Channel embankment slope shallow layer leakage identification device carrying robotic dogs and implementation method of channel embankment slope shallow layer leakage identification device

Abstract

The invention relates to a channel embankment slope shallow layer leakage identification device carrying a robotic dog and an implementation method. The device comprises a bionic robotic dog, sensing equipment, a data acquisition and transmission system and an intelligent inspection and early warning system. The bionic robot dog comprises a four-footed bionic robot dog, a recorder is arranged on the back of the bionic robot dog, the sensing equipment comprises a non-contact moisture sensor which is carried on the foot of the bionic robot dog, and the data acquisition and transmission system is carried on the bionic robot dog. According to the invention, a bionic robot dog is combined with a nondestructive detection technology, moisture sensing capacitance electrodes are additionally arranged on four feet of the bionic robot dog to form an LC oscillating circuit, and circuit equipment is deployed on legs of the bionic robot dog to realize real-time detection of the moisture content of the channel embankment slope during walking; and the data acquisition and transmission system is carried on the bionic robot dog and is used for analyzing and processing data obtained by the sensing equipment so as to realize lossless leakage detection.

Description

Technical Field

[0001] The present invention relates to the field of rapid identification of risks in canal systems engineering, and particularly to a device and an implementation method for identifying shallow seepage in the slopes of canal dikes equipped with a quadruped robot. Background Art

[0002] In water diversion and dike projects, slope stability is crucial for project safety, and seepage failure is the main cause of slope failure. Therefore, regular inspections and reinforcement are required. Timely detection of early seepage hazards during the inspection process helps control the further development of the hazards. The typical form of early seepage hazards is the seepage and emergence of the outer slope, where the deep and shallow soil layers at the seepage points first show abnormal supersaturation, followed by the surface becoming wet and then clear water appearing. From this manifestation, the main goal of the inspection is to timely detect the wetness of the surface soil layer of the outer slope and the abnormal supersaturation of the underlying soil layer.

[0003] Existing seepage detection technologies can generally be divided into the drilling and sampling method and the manual inspection method. The drilling and sampling method is simple to operate and inexpensive, but the semi-destructive detection method will cause local damage to the engineering slope. At the same time, the detection time is long, the range is small, and it cannot meet the requirements of rapid measurement and large-area non-destructive detection. The manual inspection method is to install seepage meters, pressure pipes, water level gauges and other detection equipment in an embedded or semi-embedded manner on the cross-sections of important canals and dike slopes for detection. Managers need to regularly and quantitatively inspect the instruments and observe the water pressure changes in the canal cross-section to timely detect seepage phenomena. On the one hand, such seepage detection equipment cannot achieve continuous and mobile detection, nor can it perform seepage detection between cross-sections; on the other hand, when the equipment components are damaged and repaired, it will also cause disturbance to the embankment. The above inspection methods have problems such as large inspection workload and low efficiency due to the long distance and complex terrain of the dikes and canal slopes. At the same time, manual inspection also has problems such as time-consuming, low work efficiency, untimely data collection, high safety risks and subjectivity.

[0004] Chinese invention patent CN110632131A (publication date: December 31, 2019) discloses a method for monitoring seepage in canal dike projects. The invention can simultaneously obtain the geoelectric field distribution of the entire detected area at a certain time point, and can perform multiple "time-lapse" detections on the same detected area over time to monitor the evolution dynamic process of the seepage channel from non-existent to existing and from slight to severe, thereby improving the accuracy of seepage detection in canal dike projects.

[0005] The above-mentioned existing technologies have reduced the interference of human factors and on-site environment to a certain extent, improving the monitoring accuracy and work efficiency. However, they have not solved the problems of high subjectivity and difficulty in adapting to complex terrain. Based on the shortcomings of the existing leakage detection technologies, combined with the characteristics of the leakage risks of the outer slopes of dikes and channels and the advantages of bionic robot dogs in adapting to complex terrain and having convenient walking, the present invention provides a device and implementation method for shallow leakage identification of the slopes of channels and dikes equipped with robot dogs, combining bionic robot dogs with non-destructive detection technologies to solve the problem of rapid identification of seepage points on the outer slopes of dikes and channels. Summary of the Invention

[0006] The present invention provides a device and implementation method for shallow leakage identification of the slopes of channels and dikes equipped with robot dogs. The device includes a bionic robot dog, a sensing device, a data acquisition and transmission system, and an intelligent patrol and warning system.

