Foundation pit micro-disturbance control system based on improved servo support and working method of foundation pit micro-disturbance control system

Abstract

The invention discloses a foundation pit micro-disturbance control system based on improved servo support and a working method thereof. The foundation pit micro-disturbance control system comprises a double-outlet-rod hydraulic oil cylinder, a controller and a computer. The double-outlet-rod hydraulic oil cylinder is arranged between the inner ring beam and the outer ring beam and comprises an outer shell and hydraulic oil cylinders arranged in the outer shell side by side; the controller is electrically connected with the FBG pressure sensor, an optical fiber demodulator is arranged in the controller, the optical fiber demodulator receives the optical signal and converts the optical signal into a pressure signal, and the controller converts the pressure signal into a pressure value according to a pre-calibrated pressure-wavelength curve and transmits the pressure value to a computer; and the computer is used for controlling hydraulic drive in the hydraulic oil cylinder according to the received pressure value. The optical fiber Bragg grating (FBG) pressure sensor is directly embedded into the inner wall of an oil cylinder cavity, all-optical sensing and transmission of pressure signals are achieved, the electro-hydraulic conversion link of a traditional pressure transmitter is eliminated, and an optical-mechanical-hydraulic coupling model is finally established through an optical-hydraulic direct drive interface, an optical fiber signal transmission system and an anti-interference design.

Description

Technical Field

[0001] This application relates to the technical field of foundation pit construction, and specifically belongs to a foundation pit micro-disturbance control system based on improved servo support and its working method. Background Technique

[0002] The excavation and unloading of soil in the foundation pit will cause the deformation of the surrounding soil. Therefore, the retaining structure needs to continuously support to reduce the impact on surrounding sensitive buildings (structures). The electro-hydraulic servo support system plays a role in detecting and supporting on the side wall of the foundation pit. However, the traditional electro-hydraulic servo support system has two major defects. One is the response delay, and the electro-hydraulic conversion link causes signal transmission delay. The other is the insufficient control accuracy. The non-linear characteristics of the hydraulic system cause control errors and it is difficult to meet the deformation control requirements of millimeters. Traditional hydraulic jacks may have problems such as slow response speed and insufficient long-term stability. Especially for important infrastructure in sensitive construction environments, such as deep foundation pit projects near subway tunnels and historical buildings, the control requirements for surrounding ground settlement are high. Summary of the Invention

[0003] The purpose of the present invention is to provide a foundation pit micro-disturbance control system based on improved servo support and its working method. By constructing a distributed optical fiber-servo collaborative network, a "perception-decision-instruction" closed loop is realized, and stable support of the foundation pit support system by the hydraulic cylinder is achieved.

[0004] To achieve the above purpose, the present invention adopts the following technical solutions: A foundation pit micro-disturbance control system based on improved servo support, characterized in that it includes a double-rod hydraulic cylinder, a controller and a computer; Double-rod hydraulic cylinder: a strictly symmetrical device, arranged between the inner ring beam and the outer ring beam, including an outer shell and hydraulic cylinders arranged side by side in the outer shell. The output ends of the two hydraulic cylinders are connected to the same ejector rod, and the ejector rod is tightly attached to the side wall of the outer ring beam, and the ejector rod and the center of the outer ring beam coincide on the same horizontal line; an FBG pressure sensor is embedded at the bottom of the hydraulic cylinder to realize the optical fiber perception and transmission of the pressure signal, and the pressure value is transmitted to the controller through the optical signal; Controller: electrically connected to the FBG pressure sensor, with an optical fiber demodulator built-in. The optical fiber demodulator receives the optical signal and converts it into a pressure signal. The controller converts the pressure signal into a pressure value according to the pre-calibrated pressure-wavelength curve and transmits it to the computer; Computer: controls the hydraulic drive in the hydraulic cylinder according to the received pressure value, so that the oil cylinder pressure value is kept within 31.5 * 0.75 MPa and the axial thrust value is kept within 2000 * 0.75 kN.

[0005] Further preferably, the double-rod hydraulic cylinder has a cylinder diameter of 80 mm, a rod diameter of 45 mm, a stroke of ±100 mm, and a maximum output force of 200 kN.

[0006] Further, the fiber optic demodulator is internally provided with a photodetector to convert the optical signal into an electrical signal, and the output rod in the double-rod hydraulic cylinder is symmetrically arranged up and down relative to the outer ring beam through ADC digitization.

