CN114264986B - Near seabed magnetic gradient measurement method - Google Patents

Abstract

The invention relates to the field of ocean magnetic measurement, in particular to a near-seabed magnetic gradient measurement method. It includes the following steps, S1. Install the near-seabed magnetic gradient measurement device on the submarine; S2. Release the first-level sensor; S3. Release the second-level sensor; S4. Repeat step S3 to release the subsequent several-level sensors in sequence, thereby achieving Magnetic gradient measurement of each series sensor. It realizes the release and recovery of multiple sensors in series, greatly reduces the interference of the submarine on the sensors, realizes the gradient measurement of multiple sensors in series, and improves the accuracy of magnetic gradient measurement near the seabed.

Description

Near-sea bottom magnetic gradient measurement method

Technical field

The invention relates to the field of ocean magnetic measurement, in particular to a near-seabed magnetic gradient measurement method.

Background technique

Measuring the change rate of the magnetic field in space is called magnetic field gradient measurement. In actual production, there are two types of vertical gradient measurement and horizontal gradient measurement. Magnetic gradient measurement is generally carried out using multiple probes in series. Marine magnetic measurements mostly use ship-borne towed measurements. In order to reduce the interference of the ship's equipment on the magnetic equipment, the length of the towing cable is generally 3-6 times the length of the ship's length.

At present, near-seabed magnetic surveys mainly use two measurement methods: fixed-point and traveling. Among them, fixed-point measurements are mostly magnetic diurnal observation submersibles or landers, and traveling measurements are carried out by submarines. However, underwater traveling magnetic measurements are mostly fixedly installed on submersibles. For example, in the Qianlong series submersibles, the measurement probe is installed at the tail of the submersible. This method is closer to the submersible than the towed sensor, and the submersible interferes with the sensor greatly during measurement. Moreover, the existing underwater winch cannot realize the release and recovery of multiple sensors, making it impossible to realize the gradient measurement of multiple probes in series.

Contents of the invention

The purpose of the present invention is to overcome the above-mentioned defects of the existing technology, and propose a near-seabed magnetic gradient measurement method, which realizes the release and recovery of multiple sensors in series, greatly reduces the interference of the submarine on the sensors, and realizes Gradient measurement of multiple sensors in series improves the accuracy of magnetic gradient measurement near the seafloor.

The technical solution of the present invention is: a near-sea bottom magnetic gradient measurement method, which includes the following steps:

S1. Install the near-seabed magnetic gradient measurement device on the submarine:

The near-seabed magnetic gradient measurement device includes a frame, a hydraulic cable car and a sensor release mechanism. The hydraulic cable car and the sensor release mechanism are both arranged on the frame. The top of the frame is fixed to the submarine. The hydraulic cable car and the sensor release mechanism are connected by an oil cable. ;

The sensor release mechanism includes a limiter, a sensor release cabin, a sensor push-out hydraulic cylinder, and a release cabin lock. The sensor release cabin is cylindrical and is fixed on the frame. The front end of the sensor release cabin is the sensor release end, and the sensor release cabin There are several sensors arranged along the axial direction. The sensor close to the sensor release end is a first-level sensor, and the subsequent sensors are second-level sensors, third-level sensors...n-level sensors. There are at least two fixed intervals on the top surface of the sensor. Cable ring, the oil cable passes through the cable ring on the top of each sensor in turn, the end of the oil cable is fixed with a limit block, the size of the limit block is larger than the ring aperture of the cable ring;

The top surface of the sensor release cabin is provided with a strip hole along its axial direction, the cable ring is located in the strip hole, and the lower part of the cable ring slides in the strip hole, and the sensor release cabin is fixed at the top of the sensor. A sensor push-out hydraulic cylinder is fixed on the outer wall. The cylinder of the sensor push-out hydraulic cylinder is fixedly connected to the outside of the sensor release chamber. The piston rod of the sensor push-out hydraulic cylinder faces the n-level sensor. One end of the piston rod is connected to the cylinder of the sensor push-out hydraulic cylinder. A push rod is fixed at the other end, and the push rod is located on the back side of the cable ring fixed on the top of the n-level sensor.

