A space pendulum angle measurement system, method and device for a suspended low gravity simulation

Abstract

The present application relates to a kind of space swing angle measurement system, method and device of suspension low gravity simulation, belong to space swing angle measurement technical field.The system includes: suspension cable, and is connected with the object to be tested;Center measuring head, for clamping suspension cable;Sliding assembly, including slider connecting plate and two groups of orthogonal arrangement slider, center measuring head is set on two groups of slider by slider connecting plate, so that center measuring head freely slides in X-Y plane;Measuring module is connected with slider, for real-time measurement center measuring head in X direction, Y direction linear displacement amount;Control module is connected with measuring module, for calculating the inclination angle of suspension cable in X direction, Y direction according to linear displacement amount and real-time geometric structure parameter.The present application improves the attitude measurement precision in suspension low gravity simulation, improves real-time response performance, while realizing cost control optimization, and enhances environmental adaptability.

Description

Technical Field

[0001] This invention relates to the field of spatial pendulum angle measurement technology, and in particular to a suspended low-gravity simulation spatial pendulum angle measurement system, method and apparatus. Background Technology

[0002] In the aerospace field, complex systems such as spacecraft, space robots, lunar or Mars probes, and extravehicular activity units (EVAs) for astronauts all need to operate in the low-gravity or microgravity environment of space. The reliability of these systems directly affects the success or failure of the mission; therefore, high-precision functional and performance tests must be conducted on the ground before launch. Among various testing methods, suspended low-gravity simulation systems have become a core technology for ground testing due to their large workspace, controllable cost, and ability to flexibly simulate various gravity levels.

[0003] However, with the increasing complexity of space missions and the rising demands for simulation fidelity and dynamic performance, traditional suspension technology has revealed key bottlenecks, particularly in the insufficient accuracy of attitude measurement and coupling interference under multi-degree-of-freedom motion. Specifically, spacecraft often exhibit six degrees of freedom motion (three-dimensional translation and three-dimensional rotation), and traditional systems can only achieve single or two-dimensional force compensation, making it difficult to accurately capture attitude changes of the test object. When an object (such as a space robotic arm or probe) pitches, yaws, or rolls, the relative position and angle between the suspension cable and the center of mass change drastically, introducing unexpected parasitic torques that interfere with natural motion and distort test data. Traditional solutions that use encoders mounted at remote suspension points are unable to accurately capture the cable swing angle in real time due to transmission errors, mechanical backlash, and insufficient resolution, making it difficult to effectively compensate for parasitic torques.

[0004] To address the challenges of attitude measurement, parasitic torque compensation, and dynamic response in suspended low-gravity simulations, three main technical directions have emerged. The first is based on rotary encoders or potentiometers. This approach involves mounting encoders or potentiometers on the rotating shaft of a gimbal or similar structure at the suspension point, indirectly calculating the suspension cable's attitude by reading angle values. However, this approach has significant drawbacks: First, the accuracy and resolution of existing measuring devices are limited, resulting in large errors with minute angle changes. Second, there are mechanical and physical limitations. Machining and assembly processes inevitably introduce errors, and backlash in the transmission mechanism leads to a nonlinear hysteresis between measured and true values. Specifically, when the cable sways slightly, the sensor may fail to read data due to gear backlash, creating a dead zone—a problem particularly pronounced during dynamic processes. Furthermore, achieving multi-degree-of-freedom measurements requires complex multi-axis nested gimbals, resulting in a large system size and weight. The second type is based on external vision measurement systems. The principle involves deploying multiple high-speed infrared cameras (such as Vicon and OptiTrack) in a laboratory, while simultaneously attaching reflective markers to key locations on the object under test and the suspension rope. Using triangulation principles, the three-dimensional coordinates of the markers are calculated, thereby reconstructing the object's six-degree-of-freedom pose. However, this approach also has significant drawbacks: firstly, it is costly, with high expenses for equipment purchase, deployment, and subsequent maintenance; secondly, it requires a harsh environment, needing to operate in a dark room without obstructions, and the workspace is relatively limited, making it unsuitable for large-scale mobile testing; and thirdly, its real-time performance is poor, with delays in image processing and data transmission, making the data difficult to use for real-time closed-loop control. In suspended low-gravity simulations, if the sensors react slowly, motor compensation will be delayed, leading to system oscillation or simulation distortion. The third type is based on inertial measurement units (IMUs). The principle is to install an IMU module containing accelerometers and gyroscopes on the object being measured and obtain the object's attitude angle by integrating angular velocity. However, it has two major drawbacks: First, the gyroscope has an integration drift problem, and the error will accumulate over time, resulting in unreliable measurement accuracy in the long term. Second, the IMU measures the object's own attitude, rather than the angle between the suspension rope and the plumb line, so it cannot accurately calculate the parasitic torque introduced by the rope's tilt.

[0005] In summary, existing solutions all have insurmountable bottlenecks and cannot simultaneously meet the requirements of attitude measurement accuracy, real-time performance, cost control, and environmental adaptability. New technical solutions are urgently needed to solve key problems, improve the fidelity and dynamic performance of ground low-gravity simulations, and ensure the effectiveness of aerospace equipment testing. Summary of the Invention

[0006] Therefore, the technical problem to be solved by the present invention is to overcome the shortcomings of existing technologies such as low accuracy, large mechanical error and complex multi-degree-of-freedom measurement structure of rotary encoder or potentiometer solutions; high cost, strict environmental requirements and poor real-time performance of external vision systems, which are difficult to adapt to closed-loop control; and the problems of unreliable long-term accuracy due to integral drift of IMU solutions and difficulty in calculating parasitic torque due to deviation of the measured object.

[0007] In a first aspect, to solve the above-mentioned technical problems, the present invention provides a suspended low-gravity simulation spatial pendulum angle measurement system, comprising:

[0008] The suspension cable (6) is connected to the object being tested (9);

[0009] A central measuring head is used to clamp the suspension cable (6); the central measuring head includes an upper pulley cable fixing mechanism (16), a self-aligning bearing universal joint (20), and a lower pulley cable fixing mechanism (23).

