A prestressed concrete slab construction cracking monitoring device

Abstract

The application is suitable for the technical field of prestressed concrete slab monitoring, and provides a prestressed concrete slab construction cracking monitoring device, which comprises a driving trolley and a measuring instrument arranged on the driving trolley and used for measuring the prestressed concrete slab. The measuring instrument is composed of a main machine, a group of transducers and sensors. The group of transducers are all fixed on the driving trolley. The main machine and the group of sensors are respectively arranged on the two sides of the group of transducers. A vertical driving mechanism is installed on the driving trolley and used for driving the group of sensors to move stably. The prestressed concrete slab construction cracking monitoring device provided by the scheme has the beneficial effects of high measuring efficiency, automatic cleaning of measuring points, flexible adjustment of sensor spacing and non-destructive testing, and can effectively evaluate the structural quality and damage degree of the prestressed concrete slab, thereby providing strong technical support for the safety monitoring and maintenance of engineering structures.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of prestressed concrete slab monitoring, and particularly relates to a prestressed concrete slab construction cracking monitoring device. BACKGROUND

[0002] At present, the prestressed concrete slab cracking monitoring device mostly uses a concrete ultrasonic detector, which is a non-destructive testing equipment for evaluating the prestressed concrete slab structure quality and damage degree. The equipment uses ultrasonic technology to measure the sound velocity and attenuation in concrete, so as to infer the compactness, strength and existing defects and damage of the concrete.

[0003] At present, the monitoring device is directly placed on the construction site during use, and then the dust on the surface of the measured concrete slab is cleaned, and relevant parameters such as the measurement mode, measurement range, and the distance between the transmitting transducer and the receiving transducer are set on the instrument, and then the prestressed concrete slab can be measured.

[0004] However, since multiple point measurements are required when measuring the prestressed concrete slab, the monitoring device needs to be frequently moved, and the distance between the transmitting transducer and the receiving transducer also needs to be adjusted again, which results in low measurement efficiency. The patent document with the authorization announcement number CN204439140U has the above-mentioned problems. SUMMARY

[0005] The application provides a prestressed concrete slab construction cracking monitoring device, which aims to solve the problem that the currently used monitoring device cannot quickly perform measurement work when performing multiple point measurements.

[0006] To solve the above problems, the application is implemented as follows: a prestressed concrete slab construction cracking monitoring device, comprising: a driving trolley and a measuring instrument arranged on the driving trolley for measuring a prestressed concrete slab, the measuring instrument is composed of a main machine, a group of transducers and sensors, a group of the transducers are fixed on the driving trolley, and the main machine and a group of the sensors are arranged on both sides of a group of the transducers; a vertical driving mechanism installed on the driving trolley for driving a group of sensors to move stably; a bidirectional electric guide rail arranged on the vertical driving mechanism for adjusting the distance between a group of sensors; and a cleaning brush arranged below the driving trolley for cleaning dust and impurities on the surface of the prestressed concrete slab.

[0007] Preferably, the driving trolley is composed of a vehicle body, a gimbal camera, an autonomous navigation system and a controller, the gimbal camera, the autonomous navigation system and the controller are arranged on the vehicle body, and the gimbal camera and the controller are respectively arranged at the front and rear ends of the vehicle body.

[0008] Preferably, the vertical driving mechanism comprises a support frame fixedly installed on the vehicle body, a mounting frame installed on the top of the support frame, a unidirectional screw rotatably installed in the mounting frame for driving the bidirectional electric guide rail to slide up and down, the bottom end of the unidirectional screw extending into the support frame, a sliding block threadedly sleeved on the unidirectional screw, the sliding block being connected with the bidirectional electric guide rail, a motor installed on the driving trolley for driving the unidirectional screw to rotate, the output shaft of the motor being rotatably connected with the support frame, and a set of bevel gears fixedly sleeved on the output shaft of the motor and the unidirectional screw, the bevel gears being in engagement.

[0009] Preferably, a set of connecting plates are arranged on the bidirectional electric guide rail, a sleeve is fixedly installed on each of the connecting plates, a buffer spring for buffering the downward sliding force of the connecting plate is fixedly installed in the sleeve, and a fixing member for installing a sensor is installed at the bottom end of the buffer spring.

[0010] Preferably, a through opening is formed in the vehicle body, the through opening being located directly below the sensor, a support plate is fixedly installed on the bottom of the vehicle body, a round rod is rotatably installed on the support plate, a connecting mechanism for synchronously driving the round rod and the unidirectional screw to rotate is arranged on the round rod and the unidirectional screw, a rectangular telescopic cylinder is installed at the bottom end of the round rod, and the rectangular telescopic cylinder is connected with the cleaning brush.

[0011] Preferably, the connecting mechanism comprises a mounting groove formed in the bottom of the vehicle body, a rectangular telescopic rod installed at the top end of the round rod, a set of discs fixedly installed at one end of the rectangular telescopic rod and the unidirectional screw, the discs being closely fitted, an electric push rod fixedly installed at one side of the mounting groove for driving the rectangular telescopic rod to extend and retract, and a connecting frame installed on the electric push rod, the connecting frame being rotatably connected with the rectangular telescopic rod.

[0012] Preferably, a disc is fixedly installed at the top end of the round rod, an annular frame matched with the disc is installed at the bottom of the connecting frame, and the annular frame is sleeved on the rectangular telescopic rod.

[0013] Preferably, an anti-skid pad is installed on each of the discs and the disc, a plurality of clamping strips are installed on the other disc and the annular frame, and the clamping strips are matched with the two anti-skid pads respectively.

[0014] Preferably, an electric telescopic rod for adjusting the height of the cleaning brush is fixedly installed on one side of the support plate, a fixing frame is installed on the electric telescopic rod, and the fixing frame is rotatably connected with the rectangular telescopic cylinder.

[0015] Preferably, a placing rack is mounted on the top of the vehicle body, the placing rack is located at one side of the controller, and the placing rack is used for placing a host computer, and a screw rod for fixing the host computer is screw-mounted on one side of the placing rack.

