A ship propulsion shafting coaxiality measurement system and method based on two-dimensional displacement measurement

Abstract

The application belongs to the technical field of coaxiality measurement, and discloses a ship propulsion shafting coaxiality measurement system and method based on two-dimensional displacement measurement. Two laser displacement sensors for measuring horizontal displacement and vertical displacement respectively are arranged at the front end and the rear end, two-dimensional displacement information of the cross sections of the measured shaft at both ends is synchronously collected, the position parameters of the sensors relative to the installation reference and the geometric size of the cross section of the measured shaft are combined, the center coordinates of the front and rear cross sections are calculated, and the actual center axis of the measured shaft is determined by the two centers; the coaxiality error is calculated by the position offset and the direction deflection between the actual center axis and the theoretical reference axis. Compared with the existing detection method which needs to obtain measurement information by rotating the shaft, the application can realize coaxiality parameter measurement in a static state without driving the measured shaft to rotate, has the advantages of simple structure, convenient operation, high measurement efficiency and suitability for on-site rapid detection, and can be applied to static centering detection of ship shafting and other long shaft components.

Description

Technical Field

[0001] This invention relates to the field of coaxiality measurement technology, specifically to a system and method for measuring the coaxiality of a ship propulsion shafting based on two-dimensional displacement measurement. Background Technology

[0002] The propulsion shafting system is a critical component of a ship's propulsion system, and its operational status directly affects the ship's propulsion efficiency, operational stability, and service reliability. For submarines and other vessels with high requirements for vibration and noise control, the assembly accuracy and alignment of the shafting system are particularly important. Misalignment or skewness in the shafting system can easily lead to increased bearing loads, abnormal coupling stress, and increased vibration and noise. In severe cases, it can even cause abnormal wear, reduced equipment lifespan, or operational failure. Current shafting alignment operations typically include parameter measurement, adjustment plan development, and on-site implementation, with parameter measurement being the foundation of shafting alignment. In engineering, four components—vertical offset, horizontal offset, vertical angle, and horizontal angle—are generally used to characterize the shafting alignment status and determine whether the shafting installation accuracy meets the requirements.

[0003] To address the problem of measuring shaft alignment parameters, various detection methods have been proposed in existing technologies. Based on the measurement principle, these can be broadly categorized into two types: indirect measurement methods and direct measurement methods. Indirect measurement methods typically reflect shaft misalignment indirectly through temperature, vibration, acoustic emission, or other operating status signals. These methods generally rely on offline analysis or large-scale data processing, resulting in poor real-time performance and high requirements for operating conditions and data processing capabilities. Direct measurement methods typically employ laser displacement sensors, displacement sensors, or other non-contact measuring elements to directly acquire shaft position parameters. They offer advantages such as fast response speed, high measurement accuracy, and suitability for engineering applications, making them more valuable in engineering practice.

[0004] However, existing direct measurement methods still have the following shortcomings when applied to static alignment inspection of ship shafting: First, some methods can only obtain deviation information of a single measuring point or a single cross-section, making it difficult to simultaneously characterize the spatial positional relationship between the front and rear ends of the shafting; second, some methods are highly dependent on sensor installation methods, coordinate unification, and measurement data processing, making it difficult to directly obtain the offset and angular deviation of the shafting; third, when the coordinate systems at different measuring ends are inconsistent, existing methods lack the ability to uniformly process data from multiple measuring cross-sections, affecting the accurate reconstruction of the actual central axis of the shafting.

[0005] Therefore, it is necessary to propose a ship propulsion shafting coaxiality measurement system and method based on two-dimensional displacement measurement to achieve rapid acquisition, unified calculation and reconstruction of the center axis of the forward and aft measurement sections of the shafting, thereby improving the accuracy and efficiency of shafting alignment parameter measurement. Summary of the Invention

[0006] This invention aims to provide a system and method for measuring the coaxiality of ship propulsion shafting based on two-dimensional displacement measurement, to solve the problems of low measurement efficiency, insufficient real-time performance, incomplete spatial pose representation of multiple measurement sections, and difficulty in uniformly calculating data from different measurement ends in the existing technology for measuring the alignment parameters of ship shafting. By constructing a two-dimensional displacement measurement structure with front and rear dual sections, and combining the solution of the center coordinates of the sections, coordinate system transformation, and reconstruction of the actual center axis, quantitative measurement of the offset, tilt, and coaxiality error of the measured shafting can be achieved.