[0010] The sliding assembly includes a slider connecting plate (21) and two sets of orthogonally arranged sliders (22). The self-aligning bearing universal joint (20) is mounted on the two sets of sliders (22) through the slider connecting plate (21), allowing the central measuring head to slide freely in the XY plane. The slider connecting plate (21) is provided with a through hole. The self-aligning bearing universal joint (20) passes through the through hole and is connected to the upper pulley rope fixing mechanism (16) and the lower pulley rope fixing mechanism (23) located on both sides of the slider connecting plate (21). When the test object (9) moves, the self-aligning bearing universal joint (20) pushes the slider (22) to move, decomposing and converting the spatial rotational motion of the suspension cable (6) into the linear displacement of the slider (22) in the XY plane.

[0011] The measurement module includes an X-axis grating ruler (18) and a Y-axis grating ruler (19). The X-axis grating ruler (18) and the Y-axis grating ruler (19) are respectively set on two sets of orthogonally arranged sliders (22) for real-time measurement of the linear displacement to obtain the linear displacement of the central measuring head in the X and Y directions.

[0012] The control module is connected to the measurement module and is used to acquire the displacement compensation amount of the test object (9) in the Z-axis direction in real time, obtain the real-time geometric structure parameters based on the displacement compensation amount, and calculate the tilt angle of the suspension cable (6) in the X and Y directions based on the linear displacement amount and the real-time geometric structure parameters.

[0013] In one embodiment of the present invention, a rope tension sensor (7) and a universal joint (8) are also included. One end of the rope tension sensor (7) is connected to the suspension cable (6), and the other end is connected to the universal joint (8). The universal joint (8) is connected to the object under test (9).

[0014] In one embodiment of the present invention, the universal joint (8) has a stacked cross structure.

[0015] In one embodiment of the present invention, a multi-axis motion control module and a drive module are also included. The multi-axis motion control module includes an X-axis ball screw drive (10); the drive module includes a Y-axis servo motor (11); the X-axis ball screw drive (10) is connected to the Y-axis servo motor (11).

[0016] In one embodiment of the present invention, a steel cable buckle (14) and a z-axis connecting plate (15) are also included. The steel cable buckle (14) is disposed on the surface of the z-axis connecting plate (15). The steel cable buckle (14) and the z-axis connecting plate (15) are provided with coaxial through holes. The suspension cable (6) passes through the coaxial through holes and enters the central measuring head.

[0017] Secondly, to solve the above-mentioned technical problems, the present invention provides a method for measuring the spatial pendulum angle of a suspended low-gravity simulation, which is implemented using the aforementioned suspended low-gravity simulation spatial pendulum angle measurement system, including:

[0018] S1. The test object (9) moves on the horizontal plane and pulls the suspension cable (6) to produce an inclination. The suspension cable (6) drives the central measuring head to move.

[0019] S2. The central measuring head slides on two sets of orthogonally arranged sliders (22) through the slider connecting plate (21), decoupling the tilting motion of the suspension cable (6) into linear motion in the XY plane;

[0020] S3. Real-time measurement of the linear displacement in the X and Y directions when the central measuring head performs linear motion;

[0021] S4. Real-time acquisition of the displacement compensation amount of the tested object (9) in the Z-axis direction, and real-time geometric parameters based on the displacement compensation amount; and calculation of the spatial swing angle of the suspension cable (6) based on the linear displacement amount and the real-time geometric parameters.

[0022] In one embodiment of the present invention, the method for calculating the spatial swing angle of the suspension cable (6) based on the linear displacement and the real-time geometric parameters in step S4 is as follows:

[0023] The linear displacement includes X-axis displacement and Y-axis displacement; the spatial swing angle of the suspension cable (6) is calculated in reverse based on the X-axis displacement, the Y-axis displacement, and the real-time geometric parameters; wherein the spatial swing angle includes the tilt angle in the X-axis direction and the tilt angle in the Y-axis direction; the calculation expression for the tilt angle in the X-axis direction is:

[0024] ;

[0025] The expression for calculating the tilt angle along the Y-axis is:

[0026] ;

[0027] in, This represents the displacement along the X-axis. Indicates the displacement along the Y-axis. This represents the real-time geometric parameters.

[0028] In one embodiment of the present invention, the expression for the real-time geometric structure parameters is:

[0029] ;

[0030] in, Represents real-time geometric parameters. Indicates the initial vertical distance. This indicates the real-time displacement compensation amount along the Z-axis.

[0031] Thirdly, in order to solve the above-mentioned technical problems, the present invention provides a suspended low gravity simulation device, including the above-mentioned suspended low gravity simulation spatial swing angle measurement system.

[0032] Compared with the prior art, the above-described technical solution of the present invention has the following advantages:

[0033] (1) The suspended low-gravity simulation spatial pendulum angle measurement system, method and device of the present invention achieves high-precision measurement of spatial pendulum angle by combining the self-aligning bearing universal joint and orthogonal slider with grating ruler detection and algorithm calculation. The self-aligning bearing universal joint has the dual characteristics of self-alignment and universality, which allows the cable to rotate and tilt freely in space, automatically matching the posture changes of the measured object. From the structural level, it avoids the mechanism jamming and wear problems caused by cable tilting, ensuring the continuous and stable measurement process. At the same time, it keeps the cable in a natural stress state, reducing the measurement error and component wear caused by uneven stress. Meanwhile, the self-aligning bearing universal joint can accurately decompose the spatial rotational oscillation of the cable and convert it into a two-dimensional linear displacement of the slider in the XY plane, establishing a one-to-one correspondence between spatial angle changes and planar linear displacement. This avoids the complexity of directly measuring spatial motion. Combined with real-time, high-precision acquisition of displacement by X-axis and Y-axis grating rulers, it provides a precise data foundation for subsequent angle calculation. Furthermore, by combining real-time geometric parameters and inverse trigonometric function calculation logic, it further realizes the quantitative output of spatial swing angles, significantly improving the accuracy and repeatability of measurement results. The calculation model based on real-time geometric parameters is also adjustable. By modifying the values ​​of the real-time geometric parameters, it can adapt to the spatial swing angle measurement needs of different ranges and installation scenarios without significant modifications to the mechanical structure, improving the system's versatility. Simultaneously, the linear displacement data and angle calculation results can be directly connected to the digital control system, facilitating real-time transmission, storage, and analysis of measurement data.

