Adaptive coordinated control loading and unloading method based on rock fracture information

Abstract

The present invention provides an adaptive coordinated control loading and unloading method based on rock fracture information, which relates to the technical field of rock mechanics testing. The acoustic emission sensor of the present invention monitors the rock fracture signal and converts it into an electrical signal, and transmits the fracture signal to the acoustic emission acquisition device. The acoustic emission acquisition device processes and analyzes the acoustic emission signal and transmits it to the PLC controller. The PLC controller calculates and outputs the deformation control signal through the control algorithm, thereby realizing adaptive adjustment of the input control command. After receiving the deformation control instruction, the EDC controller adjusts the force acting on the rock sample through the feedback control test machine servo actuator to realize stable control of the brittle fracture process of the rock sample.

Description

Technical Field

[0001] The invention relates to the technical field of rock mechanics testing, and in particular to an adaptive coordinated control loading and unloading method based on rock fracture information. Background Art

[0002] In deep hard rock engineering, rocks have the characteristics of high stiffness, high strength and strong brittleness. Under the influence of high stress and excavation disturbance, stress concentration and transfer occur inside the surrounding rock on site, accompanied by the initiation and expansion of fractures and energy release, and even induce severe brittle failure phenomena such as rock bursts. Moreover, the essence of high-stress brittle failure disasters such as rock bursts is the result of the change from quantitative change to qualitative change of rock fracture. Therefore, scientific understanding of the evolution process of deep hard rock fracture under high stress is of great significance to revealing the breeding mechanism of high-stress disasters such as rock bursts, rock stability evaluation and risk warning. How to achieve accurate testing of the full stress-strain brittle failure process of rocks induced by high stress is the key to solving the above problems.

[0003] In order to obtain the full stress-strain curve of rock, in addition to requiring the testing machine to have sufficient stiffness (generally greater than 5GN / m), the servo control method of the test is also crucial to capture the evolution process of rock post-peak fracture. Especially for deep hard rock, which has the characteristics of high strength and high stiffness, the rock is more brittle when it fails, and it is more difficult to capture the post-peak failure process. Traditional test techniques often conduct rock loading and unloading tests through stress control or displacement control, and generally maintain a constant loading rate. In a closed-loop servo-controlled rock mechanics test system, in order to obtain the full stress-strain curve of the rock fracture process, the displacement or deformation control loading and unloading method is usually adopted: maintaining a constant displacement or deformation rate, which is used as a feedback signal to adjust the application of stress. Compared with the stress control loading and unloading method, the constant displacement or deformation rate control method ensures the stable development of rock post-peak fracture to a certain extent and avoids the impact fracture of rock post-peak. However, this control method has high requirements for the setting of displacement or deformation rate, and it is crucial to set a suitable displacement or deformation rate; if the displacement or deformation rate is set too large, it will also cause impact failure of the rock in the post-peak stage. In addition, the fracture response of rock is different in the stages of rock crack initiation, expansion and penetration; moreover, rock fracture and deformation have a non-coordinated relationship, and the constant deformation rate control method cannot match the fracture response of rock.

[0004] Since the acoustic emission characteristics of the rock fracture process can better reflect the initiation and expansion of rock cracks, and the acoustic emission impact rate reflects the rate of rock fracture and crack expansion, parameters such as the acoustic emission impact rate can be used as key information in servo feedback control. Therefore, establishing an adaptive coordinated control loading method based on rock fracture information is crucial to realize the full stress-strain brittle failure process test of rock. Summary of the invention

[0005] In view of the shortcomings of the prior art, according to the characteristics of the acoustic emission signal of rock fracture, the present invention provides an adaptive coordinated control loading and unloading method based on rock fracture information, which adopts a coordinated control method combining the acoustic emission signal with the deformation signal. The method uses the characteristic parameters of the acoustic emission signal in the rock fracture process as the adjustment signal of the deformation control, and automatically adjusts the deformation control rate through the change of the characteristic parameters of the acoustic emission signal, so that during the loading process of the deformation feedback control actuator, the deformation control rate of the rock is automatically adjusted to match the control requirements of different stages of the rock fracture process.

[0006] The technical solution of the present invention is:

[0007] An adaptive coordinated control loading and unloading method based on rock fracture information comprises the following steps:

[0008] Step 1: After the acoustic emission sensor and the rock sample deformation sensor are assembled with the rock sample, they are installed in the pressure chamber of the rock testing machine; then the acoustic emission sensor is connected to the acoustic emission signal collector, and the acoustic emission signal is output to the voltage amplifier, and the voltage amplifier performs noise reduction and amplification processing on the input signal and then transmits it to the PLC controller; the rock sample deformation sensor is connected to the EDC controller, and the EDC controller is connected to the testing machine servo actuator; the PLC controller is synchronously interconnected with the EDC controller and connected to the computer.