[0016] Compared with the related art, the prestressed concrete slab construction cracking monitoring device provided by the application has the following beneficial effects:

[0017] Compared with the prior art, the prestressed concrete slab construction cracking monitoring device provided by the present application realizes the rapid movement and accurate positioning of the measuring instrument and the automatic lifting of the sensor through the cooperation of the driving trolley and the vertical driving mechanism, thereby greatly improving the measurement efficiency and reducing the time for manual carrying and adjustment. At the same time, the cleaning brush arranged can clean the dust or impurities on the measuring point while the sensor slides downward, ensuring the accuracy of measurement and avoiding measurement errors caused by dust or impurities interference.

[0018] Through the adjustment of the bidirectional electric guide rail, the spacing between a group of sensors can be flexibly adjusted according to different measuring point positions and measurement requirements, so as to adapt to the measurement requirements of prestressed concrete slabs of different sizes. The measuring instrument in the embodiment uses ultrasonic technology for measurement and will not cause any damage to the prestressed concrete slab, which is a non-destructive testing method and is beneficial to the safety and integrity of the engineering structure.

[0019] In summary, the prestressed concrete slab construction cracking monitoring device of the application has the beneficial effects of high measurement efficiency, automatic cleaning of measuring points, flexible adjustment of sensor spacing, and non-destructive testing, and can effectively evaluate the structural quality and damage degree of the prestressed concrete slab, thereby providing strong technical support for the safety monitoring and maintenance of engineering structures. BRIEF DESCRIPTION OF DRAWINGS

[0020] Figure 1 is a front view structural schematic diagram of a prestressed concrete slab construction cracking monitoring device provided by the application;

[0021] Figure 2 is a front view structural schematic diagram of a prestressed concrete slab construction cracking monitoring device provided by the application;

[0022] Figure 3 is a partial front view structural schematic diagram of a prestressed concrete slab construction cracking monitoring device provided by the application;

[0023] Figure 4 is an assembly drawing of a bidirectional electric guide rail, a connecting plate, a fixing member and a sensor provided by the application;

[0024] Figure 5 is a top view structural schematic diagram of a liquid storage box, a hose and a guide frame provided by the application;

[0025] Figure 6 is a top view structural schematic diagram of the middle chain wheel, limit wheel and chain provided by the present application;

[0026] Figure 7 is a top view structural schematic diagram of the middle installation cylinder, touch rod and control switch provided by the present application;

[0027] Figure 8 is a three-dimensional structural schematic diagram of the vehicle body provided by the present application;

[0028] Figure 9 is a three-dimensional structural schematic diagram of the round rod, rectangular telescopic cylinder and cleaning brush provided by the present application;

[0029] Figure 10 is a three-dimensional structural schematic diagram of the placement rack and screw rod provided by the present application;

[0030] Figure 11 is an enlarged structural schematic diagram of the A part shown in the figure; Figure 3

[0031] is an enlarged structural schematic diagram of the B part shown in the figure; Figure 12 Figure 2 is an enlarged structural schematic diagram of the C part shown in the figure.

[0032] Figure 13 Figure 3

[0033] Fig. 1 is a driving trolley; 101 is a vehicle body; 102 is a gimbal camera; 103 is an autonomous navigation system; 104 is a controller; 2 is a measuring instrument; 201 is a main machine; 202 is a transducer; 203 is a sensor; 3 is a vertical driving mechanism; 301 is a one-way screw rod; 302 is a sliding block; 303 is a motor; 304 is a bevel gear; 305 is a support frame; 4 is a two-way electric guide rail; 5 is a connecting plate; 6 is a cleaning brush; 7 is a through port; 8 is a support plate; 9 is a round rod; 10 is a rectangular telescopic cylinder; 11 is a rectangular telescopic rod; 12 is a disc; 13 is an electric push rod; 14 is a connecting frame; 15 is a round plate; 16 is an annular frame; 17 is an anti-skid pad; 18 is a clamping strip; 19 is an electric telescopic rod; 20 is a fixing frame; 21 is a placement rack; 22 is a screw rod; 23 is a fixing piece; 24 is a sleeve; 25 is a buffer spring; 26 is a liquid storage box; 27 is a hose; 28 is a liquid discharge pipe; 29 is a water pump; 30 is a guide rod; 31 is a return spring; 32 is a connecting block; 33 is a support; 34 is a rotating rod; 35 is a chain wheel; 36 is a limit wheel; 37 is a chain; 38 is a take-up stick; 39 is a steel wire rope; 40 is an installation cavity; 41 is an installation cylinder; 42 is a touch rod; 43 is a torsional spring; 44 is a control switch; 45 is a limiting rod; 46 is a guide frame; 47 is a glass observation window. DETAILED DESCRIPTION ​​​

[0034] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs; the terminology used in the description herein is for describing particular embodiments only and is not intended to be limiting of the application. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs; the terminology used in the description herein is for describing particular embodiments only and is not intended to be limiting of the application. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs; the terminology used in the description herein is for describing particular embodiments only and is not intended to be limiting of the application. The terminology used in the description herein is for describing particular embodiments only and is not intended to be limiting of the application. The terms "comprising," "having," "including," and "containing" are to be construed open-ended, unless otherwise noted. The terms "first," "second," and the like, as used herein do not have any specific one-to-one correspondence with the terms "one," "two," and the like, as these terms are used to distinguish between different objects, rather than to describe a specific sequential or chronological order. The terms "inner," "outer," "left," "right," "front," "back," "up," "down," "top," "bottom," "over," "under," and the like as used herein are made only with reference to the figures as drawn and are not intended to be limiting in any way. The terms "about" and "substantially" used herein are understood not to be absolute terms of exactitude.

[0035] Reference herein to "an embodiment" means that a particular feature, structure, or characteristic described in connection with the embodiment can be included in at least one embodiment of the application. The appearances of the phrase "in one embodiment" in various places in the specification are not necessarily all referring to the same embodiment, nor are they necessarily all directed to the same embodiment, or to a single alternative embodiment. It is expressly understood that any of the embodiments described herein can be combined with any of the other embodiments.

[0036] The prestressed concrete slab construction cracking monitoring device provided by the embodiments of the application comprises a driving trolley 1 and a measuring instrument 2 arranged on the driving trolley 1 and used for measuring a prestressed concrete slab, the measuring instrument 2 is composed of a main machine 201, a group of transducers 202 and sensors 203, the group of transducers 202 are all fixed on the driving trolley 1, and the main machine 201 and the group of sensors 203 are arranged on the two sides of the group of transducers 202 respectively. Figures 1-13 The vertical driving mechanism 3 arranged on the driving trolley 1 is used for driving the group of sensors 203 to move stably, the bidirectional electric guide rail 4 arranged on the vertical driving mechanism 3 is used for adjusting the spacing between the group of sensors 203, and the cleaning brush 6 arranged below the driving trolley 1 is used for cleaning dust and impurities on the surface of the prestressed concrete slab.

