Flexible self-adaptive detection force control method for mobile robot

Abstract

The invention provides a flexible adaptive detection force control method for a mobile robot, and the method comprises the steps: determining an ideal pressing force of a detection device of the mobile robot according to experience data including TOFD detection image quality and surface material detection; a force sensor of the detection device measures the pressing force of the probe, and then the actual pressing force of the ultrasonic detection probe on the detection surface is calculated according to the stress condition of the detection robot on the detection surface; encoder information of a driving motor and a probe lead screw motor of the mobile robot is obtained, and then the moving speed, real-time displacement and initial pressing displacement information of the mobile robot along the detection surface are obtained; a sliding mode self-adaptive force control algorithm is adopted to obtain a motion control signal, and the actual pressing force of the ultrasonic detection probe is adjusted in real time; accurate robust control over the pressing force of the probe can be achieved, the adaptability and detection precision of the ultrasonic flaw detection probe in complex curved surface detection can be improved, and the stability of the pressing force of the probe is ensured.

Description

Technical Field

[0001] The invention relates to a compliant self-adaptive detection force control method for a mobile robot, belonging to the technical field of ultrasonic probe detection. Background Art

[0002] Ultrasonic flaw detection is a commonly used nondestructive testing method for detecting internal defects in materials. The contact force and movement trajectory of the probe between the surface and the object being tested significantly influence the quality of the test signal and the accuracy of the test results. However, traditional probe control methods, which typically employ passive compliance devices or displacement control, struggle to meet the stringent requirements for stable and compliant contact force required for complex curved surface inspection.

[0003] Therefore, a sliding mode adaptive force control method is proposed to achieve more accurate and efficient ultrasonic flaw detection operation, and friction disturbance is considered to improve the force control stability and robustness. Summary of the Invention

[0004] The purpose of the present invention is to provide a compliant adaptive detection force control method for a mobile robot to solve the problem in the prior art that probe pressing force control is missing or insufficient, resulting in low accuracy and stability of probe control.

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

[0006] A method for controlling the compliant adaptive detection force of a mobile robot comprises the following steps:

[0007] S1. Determine the ideal pressing force Fd of the detection device of the mobile robot based on empirical data including TOFD detection image quality and detection surface material;

[0008] S2. The force sensor of the detection device measures the pressing force of the probe , and then analyze the force of the mobile robot on the detection surface and calculate the actual pressing force Fz of the ultrasonic detection probe on the detection surface;

[0009] S3, obtaining encoder information of the driving motor of the mobile robot and the lead screw motor of the probe, and then obtaining the moving speed, real-time displacement and initial pressing displacement information of the mobile robot along the detection surface;

[0010] S4, based on the error between the actual pressing force Fz and the ideal pressing force Fd and the disturbance term ,The sliding mode adaptive force control algorithm is used to obtain the motion control signal, and the actual pressing force Fz of the ultrasonic detection probe is adjusted in real time, so that the ultrasonic detection probe of the mobile robot can detect the surface with the ideal pressing force Fd during the detection process.

[0011] Furthermore, in step S1, the detection device includes a screw, a pressing motor, a pressing spring and an ultrasonic detection probe, namely a TOFD probe. The pressing motor is arranged on the body of the detection robot, the screw is driven by the pressing motor, the screw is connected to the TOFD probe through the pressing spring, and a force sensor is provided between the screw and the pressing spring.

[0012] Furthermore, in step S2, the force applied to the mobile robot on the detection surface is analyzed, specifically,

[0013] S21. Actual pressure of ultrasonic testing probe on the testing surface : , where α is the probe pressing force Relative actual pressing force The deflection angle, , is the radius of the surface to be tested, is the body length of the mobile robot, is the probe pressing force;

[0014] S22, friction force on ultrasonic detection probe : ,in, is the friction coefficient between the probe and the detection surface, is the moving speed of the mobile robot along the detection surface, c is the damping coefficient between the probe and the detection surface;

[0015] S23. Consider the tangential force acting on the ultrasonic detection probe as the main part of the interference term: ;

[0016] S24: According to step S23, the interference item is pressed by the probe. The real-time influence of the two variables v and the moving speed, so the disturbance term d is defined as:

[0017] ,

[0018] in, Probe pressing force The relevant disturbance term of is the moving speed of the mobile robot along the detection surface The relevant disturbance terms.

