A ship shafting automatic centering correction system and a control method thereof

Abstract

A kind of ship shafting automatic centering correction system, first laser displacement sensor group being arranged between the output flange of ship main engine and intermediate shaft, second laser displacement sensor group being arranged between intermediate shaft and tail shaft, multiple degrees of freedom hydraulic adjusting actuator being respectively installed on main engine pedestal and tail shaft support, data acquisition module being signal connected with first laser displacement sensor group and second laser displacement sensor group, central processing unit being communication connected with data acquisition module, and drive control module being connected with central processing unit control signal output end.This application adopts two groups of laser ranging probe arranged along circumference, respectively arranged in the connecting area of main engine output flange to intermediate shaft and intermediate shaft to tail shaft, covers the interface of propelling shafting from space, through synchronous trigger unit and main shaft speed encoder hard line connection, eliminates false misjudgment caused by different sampling phase.

Description

Technical Field

[0001] This invention belongs to the field of ship control technology, specifically an automatic alignment and correction system for ship shafting and its control method. Background Technology

[0002] As the transmission component connecting the main engine and the propeller, the installation of the ship's propulsion shafting directly affects the operating efficiency, vibration and noise levels, bearing life, and even navigation safety of the entire ship's power system. During ship construction or major overhaul, the main engine output shaft, intermediate shaft, and stern shaft must be coaxially aligned; otherwise, it will lead to severe additional bending moments, bearing overheating, seal failure, and even catastrophic shaft breakage. However, the traditional alignment methods commonly used in existing technologies have the following technical problems: First, the current mainstream alignment methods are still mainly based on the steel wire method, the ruler and feeler gauge method, or optical alignment instruments. Due to human reading errors, line of sight deviations, or interference from ambient light, even under the same working conditions, the results of multiple measurements are significantly different, making it difficult to guarantee engineering requirements. Especially in the confined, high-temperature, and high-humidity cabin environment, the operational difficulty is further increased, and the alignment quality fluctuates drastically.

[0003] Secondly, traditional methods typically involve measurements taken when the main shaft is completely stationary. However, ship shafting systems undergo dynamic displacement during actual operation due to thermal expansion, hull deformation, and main engine vibration. Static alignment cannot capture the true geometric centerline of the shaft segment during rotation, often resulting in "correct alignment in cold conditions but abnormal operation in hot conditions." Furthermore, if the two sets of measurement points (such as the main engine end and the stern shaft end) do not collect data synchronously at the same circumferential angle on the main shaft, this is almost unavoidable during manual operation. Even if the shaft itself is not eccentric, the different sampling phases can lead to misjudgments of radial or angular misalignment, causing unnecessary rework or incorrect adjustments.

[0004] Third, the temperature inside a ship's engine room fluctuates dramatically, with a diurnal temperature range exceeding 20°C, and local temperatures can exceed 60°C during main engine operation. Existing centering devices often use ordinary metal supports that do not account for thermal expansion. When the supports deform due to heat, the position of the laser probes or optical components fixed to them shifts, causing measurement reference drift and introducing systematic errors. Summary of the Invention

[0005] In view of the above situation and to overcome the defects of the prior art, the present invention provides an automatic alignment and correction system for ship shafting and its control method, so as to at least partially solve the above technical problems.

[0006] The technical solution adopted in this invention is as follows: This invention proposes an automatic alignment and correction system for ship shafting, comprising: A first laser displacement sensor group is installed between the main engine output flange and the intermediate shaft; a second laser displacement sensor group is installed between the intermediate shaft and the stern shaft; a multi-degree-of-freedom hydraulic adjustment actuator is installed on the main engine base and the stern shaft support respectively; a data acquisition module is connected to the first laser displacement sensor group and the second laser displacement sensor group; a central processing unit is connected to the data acquisition module; and a drive control module is connected to the control signal output terminal of the central processing unit. The multi-degree-of-freedom hydraulic adjustment actuator includes at least three hydraulic cylinders arranged in a triangular pattern. Each hydraulic cylinder is connected to the main unit base or tail shaft support and the base of the adjusted equipment respectively through a ball joint structure. It is used to independently adjust the height and horizontal offset under the command issued by the central processing unit. The first laser displacement sensor group and the second laser displacement sensor group each include no less than four laser ranging probes evenly arranged along the circumference. The measuring optical axis of the probe points perpendicularly to the outer circular surface of the corresponding shaft segment and is fixed on a rigid mounting bracket. The rigid mounting bracket is fastened to an adjacent stationary structural member by bolts.

[0007] In one embodiment of the present invention, the rigid mounting bracket is provided with a temperature compensation structure, including an embedded thermocouple and a metal expansion compensation piece thermally coupled thereto. One end of the metal expansion compensation piece is fixed to the bracket body, and the other end is connected to the laser ranging probe mounting base to counteract the influence of bracket deformation caused by changes in ambient temperature on the measurement reference.

[0008] In one embodiment of the present invention, each hydraulic cylinder in the multi-degree-of-freedom hydraulic adjustment actuator is equipped with a displacement feedback sensor. The displacement feedback sensor is a magnetostrictive displacement sensor, whose measuring rod is coaxially fixed to the piston rod of the hydraulic cylinder, and whose housing is fixed to the outer wall of the hydraulic cylinder barrel. The output signal is connected to the central processing unit in real time for closed-loop control of the extension and retraction stroke of the hydraulic cylinder.