[0007] The bionic robot dog includes a quadruped bionic robot dog with a recorder arranged on its back. The sensing device is mounted on the feet of the bionic robot dog to monitor the channels and dikes. The data acquisition and transmission system is mounted on the bionic robot dog and is used to analyze and process the data obtained by the sensing device. The intelligent patrol and warning system is mounted on the bionic robot dog.

[0008] Further, the sensing device includes a non-contact moisture sensor, which uses the difference in the dielectric constants of soil and water to identify soil moisture without the need to be closely combined with the soil body. The working frequency of the non-contact moisture sensor is 1.0 - 10 MHz, and the detection range is 50 - 100 cm. Its low-frequency penetration is strong, and it can distinguish natural soil bodies and abnormally supersaturated soil bodies.

[0009] Further, the non-contact moisture sensor is located on the feet of the bionic robot dog. It consists of two copper coils parallel to the ground to form a capacitor, and an oscillating circuit forms a circular homogenous electric field. The radius of the electric field is 0.5 m - 1.0 m, which can penetrate the underlying soil body. The electric field intensity is different under different dielectric constants, so the output voltage signals are different, which is used to distinguish natural state soil from abnormally supersaturated soil. The bionic robot dog's feet detect the saturation of the underlying soil layer in real time during walking.

[0010] Further, the legs of the bionic robot dog include outer movable joints, thigh joints, leg exoskeletons, joints, and calf parts.

[0011] A calf intelligent sensing device is arranged inside the calf part. A connecting axle pin is arranged inside the joint. The outer movable joint is located on the side of the joint away from the calf part. A thigh intelligent acquisition device is arranged near the joint inside the thigh of the bionic robot dog. The leg exoskeleton is connected to the outer movable joint, and the thigh joint is connected to the other end of the leg exoskeleton.

[0012] Further, a capacitance processing chip device is provided inside the calf intelligent sensing device, and a micro voltage measuring instrument is provided inside the thigh intelligent acquisition device;

[0013] The capacitance processing chip device is connected to the non-contact moisture sensor and the micro voltage measuring instrument, and can convert the electric field strength generated by the non-contact moisture sensor into a voltage signal, and then transmit it to the micro voltage measuring instrument. After the micro voltage measuring instrument measures the voltage signal in real time, it transmits and stores it in the recorder on the back of the robot dog.

[0014] Further, the calf intelligent sensing device, the thigh intelligent acquisition device, and the non-contact moisture sensor are connected by a connecting axle pin for easy modular replacement.

[0015] Further, the data acquisition and transmission system is linearly arranged on the feet, calves, thighs, and backs of the bionic robot dog, making full use of the carrying space of the bionic robot dog without affecting its walking and obstacle crossing.

[0016] Further, the intelligent inspection and early warning system includes a robot dog inspection path planning module and an early warning module. The robot dog inspection path planning module is used to specify corresponding inspection plans according to the size of the channel dike slope, the number of robot dogs, and the number of inspections during the inspection process. The early warning module is used to give early warnings to abnormal data that appears during the inspection process.

[0017] The implementation method of the device for identifying shallow leakage of the channel dike slope carried by the robot dog includes the following steps:

[0018] Step S1, on-site investigation; conduct on-site investigation of the channel, determine the area where leakage identification is required for the channel, calculate the path that needs to be inspected and the number of bionic robot dogs required;

[0019] Step S2, preparation work; use the frequency domain reflectometry method to form a non-contact moisture sensor with a pair of metal rings or metal rods, and connect an oscillator to form an LC oscillation circuit. Use the oscillation of this circuit to measure the change in the propagation frequency of electromagnetic waves in the dielectric; write a program so that the calf intelligent sensing device and the thigh intelligent acquisition device of the bionic robot dog can collect the data of the non-contact moisture sensor and convert it into the soil volume moisture content; according to the size of the channel dike slope, the number of bionic robot dogs, and the number of inspections, use the robot dog inspection path planning module to specify the inspection plan; enter the safety standard in the early warning module;

[0020] Step S3, assembly and debugging; place the non-contact moisture sensor on the foot of the bionic robot dog, and arrange the calf intelligent sensing device and the thigh intelligent acquisition device on the calf and thigh of the bionic robot dog respectively, and start the bionic robot dog to determine whether it can work normally;

[0021] Step S4, inspection: the assembled and fully programmed bionic robot dog is inspected according to a predetermined inspection plan; this can greatly save time and cost;

[0022] Step S5, early warning: When the data collected on-site by the bionic robot dog is higher than the safety standard, the early warning module will issue an early warning to the inspection personnel.