[0034] (2) The present invention allows the central measuring head to slide freely in the XY plane without being limited by the travel distance, thus meeting the requirement for the test object to move over a wide range in the horizontal plane. The mechanical structure of the sliding component is highly responsive, and combined with the real-time data acquisition capability of the measurement module, it can accurately track the dynamic tilt changes of the cable, adapting to the rapid and complex motion test scenarios of the test object in low gravity simulation.

[0035] (3) The system structure described in this invention is simple and reliable, which helps to reduce application costs. The mechanical structure avoids complex nested gimbals or transmission mechanisms, making processing and assembly easier and maintenance more convenient. Compared with high-precision vision measurement systems, this system does not require high equipment purchase and environmental modification costs, achieving cost control while ensuring measurement performance, and is easy to popularize and apply in various laboratory scenarios.

[0036] (4) This invention can receive displacement data from the measurement module in real time and quickly calculate the tilt angle with low output delay, meeting the high bandwidth requirements of the suspended low gravity simulation device for closed-loop control such as real-time compensation of parasitic torque and active following of the XY axis moving mechanism. This effectively improves the dynamic performance and simulation fidelity of the simulation device and avoids control oscillation or instability caused by angle measurement lag. Attached Figure Description

[0037] To make the content of this invention easier to understand, the invention will be further described in detail below with reference to specific embodiments and accompanying drawings.

[0038] Figure 1 This is a schematic diagram of a suspended low-gravity simulation spatial pendulum angle measurement system according to a preferred embodiment of the present invention;

[0039] Figure 2 This is a front view of a suspended low-gravity simulation spatial pendulum angle measurement system according to a preferred embodiment of the present invention;

[0040] Figure 3 This is a side view of a suspended low-gravity simulation spatial pendulum angle measurement system according to a preferred embodiment of the present invention;

[0041] Figure 4 This is a top view of a suspended low-gravity simulation spatial pendulum angle measurement system according to a preferred embodiment of the present invention;

[0042] Figure 5(a) is a front view of the rope angle measuring module structure in a preferred embodiment of the present invention;

[0043] Figure 5(b) is a side view of the rope angle measurement module structure in a preferred embodiment of the present invention;

[0044] Figure 6 This is a schematic diagram of the posture sensing and force feedback module in a preferred embodiment of the present invention;

[0045] Figure 7 This is a flowchart of a spatial pendulum angle measurement method for a suspended low-gravity simulation according to a preferred embodiment of the present invention.

[0046] Explanation of reference numerals in the accompanying drawings: 1. Fixed frame; 2. Y-axis ball screw drive; 3. Z-axis constant force unloading mechanism; 4. Y-axis tank chain; 5. Rope angle measurement module; 6. Suspension cable; 7. Rope tension sensor; 8. Universal joint; 9. Test object; 10. X-axis ball screw drive; 11. Y-axis servo motor; 12. X-axis first servo motor; 13. X-axis second servo motor; 14. Steel cable clip; 15. Z-axis connecting plate; 16. Upper pulley rope fixing mechanism; 17. Support column; 18. X-axis grating ruler; 19. Y-axis grating ruler; 20. Self-aligning bearing universal joint; 21. Slider connecting plate; 22. Slider; 23. Lower pulley rope fixing mechanism; 24. Base plate. Detailed Implementation

[0047] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, so that those skilled in the art can better understand and implement the present invention. However, the embodiments described are not intended to limit the present invention.

[0048] Example 1:

[0049] Reference Figure 1 As shown in Figure 5(b), an embodiment of the present invention provides a suspended low-gravity simulation space pendulum angle measurement system for planetary surface simulation missions. The system includes:

[0050] Suspension cable 6 is connected to the object being tested 9;

[0051] The center measuring head is used to clamp the suspension cable 6; the center measuring head includes an upper pulley cable fixing mechanism 16, a self-aligning bearing universal joint 20 and a lower pulley cable fixing mechanism 23.

[0052] The sliding assembly includes a slider connecting plate 21 and two sets of orthogonally arranged sliders 22. A self-aligning bearing universal joint 20 is mounted on the two sets of sliders 22 through the slider connecting plate 21, allowing the central measuring head to slide freely in the XY plane. The slider connecting plate 21 is provided with a through hole. The self-aligning bearing universal joint 20 passes through the through hole and is connected to the upper pulley rope fixing mechanism 16 and the lower pulley rope fixing mechanism 23 located on both sides of the slider connecting plate 21, respectively. When the test object 9 moves, the self-aligning bearing universal joint 20 pushes the slider 22 to move, decomposing and converting the spatial rotational motion of the suspension cable 6 into linear displacement of the slider 22 in the XY plane.

[0053] The measurement module includes an X-axis grating ruler 18 and a Y-axis grating ruler 19. The X-axis grating ruler 18 and the Y-axis grating ruler 19 are respectively set on two sets of orthogonally arranged sliders 22, which are used to measure linear displacement in real time and obtain the linear displacement of the central measuring head in the X and Y directions.

[0054] The control module, connected to the measurement module, is used to acquire the displacement compensation amount of the tested object 9 in the Z-axis direction in real time, obtain the real-time geometric structure parameters based on the displacement compensation amount, and calculate the tilt angle of the suspension cable 6 in the X and Y directions based on the linear displacement amount and the real-time geometric structure parameters.