[0007] The technical solution of the present invention is: a ship propulsion shaft coaxiality measurement system based on two-dimensional displacement measurement, characterized in that it includes: the shaft system to be measured, a front support 3, a rear support 8, a front displacement measurement unit, a rear displacement measurement unit, an air spring vibration isolator 14, a communication module 15, a computer 16, and a floating raft 17. The shaft system under test is mounted on the front support 3 and the rear support 8; the front displacement measuring unit is set at the corresponding position of the front measuring section of the shaft system under test; the rear displacement measuring unit is set at the corresponding position of the rear measuring section of the shaft system under test; the front support 3 and the rear support 8 are mounted on the raft 17; the air spring vibration isolator 14 is arranged at the bottom of the entire raft; the front displacement measuring unit and the rear displacement measuring unit are connected to the communication module 15; The communication module 15 transmits the acquired two-dimensional displacement information to the computer 16.

[0008] The measured shaft system includes a left end flange 1, a front shaft body 2, a front end connecting flange 4, a middle shaft section 5, a rear end connecting flange 6, a rear shaft body 7, and a right end flange 9, which are connected in sequence.

[0009] The front-end displacement measurement unit includes a front-end vertical displacement measurement unit 10 and a front-end horizontal displacement measurement unit 11, which are arranged in two mutually perpendicular directions to collect two-dimensional displacement information of the front-end measurement section of the measured shaft system. The rear-end displacement measurement unit includes a rear-end vertical displacement measurement unit 12 and a rear-end horizontal displacement measurement unit 13, which are arranged in two mutually perpendicular directions to collect two-dimensional displacement information of the rear-end measurement section of the measured shaft system.

[0010] Multiple air spring vibration isolators 14 are arranged at the bottom of the raft 17, in two rows symmetrically distributed along the axial direction to ensure uniform front-to-back distance. Each air spring vibration isolator 14 is independently controlled by the computer, and the position and posture of the measured shaft system in various directions are adjusted by adjusting the air pressure of each air spring vibration isolator 14.

[0011] A method for measuring the coaxiality of a ship's propulsion shafting based on two-dimensional displacement measurement includes the following steps: Step (1): Establish the measurement coordinate system for the front and rear measurement sections: The front-end and rear-end displacement measuring units are fixed at corresponding positions on the two end measuring sections and the distance is adjusted to within the measuring range; the installation reference distances in the horizontal and vertical directions of each measuring coordinate system are determined, and the displacement measurement values ​​of the front-end and rear-end measuring sections of the measured shaft system in two mutually perpendicular directions are obtained respectively; the installation reference distances of the front-end measuring sections are denoted as follows: The installation reference distances of the rear measuring section are respectively denoted as... The corresponding real-time sensor measurements are recorded as follows: , and 、 The radius of the cross section of the measured shaft system is denoted as . ; Step (2): The collected two-dimensional displacement information is transmitted to the computer 16 through the communication module 15, and the installation reference distance between the front end and the back end is entered into the computer to complete the basic parameter setting; Step (3): Analyze the center coordinates of the front and rear measurement sections: By comparing the measured values ​​from four displacement measurement units with the initial installation reference distance, the relative coordinates of the centers of the two end sections are calculated, and the coordinates of the center of the front measurement section are derived. satisfy: Rear end measurement section center coordinates satisfy: The positive and negative signs are selected based on the installation quadrant relationship of the sensor relative to the center of the measured cross section, the positive direction of the coordinate axis, and the geometric position relationship of the center of the measured cross section located inside or outside the corresponding sensor's measurement ray. Step (4), coordinate system transformation: When the coordinate system of the rear measurement section is inconsistent with that of the front measurement section, a coordinate transformation is performed on the center coordinates of the rear measurement section to uniformly transform them to the front measurement coordinate system or the preset global coordinate system. The transformation relationship is as follows: in, This is the coordinate transformation matrix from the backend measurement coordinate system to the unified coordinate system. The coordinates of the center of the measured section at the rear end in a unified coordinate system; Step (5): Based on the positional and angular deviations between the actual center axis and the reference axis in the horizontal and vertical directions, calculate the horizontal offset, vertical offset, horizontal deflection and vertical deflection of the measured shaft system, which are used as the characterization parameters of the coaxiality error of the measured shaft system. Step (6): The computer determines whether the coaxiality error calculated in step (5) exceeds the preset threshold. If it does, it enters the active centering adjustment mode. Step (7): In active adjustment mode, the computer outputs control commands to the air spring isolator 4 according to the coaxiality error obtained in step (5). The air spring isolator 14 adjusts the position and orientation of the measured shaft system according to the control commands until the coaxiality error meets the preset threshold.