[0023] Compared with the prior art, the advantages and effects of this application are:

[0024] 1. The present invention combines the bionic robot dog with non-destructive detection technology and uses the dielectric principle to measure soil moisture. It can easily distinguish the moisture in the soil from the three-state mixture and significantly improve the accuracy of identifying scattered seepage points on the slope outside the channel.

[0025] 2. The present invention places an LC oscillation circuit in a non-contact moisture sensor on the foot of a bionic robot dog, and calculates and inverts the soil volume moisture content through the oscillation frequency of the circuit. This detection method effectively solves various problems in the existing channel leakage risk identification.

[0026] The above description is only an overview of the technical solution of the present application. In order to more clearly understand the technical means of the present application so that it can be implemented in accordance with the contents of the specification, and to make the above and other purposes, features and advantages of the present application more obvious and easy to understand, the following is a detailed description of the preferred embodiments of the present application in conjunction with the accompanying drawings as follows.

[0027] Based on the detailed description of the specific embodiments of the present application in combination with the accompanying drawings below, those skilled in the art will become more aware of the above and other objects, advantages and features of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings required for use in the embodiments or the prior art descriptions are briefly introduced below. Obviously, the drawings described below are some embodiments of the present application. For ordinary technicians in this field, other drawings can also be obtained based on these drawings without creative work. In all drawings, similar elements or parts are generally identified by similar reference numerals. In the drawings, each element or part is not necessarily drawn according to the actual scale.

[0029] in:

[0030] Figure 1 This is a physical picture of the shallow leakage identification device for the channel embankment slope equipped with a robot dog according to the present invention;

[0031] Figure 2 This is a structural diagram of a non-contact moisture sensor of a shallow seepage identification device for a channel embankment slope equipped with a robot dog according to the present invention;

[0032] Figure 3 The LC oscillation circuit diagram and measurement method diagram of the sensor for non-contact detection of soil moisture on the foot of the bionic robot dog of the present invention;

[0033] Figure 4 The leg structure diagram of the shallow leakage identification device for the channel embankment slope carried by the robot dog of the present invention;

[0034] Figure 5 The result diagram of the test on the water content of 500 groups of soil samples in a typical section of the Yangtze River embankment using the present application;

[0035] Reference numerals: 1 - Calf intelligent sensing device; 2 - Connecting axle pin; 3 - Outer movable joint; 4 - Thigh intelligent acquisition device; 5 - Thigh joint; 6 - Leg exoskeleton; 7 - Joint; 8 - Calf part. Detailed implementation manners

[0036] To make the objectives, technical solutions, and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, rather than all of the embodiments. In the following description, specific details such as specific configurations and components are provided only to assist in a comprehensive understanding of the embodiments of the present application. Therefore, those skilled in the art should clearly understand that various changes and modifications can be made to the embodiments described herein without departing from the scope and spirit of the present application. Additionally, descriptions of known functions and structures are omitted in the embodiments for the sake of clarity and conciseness.

[0037] It should be understood that the "one embodiment" or "the present embodiment" mentioned throughout the specification means that specific features, structures, or characteristics related to the embodiment are included in at least one embodiment of the present application. Therefore, the "one embodiment" or "the present embodiment" that appears throughout the specification does not necessarily refer to the same embodiment. In addition, these specific features, structures, or characteristics can be combined in one or more embodiments in any suitable manner.

[0038] In addition, the present application may repeat reference numerals and / or letters in different examples. This repetition is for the purpose of simplicity and clarity, and does not itself indicate the relationship between the various embodiments and / or settings discussed.

