A multi-dimensional load composite loading mechanism applied to a shafting and a loading force correction method

Abstract

The application belongs to the technical field of mechanical loading and testing, and discloses a multi-dimensional load composite loading mechanism applied to a shaft system and a loading force correction method. The multi-dimensional load composite loading mechanism realizes non-interference composite loading of multi-dimensional force and torque through the combination of a transmission cable and a four-suspension cross composite loading frame. Meanwhile, the loading force correction method of the multi-dimensional load composite loading mechanism comprehensively considers key parameters such as a target composite load, a hydraulic cylinder output tension, a standard force sensor measured tension, a mapping matrix, a step factor and a convergence threshold, and gradually corrects the tension command of each hydraulic cylinder through closed-loop iteration, so that the actual composite load approaches the target value, and the load deviation caused by factors such as the output error of the hydraulic cylinder, the pre-tightening difference of the transmission cable and the hinged gap can be compensated. The application simplifies the conventional mechanical loading calibration method, does not need a complex mechanical decoupling mechanism, is simple to solve, has strong universality, has high correction efficiency, and has great engineering application practical value.

Description

Technical Field

[0001] This invention belongs to the field of mechanical loading and testing technology, and relates to a multi-dimensional load composite loading mechanism and a loading force correction method applied to shaft systems. Background Technology

[0002] The propulsion shafting system is the core component of power transmission in a ship. In actual operation, the propeller generates multidimensional spatial loads in complex wake fields, including axial thrust, radial force, torque, and bending moment. These loads act directly on the shafting system and are transmitted through hull bearings such as the stern bearing. Their stress characteristics significantly affect the ship's vibration and noise performance and operational reliability. To accurately simulate these conditions in a laboratory environment, scaled-down shafting tests and calibration of multidimensional force sensors on the shaft sections are required. This necessitates loading equipment capable of accurately reproducing the multidimensional composite loads generated by the propeller. However, existing shafting loading technologies and calibration devices suffer from significant technical bottlenecks in terms of the purity of mechanical transmission and the ability to decouple multidimensional forces.

[0003] Currently, shaft load simulation and sensor calibration generally adopt a mechanical jacking method combining hydraulic actuators and rigid loading heads. Wan Liyou et al.'s patent "A Machine Tool Spindle Tension and Compression Static Loading Mechanism and Method" (CN116475779B) proposes to generate tension and compression static forces between two shafts through a telescopic adjustment part. However, the rigid jacking structure has inherent defects: when the loading component contacts the measured part, it will generate lateral friction and guide stiffness constraints, resulting in "load splitting phenomenon" - part of the real load output by the actuator is absorbed by the rigid structure or the vector is changed, which ultimately distorts the effective force and causes system errors that are difficult to compensate for. Liu Xingheng et al.'s "Dynamic Loading Device for CNC Machine Tool Cutting Load" adopts a rigid orthogonal arrangement structure of actuators, focusing on the concentrated application of three-dimensional translational forces. However, this mechanism is essentially limited to the linear superposition of unidirectional forces and lacks the ability to independently apply spatial bending moments and torques. Moreover, there are serious mechanical cross-coupling and load splitting phenomena when multi-dimensional composite loading, which will generate parasitic forces or parasitic bending moments. To this end, this invention proposes a multi-dimensional load composite loading mechanism and a loading force correction method from the perspective of device design methodology. It achieves low load distribution error loading through flexible cables and multi-dimensional load composite loading through a cross loading frame, which can improve the accuracy of multi-dimensional force simulation and loading purity, and provide reliable support for high-end mechanical testing and evaluation technology. Summary of the Invention

[0004] This invention aims to overcome the shortcomings of existing technologies by proposing a multi-dimensional load composite loading mechanism and loading force correction method for shafting systems. The technical principle is as follows: multi-dimensional force composite loading without interference is achieved through the tension loading of flexible cables and their spatial orthogonal and tangential coordinated arrangement. During the simulation of ship shafting stress, the flexible cables with spherical bearings apply tension to the cross-shaped loading frame, significantly eliminating the "load splitting phenomenon" and contact stiffness constraints caused by traditional rigid jacking structures. Simultaneously, the spatial distribution of the inverted U-shaped gantry and X-axis hydraulic cylinders with the cross-shaped loading mechanism enables synchronous composite loading of force and torque. This loading mechanism can apply multi-dimensional loads independently or simultaneously according to different test conditions. Its flexible, contactless constraint loading and pure moment application design effectively reduce the cross-coupling effect between loads, improve the fidelity of force transmission, and give the loading force multi-dimensional, non-interfering, and high-precision characteristics. It provides an accurate and reliable physical calibration benchmark for complex decoupling algorithms, has reference value for the development of ship shafting load testing and calibration equipment, and has engineering application potential.

