Microgravity simulation system capable of repeatedly unfolding and folding solar wing

Abstract

The invention discloses a microgravity simulation system capable of repeatedly unfolding and folding a solar wing, which comprises a foldable solar wing, a gravity compensation device, a driving device and a six-degree-of-freedom mechanical arm, and is characterized in that the foldable solar wing is formed by hinging a plurality of panels, and the tail end of the six-degree-of-freedom mechanical arm is hinged with the innermost panel of the foldable solar wing through a bracket; the gravity compensation device comprises lifting lugs arranged in the geometric center of each panel, pulley assemblies, sliding rails, ropes and springs, the number of the pulley assemblies is the same as that of the lifting lugs, one ends of the ropes are connected with the lifting lugs, the other ends of the ropes are connected to the pulley assemblies through the springs, and the pulley assemblies are slidably connected to the sliding rails. The spring is configured to provide elastic force equal to the gravity of the corresponding panel; the track of the slide rail is matched with the horizontal movement path of the hanging point of the corresponding panel in the unfolding and folding process of the solar wing; the driving device is used for driving the panels to rotate relatively, and unfolding and folding of the solar wing are achieved. And the requirements of a large-scale multi-panel solar wing ground test can be met.

Description

Technical Field

[0001] This invention relates to the field of spacecraft ground testing technology, and in particular to a microgravity simulation system with a retractable solar array. Background Technology

[0002] Solar panels are the primary energy supply components for satellites and other spacecraft. During launch, they are retracted to save space within the rocket fairing, and after entering orbit, they need to reliably deploy to their operational state. The reliability of solar panel deployment directly affects the success or failure of the space mission; therefore, the deployment and retraction performance of the solar panels must be fully verified during the ground testing phase. Among these tests, microgravity environment simulation is a crucial step, aiming to counteract the gravitational forces exerted on the solar panel panels in the ground's gravity field, thereby realistically reproducing the zero-gravity deployment and retraction behavior in space.

[0003] Currently, ground-based microgravity simulation technologies mainly include three types: air-floating, water-floating, and suspended. Air-floating systems form an air film on a smooth platform using air feet, achieving near-frictionless motion. However, they require extremely high platform flatness and are difficult to adapt to multi-panel solar arrays with large-scale motion trajectories. Water-floating systems utilize the buoyancy of water to counteract gravity, but the viscous drag of water affects the realism of deployment and recovery dynamics, and subsequent cleaning and maintenance are complex. Suspended systems apply upward tension to the solar array components using ropes, springs, or counterweights to counteract gravity. They have advantages such as simple structure, low cost, and ease of implementation, and are therefore widely used in ground-based solar array testing.

[0004] However, existing suspended microgravity simulation systems still have the following technical problems in the deployment and retraction tests of multi-panel solar arrays:

[0005] First, the accuracy of gravity compensation is insufficient. Traditional suspended systems typically use a single-point suspension method, either suspending the entire solar array or using a fixed suspension point for each panel. However, during the deployment and retraction of multi-panel solar arrays, the center of mass of each panel changes continuously with the deployment and retraction angle. The fixed suspension point cannot follow the movement of the center of mass in real time, causing the suspension force and the line of action of gravity to not coincide, generating additional torque, which in turn causes panel attitude deviation and gravity compensation error. In addition, the movement trajectory of the panels during deployment and retraction often involves complex horizontal and vertical displacements, and existing suspension systems struggle to simultaneously decouple and compensate for movements in both directions.

[0006] Secondly, the simulated root boundary conditions are unrealistic. During in-orbit deployment of the solar array, its root is connected to the satellite body via a hinge mechanism. The satellite body imposes complex six-degree-of-freedom motion constraints on the root during deployment. Existing suspended systems typically fix the solar array root to a support frame, only releasing the deployment degree of freedom. This fails to simulate the dynamic response of the satellite body in the three translational and three rotational directions, leading to differences between the boundary conditions in ground tests and in-orbit conditions. This affects the realism of the deployment dynamics and the reliability of the test results.