[0055] The suspended low-gravity simulation spatial tilt angle measurement system described in this invention can achieve high-precision tilt angle measurement. Its measurement module can directly capture the linear displacement of the central measuring head in the XY plane, effectively avoiding the mechanical transmission errors of traditional encoders, environmental interference of visual measurement, and integration drift problems of inertial measurement units (IMUs). It can combine geometric parameters and trigonometric functions for inverse calculation, and can accurately output the tilt angle of the suspension cable in two directions, providing high-fidelity data support for core control such as parasitic torque compensation. In the efficient decoupling of the tilting motion of the suspension cable, a sliding assembly consisting of two sets of orthogonally arranged sliders and slider connecting plates can decouple the spatial tilting motion of the cable into linear motion in the XY plane, eliminating coupling interference between multi-degree-of-freedom motions. This ensures that the measurement module only captures displacement signals directly related to the tilt of the suspension cable, simplifying data processing logic and improving the timeliness of measurement response. Meanwhile, this system is adaptable to a wide range of dynamic motion scenarios. The central measuring head can slide freely in the XY plane without any travel limitations, meeting the needs of the tested object for a wide range of movement in the horizontal plane. Furthermore, the mechanical structure of the sliding component is highly responsive, and combined with the real-time data acquisition capabilities of the measurement module, it can accurately track the dynamic tilt changes of the cable, adapting to the rapid and complex motion testing scenarios of the tested object in low-gravity simulations. In addition, this system has a simple and reliable structure that reduces application costs. The mechanical structure has no complex nested gimbals or transmission mechanisms, making it easy to manufacture, assemble, and maintain. Compared to high-precision vision measurement systems, it eliminates the need for expensive equipment purchases and environmental modifications, achieving cost control while ensuring measurement performance, facilitating widespread application in various laboratory scenarios. The system described in this embodiment can also provide stable support for the closed-loop control of the simulation device. The control module can receive displacement data from the measurement module in real time and quickly calculate the tilt angle. The output delay is low, which can meet the high bandwidth requirements of the suspended low gravity simulation device for closed-loop control such as real-time compensation of parasitic torque and active following of the XY axis moving mechanism. This effectively improves the dynamic performance and simulation fidelity of the system and avoids control oscillation or instability caused by angle measurement lag.

[0056] In this embodiment of the invention, the central measuring head is mounted on the orthogonally arranged slider 22 via a self-aligning bearing universal joint 20. This enables the spatial rotational motion of the suspension cable 6 to be decoupled into linear motion in the XY plane. The core mechanism of this motion conversion is as follows: when the measured object 9 moves, causing the suspension cable 6 to tilt, the self-aligning bearing universal joint 20, through its own self-aligning and universal functions, allows the suspension cable 6 to rotate and tilt freely in space, automatically adjusting its direction to match the posture of the measured object 9. This avoids the mechanism (including the upper pulley rope fixing mechanism) from being decoupled. The locking mechanism 16 and the sliding pulley rope fixing mechanism 23) ensure that the suspension cable 6 is always under natural stress. At the same time, the self-aligning bearing universal joint 20 forcibly decomposes the spatial rotational swing of the suspension cable 6 and converts it into a two-dimensional linear displacement of the slider 22 in the XY plane. That is, any tiny tilt angle of the suspension cable 6 can be precisely driven by the self-aligning bearing universal joint 20 to produce a corresponding displacement distance in the horizontal plane. The X-axis grating ruler 18 and Y-axis grating ruler 19, which are set along the movement path of the slider 22, can measure the above two-dimensional linear displacement. Real-time measurements are performed; ultimately, the system calculates the spatial swing angle of the cable based on the precise linear displacement acquired by the grating ruler and combined with real-time geometric parameters through inverse trigonometric functions.

[0057] Specifically, the central measuring head, sliding assembly, and measuring module are all included in the rope angle measuring module 5, as shown in Figures 5(a) and 5(b). Figure 5(a) shows a front view of the rope angle measuring module 5, and Figure 5(b) shows an axonometric view of the rope angle measuring module 5.

[0058] Specifically, referring to FIG5(b), the measurement module includes an X-axis grating ruler 18 and a Y-axis grating ruler 19, which are respectively mounted on two sets of orthogonally arranged sliders 22.

[0059] Specifically, the central measuring head includes an upper pulley rope fixing mechanism 16, a lower pulley rope fixing mechanism 23, and a self-aligning bearing universal joint 20. The upper pulley rope fixing mechanism 16 is connected to the self-aligning bearing universal joint 20, and the self-aligning bearing universal joint 20 is connected to the lower pulley rope fixing mechanism 23. The suspension cable 6 passes sequentially through the upper pulley rope fixing mechanism 16, the self-aligning bearing universal joint 20, and the lower pulley rope fixing mechanism 23.

[0060] Furthermore, the function of the self-aligning bearing universal joint 20 is to automatically adjust the direction of the suspension cable 6 during the process of the test object 9 changing direction or making other complex movements, so as to ensure that the suspension cable 6 always accurately matches the posture of the test object 9, thereby precisely driving the orthogonal grating ruler (i.e., X-axis grating ruler 18 and Y-axis grating ruler 19) to move accordingly.

[0061] Furthermore, the upper pulley rope fixing mechanism 16 and the lower pulley rope fixing mechanism 23 are key designs for achieving high measurement accuracy. In this embodiment, both the upper pulley rope fixing mechanism 16 and the lower pulley rope fixing mechanism 23 include four pairs of orthogonally arranged pre-tensioning guide wheels, thereby achieving the dual functions of rigid constraint and vibration suppression. In terms of rigid constraint, the four pairs of guide wheels elastically press the suspension cable 6 from the X, -X, Y, and -Y directions, allowing it to be freely extended and retracted with low friction in the Z-axis (vertical direction). When the suspension cable 6 experiences lateral displacement in the XY plane, these displacements are rigidly captured and transmitted to the connected slider 22 and grating rulers (including the X-axis grating ruler 18 and the Y-axis grating ruler 19) without delay. In terms of vibration suppression, the pre-tensioning guide wheels are made of high-damping polyurethane material with a damping coefficient of approximately 0.01. When the dynamic movement of the measured object 9 causes the suspension cable 6 to generate high-frequency lateral vibration, the vibration energy is rapidly absorbed and dissipated by the high internal damping characteristics of this material.

