A non-contact attitude measuring device and measuring method for a towed ship model

Abstract

This invention discloses a non-contact attitude measurement device and method for towed model boats. The device includes a towing frame mounted above the test model, a towing bracket mounted on the towing frame, and the test model clamped at the lower end of the towing bracket. A laser trigger is mounted on the side wall of the test pool. Laser rangefinders are mounted on the bow and stern of the test model, and a light shield is mounted on the towing frame. A navigation board and an inclination sensor are mounted on the test model. The laser rangefinder is fixed on a rotating shaft and connected to a servo motor. The servo motor, inclination sensor, and laser trigger are respectively connected to a controller. When the test model passes the laser trigger, the trigger signal is transmitted to the controller via first and second wireless communication modules. The controller, combined with the inclination data of the test model collected by the inclination sensor, adjusts the angle of the laser rangefinder by rotating the servo motor. This solution can calculate the heave and sag of the model based on the change in distance measured by the laser rangefinder, and the measurement is convenient, accurate, reliable, and highly automated.

Description

Technical Field

[0001] This invention relates to ship model testing technology, specifically to a non-contact attitude measurement device and method for towing ship models. Background Technology

[0002] Towing tests of ship models in a towing tank are a routine method in the field of ship testing technology for studying ship navigation performance. Currently, the main equipment used to measure the navigation attitude of ship models in a towing tank includes: one is a dedicated four-degree-of-freedom (DOF) seaworthiness instrument. Because its towing method differs from traditional trailers, it is only suitable for high-speed ships with significant changes in navigation attitude. Besides being expensive, adding this equipment to existing trailers requires consideration of space capacity and electrical layout; another is a non-contact six-degree-of-freedom measurement system, whose receiving equipment is inconvenient to install, sensitive to vibration, and too expensive; and a traditional rod-type displacement sensor. Its large weight constrains the heave motion of the ship model and cannot overcome the problem that the measuring point moves along an arc in space during the free-mode motion of the ship model. During the uniform motion phase of the ship model, the measuring rod and sleeve are not on the same vertical line, thus making accurate measurement impossible.

[0003] A search revealed that prior art, CN106184614A, discloses a device and method for measuring the resistance and attitude of a ship model, and a method for measuring the heave and pitch angle of a ship model using a wire-type device with a potentiometer. However, this method has the following problems: (1) One end of the wire needs to be fixed to the model, and the other end is on the towing frame, which is essentially a contact method and will affect the sailing attitude of the ship model. (2) The wire-type method is a method for measuring the distance between the fixed point of the ship model and the fixed point of the towing frame, and the longitudinal position of the ship model relative to the towing frame will change in the initial state and the free mode uniform motion state. This causes the method to have the same limitation as the traditional rod displacement sensor, that is, the spatial position before and after the measuring point is not on the same vertical line, and the method does not compensate for this angle, resulting in systematic error.

[0004] Therefore, there is an urgent need for a towed boat model attitude measurement system that is easy to deploy, accurate and reliable, convenient to measure, economical and practical, and highly automated. Summary of the Invention

[0005] Purpose of the invention: The first purpose of the invention is to provide a non-contact attitude measurement device for towed boat models that is easy to deploy, accurate and reliable, convenient to measure, and economical; the second purpose of the invention is to provide a non-contact attitude measurement method for towed boat models that can measure the heave data of the model.

[0006] Technical Solution: The present invention provides a non-contact attitude measurement device for towed ship models, comprising a towing frame mounted above the test model, a towing bracket mounted on the towing frame, and a clamping device at the lower end of the towing bracket to clamp the test model; the test model floats upright on a test pool, and a laser trigger is mounted on the side wall of the test pool; a navigation board and an inclination sensor are mounted on the test model; a laser rangefinder is mounted on the bow and stern decks of the test model, and a light shield corresponding to the laser rangefinder is mounted on the towing frame; the laser rangefinder is fixed on a rotating shaft and connected to a servo motor; the servo motor, inclination sensor, and laser trigger are respectively connected to a controller; the laser trigger is connected to a first wireless communication module, and the controller is connected to a second wireless communication module; when the test model passes the laser trigger, the trigger signal is transmitted to the controller through the first and second wireless communication modules, and the controller, in conjunction with the inclination data of the test model collected by the inclination sensor, adjusts the deflection angle of the laser rangefinder by controlling the rotation of the servo motor.