[0019] Furthermore, in step S4, a sliding mode adaptive force control algorithm is used, specifically,

[0020] S41, establishing a probe pressing force model;

[0021] S42. Design a sliding mode adaptive control method;

[0022] S43. Design of adaptive control law:

[0023] ,

[0024] Among them, u is the input of the pressing motor control, is the first-order derivative of the ideal pressing force Fd, the transmission coefficient of the pressing mechanism ,in, is the compression spring stiffness, is the lead screw pitch; the speed control gain of the pressing motor ,in, Output angular displacement for the probe screw motor The first derivative of α is the probe pressure. Relative actual pressing force The deflection angle, , is the radius of the surface to be tested, is the body length of the mobile robot; Perturbation boundary estimated value of; is the sliding surface ratio parameter, is the sign function, and s is the sliding surface.

[0025] Furthermore, in step S41, a probe pressing force model is established, specifically,

[0026] S411, the pressing motor runs in speed mode, then the pressing motor controls the input , where k is the speed control gain of the pressing motor, Output angle displacement for the pressing motor The first derivative of ;

[0027] S412. According to the displacement transmission relationship of the pressing mechanism, the probe pressing force is obtained. :

[0028] ,

[0029] in, is the compression spring stiffness, is the lead screw displacement when the probe begins to contact the detection surface, is the screw pitch, The motor displacement when the probe begins to contact the detection surface, press the relationship between the motor output angle displacement θ and the screw displacement x: ;

[0030] S413, Order , then the probe pressure model is established:

[0031] ,

[0032] in, is the probe pressing force, is the transmission coefficient of the pressing system, is the output angle displacement of the pressing motor, is the motor displacement when the probe begins to contact the test surface.

[0033] Furthermore, in step S42, a sliding mode adaptive control method is designed, specifically,

[0034] S421. According to step S413, the first-order derivative of the probe pressure model is calculated, and the disturbance term d is introduced to obtain the probe pressure The first derivative of :

[0035] ,

[0036] in, is the transmission coefficient of the pressing mechanism, k is the speed control gain of the pressing motor, u is the control input of the pressing motor, and the disturbance term ,in, Probe pressing force The relevant disturbance term of is the moving speed of the mobile robot along the detection surface The relevant disturbance term of

[0037] S422. Define the sliding surface: ;

[0038] Definition error: ,in, For ideal pressing force, is the actual pressing force;

[0039] according to , we can get:

[0040] ,

[0041] in, For ideal pressing force The first derivative of The actual pressing force of the probe The first derivative of Probe pressing force The first derivative of α is the probe pressure Relative actual pressing force Deflection angle;

[0042] Will After substituting into the above formula, we get:

[0043] ,

[0044] Then the pressing motor control input u is obtained:

[0045] ,

[0046] in, is the sliding surface ratio parameter, is the perturbation boundary, and ,set up Perturbation boundary The estimated value of ,in, Perturbation boundary The estimated value of Perturbation boundary The estimated value of is a symbolic function, .

[0047] Furthermore, in step S43, an adaptive control law is designed, specifically,

[0048] S431, disturbance boundary The first derivative of the estimated value D :

[0049] ,

[0050] in, and is the adaptive gain coefficient, and , , is the moving speed of the mobile robot along the detection surface, s is the sliding surface, is the probe pressing force, is the moving speed of the mobile robot along the detection surface; the disturbance boundary Estimated value of The first derivative of : , perturbation boundary Estimated value of The first derivative of : ;

[0051] S432, sliding mode adaptive control law is

[0052] ,

[0053] Among them, u is the input of the pressing motor control, is the first-order derivative of the ideal pressing force Fd, is the transmission coefficient of the pressing mechanism, is the speed control gain of the pressing motor, α is the probe pressing force Relative actual pressing force The deflection angle, is the sliding surface ratio parameter, is the pressure error, Perturbation boundary The estimated value of After integral calculation, s is the sliding surface, is a symbolic function.