[0009] In one embodiment of the present invention, the data acquisition module integrates a synchronous triggering unit, which is connected to the ship's main shaft speed encoder via a hard wire. When the main shaft rotates to a preset angle position, the first laser displacement sensor group and the second laser displacement sensor group are synchronously triggered to sample simultaneously, ensuring that the two groups of sensors acquire shaft center position data at the same phase angle.

[0010] In one embodiment of the present invention, the central processing unit has a built-in axis fitting algorithm module. After receiving multi-point radial distance data from the data acquisition module, the algorithm module fits the instantaneous rotation center lines of the main output shaft segment and the tail shaft segment respectively based on the least squares method, and calculates the offset and included angle of the two center lines in space to generate a three-dimensional alignment error vector.

[0011] In one embodiment of the present invention, the drive control module includes multiple proportional servo valves. The control input terminal of each proportional servo valve is connected to the analog output channel of the central processing unit, and its pressure oil outlet is connected to the rodless chamber and rod chamber of the corresponding hydraulic cylinder, respectively. The precise fine adjustment of the hydraulic cylinder is realized through differential control.

[0012] In one embodiment of the present invention, a safety interlock device is further included, which includes a relay contact disposed in the host start-up circuit. The relay coil is controlled by the central processing unit. The relay closes only when the system detects that the shaft alignment error is less than a preset threshold, allowing the host start-up circuit to conduct.

[0013] In one embodiment of the present invention, the rigid mounting brackets of the first laser displacement sensor group and the second laser displacement sensor group are provided with an adjustable pitch and yaw fine-tuning mechanism. The fine-tuning mechanism consists of two sets of orthogonally arranged precision lead screws. The lead screw nuts are connected to the laser ranging probe mounting base and are used to manually calibrate the perpendicularity of the optical axis of each laser probe during the initial installation stage of the system.

[0014] In one embodiment of the present invention, the central processing unit is connected to a remote monitoring terminal via an industrial Ethernet interface, and the modules within the system communicate with each other via a CAN bus, wherein the data acquisition module, drive control module and displacement feedback sensor are all connected as CAN bus nodes.

[0015] In one embodiment of the present invention, a control method for an automatic alignment and correction system for a ship's shafting includes the following steps: Step S1: When the ship's main shaft is stationary, the first laser displacement sensor group and the second laser displacement sensor group are controlled by the synchronous triggering unit to synchronously collect the distance data from each laser probe to the outer circular surface of the corresponding shaft segment at the same circumferential angle position of the main shaft. Step S2: Transmit the collected distance data to the central processing unit, and use the axis fitting algorithm module to calculate the instantaneous rotation center coordinates and direction vectors of the main output shaft segment and the tail shaft segment respectively; Step S3: Based on the spatial relationship between the centerlines of the two shafts, calculate the three-dimensional displacement required to adjust the main engine base and tail shaft support, and convert it into the target extension stroke of each hydraulic cylinder. Step S4: The central processing unit sends a control signal to the drive control module to drive the corresponding proportional servo valve to adjust the hydraulic cylinder's action. At the same time, it reads the displacement feedback sensor signals of each hydraulic cylinder and implements closed-loop control until the deviation between the actual displacement and the target stroke is less than the set tolerance. Step S5: Repeat steps S1 to S4 until the change in the magnitude of the shaft alignment error vector calculated twice consecutively is less than the preset convergence threshold, thus completing the automatic alignment correction.

[0016] The beneficial effects of the technical solution of this invention are as follows: This invention employs two sets of laser ranging probes (no fewer than four) evenly arranged circumferentially, respectively positioned in the connection areas from the main engine output flange to the intermediate shaft and from the intermediate shaft to the tail shaft. This spatially covers the docking interface of the propulsion shaft system. A synchronous trigger unit is hardwired to the main shaft speed encoder, ensuring that the two sets of sensors sample synchronously at the same circumferential angular position on the main shaft, eliminating false misalignment caused by asynchronous sampling phases. Simultaneously, the rigid mounting bracket not only secures itself to the stationary structural components of the hull with bolts to ensure reference stability but also integrates a temperature compensation structure based on embedded thermocouples and metal expansion compensators. When ambient temperature changes cause thermal expansion and contraction of the bracket, the compensators deform in the opposite direction, dynamically offsetting the influence of bracket deformation on the spatial position of the laser probes. This ensures that the measurement reference remains stable in the complex engine room environment, including cold starts, hot operation, and even drastic day-night temperature fluctuations.

[0017] This invention utilizes at least three triangularly distributed hydraulic cylinders mounted on the main base and tail shaft support, connected to the base of the device being adjusted via a ball joint structure, forming a three-point support system with fully constrained degrees of freedom. This system allows for independent adjustment of vertical height and differential expansion to achieve composite horizontal displacement, effectively decoupling translational and tilting motions and avoiding over-constraint of the mechanism. Each hydraulic cylinder is equipped with a magnetostrictive displacement sensor, whose measuring rod is coaxially fixed to the piston rod, providing real-time feedback of the actual stroke to the central processing unit, forming an inner-loop position closed loop. The drive control module employs a proportional servo valve to differentially control the rod-side and rodless sides of the hydraulic cylinders, resulting in fast response speed, high control linearity, and achieving a fine-tuning accuracy of ±5μm.