There are n-1 limiters fixed on the oil cable. Each limiter corresponds to the second-level sensor to the n-level sensor respectively. The limiter includes a locking part, a lock pin and a limiter body. The main body of the limiter is cylindrical, and its two ends are respectively fixedly connected to the locking parts. There is a lock pin in the main body of the limiter;

The main body of the limiter includes a cylindrical fixed sleeve. Threaded joints are fixed at both axial ends of the fixed sleeve. At the same time, several threaded holes II are provided at intervals on both axial ends of the fixed sleeve. The size of the fixed sleeve is smaller than that of the through hole. The ring aperture of the cable ring;

There is a through hole in the center of the fixed sleeve, and both ends of the through hole are connected with threaded joints respectively. There are several lock pin through holes spaced along the radial direction in the fixed sleeve, and the lock pins are slidably arranged in the lock pin through holes. One end of the pin through hole is connected with the through hole, and the other end is connected with the opening of the annular outer wall of the fixed sleeve. When the end of the lock pin extends out of the lock pin through hole and is higher than the outer wall of the fixed sleeve, the lock pin with the extended lock pin The size of the fixing sleeve is larger than the diameter of the cable ring;

S2. Release the primary sensor:

Open the release cabin lock, push the sensor out of the hydraulic cylinder, and push the push rod to move the sensor toward the sensor release end of the sensor release cabin. When the first-level sensor is pushed out of the sensor release cabin, close the release cabin lock, and the sensor pushes out of the hydraulic cylinder and stops. Block other sensors in the cabin;

S3. Release the secondary sensor:

The primary sensor continuously descends under the action of gravity and falls to a position near the seabed for magnetic gradient measurement. While the primary sensor descends, it pulls the oil cable through the cable ring, so that the hydraulic winch is in a continuous cable-laying state. When interacting with the secondary sensor When the corresponding limiter moves between the two cable rings fixed on the top of the secondary sensor, the limiter works to increase the oil pressure in the limit. Under the push of the oil pressure, the limiter moves The lock pin extends out of the fixed sleeve to increase the outer size of the fixed sleeve. When the oil cable drives the stopper to move to contact with the cable ring fixedly connected to the secondary sensor, the stopper is pulled by the cable. The cable ring and the secondary sensor fixedly connected to it will be pushed toward the sensor release end until the secondary sensor is pushed out of the sensor release chamber;

S4. Repeat step S3 and release the subsequent sensors in sequence:

Under the gravity of several sensors in series, the hydraulic winch continues to release the cable. Subsequent sensors follow the oil cable through the corresponding limiter and leave the sensor release chamber, realizing the release of several series sensors on the seabed. The position of the sensors at each level on the oil cable is limited by the limiter, and the magnetic gradient measurement of each series sensor is realized.

In the present invention, the hydraulic cable car and the sensor release cabin are located at the front end of the frame, and the rear end of the frame is provided with two guide pulleys. The oil cables on the hydraulic cable car are connected to the sensor release cabin after passing through the two guide pulleys.

The sensor release end is in the shape of a trumpet, and the release cabin lock is in the shape of a rod, one end of which is connected to the hydraulic cylinder, and the other end extends into the sensor release cabin, thereby blocking the sensor in the sensor release cabin.

A push plate is fixed on the side of the lock pin facing the through hole, and the push plate is in direct contact with the hydraulic oil in the through hole. A spring is wound around the outside of the lock pin. One end of the spring is fixedly connected to the push plate. The lock pin is slidably arranged in the lock pin through hole. The size of the opening on the annular outer wall of the fixed sleeve is larger than the diameter of the lock pin and smaller than the diameter of the spring.

The locking portion at the axial end of the fixed sleeve is composed of two locking blocks. The locking block is provided with several threaded holes I, and the connecting threads pass through the threaded holes I and the threaded holes II at the end of the fixed sleeve in sequence to achieve a fixed connection between the locking part and the limiter body. The internal design of the locking block There are fixed grooves and oil cable passages. The fixed grooves are located outside the oil cable passages, and the fixed grooves are connected with the oil cable passages. After the two locking blocks are combined, the two fixing grooves are formed to match the locking ends of the standard hydraulic oil cables. The fixing hole, and the two oil cable through slots form the oil cable through hole.

The hydraulic winch includes a winch, a hydraulic motor, a catcher, and a slip ring. Winches are fixed at both ends of the rotating shaft of the hydraulic winch. The oil cable is wound around the rotating shaft. A hydraulic motor is provided on the support frame outside the winch on one side. The hydraulic motor is docked with the submersible. A slip ring is fixed on the support frame outside the winch on the other side. The oil cable hydraulic interface on the slip ring is docked with the submersible. There is also an electronic watertight connector on the slip ring. There is a slip ring in front of the winch. There is a catcher.