[0005] The technical solution of the present invention: A multi-dimensional load composite loading mechanism for shaft systems has the following structure: a high-rigidity reference cast iron platform 2 is fixed on the foundation; a V-shaped support bracket 12 for the drive shaft is fixedly installed on the high-rigidity reference cast iron platform 2; a marine simulated drive shaft prototype 11 is installed and supported on the V-shaped support bracket 12; a four-cantilever cross-shaped composite loading frame 13 is coaxially fitted onto the overhanging end of the marine simulated drive shaft prototype 11; each cantilever end of the four-cantilever cross-shaped composite loading frame 13 is fixedly equipped with a self-lubricating joint bearing hinge seat 14; a flexible cable-suspended inverted U-shaped gantry frame 1 is fixedly installed on the high-rigidity reference cast iron platform 2, ensuring that its two side columns are aligned with the two side cantilever arms of the four-cantilever cross-shaped composite loading frame 13; the gantry frame is top-mounted. The Z-axis hydraulic cylinder 8 is installed on the top crossbeam of the flexible cable-suspended inverted U-shaped gantry frame 1; one end of the series-type tension standard force sensor 4 is connected to the end of the piston rod of the top-mounted Z-axis hydraulic cylinder 8 of the gantry frame, and the other end is connected to the beginning of the high-flexibility Z-axis transmission cable 9; the end of the high-flexibility Z-axis transmission cable 9 is connected to the Z-axis cable special U-shaped hinge fork 15, and the Z-axis cable special U-shaped hinge fork 15 is movably hinged to the self-lubricating joint bearing hinge seat 14 of the cantilever on the four-cantilever cross-shaped composite loading frame 13 through the shear-resistant high-strength hinge pin 18, with a margin between the two; at the same time, the shear-resistant high-strength hinge pin 18 is fitted with pin axial limiting elastic snap rings 19 at both ends for limiting, realizing Z-axis force loading; the gantry frame side-mounted Y-axis hydraulic cylinder Four pressure cylinders 3 are installed on the upper and lower sides of the two columns of the flexible cable-suspended inverted U-shaped gantry frame 1, respectively. One end of the series-type tension standard force sensor 4 is connected to the piston rod end of the gantry frame side-mounted Y-axis hydraulic cylinder 3, and the other end is connected to the beginning end of the high-flexibility Y-axis transmission cable 5. The end of the high-flexibility Y-axis transmission cable 5 is fixed to the multi-directional universal U-shaped articulated fork 16. The multi-directional universal U-shaped articulated fork 16 is movably hinged to the self-lubricating joint bearing articulated seat 14 of the left cantilever, right cantilever, or lower cantilever of the four-cantilever cross-shaped composite loading frame 13 through the shear-resistant high-strength articulated pin 18, and is limited by the axial limiting elastic snap ring 19 of the pin, realizing the loading of Y-axis force and X-axis torque. The X-axis hydraulic cylinder 6 includes the X-axis left side hydraulic cylinder. The pressure cylinder and the right-side hydraulic cylinder in the X direction are respectively connected to the sliding adjustable base 10 of the hydraulic cylinders on the left and right sides; one end of the series-type tension standard force sensor 4 is connected to the end of the piston rod of the X-direction hydraulic cylinder 6, and the other end is connected to the beginning of the high-flexibility X-direction transmission cable 7; the end of the high-flexibility X-direction transmission cable 7 is fixed to the multi-directional universal U-shaped articulated fork 16, which is movably hinged to the self-lubricating joint bearing articulated seats 14 of the left and right cantilever cross-shaped composite loading frame 13 through the shear-resistant high-strength articulated pin 18, and is limited by the axial limiting elastic snap ring 19 of the pin; by changing the front and rear positions of the sliding adjustable base 10 of the hydraulic cylinders on the left and right sides, the X-direction force and Z-direction torque can be loaded; The axial direction of the simulated marine drive shaft sample 11 is taken as the X-direction. The direction from the V-shaped support fixing frame 12 of the drive shaft to the four-cantilever cross-shaped composite loading frame 13 is the positive X-direction. The direction from the left cantilever to the right cantilever of the four-cantilever cross-shaped composite loading frame 13 is the positive Y-direction. The direction perpendicular to the high-rigidity reference cast iron platform 2 and upward is the positive Z-direction.

[0006] The central hole of the four-cantilever cross-shaped composite loading frame 13 and the marine simulated drive shaft sample 11 are connected by a keyless locking sleeve 17 with a high torque keyless expansion and locking sleeve to ensure that the four-cantilever cross-shaped composite loading frame 13 does not rotate relative to each other when torque is applied.