[0018] This invention utilizes the axis fitting algorithm module built into the central processing unit to perform three-dimensional reconstruction of multi-angle and multi-point radial distance data based on the least squares method. It fits the instantaneous rotation center lines of the main output shaft segment and the tail shaft segment respectively, and calculates their radial offset and angular angle in space to generate a complete three-dimensional alignment error vector. The system continuously approaches the optimal alignment state through an iterative cycle of "measurement, calculation, execution, and remeasurement" until the change in error vector is less than the preset convergence threshold for two consecutive times, ensuring that the results are stable and reliable.

[0019] Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0020] The above and / or additional aspects and advantages of the present invention will become apparent and readily understood from the following description of the embodiments taken in conjunction with the accompanying drawings, wherein: Figure 1 This is a block diagram of the architecture of the automatic alignment and correction system for ship shafting proposed in an embodiment of the present invention. Figure 2 This is a first functional framework diagram of the automatic alignment and correction system for ship shafting proposed in an embodiment of the present invention; Figure 3 This is a functional framework diagram of the second architecture of the automatic alignment and correction system for ship shafting proposed in an embodiment of the present invention; Figure 4 This is a framework diagram of the control method for the automatic alignment and correction system of ship shafting proposed in an embodiment of the present invention. Detailed Implementation

[0021] Embodiments of the present invention are described in detail below, examples of which are illustrated in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention.

[0022] An automatic alignment and correction system for ship shafting and its control method according to an embodiment of the present invention are described below with reference to the accompanying drawings.

[0023] like Figures 1 to 4 As shown, this embodiment of the invention provides an automatic alignment and correction system for a ship's shafting, comprising: a first laser displacement sensor group disposed between the ship's main engine output flange and the intermediate shaft; a second laser displacement sensor group disposed between the intermediate shaft and the stern shaft; a multi-degree-of-freedom hydraulic adjustment actuator respectively mounted on the main engine base and the stern shaft support; a data acquisition module connected to the first and second laser displacement sensor groups; a central processing unit communicatively connected to the data acquisition module; and a drive control module connected to the control signal output terminal of the central processing unit. The multi-degree-of-freedom hydraulic adjustment actuator includes at least three hydraulic cylinders arranged in a triangular pattern. Each hydraulic cylinder is connected to the main unit base or tail shaft support and the base of the adjusted equipment respectively through a ball joint structure. It is used to independently adjust the height and horizontal offset under the command issued by the central processing unit. Both the first and second laser displacement sensor groups contain no fewer than four laser ranging probes evenly arranged along the circumference. The measuring optical axis of the probe points perpendicularly to the outer circular surface of the corresponding shaft segment and is fixed on a rigid mounting bracket. The rigid mounting bracket is fastened to an adjacent stationary structural member by bolts.

[0024] In a specific application of this invention, after the system is started, the first laser displacement sensor group located in the connection area between the main output flange and the intermediate shaft, and the second laser displacement sensor group located in the connection area between the intermediate shaft and the tail shaft, synchronously collect radial distance data of the outer circular surface of the shaft segment. Each of the two sensor groups contains no less than four laser ranging probes evenly distributed along the circumference. The measuring optical axis of all probes is perpendicular to the outer circular surface of the shaft segment being measured, and they are firmly fixed to adjacent stationary structural components (such as cabin ribs, bases, or supports) by rigid mounting brackets to ensure the stability and repeatability of the measurement reference. When the main shaft is in a slow rotation or stationary state, the laser beam emitted by the laser probe hits the metal surface of the corresponding shaft segment in real time. The reflected signal is converted into a high-resolution distance value by the internal photoelectric element and transmitted to the data acquisition module through a shielded cable.

[0025] After receiving the raw distance data, the data acquisition module immediately performs filtering, noise reduction, and timestamp alignment processing, and then uploads the processed multi-channel data packets to the central processing unit via a high-speed communication link. The spatial geometric analysis algorithm built into the central processing unit is then activated. Based on the least squares principle, it performs circle center fitting on the data from no less than four measuring points in each group, reconstructing the instantaneous rotation center lines of the main output shaft segment and the tail shaft segment under the current operating conditions. The center lines not only contain the position coordinates of the shaft center in the horizontal and vertical directions, but also its tilt angle information in three-dimensional space. By comparing the relative positional relationship between the two fitted center lines, the system can calculate the radial offset (i.e., parallel misalignment) and angular deviation (i.e., angular misalignment) at the docking end face, and then synthesize a complete three-dimensional alignment error vector.

