Sound probe contact force and ultrasonic cooperative control method based on adaptive control

Abstract

The invention belongs to the technical field of nondestructive testing and intelligent robot control, and discloses a sound probe contact force and ultrasonic cooperative control method based on self-adaptive control, which specifically comprises the following steps of: acquiring an ultrasonic waveform to extract an echo signal, calculating characteristic parameters of the echo signal, and calculating the characteristic parameters of the echo signal; judging whether the pressing force is proper or not according to the characteristic parameters of the echo signals; acquiring actual pressing force of the sound probe, calculating a pressing force error based on the expected pressing force, and judging whether to enter an adjustment mode or not; the adjustment mode comprises adjustment of pressing force and adjustment of the position of the sound probe; based on model reference self-adaptive control, calculating a self-adaptive gain parameter, and adjusting the pressing force; according to pressing force error feedback, dynamic characteristics of expected pressing force control are established, and the position of the sound probe is adjusted; after the mode adjustment is finished, the ultrasonic waveform is collected again, echo signals are extracted, and whether the pressing force is appropriate or not is calculated and judged; the problems of unstable probe control and signal distortion easily caused in the prior art are solved.

Description

Technical Field

[0001] The present invention belongs to the technical field of non-destructive testing and intelligent robot control, and particularly relates to a method for collaborative control of acoustic probe contact force and ultrasound based on adaptive control. Background Art

[0002] Large pressure vessels and pipelines, critical facilities for energy storage and transportation and chemical production, rely on stable acoustic coupling between ultrasonic probes and the surface being tested. Factors such as complex surface deformation, coating variations, and dynamic scanning disturbances lead to nonlinear coupling between contact force and acoustic impedance. Insufficient contact force can cause signal attenuation due to air gaps, while excessive contact force can lead to probe wear or false defect signals. Traditional manual operation or fixed threshold control methods make it difficult to achieve dynamic matching between the two.

[0003] While existing automated ultrasonic testing systems have improved inspection efficiency through robotic arm trajectory planning and force sensing technology, their control strategies often rely on preset pressure thresholds or force / position decoupling modes, making them difficult to adapt to dynamic disturbances such as sudden changes in surface curvature and mechanical vibration. Under such conditions, rigid contact control can easily cause the probe to vibrate or detach from the inspection surface, while static force control strategies reduce defect detection sensitivity due to offsets in the acoustic beam incident angle. Furthermore, the static matching mechanism between ultrasonic excitation parameters (such as frequency and gain) and contact force lacks real-time response to dynamic changes in acoustic impedance, leading to fluctuations in the signal-to-noise ratio and affecting the accuracy of defect quantification. Consequently, existing technologies are prone to unstable probe control and signal distortion. Summary of the Invention

[0004] In view of the shortcomings of the existing technology, the purpose of the present invention is to provide a method for collaborative control of acoustic probe contact force and ultrasound based on adaptive control, which solves the problems in the existing technology that easily lead to unstable probe control and signal distortion.

[0005] The purpose of the present invention can be achieved through the following technical solutions:

[0006] A method for collaboratively controlling acoustic probe contact force and ultrasound based on adaptive control specifically comprises the following steps:

[0007] Collect ultrasonic waveforms to extract echo signals, calculate characteristic parameters of the echo signals, and determine whether the pressing force is appropriate based on the characteristic parameters of the echo signals;

[0008] Collect the actual pressing force of the acoustic probe, calculate the pressing force error based on the expected pressing force, and determine whether to enter the adjustment mode;

[0009] The adjustment mode includes adjusting the pressing force and adjusting the position of the acoustic probe;

[0010] Based on model reference adaptive control, the adaptive gain parameters are calculated to adjust the pressing force;

[0011] According to the pressure error feedback, the dynamic characteristics of the desired pressure control are established and the position of the acoustic probe is adjusted;

[0012] After the adjustment mode ends, the ultrasonic waveform is collected again to extract the echo signal, and the pressing force is calculated and judged to be appropriate; if the pressing force is judged to be appropriate, the adjustment is successful; if the pressing force is judged to be inappropriate, iterative adjustment is performed until the pressing force is judged to be appropriate.