[0007] The laser trigger is pre-set in the uniform steady-state motion segment of the test model. It automatically triggers the attitude measurement system when the test model reaches the set uniform motion condition, obtaining data and overcoming the coordination difficulties between trailer movement, test model motion judgment, and sensor data reading. For situations with limited towing pool length or high speed requirements for the test model, as long as a short segment of uniform steady-state motion exists, its attitude can be measured using this system and method.

[0008] The light-shielding plate is fixed to the towing frame by a truss, and the light-shielding plate remains horizontal; when the test model moves, the measuring point of the laser rangefinder always falls on the light-shielding plate.

[0009] A steel wire is also provided between the towing frame and the test model. One end of the steel wire is connected to the towing frame, and the other end passes around the fixed pulley and connects to the test model. The steel wire can provide a constant forward traction force during the uniform steady-state motion of the test model. The fixed pulley can be adjusted vertically through a screw lifting mechanism, so that the steel wire remains horizontal during the uniform steady-state motion of the test model.

[0010] The present invention also includes a non-contact attitude determination method for towed model boats, the method comprising the following steps:

[0011] Step 1: The dragging bracket moves the test model, the clamping device opens, and the test model enters the uniform steady-state motion stage in the free mode. The laser trigger is placed at a position in this motion stage, and the height of the fixed pulley is repeatedly adjusted so that the dragging steel wire can drag the test model horizontally in this motion stage.

[0012] Step Two: At the initial moment when the test model is upright and clamped, adjust the servo motor angle via the controller to keep the laser rangefinder's ranging laser perpendicular. Then, read the laser rangefinder data from the bow and stern of the test model via the controller, which will be z... 11 z 21 The horizontal distances from the station position in the test model to the two laser rangefinders were measured as x1 and x2 respectively, and the current position of the tilt sensor was set as the zero point.

[0013] Step 3: Repeat the operation in Step 1 to drag the test model. The test model obtains a constant directional traction force through the pre-adjusted horizontal steel wire rope and enters uniform motion in free mode.

[0014] Step 4: The test model passes the laser trigger at a constant speed. The laser trigger transmits the trigger signal to the controller through the first wireless communication module and the second wireless communication module. The controller sends a command to the tilt sensor to read the angle, and uses this angle θ as the pitch angle of the test model. The controller encodes the angle signal into a PWM signal and outputs it to the servo motor through its built-in general-purpose timer module, so that the servo motor rotates in the opposite direction by an angle θ, so that the laser rangefinder returns to the vertical state.

[0015] Step 5: The controller reads the data from the laser rangefinder after it has returned to a vertical position. The distances measured at the bow and stern of the test model are z and z, respectively. 12 z 22 ,

[0016] Step 6: Based on the data measured by the laser rangefinder and the pitch angle θ measured by the tilt sensor, calculate the overall heave value δ0, the bow heave value δ1, and the stern heave value δ2 of the test model.

[0017] In step six, the formula for calculating the overall heave value δ0 of the experimental model is:

[0018] δ0=z 11 -z 12 -x1tanθ

[0019] or

[0020] δ0=z 21 -z 22 +x2tanθ

[0021] Among them, z 11 z 21 These are the distance values ​​recorded by the bow and stern laser rangefinders at the initial moment, respectively; z 12 z 22 x1 and x2 are the distance values ​​recorded by the laser rangefinders at the bow and stern during uniform steady-state motion, respectively; x1 and x2 are the horizontal distances from the midship station position to the laser rangefinder positions at the bow and stern, respectively.

[0022] In step six, the formula for calculating the bow heave value δ1 of the experimental model is as follows:

[0023]

[0024] Where δ0 represents the overall heave; L represents the horizontal distance from the bow to the stern; and θ represents the pitch angle of the test model.

[0025] In step six, the formula for calculating the stern heave value δ2 of the experimental model is:

[0026]

[0027] Where δ0 represents the overall heave; L represents the horizontal distance from the bow to the stern; and θ is the pitch angle of the test model.