[0026] The error vector is then input into the preset inverse kinematic model. The model performs coordinate transformation based on the mechanical layout of the multi-degree-of-freedom hydraulic adjustment actuators installed on the main unit base and tail shaft support (i.e., at least three hydraulic cylinders distributed in a triangle and their ball joint connection). The overall alignment correction requirement is decomposed into independent extension and retraction stroke commands to be executed by each hydraulic cylinder. Each hydraulic cylinder is connected to the fixed base (main unit base or tail shaft support) at one end through a ball joint structure, and to the base of the adjusted equipment (main unit or tail shaft bearing housing) at the other end. The universal connection allows the hydraulic cylinder to adapt to small angle changes while bearing load, thereby providing lifting and lowering adjustment capability in the vertical direction. In the horizontal plane, the differential extension and retraction of different hydraulic cylinders achieves composite displacement in the lateral and longitudinal directions. After receiving the digital control signal from the central processing unit, the drive control module converts it into analog voltage or current output, regulates the opening of multiple proportional servo valves, and allows high-pressure hydraulic oil to flow into the rod chamber or rodless chamber of the corresponding hydraulic cylinder as needed, pushing the piston rod to produce displacement.

[0027] Meanwhile, the magnetostrictive displacement feedback sensor on the hydraulic cylinder monitors the actual position of the piston rod in real time and transmits the displacement signal back to the central processing unit, forming a closed-loop control circuit. The central processing unit continuously compares the target stroke with the actual feedback value and dynamically adjusts the output control quantity until each hydraulic cylinder reaches the set position and the overall shaft alignment error converges to the allowable tolerance range. Throughout the adjustment process, the system can repeatedly execute the closed-loop process of "measurement, calculation, adjustment, and remeasurement" to ensure the stability and reliability of the final alignment result. In addition, since all laser sensor brackets adopt a rigid structure and are bolted to the stationary components of the hull, measurement drift caused by the flexible deformation of the brackets is avoided; while the triangularly distributed multi-point hydraulic support structure provides sufficient constrained degrees of freedom, effectively decoupling the adjustment actions in the vertical and horizontal directions and preventing over-constraint or under-constraint of the mechanism.

[0028] In one specific embodiment, the rigid mounting bracket is equipped with a temperature compensation structure, including an embedded thermocouple and a metal expansion compensation plate thermally coupled thereto. One end of the metal expansion compensation plate is fixed to the bracket body, and the other end is connected to the laser ranging probe mounting base to counteract the influence of bracket deformation caused by changes in ambient temperature on the measurement reference. Each hydraulic cylinder in the multi-degree-of-freedom hydraulic adjustment actuator is equipped with a displacement feedback sensor. The displacement feedback sensor is a magnetostrictive displacement sensor, whose measuring rod is coaxially fixed to the hydraulic cylinder piston rod, and whose outer shell is fixed to the outer wall of the hydraulic cylinder barrel. The output signal is connected to the central processing unit in real time for closed-loop control of the extension and retraction stroke of the hydraulic cylinder.

[0029] In practical applications of this invention, when the system is in an engine room environment, the local temperature of the rigid mounting bracket continuously changes due to factors such as main engine operation, seawater temperature variations, or day-night cycles. If the bracket material undergoes slight deformation due to thermal expansion and contraction, it can also cause a spatial position shift of the laser ranging probe, thereby introducing false axis deviation signals and interfering with alignment judgment. To address this, the system integrates an embedded thermocouple inside the rigid mounting bracket. The thermocouple is tightly attached to the metal body of the bracket and can sense the current temperature of the bracket in real time. The temperature signal output by the thermocouple is sent to the central processing unit, triggering a temperature and deformation compensation algorithm. The algorithm pre-establishes a thermal deformation model based on the linear expansion coefficient of the bracket material and drives the thermally coupled metal expansion compensation plate to perform reverse deformation adjustment. Specifically, one end of the metal expansion compensation plate is firmly fixed to the bracket body, and the other end is rigidly connected to the mounting base of the laser ranging probe. When the bracket is heated and expands, the compensation plate will generate deformations in opposite directions and with matching amplitudes due to the use of bimetallic structures with different coefficients of thermal expansion or preset stress. This will drive the probe mounting base to perform micro-displacement compensation, so that the measurement reference point of the laser ranging probe remains relatively constant in space.

[0030] Meanwhile, at the actuator end, each hydraulic cylinder used to support and adjust the main unit or tail shaft bracket is equipped with a magnetostrictive displacement sensor. The sensor's probe is strictly coaxially fixed to the hydraulic cylinder piston rod via a coupling structure, and its housing is rigidly fixed to the outer wall of the hydraulic cylinder barrel, forming a displacement detection channel that is completely synchronized with the hydraulic actuation action. After the central processing unit calculates the target stroke of each hydraulic cylinder based on the shaft alignment error, the drive control module outputs the corresponding control signal to adjust the opening of the proportional servo valve, allowing hydraulic oil to enter the cylinder chamber as needed, pushing the piston rod to extend or retract. During this process, the magnetostrictive displacement sensor detects the actual displacement of the piston rod in real time in a non-contact manner, and feeds back the displacement data to the central processing unit with high resolution (typically ±1μm) and high frequency (up to several kilohertz). The central processing unit compares this measured value with the target stroke and uses PID or other advanced control algorithms to dynamically correct the output signal, realizing closed-loop control of the hydraulic cylinder action. This ensures that when multiple cylinders are adjusted in tandem, they can follow the preset motion trajectory, avoiding twisting or tilting of the equipment base due to response deviations of individual cylinders.

