Force / position control method for ultrasonic probe

Abstract

The invention provides a force / position control method for an ultrasonic probe. The method comprises the following steps: setting a macro threshold value and a micro threshold value of a macro-micro force control device; when the average pressing force of the left probe and the right probe is lower than a macro threshold value, switching to a macro motion mode, and controlling a macro moving rod to move towards a direction close to the surface to be detected until the average pressing force of the left probe and the right probe is not lower than the macro threshold value; when the pressing force difference between the left probe and the right probe exceeds a micro-threshold value, the micro-motion mode is switched to, and the micro-motor is controlled to drive the micro-rotating rod to rotate until the pressing force of the left probe and the pressing force of the right probe are equal. The two-stage motion mode of the macro motion mode and the micro motion mode is adopted to achieve synchronous control over the pressing force of the double-probe set, the rapidness and accuracy of synchronous regulation and control over the pressing force of the left probe and the right probe can be improved, the pressing position can be rapidly reached, and meanwhile the pressing force can be accurately adjusted.

Description

Technical Field

[0001] The invention relates to a force / position control method for an ultrasonic probe, belonging to the technical field of ultrasonic flaw detection. Background Art

[0002] Ultrasonic flaw detection using time-of-flight diffraction (TOFD) is a commonly used nondestructive testing method for detecting internal defects in materials. The contact force between the probe and the surface of the object being tested significantly affects the quality of the test signal and the accuracy of the test results.

[0003] Traditional detection probes usually include two left and right probes. However, most of them usually use adaptive mechanisms such as springs and do not have the ability to actively adjust the pressing force. Although some mechanisms are equipped with an independent driving mechanism for each probe to control its pressing force, it is difficult to synchronously control the pressing force of the left and right probes. Its speed and accuracy cannot meet the high requirements for the effective pressing force of the probes at both ends in complex surface detection, which limits the detection stability and ultrasonic image quality, and affects the accuracy of the detection results. Summary of the Invention

[0004] The purpose of the present invention is to provide a force / position control method for an ultrasonic probe to solve the problem in the prior art that the speed and accuracy of synchronous control of the pressing force of the left and right probes of TOFD ultrasonic flaw detection need to be improved.

[0005] The technical solution of the present invention is:

[0006] A force / position control method for an ultrasonic probe comprises the following steps:

[0007] S1. Setting the macrothreshold and microthreshold of the macro-micro force control device;

[0008] S2. When the average pressing force of the left probe and the right probe is lower than the macro threshold, switch to the macro motion mode and control the macro moving rod to move in the direction close to the surface to be detected until the average pressing force of the left probe and the right probe is no lower than the macro threshold;

[0009] S3. When the difference in the pressing force between the left probe and the right probe exceeds a micro-threshold, the system switches to a micro-motion mode and controls the micro-motor to drive the micro-rotating rod to rotate until the pressing force of the left probe and the right probe is equal.

[0010] Furthermore, in step S1, the macro threshold F is set H =Ideal pressing force F0.

[0011] Furthermore, the macro-micro force control device includes a dual probe group, a micro motion mechanism, a macro motion mechanism, and a control module for controlling the micro motion mechanism and the macro motion mechanism. The dual probe group includes a left probe and a right probe, and the left probe and the right probe are respectively provided with a pressure sensor.

[0012] Micro-motion mechanism: according to the rotation control instructions of the control module, the dual probe group is rotated to adjust the pressing force of the left and right probes;

[0013] Macro motion mechanism: according to the movement control instructions of the control module, the micro motion mechanism is moved to adjust the position of the left probe and the right probe;

[0014] Control module: switches between macro motion mode and micro motion mode in real time, and sends control instructions to the micro motion mechanism and macro motion mechanism.

[0015] Furthermore, the micro-motion mechanism includes a micro-rotating rod and a micro-motor. One end of the micro-rotating rod is connected to the left probe through a left spring, and the other end of the micro-rotating rod is connected to the right probe through a right spring. The middle part of the micro-rotating rod is connected to the output shaft of the micro-motor, and the micro-motor is arranged on the macro-motion mechanism.

[0016] Furthermore, the macro motion mechanism includes a macro moving rod and a macro motor. The macro moving rod adopts a ball screw, and the macro motor adopts a servo motor. The macro moving rod is arranged on the robot body.

[0017] Furthermore, in step S2, in the macro motion mode, the following adaptive law is used to control the operation of the macro motor:

[0018] , in, is the speed of the macro motor, is the speed gain, is the set descending speed of the micro-movement rod, is the adaptive adjustment coefficient, is the pitch of the screw motor, F H is the macro threshold, F1 and F2 are the pressing forces of the left probe and the right probe, respectively.

[0019] Furthermore, in step S3, in the micro-motion mode, the control module uses PID to control the rotation speed u2 of the micro-motor:

[0020] , in, is the proportional gain, is the differential gain, is the integral gain, F1 and F2 are the pressing forces of the left and right probes respectively, and are the first-order derivatives of the pressing force F1 of the left probe and the first-order derivative of the pressing force F2 of the right probe, respectively. W is a micro-threshold.