[0007] Third, the accuracy of repeated deployment and retrieval is difficult to guarantee. Ground tests of solar arrays often require multiple deployments and retrievals to verify the fatigue life and reliability of the mechanism. After multiple deployments and retrievals, existing suspended systems are prone to drifting of the suspension point position and fluctuations in gravity compensation force due to rope wear, spring fatigue, and accumulated clearance in the slide rails. This affects the repeatability of the deployment and retrieval trajectory and makes it difficult to meet the requirements of high-precision repeated tests.

[0008] Fourth, the application of robotic arms has not yet formed an effective synergy with the suspension system. In recent years, industrial robotic arms, due to their six-degree-of-freedom flexible motion capabilities, have been gradually introduced into the field of spacecraft ground testing. However, in existing technologies, robotic arms are usually only used as a drive source or static support, without forming a synergistic control with the suspension system. This makes it impossible to simultaneously achieve dynamic simulation of root boundary conditions and accurate compensation of panel gravity. The two work independently, making it difficult to leverage their synergistic advantages. Summary of the Invention

[0009] The purpose of this invention is to overcome the shortcomings of the prior art and provide a microgravity simulation system for a reusable solar array that can achieve accurate gravity compensation, realistically simulate root boundary conditions, and support high-precision reusable solar array deployment and deployment, so as to meet the needs of large-scale multi-panel solar array ground tests.

[0010] The objective of this invention is achieved through the following technical solution:

[0011] A microgravity simulation system with a retractable solar array includes a foldable solar array, a gravity compensation device, a drive device, and a six-degree-of-freedom robotic arm. The foldable solar array is composed of several panels hinged together.

[0012] The end of the six-degree-of-freedom robotic arm is hinged to a panel on the innermost side of the foldable solar wing via a bracket, which is used to provide multi-degree-of-freedom motion support for the foldable solar wing.

[0013] The gravity compensation device includes a lug disposed at the geometric center of each panel, a pulley assembly equal in number to the lugs, a slide rail, a rope, and a spring. One end of the rope is connected to the lug, and the other end is connected to the pulley assembly via the spring. The pulley assembly is slidably connected to the slide rail. The spring is configured to provide a spring force equal to the weight of the corresponding panel. The trajectory of the slide rail matches the horizontal movement path of the suspension point of the corresponding panel during the deployment and retraction of the solar panels.

[0014] The drive device is used to drive the relative rotation between the panels to realize the deployment and retraction of the solar panels.

[0015] Furthermore, the driving device includes an extension and retraction drive motor located at the hinge position of the two panels at the root of the foldable solar panel. The extension and retraction drive motor and the six-degree-of-freedom robotic arm form a cooperative driving relationship. During the extension and retraction process, the extension and retraction drive motor provides the main driving force, and the six-degree-of-freedom robotic arm performs follow-up movements and provides dynamic root constraints.

[0016] Furthermore, the lifting lug is a ball joint, and the fixed end of the ball joint is connected to the geometric center of the panel; the ball joint enables the rope to swing in any direction relative to the panel, avoiding the generation of additional bending moment in the rope when the panel moves.

[0017] Furthermore, the six-degree-of-freedom robotic arm performs position control according to a preset deployment and retraction trajectory, providing boundary constraints that simulate the satellite body for the foldable solar array and compensating for position deviations during the deployment and retraction process.

[0018] Furthermore, the slide rail is composed of multiple curved guide rail segments, which are fixed above the test site. The curved guide rail segments are the horizontal projection path of the geometric center of the panel unfolding.

[0019] Furthermore, the overall size of the system in its fully folded state is less than 4m × 4m × 2m.

[0020] Furthermore, the spring is a helical spring.

[0021] Furthermore, the end of the six-degree-of-freedom robotic arm is equipped with a root clamping fixture, which is connected to the bracket. The bracket has a flat-bottomed V-shaped structure, and its two ends are respectively fixed to the two sides of the panel at the innermost center of the foldable solar panel.

[0022] Compared with the prior art, the beneficial effects of the technical solution of the present invention are:

[0023] 1. The microgravity simulation system for the retractable solar array of the present invention calculates the motion path of the suspension point in three-dimensional space and designs a curved slide rail accordingly, so that the horizontal movement of the suspension point corresponds perfectly with the trajectory of the slide rail, and the vertical displacement is effectively absorbed by the spring, thereby achieving precise cancellation of the gravity of each panel.