[0007] In addition, the bottom of the hydraulic cylinder is machined with a micro-groove with a width of 0.3 mm × a depth of 0.2 mm by a five-axis laser engraving machine for installing the FBG pressure sensor. The micro-groove is located on the inner wall surface of the oil inlet cavity of the hydraulic cylinder far from the output end. Each hydraulic cylinder is provided with an FBG pressure sensor, and they are symmetrically arranged relative to the hydraulic cylinder.

[0008] A working method of a foundation pit micro-disturbance control system based on an improved servo support, characterized by comprising the following steps: The FBG pressure sensor receives the pressure signal from the hydraulic cylinder to achieve all-optical perception of the pressure signal, converts the pressure signal into an optical signal, that is, a wavelength signal, and transmits the optical signal to the fiber optic demodulator of the controller. The fiber optic demodulator converts the optical signal into a pressure signal, that is, an electrical signal. The controller converts the electrical signal into a pressure value according to the pre-calibrated pressure-wavelength curve and displays it on the computer. The computer outputs a signal to drive the servo valve to adjust the hydraulic oil flow and pressure, push the piston of the cylinder to move, keep the cylinder pressure value within 31.5 * 0.75 MPa, and keep the axial thrust value within 2000 * 0.75 kN, establish an optical-mechanical-hydraulic coupling model, and achieve precise mapping of fiber optic strain-hydraulic oil pressure-mechanical deformation.

[0009] Compared with the prior art, the present invention has the following characteristics and beneficial effects: In view of the problems of lagging response and insufficient control accuracy of the traditional electro-hydraulic servo support, this application designs a double-rod symmetric hydraulic cylinder (cylinder diameter 80 mm / rod diameter 45 mm, stroke ±100 mm), and eliminates the non-linearity of the output force through the equal cross-sectional area structure of the double piston rods; adopts the five-axis laser engraving and micro-welding process to directly embed the fiber Bragg grating (FBG) pressure sensor into the inner wall of the cylinder cavity to achieve all-optical perception and transmission of the pressure signal and eliminate the electro-hydraulic conversion link of the traditional pressure transmitter; This application constructs a distributed fiber optic-servo collaborative network to achieve a closed loop of "perception - decision - instruction". Through the design of the double-rod symmetric cylinder, the development of a high-precision sensing system and a control module, through the optical-hydraulic direct drive interface, the fiber optic signal transmission system and the anti-interference design, finally establish an optical-mechanical-hydraulic coupling model to achieve precise mapping of fiber optic strain-hydraulic oil pressure-mechanical deformation, and provides a more refined solution for the construction of deep foundation pit projects in urban sensitive environments. Description of the Drawings

[0010] Figure 1 This is a schematic diagram of the double-rod hydraulic cylinder involved in the present application; Figure 2 This is a specific application diagram involved in the present application; Figure 3 This is a diagram of the working signal transmission involved in the present application.

[0011] Reference numerals: 1 - double-rod hydraulic cylinder; 11 - outer housing; 12 - hydraulic cylinder; 13 - ejector rod; 2 - controller; 3 - computer; 4 - inner ring beam; 5 - outer ring beam; 6 - FBG pressure sensor. Specific embodiments

[0012] To make the technical means, innovative features, achieved purposes and effects of the present invention easy to understand, the present invention will be further described below.

[0013] The embodiments described herein are specific specific embodiments of the present invention for explaining the concept of the present invention, and are all explanatory and exemplary, and should not be construed as limiting the embodiments of the present invention and the scope of the present invention. Except for the embodiments described herein, those skilled in the art can also adopt other obvious technical solutions based on the content disclosed in the claims and the specification of the present application, and these technical solutions include technical solutions that make any obvious substitutions and modifications to the embodiments described herein.

[0014] Embodiment 1 A foundation pit micro-disturbance control system based on an improved servo support, as Figures 1 - 3 shown, includes a double-rod hydraulic cylinder 1, a controller 2 and a computer 3; Double-rod hydraulic cylinder 1: A strictly symmetrical device arranged between the inner ring beam 4 and the outer ring beam 5, including an outer housing 11 and hydraulic cylinders 12 arranged side by side in the outer housing 11. The output ends of the two hydraulic cylinders 12 are connected to the same ejector rod 13, and the ejector rod 13 is closely attached to the side wall of the outer ring beam 5 and the center of the ejector rod 13 coincides with the outer ring beam 5 on the same horizontal line; an FBG pressure sensor 6 (fiber Bragg grating pressure sensor) is embedded at the bottom of the hydraulic cylinder 12 to realize the fiber perception and transmission of the pressure signal, and the pressure value is transmitted to the controller 2 through the optical signal; Controller 2: Electrically connected to the FBG pressure sensor 6, in a wired connection manner, and is internally provided with a fiber optic demodulator. The fiber optic demodulator receives the optical signal (fiber optic signal) and converts it into a pressure signal. The controller 2 converts the pressure signal into a pressure value according to the pre-calibrated pressure-wavelength curve and transmits it to the computer 3; specifically, the fiber optic demodulator is internally provided with a photodetector to convert the optical signal into an electrical signal and digitize it through an ADC (analog-to-digital converter). The output rods in the double-rod hydraulic cylinder 1 are symmetrically arranged up and down with respect to the outer ring beam 5.