[0009] Step 2: Set the initial deformation rate control amount and the monitoring threshold of the characteristic parameters of the acoustic emission signal of the rock fracture process on the computer, including the impact rate, amplitude, energy release rate, and count. Then the computer issues a loading instruction, and the servo actuator of the testing machine loads the rock sample in the pressure chamber of the rock testing machine. At the same time, the acoustic emission sensor collects the rock sample fracture signal, which is transmitted to the voltage amplifier by the acoustic emission signal collector. The voltage amplifier reduces the noise and amplifies the signal and then transmits it to the PLC controller.

[0010] Step 3: The PLC controller samples the acoustic emission signal, converts the collected analog signal into a digital signal through digital-to-analog conversion and stores it in a register. After calculation by the incremental digital PID control algorithm, the rock deformation control rate is adaptively changed, and a deformation rate control signal matching the rock fracture information is output to the EDC controller;

[0011] The incremental digital PID control algorithm specifically comprises the following steps:

[0012] Step S1: Initialize PID parameters, including the proportional coefficient K p , integral coefficient K i , differential coefficient K d, as well as the error variable e(k), the previous error variable e(k-1), the previous previous error variable e(k-2) and the output variable Δu;

[0013] Step S2: Read the current feedback value y and the expected value y_set, and calculate the error variable e = y_set - y;

[0014] Step S3: Calculate the output variable Δu(k) = K p Δe(k)+ K i e(k)+ K d [Δe(k)-Δe(k-1)];

[0015] Where Δe(k)=e(k)-e(k-1);

[0016] Step S4: sending the output variable Δu(k) into the deformation control rate instruction;

[0017] Step S5: Update error variables e(k)=e(k+1), e(k-1)=e(k), e(k-2)=e(k-1);

[0018] Step S6: If the test is not finished, return to step 2, otherwise continue to execute.

[0019] Step 4: The EDC controller receives the deformation rate control signal, adjusts the deformation rate of the rock sample, and judges whether the size of the deformation instruction meets the set deformation rate range of different fracture stages. If not, step 3 is repeated to adjust the deformation rate of the rock sample, and then it is transmitted to the servo actuator of the testing machine through closed-loop servo feedback to further adjust the rock loading and unloading rate and loading force, thereby adjusting the energy release rate of rock fracture to meet the needs of stable control.

[0020] The beneficial effects of adopting the above technical solution are:

[0021] The present invention provides an adaptive coordinated control loading and unloading method based on rock fracture information. Compared with the traditional constant deformation control rate servo feedback control method, this method uses the acoustic emission signal as the control variable and adopts a coordinated control method combining fracture and deformation signals. It can automatically adjust the deformation control command according to the degree of crack initiation and expansion, avoiding rock impact damage caused by the mismatch between the deformation control command and the rock damage degree. This method not only retains the accuracy of traditional control, but also greatly improves the stability of control during rock brittle fracture. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 This is a flow chart of the method for adaptive coordinated control of loading and unloading in an embodiment of the present invention;

[0023] Figure 2 It is a structural block diagram of the adaptive coordinated control loading and unloading system in an embodiment of the present invention. Implementation

[0024] The specific implementation of the present invention is further described in detail below in conjunction with the accompanying drawings and examples. The following examples are used to illustrate the present invention, but are not intended to limit the scope of the present invention.

[0025] An adaptive coordinated control loading and unloading method based on rock fracture information, such as Figure 1 As shown, the following steps are included:

[0026] Step 1: After the acoustic emission sensor and the rock sample deformation sensor are assembled with the rock sample, they are installed in the pressure chamber of the rock testing machine; then the acoustic emission sensor is connected to the acoustic emission signal collector, and the acoustic emission signal is output to the voltage amplifier, the voltage amplifier performs noise reduction and amplification processing on the acoustic emission signal and then outputs it to the PLC controller, the PLC controller samples the input analog signal, converts the analog signal into a digital signal through digital-to-analog conversion and stores it in the register; the rock sample deformation sensor is connected to the EDC controller, and the EDC controller is connected to the testing machine servo actuator at the same time; the PLC controller is synchronously interconnected with the EDC controller and connected to the computer.