[0013] Characteristic parameters include signal amplitude A actual , signal-to-noise ratio SNR and bottom echo intensity R b .

[0014] Calculating the characteristic parameters of the echo signal and judging whether the pressing force is appropriate based on the characteristic parameters of the echo signal specifically includes the following steps:

[0015] Signal amplitude A actual The calculation formula is:

[0016]

[0017] Among them, A max is the signal amplitude under the optimal pressing force; α is the adjustment factor; F ref is the expected pressing force, the value of which is determined by the distance between the acoustic probe and the wall; F actual is the actual pressing force;

[0018] The calculation formula for the signal-to-noise ratio SNR is:

[0019]

[0020] Among them, P signal is the signal power; P noise is the noise power;

[0021] Bottom wall echo intensity R b The calculation formula is as follows:

[0022]

[0023] Preset signal amplitude threshold β1, signal-to-noise ratio threshold β2 and bottom wall echo intensity threshold range β3;

[0024] If the signal amplitude A actual If it is less than the signal amplitude threshold β1, the pressing force is inappropriate;

[0025] If the signal-to-noise ratio SNR is less than the signal-to-noise ratio threshold β2, the pressing force is inappropriate;

[0026] If the bottom echo intensity R b If the pressure deviates from the threshold range β3, the pressing force is inappropriate.

[0027] Based on the expected pressing force, the pressing force error is calculated to determine whether to enter the adjustment mode. The specific steps include the following:

[0028] Calculate the pressure error. The calculation formula for the pressure error is as follows:

[0029] e(t)=|F ref -F actual | (4)

[0030] Where, e(t) is the pressure error at time t;

[0031] Preset the error threshold ε;

[0032] If the pressure error e(t) is greater than the error threshold ε, it is determined that the adjustment mode has been entered.

[0033] Based on the model reference adaptive control, the adaptive gain parameters are calculated and the pressing force is adjusted. The specific steps include:

[0034] The adaptive gain parameter θ is calculated as follows:

[0035]

[0036] θ(t)=θ(0)-γ∫e(t)F actual dt (6)

[0037] Where θ(t) represents the adaptive gain parameter at time t;

[0038] represents the first-order derivative of θ(t) at time t;

[0039] θ(0) represents the initial value of the adaptive gain parameter;

[0040] γ is the learning rate, which determines the speed of adaptive gain parameter adjustment;

[0041] Adjusted pressing force F cmd The calculation formula is as follows:

[0042] F cmd =F ref +θ(t)·φ(x) (7)

[0043] Among them, φ(x) is the state vector, which contains two state information: the pressure error and the pressure change rate. The expression of φ(x) is:

[0044]

[0045] in, It is the rate of change of the actual pressing force, reflecting the changing trend of the pressing force over time.

[0046] Based on the pressure error feedback, the dynamic characteristics of the desired pressure control are established and the position of the acoustic probe is adjusted. The specific steps include the following:

[0047] The dynamic characteristics of the desired pressure control are established. The expression of the dynamic characteristics is as follows:

[0048]

[0049] Among them, M is the equivalent mass, B is the damping coefficient, and K is the stiffness coefficient;

[0050] Calculate the position x of the acoustic probe after adjustment current , the calculation formula is as follows:

[0051]

[0052] in, is the velocity of the acoustic probe position, describing the instantaneous motion state of the probe;

[0053] is the acceleration of the acoustic probe position, which represents the dynamic adjustment rate of the acoustic probe under force feedback control;

[0054] Δt is the time step, which represents the time interval between two adjacent sampling moments;

[0055] x previous This is the position of the acoustic probe before adjustment.

[0056] Beneficial effects of the present invention:

[0057] By adjusting the probe pressure and signal amplitude A in real time actual , signal-to-noise ratio SNR and bottom echo intensity R b The system can realize contact force tracking and acoustic coupling optimization by combining characteristic parameters, solve the problems of probe jitter and signal distortion under traditional control, and significantly improve the accuracy and stability of defect detection under dynamic working conditions. BRIEF DESCRIPTION OF THE DRAWINGS

[0058] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0059] Figure 1 This is a flow chart of the coordinated control of the acoustic probe contact force and ultrasound of the present invention.