[0037] In this embodiment, in use, first, the measuring instrument 2 is moved to the designated measurement position by driving the trolley 1, the measuring instrument 2 is composed of a host machine 201, a set of transducers 202 and sensors 203, which are used to emit and receive ultrasonic waves to measure the speed and attenuation of sound in concrete, and then according to the measurement point position, the controller 104 on the driving trolley 1 is controlled to control the bidirectional electric guide rail 4 to adjust the spacing of the set of sensors 203, after adjustment, the vertical driving mechanism 3 is started to make the vertical driving mechanism 3 drive the set of sensors 203 to slide smoothly, while the set of sensors 203 slide, the cleaning brush 6 cleans the dust or impurities on the measurement point directly below the set of sensors 203, when the set of sensors 203 touch the ground, the staff operates the host machine 201 to perform measurement work;

[0038] The set of sensors 203 are respectively receiving sensors and transmitting sensors, during measurement, the host machine 201 sends a short pulse to the transmitting sensor 203, causing the transmitting sensor 203 to vibrate and generate ultrasonic waves, the ultrasonic waves propagate in concrete at a certain speed, and when encountering different material interfaces or defects, reflection or refraction occurs, the propagation speed of the sound wave depends on multiple factors such as the density, water content and strength of the concrete.

[0039] When the sound wave encounters the interface, crack or other defect in the concrete, part of the sound wave will be reflected back, and another part of the sound wave will continue to propagate in different directions, the receiving sensor 203 will receive the reflected sound wave and convert it into an electrical signal, the receiver will record the sound wave propagation time and intensity change for subsequent analysis and evaluation, through analysis and interpretation of the collected sound wave data, the quality, cracking condition, compactness and possible defects or structural damage of the concrete can be evaluated.

[0040] After measurement, the vertical driving mechanism 3 drives the sensor 203 to slide up and away from the pre-stressed concrete slab, then the controller 104 is operated to start the driving trolley 1, so that the driving trolley 1 automatically goes to the next measurement point to perform multi-measurement point measurement work;

[0041] Through the cooperation of the driving trolley 1 and the vertical driving mechanism 3, the rapid movement and accurate positioning of the measuring instrument 2 and the automatic lifting of the sensor 203 are realized, thereby greatly improving the measurement efficiency and reducing the time for manual carrying and adjustment, at the same time, the cleaning brush 6 set can clean the dust or impurities on the measurement point while the sensor 203 slides down, ensuring the accuracy of measurement and avoiding measurement errors caused by dust or impurities interference.

[0042] Through the adjustment of the bidirectional electric guide rail 4, the spacing between a group of sensors 203 can be flexibly adjusted according to different measuring point positions and measuring requirements, so as to adapt to the measuring requirements of prestressed concrete plates of different sizes. The measuring instrument 2 in the embodiment uses ultrasonic technology for measurement and does not cause any damage to the prestressed concrete plate, which is a non-destructive testing method and is beneficial to the safety and integrity of the engineering structure.

[0043] In a further preferred embodiment of the application, the driving trolley 1 is composed of a trolley body 101, a gimbal camera 102, an autonomous navigation system 103 and a controller 104, the gimbal camera 102, the autonomous navigation system 103 and the controller 104 are all arranged on the trolley body 101, and the gimbal camera 102 and the controller 104 are respectively arranged at the front and rear ends of the trolley body 101.

[0044] In the embodiment, during the measurement process, the driving trolley 1 first plans and navigates to the designated measuring position through the autonomous navigation system 103, after reaching the position, the gimbal camera 102 starts to monitor and shoot the on-site environment in real time, ensuring that the staff can clearly see the situation of the measuring site, then according to the measuring point position, the staff adjusts the spacing of a group of sensors 203 through the controller 104 controlling the bidirectional electric guide rail 4, after the adjustment, the vertical driving mechanism 3 is started to make the vertical driving mechanism 3 drive a group of sensors 203 to smoothly slide to the surface of the prestressed concrete plate, while the sensors 203 are sliding down, the cleaning brush 6 cleans the dust or impurities on the measuring point directly below the sensors;

[0045] When the sensors 203 touch the ground, the staff measures through the controller 104 operating the host 201, after the measurement is completed, the vertical driving mechanism 3 drives the sensors 203 to slide up away from the concrete plate, and then the driving trolley 1 automatically goes to the next measuring point for measurement under the guidance of the autonomous navigation system 103;

[0046] The gimbal camera 102 monitors and shoots the on-site environment in real time by flexibly adjusting the shooting angle and focal length, the gimbal camera 102 can capture key information and provide intuitive on-site pictures, which is helpful for the staff to remotely monitor the measurement process and timely discover and handle abnormal situations. The autonomous navigation system 103 uses advanced navigation technologies such as SLAM (simultaneous localization and mapping), GPS, etc. to realize the autonomous navigation and positioning of the driving trolley 1, the autonomous navigation system 103 can plan the optimal path to ensure that the driving trolley 1 quickly and accurately reaches the designated measuring position. The controller 104 is responsible for receiving and processing information from the gimbal camera 102, the autonomous navigation system 103 and the measuring instrument 2, etc., and controls the movement of the driving trolley 1, the lifting of the measuring instrument 2, the adjustment of the spacing of the sensors 203, etc. according to the preset program or the operation instructions of the staff;

[0047] The automatic navigation and positioning of the driving trolley 1 are realized through the autonomous navigation system 103 and the controller 104, the time for manual carrying and adjustment is reduced, the measurement efficiency is greatly improved, the pan-tilt camera 102 can flexibly adjust the shooting angle and focal length, the real-time monitoring and shooting of the on-site environment are realized, and intuitive on-site pictures are provided, which is helpful for the staff to timely find and handle abnormal situations.