[0007] When the top-mounted Z-axis hydraulic cylinder 8, the side-mounted Y-axis hydraulic cylinder 3, and the X-axis hydraulic cylinder 6 of the gantry are driven by the hydraulic pump to retract and pull outward, the pulling force is applied to the four-cantilever cross-shaped composite loading frame 13 through the high-flexibility Y-axis transmission cable 5 and the high-flexibility X-axis transmission cable 7, and the series-connected tension standard force sensor 4 collects the output force value in real time, realizing the multi-dimensional load composite loading of the marine simulated transmission shaft sample 11.

[0008] A loading force correction method for a multi-dimensional load composite loading mechanism applied to a shaft system, the loading force correction method being implemented based on the aforementioned multi-dimensional load composite loading mechanism; the specific steps are as follows: Step 1: Determine the key parameters of the loading mechanism; The target load applied to the marine simulated drive shaft prototype 11: In the formula: This represents the axial force expected to be applied to the marine simulated drive shaft prototype 11, with positive values ​​along the positive X-axis. This represents the desired horizontal radial force applied to the marine simulated drive shaft prototype 11, with positive values ​​along the positive Y-axis. This represents the vertical force expected to be applied to the marine simulated drive shaft prototype 11, with the positive direction along the Z-axis being positive. This represents the bending moment about the X-axis that is expected to be applied to the marine simulated drive shaft prototype 11; This represents the torque about the Z-axis that is expected to be applied to the marine simulated drive shaft prototype 11; Actual output tension vector: In the formula: This represents the actual output pulling force applied by X to the left hydraulic cylinder; This represents the actual output pulling force applied by X to the right hydraulic cylinder; This indicates the pulling force applied by the gantry side-mounted Y-axis hydraulic cylinder 3 at the upper position of the left column; This indicates the pulling force applied by the gantry side-mounted Y-axis hydraulic cylinder 3 at the lower position of the left column; This indicates the pulling force applied by the gantry side-mounted Y-axis hydraulic cylinder 3 at the upper position of the right column; This indicates the pulling force applied by the gantry side-mounted Y-axis hydraulic cylinder 3 at the lower position of the right column; This indicates the pulling force applied to the top-mounted Z-axis hydraulic cylinder 8 of the gantry frame, and p i ≥0; The measured tension vector of the series-type tension standard force sensor 4: In the formula: This indicates the tension measured by the series-type tension standard force sensor 4, which connects the hydraulic cylinders on the left side of the X direction. This indicates the tension measured by the series-type tension standard force sensor 4 connected in series with the hydraulic cylinder on the right side of X; This indicates the tension measured by the series-type tension standard force sensor 4, which is connected in series with the gantry side-mounted Y-axis hydraulic cylinder 3 at the upper position of the left column. This indicates the tension measured by the series-type tension standard force sensor 4 connected in series with the gantry side-mounted Y-axis hydraulic cylinder 3 at the lower position of the left column; This indicates the tension measured by the series-type tension standard force sensor 4 connected in series with the gantry side-mounted Y-axis hydraulic cylinder 3 at the upper position of the right column; This indicates the tension measured by the series-type tension standard force sensor 4 connected in series with the gantry side-mounted Y-axis hydraulic cylinder 3 at the lower position of the right column; This indicates the tension measured by the series-type tension standard force sensor 4 of the top-mounted Z-axis hydraulic cylinder 8 of the gantry frame, and ≥0; The mapping matrix M is a 7×5 matrix that satisfies: Define the number of iterations k and the step size factor. Convergence threshold ; Step 2: Initialize the hydraulic cylinder command; The third step is to apply the tension command and collect the measured values. Step 4: Calculate the actual composite load and load error; Step 5: Convergence judgment and tension correction.

[0009] The specific implementation process of the second step is as follows: Determine the convergence threshold Step size factor Maximum number of iterations ;make k=0, calculate the initial tension command based on the target load T. : In the formula: The Moore-Penrose pseudo-inverse matrix satisfies: .

[0010] The specific implementation process of the third step is as follows: According to the tension command of the kth iteration Drive the top-mounted Z-axis hydraulic cylinder 8, the side-mounted Y-axis hydraulic cylinder 3, and the X-axis hydraulic cylinder 6 of the gantry frame. After the tension stabilizes, read the values ​​of each series-connected tension standard force sensor 4 to obtain the measured tension vector. .

[0011] The specific implementation process of the fourth step is as follows: In the formula: This represents the actual composite load during the k-th iteration; This represents the error between the expected load and the actual composite load after the k-th iteration.