[0062] In this embodiment of the invention, the upper pulley rope fixing mechanism 16 and the lower pulley rope fixing mechanism 23 work together to form a short, highly damped measurement reference section on the suspension cable 6. This design ensures that the grating ruler always measures the true lateral displacement of this reference section, and high-frequency vibrations are effectively suppressed. Therefore, the accuracy and stability of the measurement signal are guaranteed.

[0063] Further, referring to Figures 5(a) and 5(b), the specific connection structure between the central measuring head and the sliding assembly is as follows: a through hole is opened on the slider connecting plate 21, the inner diameter of which is adapted to the outer diameter of the self-aligning bearing universal joint 20. After the self-aligning bearing universal joint 20 passes through the through hole, it is connected to the lower pulley rope fixing mechanism 23 located on the other side of the slider connecting plate 21. This structure also ensures that the upper pulley rope fixing mechanism 16 and the lower pulley rope fixing mechanism 23 are located on both sides of the slider connecting plate 21, realizing the orderly arrangement of components. Each set of sliders 22 includes a first slider and a second slider, which are symmetrically installed at both ends of the slider connecting plate 21 and form a stable connection with the slider connecting plate 21. When the first slider and the second slider move synchronously in a preset direction, the connecting structure will drive the slider connecting plate 21 to translate accordingly, thereby driving the central measuring head mounted on the slider connecting plate 21 to achieve precise movement in the corresponding direction, ensuring the synchronicity and stability of position adjustment during the measurement process. The slider 22 is disposed on the upper surface of the base plate 24 and the lower surface of the slider connecting plate 21. The two sets of sliders are orthogonally arranged along the X and Y directions, forming a stacked orthogonal sliding structure. In addition, the first set of sliders is allowed to move along the X-axis, and the second set of sliders is allowed to move along the Y-axis, thereby achieving motion decoupling and constraining the central measuring head to move linearly only in the XY plane.

[0064] Specifically, refer to Figure 6As shown, the spatial swing angle measurement system of this embodiment of the invention also includes an attitude perception and force feedback module, which includes a rope tension sensor 7 and a universal joint 8. One end of the rope tension sensor 7 is connected to the suspension cable 6, and the other end is connected to the universal joint 8, which is connected to the test object 9. In this embodiment of the invention, the rope tension sensor 7 is connected in series in the suspension cable 6, and the cable force can be stabilized at a set value through a closed loop using a high-speed motor or servo control. At the same time, the multi-axis motion control module adopts a bridge-type trolley structure, and the trolley actively follows the test object 9 in the XY direction to ensure that the suspension cable 6 remains basically vertical. This design effectively reduces lateral force and sway, thereby ensuring that the constant unloading force in the vertical direction maintains high fidelity.

[0065] Furthermore, to achieve a realistic low-gravity simulation of the tested object 9, the universal joint connecting it needs to provide three rotational degrees of freedom (pitch, roll, and yaw) to ensure its attitude is unrestricted. However, the design of this universal joint faces two key problems. First, the mass and moment of inertia of the universal joint itself become parasitic loads, directly affecting the fidelity of the simulation. Therefore, the universal joint needs to adopt a lightweight design. Second, the rotation center of the universal joint must precisely coincide with the center of mass (CG) of the tested object 9. Any deviation will generate additional artificial righting or overturning moments when the tested object 9 tilts, severely interfering with the stability test data. In addition, the center of mass of the tested object 9 may change during motion, further increasing the difficulty of alignment. Therefore, the design of the universal joint is crucial to ensuring the fidelity of the low-gravity simulation. To address the above problems, refer to... Figure 6 As shown, this embodiment of the invention features a structural design for the universal joint 8, employing a stacked cross-shaped universal joint configuration. The universal joint 8 includes two axial universal joints, one above the other, with an additional axial rotational joint at its connection point with the test object 9. This adapts to the multi-dimensional motion requirements of the test object 9, eliminating torsion and motion interference of the suspension cable 6. This design optimizes the structure of a standard cross-shaped universal joint, significantly improving motion smoothness and increasing the transmission angle range. Through this optimized structure, the stacked cross-shaped universal joint allows the test object 9 to achieve large-angle motions of ±80° in two rotational degrees of freedom, ensuring that the motion posture of the test object 9 is not restricted by the mechanism. Simultaneously, a high-precision cable tension sensor 7 is directly connected to the universal joint 8. The advantage of this connection method is that the sensor can sensitively detect changes in the tension of the suspension cable 6 caused by minute posture changes (e.g., 0.1-degree angle changes), thereby providing high-fidelity force feedback to the system.

[0066] Specifically, referring to Figures 5(a) and 5(b), the rope angle measurement module 5 also includes a steel cable clip 14, a z-axis connecting plate 15, four support columns 17, and a base plate 24. The steel cable clip 14 is fixedly installed on the surface of the z-axis connecting plate 15, and the steel cable clip 14 and the z-axis connecting plate 15 have corresponding coaxial through holes. The suspension cable 6 passes through these coaxial through holes sequentially into the interior of the central measuring head, and then through the central measuring head to connect with the rope tension sensor 7 in the attitude sensing and force feedback module. The size of the coaxial through holes is adapted to the suspension cable 6. In this embodiment, the suspension cable 6 uses a 6mm diameter steel cable to ensure stable and smooth threading. The four support columns 17 are symmetrically arranged, with one end of each support column 17 fixedly connected to the z-axis connecting plate 15 and the other end fixedly connected to the base plate 24, together forming an installation space for accommodating the central measuring head, sliding assembly, and measurement module. An opening is provided in the middle of the base plate 24. The size of the opening matches the shape of the pulley rope fixing mechanism 23, allowing the pulley rope fixing mechanism 23 to pass through and be moved and assembled.

[0067] Specifically, refer to Figure 1 and Figure 3 As shown, the spatial pendulum angle measurement system described in this embodiment of the invention further includes a fixed frame 1, a z-axis constant force unloading mechanism 3, a multi-axis motion control module, a drive module, and a Y-axis tank chain 4. The multi-axis motion control module includes a Y-axis ball screw drive 2 and an X-axis ball screw drive 10. The drive module includes a Y-axis servo motor 11, an X-axis first servo motor 12, and an X-axis second servo motor 13.