[0015] Working principle of fiber Bragg grating (FBG) pressure sensor: The FBG sensor reflects light of a specific wavelength through the grating. When the external pressure changes, the period and refractive index of the grating will change, resulting in a shift in the reflected wavelength. This wavelength change can be detected by a demodulator and converted into the corresponding pressure or strain value.

[0016] Computer 5: Electrically connected to the controller, with a wired connection method. It controls the hydraulic drive in the hydraulic cylinder 12 according to the received pressure value, so that the cylinder pressure value is kept within 31.5 * 0.75 MPa, and the axial thrust value is kept within 2000 * 0.75 kN.

[0017] In this embodiment, the double-rod hydraulic cylinder 1 has a cylinder diameter of 80 mm, a rod diameter of 45 mm, a stroke of ±100 mm, and a maximum output force of 200 kN, which can be extended to the 500 kN level.

[0018] In this embodiment, a micro-groove with a width of 0.3 mm × a depth of 0.2 mm is machined at the bottom of the hydraulic cylinder 12 by a five-axis laser engraving machine for installing the FBG pressure sensor 6. The micro-groove is located on the inner wall surface of the oil inlet cavity of the hydraulic cylinder 12 away from the output end. One FBG pressure sensor 6 is arranged for each hydraulic cylinder 12 and is symmetrically arranged relative to the hydraulic cylinder 12.

[0019] Embodiment 2 Based on Embodiment 1, the FBG pressure sensors are arranged in an array along the perimeter of the foundation pit with the double-rod hydraulic cylinder 1 for real-time monitoring to ensure that both the cylinder pressure value and the axial thrust value of the double-rod hydraulic cylinder 1 are kept within 75%. The double-rod hydraulic cylinder is driven to adjust the supporting force according to the signal instruction, and the foundation pit deformation is controlled within ±0.5 mm. The foundation pit deformation needs to be detected in cooperation with the foundation pit deformation monitoring system. The fiber optic signal transmission adopts the all-optical relay technology to avoid the introduction of noise caused by the conversion of electrical signals. The fiber optic signal is connected to the servo actuator controller to realize the control of the servo actuator itself.

[0020] The fiber Bragg grating Bragg pressure sensing adopts a direct embedding design. A micro-groove (width 0.3 mm × depth 0.2 mm) is pre-machined on the inner wall of the cylinder. The micro-groove is machined by a five-axis laser engraving machine (accuracy ±5 μm). The FBG sensor (central wavelength 1550 nm) is encapsulated on the front cavity wall of the cylinder, and the laser micro-welding process (weld width 0.2 mm) is adopted. For the double-rod cylinder, one FBG pressure sensor is arranged on each side of the cylinder. The double FBG pressure sensors can realize redundant monitoring, while the traditional cylinder only has single-sided sensing.

[0021] Optical-fluid direct drive interface, the fiber Bragg grating (FBG) pressure sensor is directly embedded in the oil inlet chamber of the oil cylinder (range 0-40 MPa, wavelength demodulation frequency 1 kHz) to achieve all-optical perception of pressure signals.

[0022] The controller is equipped with an optical interface module. The optical signal (wavelength) is transmitted to the optical interface module of the controller through single-mode / multi-mode optical fiber, which can effectively avoid electromagnetic interference. Specifically, the optical fiber signal transmission adopts all-optical relay technology to avoid noise introduced by electrical signal conversion; the controller converts the wavelength offset into the actual pressure value according to the pre-calibrated pressure-wavelength relationship curve and displays it on the computer.

[0023] The computer executes: driving the double-rod hydraulic cylinder to adjust the supporting force according to the signal instruction, controlling the foundation pit deformation within ±0.5 mm, and dynamically adjusting the parameters according to the real-time pressure data to adapt to the changes, and finally forming a closed-loop feedback.