[0028] Beneficial effects: Compared with the prior art, the technical solution of the present invention has the following beneficial effects: (1) It can measure the attitude parameters of the ship model in the free mode of open heave, sway, and pitch, and is easy to arrange, accurate and reliable, convenient to measure, economical and applicable, and highly automated. It is used to measure the pitch and heave of the free mode ship model; (2) It can automatically trigger the attitude measurement system when the test model reaches the uniform motion set in the working condition to obtain data, overcoming the coordination problem between the movement of the trailer, the judgment of the motion of the test model, and the reading of sensor data; (3) For situations such as tight towing pool length and large speed working condition required by the test model, as long as there is a small segment of uniform steady-state motion, its attitude can be measured by this system and method. Attached Figure Description

[0029] Figure 1 This is a schematic diagram of the measuring device of the present invention;

[0030] Figure 2 This is a schematic diagram of the laser rangefinder and its angle compensation component of the present invention.

[0031] Figure 3 This is a schematic diagram of the fixed pulley and steel wire of the present invention;

[0032] Figure 4 This is a flowchart illustrating the information transmission logic of the present invention.

[0033] Figure 5 This is a schematic diagram of the attitude calculation of the present invention;

[0034] Figure 6 This is a schematic diagram illustrating the principle of attitude calculation after translation in this invention. Detailed Implementation

[0035] The technical solution of the present invention will now be described in detail with reference to specific embodiments and accompanying drawings.

[0036] like Figure 1 , Figure 2 , Figure 3 As shown, the non-contact attitude measurement device for towing a model boat of the present invention includes the following components: a laser trigger 2, a towing frame 4, a towing bracket 5, a clamping device 6, a fixed pulley 7, a navigation plate 8, a navigation rod 9, a truss 10, a light shield 11, a laser rangefinder 12, an tilt sensor 13, a servo motor 14, a rotating shaft 15, a controller 16, and a towing steel wire 17. The towing frame 4 is located above the test model 3. The towing bracket 5 is installed on the towing frame 4. The lower end of the towing frame 4 clamps the test model 3 through the clamping device 6. An air valve is installed on the clamping device 6, and the opening and closing of the clamping device 6 is controlled by the air valve. A towing steel wire 17 is also provided between the towing frame 4 and the test model 3. One end of the towing steel wire 17 is connected to the test model 3, and the other end passes around the fixed pulley 7 and is connected to the towing frame 4. Two additional navigation rods 9 are arranged on the longitudinal section of the towing frame 4, with their lower ends passing through the slot in the middle of the navigation plate 8 to control the degrees of freedom of motion of the test model. The navigation plate 8 is horizontally installed on the deck of the test model 3. The clamping device 6 clamps the test model 3 when it is floating on the test water tank 1. When the towing frame 4 enters a constant speed, the airlock control clamp on the clamping device 6 opens, releasing the test model 3. The towing force is provided by the towing steel wire 17 connected between the towing frame 4 and the test model 3.

[0037] The test model 3 floats on the test water tank 1. A laser trigger 2 is installed on the side wall of the test water tank 1. When the test model 3 moves to the front of the test model 3, the laser trigger 2 is triggered. In this scheme, the laser trigger 2 is located in the uniform steady-state motion segment of the test model 3. It can automatically trigger the attitude measurement system to obtain data when the test model reaches the uniform motion set in the working condition, thus overcoming the coordination problem between trailer movement, test model motion judgment, and sensor data reading. For situations where the towing water tank length is limited and the test model requires a high speed, this scheme only requires a short segment of uniform steady-state motion to determine its attitude through this system and method. A laser rangefinder 12 is installed on the bow and stern decks of the test model 3, respectively. A light shield 11 is installed on the towing frame 4 at the corresponding position of the laser rangefinder 12. The laser rangefinder 12 sends a laser to the light shield 11 to measure the distance between itself and the light shield 11. The specific installation method of the light-shielding plate 11 is as follows: the light-shielding plate 11 is fixed to the towing frame 4 by the truss 10, and the light-shielding plate 11 is adjusted with a level to keep it horizontal; when the test model 3 moves, the measuring point of the laser rangefinder 12 always falls on the light-shielding plate 11. The laser rangefinder 12 can be installed at any position at the bow and stern of the test model 3, which can avoid the situation where the deck space at the bow and stern of the test model is limited. An inclination sensor 13 is also installed in the middle of the deck of the test model 3 to measure the inclination angle caused by hydrodynamics when the test model 3 moves.