[0027] Step 2: Set the initial deformation rate control amount and the monitoring threshold of the acoustic emission signal characteristic parameters of the rock fracture process on the computer, including the impact rate, amplitude, energy release rate, and count. Then the computer issues a loading instruction, and the servo actuator of the testing machine loads the rock sample in the pressure chamber of the rock testing machine. At the same time, the acoustic emission sensor collects the rock sample fracture signal, which is transmitted to the voltage amplifier by the acoustic emission signal collector and then transmitted to the PLC controller after noise reduction and amplification processing by the voltage amplifier.

[0028] Step 3: The PLC controller samples the acoustic emission signal, converts the analog signal into a digital signal through digital-to-analog conversion and stores it in the register. After calculation by the incremental digital PID control algorithm, the rock deformation control rate is adaptively changed, and the deformation rate control signal matching the rock fracture information is output to the EDC controller;

[0029] The incremental digital PID control algorithm specifically comprises the following steps:

[0030] Step S1: Initialize PID parameters, including the proportional coefficient K p , integral coefficient K i , differential coefficient K d , as well as the error variable e(k), the previous error variable e(k-1), the previous previous error variable e(k-2) and the output variable Δu.

[0031] Step S2: Read the current feedback value y and the expected value y_set, and calculate the error variable e = y_set - y.

[0032] Step S3: Calculate the output variable Δu(k) = K p Δe(k)+ K i e(k)+ K d [Δe(k)-Δe(k-1)].

[0033] Where Δe(k)=e(k)-e(k-1).

[0034] Step S4: sending the output variable Δu(k) into the deformation control rate instruction;

[0035] Step S5: Update error variables e(k)=e(k+1), e(k-1)=e(k), e(k-2)=e(k-1);

[0036] Step S6: If the test is not finished, return to step 2, otherwise continue to execute.

[0037] Step 4: The EDC controller receives the deformation rate control signal, adjusts the deformation rate of the rock sample, and judges whether the size of the deformation instruction meets the set deformation rate range of different fracture stages. If not, step 3 is repeated to adjust the deformation rate of the rock sample, and then it is transmitted to the servo actuator of the testing machine through closed-loop servo feedback to further adjust the rock loading and unloading rate and loading force, thereby adjusting the energy release rate of rock fracture to meet the needs of stable control.

[0038] In this embodiment, an adaptive coordinated control loading and unloading method based on rock fracture information is implemented based on an adaptive coordinated control loading and unloading system based on rock fracture information. Figure 2 As shown, it includes: an acoustic emission sensor, an acoustic emission signal collector, a rock sample deformation sensor, a pressure sensor, an actuator displacement sensor, a rock sample fixture, a voltage amplifier, a PLC controller, an EDC controller, a computer, and a rock testing machine;

[0039] The rock testing machine model used in this embodiment is Lavender TTT508;

[0040] A rock sample is arranged in the pressure chamber of the rock testing machine, the acoustic emission sensor is arranged on the rock sample, the acoustic emission sensor is connected to the acoustic emission signal collector, the output end of the acoustic emission signal collector is connected to a voltage amplifier, and the voltage amplifier is connected to a PLC controller;

[0041] The acoustic emission signal collector is set according to the requirements;

[0042] A PLC controller is used for collecting acoustic emission signals and adjusting and outputting deformation control commands; the PLC controller is synchronously interconnected with the EDC controller to transmit the deformation control command to the EDC controller; and is connected to a computer;

[0043] The EDC controller is connected to the pressure sensor, the actuator displacement sensor, and the rock sample deformation sensor. The pressure sensor, the actuator displacement sensor, and the rock sample deformation sensor are all installed on the rock sample fixture. The rock sample fixture is fixed to the surface of the rock sample. The output end of the EDC controller is connected to the servo actuator of the rock testing machine. The rock sample deformation sensor and the acoustic emission sensor form a first closed-loop servo feedback system through the PLC controller and the EDC controller. The rock sample deformation sensor and the actuator displacement sensor form a second closed-loop servo feedback system through the EDC controller, which is used for adjusting the loading and unloading pressure and rate.

[0044] In this embodiment, the acoustic emission sensor is connected to the acoustic emission acquisition device, which is connected to the voltage amplifier. The voltage amplifier performs noise reduction and amplification processing on the input signal and then transmits it to the PLC controller; the deformation sensor is connected to the EDC controller, which is connected to the test machine servo actuator; the PLC controller is synchronously interconnected with the EDC controller and connected to the computer. The acoustic emission sensor detects the rock fracture signal and converts it into an electrical signal, and transmits the fracture signal to the acoustic emission acquisition device. The acoustic emission acquisition device transmits the acoustic emission signal to the voltage amplifier, which performs noise reduction and amplification processing on the signal and then transmits it to the PLC controller. The PLC controller samples the input analog signal, converts the analog signal into a digital signal through digital-to-analog conversion and stores it in a register, and calculates the output deformation control signal through a digital PID control algorithm, thereby realizing adaptive adjustment of the input control command. After receiving the deformation control instruction, the EDC controller controls the servo driver through feedback to adjust the force acting on the rock sample and realize stable control of the brittle fracture process of the rock sample.