[0024] 2. This invention uses a six-degree-of-freedom robotic arm to form the boundary conditions at the root of the solar array. The six-degree-of-freedom motion of the robotic arm simulates the fixed points required for the solar array to deploy on the satellite. This can realistically reproduce the complex motion constraints imposed on the root of the solar array by the satellite body during the deployment process, overcoming the limitations of traditional fixed support or single-degree-of-freedom drive.

[0025] 3. This invention achieves high-precision, repeatable deployment and retraction of the solar array by coordinating the deployment and retraction drive motor and the robotic arm. The deployment and retraction drive motor is responsible for the main motion, while the robotic arm performs six-degree-of-freedom follow-up according to the motor's motion state and compensates for position deviations.

[0026] 4. The present invention adopts a solution that combines a robotic arm with a suspension system. It utilizes existing robotic arm equipment and eliminates the need to develop complex air flotation or water flotation devices, thereby reducing system costs and maintenance difficulty.

[0027] 5. The system of the present invention has a compact overall structure, with an overall size of less than 4m×4m×2m when fully folded, which can adapt to conventional laboratory space conditions and facilitate the conduct of ground deployment and recovery tests of solar arrays in a limited space. Attached Figure Description

[0028] Figure 1 This is a schematic diagram of the structure of the present invention;

[0029] Figure 2 This is a schematic diagram showing the relationship between the slide rail trajectory and the motion of the suspension point according to the present invention;

[0030] Figure 3 This is a schematic diagram of the six-degree-of-freedom robotic arm structure of the present invention;

[0031] Figure 4 This is a partially enlarged view of the connection between the six-degree-of-freedom robotic arm and the solar array of the present invention;

[0032] Figure 5 This is a schematic diagram of the fully folded state of the present invention;

[0033] Figure 6 This is a schematic diagram of the intermediate process states of the present invention;

[0034] Figure 7 This is a schematic diagram of the fully deployed state of the present invention. Detailed Implementation

[0035] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are only for explaining the present invention and are not intended to limit the present invention.

[0036] like Figures 1 to 7 As shown, this invention provides a microgravity simulation system for a reusable solar array, aiming to address the shortcomings of traditional suspended systems in terms of gravity compensation accuracy, root boundary condition simulation realism, and reusability accuracy. The system is particularly suitable for conducting ground-based microgravity environment simulation experiments on multi-panel, laterally deployable solar arrays.

[0037] like Figure 1 The system mainly includes a solar array, a gravity compensation device, a root constraint and motion simulation device, and a drive device.

[0038] Foldable solar panels: These are composed of multiple panels 1 hinged together sequentially, and can be unfolded or folded along the unfolding direction. This embodiment uses six panels 1 as an example for illustration, but the number of panels can be adjusted according to actual applications.

[0039] Gravity compensation device: Used to precisely counteract the gravity acting on each panel 1 during the unfolding and retraction process. Its core lies in designing an independent, high-precision motion-following and compensation mechanism for the geometric center of each panel 1 through pre-calculation. This device includes a lug located at the geometric center of each panel 1, a pulley assembly 5 corresponding to the lug, a slide rail 6 for the pulley assembly 5 to slide on, a connecting rope 3, and a spring 4. The pulley assembly 5 is slidably mounted on the slide rail 6 and can slide freely along the slide rail 6. The upper end of the rope 3 is connected to the pulley assembly 5 via the spring 4, and the lower end is connected to the lug. The lifting force (elastic force) provided by the spring 4 after pre-tensioning is always equal to the gravity of the corresponding panel 1.

[0040] Root constraint: A six-degree-of-freedom robotic arm 7 is used, with its end connected to a flat-bottomed V-shaped support 9 via a root clamping fixture 10. The two ends of the support 9 are fixed to both sides of the innermost center of the solar array panel 1, providing dynamic and complex boundary conditions for the root of the solar array, simulating the satellite body's movement. The robotic arm 7 can perform six-degree-of-freedom motion according to a preset program, simulating the constraint and follow-up motion of the satellite body's attitude changes in space on the root of the solar array.