[0048] In further preferable embodiments of the application, the vertical driving mechanism 3 comprises a support frame 305 fixedly installed on the vehicle body 101, a mounting frame installed on the top of the support frame 305, a unidirectional screw 301 rotatably installed in the mounting frame and used to drive the bidirectional electric guide rail 4 to slide up and down, the bottom end of the unidirectional screw 301 extending into the support frame 305, a sliding block 302 threadedly sleeved on the unidirectional screw 301 and connected with the bidirectional electric guide rail 4, a motor 303 installed on the driving trolley 1 and used to drive the unidirectional screw 301 to rotate, the output shaft of the motor 303 being rotatably connected with the support frame 305, and a set of bevel gears 304 fixedly sleeved on the output shaft of the motor 303 and the unidirectional screw 301, respectively, and engaged with each other.

[0049] In the embodiment, when it is necessary to adjust the height of the sensor 203, the motor 303 is started and drives its output shaft to rotate, the unidirectional screw 301 also starts to rotate through the transmission of the bevel gears 304, and when the unidirectional screw 301 rotates, the sliding block 302 slides up and down along the thread direction of the unidirectional screw 301 due to the threaded sleeve of the sliding block 302 on the unidirectional screw 301, the up-and-down sliding of the sliding block 302 drives the up-and-down movement of the bidirectional electric guide rail 4 and the sensor 203 and other components connected with the sliding block 302, so as to realize the adjustment of the height of the sensor 203, and when the sensor 203 slides down to the ground, the host 201 can be operated to perform the measurement operation.

[0050] The vertical driving mechanism 3 is composed of the support frame 305, the mounting frame, the unidirectional screw 301, the sliding block 302, the motor 303 and the bevel gears 304, so as to realize the accurate adjustment of the height of the sensor 203 while keeping the compactness of the structure, facilitating the installation and fixation on the driving trolley 1.

[0051] Through the driving of the motor 303 and the transmission of the bevel gears 304, the rotation of the unidirectional screw 301 and the up-and-down sliding of the sliding block 302 can be conveniently realized, so as to quickly adjust the height of the sensor 203. This adjustment mode is not only simple and convenient to operate, but also has high adjustment accuracy, and has high stability and reliability due to the threaded connection and the transmission of the bevel gears 304. In the measurement process, the stability and accuracy of the sensor 203 can be maintained even if it is disturbed or vibrated by the outside.

[0052] Specifically, the vertical driving mechanism 3 can adjust the height of the sensor 203 according to actual needs, adapt to the measurement requirements of prestressed concrete slabs of different sizes and surface unevenness, and has high automation degree and flexibility due to the adoption of advanced technologies such as motor 303 driving and bevel gear 304 transmission.

[0053] In the further preferred embodiment of the application, the bidirectional electric guide rail 4 is provided with a set of connecting plates 5, each of which is fixedly installed with a sleeve 24, and the sleeve 24 is fixedly installed with a buffer spring 25 for buffering the impact force of the connecting plate 5 sliding downward, and the bottom end of the buffer spring 25 is installed with a fixing piece 23 for installing the sensor 203.

[0054] In the measurement process in this embodiment, the vertical driving mechanism 3 drives the connecting plate 5 and the components (including the sleeve 24, the buffer spring 25 and the sensor fixing piece 23) thereon to slide downward to the surface of the prestressed concrete slab, and when the sensor 203 touches the ground, due to the elastic effect of the buffer spring 25, it will absorb and buffer the impact force of the connecting plate 5 sliding downward, thereby protecting the sensor 203 from being damaged, and at the same time, this buffering effect also helps to ensure that the sensor 203 can stably and accurately contact the surface of the concrete slab, improving the accuracy and reliability of the measurement.

[0055] The arrangement of the buffer spring 25 effectively absorbs the impact force of the connecting plate 5 sliding downward, protects the sensor 203 from being damaged, prolongs the service life of the sensor, and through the buffering effect of the buffer spring 25, ensures that the sensor 203 can stably and accurately contact the surface of the concrete slab, avoids measurement errors caused by impact, and improves the accuracy and reliability of the measurement.

[0056] Through the combination of the connecting plate 5, the sleeve 24 and the buffer spring 25 and other components, the structural stability of the entire measuring device is enhanced, so that it can maintain a stable state during measurement, further improving the accuracy of measurement.

[0057] Specifically, since the buffer spring 25 has a certain range of elasticity, it can adapt to the surfaces of concrete slabs of different hardness and roughness, improving the adaptability and flexibility of the measuring device.

[0058] Further preferably, a through hole 7 is formed in the vehicle body 101, the through hole 7 is located directly below the sensor 203, a support plate 8 is fixedly installed at the bottom of the vehicle body 101, a round rod 9 is rotatably installed on the support plate 8, a connecting mechanism for synchronously driving the rotation of the round rod 9 and the one-way screw rod 301 is arranged on the round rod 9 and the one-way screw rod 301, and a rectangular telescopic cylinder 10 is installed at the bottom end of the round rod 9 and connected with the cleaning brush 6.

[0059] In this embodiment, when it is necessary to clean dust and impurities on the concrete plate, the motor 303 is started to drive the one-way screw rod 301 to rotate, and through the transmission of the connecting mechanism, the round rod 9 also synchronously rotates. The rotation of the round rod 9 drives the rotation of the rectangular telescopic cylinder 10 and the cleaning brush 6, so that the cleaning operation on the concrete plate is started, and the rotation of the cleaning brush 6 can effectively remove dust and impurities from the surface of the concrete plate, thereby providing a clean and accurate measurement environment for subsequent measurement operations.

[0060] The rotation of the one-way screw rod 301 is driven by the motor 303, and the round rod 9 and the cleaning brush 6 are synchronously rotated through the connecting mechanism, so that the automatic cleaning function in the measurement process is realized, thereby greatly reducing the time and labor cost of manual cleaning, improving the measurement efficiency, and the rotation of the cleaning brush 6 can timely clean the dust and impurities on the concrete plate, thereby avoiding the influence of these impurities on the measurement result, and helping to improve the accuracy and reliability of the measurement.

[0061] Specifically, the entire cleaning mechanism (including the support plate 8, the round rod 9, the connecting mechanism, the rectangular telescopic cylinder 10, and the cleaning brush 6) is compactly installed at the bottom of the vehicle body 101, does not occupy additional space, and at the same time maintains the stability and reliability of the measuring instrument 2. The design of the rectangular telescopic cylinder 10 allows the cleaning brush 6 to be retracted to a certain extent when needed to adapt to the movement of the driving trolley 1.