[0021] The beneficial effects of the present invention are:

[0022] 1. This force / position control method for ultrasonic probes adopts a two-level motion mode, macro motion mode and micro motion mode, to achieve synchronous control of the pressing force of the dual probe group. It can improve the speed and accuracy of the synchronous regulation of the pressing force of the left and right probes, and can achieve rapid reaching of the pressing position while accurately adjusting the pressing force.

[0023] 2. This force / position control method for ultrasonic probes can achieve precise micro-force regulation by adopting a micro-rotating rod of a micro-motion mechanism and setting a left spring and a right spring at the left probe and the right probe respectively, ensuring that the pressing force of the left probe and the right probe are consistent.

[0024] 3. This force / position control method for ultrasonic probes uses adaptive speed control and PID control for the micro-motion mechanism and macro-motion mechanism respectively, and switches the micro-motion mechanism and macro-motion mechanism according to the threshold value, which can ensure the rapidity and stability of the force / displacement of the dual-probe group, thereby improving the detection quality. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 1 is a flow chart of a method for controlling macro- and micro-forces of a dual-probe TOFD ultrasonic flaw detection system according to an embodiment of the present invention;

[0026] Figure 2 2 is a schematic structural diagram of a macro-micro force control device in an embodiment;

[0027] Figure 3 1 is a schematic diagram of the implementation process of the macro-micro force control by the control module in the embodiment;

[0028] Among them: 1-left probe, 2-right probe, 3-micro rotating rod, 4-micro motor, 5-macro moving rod, 6-macro motor, 7-left spring, 8-right spring, 9-robot body, 10-surface to be detected. DETAILED DESCRIPTION

[0029] The preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0030] The embodiment provides a force / position control method for an ultrasound probe, such as Figure 1 , including the following steps,

[0031] S1. Setting the macrothreshold and microthreshold of the macro-micro force control device.

[0032] In step S1, set the macro threshold F H = Ideal pressing force F0, in Newtons, which is preset based on experience or experiment. Set the microthreshold F W The unit is Newton.

[0033] like Figure 2The macro-micro force control device includes a dual probe group, a micro motion mechanism, a macro motion mechanism, and a control module for controlling the micro motion mechanism and the macro motion mechanism. The dual probe group includes a left probe 1 and a right probe 2. The left probe 1 and the right probe 2 are respectively provided with a pressure sensor.

[0034] Micro-motion mechanism: Based on the rotation control instructions from the control module, the dual-probe assembly rotates to adjust the pressing force on the left and right probes 1 and 2. The micro-motion mechanism comprises a micro-rotation rod 3 and a micro-motor 4. One end of the micro-rotation rod 3 is connected to the left probe 1 via a left spring 7, and the other end is connected to the right probe 2 via a right spring 8. The middle of the micro-rotation rod 3 is connected to the output shaft of the micro-motor 4, which is mounted on the macro-motion mechanism. Pressure sensors are located between the left spring 7 and the left probe 1, and between the right spring 8 and the right probe 2.

[0035] Macro-motion mechanism: Based on the movement control instructions from the control module, the micro-motion mechanism moves to adjust the positions of the left and right probes 1 and 2. The macro-motion mechanism includes a macro-movement rod 5 and a macro-motor 6. The macro-movement rod 5 uses a ball screw, and the macro-motor 6 uses a servo motor. The macro-movement rod 5 is mounted on the robot body 9.

[0036] Control module: switches between macro motion mode and micro motion mode in real time, and sends control instructions to the micro motion mechanism and macro motion mechanism.

[0037] S2. When the average pressing force of the left probe 1 and the right probe 2 is lower than the macro threshold, switch to the macro motion mode and control the macro moving rod 5 to move in the direction close to the surface to be detected 10 until the average pressing force of the left probe 1 and the right probe 2 is no lower than the macro threshold.

[0038] In step S2, in the macro motion mode, the following adaptive law is used to control the operation of the macro motor 6:

[0039] , in, is the speed of macro motor 6, is the speed gain, is the set descending speed of the micro-movement rod, is the adaptive adjustment coefficient, is the pitch of the screw motor, F H is the macro threshold, F1 and F2 are the pressing forces of the left probe 1 and the right probe 2, respectively.

[0040] The above control law allows the macro motion mechanism to carry the left probe 1 and the right probe 2 to move quickly to the detection surface 10 at a constant speed, and when any probe reaches the detection surface, the speed of the macro motor 6 is adaptively adjusted, so that the closer the average pressing force is to the macro threshold, the slower the speed of the macro moving rod 5 is, until the pressing force is The detection surface 10 is stopped at the same time, thereby achieving a fast and accurate adaptive pressure adjustment effect and avoiding damage to the detection surface 10 due to excessive speed.

[0041] S3. When the pressure difference between the left probe 1 and the right probe 2 exceeds the micro threshold, the micro motion mode is switched to control the micro motor 4 to drive the micro rotating rod 3 to rotate until the pressure of the left probe 1 and the right probe 2 are equal.