[0031] In one specific implementation, the data acquisition module integrates a synchronous triggering unit, which is connected to the ship's main shaft speed encoder via a hard wire. When the main shaft rotates to a preset angle position, the first laser displacement sensor group and the second laser displacement sensor group are simultaneously triggered to sample, ensuring that the two sets of sensors acquire shaft center position data at the same phase angle. The central processing unit has a built-in axis fitting algorithm module. After receiving multi-point radial distance data from the data acquisition module, the algorithm module fits the instantaneous rotation center lines of the main engine output shaft segment and the tail shaft segment based on the least squares method, and calculates the offset and included angle of the two center lines in space to generate a three-dimensional alignment error vector.

[0032] In practical applications, when the spindle rotates slowly (typically driven by a turning device, with the speed controlled between 1 and 3 rpm), a high-resolution incremental or absolute speed encoder mounted on the spindle outputs angle pulse signals in real time. These signals are directly connected to the synchronization trigger unit inside the data acquisition module via shielded hard wires, avoiding timing uncertainties caused by communication delays or software interruptions. The synchronization trigger unit presets one or more reference angle positions (e.g., 0°, 90°, 180°, 270°). Once the spindle angle fed back by the encoder reaches any preset point, the trigger unit immediately generates a high-level synchronization pulse and simultaneously sends hardware-level sampling commands to the first and second laser displacement sensor groups. Because the trigger signals are distributed in parallel hard wires, the two sensor groups complete synchronous exposure and distance reading within microseconds, ensuring that the data collected at each measurement point corresponds to the state of the spindle in the same circumferential cross-section.

[0033] The acquired multi-channel radial distance data (each group has no fewer than four measuring points) is then packaged and transmitted to the central processing unit. The axis fitting algorithm module in the central processing unit immediately initiates the geometric reconstruction process: First, for each group of sensors acquiring multiple radial distance values ​​at a certain fixed angle, combined with the known spatial coordinates of each laser probe on the mounting bracket, the center position of the outer circle of the measured shaft segment on the cross section is solved inversely; then, after the main shaft completes at least one rotation, the system accumulates the center coordinates at multiple angular positions, and uses a three-dimensional least squares fitting algorithm to fit the discrete center points into an optimal straight line, that is, the current actual instantaneous rotation center line of the shaft segment. The center line not only contains the position information of the shaft center in the X and Y directions, but also reflects its tilt attitude in the Z-axis direction through the spatial slope.

[0034] The system calculates the shortest distance (radial offset) between the two axes in the plane perpendicular to the axis and the angle (angular deviation) between the two linear direction vectors by vector operations. These two parameters are then fused into a three-dimensional alignment error vector with direction and magnitude. This vector fully describes the misalignment state of the current shaft system in space and serves as the sole basis for subsequent actuator action decisions. The entire process from synchronous sampling to error vector generation is highly automated, and all calculations are based on real physical measurements. Even if the shaft segment has local bending, surface roughness, or slight vibration, the system can still effectively suppress noise interference and extract stable geometric features through multi-point averaging and least squares optimization.

[0035] In one specific implementation, the drive control module includes multiple proportional servo valves. The control input of each proportional servo valve is connected to the analog output channel of the central processing unit, and its pressure oil outlet is connected to the rodless chamber and rod chamber of the corresponding hydraulic cylinder, respectively. The hydraulic cylinder is precisely fine-tuned through differential control. The module also includes a safety interlock device, which includes relay contacts installed in the host start-up circuit. The relay coil is controlled by the central processing unit. The relay closes only when the system detects that the shaft alignment error is less than a preset threshold, allowing the host start-up circuit to conduct.

[0036] In practical applications of this invention, after the central processing unit completes the calculation of the three-dimensional alignment error vector of the shaft system, it decomposes the overall correction requirement into the target displacement required by each hydraulic cylinder based on the topology of the multi-degree-of-freedom hydraulic adjustment actuator (such as three hydraulic cylinders in a triangular distribution). This target displacement is then sent from the central processing unit's dedicated analog output channel to multiple corresponding proportional servo valves in the form of a high-resolution analog voltage signal (typically ±10V or 4–20mA). Each proportional servo valve, as an electro-hydraulic conversion element, has a valve core opening that is linearly related to the input electrical signal, thereby regulating the flow and pressure of hydraulic oil entering the rodless and rod chambers of the hydraulic cylinder. Through a differential control strategy, i.e., simultaneously adjusting the inlet / outlet oil state of the two chambers, the system can achieve bidirectional smooth movement of the piston rod: for example, when the hydraulic cylinder needs to extend, the proportional servo valve conducts pressure oil to the rodless chamber while simultaneously opening the return oil channel of the rod chamber; conversely, it supplies oil in the opposite direction.

[0037] Throughout the adjustment process, the actual displacement of the hydraulic cylinders is fed back to the central processing unit in real time by the magnetostrictive sensor, forming an inner-loop position closed loop. The central processing unit continuously compares the target displacement with the measured value and dynamically corrects the control signal output to the proportional servo valve until the error converges within the set tolerance range. Once all hydraulic cylinders have reached the target position, the system triggers the laser sensor group again for retesting to verify the alignment effect. If the final calculated shaft alignment error vector magnitude (combining radial offset and angular deviation) is less than the preset safety threshold (e.g., radial deviation ≤ 0.05 mm, angular deviation ≤ 0.1° / m), the central processing unit determines that the correction is successful and immediately activates the safety interlock logic.