[0041] Drive unit: Typically, it is an extension / retraction drive motor 8 located at the hinge of any two panels at the root of the solar array, used to provide the main driving force for the deployment and retraction of the solar array. In this embodiment, the extension / retraction drive motor 8 and the six-degree-of-freedom robotic arm 7 form a cooperative driving relationship.

[0042] like Figure 2As shown, to achieve accurate gravity compensation, the key is to ensure that the vertical force at the suspension point of the lifting lug always passes through the center of mass of the panel and to minimize constraints in non-gravitational directions. To this end, this invention first performs kinematic calculations on the movement paths of the geometric centers of each panel 1 in three-dimensional space during the folding and unfolding process of the solar array. Through these calculations, the precise two-dimensional projection trajectory of the suspension point of each lifting lug in the horizontal plane can be predetermined, while simultaneously controlling the displacement fluctuations of the suspension point in the vertical direction within a preset small threshold range.

[0043] Based on the horizontal movement path of the suspension point obtained from the above calculation, a curved slide rail 6 is designed to correspond precisely to and match it. For example... Figure 1 and Figure 2 As shown, the slide rail 6 is fixed above the test site and is usually composed of multiple independent curved guide rail segments. In this embodiment, there are 5 segments, and the shape of each guide rail segment is the horizontal projection route of the corresponding hanging point of panel 1. The slide rail 6 has a compact overall layout. In this embodiment, its projected area in the horizontal plane is less than 4m x 4m.

[0044] The pulley assembly 5 is slidably mounted on the corresponding slide rail 6. The rope 3 is connected to the pulley assembly 5 via a spring 4. Since the trajectory of the slide rail 6 corresponds perfectly to the horizontal movement path of the suspension point, when the solar panels extend and retract, the lifting lugs drive the rope 3 and the pulley assembly 5, allowing the pulley assembly 5 to slide along the predetermined slide rail 6 path with almost no resistance, thereby achieving precise guidance of the horizontal movement of the suspension point.

[0045] Each panel 1 has a lifting lug 2 at its geometric center, preferably a ball joint. The fixed end of the ball joint is connected to the geometric center of the panel 1, and the movable end is connected to the lower end of the rope 3. The ball joint structure allows the rope 3 to swing slightly relative to the panel 1 in any direction, avoiding additional bending moments caused by motion mismatch and ensuring that the direction of the suspension force is always approximately vertically upward.

[0046] The constant force for gravity compensation is provided by spring 4. In this embodiment, spring 4 is a helical spring, which is pre-tightened during system installation so that its output force is precisely equal to the weight of the corresponding panel 1. One end of spring 4 is connected to pulley assembly 5, and the other end is connected to the lifting lug via rope 3. It has two functions: first, to provide a constant lifting force to counteract the weight of the panel; second, to absorb the slight vertical movement of the lifting lug by utilizing its own expansion and contraction deformation, thereby achieving "effective elimination of vertical movement". Throughout the entire extension and retraction process, the output force of spring 4 remains essentially constant, providing a near-zero gravity environment for panel 1.

[0047] like Figure 3 and Figure 4As shown, the six-degree-of-freedom robotic arm 7 is crucial for simulating real-world on-orbit boundary conditions in this system. The six-degree-of-freedom robotic arm 7 has six rotary joints, labeled A, B, C, D, E, and F. Joint A is the base rotary joint, enabling rotation around the vertical axis; joint B is the shoulder swing joint, enabling forward and backward swinging; joint C is the elbow swing joint, enabling up and down swinging; joint D is the wrist rotary joint, enabling rotation around the forearm axis; joint E is the wrist swing joint, enabling wrist pitch movement; and joint F is the wrist rotation joint, enabling the end effector's rotation. Through the coordinated movement of these six joints, the end effector of the robotic arm 7 can achieve any position and orientation in three-dimensional space, possessing complete six-degree-of-freedom motion capabilities.

[0048] During the experiment, the six-degree-of-freedom robotic arm 7 moves according to a preset program or real-time commands. Its trajectory is planned based on the expected movements of the satellite body during the solar array deployment process (such as attitude adjustment and vibration). Through the six-degree-of-freedom active movement of the six-degree-of-freedom robotic arm 7, complex dynamic constraints similar to those of a real satellite body can be provided to the root of the solar array, including translational constraints in three directions and rotational constraints in three directions, thereby greatly improving the realism of the boundary conditions of the ground experiment.