[0062] Further preferably, the connecting mechanism comprises: a mounting groove formed in the bottom of the vehicle body 101; a rectangular telescopic rod 11 installed at the top end of the round rod 9; a group of circular discs 12 fixedly installed at one end of the rectangular telescopic rod 11 and the one-way screw rod 301 respectively, and the circular discs 12 are closely attached; an electric push rod 13 fixedly installed on one side of the mounting groove for driving the telescopic movement of the rectangular telescopic rod 11; and a connecting frame 14 installed on the electric push rod 13, the connecting frame 14 being rotatably connected with the rectangular telescopic rod 11.

[0063] In this embodiment, when it is necessary to clean the dust and impurities on the concrete slab, the electric push rod 13 is started and drives the rectangular telescopic rod 11 to telescope towards the unidirectional screw rod 301, so that the two groups of circular discs 12 are tightly attached. At this time, the rotation of the unidirectional screw rod 301 will drive the circular rod 9 to rotate synchronously, and then drive the cleaning brush 6 to start rotating and clean the concrete slab through the rectangular telescopic cylinder 10.

[0064] When the sensor 203 gradually slides along the preset path to the preset height (controlled by the controller 104 preset program), the electric push rod 13 is started and drives the rectangular telescopic rod 11 to telescope from top to bottom. This action causes the two groups of circular discs 12 installed on the rectangular telescopic rod 11 and one end of the unidirectional screw rod 301 to move away from each other, thereby breaking the linkage between them. Since the linkage between the circular discs 12 is broken, the rotation of the unidirectional screw rod 301 can no longer drive the circular rod 9 and the cleaning brush 6 to rotate synchronously, so the cleaning brush 6 stops rotating, avoiding collision with the sliding sensor 203. After the cleaning brush 6 stops rotating, the sensor 203 continues to slide and contacts the measured point for measurement;

[0065] By accurately controlling the separation time of the circular discs 12 and the stopping rotation of the cleaning brush 6, the collision between the sensor 203 and the cleaning brush 6 can be effectively avoided, which helps to protect the sensor 203 and the cleaning brush 6 from damage, while ensuring the accuracy and safety of the measurement. The stopping rotation of the cleaning brush 6 reduces the interference factors in the measurement process, so that the sensor 203 can more accurately contact the measured point and measure, which helps to improve the accuracy and reliability of the measurement.

[0066] In a further preferred embodiment of the application, the top end of the circular rod 9 is fixedly installed with a circular plate 15, and the bottom of the connecting frame 14 is installed with a ring-shaped frame 16 matched with the circular plate 15, and the ring-shaped frame 16 is sleeved on the rectangular telescopic rod 11.

[0067] In this embodiment, when the cleaning brush 6 needs to rotate away from below the passageway 7 (for example, when the sensor 203 gradually slides along the preset path to the preset height), the electric push rod 13 first drives the rectangular telescopic rod 11 to contract, so that the two groups of circular discs 12 move away from each other, thereby breaking the linkage between the unidirectional screw rod 301 and the circular rod 9, and stopping the rotation of the cleaning brush 6.

[0068] At the same time of the separation of the circular discs 12, the connecting frame 14 and the ring-shaped frame 16 slide downward synchronously, and when the ring-shaped frame 16 slides to contact the circular plate 15, it will stably position the circular rod 9, ensuring that the cleaning brush 6 will not be displaced due to external force or vibration in the static state, thereby ensuring that the position of the cleaning brush 6 is not below the passageway 7 when the circular discs 12 are disconnected;

[0069] The electric push rod 13 has a double function, one is to drive the rectangular telescopic rod 11 to perform telescopic movement to control the adhesion and separation of the disc 12, and the other is to drive the connecting frame 14 and the annular frame 16 to slide up and down to realize the positioning of the circular rod 9, which can ensure that the cleaning brush 6 will not be displaced due to external force or vibration after stopping rotating, improve the stability and measurement accuracy of the equipment, and through the rapid and accurate adjustment of the adhesion and separation state of the disc 12 and the up and down sliding position of the annular frame 16, the electric push rod 13 in the embodiment can efficiently control the rotation and positioning of the cleaning brush 6, which helps to reduce the waiting time and operation complexity in the measurement process, thereby improving the measurement efficiency.

[0070] In further preferred embodiments of the application, a non-slip pad 17 is mounted on each of the discs 12 and the circular plate 15, and a plurality of clamping strips 18 are mounted on the other disc 12 and the annular frame 16, and the plurality of clamping strips 18 are respectively matched with the two non-slip pads 17.

[0071] In the embodiment, when the unidirectional screw (through the disc 12 thereon) rotates, due to the close contact and high friction of the non-slip pad 17 and the clamping strip 18, the circular plate 15 (and the circular rod 9 thereon) will be driven to rotate synchronously, and the design of the non-slip pad 17 and the clamping strip 18 ensures that the disc 12 and the circular plate 15 will not slip or dislocate even under high load or high-speed rotation, and the matching design of the clamping strip 18 and the non-slip pad 17 not only increases the friction, but also provides additional connection stability, when the discs 12 are close to each other and adhere to each other, the clamping strip 18 will be embedded in the groove of the non-slip pad 17, forming a firm connection structure, which helps to prevent the discs 12 from separating due to external force or vibration during rotation;

[0072] By increasing the friction and providing additional connection stability, the design of the non-slip pad 17 and the clamping strip 18 significantly improves the reliability of the synchronous rotation between the unidirectional screw 301 and the circular rod 9, which helps to ensure the accuracy and stability of the measurement process, and due to the design of the non-slip pad 17 and the clamping strip 18, the connection between the disc 12 and the circular plate 15 is more firm and reliable, and the operator only needs to perform measurement operation without worrying about the problem of connection failure or slipping, which helps to reduce the operation difficulty and improve the measurement efficiency.

[0073] In further preferred embodiments of the application, an electric telescopic rod 19 for adjusting the height of the cleaning brush 6 is fixedly installed on one side of the support plate 8, a fixed frame 20 is installed on the electric telescopic rod 19, and the fixed frame 20 is rotationally connected with the rectangular telescopic cylinder 10.