[0038] At this point, the central processing unit outputs an enable signal to the relay coil in the safety interlock device, energizing it and closing the normally open contact connected in series in the ship's main engine start-up control circuit. Only when this contact is closed can the main engine start button or remote start / stop command effectively activate the main control relay, thereby connecting the fuel supply, ignition system, or electric motor drive circuit, allowing the main engine to start normally. Conversely, if the system detects that the alignment error still exceeds the allowable range, or if sensor failure, hydraulic leakage, or communication interruption occurs during the calibration process, the central processing unit will keep the relay coil de-energized, its contacts remaining open, physically cutting off the main engine start-up path.

[0039] In one specific implementation, the rigid mounting brackets of the first and second laser displacement sensor groups are equipped with adjustable pitch and yaw fine-tuning mechanisms. The fine-tuning mechanisms consist of two sets of orthogonally arranged precision lead screws. The lead screw nuts are connected to the laser ranging probe mounting base and are used to manually calibrate the perpendicularity of the optical axis of each laser probe during the initial installation phase of the system. The central processing unit is connected to a remote monitoring terminal through an industrial Ethernet interface, and the modules within the system communicate with each other via a CAN bus. The data acquisition module, drive control module, and displacement feedback sensor are all connected as CAN bus nodes.

[0040] In practical applications of this invention, during initial system installation or redeployment after major overhaul, although the laser ranging probes are fixed on rigid mounting brackets, the measurement optical axes of each probe cannot be naturally guaranteed to be perpendicular to the outer circular surface of the measured axis segment due to welding deformation of the hull structure, base processing errors, or on-site assembly tolerances. If there is a pitch or yaw angle deviation in the optical axis, even if it is only a few tenths of a degree, it will cause the laser ranging value to contain cosine error, distorting the reconstruction result of the axis position. To address this, an adjustable pitch and yaw fine-tuning mechanism is integrated into the rigid mounting bracket of each laser displacement sensor group. The mechanism consists of two sets of orthogonally arranged ball screws: one set controls the pitch angle of the probe in the vertical plane, and the other set controls its yaw angle in the horizontal plane. The screw nut is directly connected to the mounting base of the laser ranging probe. The operator can drive the screw to produce a micron-level linear displacement by rotating the external fine-tuning handwheel, thereby causing the probe mounting base to rotate at a small angle around a specific fulcrum. During the initial debugging phase, technicians used a mandrel or optical autocollimator as a reference to observe the consistency of the raw distance data fed back by the central processing unit while repeatedly adjusting the two sets of lead screws until the distance fluctuation output by all probes on the same cross section was minimal when the axis rotated one revolution, indicating that each optical axis was basically perpendicular to the actual rotation center of the axis.

[0041] After mechanical calibration is completed, the system enters normal operation. The system adopts a layered communication architecture: at the bottom layer, all control and feedback devices with high real-time requirements, including the data acquisition module, drive control module, and magnetostrictive displacement feedback sensors on each hydraulic cylinder, are connected to the CAN (Controller Area Network) bus as independent nodes. The CAN bus, with its high anti-interference capability, multi-master arbitration mechanism, and deterministic transmission delay, is particularly suitable for industrial scenarios with complex electromagnetic environments and long wiring distances, such as ship engine rooms. Each node periodically broadcasts or sends data through predefined message IDs or event-triggered transmission. For example, the displacement sensor uploads the piston rod position at a frequency of 1kHz, the data acquisition module immediately publishes multi-channel distance values ​​after each synchronous sampling, and the drive control module receives valve control commands from the central processing unit and sends back the execution status.

[0042] At the upper layer, the central processing unit establishes a high-speed connection with remote monitoring terminals (such as industrial control computers in the engine room control room or shore-based maintenance platforms) via an industrial Ethernet interface. The interface adopts the TCP / IP protocol stack and supports OPCUA and ModbusTCP industrial standards. It is used to upload complete alignment process data (such as error vector history, hydraulic cylinder stroke curves, and temperature compensation status), receive remote start / stop commands, download and update algorithm parameters, or perform fault diagnosis. The high bandwidth of industrial Ethernet enables high-definition trend charts, 3D alignment status visualization interfaces, and alarm logs to be displayed in real time, improving human-machine interaction efficiency and maintenance transparency. More importantly, the upper-layer communication and the lower-layer CAN bus achieve protocol conversion and data fusion through the central processing unit: for example, when the remote terminal issues a "start automatic alignment" command, the central processing unit parses the command, coordinates each node in the CAN network to execute the measurement, calculation, and adjustment processes in sequence, and summarizes the phased results and transmits them back via Ethernet.