[0012] The specific implementation process of step five is as follows: like Then the iteration ends. For the final tension command, force correction begins; In the formula: These represent the errors between the expected load and the actual combined load in the X direction after the k-th iteration, the errors between the expected load and the actual combined load in the Y direction after the k-th iteration, the errors between the expected load and the actual combined load in the Z direction after the k-th iteration, the errors between the expected torque and the actual torque in the X direction after the k-th iteration, and the errors between the expected torque and the actual torque in the Z direction after the k-th iteration. This is the corrected force vector obtained after the k-th iteration; This is the tension command obtained after the k-th iteration; The top-mounted Z-axis hydraulic cylinder 8, the side-mounted Y-axis hydraulic cylinder 3, and the X-axis hydraulic cylinder 6 of the gantry all meet the following requirements: In the formula: The rated maximum pulling force for each hydraulic cylinder; This represents the required pulling force for each hydraulic cylinder after the k-th iteration; Finally, let k = k + 1, return to step 3, and repeat the above process until convergence or the maximum number of iterations is reached.

[0013] The beneficial effect of this invention is that it proposes a multi-dimensional load composite loading mechanism and a loading force correction method for shaft systems. The multi-dimensional load composite loading mechanism uses a cast iron platform and an inverted U-shaped gantry as its supporting foundation. X-axis, Y-axis, and Z-axis hydraulic cylinders are connected to a four-cantilever cross-shaped composite loading frame via standard force sensors, transmission locks, U-shaped hinged forks, and self-lubricating spherical bearing hinge seats. This allows the hydraulic cylinder output force to be transmitted to a marine simulated drive shaft sample via the transmission locks. Compared to the traditional method of directly pushing or pulling the test piece with a rigid loading head, the multi-dimensional load composite loading mechanism uses transmission locks for unidirectional tensile loading. The loading end is connected to the four-cantilever cross-shaped composite loading frame via threads, which reduces the influence of lateral friction on rigid contact surfaces, guide stiffness constraints, and assembly deviations on load transmission, thereby reducing load distribution errors during the loading process. Meanwhile, a four-cantilevered cross-shaped composite loading frame is coaxially mounted on the overhanging end of a marine simulated drive shaft prototype. Each cantilever end serves as the application position for loads in different directions. Through the cooperation of hydraulic cylinders in different directions and the effective lever arm, multidimensional force and torque can be applied in combination. By adjusting the front and rear positions of the two sets of X-axis hydraulic cylinders and the sliding adjustable base of the hydraulic cylinders, different loading conditions with axial translational force or torque around the Z-axis as the primary objective can be achieved. Therefore, this multidimensional load composite loading mechanism has advantages such as a clear loading path, well-defined structural composition, prominent flexible force transmission characteristics, and strong multi-branch composite loading capability, making it suitable for scenarios such as shaft load simulation, scaled-down shaft tests, and multidimensional force sensor calibration. Furthermore, the loading force correction method proposed in this invention can improve the consistency of load application during actual loading processes. This loading force correction method is based on the target composite load, the hydraulic cylinder output tension, the measured tension from standard force sensors, and the loading mapping matrix. First, the initial tension command is calculated using the Moore-Penrose pseudo-inverse of the target load and mapping matrix. Then, the control system drives each hydraulic cylinder to load, and the actual tension is collected by standard force sensors connected in series in each branch. Subsequently, the actual composite load is calculated based on the measured tension, compared with the target load to obtain the load error, and the hydraulic cylinder tension command is iteratively corrected according to the step size factor until the convergence threshold is met or the maximum number of iterations is reached. Compared with the method of simply relying on a theoretical static model for one-time open-loop loading, this method introduces the sensor measurement results into the tension command correction process, which can compensate for load deviations caused by factors such as hydraulic cylinder output error, flexible cable preload differences, hinge gaps, and installation alignment errors. Therefore, this invention can realize the calculation, distribution, and feedback correction of multi-branch loading forces without introducing complex mechanical decoupling mechanisms, providing a composite loading and correction scheme with a clear calculation process and easy engineering implementation for multi-dimensional load simulation of shaft systems and sensor calibration. Attached Figure Description