[0012] The beneficial effects of the present invention are as follows: By setting mutually perpendicular displacement measurement units at the front and rear ends of the shaft system being measured, the present invention can simultaneously acquire two-dimensional displacement information of the two measurement sections when the shaft system is stationary, without driving the shaft system to rotate, thus simplifying the measurement process and improving the measurement efficiency of static alignment parameters of the ship propulsion shaft system.

[0013] This invention analyzes and obtains the center coordinates of the front and rear measurement sections based on the measured values ​​of each displacement measurement unit, the installation reference distance, and the geometric parameters of the measured shaft section. It then unifies the center coordinates of different measurement coordinate systems into the same coordinate system through coordinate transformation, thereby reducing the influence of sensor installation position and measurement coordinate system differences on the measurement results.

[0014] This invention reconstructs the actual central axis of the measured shaft system by using the center positions of the front and rear measurement sections, and obtains the positional and angular deviations in the horizontal and vertical directions, which can more completely characterize the spatial alignment state of the measured shaft system.

[0015] This invention combines shaft coaxiality measurement with the position adjustment of an air spring isolator. When the coaxiality error exceeds a preset threshold, the position of the raft and the measured shaft can be changed by adjusting the air pressure of the air spring isolator, providing a basis for the active alignment adjustment of the ship's propulsion shaft. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the ship propulsion shaft coaxiality measurement system based on two-dimensional displacement measurement according to the present invention.

[0017] Figure 2 This is a flowchart of the coaxiality detection process of the present invention.

[0018] Figure 3This is a schematic diagram of the coaxiality detection principle of the present invention.

[0019] In the diagram: 1-Front-end flange, 2-Front-end shaft section, 3-Front support seat, 4-Front-end connecting flange, 5-Intermediate shaft end, 6-Rear-end connecting flange, 7-Rear-end shaft section, 8-Rear support seat, 9-Rear-end flange, 10-Front-end vertical displacement measuring unit, 11-Front-end horizontal displacement measuring unit, 12-Tail-end vertical displacement measuring unit, 13-Tail-end horizontal displacement measuring unit, 14-Air spring vibration isolator, 15-Communication module, 16-Computer, 17-Floating raft. Detailed Implementation

[0020] 1. Establishment of communication connection and data acquisition; Multiple air spring isolators 14 are arranged at the bottom of the raft 17 to provide elastic support for the raft 17. Each air spring isolator 14 can be independently adjusted in air pressure. A front support 3 and a rear support 8 are installed on the raft 17, and the shaft system to be measured is mounted on the front support 3 and the rear support 8, placing the shaft system in a static measurement state. Perpendicular laser displacement sensors are arranged at the front and rear measurement sections, respectively.

[0021] Taking the front-end measurement section as an example, let the theoretical reference intersection of the front-end horizontal laser displacement sensor and the front-end vertical laser displacement sensor be the origin of the front-end local coordinate system. Let the preset distance from the origin to the horizontal measurement reference position at the front end be... The preset distance to the reference position in the vertical direction of the front end is The real-time measurement value of the front-end horizontal laser displacement sensor is recorded as follows: The real-time measurement value of the front-end vertical laser displacement sensor is recorded as follows: .

[0022] Similarly, the preset distance from the origin to the horizontal measurement reference position at the tail end in the local coordinate system is... The preset distance to the reference position in the vertical direction from the tail end is The real-time measurement value of the horizontal laser displacement sensor at the tail end is recorded as follows: The real-time measurement value of the vertical laser displacement sensor at the tail end is recorded as follows: .

[0023] Let the radius of the measured axial section be... .

[0024] The RS485 communication ports of the front-end and back-end measurement units are connected to a 485-to-USB converter module via communication lines A and B, respectively. The 485-to-USB converter module is then connected to a computer via a USB interface to establish a communication connection between the laser displacement sensor and the data processing unit. The computer, acting as the host computer, reads real-time measurement data from the front-end vertical laser displacement sensor, the front-end horizontal laser displacement sensor, the back-end vertical laser displacement sensor, and the back-end horizontal laser displacement sensor via serial communication. This real-time measurement data is then transmitted to the data processing program for subsequent calculations of the center coordinates of the measurement section, coordinate transformation, axis reconstruction, and static coaxiality error.