[0024] Embodiment 3 Based on Embodiment 1, this embodiment provides a working method of a foundation pit micro-disturbance control system based on an improved servo support, including the following steps. The FBG pressure sensor 6 receives the pressure signal from the hydraulic cylinder 12 to achieve all-optical perception of the pressure signal, converts the pressure signal into an optical signal, that is, a wavelength signal, and transmits the optical signal to the fiber optic demodulator of the controller 2. The fiber optic demodulator converts the optical signal into a pressure signal, that is, an electrical signal. The controller converts the electrical signal into a pressure value according to the pre-calibrated pressure-wavelength curve and displays it on the computer 3. The computer 3 outputs a signal to drive the servo valve to adjust the hydraulic oil flow and pressure, and push the piston of the oil cylinder to move, so that the pressure value of the oil cylinder is kept within 31.5 * 0.75 MPa and the axial thrust value is kept within 2000 * 0.75 kN, and an optical-mechanical-fluid coupling model is established to achieve accurate mapping of fiber optic strain - oil pressure - mechanical deformation.

[0025] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A foundation pit micro-disturbance control system based on improved servo support, characterized in that: It comprises a double-rod hydraulic cylinder (1), a controller (2) and a computer (3); The double-rod hydraulic cylinder (1) is a strictly symmetrical device, arranged between the inner ring beam (4) and the outer ring beam (5), and comprises an outer shell (11) and a hydraulic cylinder (12) arranged side by side in the outer shell (11). The output ends of the two hydraulic cylinders (12) are connected to the same push rod (13). The push rod (13) is arranged in close contact with the side wall of the outer ring beam (5), and the push rod (13) and the center of the outer ring beam (5) coincide on the same horizontal line. An FBG pressure sensor (6) is embedded at the bottom of the hydraulic cylinder (12) to realize optical fiber sensing and transmission of pressure signals, and transmit the pressure value to the controller (2) through optical signals. Controller (2): electrically connected to the FBG pressure sensor (6), having a built-in optical fiber demodulator, which receives the optical signal and converts it into a pressure signal. The controller (2) converts the pressure signal into a pressure value according to a pre-calibrated pressure-wavelength curve and transmits it to the computer (3); Computer (5): controls the hydraulic drive in the hydraulic cylinder (12) according to the received pressure value, so that the cylinder pressure value is maintained within 31.5*0.75MPa and the axial thrust value is maintained within 2000*0.75kN.

2. A foundation pit micro-disturbance control system based on improved servo support as claimed in claim 1, characterized in that: Double-rod hydraulic cylinder (1) with a bore of 80 mm, a cylinder diameter of 45 mm, a stroke of ±100 mm, and a maximum output of 200 kN (expandable to 500 kN).

3. The foundation pit micro-disturbance control system based on improved servo support as claimed in claim 1, characterized in that: The optical fiber demodulator has a built-in photoelectric detector, which converts the optical signal into an electrical signal and digitizes it through an ADC. The output rods in the double-rod hydraulic cylinder (1) are symmetrically arranged with respect to the outer ring beam (5).

4. The foundation pit micro-disturbance control system based on improved servo support as claimed in claim 1, characterized in that: The bottom of the hydraulic cylinder (12) is processed by a five-axis laser engraving machine to have a micro-groove with a width of 0.3 mm and a depth of 0.2 mm, for mounting an FBG pressure sensor (6). The micro-groove is located on the oil inlet chamber and the inner wall surface of the hydraulic cylinder (12) away from the output end. Each hydraulic cylinder (12) is provided with an FBG pressure sensor (6), and the FBG pressure sensor (6) is symmetrically arranged relative to the hydraulic cylinder (12).

5. A working method of a foundation pit micro-disturbance control system based on an improved servo support as claimed in any one of claims 1 to 4, characterized in that: The following steps are included: The FBG pressure sensor (6) receives the pressure signal from the hydraulic cylinder (12), realizes full optical perception of the pressure signal, converts the pressure signal into an optical signal, that is, a wavelength signal, and transmits the optical signal to the optical fiber demodulator of the controller (2). The optical fiber demodulator converts the optical signal into a pressure signal, that is, an electrical signal. The controller converts the electrical signal into a pressure value according to a pre-calibrated pressure-wavelength curve and displays it on the computer (3). The computer (3) outputs a signal to drive the servo valve to adjust the flow and pressure of the hydraulic oil, push the cylinder piston to move, keep the cylinder pressure value within 31.5*0.75MPa, and keep the axial thrust value within 2000*0.75kN. An optical-mechanical-fluid coupling model is established to realize accurate mapping of optical fiber strain-oil pressure-mechanical deformation.

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