[0014] Figure 1 This is a schematic diagram of a multi-dimensional load composite loading mechanism applied to a shaft system. Figure 2 This is a partial schematic diagram of a cross-shaped loading mechanism in a multi-dimensional load composite loading mechanism applied to a shaft system; Figure 3 This is a partial schematic diagram of the connection between the cross-shaped loading mechanism and the flexible rope; Figure 4 This is a schematic diagram of the hydraulic cylinder arrangement for a multi-dimensional load composite loading mechanism applied to a shaft system when applying Z-axis torque loading. Figure 5 Flowchart of a multidimensional force and couple interference-free composite loading and mapping control loading method; Figure 1 Components: 1- Flexible cable-suspended inverted U-shaped gantry frame, 2- High-rigidity reference cast iron platform, 3- Gantry frame side-mounted Y-axis hydraulic cylinder, 4- Series-type tension standard force sensor, 5- High-flexibility Y-axis transmission cable, 6- X-axis hydraulic cylinder, 7- High-flexibility X-axis transmission cable, 8- Gantry frame top-mounted Z-axis hydraulic cylinder, 9- High-flexibility Z-axis transmission cable, 10- Hydraulic cylinder sliding adjustable base, 11- Marine simulated drive shaft sample, 12- Drive shaft V-type support fixing frame, 13- Four-cantilever cross-shaped composite loading frame, 14- Self-lubricating spherical bearing hinge seat, 15- Z-axis cable special U-shaped hinge fork, 16- Multi-directional universal U-shaped hinge fork, 17- High-torque keyless expansion locking sleeve, 18- Shear-resistant high-strength hinge pin, 19- Pin axial limiting elastic snap ring; Detailed Implementation

[0015] The specific embodiments of the present invention will be further described below with reference to the accompanying drawings and technical solutions.

[0016] Example The selected system parameters are: the effective lever arm of the cross-loading frame is 0.5m, and the rated pulling force of the X-axis hydraulic cylinder 6 is... =20000N, the rated pulling force of the gantry side-mounted Y-axis hydraulic cylinder 3 is =10000N, the rated pulling force of the top-mounted Z-axis hydraulic cylinder 8 of the gantry is =10000N, the standard force sensor accuracy is ±0.1%FS, the convergence threshold is the absolute value of each target component × 0.5%, and the step size factor is 0.6.

[0017] The installation steps for a multi-dimensional force composite loading mechanism applied to a shaft system are as follows: A high-rigidity reference cast iron platform 2 is fixedly installed on the foundation, serving as the overall load-bearing base. A V-shaped support bracket 12 for the drive shaft is bolted to the high-rigidity reference cast iron platform 2, and a marine simulated drive shaft prototype 11 is supported and fixed to the V-shaped support bracket 12. A four-cantilever cross-shaped composite loading frame 13 is coaxially fitted onto the overhanging end of the marine simulated drive shaft prototype 11 and locked to it via a high-torque keyless expansion locking sleeve 17, ensuring reliable transmission of loading torque. Each cantilever end of the four-cantilever cross-shaped composite loading frame 13 is equipped with a self-lubricating spherical bearing hinge seat 14, serving as the hinge loading point for the flexible cable. A flexible cable-suspended inverted U-shaped gantry frame 1 is fixedly installed on the high-rigidity reference cast iron platform 2, and its position is adjusted to ensure alignment between the two side columns and the cantilever sides of the four-cantilever cross-shaped composite loading frame 13. The top-mounted Z-axis hydraulic cylinder 8 is installed on the top crossbeam of the flexible cable-suspended inverted U-shaped gantry frame 1. The side-mounted Y-axis hydraulic cylinder 3 is installed on the two side columns of the flexible cable-suspended inverted U-shaped gantry frame 1. The X-axis hydraulic cylinder 6 is installed on the sliding adjustable base 10 of the hydraulic cylinder. The piston rod end of each hydraulic cylinder is sequentially connected to the series-type tension standard force sensor 4, the corresponding direction transmission cable and the U-shaped articulated fork, and is movably hinged to the self-lubricating joint bearing articulated seat 14 at the end of the corresponding cantilever of the four-cantilever cross-shaped composite loading frame 13 through the shear-resistant high-strength articulated pin 18. The two ends of the shear-resistant high-strength articulated pin 18 are limited by the pin axial limiting elastic retaining spring 19. After installation, the tension output by the X, Y and Z hydraulic cylinders is transmitted to the marine simulated drive shaft sample 11 via the series-type tension standard force sensor 4, the transmission cable and the four-cantilever cross-shaped composite loading frame 13. The front and rear arrangement of the sliding adjustable base 10 of the hydraulic cylinder can be adjusted to adapt to the loading conditions of X-axis force and torque around the Z-axis.