[0038] like Figure 3 As shown, a towing steel wire 17 is also provided between the towing frame 4 and the test model 3. One end of the towing steel wire 17 is connected to the towing frame 4, and the other end passes around the fixed pulley 7 and connects to the test model 3. The towing steel wire 17 can provide a constant forward traction force during the uniform steady-state motion segment of the test model 3 in free mode after the clamping device 6 is released. The fixed pulley 7 can be adjusted in vertical height through the screw lifting mechanism, so that the towing steel wire 17 can remain horizontal during the uniform steady-state motion segment of the test model 3.

[0039] like Figure 2 and Figure 4As shown, the laser rangefinder 12 is connected to the servo motor 14 via a rotating shaft 15, allowing it to rotate and ensuring that the midpoint of the shaft coincides with the starting point of the ranging laser. In principle, the servo motor 14 and the controller 16 do not need to be adjacent, but in this design, for ease of equipment arrangement, the servo motor 14 and the controller 16 are integrated together via a connector. The tilt sensor 13, servo motor 14, laser trigger 2, and second wireless communication module are respectively connected to the controller 16, and the laser trigger 2 is connected to the first wireless communication module. Specifically, the tilt sensor 13 is connected to the controller 16 via the CAN bus communication protocol, and the controller 16 outputs a PWM signal through its built-in general-purpose timer module, which is connected to the servo motor via a PWM signal line. In this design, the controller 16 can specifically be an STM32 embedded microcontroller, and the first and second wireless communication modules can specifically be wireless access points (APs). When the test model 3 passes the laser trigger 2, the laser trigger 2 is triggered and returns a trigger signal to the WiFi module of the STM32 through the two wireless APs. The controller 16 combines the tilt angle data of the test model 3 collected by the tilt sensor 13 and adjusts the angle of the laser rangefinder 12 by controlling the rotation of the servo motor 14.

[0040] The present invention also includes a non-contact attitude determination method for towed model boats, comprising the following steps:

[0041] Step 1: The dragging bracket 5 moves the test model 3, the clamping device 6 opens, and the test model 3 enters the uniform steady-state motion stage in the free mode. The laser trigger 2 is placed at a position in this motion stage, and the height of the fixed pulley 7 is repeatedly adjusted so that the dragging steel wire 17 can drag the test model 3 horizontally in this motion stage; the details are as follows:

[0042] The test model 3 floats on the test pool 1 and is clamped by the towing support 5. The towing frame 4 drives the support 5 and the clamped test model 3 to move. After the towing frame 4 enters the set uniform motion, the clamping device 6 opens. At this time, the test model 3 is only provided with towing force by the towing steel wire 17 passing around the fixed pulley 7. The navigation plate 8 and the navigation rod 9 constrain the three degrees of freedom of the test model 3: yaw, sway, and roll, realizing the free modal motion of the towed boat model with open pitch, sway, and heave. Then the attitude of the test model 3 changes and proceeds... Entering its uniform steady-state motion phase; the laser trigger 2 is placed at a position during the uniform steady-state motion phase of the test model 3; during this phase, the attitude of the test model 3 will change, causing one end of the steel wire dragging the test model 3 to deviate from the horizontal direction, at which time the traction force provided by the dragging steel wire 17 deviates from the bow direction; after the dragging frame 4 returns to the starting point, the height of the fixed pulley 7 is adjusted, and the above operation is repeated so that the lower end of the dragging steel wire 17 can remain horizontal during the uniform motion phase of the free mode of the test model 3, providing a horizontal bow traction force;

[0043] Step Two: At the initial moment when the test model 3 is floating upright and clamped by the clamping device 6, the angle of the servo motor 14 is adjusted by the controller 16 to keep the ranging laser of the laser rangefinder 12 perpendicular; the controller 16 reads the data from the laser rangefinder 12 at the bow and stern of the test model 3, which are respectively z 11 z 21 ; Measure the horizontal distances x1 and x2 from the station position in test model 3 to the station positions of the two laser rangefinders 12 respectively; Set the current position of the tilt sensor 13 as the zero point;

[0044] Step 3: Repeat the operation in Step 1 to drag the test model 3. The test model 3 obtains a constant directional traction force only by dragging the steel wire 17 whose position has been adjusted in advance, and enters uniform motion in free mode.