[0060] Figure 2It is a structural schematic diagram of the acoustic probe contact force and ultrasound coordinated control model of the present invention. DETAILED DESCRIPTION

[0061] The following will clearly and completely describe the technical solutions in the embodiments of the present invention 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 making any creative efforts shall fall within the scope of protection of the present invention.

[0062] like Figure 1 As shown, a method for collaborative control of acoustic probe contact force and ultrasound based on adaptive control specifically includes the following steps:

[0063] Collect ultrasonic waveforms to extract echo signals, calculate characteristic parameters of the echo signals, and determine whether the pressing force is appropriate based on the characteristic parameters of the echo signals;

[0064] Collect the actual pressing force of the acoustic probe, calculate the pressing force error based on the expected pressing force, and determine whether to enter the adjustment mode;

[0065] The adjustment mode includes adjusting the pressing force and adjusting the position of the acoustic probe;

[0066] Based on model reference adaptive control (MRAC), the adaptive gain parameters are calculated to adjust the pressing force;

[0067] According to the pressure error feedback, the dynamic characteristics of the desired pressure control are established and the position of the acoustic probe is adjusted;

[0068] After the adjustment mode ends, the ultrasonic waveform is collected again to extract the echo signal, and the pressing force is calculated and judged to be appropriate; if the pressing force is judged to be appropriate, the adjustment is successful; if the pressing force is judged to be inappropriate, iterative adjustment is performed until the pressing force is judged to be appropriate.

[0069] Characteristic parameters include signal amplitude A actual , signal-to-noise ratio SNR and bottom echo intensity R b .

[0070] Calculating the characteristic parameters of the echo signal and judging whether the pressing force is appropriate based on the characteristic parameters of the echo signal specifically includes the following steps:

[0071] Signal amplitude A actual The calculation formula is:

[0072]

[0073] Among them, A max is the signal amplitude under the optimal pressing force; α is the adjustment factor; Fref is the expected pressing force, the value of which is determined by the distance between the acoustic probe and the wall; F actual is the actual pressing force;

[0074] The calculation formula for the signal-to-noise ratio SNR is:

[0075]

[0076] Among them, P signal is the signal power; P noise is the noise power;

[0077] Bottom wall echo intensity R b The calculation formula is as follows:

[0078]

[0079] Preset signal amplitude threshold β1, signal-to-noise ratio threshold β2 and bottom wall echo intensity threshold range β3;

[0080] If the signal amplitude A actual If it is less than the signal amplitude threshold β1, the pressing force is inappropriate;

[0081] If the signal-to-noise ratio (SNR) is less than the signal-to-noise ratio threshold β2, the pressing force is inappropriate; and if the signal-to-noise ratio (SNR) is less than the signal-to-noise ratio threshold, it indicates poor contact or insufficient pressing force.

[0082] If the bottom echo intensity R b If it deviates from the threshold range β3, the pressing force is inappropriate;

[0083] Among them, R b ≈1 indicates moderate pressure;

[0084] R b <<1 means the pressing force is too small;

[0085] R b >1 may indicate excessive pressure and signal distortion;

[0086] In this application, the following five methods can be used to determine whether the pressing force is appropriate:

[0087] Judgment method 1: Determine whether the probe pressing force is good by the change in signal amplitude. When the probe pressing force is insufficient, the contact surface is poorly coupled, resulting in obstructed ultrasonic energy transmission, a decrease in echo signal amplitude, and even signal loss. When the probe pressing force is moderate, ultrasonic energy can be transmitted well, the echo signal amplitude is maximized, and the signal is clear. Excessive pressing force can cause slight deformation of the ultrasonic propagation path, which may cause sound beam deviation, mode conversion, or signal distortion, affecting defect identification.