[0018] A method for correcting the loading force of a multi-dimensional load composite loading mechanism applied to a shaft system, such as... Figure 5 As shown, the steps are as follows: Step 1: Determine the key parameters of the loading mechanism; The effective lever arm of the four-cantilever cross-shaped composite loading frame 13 is: L =0.5m, the rated pulling force of the X-axis hydraulic cylinder 6 is =20000N, the rated pulling force of the gantry side-mounted Y-axis hydraulic cylinder 3 is =10000N, the rated pulling force of the top-mounted Z-axis hydraulic cylinder 8 of the gantry is =10000N, the accuracy of the series-type tension standard force sensor 4 is ±0.1%FS, and the target load simulating the ship propeller in a non-uniform wake field is... N, the actual output tension vector of each hydraulic cylinder is The measured tension vector of the series-type tension standard force sensor 4 is: , bring in L The mapping matrix after =0.5m is ; Step 2: Initialize the hydraulic cylinder command; Determine the step size factor as The maximum number of iterations is The convergence threshold is The error of each force component is not greater than The error of each torque component is no greater than When the target component is zero, the preset minimum allowable error is used as the convergence threshold for that component.

[0019] The initial tension command was calculated. Constraints are checked to ensure the initial tension command is satisfied. .

[0020] The third step is to apply the tension command and collect the measured values. The control system follows the initial tension command. Drive each hydraulic cylinder to move. After the loading stabilizes, read the values ​​of each series-type tension standard force sensor 4 to obtain the measured tension vector at the 0th iteration. ; Step 4: Calculate the actual composite load and load error; Further calculations yielded the actual composite load for the 0th iteration. and the load error at the 0th iteration , and convergence threshold The comparison is to meet the convergence requirements.

[0021] Step 5: Calculate the actual composite load and load error; The corrected force vector obtained from the 0th iteration is: The expected pulling force command of the hydraulic cylinder after the 0th iteration is ,right Perform constraint judgment To meet the requirements, Then return to step three to continue iterating.

[0022] The iterative process is as follows: First iteration: The measured tension vector using the standard force sensor is The actual composite load obtained The corresponding load error is The corrected force vector is calculated as follows: The calculated desired pulling force command of the hydraulic cylinder is as follows: To satisfy the constraints, let k =2 Returns to continue iteration.

[0023] Second iteration: The measured tension vector of the series-type tension standard force sensor 4 is... The actual composite load obtained The corresponding load error is The error satisfies the convergence threshold. The iteration ends and the final hydraulic cylinder loading command is calculated as follows: .

[0024] At this point, the calculation of the loading force correction method for the multi-dimensional force composite loading mechanism applied to the shaft system is complete.

[0025] This method proposes a force correction calculation approach that considers key parameters such as the target composite load, hydraulic cylinder output tension, measured tension from a standard force sensor, loading mapping matrix, step size factor, convergence threshold, and maximum number of iterations. This simplifies the loading process that relies solely on manual adjustment or one-time theoretical allocation. The method first calculates the initial tension command based on the Moore-Penrose pseudo-inverse of the target load and mapping matrix. Then, the control system drives the loading of each hydraulic cylinder, and the actual tension of each branch is collected by a series-type standard force sensor. Subsequently, the actual composite load is calculated based on the measured tension, compared with the target load to obtain the load error, and the hydraulic cylinder tension command is iteratively corrected according to the step size factor until the convergence threshold is met or the maximum number of iterations is reached. Compared with open-loop loading methods, this method introduces sensor feedback into the tension allocation and correction process, compensating for deviations caused by factors such as hydraulic cylinder output error, flexible cable preload differences, hinge gaps, and installation alignment errors. This provides a clear, simple, and easily applicable correction method for multi-dimensional composite load loading.