[0054] The beneficial effects of the present invention are: this mobile robot flexible adaptive detection force control method can achieve accurate and robust control of the probe pressing force, can improve the adaptability and detection accuracy of the ultrasonic flaw detection probe in complex surface detection, and ensure the stability of the probe pressing force. BRIEF DESCRIPTION OF THE DRAWINGS

[0055] Figure 1 This is a flow chart of a method for controlling compliant and adaptive detection force of a mobile robot according to an embodiment of the present invention;

[0056] Figure 2 is a schematic diagram illustrating a detection device of a mobile robot on a curved surface in an embodiment;

[0057] Figure 3 is a schematic diagram illustrating the force applied to the mobile robot on a curved surface in an embodiment;

[0058] Figure 4 is a schematic diagram illustrating sliding mode adaptive pressing force control of a mobile robot in an embodiment;

[0059] Figure 5 is a schematic diagram illustrating adaptive pressure control of the pressing motors at the left and right ends of the mobile robot according to an embodiment;

[0060] Among them: 1-detection robot, 2-lead screw, 3-pressing motor, 4-pressing spring, 5-ultrasonic detection probe, 6-force sensor. DETAILED DESCRIPTION

[0061] The preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0062] The embodiment provides a method for controlling the compliant adaptive detection force of a mobile robot. Figure 1 , including the following steps:

[0063] S1. Determine the ideal pressing force Fd of the mobile robot's detection device based on empirical data including TOFD detection image quality and detection surface material.

[0064] In step S1, Figure 2The detection device includes a screw, a pressing motor, a pressing spring and an ultrasonic detection probe, namely a TOFD probe. The pressing motor is arranged on the body of the detection robot. The screw is driven by the pressing motor. The screw is connected to the TOFD probe through the pressing spring, and a force sensor is provided between the screw and the pressing spring. Figure 2 In the figure, the direction of the arrow is the moving direction of the screw, and detection devices with the same structure are respectively provided at the left and right ends of the side of the mobile robot.

[0065] S2. The force sensor of the detection device measures the pressing force of the probe , and then calculate the actual pressing force Fz of the ultrasonic detection probe on the detection surface according to the force applied by the detection robot on the detection surface.

[0066] In step S2, the force applied to the mobile robot on the detection surface is analyzed, such as Figure 3 , specifically,

[0067] S21. Actual pressure of ultrasonic testing probe on the testing surface : , where α is the probe pressing force Relative actual pressing force Deflection angle, probe pressing force Actual pressing force , , is the radius of the surface to be tested, is the body length of the mobile robot, is the probe pressing force;

[0068] S22, friction force on ultrasonic detection probe : ,in, is the friction coefficient between the probe and the detection surface, is the moving speed of the mobile robot along the detection surface, c is the damping coefficient between the probe and the detection surface;

[0069] S23. Consider the tangential force acting on the ultrasonic detection probe as the main part of the interference term: ;

[0070] S24: According to step S23, the interference item is pressed by the probe. The real-time influence of the two variables v and the moving speed, so the disturbance term d is defined as:

[0071] ,

[0072] in, Probe pressing force The relevant disturbance term of is the moving speed of the mobile robot along the detection surface The relevant disturbance terms.

[0073] S3. Obtain encoder information of the driving motor of the mobile robot and the lead screw motor of the probe, and then obtain the moving speed, real-time displacement and initial pressing displacement information of the mobile robot along the detection surface.

[0074] In step S3, the driving motor of the mobile robot provides movement speed information, and the probe lead screw motor provides real-time displacement and initial pressing displacement information.

[0075] S4, based on the error between the actual pressing force Fz and the ideal pressing force Fd and the disturbance term , a sliding mode adaptive force control algorithm is used to obtain the motion control signal, and the actual pressing force Fz of the ultrasonic detection probe 5 is adjusted in real time, so that the ultrasonic detection probe 5 of the detection robot detects the surface with the ideal pressing force Fd during the detection process.