[0088] Judgment method 2: Determine whether the probe pressing force is good by the echo waveform. When the coupling is good, the ultrasonic waveform is clear, the echo has a high amplitude and a stable envelope shape; when the coupling is poor or the pressing force is insufficient, the waveform may have stray signals, signal distortion, and even the bottom echo may become weak or disappear; when the pressing force is too large, the waveform may be distorted, especially when using an oblique probe or phased array detection, the sound beam angle may change, affecting the reflected signal;

[0089] Judgment method three: judge whether the probe pressing force is good by the signal-to-noise ratio. If the pressing force is insufficient, poor contact may introduce more noise, reducing the signal-to-noise ratio. Appropriate pressing force will result in clear signal, low noise, and the highest signal-to-noise ratio. If the pressing force is too great, coupling agent extrusion or surface deformation may cause unstable signal, affecting the signal-to-noise ratio.

[0090] Judgment method 4: Determine whether the probe pressing force is good by the bottom echo. When the pressing force is insufficient, the bottom echo is weak or unstable, and may disappear intermittently; when the pressing force is appropriate, the bottom echo is clear and the amplitude is stable; when the pressing force is too large, the bottom echo may change phase or weaken energy, which is more obvious in thickness measurement or phased array ultrasonic testing.

[0091] Judgment method five: The probe coupling status is reflected by the C-scan and B-scan images in phased array ultrasound (PAUT) and automated ultrasonic testing (AUT). Insufficient pressure may result in discontinuous signal areas on the C-scan and severe B-scan signal attenuation. Moderate pressure results in a uniform image and stable signal. Excessive pressure may result in localized signal attenuation or waveform distortion.

[0092] Based on the expected pressing force, the pressing force error is calculated to determine whether to enter the adjustment mode. The specific steps include the following:

[0093] Calculate the pressure error. The calculation formula for the pressure error is as follows:

[0094] e(t)=|F ref -F actual | (4)

[0095] Where, e(t) is the pressure error at time t;

[0096] Preset the error threshold ε;

[0097] If the pressure error e(t) is greater than the error threshold ε, it is determined that the adjustment mode has been entered.

[0098] Based on the model reference adaptive control, the adaptive gain parameters are calculated and the pressing force is adjusted. The specific steps include:

[0099] The calculation formula of the adaptive gain parameter is as follows:

[0100]

[0101] θ(t)=θ(0)-γ∫e(t)F actual dt (6)

[0102] Where θ(t) represents the adaptive gain parameter at time t;

[0103] represents the first-order derivative of θ(t) at time t;

[0104] θ(0) represents the initial value of the adaptive gain parameter;

[0105] γ is the learning rate, which determines the speed of adaptive gain parameter adjustment and has a value range of 0.01-0.1;

[0106] Adjusted pressing force F cmd The calculation formula is as follows:

[0107] F cmd =F ref +θ(t)·φ(x) (7)

[0108] Among them, φ(x) is the state vector, which contains two state information: the pressure error and the pressure change rate. The expression of φ(x) is:

[0109]

[0110] in, is the rate of change of the actual pressing force, reflecting the changing trend of the pressing force over time;

[0111] The adaptive gain parameter θ is a parameter that is adjusted in real time during the adaptive control process to adapt the system to dynamic changes. The adaptive gain parameter θ is quickly adjusted by the gradient descent method to ensure that the output F of the controlled system is cmd Accurately track the desired trajectory F ref , reducing the error e(t).

[0112] Based on the pressure error feedback, the dynamic characteristics of the desired pressure control are established and the position of the acoustic probe is adjusted. The specific steps include the following:

[0113] The dynamic characteristics of the desired pressure control are established. The expression of the dynamic characteristics is as follows:

[0114]

[0115] Where M is the equivalent mass, which is 0.05 kg;

[0116] B is the damping coefficient, which is 5Ns / m;

[0117] K is the stiffness coefficient, which is 50N / m;

[0118] Calculate the position x of the acoustic probe after adjustment current , the calculation formula is as follows:

[0119]

[0120] in, is the velocity of the acoustic probe position (first-order derivative), describing the instantaneous motion state of the probe;

[0121] is the acceleration (second-order derivative) of the acoustic probe position, which represents the dynamic adjustment rate of the acoustic probe under force feedback control;

[0122] Δt is the time step, which represents the time interval between two adjacent sampling moments;

[0123] x previous This is the position of the acoustic probe before adjustment.