Claims

1. A multi-dimensional load composite loading mechanism applied to a shaft system, characterized in that, The structure of the multidimensional load composite loading mechanism is as follows: a high-rigidity reference cast iron platform (2) is fixed on the foundation; a V-shaped support fixing frame (12) for the drive shaft is fixedly installed on the high-rigidity reference cast iron platform (2); a marine simulated drive shaft sample (11) is installed and supported on the V-shaped support fixing frame (12); a four-cantilever cross-shaped composite loading frame (13) is coaxially fitted onto the overhanging end of the marine simulated drive shaft sample (11); each cantilever end of the four-cantilever cross-shaped composite loading frame (13) is fixedly installed with a self-lubricating joint bearing hinge seat (14); a flexible cable-suspended inverted U-shaped gantry frame (1) is fixedly installed on the high-rigidity reference cast iron platform (2), so that its two The side columns are aligned with the two cantilever arms of the four-cantilever cross-shaped composite loading frame (13); the top-mounted Z-axis hydraulic cylinder (8) of the gantry frame is installed on the top crossbeam of the flexible cable-suspended inverted U-shaped gantry frame (1); one end of the series-type tension standard force sensor (4) is connected to the end of the piston rod of the top-mounted Z-axis hydraulic cylinder (8) of the gantry frame, and the other end is connected to the beginning of the high-flexibility Z-axis transmission cable (9); the end of the high-flexibility Z-axis transmission cable (9) is connected to the Z-axis cable special U-shaped articulation fork (15), and the Z-axis cable special U-shaped articulation fork (15) is connected to the self-lubricating joint of the upper cantilever arm of the four-cantilever cross-shaped composite loading frame (13) through the shear-resistant high-strength articulation pin (18). The bearing hinge seat (14) is movably hinged, and there is a margin between the two; at the same time, the two ends of the shear-resistant high-strength hinge pin (18) are fitted with pin axial limiting elastic snap rings (19) for limiting, so as to realize Z-direction force loading; there are four gantry side-mounted Y-direction hydraulic cylinders (3), which are respectively installed on the upper and lower sides of the two columns of the flexible cable suspension inverted U-shaped gantry (1); one end of the series-type tension standard force sensor (4) is connected to the end of the piston rod of the gantry side-mounted Y-direction hydraulic cylinder (3), and the other end is connected to the beginning of the high-flexibility Y-direction transmission cable (5); the end of the high-flexibility Y-direction transmission cable (5) is fixed to the multi-directional universal U-shaped hinge fork (16). The multi-directional universal U-shaped articulated fork (16) is movably articulated with the self-lubricating joint bearing articulation seat (14) of the left cantilever, right cantilever or lower cantilever of the four cantilever cross-shaped composite loading frame (13) through the shear-resistant high-strength articulated pin (18), and is limited by the pin axial limiting elastic snap ring (19) to realize the loading of Y-direction force and X-direction torque; the X-direction hydraulic cylinder (6) includes an X-direction left hydraulic cylinder and an X-direction right hydraulic cylinder, which are respectively connected to the sliding adjustable base (10) of the hydraulic cylinder on the left and right sides; one end of the series-type tension standard force sensor (4) is connected to the end of the piston rod of the X-direction hydraulic cylinder (6), and the other end is connected to the beginning of the high-flexibility X-direction transmission cable (7);The end of the high-flexibility X-direction transmission cable (7) is fixed to the multi-directional universal U-shaped articulated fork (16). The multi-directional universal U-shaped articulated fork (16) is movably articulated with the self-lubricating joint bearing articulated seats (14) of the left and right cantilever cross-shaped composite loading frame (13) through the shear-resistant high-strength articulated pin (18), and is limited by the axial limit elastic snap ring (19) of the pin. The X-direction force and Z-direction torque are loaded by changing the front and rear positions of the hydraulic cylinder sliding adjustable base (10) on the left and right sides. The axial direction of the simulated marine drive shaft sample (11) is the X direction. The direction from the V-shaped support fixing frame (12) of the drive shaft to the four-cantilever cross-shaped composite loading frame (13) is the positive X direction. The direction from the left cantilever to the right cantilever of the four-cantilever cross-shaped composite loading frame (13) is the positive Y direction. The direction perpendicular to the high-rigidity reference cast iron platform (2) is the positive Z direction.

2. The multidimensional load composite loading mechanism applied to a shaft system according to claim 1, characterized in that, The center hole of the four-cantilever cross-shaped composite loading frame (13) and the marine simulated drive shaft sample (11) are connected by a keyless locking sleeve (17) with a high torque keyless expansion and locking sleeve to ensure that the four-cantilever cross-shaped composite loading frame (13) does not rotate relative to each other when torque is applied.

3. The multidimensional load composite loading mechanism applied to a shaft system according to claim 2, characterized in that, When the top-mounted Z-axis hydraulic cylinder (8), the side-mounted Y-axis hydraulic cylinder (3), and the X-axis hydraulic cylinder (6) of the gantry are driven by the hydraulic pump to retract and pull outward, the tension is applied to the four-cantilever cross-shaped composite loading frame (13) through the high-flexibility Y-axis transmission cable (5) and the high-flexibility X-axis transmission cable (7), and the series-connected tension standard force sensor (4) collects the output force value in real time, so as to realize the multi-dimensional load composite loading of the marine simulated transmission shaft sample (11).