[0049] To achieve high-precision and repeatable deployment and retraction tests, the drive system adopts a cooperative control strategy. The deployment and retraction drive motor 8 is the main drive source for the deployment and retraction of the solar array, driving the solar array deployment mechanism according to a preset speed and angle curve.

[0050] Meanwhile, the six-degree-of-freedom robotic arm 7 and the deployment / retraction drive motor 8 form a coordinated driving relationship. During deployment, the six-degree-of-freedom robotic arm 7 mainly operates in "position control" mode, with its end effector moving along a trajectory matched to the main deployment motion, simulating the coordinated motion of the satellite body. During retraction, the six-degree-of-freedom robotic arm 7 can switch to "force control" mode, actively following the movement of the solar array root, providing necessary dynamic support while avoiding over-constraint and protecting the solar array mechanism.

[0051] This collaborative mechanism ensures that: 1) the main driving force source is clear and the control is simple and reliable; 2) the six-degree-of-freedom robotic arm 7 can dynamically compensate for the root position deviation caused by factors such as mechanism clearance and deformation; 3) the two work together to achieve high-precision trajectory and attitude control of the entire process of solar wing deployment and retraction, thereby ensuring the consistency of multiple repeated deployment and retraction tests.

[0052] like Figures 5-7 As shown, the system has three typical operating states:

[0053] Fully folded state ( Figure 5Each panel 1 is stacked and folded together in sequence, with the pulley assembly 5 located at the starting end of each slide rail 6, and the joints of the six-degree-of-freedom robotic arm 7 in a compact folded posture. At this time, the overall size of the system is minimized, less than 4m (length) x 4m (width) x 2m (height), which facilitates its arrangement and storage in the laboratory.

[0054] Intermediate unfolding and unwinding process status ( Figure 6 The unfolding drive motor 8 drives the panel 1 to unfold, and the hanging points of each panel 1 move along their three-dimensional paths, driving the pulley assembly 5 to slide to the corresponding position on the target curved slide rail 6. The spring 4 extends and retracts to maintain a constant force, and the rope 3 may swing with the panel. The joints of the six-degree-of-freedom robotic arm 7 move in coordination, so that its end effector follows the movement of the root of the solar panel and provides dynamic constraints.

[0055] Fully unfolded state ( Figure 7 Panel 1 is fully extended to the working position, and pulley assembly 5 slides to the ends of each rail 6 and may be locked. The end effector of the six-degree-of-freedom robotic arm 7 reaches and remains in the predetermined position and attitude, simulating the final constraint state of the satellite body on the deployed solar array.

[0056] Preferably, the deployment and retrieval process of the system in this embodiment is as follows:

[0057] Deployment Phase: The deployment drive motor 8 starts, driving the solar array deployment mechanism at a preset angular velocity, causing each solar array panel 1 to deploy sequentially. Simultaneously, the six-degree-of-freedom robotic arm 7 moves along a preset trajectory in position control mode. Through the coordinated control of joints A, B, C, D, E, and F, it simulates the motion constraint of the satellite body on the root of the solar array. The hanging points on each panel 1 move with the panel, and the pulley system 5 slides freely on the slide rail 6 along a curve perfectly corresponding to the horizontal movement path. The spring 4 applies a nearly constant upward pulling force to the panel 1 through the rope 3, counteracting gravity. When all panels 1 reach the fully deployed position, the deployment drive motor 8 stops, and the six-degree-of-freedom robotic arm 7 remains locked in position, completing the deployment process.

[0058] The retraction phase: The retraction drive motor 8 rotates in the opposite direction, driving the solar panel retraction mechanism to fold and retract each panel 1 sequentially. The six-degree-of-freedom robotic arm 7 switches to force control mode, actively following the movement of the solar panel root through the coordinated adjustment of joints A, B, C, D, E, and F, avoiding excessive internal stress caused by movement mismatch and achieving "over-constraint avoidance". When all panels 1 reach the fully retracted position, the retraction drive motor 8 stops, the six-degree-of-freedom robotic arm 7 stops moving, and the retraction process is completed.