[0045] Step 4: The test model 3 passes the laser trigger 2 at a constant speed. The laser trigger 2 transmits the trigger signal to the controller 16 through the first wireless communication module and the second wireless communication module. The controller 16 sends a command to the tilt sensor 13 to read the angle, and uses this angle θ as the pitch angle of the test model 3. The controller 16 encodes the angle signal into a PWM signal and outputs it to the servo motor 14 through its built-in general-purpose timer module, so that the servo motor 14 rotates in the opposite direction by an angle θ, so that the laser rangefinder 12 returns to the vertical state.

[0046] Step 5: Controller 16 reads the data from laser rangefinder 12 after a delay, once the rangefinder has returned to a vertical position. The distances measured at the bow and stern of test model 3 are z and z, respectively. 12 z 22 ,

[0047] Step 6: Based on the data measured by the laser rangefinder 12 and the pitch angle θ measured by the tilt sensor 13, calculate the overall heave value δ0, the bow heave value δ1, and the stern heave value δ2 of the test model 3.

[0048] like Figure 5 As shown, P represents the initial position of the bow laser rangefinder; P' represents the position of the bow laser rangefinder at its steady-state state; Q represents the initial position of the stern laser rangefinder; Q' represents the position of the stern laser rangefinder at its steady-state state; M represents the initial position of the mid-station; M' represents the position of the mid-station at its steady-state state; PQ represents the initial position of experimental model 3, and P'Q' represents the position of experimental model 3 at its steady-state state. For ease of explanation, P'Q' is moved horizontally a certain distance to align the points vertically, as shown... Figure 6 As shown. At this point, the overall heave value δ0 of experimental model 3, i.e., MM' in the figure, can be easily calculated using the following formula:

[0049] δ0=z 11 -z 12 -x1tanθ

[0050] or

[0051] δ0=z 21 -z 22 +x2tanθ

[0052] Among them, z 11 z 21 These are the distance values ​​recorded by the bow and stern laser rangefinders at the initial moment, respectively; z 12 z 22 x1 and x2 are the distance values ​​recorded by the laser rangefinders at the bow and stern during uniform steady-state motion, respectively; x1 and x2 are the horizontal distances from the midship station position to the laser rangefinder positions at the bow and stern, respectively.

[0053] The formula for calculating the bow heave δ1 of test model 3 is as follows:

[0054]

[0055] Where δ0 represents the overall heave; L represents the horizontal distance from the bow to the stern; and θ is the pitch angle of the test model (sign is retained).

[0056] The formula for calculating the stern heave value δ2 of test model 3 is as follows:

[0057]

[0058] Where δ0 represents the overall heave; L represents the horizontal distance from the bow to the stern; and θ is the pitch angle of the test model (sign is retained).

Claims

1. A non-contact attitude measurement device for towed model boats, characterized in that: The test model (3) is equipped with a towing frame (4) mounted on top of the test model (3), a towing bracket (5) is mounted on the towing frame (4), and a clamping device (6) is located at the lower end of the towing bracket (5) to clamp the test model (3). The test model (3) floats upright on the test pool (1), and a laser trigger (2) is mounted on the side wall of the test pool (1). A navigation board (8) and an tilt sensor (13) are mounted on the test model (3). A laser rangefinder (12) is mounted on the bow and stern decks of the test model (3), and a light shield (11) corresponding to the laser rangefinder (12) is mounted on the towing frame (4). The laser rangefinder (12) is fixed on the rotating shaft (15) and connected to the servo motor (14). The servo motor (14), the tilt sensor (13), and the laser trigger (2) are connected to the controller (16). The laser trigger (2) is connected to the first wireless communication module, and the controller (16) is connected to the second wireless communication module. When the test model (3) passes the laser trigger (2), the trigger signal is transmitted to the controller (16) through the first wireless communication module and the second wireless communication module. The controller (16) combines the tilt angle data of the test model (3) collected by the tilt sensor (13) and adjusts the deflection angle of the laser rangefinder (12) by controlling the rotation of the servo motor (14).