[0124] like Figure 2 As shown, it is an optional embodiment of the acoustic probe contact force and ultrasound collaborative control model structure in this application;

[0125] The acoustic probe contact force and ultrasound coordinated control model includes a mounting frame 100, which is connected to a lifting adjustment mechanism 200. A pair of acoustic probes 400 are provided on one side of the mounting frame 100. A horizontally placed first slide rail is fixed to the mounting frame 100, and a pair of first sliders are slidably connected within the first slide rail. The acoustic probes 400 correspond to the first sliders one by one. The acoustic probes 400 and the first sliders are both connected by a pressure adjustment mechanism 300, and the pressure adjustment mechanism 300 is also provided with a pressure collection unit.

[0126] The lifting and lowering adjustment mechanism 200 is used to drive the mounting frame 100 to move up and down. The lifting and lowering adjustment mechanism 200 includes a pair of vertically placed second slide rails, each of which is slidably connected to a second slider, and each of which is fixed to the mounting frame 100. A vertically placed rack is also fixed to the mounting frame 100, and a gear is meshed with the rack, and the gear is connected to a driving motor, and the gear is connected to the output shaft of the driving motor. It should be noted that the second slide rail and the driving motor are both installed on a fixed object such as an external wall. When in use, the driving motor can be turned on, and the driving motor drives the gear to rotate, and the gear drives the rack to move up and down, and the rack drives the mounting frame 100, the pressure regulating mechanism 300 and the acoustic probe 400 in turn, and the rotation direction of the output shaft of the driving motor is controlled to control the lifting and lowering adjustment of the acoustic probe 400.

[0127] The pressure adjustment mechanism 300 includes a connecting plate vertically fixed to the first slider, a vertically placed third slide rail is installed on the connecting plate, a third slide rail is slidably connected to the third slide rail, a lifting bar is fixed to the third slide, and the lifting bars are fixed to the corresponding sound probe 400, and at least one spring placed vertically upward is provided on one side of the connecting plate close to the lifting bar, and a connecting shaft is fixed at both ends of the spring, the upper connecting shaft of the spring is fixed to the third slide, and the lower connecting shaft of the spring is fixed to the connecting plate; through the coordinated arrangement of the connecting plate, the third slide rail, the third slide, the lifting bar and the spring, when the lifting adjustment mechanism 200 drives the sound probe 400 to move up and down and contact the wall, the arrangement of the spring can prevent the sound probe 400 from rigidly colliding with the wall, etc., and at the same time, by driving the third slide, the third slide drives the connecting shaft to squeeze and compress the spring to different degrees, so that the elastic force of the spring can be controlled, thereby indirectly controlling and adjusting the pressing force applied to the sound probe 400;

[0128] Preferably, the pressure collecting unit may be a pressure sensor, a piezoresistive pressure sensor or an optical fiber pressure sensor, etc., which can be used to detect the elastic force of the spring, and thus indirectly measure the pressing force applied to the acoustic probe 400 .

[0129] Throughout this specification, references to terms such as "one embodiment," "example," or "specific example" indicate that the specific features, structures, materials, or characteristics described in conjunction with that embodiment or example are included in at least one embodiment or example of the present invention. In this specification, schematic representations of these terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

[0130] The basic principles, main features, and advantages of the present invention are shown and described above. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The above embodiments and descriptions are merely illustrative of the principles of the present invention. Various changes and modifications may be made to the present invention without departing from the spirit and scope of the present invention, and such changes and modifications are intended to fall within the scope of the present invention.

Claims

1. A method for collaborative control of acoustic probe contact force and ultrasound based on adaptive control, characterized in that: The specific steps include: Collect ultrasonic waveforms to extract echo signals, calculate characteristic parameters of the echo signals, and determine whether the pressing force is appropriate based on the characteristic parameters of the echo signals; Collect the actual pressing force of the acoustic probe, calculate the pressing force error based on the expected pressing force, and determine whether to enter the adjustment mode; The adjustment mode includes adjusting the pressing force and adjusting the position of the acoustic probe; Based on model reference adaptive control, the adaptive gain parameters are calculated to adjust the pressing force; According to the pressure error feedback, the dynamic characteristics of the desired pressure control are established and the position of the acoustic probe is adjusted; After the adjustment mode ends, the ultrasonic waveform is collected again to extract the echo signal, and the pressing force is calculated and judged to be appropriate; if the pressing force is judged to be appropriate, the adjustment is successful; if the pressing force is judged to be inappropriate, iterative adjustment is performed until the pressing force is judged to be appropriate.