[0039] In this text, the term "and / or" is merely a description of the relationship between associated objects, indicating that there can be three relationships. For example, A and / or B can represent three situations: A exists alone, B exists alone, and both A and B exist simultaneously. In this text, the term " / and" describes another relationship between associated objects, indicating that there can be two relationships. For example, A / and B can represent two situations: A exists alone, and both A and B exist. Additionally, in this text, the character " / " generally indicates that the associated objects before and after are in an "or" relationship.

[0040] In this text, the term "at least one" is merely a description of the relationship between associated objects, indicating that there can be three relationships. For example, at least one of A and B can represent three situations: A exists alone, both A and B exist simultaneously, and B exists alone.

[0041] It should also be noted that in this text, relational terms such as first and second are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the term "comprising", "including" or any other variant thereof is intended to cover non-exclusive inclusion.

[0042] Embodiment 1

[0043] This embodiment introduces a device for identifying shallow leakage of the slope of a channel dike equipped with a robotic dog. For the physical diagram, please refer to Figure 1 , including a bionic robotic dog, a sensing device, a data acquisition and transmission system, and an intelligent inspection and early warning system;

[0044] The bionic robotic dog includes a quadruped bionic robotic dog with a recorder installed on its back. The sensing device is mounted on the feet of the bionic robotic dog to monitor the channel dike. The data acquisition and transmission system is mounted on the bionic robotic dog and is used to analyze and process the data obtained by the sensing device; the intelligent inspection and early warning system is mounted on the bionic robotic dog.

[0045] Preferably, the sensing device includes a non-contact moisture sensor, which uses the dielectric constant difference between soil and water to identify soil moisture without the need to be closely combined with the soil mass; the working frequency of the non-contact moisture sensor is 1.0 - 10 MHz, and the detection range is 50 - 100 cm. Its low-frequency penetration is strong, and it can distinguish natural soil mass and abnormal supersaturated soil mass.

[0046] Preferably, the non-contact moisture sensor is located at the foot of the bionic robot dog and consists of two copper coils parallel to the ground to form a capacitor. An oscillating circuit forms a circular homogenous electric field with an electric field radius of 0.5 m to 1.0 m, which can penetrate the underlying soil layer. The electric field intensity is different under different dielectric constants, so the output voltage signals are different, which is used to distinguish natural state soil from abnormally supersaturated soil. The bionic robot dog's foot detects the saturation of the underlying soil layer in real time during walking. For the structure diagram of the non-contact moisture sensor, please refer to Figure 2 。

[0047] Preferably, the leg of the bionic robot dog includes an outer movable joint 3, a thigh joint 5, a leg exoskeleton 6, a joint 7, and a calf 8;

[0048] A calf intelligent sensing device 1 is arranged inside the calf 8, a connecting axle pin 2 is arranged inside the joint 7, the outer movable joint 3 is located on the side of the joint 7 away from the calf 8, a thigh intelligent acquisition device 4 is arranged near the joint 7 inside the thigh of the bionic robot dog, the leg exoskeleton 6 is connected to the outer movable joint 3, and the thigh joint 5 is connected to the other end of the leg exoskeleton 6.

[0049] Preferably, a capacitance processing chip device is arranged inside the calf intelligent sensing device 1, and a micro-channel voltage measuring meter is arranged inside the thigh intelligent acquisition device 4;

[0050] The capacitance processing chip device is connected to the non-contact moisture sensor and the micro-channel voltage measuring meter, and can convert the electric field intensity generated by the non-contact moisture sensor received into a voltage signal, and then transmit it to the micro-channel voltage measuring meter. The micro-channel voltage measuring meter measures the voltage signal in real time and then transmits and stores it in the recorder on the back of the robot dog.

[0051] Preferably, the calf intelligent sensing device 1, the thigh intelligent acquisition device 4, and the non-contact moisture sensor are connected through the connecting axle pin 2 for easy modular replacement.

[0052] Preferably, the data acquisition and transmission system is linearly arranged on the foot, calf 8, thigh, and back of the bionic robot dog, making full use of the carrying space of the bionic robot dog without affecting its walking and obstacle crossing.

