedback loop operation, the negative feedback gain module receives the error signal e, and applies negative feedback gain to the error signal e to obtain a negative feedback signal u1; S4, the narrowband transducer module receives the negative feedback signal u1, and outputs the acoustic signal y and the equivalent electrical signal y of the acoustic signal y * ; S5. The feedback signal gain module receives the equivalent electrical signal y * And amplify to obtain the feedback signal Hy * , the feedback signal Hy * Feedback to the comparator module, and return to step S1; S6. When the system switches to the positive feedback loop operation, the positive feedback gain module receives the error signal e, and applies the positive feedback gain to the error signal e to obtain the positive feedback signal u2; S7, the narrowband transducer module receives the positive feedback signal u2, and outputs the acoustic signal y and the equivalent electrical signal y of the acoustic signal y * ; S8, the feedback signal gain module receives the equivalent electrical signal y * And amplify to obtain the feedback signal Hy * , the feedback signal Hy * Feedback is sent to the comparator module, and the process returns to step S1.

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