[0043] In one specific implementation, the control method for an automatic alignment and correction system for a ship's shafting includes the following steps: Step S1: When the ship's main shaft is stationary, the first laser displacement sensor group and the second laser displacement sensor group are controlled by the synchronous triggering unit to synchronously collect the distance data from each laser probe to the outer circular surface of the corresponding shaft segment at the same circumferential angle position of the main shaft. Step S2: Transmit the collected distance data to the central processing unit, and use the axis fitting algorithm module to calculate the instantaneous rotation center coordinates and direction vectors of the main output shaft segment and the tail shaft segment respectively; Step S3: Based on the spatial relationship between the centerlines of the two shafts, calculate the three-dimensional displacement required to adjust the main engine base and tail shaft support, and convert it into the target extension stroke of each hydraulic cylinder. Step S4: The central processing unit sends a control signal to the drive control module to drive the corresponding proportional servo valve to adjust the hydraulic cylinder's action. At the same time, it reads the displacement feedback sensor signals of each hydraulic cylinder and implements closed-loop control until the deviation between the actual displacement and the target stroke is less than the set tolerance. Step S5: Repeat steps S1 to S4 until the change in the magnitude of the shaft alignment error vector calculated twice consecutively is less than the preset convergence threshold, thus completing the automatic alignment correction.

[0044] In practical applications of this invention, after system startup, the first step is to ensure that the ship's main shaft is completely stationary or rotating at an extremely low speed (typically below 1 rpm) driven by a turning gear, to avoid dynamic vibration interfering with measurement accuracy. Under this premise, the synchronization trigger unit monitors the angle signal output by the main shaft speed encoder in real time. Once the main shaft rotates to a preset reference angle position (e.g., 0°), it immediately issues a hardware-level synchronization pulse, forcing the first and second laser displacement sensor groups to complete sampling within the same millisecond window. Based on the physical hard-triggered synchronization mechanism, it ensures that the data acquired by the two sets of sensors correspond to the same circumferential section of the main shaft in space, thereby eliminating false misalignment errors introduced by asynchronous sampling phases.

[0045] Upon receiving the data, the central processing unit immediately invokes the built-in axis fitting algorithm module. This module first performs coordinate inversion on the distance values ​​of at least four measuring points in each group, calculating the local center of the outer circle of the shaft segment at the current cross-section. Then, after the main shaft completes at least one slow rotation, the system accumulates the center coordinates at multiple angles and uses the three-dimensional least squares method to fit an optimal straight line, i.e., the instantaneous rotation centerline of the shaft segment. This centerline is defined by a spatial point coordinate and a direction vector, fully describing the geometric attitude of the shaft segment under the current working condition. Similarly, the above fitting is performed on the main output shaft segment and the tail shaft segment, respectively, yielding two independent spatial straight lines. Next, the algorithm accurately calculates the shortest distance (reflecting radial offset) and the included angle (reflecting angular deviation) between these two lines in the docking area through vector operations, and merges them into a three-dimensional alignment error vector with direction and magnitude.

[0046] Based on the error vector, the system further calls the preset inverse kinematics model. The model fully considers the mechanical layout of the multi-degree-of-freedom hydraulic adjustment actuators on the main unit base and tail shaft support. Typically, there are three hydraulic cylinders arranged in a triangle. Each cylinder is connected to the base of the adjusted equipment through a ball joint. The model decomposes the overall three-dimensional pose correction requirements (including vertical lifting, lateral translation and slight tilting) into the independent extension stroke required by each hydraulic cylinder.

[0047] Once the target stroke is determined, the central processing unit sends continuously adjustable control signals to the drive control module via the analog output channel. This drives the corresponding proportional servo valves to precisely adjust the flow and pressure of the oil entering the rod and rodless chambers of each hydraulic cylinder. Simultaneously, the magnetostrictive displacement sensor integrated on each hydraulic cylinder provides high-frequency, real-time feedback on the actual position of the piston rod, forming an inner position closed loop. The central processing unit continuously compares the target value with the measured value, dynamically correcting the output signal using adaptive PID or other advanced control strategies until the deviation between the actual displacement of each cylinder and the target stroke is less than a preset tolerance (e.g., ±10μm).

[0048] However, a single adjustment is often insufficient to meet the final requirements because the hydraulic cylinder action causes a redistribution of local stress in the hull, leading to secondary minor deformations in the shafting system. Therefore, after completing one adjustment, the system immediately returns to step S1 to re-perform synchronous sampling and error calculation. By repeatedly executing the iterative cycle of "measurement, calculation, adjustment, and re-measurement," the system continuously approaches the true alignment state. When the difference in the magnitude of the three-dimensional alignment error vector calculated by two consecutive iterations is less than a preset convergence threshold (e.g., 0.01 mm), it indicates that the system has entered a stable convergence range, and the benefits of further adjustments are no longer lower than the noise level. At this point, the automatic alignment correction is considered complete.

[0049] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0050] The present invention and its embodiments have been described above. This description is not restrictive, and the accompanying drawings are only one embodiment of the present invention; the actual structure is not limited thereto. In conclusion, if those skilled in the art are inspired by this description and design similar structures and embodiments without departing from the spirit of the invention, such designs should fall within the protection scope of the present invention.