[0076] In step S4, a sliding mode adaptive force control algorithm is used, specifically,

[0077] S41, establishing a probe pressing force model;

[0078] S411, the pressing motor runs in speed mode, then the pressing motor controls the input , where k is the speed control gain of the pressing motor, Output angle displacement for the pressing motor The first derivative of ;

[0079] S412. According to the displacement transmission relationship of the pressing mechanism, the probe pressing force is obtained. :

[0080] ,

[0081] in, is the compression spring stiffness, is the lead screw displacement when the probe begins to contact the detection surface, is the screw pitch, The motor displacement when the probe begins to contact the detection surface, press the relationship between the motor output angle displacement θ and the screw displacement x: ;

[0082] S413, Order , then the probe pressure model is established:

[0083] ,

[0084] in, is the probe pressing force, is the transmission coefficient of the pressing mechanism, is the output angle displacement of the pressing motor, is the motor displacement when the probe begins to contact the test surface.

[0085] S42. Design a sliding mode adaptive control method;

[0086] S421. According to step S413, the first-order derivative of the probe pressure model is calculated, and the disturbance term d is introduced to obtain the probe pressure The first derivative of :

[0087] ,

[0088] in, is the transmission coefficient of the pressing mechanism, k is the speed control gain of the pressing motor, u is the control input of the pressing motor, and the disturbance term ,in, Probe pressing force The relevant disturbance term of is the moving speed of the mobile robot along the detection surface The relevant disturbance term of

[0089] S422. Define the sliding surface: ;

[0090] Definition error: ,in, For ideal pressing force, is the actual pressing force;

[0091] according to , we can get:

[0092] ,

[0093] in, For ideal pressing force The first derivative of The actual pressing force of the probe The first derivative of Probe pressing force The first derivative of α is the probe pressing force Relative actual pressing force Deflection angle;

[0094] Will After substituting into the above formula, we get:

[0095] ,

[0096] Then we get:

[0097] ,

[0098] in, is the sliding surface ratio parameter, is the perturbation boundary, and ,set up Perturbation boundary The estimated value of ,in, Perturbation boundary The estimated value of Perturbation boundary The estimated value of is a symbolic function, .

[0099] S43, design adaptive control law, such as Figure 4 :

[0100] ,

[0101] Among them, u is the input of the pressing motor control, is the first-order derivative of the ideal pressing force Fd, the transmission coefficient of the pressing mechanism ,in, is the compression spring stiffness, is the lead screw pitch; the speed control gain of the pressing motor ,in, Output angular displacement for the probe screw motor The first derivative of ; Perturbation boundary estimated value of; is the sliding surface ratio parameter, is the sign function, and s is the sliding surface.

[0102] In step S43, an adaptive control law is designed, specifically,

[0103] S431, disturbance boundary The first derivative of the estimated value D :

[0104] ,

[0105] in, and is the adaptive gain coefficient, and , , is the moving speed of the mobile robot along the detection surface, s is the sliding surface, is the probe pressing force, is the moving speed of the mobile robot along the detection surface; the disturbance boundary Estimated value of The first derivative of : , perturbation boundary Estimated value of The first derivative of : ;

[0106] S432, sliding mode adaptive control law is

[0107] ,

[0108] Among them, u is the input of the pressing motor control, is the first-order derivative of the ideal pressing force Fd, is the transmission coefficient of the pressing mechanism, is the speed control gain of the pressing motor, α is the probe pressing force Relative actual pressing force The deflection angle, is the sliding surface ratio parameter, is the pressure error, Perturbation boundary The estimated value of After integral calculation, s is the sliding surface, is a symbolic function.

[0109] The stability of the designed adaptive control law is proved as follows:

[0110] 1) Define the Lyapunov function: ,but ;

[0111] 2) The first-order derivative of the sliding surface s : ;

[0112] 3) Due to the perturbation boundary Estimated value of The first derivative of , then the perturbation boundary Estimated value of ,but:

[0113] ,

[0114] in, is the first-order derivative of the error e, is the first derivative of the Lyapunov function.

[0115] 4) Due to Then the control law is stable.