[0045] The above description is only a preferred embodiment of the present disclosure and an explanation of the technical principles used. Those skilled in the art should understand that the scope of the invention involved in the embodiments of the present disclosure is not limited to the technical solutions formed by a specific combination of the above technical features, but should also cover other technical solutions formed by any combination of the above technical features or their equivalent features without departing from the above inventive concept. For example, the above features are replaced with (but not limited to) technical features with similar functions disclosed in the embodiments of the present disclosure to form a technical solution.

Claims

1. An adaptive coordinated control loading and unloading method based on rock fracture information, characterized in that: The following steps are involved: Step 1: Build an adaptive coordinated control loading and unloading system; Step 2: Set the initial deformation rate control amount and the monitoring threshold of the characteristic parameter of the acoustic emission signal of the rock fracture process on the computer, and then the computer sends a loading instruction to control the PLC controller; Step 3: The PLC controller samples the acoustic emission signal, converts the collected analog signal into a digital signal through digital-to-analog conversion and stores it in a register. After calculation by the incremental digital PID control algorithm, the rock deformation control rate is adaptively changed, and a deformation rate control signal matching the rock fracture information is output to the EDC controller; Step 4: The EDC controller receives the deformation rate control signal, adjusts the deformation rate of the rock sample, and determines whether the size of the deformation instruction meets the set deformation rate range of different fracture stages.

2. The method for adaptive coordinated control of loading and unloading based on rock fracture information according to claim 1 is characterized in that: Specifically, step 1 comprises the following steps: assembling the acoustic emission sensor and the rock sample deformation sensor with the rock sample and installing them in the pressure chamber of the rock testing machine; then the acoustic emission sensor is connected to the acoustic emission signal collector, and the acoustic emission signal is output to the voltage amplifier, and the voltage amplifier performs noise reduction and amplification processing on the input signal and then transmits it to the PLC controller; The rock sample deformation sensor is connected to the EDC controller, and the EDC controller is connected to the testing machine servo actuator.

3. The method for adaptive coordinated control of loading and unloading based on rock fracture information according to claim 2 is characterized in that: The PLC controller is synchronously interconnected with the EDC controller and connected to the computer.

4. The method of adaptive coordinated control of loading and unloading based on rock fracture information according to claim 1 is characterized in that: Specifically, step 2 is as follows: the rock sample in the pressure chamber of the rock testing machine is loaded by the testing machine servo actuator, and at the same time, the acoustic emission sensor collects the rock sample fracture signal, and the acoustic emission signal collector transmits it to the voltage amplifier, and the voltage amplifier performs noise reduction and amplification processing on the signal and then transmits it to the PLC controller.

5. The method of adaptive coordinated control of loading and unloading based on rock fracture information according to claim 1 is characterized in that: The characteristic parameters of the acoustic emission signal in step 2 specifically include impact rate, amplitude, energy release rate and count.

6. The method for adaptive coordinated control of loading and unloading based on rock fracture information according to claim 1 is characterized in that: The incremental digital PID control algorithm described in step 3 specifically includes the following steps: Step S1: Initialize PID parameters, including the proportional coefficient K p , integral coefficient K i , differential coefficient K d , as well as the error variable e(k), the previous error variable e(k-1), the previous previous error variable e(k-2) and the output variable Δu; Step S2: read the current feedback value y and the expected value y_set, and calculate the error variable e=y_set–y; Step S3: Calculate the output variable Δu(k)=K p Δe(k)+K i e(k)+K d [Δe(k)-Δe(k-1)]; Where Δe(k)=e(k)-e(k-1); Step S4: sending the output variable Δu(k) into the deformation control rate instruction; Step S5: Update error variables e(k)=e(k+1), e(k-1)=e(k), e(k-2)=e(k-1); Step S6: If the test is not finished, return to step S2, otherwise continue to execute.

7. The method for adaptive coordinated control of loading and unloading based on rock fracture information according to claim 1 is characterized in that: In step 4, if it does not match, step 3 is repeated to adjust the deformation rate of the rock sample, and then it is transmitted to the servo actuator of the testing machine through closed-loop servo feedback to further adjust the rock loading and unloading rate and loading force, thereby adjusting the energy release rate of rock fracture to meet the needs of stable control.

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