[0074] In the embodiment, when the height of the cleaning brush 6 needs to be adjusted, the electric telescopic rod 19 is extended or shortened according to the preset program or operation instruction, when the electric telescopic rod 19 is shortened, the fixed frame 20 and the rectangular telescopic cylinder 10 are moved downward as a whole, so that the cleaning brush 6 is away from the surface of the concrete slab, on the contrary, when the electric telescopic rod 19 is extended, the cleaning brush 6 is close to the surface of the concrete slab, by accurately adjusting the height of the cleaning brush 6, it can be ensured that the sensor 203 is not disturbed by the cleaning brush 6 when contacting the measured point, which helps to improve the accuracy and precision of measurement.

[0075] In the further preferred embodiment of the application, a placing rack 21 is mounted on the top of the vehicle body 101, the placing rack 21 is located on one side of the controller 104, and the placing rack 21 is used for placing the host computer 201, and a screw rod 22 for fixing the host computer 201 is screw-mounted on one side of the placing rack 21.

[0076] In the embodiment, in the preparation stage, the operator places the host computer 201 on the placing rack 21 and tightens it by rotating the screw rod 22, so that the host computer 201 is firmly fixed on the placing rack 21. In this way, the host computer 201 will not be displaced due to vibration or external force during the operation of the driving trolley 1. The host computer 201 is connected to the controller 104, the transducer 202 and other components through the connecting line, receives the measurement data from the sensor 203, and controls the operation of the equipment according to the preset program or operation instruction. When the host computer 201 needs to be maintained or replaced, the operator only needs to loosen the screw rod 22 to easily disassemble the host computer from the placing rack 21. Through the design of the placing rack 21 and the screw rod 22, the stability and reliability of the host computer 201 during the operation of the equipment can be ensured.

[0077] In order to further improve the use effect of the device, in addition to the above-mentioned scheme, the present scheme also has the following embodiments:

[0078] In another embodiment of the application, a liquid discharge mechanism for automatically discharging coupling agent is arranged on the driving trolley 1, the liquid discharge mechanism comprises: a liquid storage box 26 fixedly installed at the bottom of the vehicle body 101 and used for storing coupling agent; a hose 27 installed on one side of the liquid storage box 26; a liquid discharge pipe 28 installed on the hose 27 and used for discharging coupling agent; and a water pump 29 installed in the liquid storage box 26 and used for conveying coupling agent, wherein the output end of the water pump 29 is fixedly connected with the hose 27.

[0079] In the embodiment, the water pump 29 is started at regular time intervals while the sensor 203 is sliding downward, and the water pump 29 discharges the coupling agent in the liquid storage box 26 through the hose 27 and the liquid discharge pipe 28. At this time, the liquid discharge pipe 28 is arranged below the through opening 7 and initially located at the left side of the center position of the through opening 7.

[0080] With the rotation of the round rod 9, the drain pipe 28 is driven to move to the right side through the chain transmission system, so that the drain pipe 28 can be slid and accurately located directly below the through opening 7, ensuring that the coupling agent can be accurately discharged to the required position, and in the process of rotation of the round rod 9, the drain pipe 28 continuously slides to one side, ensuring that the drain pipe 28 can always be located in the correct discharge position, and avoiding contact with the sensor 203, thereby ensuring the normal movement and detection accuracy of the sensor 203;

[0081] Through the timing start of the water pump 29 and the control of the chain transmission system, automatic discharge of the coupling agent is realized, greatly improving the work efficiency, and the drain pipe 28 can be accurately slid to the position directly below the through opening 7 for discharge, ensuring that the coupling agent can accurately reach the required position, and the drain pipe 28 always avoids contact with the sensor 203 in the sliding process, ensuring the normal movement and detection accuracy of the sensor 203.

[0082] In another embodiment of the application, a guide groove is formed in the bottom of the vehicle body 101, a guide rod 30 is fixedly installed in the guide groove, a return spring 31 and a connecting block 32 are sleeved on the guide rod 30, and a support 33 for supporting the drain pipe 28 is fixedly installed at the bottom of the connecting block 32.

[0083] In this embodiment, in the initial state, the return spring 31 is in a released state, the connecting block 32 supports the drain pipe 28 through the support 33, so that the drain pipe 28 is kept in a certain position, when the coupling agent needs to be discharged, the water pump 29 is started to convey the coupling agent to the drain pipe 28 through the hose 27, and at the same time, the connecting block 32 is driven to slide along the guide rod 30 by the round rod 9 through the chain transmission system, since the support 33 is fixedly connected with the connecting block 32, the drain pipe 28 will also move with the movement of the connecting block 32, so as to compress the return spring 31, when the round rod 9 stops rotating, the annular frame 16 is in close contact with the circular plate 15, thereby fixing the positions of the round rod 9 and the drain pipe 28, ensuring that the cleaning brush 6 and the drain pipe 28 will not affect the downward sliding of the sensor 203, through the combined design of the guide groove, the guide rod 30, the return spring 31 and the connecting block 32, the movement of the drain pipe 28 is more stable and reliable, avoiding the problem of inaccurate discharge caused by unstable movement, through the cooperation of the chain transmission system and the return spring 31, automatic movement and reset of the drain pipe 28 are realized, greatly improving the work efficiency.

[0084] In another embodiment of the present application, the bottom of the vehicle body 101 is provided with an adjusting mechanism for adjusting the position of the drain pipe 28, which comprises: a plurality of rotating rods 34 rotatably installed on the bottom of the vehicle body 101; a chain wheel 35 and a limiting wheel 36 fixedly sleeved on the round rod 9 and the plurality of rotating rods 34 respectively; a chain 37 sleeved on the chain wheel 35 and the limiting wheel 36 for synchronously driving the round rod 9 and the plurality of rotating rods 34 to rotate synchronously, the chain 37 being engaged with the chain wheel 35 and the limiting wheel 36; a take-up stick 38 fixedly installed at the bottom end of any one of the rotating rods 34, the take-up stick 38 being provided with a steel wire rope 39, one end of the steel wire rope 39 being fixedly connected with the support 33.

[0085] In the present embodiment, when the round rod 9 starts to rotate, the cleaning brush 6 synchronously cleans the ground, since the chain 37 is engaged with the chain wheel 35 and the limiting wheel 36, the rotation of the round rod 9 drives the chain 37, the limiting wheel 36 and the rotating rod 34 to rotate synchronously. At this time, the take-up stick 38 also starts to rotate and winds the steel wire rope 39. The winding of the steel wire rope 39 drives the support 33 and the drain pipe 28 to slide to the right until reaching a predetermined position, when the drain pipe 28 slides to the right to the position directly below the through hole 7, the water pump 29 is started to discharge the coupling agent.

