A low-gravity compensation method for a space manipulator based on a whole single-point suspension mode

Abstract

The present application relates to a kind of space manipulator low gravity compensation method based on overall single point suspension mode, belong to space unfolding mechanism integrated assembly and test field;For four degrees of freedom space manipulator, its gravity unloading method is described;Mechanical suspension method applies suspension pull force to manipulator by sling, and air suspension suspension method applies suspension pull force to manipulator by helium balloon lift, to realize 1 / 6 gravity simulation of space manipulator ground deployment test process, to meet adaptive following and motion process high stability control in the whole motion process of manipulator;The present application realizes adaptive following, motion process high stability control of ground deployment test process in the state of space manipulator single point suspension, to meet the interference avoidance demand and unloading efficiency in the whole motion process of manipulator.

Description

Technical Field

[0001] This invention belongs to the field of space deployment mechanism integration, assembly and testing; it relates to a low gravity compensation method for a space robotic arm based on an overall single-point suspension method. Background Technology

[0002] A space robotic arm is a specialized robot used in space to perform tasks such as supporting the construction and operation of space stations, assembling and servicing satellites, and exploring and experimenting on planetary surfaces. Based on the tasks they perform, space robotic arms can be divided into on-orbit operating robotic arms and...

[0003] There are two types of robotic arms for space exploration: the former includes robotic arms used for on-orbit assembly, maintenance, inspection, and assisting astronauts in their activities.

[0004] The latter includes various robots for patrol and movement, sample collection and scientific measurement, and assisting astronauts in exploration.

[0005] Space robotic arms are generally multi-degree-of-freedom serial configurations. Depending on the spatial structure and operational requirements, the number of degrees of freedom of the product ranges from 4 to 7. Structurally, they mainly consist of three parts: robotic arm joints, arm components, and end effectors. The number of matching joints varies from 4 to 7 depending on the number of degrees of freedom of the robotic arm.

[0006] Space robotic arms operate in a zero-gravity (low-gravity) environment. To simulate the actual operation of the robotic arm, gravity unloading needs to be performed on the robotic arm while it is on the ground. Currently, commonly used gravity unloading methods include drop method, parabolic flight method, buoyancy method, air buoyancy method, and suspension method. Among these, the drop method and parabolic flight method provide low-gravity conditions for a relatively short time, while the buoyancy method has many limitations. Currently, for space robotic arm products, the air buoyancy method and suspension method are more widely used. Since the air buoyancy method can only realize the two-dimensional deployment of the robotic arm and cannot truly reflect the three-dimensional motion state of the product, the suspension method is receiving increasing attention.

[0007] The suspension method can be further divided into mechanical suspension and air suspension. Currently, the main principle of using the suspension method to implement gravity unloading of robotic arms is to apply gravity in the vertical direction through the center of mass to the two arms of the robotic arm or to several joints. Due to the large number of suspension points, it is applicable to products with relatively simple motion trajectories. However, for robotic arms with complex motion trajectories and end-effector separation conditions, it is very easy to cause interference and collision during movement and insufficient unloading efficiency. Summary of the Invention

[0008] The technical problem solved by this invention is to overcome the shortcomings of the prior art and propose a low gravity compensation method for a space robotic arm based on an overall single-point suspension method. This method enables adaptive following and high stability control of the motion process during the ground deployment test of the space robotic arm, aiming to meet the interference avoidance requirements and unloading efficiency of the robotic arm throughout its entire motion process.

[0009] The solution of the present invention is:

[0010] A low-gravity compensation method for a space robotic arm based on a single-point suspension system includes:

[0011] Step 1: Divide the robotic arm body into arm A component and arm B component; arm A component includes shoulder joint support, shoulder joint, arm A, elbow joint, and elbow joint fixation support; arm B component includes elbow joint output support, arm B, wrist joint support, wrist joint, and end effector.

[0012] Define the shoulder joint position as point M and the elbow joint position as point N; calculate the torque M generated at point M when the robotic arm is in any position on the ground. OM The torque M generated at point N ON ; Calculate the torque M generated at point M under lunar surface gravity of 1 / 6. OM1 / 6g The torque M generated at point N ON1 / 6g ;

[0013] Let the initial position of the single-point suspension be b4, and let the suspension force F be F; solve for the expressions of b4 and F.

[0014] Step 2: If the single-point suspension position is located within the envelope area of ​​the end effector's motion trajectory, set a center of gravity adjustment disc on boom A and boom B respectively; install both center of gravity adjustment discs on the side close to the elbow joint to prevent the single-point suspension position b4 from being located within the envelope area of ​​the end effector's motion trajectory.

[0015] Step 3: Calculate the position and suspension pressure of the single-point suspension again using the method in Step 1; after confirming that the suspension point is outside the envelope area of ​​the end effector's motion trajectory, obtain the line of action of the suspension point position, which is perpendicular to the length direction of the arm; realize the physical connection between the robotic arm and the external sling or rope through the suspension point connection structure; at the same time, avoid interference and collision between the robotic arm itself and the external sling or rope and the robotic arm during the movement of the robotic arm.

[0016] Step 4: Analyze the unloading efficiency of the elbow and shoulder joints. Based on the unloading efficiency of the elbow and shoulder joints, correct the running trajectory of the end effector to ensure that the gravity unloading efficiency of the robotic arm meets the requirements and complete the low gravity compensation of the robotic arm.