Claims

1. An automatic alignment and correction system for ship shafting, characterized in that, include: A first laser displacement sensor group is installed between the main engine output flange and the intermediate shaft; a second laser displacement sensor group is installed between the intermediate shaft and the stern shaft; a multi-degree-of-freedom hydraulic adjustment actuator is installed on the main engine base and the stern shaft support respectively; a data acquisition module is connected to the first laser displacement sensor group and the second laser displacement sensor group; a central processing unit is connected to the data acquisition module; and a drive control module is connected to the control signal output terminal of the central processing unit. The multi-degree-of-freedom hydraulic adjustment actuator includes at least three hydraulic cylinders arranged in a triangular pattern. Each hydraulic cylinder is connected to the main unit base or tail shaft support and the base of the adjusted equipment respectively through a ball joint structure. It is used to independently adjust the height and horizontal offset under the command issued by the central processing unit. The first laser displacement sensor group and the second laser displacement sensor group each include no less than four laser ranging probes evenly arranged along the circumference. The measuring optical axis of the probe points perpendicularly to the outer circular surface of the corresponding shaft segment and is fixed on a rigid mounting bracket. The rigid mounting bracket is fastened to an adjacent stationary structural member by bolts.

2. The automatic alignment and correction system for ship shafting according to claim 1, characterized in that, The rigid mounting bracket is equipped with a temperature compensation structure, including an embedded thermocouple and a metal expansion compensation piece thermally coupled thereto. One end of the metal expansion compensation piece is fixed to the bracket body, and the other end is connected to the laser ranging probe mounting base to offset the influence of bracket deformation caused by changes in ambient temperature on the measurement reference.

3. The automatic alignment and correction system for ship shafting according to claim 1, characterized in that, Each hydraulic cylinder in the multi-degree-of-freedom hydraulic adjustment actuator is equipped with a displacement feedback sensor, which is a magnetostrictive displacement sensor. Its measuring rod is coaxially fixed to the piston rod of the hydraulic cylinder, and its housing is fixed to the outer wall of the hydraulic cylinder barrel. The output signal is connected to the central processing unit in real time for closed-loop control of the extension and retraction stroke of the hydraulic cylinder.

4. The automatic alignment and correction system for ship shafting according to claim 1, characterized in that, The data acquisition module integrates a synchronous triggering unit, which is connected to the ship's main shaft speed encoder via a hard wire. When the main shaft rotates to a preset angle position, it synchronously triggers the first laser displacement sensor group and the second laser displacement sensor group to sample simultaneously, ensuring that the two groups of sensors acquire shaft center position data at the same phase angle.

5. The automatic alignment and correction system for ship shafting according to claim 1, characterized in that, The central processing unit has a built-in axis fitting algorithm module. After receiving multi-point radial distance data from the data acquisition module, the algorithm module fits the instantaneous rotation center lines of the main output shaft segment and the tail shaft segment based on the least squares method, and calculates the offset and angle between the two center lines in space to generate a three-dimensional alignment error vector.

6. The automatic alignment and correction system for ship shafting according to claim 1, characterized in that, The drive control module includes multiple proportional servo valves. The control input of each proportional servo valve is connected to the analog output channel of the central processing unit, and its pressure oil outlet is connected to the rodless chamber and rod chamber of the corresponding hydraulic cylinder, respectively. The precise fine adjustment of the hydraulic cylinder is achieved through differential control.

7. The automatic alignment and correction system for ship shafting according to claim 1, characterized in that, It also includes a safety interlock device, which includes relay contacts located in the host start-up circuit. The relay coil is controlled by the central processing unit. The relay closes only when the system detects that the shaft alignment error is less than a preset threshold, allowing the host start-up circuit to conduct.

8. The automatic alignment and correction system for ship shafting according to claim 1, characterized in that, The rigid mounting brackets of the first and second laser displacement sensor groups are equipped with adjustable pitch and yaw fine-tuning mechanisms. The fine-tuning mechanisms consist of two sets of orthogonally arranged precision lead screws. The lead screw nuts are connected to the laser ranging probe mounting base and are used to manually calibrate the perpendicularity of the optical axis of each laser probe during the initial installation phase of the system.

9. The automatic alignment and correction system for ship shafting according to claim 1, characterized in that, The central processing unit is connected to the remote monitoring terminal via an industrial Ethernet interface, and the modules within the system communicate with each other via a CAN bus. The data acquisition module, drive control module, and displacement feedback sensor are all connected as CAN bus nodes.

10. A control method for an automatic alignment and correction system for a ship shafting as described in any one of claims 1 to 9, characterized in that, Includes the following steps: Step S1: When the ship's main shaft is stationary, the first laser displacement sensor group and the second laser displacement sensor group are controlled by the synchronous triggering unit to synchronously collect the distance data from each laser probe to the outer circular surface of the corresponding shaft segment at the same circumferential angle position of the main shaft. Step S2: Transmit the collected distance data to the central processing unit, and use the axis fitting algorithm module to calculate the instantaneous rotation center coordinates and direction vectors of the main output shaft segment and the tail shaft segment respectively; Step S3: Based on the spatial relationship between the centerlines of the two shafts, calculate the three-dimensional displacement required to adjust the main engine base and tail shaft support, and convert it into the target extension stroke of each hydraulic cylinder. Step S4: The central processing unit sends a control signal to the drive control module to drive the corresponding proportional servo valve to adjust the hydraulic cylinder's action. At the same time, it reads the displacement feedback sensor signals of each hydraulic cylinder and implements closed-loop control until the deviation between the actual displacement and the target stroke is less than the set tolerance. Step S5: Repeat steps S1 to S4 until the change in the magnitude of the shaft alignment error vector calculated twice consecutively is less than the preset convergence threshold, thus completing the automatic alignment correction.

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