[0116] In step S4, due to the actual pressing force of the two ultrasonic detection probes 5 of the mobile robot The actual feedback and control data according to the detection surface conditions such as the pressing position are different, and the calculated control amount u is also different. Therefore, if Figure 5 The two ultrasonic detection probes 5 of the mobile robot are independently controlled, each utilizing the sliding mode adaptive control law described in this invention. The independent control of the two ultrasonic detection probes 5 also enables the robot to independently navigate obstacles on either side, enhancing its mobility and surface adaptability.

[0117] This mobile robot's compliant adaptive detection force control method can achieve precise and robust control of the probe's pressing force, improve the adaptability and detection accuracy of ultrasonic flaw detection probes in complex surface detection, ensure the stability of the probe's pressing force, and thus optimize the ultrasonic signal quality.

[0118] This method of compliant adaptive detection force control for mobile robots introduces a robot ultrasonic detection pressing device, a probe curved surface pressing force model, and a sliding mode adaptive control algorithm to control the real-time pressing force of the ultrasonic probe on the surface of the object being tested during the detection process, and to control the pressing depth so that the actual pressing force matches the expected pressing force. The ultrasonic detection pressing device includes two sets of screw motor spring devices, each set of screw motor spring devices independently controls a detection probe. Therefore, the pressing action of the probes on both sides can be independently adjusted by controlling the two sets of pressing motors, thereby adapting to detection surfaces of various curvatures and shapes, and overcoming single-sided or double-sided probe detection failures due to uneven detection surfaces or during the robot's movement over obstacles, such as detachment from the detection surface or excessive pressing, thereby enhancing the robustness and adaptability of the robot detection system control. The probe curved surface pressing force model can compensate for the probe pressing force caused by the curvature of the curved surface. and actual pressing force The sliding mode adaptive force control algorithm estimates the system friction disturbance by detecting the pressing force and velocity feedback, and adaptively and quickly adjusts the pressing force error to ensure that the probe maintains a stable pressing force during the inspection process, thereby improving the accuracy of robotic ultrasonic inspection.

[0119] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the technical principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A compliant adaptive detection force control method for a mobile robot, characterized by: The following steps are included: S1. Determine the ideal pressing force Fd of the detection device of the mobile robot based on empirical data including TOFD detection image quality and detection surface material; S2. The force sensor of the detection device measures the pressing force of the probe , and then analyze the force of the mobile robot on the detection surface and calculate the actual pressing force Fz of the ultrasonic detection probe on the detection surface; S3, obtaining encoder information of the driving motor of the mobile robot and the lead screw motor of the probe, and then obtaining the moving speed, real-time displacement and initial pressing displacement information of the mobile robot along the detection surface; S4, based on the error between the actual pressing force Fz and the ideal pressing force Fd and the disturbance term ,The sliding mode adaptive force control algorithm is used to obtain the motion control signal, and the actual pressing force Fz of the ultrasonic detection probe is adjusted in real time, so that the ultrasonic detection probe of the mobile robot can detect the surface with the ideal pressing force Fd during the detection process.

2. The method for controlling the compliant adaptive detection force of a mobile robot according to claim 1, wherein: In step S1, the detection device includes a screw, a pressing motor, a pressing spring and an ultrasonic detection probe, namely a TOFD probe. The pressing motor is arranged on the body of the detection robot, the screw is driven by the pressing motor, the screw is connected to the TOFD probe through the pressing spring, and a force sensor is provided between the screw and the pressing spring.

3. The method for controlling the compliant adaptive detection force of a mobile robot according to claim 1, wherein: In step S2, the force applied to the mobile robot on the detection surface is analyzed, specifically, S21. Actual pressure of ultrasonic testing probe on the testing surface : , where α is the probe pressing force Relative actual pressing force The deflection angle, , is the radius of the surface to be tested, is the body length of the mobile robot, is the probe pressing force; S22, friction force on ultrasonic detection probe : ,in, is the friction coefficient between the probe and the detection surface, is the moving speed of the mobile robot along the detection surface, c is the damping coefficient between the probe and the detection surface; S23. Consider the tangential force acting on the ultrasonic detection probe as the main part of the interference term: ; S24: According to step S23, the interference item is pressed by the probe. The real-time influence of the two variables v and the moving speed, so the disturbance term d is defined as: ， in, Probe pressing force The relevant disturbance term of is the moving speed of the mobile robot along the detection surface The relevant disturbance terms.