The beneficial effects of the present invention are:

(1) Each sensor is released to a position near the seabed through a hydraulic winch and oil cable. During the measurement process, the distance between each sensor and the submersible is relatively large, which greatly reduces the interference of the submersible to the sensor and improves the measurement of magnetic gradient near the seabed. precision;

(2) The serial release and recovery between multiple sensors are realized, and the gradient measurement of multiple sensors in series is realized;

(3) The oil in the oil cable can not only protect the oil cable from water, but also drive and control the limiter by controlling the pressure of the oil, thereby realizing the release of multiple series sensors.

Description of drawings

Figure 1 is a schematic three-dimensional structural diagram of the present invention;

Figure 2 is a schematic top view of the structure of the present invention;

Figure 3 is a schematic structural diagram of one end of the hydraulic winch;

Figure 4 is a schematic structural diagram of the other end of the hydraulic winch;

Figure 5 is a schematic three-dimensional structural diagram of the sensor release mechanism;

Figure 6 is a schematic structural diagram of the sensor release cabin;

Figure 7 is a schematic structural diagram of the sensor;

Figure 8 is a schematic structural diagram of the present invention;

Figure 9 is a schematic structural diagram of the limiter body;

Figure 10 is a schematic diagram of the internal structure of the limiter body;

Figure 11 is a schematic structural diagram of the lock pin;

Figure 12 is a schematic diagram of the installation structure of the locking block and the limiter body;

Figure 13 is a schematic top view of the locking block;

Figure 14 is a schematic bottom structural view of the locking block.

In the picture: 1 frame; 2 hydraulic winch; 201 winch; 202 hydraulic motor; 203 catcher; 204 slip ring; 205 oil cable hydraulic interface; 206 electronic watertight connector; 3 limiter; 301 locking part; 302 Fixed groove; 303 oil cable slot; 304 threaded hole I; 305 locking block; 306 lock pin; 307 limiter body; 308 fixed sleeve; 309 threaded hole II; 310 threaded joint; 311 through hole; 312 lock pin through hole; 313 spring; 314 push plate; 4 submersible docking pile; 5 hydraulic docking panel; 6 sensor release cabin; 7 sensor push-out hydraulic cylinder; 701 piston rod; 702 push rod; 8 release cabin lock; 9 guide pulley; 10 oil cable; 11 cable rings; 12 limit blocks; 13 strip holes; 14 sensors.

Detailed ways

In order to make the above objects, features and advantages of the present invention more obvious and understandable, specific implementation modes of the present invention will be described in detail below with reference to the accompanying drawings.

In the following description, specific details are set forth in order to provide a thorough understanding of the invention. However, the present invention can be implemented in many other ways than those described here, and those skilled in the art can make similar extensions without violating the connotation of the present invention. The present invention is therefore not limited to the specific embodiments disclosed below.

The near seabed magnetic gradient measurement method according to the present invention includes the following steps.

The first step is to install the near-seabed magnetic gradient measurement device on the submarine.

As shown in Figures 1 and 2, the near-seabed magnetic gradient measurement device includes a frame 1, a hydraulic cable car 2 and a sensor release mechanism. The hydraulic cable car 2 and the sensor release mechanism are both arranged on the frame 1. The top of the frame 1 is fixed with a submarine. The fixedly connected submersible docking pile 4 and the frame 1 are also fixed with a hydraulic docking panel 5. Through the hydraulic docking panel 45, the submarine can provide hydraulic power to the device. The hydraulic cable car 2 and the sensor release mechanism are connected through an oil cable 10.

As shown in Figures 3 and 4, the hydraulic winch 2 includes a winch 201, a hydraulic motor 202, an exhaust device 203, and a slip ring 204. The winch 201 is fixed at both ends of the rotating shaft of the hydraulic winch 2, and a support frame on the outside of the winch on one side. A hydraulic motor 202 is provided on the vehicle. The hydraulic pipe of the hydraulic motor 202 is connected to the hydraulic docking panel 5. The hydraulic motor 202 is docked with the submersible through the hydraulic docking panel 5, and the submersible provides power for the hydraulic motor. A slip ring 204 is fixed on the support frame outside the winch on the other side. The oil cable hydraulic interface 205 on the slip ring 204 is connected to the hydraulic docking panel 4 through a hydraulic pipe. The submarine provides hydraulic oil to the oil cable. At the same time, the oil cable hydraulic interface 205 on the slip ring 204 An electronic watertight connector 206 is also provided. The sensor is energized through the electronic watertight connector 206, the winch slip ring, and the oil cable to realize communication between the sensor and the submarine. This method can only achieve communication with the last level, that is, the Nth level. Real-time communication of sensors, other sensors can work by adding wireless communication components or self-capacitive data storage at specific locations in the oil cable. The front of the winch 201 is provided with a catcher 203. The catcher 203 is a device used to control the winding direction of the cable so that the cable can be wound better.