[0068] Furthermore, the fixed rack 1, serving as the fundamental support structure of the entire system, provides a stable mounting platform for all hardware components. In this embodiment, the fixed rack 1 is constructed using high-strength aluminum alloy profiles, characterized by its lightweight yet robust nature. Its base is designed with adjustable feet and casters, enabling flexible switching between stable operating and mobile modes. This design not only ensures the stability of the system during testing and operation but also enhances the portability and flexibility of the equipment, facilitating rapid relocation and rearrangement in different locations.

[0069] Furthermore, the X-axis grating ruler 18 and the Y-axis grating ruler 19 are respectively arranged parallel to each other on the sides of the X-axis and Y-axis guide rails of the fixed frame 1, and their reading heads are fixed on the sliding components to ensure that the movement trajectories of the grating rulers and the sliding components are precisely parallel, providing structural assurance for the accuracy of subsequent displacement measurements.

[0070] Furthermore, the z-axis constant force unloading mechanism 3 is mounted on the X-axis upper beam of the fixed frame 1. The suspension cable 6 extends from this mechanism and passes downwards through the rope angle measuring module 5. At the end of the suspension cable 6, a rope tension sensor 7 and a universal joint 8 are connected in sequence, and the cable is connected to the object being measured 9 via the universal joint 8. During system operation, the system actively follows the object being measured 9 through high-precision movement in the XY plane, ensuring that the suspension cable 6 in the Z-axis direction is always vertically downwards, thereby maintaining the stability of the system and the accuracy of the measurement.

[0071] Furthermore, the z-axis constant force unloading mechanism 3 includes a displacement sensor (or servo motor encoder) for real-time monitoring of the vertical extension and retraction length of the suspension cable 6 and the lifting displacement of the tested object 9. The control module is connected to the displacement sensor and can synchronize the Z-axis height data in real time, updating the vertical distance in the calculation model using real-time geometric parameter calculation formulas. Specifically, during dynamic testing, when the tested object 9 undergoes a vertical pose change, the control module receives feedback signals (i.e., real-time displacement compensation) from the z-axis constant force unloading mechanism 3 in real time. At this point, the expression for calculating the spatial pendulum angle will be updated to:

[0072] ;

[0073] ;

[0074] in, Indicates the real-time tilt angle along the X-axis. Indicates the real-time tilt angle along the Y-axis. This represents the displacement along the X-axis. Indicates the displacement along the Y-axis. This represents the initial vertical distance.

[0075] This dynamic compensation mechanism ensures that even when the measured object 9 undergoes a violent jump or descent, the system can still output high-fidelity swing angle data, thereby effectively eliminating calculation errors caused by changes in vertical distance.

[0076] Furthermore, movement along the XY axes is achieved using a multi-axis motion control module and a drive module. Specifically, the Y-axis servo motor 11, the first X-axis servo motor 12, and the second X-axis servo motor 13 in the drive module provide power output, driving the Y-axis ball screw drive 2 and the X-axis ball screw drive 10 to perform linear motion along their respective axes, thereby enabling the load to achieve multi-dimensional position adjustment in the XY plane.

[0077] Furthermore, in terms of structure, the multi-axis motion control module adopts a bridge-type overhead crane for the X-axis, enabling stable movement in the Y-axis plane. Compared with existing gear and rack transmission solutions, the ball screw transmission solution offers higher movement accuracy, with a repeatability of 0.1mm, thus improving the overall performance and operational precision of the system.

[0078] Furthermore, the Y-axis servo motor 11 is mounted on the X-axis platform of the fixed frame 1; the first X-axis servo motor 12 and the second X-axis servo motor 13 are arranged symmetrically and are respectively mounted on the fixed frame 1 at both ends of the Y-axis ball screw drive 2. Through the coordinated drive design of the dual servo motors, synchronous control and error compensation in the X-axis direction can be achieved, effectively improving the positioning accuracy and motion stability of the system, thereby ensuring the accuracy and reliability of the overall operation process.

[0079] Furthermore, the specific connection structure of the z-axis constant force unloading mechanism 3, drive module, multi-axis motion control module, rope angle measurement module 5, and fixed frame 1 is as follows: two sets of Y-axis ball screw drives 2 are arranged parallel to each other on both sides of the top of the fixed frame 1. The first X-axis servo motor 12 and the second X-axis servo motor 13 are symmetrically fixed at both ends of the fixed frame 1, driving the Y-axis ball screw drives 2 on both sides respectively. The X-axis ball screw drive 10 is mounted across the Y-axis drive mechanism on both sides, and one end of it is connected to the Y-axis servo motor 11. The z-axis constant force unloading mechanism 3 is slidably mounted on the X-axis ball screw drive 10, and the rope angle measurement module 5 is fixedly set below the z-axis constant force unloading mechanism 3. The suspension cable 6 is led out through the z-axis constant force unloading mechanism 3, passes vertically downward through the central through hole of the rope angle measurement module 5, and extends to the object under test 9.

[0080] Furthermore, referring to Figure 1 As shown, the Y-axis tank chain 4 serves as an auxiliary protection and tidying device, and is installed on the Y-axis side of the fixed frame 1. Its interior forms a sealed containment channel for the orderly storage, tidying, and protection of the suspension cable 6. This effectively prevents problems such as entanglement, wear, or interference of the cable during equipment movement, ensuring the stability of the transmission link and the safety of equipment operation.

[0081] Furthermore, the working principle of the spatial swing angle measurement system described in this embodiment of the invention is as follows: when the object being measured 9 moves in the horizontal plane, it pulls the suspension cable 6, causing it to tilt. The suspension cable 6 is firmly clamped by the central measuring head, which is mounted on two sets of orthogonally arranged sliders 22 via a slider connecting plate 21, allowing it to slide freely in the XY plane, thereby decoupling the tilting motion of the suspension cable 6 into linear motion in the plane. When the central measuring head slides, two orthogonally arranged high-precision X-axis grating rulers 18 and Y-axis grating rulers 19 can measure its linear displacement in the X and Y directions in real time. and The preferred grating ruler is one with an accuracy of 1µm. Subsequently, the control module uses these displacement values ​​and real-time geometric parameters (e.g., the vertical distance from the universal joint 8 pivot point to the grating ruler plane) to determine the displacement. The precise tilt angles of the suspension cable 6 in both directions are calculated in reverse using trigonometric functions.