2. The method for cooperative control of acoustic probe contact force and ultrasound based on adaptive control according to claim 1, characterized in that: Characteristic parameters include signal amplitude A actual , signal-to-noise ratio SNR and bottom echo intensity R b .

3. The method for cooperative control of acoustic probe contact force and ultrasound based on adaptive control according to claim 2, characterized in that: Calculating the characteristic parameters of the echo signal and judging whether the pressing force is appropriate based on the characteristic parameters of the echo signal specifically includes the following steps: Signal amplitude A actual The calculation formula is: Among them, A max is the signal amplitude under the optimal pressing force; α is the adjustment factor; F ref is the expected pressing force, the value of which is determined by the distance between the acoustic probe and the wall; F actual is the actual pressing force; The calculation formula for the signal-to-noise ratio SNR is: Among them, P signal is the signal power; P noise is the noise power; Bottom wall echo intensity R b The calculation formula is as follows: Preset signal amplitude threshold β1, signal-to-noise ratio threshold β2 and bottom wall echo intensity threshold range β3; If the signal amplitude A actual If it is less than the signal amplitude threshold β1, the pressing force is inappropriate; If the signal-to-noise ratio SNR is less than the signal-to-noise ratio threshold β2, the pressing force is inappropriate; If the bottom echo intensity R b If the pressure deviates from the threshold range β3, the pressing force is inappropriate.

4. The method for cooperative control of acoustic probe contact force and ultrasound based on adaptive control according to claim 3, characterized in that: Based on the expected pressing force, the pressing force error is calculated to determine whether to enter the adjustment mode. The specific steps include the following: Calculate the pressure error. The calculation formula for the pressure error is as follows: e(t)=|F ref -F actual | (4) Where, e(t) is the pressure error at time t; Preset the error threshold ε; If the pressure error e(t) is greater than the error threshold ε, it is determined that the adjustment mode has been entered.

5. The method for cooperative control of acoustic probe contact force and ultrasound based on adaptive control according to claim 4, characterized in that: Based on the model reference adaptive control, the adaptive gain parameters are calculated and the pressing force is adjusted. The specific steps include: The calculation formula of the adaptive gain parameter is as follows: θ(t)=θ(0)-γ∫e(t)F actual dt (6) Where θ(t) represents the adaptive gain parameter at time t; represents the first-order derivative of θ(t) at time t; θ(0) represents the initial value of the adaptive gain parameter; γ is the learning rate, which determines the speed of adaptive gain parameter adjustment; Adjusted pressing force F cmd The calculation formula is as follows: F cmd =F ref +θ(t)·φ(x) (7) Among them, φ(x) is the state vector, which contains two state information: the pressure error and the pressure change rate. The expression of φ(x) is: in, It is the rate of change of the actual pressing force, reflecting the changing trend of the pressing force over time.

6. The method for cooperative control of acoustic probe contact force and ultrasound based on adaptive control according to claim 5, characterized in that: Based on the pressure error feedback, the dynamic characteristics of the desired pressure control are established and the position of the acoustic probe is adjusted. The specific steps include the following: The dynamic characteristics of the desired pressure control are established. The expression of the dynamic characteristics is as follows: Among them, M is the equivalent mass, B is the damping coefficient, and K is the stiffness coefficient; Calculate the position x of the acoustic probe after adjustment current , the calculation formula is as follows: in, is the velocity of the acoustic probe position, describing the instantaneous motion state of the probe; is the acceleration of the acoustic probe position, which represents the dynamic adjustment rate of the acoustic probe under force feedback control; Δt is the time step, which represents the time interval between two adjacent sampling moments; x previous This is the position of the acoustic probe before adjustment.

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