4. A method for correcting the loading force of a multi-dimensional load composite loading mechanism applied to a shaft system, characterized in that, This loading force correction method is implemented based on the multi-dimensional load composite loading mechanism described in any one of claims 1-3; the specific steps are as follows: Step 1: Determine the key parameters of the loading mechanism; The target load applied to the marine simulated drive shaft prototype (11): In the formula: This represents the axial force expected to be applied to the marine simulated drive shaft sample (11), with positive values ​​along the positive X-axis. This represents the horizontal radial force expected to be applied to the marine simulated drive shaft sample (11), with positive values ​​along the positive Y-axis. The vertical force expected to be applied to the marine simulated drive shaft sample (11) is positive along the positive Z-axis. This represents the bending moment about the X-axis that is expected to be applied to the marine simulated drive shaft sample (11); This represents the torque about the Z-axis that is expected to be applied to the marine simulated drive shaft sample (11); Actual output tension vector: In the formula: This represents the actual output pulling force applied by X to the left hydraulic cylinder; This represents the actual output pulling force applied by X to the right hydraulic cylinder; This indicates the pulling force applied by the gantry side-mounted Y-axis hydraulic cylinder (3) at the upper position of the left column; This indicates the pulling force applied by the gantry side-mounted Y-axis hydraulic cylinder (3) at the lower position of the left column; This indicates the pulling force applied by the gantry side-mounted Y-axis hydraulic cylinder (3) at the upper position of the right column; This indicates the pulling force applied by the gantry side-mounted Y-axis hydraulic cylinder (3) at the lower position of the right column; This indicates the pulling force applied by the top-mounted Z-axis hydraulic cylinder (8) of the gantry frame, and p i ≥0; The measured tension vector of the series-type tension standard force sensor (4): In the formula: This indicates the tension measured by the series-type tension standard force sensor (4) connected in series with the hydraulic cylinders on the left side of X; This indicates the tension measured by the series-type tension standard force sensor (4) connected in series with the hydraulic cylinder on the right side of X; The tension is measured by the series-type tension standard force sensor (4) connected in series with the gantry side-mounted Y-axis hydraulic cylinder (3) at the upper position of the left column; The tension measured by the series-type tension standard force sensor (4) connected in series with the gantry side-mounted Y-axis hydraulic cylinder (3) at the lower position of the left column; The tension is measured by the series-type tension standard force sensor (4) connected in series with the gantry side-mounted Y-axis hydraulic cylinder (3) at the upper position of the right column; The tension is measured by the series-type tension standard force sensor (4) connected in series with the gantry side-mounted Y-axis hydraulic cylinder (3) at the lower position of the right column; The tensile force measured by the series-type tension standard force sensor (4) of the top-mounted Z-axis hydraulic cylinder (8) of the gantry is indicated, and ≥0; The mapping matrix M is a 7×5 matrix that satisfies: Define the number of iterations k and the step size factor. Convergence threshold ; Step 2: Initialize the hydraulic cylinder command; The third step is to apply the tension command and collect the measured values. Step 4: Calculate the actual composite load and load error; Step 5: Convergence judgment and tension correction.

5. The loading force correction method for a multi-dimensional load composite loading mechanism applied to a shaft system according to claim 4, characterized in that, The specific implementation process of the second step is as follows: Determine the convergence threshold Step size factor Maximum number of iterations ; make k =0, calculate the initial tension command based on the target load T. : In the formula: The Moore-Penrose pseudo-inverse matrix satisfies: .

6. The loading force correction method for a multi-dimensional load composite loading mechanism applied to a shaft system according to claim 5, characterized in that, The specific implementation process of the third step is as follows: According to the tension command of the kth iteration Drive the top-mounted Z-axis hydraulic cylinder (8), the side-mounted Y-axis hydraulic cylinder (3), and the X-axis hydraulic cylinder (6) of the gantry frame. After the tension stabilizes, read the values ​​of each series-connected tension standard force sensor (4) to obtain the measured tension vector. .

7. The loading force correction method for a multi-dimensional load composite loading mechanism applied to a shaft system according to claim 6, characterized in that, The specific implementation process of the fourth step is as follows: In the formula: This represents the actual composite load during the k-th iteration; This represents the error between the expected load and the actual composite load after the k-th iteration.

8. The loading force correction method for a multi-dimensional load composite loading mechanism applied to a shaft system according to claim 7, characterized in that, The specific implementation process of step five is as follows: like Then the iteration ends. For the final tension command, force correction begins; In the formula: These represent the errors between the expected load and the actual combined load in the X direction after the k-th iteration, the errors between the expected load and the actual combined load in the Y direction after the k-th iteration, the errors between the expected load and the actual combined load in the Z direction after the k-th iteration, the errors between the expected torque and the actual torque in the X direction after the k-th iteration, and the errors between the expected torque and the actual torque in the Z direction after the k-th iteration. This is the corrected force vector obtained after the k-th iteration; This is the tension command obtained after the k-th iteration; The top-mounted Z-axis hydraulic cylinder (8), the side-mounted Y-axis hydraulic cylinder (3), and the X-axis hydraulic cylinder (6) of the gantry all meet the following requirements: In the formula: The rated maximum pulling force for each hydraulic cylinder; This represents the required pulling force for each hydraulic cylinder after the k-th iteration; Finally, let k = k + 1, return to step 3, and repeat the above process until convergence or the maximum number of iterations is reached.

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