[0053] Preferably, the intelligent inspection and early warning system includes a robot dog inspection path planning module and an early warning module. The robot dog inspection path planning module is used to specify corresponding inspection plans according to the size of the channel embankment slope, the number of robot dogs, and the number of inspections during the inspection process. The early warning module is used to give early warnings for abnormal data that appears during the inspection process.

[0054] The technical effects achieved by this embodiment are as follows: This embodiment uses a bionic robot dog as a carrier and the dielectric principle to measure soil moisture, which can easily distinguish the moisture in the soil from the three-state mixture and significantly improve the recognition accuracy of seepage points on the outer slope of the channel.

[0055] Embodiment 2

[0056] Based on Embodiment 1, this embodiment introduces the implementation method of the shallow leakage identification device for the slopes of channel dikes equipped with robot dogs, including the following steps:

[0057] Step S1, on-site investigation; conduct an on-site investigation of the channel, determine the areas where leakage identification is required for the channel, calculate the inspection paths and the number of bionic robot dogs required;

[0058] Step S2, preparation work; use the frequency domain reflectometry method to form a non-contact moisture sensor with a pair of metal rings or metal rods, and connect an oscillator to form an LC oscillation circuit. Please refer to Figure 3 , and use the oscillation of this circuit to measure the change in the propagation frequency of electromagnetic waves in the dielectric; write a program so that the intelligent induction device 1 on the calf of the bionic robot dog and the intelligent acquisition device 4 on the thigh can collect the data of the non-contact moisture sensor and convert it into the volumetric water content of the soil; according to the size of the channel dike slope, the number of bionic robot dogs, and the number of inspections, use the robot dog inspection path planning module to specify the inspection plan; enter the safety standards in the warning module;

[0059] Step S3, assembly and debugging; place the non-contact moisture sensor on the foot of the bionic robot dog, and arrange the intelligent induction device 1 on the calf and the intelligent acquisition device 4 on the thigh of the bionic robot dog respectively, and start the bionic robot dog to determine whether it can work properly; please refer to the schematic diagram of the bionic robot dog's leg in Figure 4 ;

[0060] Step S4, inspection; use the assembled bionic robot dog with the program fully set to conduct inspections according to the predetermined inspection plan; it can greatly save time and cost;

[0061] Step S5, warning; when the data collected on-site by the bionic robot dog is higher than the safety standard, the warning module will issue a warning to the inspection personnel.

[0062] The relationship between the oscillation frequency and the capacitance response in Step S2 is:

[0063]

[0064] where f is the output frequency of the oscillator and L is the inductance value of the circuit;

[0065] The relationship between the measured oscillation frequency and the water content conversion is:

[0066]

[0067] where f a , f s , f w They are the oscillation frequencies caused by air, soil and pure water respectively.

[0068] This application uses regression analysis to obtain a scatter plot of the measured voltage value and moisture content of the non-contact moisture detection system based on 500 sets of soil sample moisture test data from a typical section of the Yangtze River embankment. Figure 5 As shown; the obtained fitting formula is:

[0069]

[0070] Among them, U is the measured voltage value of the acquisition section, and w is the soil moisture content. It can be seen that when the sensor frequency of the present invention is used, when the soil moisture content is below 0.8, the voltage value changes slightly, and starts to rise significantly after exceeding 0.8. This feature can be used to quickly identify abnormally supersaturated areas of the soil.

[0071] The technical effect achieved by this embodiment is: the present invention forms a capacitor with a pair of metal rings or metal rods and connects an oscillator to form an LC oscillation circuit, which is placed in a non-contact moisture sensor on the foot of the robot dog. The oscillation frequency of the circuit is measured and further calculated to invert the soil volume moisture content. This detection method can effectively solve various problems in the existing channel leakage risk identification.

[0072] The above description is only the preferred embodiment of the present invention, which does not limit the protection scope of the present invention. For those skilled in the art, the present invention can be modified and varied in various ways. Within the spirit and principle of the present invention, any change, modification, replacement, integration and parameter change of these embodiments by conventional substitution or capable of achieving the same function without departing from the principle and spirit of the present invention shall fall within the protection scope of the present invention.