[0025] 2. Solving for the coordinates of the center of the cross-section; 1) Solving for the coordinates of the center of the front-end measurement section; Let the center of the front-end measurement section be in the front-end local coordinate system. The coordinates below are: Based on the geometric relationships measured at the front end, the coordinates of the circle center satisfy: After solving the simultaneous equations, the coordinates of the center of the front-end measurement section can be expressed as: 2) Solving for the coordinates of the center of the cross-section at the tail end; Assume the center of the measured section at the tail end is in the local coordinate system at the tail end. The coordinates below are: Based on the geometric relationship measured at the tail end, the coordinates of the center of the circle satisfy: The coordinates of the center of the measured section at the tail end can be expressed as: 3) Determining the sign of the center coordinates; In this embodiment, the initial sign branch in the formula for solving the center coordinates is determined based on the sensor installation parameters, the definition of the local coordinate system, and the preset range of change of the center of the measured shaft section. Since the inverse calculation of the center coordinates from two displacement measurement data yields two sets of candidate solutions that are mirror images of each other about the same dividing line, the effective sign branch needs to be determined in conjunction with the actual installation relationship. The dividing line is a symmetrical dividing line of the candidate center determined by both horizontal and vertical measurement constraints, which divides the center solutions corresponding to the two sign branches on both sides of this line. According to the installation parameters and adjustment range constraints in this embodiment, the center of the measured shaft section is located in the region below the dividing line during initial installation and subsequent adjustment. Therefore, the negative sign branch corresponding to this lower region is selected as the initial effective solution, and this sign branch remains unchanged when the range constraints are subsequently met. The range constraints are used to ensure that the center of the measured shaft section does not cross the dividing line during the measurement process, thereby preventing changes in the center coordinate solution branch.

[0026] 3. Unified transformation of front-end and back-end coordinates; In the actual device, the front-end local coordinate system With the tail end local coordinate system There may be origin offset, inconsistent coordinate axis directions, or rotation angle differences. Therefore, it is necessary to unify the coordinates of the front and rear center points into the same coordinate system.

[0027] In one implementation, the front-end local coordinate system is used as the unified coordinate system. If the tail-end local coordinate system only has a translational difference relative to the front-end local coordinate system, a simplified coordinate transformation relationship can be used: in, and These represent the coordinate offsets of the origin of the tail local coordinate system relative to the origin of the front local coordinate system in the horizontal and vertical directions, respectively. The coordinates of the center of the measured section at the tail end in a unified coordinate system.

[0028] In another implementation, if the tail-end local coordinate system is both translated and rotated relative to the front-end local coordinate system, then a rigid body coordinate transformation relationship is used: in, Let be the rotation angle of the local coordinate system at the tail end relative to the unified coordinate system. and This represents the translation amount.

[0029] In the preferred embodiment where the front-end local coordinate system is used as the unified coordinate system, it can be directly taken as... .

[0030] 4. Unified transformation of front-end and back-end coordinates; Let the coordinates of the center of the front measuring section in the unified coordinate system be: The coordinates of the center of the measured section at the tail end are: in, and These represent the axial coordinates of the front and rear measurement sections, respectively. ,in This represents the axial distance between the two measurement sections.

[0031] The actual central axis of the measured shaft system can be determined from the center point of the front end. and the center point of the tail end It is uniquely determined, and its parametric equation can be written as: in, The parameter is a real number.

[0032] 5. Coaxiality calculation; In this embodiment, the static alignment state of the measured shaft system is not characterized by a single comprehensive radial error, but is described by four parameters: horizontal offset, vertical offset, horizontal deflection, and vertical deflection.

[0033] 1) Horizontal offset represents the positional deviation of the measured shaft system relative to the reference axis in the horizontal direction.

[0034] In this embodiment, the front-end measurement section is used as the reference section, and the horizontal offset can be taken as... ; 2) Vertical offset represents the positional deviation of the measured axis system relative to the reference axis in the vertical direction.

[0035] In this embodiment, the front-end measurement section is used as the reference section, and the vertical offset can be taken as... ; 3) Horizontal deflection represents the degree of inclination of the actual central axis of the measured shaft system relative to the reference axis in the horizontal plane. It can be expressed as the ratio of the difference in the horizontal coordinates of the centers of the front and rear measurement sections to the axial distance, i.e. ; 4) Vertical deflection is used to characterize the degree of inclination of the actual central axis of the measured shaft system relative to the reference axis in the vertical plane. It can be expressed as the ratio of the difference in the vertical coordinates of the centers of the front and rear measurement sections to the axial distance, i.e. .

Claims

1. A ship propulsion shafting coaxiality measurement system based on two-dimensional displacement measurement, characterized in that, include: The shaft system under test, front support (3), rear support (8), front displacement measurement unit, rear displacement measurement unit, air spring vibration isolator (14), communication module (15), computer (16), and floating raft (17). The shaft system under test is mounted on the front support (3) and the rear support (8); the front displacement measuring unit is set at the corresponding position of the front measuring section of the shaft system under test; the rear displacement measuring unit is set at the corresponding position of the rear measuring section of the shaft system under test; the front support (3) and the rear support (8) are mounted on the raft (17); the air spring vibration isolator (14) is arranged at the bottom of the entire raft; the front displacement measuring unit and the rear displacement measuring unit are connected to the communication module (15). The communication module (15) transmits the collected two-dimensional displacement information to the computer (16).