As shown in Figures 5 to 7, the sensor release mechanism includes a limiter 3, a sensor release cabin 6, a sensor push-out hydraulic cylinder 7, and a release cabin lock 8. The sensor release cabin 6 is cylindrical and is fixed on the frame 1 . In this embodiment, the hydraulic cable car 2 and the sensor release cabin 6 are located at the front end of the frame 1. The rear end of the frame 1 is provided with two guide pulleys 9. The oil cables on the hydraulic cable car pass through the two guide pulleys 9 and are released from the sensor. The cabin is connected, and the guide pulley 9 plays a guiding role.

The front end of the sensor release cabin 6 is a sensor release end, and the sensor release end is in the shape of a trumpet, which facilitates the release and recovery of the sensor. At the same time, there is a release cabin lock 8 at the sensor release end. The release cabin lock 8 is rod-shaped, one end of which is connected to the hydraulic cylinder, and the other end extends into the sensor release cabin 6, which blocks the sensor in the sensor release cabin 6.

The sensor release cabin 6 is provided with several sensors 14 arranged along the axial direction. The sensors close to the sensor release end are first-level sensors, and the subsequent sensors are second-level sensors, third-level sensors, and n-level sensors. As shown in Figure 7, at least two cable-passing rings 11 are fixed at intervals on the top surface of the sensor 14. The oil cable 10 passes through the cable-passing rings 11 on the top of each sensor in sequence. At the same time, the end of the oil cable 10 is fixed with a limiting block 12, limiting the The size of the bit block 12 is larger than the annular diameter of the cable ring 11 , thereby preventing the cable ring 11 from falling off the oil cable and ensuring that the cable ring 11 can always be placed on the oil cable 10 .

The top surface of the sensor release chamber 6 is provided with a bar-shaped hole 13 along its axial direction. The cable-passing rings 11 are located in the bar-shaped holes 13 , and the lower part of the cable-passing ring 11 can slide in the bar-shaped hole 13 . When the cable-passing ring 11 moves in the strip hole 13 , the sensor fixedly connected to the cable-passing ring 11 moves in the sensor release chamber 6 . A sensor push-out hydraulic cylinder 7 is fixed on the outer wall of the sensor release cabin 6. The cylinder of the sensor push-out hydraulic cylinder 7 is fixedly connected to the outside of the sensor release cabin 6. The piston rod 701 of the sensor push-out hydraulic cylinder 7 faces the n-level sensor. One end of the piston rod 701 is connected to the cylinder of the sensor push-out hydraulic cylinder, and the other end is fixed with a push rod 702. The push rod 702 is located on the rear side of the cable ring 11 fixed on the top of the n-level sensor. The rear side here refers to the sensor relative to the The direction of movement is the rear side. The sensor push-out hydraulic cylinder 7 is connected to the hydraulic docking panel 5 through a hydraulic pipe.

There are several limiters fixed on the oil cable. When there are n sensors in the sensor release cabin 6, n-1 limiters are provided on the corresponding oil cable. By setting the position of the limiter reasonably, each limiter is ensured. The positioner corresponds one-to-one with the second-level sensor to the n-level sensor respectively. As shown in Figures 8 to 14, the limiter 3 includes a locking part 301, a lock pin 306 and a limiter main body 307. The limiter main body 307 is cylindrical, and its two ends are fixedly connected to the locking part 301 respectively. A lock pin 306 is provided in the main body 307 of the positioner.

The limiter body 307 includes a cylindrical fixed sleeve 308. Threaded joints 310 are fixed at both axial ends of the fixed sleeve 308. Through the threaded joints 310, the connection between the limiter main body 307 and the oil cable 11 is realized. At the same time, the fixed sleeve 308 Several threaded holes II 309 are provided at intervals on both sides of the axial end, and the fixed connection between the fixed sleeve 308 and the locking block 305 is realized through the threaded holes II. The size of the fixing sleeve 308 is smaller than the ring hole diameter of the cable ring 11 .