4. A method for controlling compliant adaptive detection force of a mobile robot according to any one of claims 1 to 3, characterized in that: In step S4, a sliding mode adaptive force control algorithm is used, specifically, S41, establishing a probe pressing force model; S42. Design a sliding mode adaptive control method; S43. Design of adaptive control law: ， Among them, u is the input of the pressing motor control, is the first-order derivative of the ideal pressing force Fd, the transmission coefficient of the pressing mechanism ,in, is the compression spring stiffness, is the lead screw pitch; the speed control gain of the pressing motor ,in, Output angular displacement for the probe screw motor The first derivative of α is the probe pressure. Relative actual pressing force The deflection angle, , is the radius of the surface to be tested, is the body length of the mobile robot; Perturbation boundary estimated value of; is the sliding surface ratio parameter, is the sign function, and s is the sliding surface.

5. The method for controlling the compliant adaptive detection force of a mobile robot according to claim 4, wherein: In step S41, a probe pressing force model is established, specifically, S411, the pressing motor runs in speed mode, then the pressing motor controls the input , where k is the speed control gain of the pressing motor, Output angle displacement for the pressing motor The first derivative of ; S412. According to the displacement transmission relationship of the pressing mechanism, the probe pressing force is obtained. : ， in, is the compression spring stiffness, is the lead screw displacement when the probe begins to contact the detection surface, is the screw pitch, The motor displacement when the probe begins to contact the detection surface, press the relationship between the motor output angle displacement θ and the screw displacement x: ; S413, Order , then the probe pressure model is established: ， in, is the probe pressing force, is the transmission coefficient of the pressing mechanism, is the output angle displacement of the pressing motor, is the motor displacement when the probe begins to contact the test surface.

6. A method for controlling compliant and adaptive detection force of a mobile robot according to claim 5, characterized in that: In step S42, a sliding mode adaptive control method is designed, specifically, S421. According to step S413, the first-order derivative of the probe pressure model is calculated, and the disturbance term d is introduced to obtain the probe pressure The first derivative of : ， in, is the transmission coefficient of the pressing mechanism, k is the speed control gain of the pressing motor, u is the control input of the pressing motor, and the disturbance term ,in, Probe pressing force The relevant disturbance term of is the moving speed of the mobile robot along the detection surface The relevant disturbance term of S422. Define the sliding surface: ; Definition error: ,in, For ideal pressing force, is the actual pressing force; according to , we can get: ， in, For ideal pressing force The first derivative of The actual pressing force of the probe The first derivative of Probe pressing force The first derivative of α is the probe pressing force Relative actual pressing force Deflection angle; Will After substituting into the above formula, we get: ， Then the pressing motor control input u is obtained: ， in, is the sliding surface ratio parameter, is the perturbation boundary, and ,set up Perturbation boundary The estimated value of ,in, Perturbation boundary The estimated value of Perturbation boundary The estimated value of is a symbolic function, .

7. The method for controlling the compliant adaptive detection force of a mobile robot according to claim 4, wherein: In step S43, an adaptive control law is designed, specifically, S431, disturbance boundary The first derivative of the estimated value D : ， in, and is the adaptive gain coefficient, and , , is the moving speed of the mobile robot along the detection surface, s is the sliding surface, is the probe pressing force, is the moving speed of the mobile robot along the detection surface; the disturbance boundary Estimated value of The first derivative of : , perturbation boundary Estimated value of The first derivative of : ; S432, sliding mode adaptive control law is ， Among them, u is the input of the pressing motor control, is the first-order derivative of the ideal pressing force Fd, is the transmission coefficient of the pressing mechanism, is the speed control gain of the pressing motor, α is the probe pressing force Relative actual pressing force The deflection angle, is the sliding surface ratio parameter, is the pressure error, Perturbation boundary The estimated value of After integral calculation, s is the sliding surface, is a symbolic function.

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