Claims

1. A shallow seepage identification device for channel embankment slopes equipped with a robot dog, characterized in that: Including bionic robot dogs, sensor equipment, data collection and transmission systems, intelligent inspection and early warning systems; The bionic robot dog comprises a four-legged bionic robot dog, a recorder is arranged on the back of the bionic robot dog, the sensor device is mounted on the foot of the bionic robot dog, and the data collection and transmission system and the intelligent inspection and early warning system are mounted on the bionic robot dog.

2. The shallow seepage identification device for channel embankment slope equipped with a robot dog according to claim 1 is characterized in that: The sensing device comprises a non-contact moisture sensor, the working frequency of the non-contact moisture sensor is 1.0-10 MHz, and the detection range is 50-100 cm.

3. The shallow seepage identification device for channel embankment slope equipped with a robot dog according to claim 2 is characterized in that: The non-contact moisture sensor is located at the foot of the bionic robot dog. It is composed of two copper coils parallel to the ground to form a capacitor. An annular homologous electric field is formed through an oscillation circuit. The electric field radius is 0.5m to 1.0m. The bionic robot dog can detect the saturation of the soil layer below in real time while walking.

4. The shallow seepage identification device for channel embankment slope equipped with a robot dog according to claim 1 is characterized in that: The bionic robot dog leg comprises an external movable joint (3), a thigh joint (5), a leg exoskeleton (6), a joint (7), and a calf (8); The calf part (8) is provided with a calf intelligent sensing device (1), the joint (7) is provided with a connecting shaft pin (2), the external movable joint (3) is located on the side of the joint (7) away from the calf part (8), a thigh intelligent acquisition device (4) is provided at a position near the joint (7) in the thigh of the bionic robot dog, the leg exoskeleton (6) is connected to the external movable joint (3), and the thigh joint (5) is connected to the other end of the leg exoskeleton (6).

5. The shallow seepage identification device for channel embankment slope equipped with a robot dog according to claim 3 or 4, characterized in that: The calf intelligent sensing device (1) is provided with a capacitance processing chip device, and the thigh intelligent collection device (4) is provided with a WeChat voltage measurement meter; The capacitance processing chip device is connected to a non-contact moisture sensor and a WeChat voltage measuring meter.

6. The shallow seepage identification device for channel embankment slope equipped with a robot dog according to claim 5 is characterized in that: The calf intelligent sensing device (1), the thigh intelligent collection device (4), and the non-contact moisture sensor are connected via a connecting shaft pin (2).

7. The shallow seepage identification device for channel embankment slope equipped with a robot dog according to claim 1 is characterized in that: The data acquisition and transmission system is linearly arranged on the foot, calf (8), thigh and back of the bionic robot dog.

8. The shallow seepage identification device for channel embankment slope equipped with a robot dog according to claim 1 is characterized in that: The intelligent inspection and early warning system includes a robot dog inspection path planning module and an early warning module.

9. The implementation method of the channel embankment slope shallow leakage identification device equipped with a robot dog according to any one of claims 1 to 8 is characterized in that: The following steps are involved: Step S1, on-site investigation; Conduct on-site surveys of the channel to determine the areas where leakage identification is required, calculate the routes that need to be inspected and the number of bionic robot dogs required; Step S2, preparation work; using the frequency domain reflection method to form a pair of metal rings or metal rods into a non-contact moisture sensor, and connecting an oscillator to form an LC oscillation circuit, using the oscillation of the circuit to measure the change in the propagation frequency of electromagnetic waves in the dielectric; writing a program so that the calf intelligent sensing device (1) and the thigh intelligent collection device (4) of the bionic robot dog can collect data from the non-contact moisture sensor and convert it into soil volume moisture content; according to the size of the channel embankment slope, the number of bionic robot dogs, and the number of inspections, the robot dog inspection path planning module is used to specify the inspection plan; and the safety standards are entered into the early warning module; Step S3, assembly and debugging; placing a non-contact moisture sensor on the foot of the bionic robot dog, and arranging a calf intelligent sensing device (1) and a thigh intelligent collection device (4) on the calf and thigh of the bionic robot dog respectively, and starting the bionic robot dog to determine whether it can work normally; Step S4, inspection: the assembled and fully programmed bionic robot dog is inspected according to a predetermined inspection plan; Step S5: early warning; When the data collected on-site by the bionic robot dog is higher than the safety standard, the early warning module will issue an early warning to the inspection personnel.

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