There is a through hole in the center of the fixed sleeve 308, and both ends of the through hole are connected to the threaded joint 310 respectively. The hydraulic oil enters the through hole from the threaded joint at one end through the oil cable, flows to the threaded joint at the other end, and flows from the threaded joint to the threaded joint 310. The oil cable connected by the joint flows out. Several locking pin through holes 312 are provided in the fixed sleeve 308 at radial intervals, and the locking pins 306 are located in the locking pin through holes 312 . One end of the locking pin through hole 312 is connected to the through hole, and the other end is connected to the opening of the annular outer wall of the fixing sleeve. In this embodiment, two locking pin through holes 312 are provided in the fixed sleeve 308. The two locking pin through holes 312 are located on the same plane, and the two locking pin through holes 312 are arranged symmetrically.

A push plate 314 is fixed on the side of the lock pin 306 facing the through hole, and the push plate 314 is in direct contact with the hydraulic oil in the through hole. A spring 313 is wound around the outside of the lock pin 306, and one end of the spring 313 is fixedly connected to the push plate 314. The lock pin 306 is slidably disposed in the lock pin through hole 312 . At the same time, it is necessary to ensure that the size of the opening on the annular outer wall of the fixed sleeve 308 is larger than the diameter of the lock pin 306 and smaller than the diameter of the spring 313. When the limiter 3 is not working, the lock pin 306 is located in the lock pin through hole 312. Since the size of the fixing sleeve 308 is smaller than the annular diameter of the cable ring 11, the oil cable 11 can drive the limiter 3 at each position. Move between the cable rings 11. When the hydraulic oil in the through hole is pressurized, the hydraulic oil will push the push plate 314 to move radially outward, and the lock pin 306 and the spring 313 fixedly connected to the push plate 314 will also move outward. When the spring 313 moves When one end thereof comes into contact with the opening of the annular outer wall of the fixed sleeve, the spring 313 cannot continue to move outward, and the push plate 314 will push the lock pin 306 to continue to move outward, so that the end of the lock pin 306 extends out of the lock pin through hole 312 , and higher than the outer wall of the fixed sleeve 308. At this time, the size of the fixed sleeve with protruding lock pins on both sides is larger than the size of the cable ring 11. When the oil cable 10 drives the stopper 2 to move to the cable ring 11 , the stopper 3 can no longer pass through the cable ring, but can only push the cable ring 11 and the sensor connected to the cable ring to move together with the oil cable. The spring is in a compressed state under the thrust of push plate 313. When the oil pressure in the through hole decreases, under the elastic force of the spring 313, the lock pin 303 automatically resets and returns to the lock pin through hole 312 again.

The locking portions at the axial ends of the fixed sleeve 308 are composed of two locking blocks 305 . The locking block 305 is provided with several threaded holes I304, and the connecting threads pass through the threaded holes I304 and the threaded holes II309 at the end of the fixed sleeve in sequence, thereby achieving a fixed connection between the locking part 301 and the limiter body 307. The locking block 305 is provided with a fixing groove 302 and an oil cable passage groove 303 inside. The fixing groove 302 is located outside the oil cable passage groove 303, and the fixing groove 302 is connected with the oil cable passage groove 303. After the two locking blocks are combined, the two fixings 302 form a hexagonal fixing hole, which cooperates with the locking end of the standard hydraulic oil cable to prevent the oil cable from loosening; the two oil cable passage slots 303 form a cylindrical oil cable passage. hole for the oil cable to pass through. In addition, one end of the outer surface of the locking portion facing the stopper body is cylindrical, and the other end is truncated.

The second step is to release the primary sensor.

The release chamber lock is opened, the sensor is pushed out of the hydraulic cylinder 7, and the push rod 702 pushes the sensor to move toward the sensor release end of the sensor release chamber 6. When the first-level sensor is pushed out of the sensor release chamber 6, the release chamber lock 8 is closed, and the sensor Push out the hydraulic cylinder 7 to stop the action and block other sensors in the cabin.

The third step is to release the secondary sensor.