2. The non-contact attitude measuring device for towed model boats according to claim 1, characterized in that: The laser trigger (2) is pre-set in the uniform steady-state motion segment of the test model (3).

3. The non-contact attitude measuring device for towed model boats according to claim 1, characterized in that: The light-shielding plate (11) is fixed to the towing frame (4) by the truss (10), and the light-shielding plate (11) remains horizontal; when the test model (3) moves, the measuring point of the laser rangefinder (12) always falls on the light-shielding plate (11).

4. The non-contact attitude measuring device for towed model boats according to claim 1, characterized in that: A towing wire (17) is also provided between the towing frame (4) and the test model (3). One end of the towing wire (17) is connected to the towing frame (4), and the other end passes around the fixed pulley (7) and is connected to the test model (3).

5. A non-contact attitude measurement method for towed model boats, characterized in that, The method applied to the non-contact attitude measurement device for towing a model boat as described in claim 1 includes the following steps: Step 1: The dragging bracket (5) drags the test model (3) to move, the clamping device (6) is opened, and the test model (3) enters the uniform steady-state motion stage in the free mode. The laser trigger (2) is placed in this motion stage, and the height of the fixed pulley (7) is repeatedly adjusted so that the dragging steel wire (17) drags the test model (3) horizontally in this motion stage. Step 2: At the initial moment when the test model (3) is floating upright and clamped, the angle of the servo motor (14) is adjusted by the controller (16) to keep the ranging laser of the laser rangefinder (12) vertical. The controller (16) reads the data from the laser rangefinder (12) at the bow and stern of the test model (3) respectively. 11 z 21 The horizontal distances from the station position in the test model (3) to the two laser rangefinders (12) are measured as x1 and x2 respectively, and the current position of the tilt sensor (13) is set as zero. Step 3: Repeat the operation in Step 1 to drag the test model (3). The test model (3) obtains a constant directional traction force through the pre-adjusted drag wire (17) and enters uniform motion in free mode. Step 4: The test model (3) passes through the laser trigger (2) at a constant speed. The laser trigger (2) transmits the trigger signal to the controller (16) through the first wireless communication module and the second wireless communication module. The controller (16) sends a command to the tilt sensor (13) to read the angle and uses this angle θ as the pitch angle of the test model (3). The controller (16) encodes the angle signal into a PWM signal and outputs it to the servo motor (14) through its built-in general-purpose timer module, so that the servo motor (14) rotates in the opposite direction by an angle θ, so that the laser rangefinder (12) returns to the vertical state. Step 5: The controller (16) reads the data after the laser rangefinder (12) returns to a vertical state. The distances measured at the bow and stern of the test model (3) are z respectively. 12 z 22 ; Step 6: Based on the data measured by the laser rangefinder (12) and the pitch angle θ measured by the tilt sensor (13), calculate the overall heave value δ0, the bow heave value δ1, and the stern heave value δ2 of the test model (3).

6. The non-contact attitude determination method for towed model boats according to claim 5, characterized in that, In step six, the formula for calculating the overall heave value δ0 of the experimental model (3) is as follows: δ0=z 11 -With 12 -x1tanθ or δ0=z 21 -With 22 +x2tanθ Among them, z 11 z 21 These are the distance values ​​recorded by the bow and stern laser rangefinders at the initial moment, respectively; z 12 z 22 x1 and x2 are the distance values ​​recorded by the laser rangefinders at the bow and stern during uniform steady-state motion, respectively; x1 and x2 are the horizontal distances from the midship station position to the laser rangefinder positions at the bow and stern, respectively.

7. The non-contact attitude determination method for towed model boats according to claim 5, characterized in that, In step six, the formula for calculating the bow heave value δ1 of the experimental model (3) is as follows: Where δ0 represents the overall heave; L represents the horizontal distance from the bow to the stern; and θ represents the pitch angle of the test model.

8. The non-contact attitude determination method for towed boat models according to claim 5, characterized in that, In step six, the formula for calculating the stern heave value δ2 of the experimental model (3) is as follows: Where δ0 represents the overall heave; L represents the horizontal distance from the bow to the stern; and θ is the pitch angle of the test model.

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