2. The ship propulsion shafting coaxiality measurement system based on two-dimensional displacement measurement according to claim 1, characterized in that, The measured shaft system includes a left end flange (1), a front shaft body (2), a front end connecting flange (4), a middle shaft section (5), a rear end connecting flange (6), a rear shaft body (7), and a right end flange (9) connected in sequence.

3. The ship propulsion shafting coaxiality measurement system based on two-dimensional displacement measurement according to claim 1, characterized in that, The front displacement measurement unit includes a front vertical displacement measurement unit (10) and a front horizontal displacement measurement unit (11). The front vertical displacement measurement unit (10) and the front horizontal displacement measurement unit (11) are arranged in two mutually perpendicular directions to collect two-dimensional displacement information of the front measurement section of the measured shaft system. The rear displacement measurement unit includes a rear vertical displacement measurement unit (12) and a rear horizontal displacement measurement unit (13). The rear vertical displacement measurement unit (12) and the rear horizontal displacement measurement unit (13) are arranged in two mutually perpendicular directions to collect two-dimensional displacement information of the rear measurement section of the measured shaft system.

4. The ship propulsion shafting coaxiality measurement system based on two-dimensional displacement measurement according to claim 1, characterized in that, The air spring isolators (14) are multiple and arranged at the bottom of the raft (17). They are distributed in two rows symmetrically along the axial direction and the front and rear distances are uniform. Each air spring isolator (14) is independently controlled by the computer. The position and posture of the measured shaft system in each direction are adjusted by adjusting the air pressure of each air spring isolator (14).

5. A method for measuring the coaxiality of a ship's propulsion shafting based on two-dimensional displacement measurement, characterized in that, Includes the following steps: Step (1): Establish the measurement coordinate system for the front and rear measurement sections: Fix the front displacement measuring unit and the rear displacement measuring unit at the corresponding positions of the measuring sections at both ends and adjust the distance to within the range; determine the installation reference distance in the horizontal and vertical directions in each measuring coordinate system and obtain the displacement measurement values ​​of the front measuring section and the rear measuring section of the measured shaft system in two mutually perpendicular directions respectively; The installation reference distance of the front-end measuring section is denoted as follows: The installation reference distances of the rear measuring section are respectively denoted as... The corresponding real-time sensor measurements are recorded as follows: , and 、 The radius of the cross section of the measured shaft system is denoted as ; Step (2): The collected two-dimensional displacement information is transmitted to the computer (16) through the communication module (15), and the installation reference distance between the front end and the back end is entered into the computer to complete the basic parameter setting; Step (3): Analyze the center coordinates of the front and rear measurement sections: By comparing the measured values ​​from four displacement measurement units with the initial installation reference distance, the relative coordinates of the centers of the two end sections are calculated, and the coordinates of the center of the front measurement section are derived. satisfy: Rear end measurement section center coordinates satisfy: The positive and negative signs are selected based on the installation quadrant relationship of the sensor relative to the center of the measured cross section, the positive direction of the coordinate axis, and the geometric position relationship of the center of the measured cross section located inside or outside the corresponding sensor's measurement ray. Step (4), coordinate system transformation: When the coordinate system of the rear measurement section is inconsistent with that of the front measurement section, a coordinate transformation is performed on the center coordinates of the rear measurement section to uniformly transform them to the front measurement coordinate system or the preset global coordinate system. The transformation relationship is as follows: in, This is the coordinate transformation matrix from the backend measurement coordinate system to the unified coordinate system. The coordinates of the center of the measured section at the rear end in a unified coordinate system; Step (5): Based on the positional and angular deviations between the actual center axis and the reference axis in the horizontal and vertical directions, calculate the horizontal offset, vertical offset, horizontal deflection and vertical deflection of the measured shaft system, which are used as the characterization parameters of the coaxiality error of the measured shaft system. Step (6): The computer determines whether the coaxiality error calculated in step (5) exceeds the preset threshold. If it does, it enters the active centering adjustment mode. Step (7): In active adjustment mode, the computer outputs control commands to the air spring vibration isolator (14) based on the coaxiality error obtained in step (5). The air spring vibration isolator (14) adjusts the position and orientation of the measured shaft system according to the control commands until the coaxiality error meets the preset threshold.

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