The first-level sensor continuously descends under the action of gravity and falls to a position near the seabed for magnetic gradient measurement. When the first-level sensor descends, it will pull the oil cable 10 through the cable ring 11, so that the hydraulic winch 2 is in a continuous cable-laying state. When the limiter 3 corresponding to the secondary sensor moves between the two cable rings 11 fixed on the top of the secondary sensor, the limiter 3 works to increase the oil pressure in the limiter 3. When the oil pressure increases, Under the push action, the lock pin 306 in the limiter 3 extends out of the fixed sleeve 308, so that the external size of the fixed sleeve 308 increases. As the cable car continues to unwind, the oil cable 10 drives the limiter 3 to move to the position of the two cables. When the cable ring 11 fixedly connected to the primary sensor comes into contact, the limiter 3, under the pulling action of the cable, will push the cable ring 11 and the secondary sensor fixedly connected to it toward the sensor release end until the sensor release chamber is pushed out. .

The fourth step is to repeat the action of step three and release the subsequent sensors in sequence.

Under the gravity of several sensors in series, the hydraulic winch 2 continues to release the cable, and the subsequent digital sensors 14 follow the oil cable 10 through the limiter 3 and leave the sensor release chamber 6, realizing the release of several series sensors 14 on the seabed. , the position of the sensors at each level on the oil cable is limited by the limiter 3, and the magnetic gradient measurement of each series sensor is realized.

When the sensors need to be recovered, the hydraulic cable car 2 collects them, and each sensor 14 can be pulled back to the sensor release cabin 6 through the oil cable 10 .

The near-seabed magnetic gradient measurement device provided by the present invention has been introduced in detail above. This article uses specific examples to illustrate the principles and implementation methods of the present invention. The description of the above embodiments is only used to help understand the method and the core idea of the present invention. It should be noted that those skilled in the art can make several improvements and modifications to the present invention without departing from the principles of the present invention, and these improvements and modifications also fall within the scope of the claims of the present invention. The above description of the disclosed embodiments enables those skilled in the art to make or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be practiced in other embodiments without departing from the spirit or scope of the invention. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims (6)