[0059] Thanks to its motion path calculation and slide rail matching design, combined with the constant force characteristics of the springs, this system can achieve high-precision gravity compensation for the solar array. Simultaneously, through real-time feedback control from high-precision position sensors, the system can perform multiple repeated deployments and retractions with high reset accuracy for each panel, meeting the requirements of ground testing. The overall system dimensions are less than 4m × 4m × 2m, allowing for installation and use in a conventional laboratory.

[0060] This invention is not limited to the embodiments described above. The above description of specific embodiments is intended to illustrate and explain the technical solutions of this invention. The specific embodiments described above are merely illustrative and not restrictive. Without departing from the spirit and scope of the claims, those skilled in the art can make many specific modifications based on the teachings of this invention, and these modifications all fall within the scope of protection of this invention.

Claims

1. A microgravity simulation system with a reusable solar array, characterized in that, It includes a foldable solar array, a gravity compensation device, a drive device, and a six-degree-of-freedom robotic arm (7). The foldable solar array is composed of several panels (1) hinged together, wherein: The end of the six-degree-of-freedom robotic arm (7) is hinged to a panel (1) on the innermost side of the foldable solar wing via a bracket (9) to provide multi-degree-of-freedom motion support for the foldable solar wing; The gravity compensation device includes a lug (2) located at the geometric center of each panel (1), a pulley assembly (5) of the same number as the lug (2), a slide rail (6), a rope (3), and a spring (4). One end of the rope (3) is connected to the lug (2), and the other end is connected to the pulley assembly (5) via the spring (4). The pulley assembly (5) is slidably connected to the slide rail (6). The spring (4) is configured to provide a spring force equal to the weight of the corresponding panel (1). The trajectory of the slide rail (6) matches the horizontal movement path of the lug (2) of the corresponding panel (1) during the expansion and retraction of the solar wing. The drive device is used to drive the relative rotation between each panel (1) to realize the deployment and retraction of the solar panels.

2. The microgravity simulation system with a reusable solar array according to claim 1, characterized in that, The drive device includes an extension and retraction drive motor (8) located at the hinge position of any two panels (1) at the root of the foldable solar wing. The extension and retraction drive motor (8) and the six-degree-of-freedom robotic arm (7) form a cooperative drive relationship. During the deployment and retraction process, the deployment and retraction drive motor (8) provides the main driving force, and the six-degree-of-freedom robotic arm (7) performs follow-up and provides dynamic root constraints.

3. The microgravity simulation system with a reusable solar array according to claim 1, characterized in that, The lug (2) is a ball joint, and the fixed end of the ball joint is connected to the geometric center of the panel (1). The ball joint enables the rope (3) to swing in any direction relative to the panel (1), avoiding the additional bending moment generated by the rope (3) when the panel (1) moves.

4. The microgravity simulation system for a reusable solar array according to claim 1, characterized in that, The six-degree-of-freedom robotic arm (7) performs position control according to the preset deployment and retraction trajectory, providing the foldable solar array with boundary constraints that simulate the satellite body and compensating for position deviations during deployment and retraction.

5. A microgravity simulation system with a reusable solar array according to claim 1, characterized in that, The slide rail (6) is composed of multiple curved guide rail segments, which are fixed above the test site. The curved guide rail segments are the horizontal projection route of the geometric center of the panel unfolding.

6. The microgravity simulation system for a reusable solar array according to claim 1, characterized in that, The overall dimensions of the system when fully folded are less than 4m × 4m × 2m.

7. A microgravity simulation system with a reusable solar array according to claim 1, characterized in that, The spring (4) is a helical spring.

8. A microgravity simulation system with a reusable solar array according to claim 1, characterized in that, The six-degree-of-freedom robotic arm (7) is equipped with a root clamping fixture (10) at its end. The root clamping fixture (10) is connected to the bracket (9). The bracket (9) has a flat-bottomed V-shaped structure. The two ends of the bracket (9) are respectively fixed to the two sides of the panel (1) at the innermost center of the foldable solar wing.

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