[0086] After the draining is completed, the drain pipe 28 continuously slides to the right until the round rod 9 stops rotating, when the sensor 203 slides back to the predetermined height and then the two discs 12 are tightly attached to each other, the sensor 203 and the drain pipe 28 are synchronously reset.

[0087] In another embodiment of the present application, the vehicle body 101 is provided with an installation cavity 40, one end of the rotating rod 34 located on the take-up stick 38 extending into the installation cavity 40, the installation cavity 40 being provided with a control mechanism for controlling the opening and closing of the water pump 29, the control mechanism comprising: an installation cylinder 41 arranged in the installation cavity 40, the bottom end of the installation cylinder 41 being fixedly connected with the rotating rod 34; a touch rod 42 rotatably sleeved on the installation cylinder 41; a control switch 44 fixedly installed on one side of the installation cavity 40 for controlling the opening and closing of the water pump 29; a torsional spring 43 fixedly installed in the installation cylinder 41, the top end of the torsional spring 43 movably penetrating through the touch rod 42; a plurality of limiting rods 45 fixedly installed in the installation cavity 40 for limiting the rotating angle of the touch rod 42, the plurality of limiting rods 45 being arranged on both sides of the touch rod 42 respectively.

[0088] In the initial state, the lever 42 is kept in a certain position (such as the position away from the control switch 44) under the action of the torsion spring 43. At this time, the water pump 29 is in the closed state, and when the rotating rod 34 rotates, the mounting cylinder 41 is fixedly connected with the rotating rod 34, so that the mounting cylinder 41 also rotates. The rotation of the mounting cylinder 41 drives the lever 42 to rotate. When the lever 42 rotates to a certain angle, it will contact the control switch 44 and the limiting rod 45;

[0089] When the lever 42 contacts the control switch 44, the switch action is triggered, thereby controlling the water pump 29 to start. At this time, the water pump 29 starts to work and discharges the coupling agent through the hose 27 and the drainage pipe 28. At the same time that the lever 42 contacts the control switch 44, it is also limited by the limiting rod 45 to prevent excessive rotation. When the water pump 29 discharges for a certain time (such as a few seconds), the control switch 44 automatically closes the water pump 29. At this time, although the lever 42 still continuously contacts the control switch 44, the control switch 44 has been matched with the circuit board to realize the automatic closing function, so the water pump 29 will not start again. Subsequently, through the reset of the drainage pipe 28 and the restoring force of the torsion spring 43, the lever 42 starts to reset, preparing for the next triggering action. Through the contact and separation of the lever 42 and the control switch 44, the automatic control of the water pump 29 is realized without manual intervention. Through the design of the limiting rod 45, the rotation angle of the lever 42 is limited, thereby ensuring that the start and stop time of the water pump 29 is accurately controllable.

[0090] In a further preferred embodiment of the application, one side of the liquid storage box 26 is fixedly provided with a guide frame 46. The guide frame 46 is composed of a plurality of clamping plates hinged together. The guide frame 46 is fixedly connected with the hose 27.

[0091] In the embodiment, when the drainage pipe 28 slides to the right, the hose 27 also moves with the movement of the drainage pipe 28 because the hose 27 is fixedly connected with the guide frame 46. At this time, the relative rotation between the clamping plates of the guide frame 46 occurs, so that the guide frame 46 as a whole bends to the back side (i.e. the side opposite to the movement direction of the drainage pipe 28). This bending ensures that the hose 27 will not be in a slack state and touch the ground during the movement, thereby avoiding damage of the hose 27 due to friction or extrusion. After the drainage is completed, the drainage pipe 28 returns to the initial position. At this time, the guide frame 46 gradually returns to the initial shape due to its flexibility and deformability, and drives the hose 27 to reset. Through the design of the guide frame 46, it is ensured that the hose 27 will not touch the ground during the movement, thereby avoiding the risk of damage of the hose 27 due to friction or extrusion. Through the design of the guide frame 46, the movement of the hose 27 is more stable and controllable, thereby avoiding the problem of inaccurate or unstable drainage due to the slack of the hose 27.

[0092] Further preferably, the liquid storage box 26 is provided with a glass observation window 47 on one side for observing the liquid storage condition of the liquid storage box 26, and a cover is threadedly installed on one side of the liquid storage box 26.

[0093] In the embodiment, when the user needs to observe the liquid storage condition inside the liquid storage box 26, the user can directly observe the remaining amount of the coupling agent through the glass observation window 47, which enables the user to know the storage condition of the coupling agent without opening the liquid storage box 26, thereby avoiding the risk of leakage or contamination of the coupling agent due to frequent opening of the liquid storage box 26. When the coupling agent in the liquid storage box 26 is insufficient, the user needs to open the threaded cover, add the coupling agent into the liquid storage box 26, and then tighten the threaded cover after the addition is completed, so as to ensure the sealing of the liquid storage box 26. This design enables the user to conveniently add or replace the coupling agent, while ensuring the sealing and safety of the liquid storage box 26.

[0094] To sum up, compared with the related art, the device has the beneficial effects of high measurement efficiency, automatic cleaning of measurement points, flexible adjustment of sensor spacing, and non-destructive testing, and can effectively evaluate the structural quality and damage degree of the prestressed concrete slab, thereby providing strong technical support for safety monitoring and maintenance of engineering structures.

[0095] In several embodiments provided in the present application, it should be understood that the disclosed device can be implemented in other ways.

[0096] The above embodiments are only used to illustrate the technical solutions of the present application, and not to limit the protection scope of the application. Obviously, the described embodiments are only some of the embodiments of the present application, not all the embodiments. Based on these embodiments, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of the present application. Although the present application has been described in detail with reference to the above embodiments, those skilled in the art can combine, add or delete the features of the embodiments according to the circumstances without creative labor, so as to obtain different technical solutions which do not deviate from the concept of the present application in essence. These technical solutions also belong to the scope of the present application.