1. A near-sea bottom magnetic gradient measurement method, characterized in that it includes the following steps: S1. Install the near-seabed magnetic gradient measurement device on the submarine: The near-seabed magnetic gradient measurement device includes a frame, a hydraulic cable car and a sensor release mechanism. The hydraulic cable car and the sensor release mechanism are both arranged on the frame. The top of the frame is fixed to the submarine. The hydraulic cable car and the sensor release mechanism are connected by an oil cable. ; The sensor release mechanism includes a limiter, a sensor release cabin, a sensor push-out hydraulic cylinder, and a release cabin lock. The sensor release cabin is cylindrical and is fixed on the frame. The front end of the sensor release cabin is the sensor release end, and the sensor release cabin There are several sensors arranged along the axial direction. The sensor close to the sensor release end is a first-level sensor, and the subsequent sensors are second-level sensors, third-level sensors...n-level sensors. There are at least two fixed intervals on the top surface of the sensor. Cable ring, the oil cable passes through the cable ring on the top of each sensor in turn, the end of the oil cable is fixed with a limit block, the size of the limit block is larger than the ring aperture of the cable ring; The top surface of the sensor release cabin is provided with a strip hole along its axial direction, the cable ring is located in the strip hole, and the lower part of the cable ring slides in the strip hole, and the sensor release cabin is fixed at the top of the sensor. A sensor push-out hydraulic cylinder is fixed on the outer wall. The cylinder of the sensor push-out hydraulic cylinder is fixedly connected to the outside of the sensor release chamber. The piston rod of the sensor push-out hydraulic cylinder faces the n-level sensor. One end of the piston rod is connected to the cylinder of the sensor push-out hydraulic cylinder. A push rod is fixed at the other end, and the push rod is located on the back side of the cable ring fixed on the top of the n-level sensor. There are n-1 limiters fixed on the oil cable. Each limiter corresponds to the second-level sensor to the n-level sensor respectively. The limiter includes a locking part, a lock pin and a limiter body. The main body of the limiter is cylindrical, and its two ends are respectively fixedly connected to the locking parts. There is a lock pin in the main body of the limiter; The main body of the limiter includes a cylindrical fixed sleeve. Threaded joints are fixed at both axial ends of the fixed sleeve. At the same time, several threaded holes II are provided at intervals on both axial ends of the fixed sleeve. The size of the fixed sleeve is smaller than that of the through hole. The ring aperture of the cable ring; There is a through hole in the center of the fixed sleeve, and both ends of the through hole are connected with threaded joints respectively. There are several lock pin through holes spaced along the radial direction in the fixed sleeve, and the lock pins are slidably arranged in the lock pin through holes. One end of the pin through hole is connected with the through hole, and the other end is connected with the opening of the annular outer wall of the fixed sleeve. When the end of the lock pin extends out of the lock pin through hole and is higher than the outer wall of the fixed sleeve, the lock pin with the extended lock pin The size of the fixing sleeve is larger than the diameter of the cable ring; S2. Release the primary sensor: Open the release cabin lock, push the sensor out of the hydraulic cylinder, and push the push rod to move the sensor toward the sensor release end of the sensor release cabin. When the first-level sensor is pushed out of the sensor release cabin, close the release cabin lock, and the sensor pushes out of the hydraulic cylinder and stops. Block other sensors in the cabin; S3. Release the secondary sensor: The primary sensor continuously descends under the action of gravity and falls to a position near the seabed for magnetic gradient measurement. While the primary sensor descends, it pulls the oil cable through the cable ring, so that the hydraulic winch is in a continuous cable-laying state. When interacting with the secondary sensor When the corresponding limiter moves between the two cable rings fixed on the top of the secondary sensor, the limiter works to increase the oil pressure in the limit. Under the push of the oil pressure, the limiter moves The lock pin extends out of the fixed sleeve to increase the outer size of the fixed sleeve. When the oil cable drives the stopper to move to contact with the cable ring fixedly connected to the secondary sensor, the stopper is pulled by the cable. The cable ring and the secondary sensor fixedly connected to it will be pushed toward the sensor release end until the secondary sensor is pushed out of the sensor release chamber; S4. Repeat step S3 and release the subsequent sensors in sequence: Under the gravity of several sensors in series, the hydraulic winch continues to release the cable. Subsequent sensors follow the oil cable through the corresponding limiter and leave the sensor release chamber, realizing the release of several series sensors on the seabed. The position of the sensors at each level on the oil cable is limited by the limiter, and the magnetic gradient measurement of each series sensor is realized. 2. The near-seabed magnetic gradient measurement method according to claim 1, characterized in that the hydraulic cable car and the sensor release cabin are located at the front end of the frame, the rear end of the frame is provided with two guide pulleys, and the oil on the hydraulic cable car is The cables are connected to the sensor release cabin after passing through two guide pulleys. 3. The near-seabed magnetic gradient measurement method according to claim 1, characterized in that the sensor release end is in the shape of a trumpet, and the release cabin lock is in the shape of a rod, one end of which is connected to the hydraulic cylinder, and the other end extends into the sensor release cabin. inside, blocking the sensors in the sensor release cabin. 4. The near-seabed magnetic gradient measurement method according to claim 1, characterized in that a push plate is fixed on the side of the lock pin facing the through hole, and the push plate is in direct contact with the hydraulic oil in the through hole. A spring is wound around the outside of the lock pin. One end of the spring is fixedly connected to the push plate. The lock pin is slidably arranged in the lock pin through hole. The size of the opening on the annular outer wall of the fixed sleeve is larger than the diameter of the lock pin and smaller than the diameter of the spring. 5. The near-seabed magnetic gradient measurement method according to claim 1, characterized in that the locking portions at the axial end of the fixed sleeve are composed of two locking blocks. The locking block is provided with several threaded holes I, and the connecting threads pass through the threaded holes I and the threaded holes II at the end of the fixed sleeve in sequence to achieve a fixed connection between the locking part and the limiter body. The internal design of the locking block There are fixed grooves and oil cable passages. The fixed grooves are located outside the oil cable passages, and the fixed grooves are connected with the oil cable passages. After the two locking blocks are combined, the two fixing grooves are formed to match the locking ends of the standard hydraulic oil cables. The fixing hole, and the two oil cable through slots form the oil cable through hole. 6. The near-seabed magnetic gradient measurement method according to claim 1, characterized in that the hydraulic winch includes a winch, a hydraulic motor, an exhaust device, and a slip ring, and winches are respectively fixed at both ends of the rotating shaft of the hydraulic winch. The cable is wound around the rotating shaft. A hydraulic motor is installed on the support frame outside the winch on one side. The hydraulic motor is connected to the submarine. A slip ring is fixed on the support frame outside the winch on the other side. The oil cable hydraulic interface on the slip ring is connected to the support frame on the other side of the winch. When the submersible is docked, the slip ring is also equipped with an electronic watertight connector, and there is a catcher in front of the winch.