[0082] This invention addresses the problems existing in current encoder solutions. Specifically, traditional encoder solutions often suffer from mechanical backlash, transmission errors, and limited resolution, which severely affect measurement accuracy and reliability. This invention overcomes these technical bottlenecks through the aforementioned design, providing a measurement solution with higher accuracy and fidelity. Furthermore, the design concept of this invention differs from traditional rotational and measurement rotation approaches. By decoupling and converting the spatial tilting rotation of the suspension cable 6 into linear motion of the central measuring head in the XY plane, linear displacement data is collected by a grating ruler. Finally, combined with real-time geometric parameters, the cable tilt angle is synthesized through trigonometric function calculations, significantly improving measurement accuracy and dynamic response speed, providing stable and reliable core data support for system closed-loop control.

[0083] The spatial pendulum angle measurement system described in this embodiment of the invention cleverly converts the spatial rotational motion of the suspension cable 6 into a two-dimensional linear displacement on an orthogonal plane through a self-aligning bearing universal joint 20. Simultaneously, this linear displacement is precisely measured using two mutually perpendicular orthogonal optical grating rulers. This design fundamentally changes the measurement method, improving measurement accuracy and reliability. Based on this, the invention has significant technical advantages, specifically as follows:

[0084] First, the embodiments of this invention achieve zero-backlash high-fidelity measurement. Because a grating ruler is used for measurement, there are no transmission links in the measurement chain that generate backlash, effectively eliminating mechanical transmission error sources from a structural perspective and ensuring high-fidelity measurement results. The resolution of the grating ruler can reach 1µm, far exceeding that of traditional encoder solutions, greatly improving measurement accuracy.

[0085] Secondly, unlike the inertial measurement unit (IMU) approach, this embodiment of the invention directly and accurately measures the linear displacement of the suspension rope in the XY plane. This is the most direct and critical physical quantity required to calculate the parasitic torque, and there is no cumulative drift, ensuring the accuracy and reliability of the measurement results.

[0086] Third, the embodiments of the present invention utilize real-time geometric parameters as a lever. Through real-time geometric parameters... The design allows minute angular changes to be precisely amplified into measurable displacements. Unlike existing vision solutions limited by pixel resolution, this invention improves physical measurement accuracy, thereby achieving more precise angle measurements.

[0087] Fourth, this embodiment of the invention employs a combination of a self-aligning universal joint 20 and a linear encoder to achieve purely mechanical contact measurement. This design ensures that the measurement process is completely independent of external environmental conditions. Whether in strong light, a dark room, or complex scenarios with obstructions, as long as the cable moves, the self-aligning universal joint 20 will move accordingly, thereby driving the linear encoder to perform precise measurements. This structure is simple and highly reliable, ensuring the stability and accuracy of the measurement, unaffected by lighting conditions or obstructions.

[0088] Example 2:

[0089] Reference Figure 7 As shown, this embodiment provides a method for measuring the spatial pendulum angle in a suspended low-gravity simulation, which is implemented using the spatial pendulum angle measurement system for a suspended low-gravity simulation described in Embodiment 1, including but not limited to the following steps:

[0090] S1. The test object 9 moves on the horizontal plane, pulling the suspension cable 6 to tilt, and the suspension cable 6 drives the central measuring head to move.

[0091] S2. The central measuring head slides on two sets of orthogonally arranged sliders 22 via the slider connecting plate 21, decoupling the tilting motion of the suspension cable 6 into linear motion in the XY plane.

[0092] S3. The linear displacement in the X and Y directions when the measuring head of the real-time measurement center performs linear motion;

[0093] S4. Real-time acquisition of the displacement compensation amount of the tested object 9 in the Z-axis direction; based on the displacement compensation amount, obtain the real-time geometric structure parameters; based on the linear displacement amount and the real-time geometric structure parameters, calculate the spatial swing angle of the suspension cable 6.

[0094] Specifically, in step S4, the method for calculating the spatial swing angle of the suspension cable 6 based on the linear displacement and real-time geometric parameters is as follows:

[0095] The linear displacement includes X-axis displacement and Y-axis displacement; the spatial swing angle of the suspension cable 6 is calculated inversely based on the X-axis displacement, Y-axis displacement, and real-time geometric parameters; the spatial swing angle includes the tilt angle in the X-axis direction and the tilt angle in the Y-axis direction; the expression for calculating the tilt angle in the X-axis direction is:

[0096] ;

[0097] The expression for calculating the tilt angle along the Y-axis is:

[0098] ;

[0099] in, This represents the displacement along the X-axis. Indicates the displacement along the Y-axis; This represents the real-time geometric structure parameters, which are dynamic parameters adjusted in real time based on displacement compensation. In this embodiment, the real-time geometric structure parameters... The vertical distance between the pivot center of the universal joint 8 and the horizontal measuring plane where the measuring modules (X-axis grating ruler 18 and Y-axis grating ruler 19) are located.

[0100] Furthermore, in step S4, the real-time geometric parameters The expression is:

[0101] ;

[0102] in, Represents real-time geometric parameters. Indicates the initial vertical distance. This indicates the real-time displacement compensation amount along the Z-axis.

[0103] Example 3:

[0104] This embodiment provides a suspended low gravity simulation device, including the spatial swing angle measurement system for suspended low gravity simulation described in Embodiment 1.

[0105] Those skilled in the art will understand that embodiments of this application can be provided as methods, systems, or computer program products. Therefore, this application can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, this application can take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0106] This application is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of this application. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, generate instructions for implementing the flowchart... Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0107] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure 1 One or more processes and / or boxes Figure 1 The function specified in one or more boxes.

[0108] These computer program instructions may also be loaded onto a computer or other programmable data processing equipment to cause a series of operational steps to be performed on the computer or other programmable equipment to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable equipment for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 The steps of the function specified in one or more boxes.