Claims

1. A device for monitoring cracking in construction of a prestressed concrete slab, characterized in that, The utility model relates to a kind of pre-stressed concrete plate measuring device, including: Driving trolley (1) and be arranged in the driving trolley (1) for measuring pre-stressed concrete plate measuring instrument (2), the measuring instrument (2) is by host computer (201), a group of transducers (202) and sensor (203) are formed, a group of the transducer (202) are fixed on the driving trolley (1), the host computer (201) and a group of the sensor (203) are respectively arranged in a group of the transducer (202) two sides; Vertically driving mechanism (3) for driving a group of sensors (203) to move stably is installed on the driving trolley (1); Bidirectional electric guide rail (4) for adjusting the spacing of a group of sensors (203) is arranged on the vertically driving mechanism (3); Cleaning brush (6) for cleaning the surface impurities of pre-stressed concrete plate is arranged below the driving trolley (1); The driving trolley (1) is composed of a vehicle body (101), a gimbal camera (102), an autonomous navigation system (103) and a controller (104); A support plate (8) is fixedly installed on the bottom of the vehicle body (101), and a round rod (9) is rotatably installed on the support plate (8); The driving trolley (1) is provided with a drainage mechanism for automatically draining coupling agent, which comprises a liquid storage box (26) fixedly installed on the bottom of the vehicle body (101) for storing coupling agent, a hose (27) installed on one side of the liquid storage box (26), a drainage pipe (28) installed on the hose (27) for discharging coupling agent, and a water pump (29) installed in the liquid storage box (26) for conveying coupling agent, wherein the output end of the water pump (29) is fixedly connected with the hose (27); An adjusting mechanism for adjusting the position of the drainage pipe (28) is arranged on the bottom of the vehicle body (101), which comprises a plurality of rotating rods (34) rotatably installed on the bottom of the vehicle body (101), a chain wheel (35) and a limiting wheel (36) fixedly sleeved on the round rod (9) and the plurality of rotating rods (34), respectively, a chain (37) sleeved on the chain wheel (35) and the limiting wheel (36) for synchronously driving the round rod (9) and the plurality of rotating rods (34) to rotate synchronously, the chain (37) is engaged with the chain wheel (35) and the limiting wheel (36), and a take-up stick (38) is fixedly installed at the bottom end of any one of the rotating rods (34), and a steel wire rope (39) is installed on the take-up stick (38).

2. The pre-stressed concrete slab construction cracking monitoring apparatus of claim 1, wherein, The gimbal camera (102), the autonomous navigation system (103) and the controller (104) are arranged on the vehicle body (101), and the gimbal camera (102) and the controller (104) are respectively arranged at the front and rear ends of the vehicle body (101).

3. The apparatus for monitoring cracking in construction of a prestressed concrete slab according to claim 2, wherein The vertically driving mechanism (3) comprises: A support frame (305) is fixedly installed on the vehicle body (101), and a mounting bracket is installed on the top of the support frame (305); A one-way screw (301) is rotatably installed in the mounting bracket for driving the bidirectional electric guide rail (4) to slide up and down, and the bottom end of the one-way screw (301) extends into the support frame (305); A slider (302) is sleeved on the one-way screw rod (301), and the slider (302) is connected with the bidirectional electric guide rail (4); A motor (303) for driving the one-way screw rod (301) to rotate is mounted on the driving trolley (1), and an output shaft of the motor (303) is rotationally connected with the support frame (305); A group of bevel gears (304) are fixedly sleeved on the output shaft of the motor (303) and the one-way screw rod (301) respectively, and the bevel gears (304) are in engagement.

4. The apparatus for monitoring cracking in construction of a prestressed concrete slab as recited in claim 1, wherein A group of connecting plates (5) are arranged on the bidirectional electric guide rail (4), a sleeve (24) is fixedly mounted on each connecting plate (5), a buffer spring (25) for buffering the downward sliding force of the connecting plate (5) is fixedly mounted in the sleeve (24), and a fixing member (23) for mounting a sensor (203) is mounted at the bottom end of the buffer spring (25).

5. The apparatus for monitoring cracking in construction of a prestressed concrete slab as recited in claim 3, wherein A through opening (7) is formed in the trolley body (101), the through opening (7) is located directly below the sensor (203), a connecting mechanism for synchronously driving the rotation of the round rod (9) and the one-way screw rod (301) is arranged on the round rod (9) and the one-way screw rod (301), and a rectangular telescopic cylinder (10) is mounted at the bottom end of the round rod (9), and the rectangular telescopic cylinder (10) is connected with the cleaning brush (6).

6. The pre-stressed concrete slab construction cracking monitoring apparatus of claim 5, wherein, The connecting mechanism comprises: a mounting groove formed in the bottom of the trolley body (101); a rectangular telescopic rod (11) mounted at the top end of the round rod (9); a group of discs (12) fixedly mounted at one end of the rectangular telescopic rod (11) and the one-way screw rod (301) respectively, and the discs (12) are closely fitted; an electric push rod (13) fixedly mounted at one side of the mounting groove and used for driving the telescopic movement of the rectangular telescopic rod (11); and a connecting frame (14) mounted on the electric push rod (13) and rotationally connected with the rectangular telescopic rod (11).

7. The pre-stressed concrete slab construction cracking monitoring apparatus of claim 6, wherein, A disc (15) is fixedly mounted at the top end of the round rod (9), a ring-shaped frame (16) matched with the disc (15) is mounted at the bottom of the connecting frame (14), and the ring-shaped frame (16) is sleeved on the rectangular telescopic rod (11).

8. The pre-stressed concrete slab construction cracking monitoring apparatus of claim 7, wherein, Anti-skid pads (17) are mounted on any one of the discs (12) and the disc (15), and a plurality of clamping strips (18) are mounted on the other disc (12) and the ring-shaped frame (16), and the clamping strips (18) are matched with the two anti-skid pads (17) respectively.

9. The pre-stressed concrete slab construction cracking monitoring apparatus of claim 5, wherein, An electric telescopic rod (19) for adjusting the height of the cleaning brush (6) is fixedly mounted on one side of the support plate (8), a fixing frame (20) is mounted on the electric telescopic rod (19), and the fixing frame (20) is rotationally connected with the rectangular telescopic cylinder (10).

10. The apparatus for monitoring cracking in construction of a prestressed concrete slab as defined in claim 2, wherein The top of the vehicle body (101) is provided with a rack (21), the rack (21) is located on one side of the controller (104), and the rack (21) is used for placing a host computer (201), and one side of the rack (21) is screw-mounted with a screw rod (22) for fixing the host computer (201).

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