[0042] In step S3, in the micro-motion mode, the control module uses PID to control the rotation speed u2 of the micro-motor 4:

[0043] , in, is the proportional gain, is the differential gain, is the integral gain, F1 and F2 are the pressing forces of the left probe 1 and the right probe 2 respectively. and are the first-order derivatives of the pressing force F1 of the left probe 1 and the first-order derivative of the pressing force F2 of the right probe 2, respectively. W is a micro-threshold.

[0044] This force / position control method for ultrasonic probes, such as Figure 3 The macro motion mode and the micro motion mode are used to realize the synchronous control of the pressing force of the dual probe group, which can improve the speed and accuracy of the synchronous regulation of the pressing force of the left probe 1 and the right probe 2, and can quickly reach the pressing position while accurately adjusting the pressing force.

[0045] This force / position control method for ultrasonic probes realizes the adjustment of the probe position and the pressing force of the measured surface during the detection process by setting a macro-motion mechanism and a micro-motion mechanism. The macro-motion mechanism quickly approaches the detection surface and ensures the desired pressing force through position control. The micro-motion mechanism performs fine-tuning according to the real-time force difference of the ultrasonic probe, adjusts the pressing depth of the left probe 1 and the right probe 2, and ensures that the pressing force of the left probe 1 and the right probe 2 is stable and consistent on any detection surface. The macro-motion mode and the micro-motion mode are switched according to the pressing force of the left probe 1 and the right probe 2, and the macro-motion mode and the micro-motion mode are not performed at the same time. The macro-micro motion mode is switched in real time, and each motor receives a control signal and performs automatic detection. The present invention adopts two-level motion control for fast and accurate control of the pressing force, which can ensure that the probe presses the complex detection surface quickly and stably during the detection process, thereby improving the accuracy of the detection.

[0046] Although the present invention has been described in detail with reference to the aforementioned embodiments, it is still possible for those skilled in the art to modify the technical solutions described in the aforementioned embodiments, or to make equivalent substitutions for some of the technical features therein. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A force / position control method for an ultrasonic probe, characterized in that: The following steps are included: S1. Setting the macrothreshold and microthreshold of the macro-micro force control device; S2. When the average pressing force of the left probe and the right probe is lower than the macro threshold, switch to the macro motion mode and control the macro moving rod to move in the direction close to the surface to be detected until the average pressing force of the left probe and the right probe is no lower than the macro threshold; S3. When the difference in the pressing force between the left probe and the right probe exceeds a micro-threshold, the system switches to a micro-motion mode and controls the micro-motor to drive the micro-rotating rod to rotate until the pressing force of the left probe and the right probe is equal.

2. The force / position control method for an ultrasonic probe according to claim 1, wherein: In step S1, set the macro threshold F H =Ideal pressing force F0.

3. The force / position control method for an ultrasonic probe according to claim 1, wherein: The macro-micro force control device includes a dual probe group, a micro motion mechanism, a macro motion mechanism, and a control module for controlling the micro motion mechanism and the macro motion mechanism. The dual probe group includes a left probe and a right probe, and the left probe and the right probe are respectively provided with a pressure sensor. Micro-motion mechanism: according to the rotation control instructions of the control module, the dual probe group is rotated to adjust the pressing force of the left and right probes; Macro motion mechanism: according to the movement control instructions of the control module, the micro motion mechanism is moved to adjust the position of the left probe and the right probe; Control module: switches between macro motion mode and micro motion mode in real time, and sends control instructions to the micro motion mechanism and macro motion mechanism.

4. The force / position control method for an ultrasonic probe according to claim 3, wherein: The micro-motion mechanism includes a micro-rotating rod and a micro-motor. One end of the micro-rotating rod is connected to the left probe through a left spring, and the other end of the micro-rotating rod is connected to the right probe through a right spring. The middle part of the micro-rotating rod is connected to the output shaft of the micro-motor, and the micro-motor is arranged on the macro-motion mechanism.

5. The force / position control method for an ultrasonic probe according to claim 3, wherein: The macro motion mechanism includes a macro moving rod and a macro motor. The macro moving rod adopts a ball screw, and the macro motor adopts a servo motor. The macro moving rod is arranged on the robot body.

6. A force / position control method for an ultrasonic probe according to any one of claims 1 to 5, characterized in that: In step S2, in the macro motion mode, the following adaptive law is used to control the operation of the macro motor: ， in, is the speed of the macro motor, is the speed gain, is the set descending speed of the micro-movement rod, is the adaptive adjustment coefficient, is the pitch of the screw motor, F H is the macro threshold, F1 and F2 are the pressing forces of the left probe and the right probe, respectively.

7. A force / position control method for an ultrasonic probe according to any one of claims 1 to 5, characterized in that: In step S3, in the micro-motion mode, the control module uses PID to control the rotation speed u2 of the micro-motor: ， in, is the proportional gain, is the differential gain, is the integral gain, F1 and F2 are the pressing forces of the left and right probes respectively, and are the first-order derivatives of the pressing force F1 of the left probe and the first-order derivative of the pressing force F2 of the right probe, respectively. W is a micro-threshold.

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