[0109] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A suspended low-gravity simulation spatial pendulum angle measurement system, characterized in that, include: The suspension cable (6) is connected to the object being tested (9); A central measuring head is used to clamp the suspension cable (6); the central measuring head includes an upper pulley cable fixing mechanism (16), a self-aligning bearing universal joint (20), and a lower pulley cable fixing mechanism (23); both the upper pulley cable fixing mechanism (16) and the lower pulley cable fixing mechanism (23) include orthogonally arranged pre-tensioning guide wheels, which are used to achieve rigid constraint and vibration suppression on the suspension cable (6); The sliding assembly includes a slider connecting plate (21) and two sets of orthogonally arranged sliders (22). The self-aligning bearing universal joint (20) is mounted on the two sets of sliders (22) through the slider connecting plate (21), allowing the central measuring head to slide freely in the XY plane. The slider connecting plate (21) is provided with a through hole. The self-aligning bearing universal joint (20) passes through the through hole and is connected to the upper pulley rope fixing mechanism (16) and the lower pulley rope fixing mechanism (23) located on both sides of the slider connecting plate (21). When the test object (9) moves, the self-aligning bearing universal joint (20) pushes the slider (22) to move, decomposing and converting the spatial rotational motion of the suspension cable (6) into the linear displacement of the slider (22) in the XY plane. The measurement module includes an X-axis grating ruler (18) and a Y-axis grating ruler (19). The X-axis grating ruler (18) and the Y-axis grating ruler (19) are respectively set on two sets of orthogonally arranged sliders (22) for real-time measurement of the linear displacement to obtain the linear displacement of the central measuring head in the X and Y directions. The attitude perception and force feedback module includes a rope tension sensor (7) and a universal joint (8). One end of the rope tension sensor (7) is connected to the suspension cable (6), and the other end is connected to the universal joint (8). The universal joint (8) is connected to the test object (9). The universal joint (8) has a stacked cross structure. The connection end between the universal joint (8) and the test object (9) is provided with an axial rotation joint to eliminate the torsion and motion interference of the suspension cable (6). Z-axis constant force unloading mechanism (3) includes a displacement sensor; the displacement sensor is used to monitor in real time the extension and retraction length of the suspension cable (6) in the vertical direction, as well as the lifting displacement of the test object (9); The control module is connected to the measurement module and the Z-axis constant force unloading mechanism (3) and is used to acquire the displacement compensation amount of the test object (9) in the Z-axis direction in real time, obtain the real-time geometric structure parameters based on the displacement compensation amount, and calculate the tilt angle of the suspension cable (6) in the X and Y directions based on the linear displacement amount and the real-time geometric structure parameters. When the tested object (9) undergoes a vertical pose change, the control module receives the real-time displacement compensation from the Z-axis constant force unloading mechanism (3). The expression for calculating the spatial swing angle is updated as follows: ; ; in, Indicates the real-time tilt angle along the X-axis. Indicates the real-time tilt angle along the Y-axis. This represents the displacement along the X-axis. Indicates the displacement along the Y-axis. This represents the initial vertical distance.

2. The suspended low-gravity simulation spatial pendulum angle measurement system according to claim 1, characterized in that, It also includes a multi-axis motion control module and a drive module. The multi-axis motion control module includes an X-axis ball screw drive (10); the drive module includes a Y-axis servo motor (11); the X-axis ball screw drive (10) is connected to the Y-axis servo motor (11).

3. The suspended low-gravity simulation spatial pendulum angle measurement system according to claim 1, characterized in that, It also includes a steel cable clip (14) and a Z-axis connecting plate (15). The steel cable clip (14) is disposed on the surface of the Z-axis connecting plate (15). The steel cable clip (14) and the Z-axis connecting plate (15) are provided with coaxial through holes. The suspension cable (6) passes through the coaxial through holes and enters the central measuring head.

4. A method for measuring the spatial pendulum angle in a suspended low-gravity simulation, implemented using a spatial pendulum angle measurement system for a suspended low-gravity simulation as described in any one of claims 1 to 3, characterized in that, include: S1. The test object (9) moves on the horizontal plane and pulls the suspension cable (6) to produce an inclination. The suspension cable (6) drives the central measuring head to move. S2. The central measuring head slides on two sets of orthogonally arranged sliders (22) through the slider connecting plate (21), decoupling the tilting motion of the suspension cable (6) into linear motion in the XY plane; S3. Real-time measurement of the linear displacement in the X and Y directions when the central measuring head performs linear motion; S4. Real-time acquisition of the displacement compensation amount of the tested object (9) in the Z-axis direction, and real-time geometric structure parameters based on the displacement compensation amount; and calculation of the spatial swing angle of the suspension cable (6) based on the linear displacement amount and the real-time geometric structure parameters.

5. The method for measuring the spatial pendulum angle in a suspended low-gravity simulation according to claim 4, characterized in that, The method for calculating the spatial swing angle of the suspension cable (6) based on the linear displacement and the real-time geometric parameters in S4 is as follows: The linear displacement includes X-axis displacement and Y-axis displacement; the spatial swing angle of the suspension cable (6) is calculated in reverse based on the X-axis displacement, the Y-axis displacement, and the real-time geometric parameters; wherein the spatial swing angle includes the tilt angle in the X-axis direction and the tilt angle in the Y-axis direction; the calculation expression for the tilt angle in the X-axis direction is: ; The expression for calculating the tilt angle along the Y-axis is: ； in, This represents the displacement along the X-axis. Indicates the displacement along the Y-axis. This represents the real-time geometric parameters.

6. The method for measuring the spatial pendulum angle in a suspended low-gravity simulation according to claim 4, characterized in that, The expression for the real-time geometric structure parameters is: ; in, Represents real-time geometric parameters. Indicates the initial vertical distance. This indicates the real-time displacement compensation amount along the Z-axis.

7. A suspended low-gravity simulation device, characterized in that, The system includes a suspended low-gravity simulation spatial pendulum angle measurement system as described in any one of claims 1 to 3.

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