[0017] In the aforementioned low-gravity compensation method for a space robotic arm based on a single-point suspension system, in step one, the shoulder joint support is connected to the external base joint; the shoulder joint is mounted on the shoulder joint support; one axial end of arm A is connected to the shoulder joint; the other axial end of arm A is connected to the elbow joint fixing support; the elbow joint is mounted on the elbow joint fixing support; the elbow joint output support is connected to the elbow joint fixing support via the elbow joint; one end of arm B is connected to the elbow joint output support; the other end of arm B is connected to the wrist joint support; the wrist joint is mounted on the wrist joint support; and the end effector is connected to the wrist joint. The end effector is considered a fixed mass block; the position where the relative angle between the end effector's axial direction and the arm B's axial direction is 0° is set as the initial orientation of the end effector.

[0018] In the aforementioned low-gravity compensation method for a space robotic arm based on a single-point suspension system, under ground conditions, the torque M... OM The calculation method is as follows:

[0019] M OM =m1ga1cosα+m2g(lcosα+b2sinθ)-F(lcosα+b4sinθ) (1)

[0020] In the formula, m1 is the weight of component A of the boom;

[0021] m2 is the weight of component B of the boom;

[0022] a1 is the distance from the center of mass of component A of the arm bar to the center of the shoulder joint;

[0023] b2 is the distance from the center of mass of the arm-bar assembly A to the center of the elbow joint;

[0024] l is the distance between the centers of the shoulder joint and the elbow joint;

[0025] α is the angle between the axis of arm A and the horizontal plane in any posture;

[0026] θ is the angle between the arm B axis and the vertical plane in any posture;

[0027] F represents the single-point suspension tension;

[0028] b4 is the distance from the suspension position to the center of the elbow joint;

[0029] g is the acceleration due to gravity;

[0030] Torque M ON The calculation method is as follows:

[0031] M ON =m2gb2sinθ-Fb4sinθ (2).

[0032] In the aforementioned low-gravity compensation method for a space robotic arm based on a single-point suspension system, under lunar surface gravity conditions of 1 / 6, the torque M... OM1 / 6g The calculation method is as follows:

[0033]

[0034] Torque M ON1 / 6g The calculation method is as follows:

[0035]

[0036] In the aforementioned low-gravity compensation method for a space robotic arm based on a single-point suspension, to ensure that the torque generated at joints M and N during single-point suspension is equal to the torque generated by the robotic arm on the moon, formulas (1) and (3) are made equal, and formulas (2) and (4) are made equal, thus obtaining:

[0037]

[0038]

[0039] In the aforementioned low-gravity compensation method for a space robotic arm based on a single-point suspension system, the positions of two center-of-gravity adjustment disks are adjusted to transfer the center of gravity of arms A and B. After the center-of-gravity transfer is completed, the overall mass characteristics of the robotic arm change, and the torque M in the ground state changes. OM The calculation method is as follows:

[0040] M OM =m1′ga1′cosα+m2′g(lcosα+b2′sinθ)-F(lcosα+b4sinθ) (7)

[0041] In the formula, m1′ is the weight of boom A component + boom A center of mass adjustment disc;

[0042] m2′ is the weight of boom component B plus the weight of boom B center of gravity adjustment disc;

[0043] a1′ is the distance between the center of mass of arm A component and the center of mass of arm A adjustment disc and the center of shoulder joint;

[0044] b2′ is the distance between the center of mass of component B of the arm and the center of mass of the arm B adjustment disc from the center of the elbow joint.

[0045] Torque M ON The calculation method is as follows:

[0046] M ON =m2′gb2′sinθ-Fb4sinθ (8).

[0047] In the aforementioned low-gravity compensation method for a space robotic arm based on a single-point suspension, to ensure that the torque generated at joints M and N during single-point suspension after the robotic arm's center of mass transfer is equal to the torque generated by the robotic arm on the moon, formulas (7) and (3) are made equal, and formula (8) and (4) are made equal, thus obtaining:

[0048]

[0049]

[0050] In the aforementioned low-gravity compensation method for a space robotic arm based on a single-point suspension system, step four involves setting the center-of-mass position of component B of the arm along its length in the initial orientation of the robotic arm as... The range of the center of mass position along the length of the boom is

[0051] The method for analyzing elbow joint unloading efficiency is as follows:

[0052] With the robotic arm's suspension position and suspension force remaining constant, and assuming the center of mass position of component B of the arm changes after the end effector's pose change, the position of this center of mass is... The torque generated at joint N under 1 / 6 lunar gravity is M. ON1 / 6g The torque generated under actual ground conditions is M. ON The elbow joint unloading efficiency is η N1 Then we get:

[0053]

[0054]

[0055]

[0056] Substituting formulas (11) and (12) into formula (13), we get:

[0057]

[0058] Similarly, after the end effector's pose changes, the position of the center of mass of component B of the boom is... At that time, the unloading efficiency of the elbow joint is:

[0059]

[0060] The range of elbow joint unloading efficiency is:

[0061] when At that time, the unloading efficiency range of the elbow joint is:

[0062]

[0063] Conversely At that time, the unloading efficiency range of the elbow joint is:

[0064]

[0065] Set an elbow joint unloading efficiency threshold; when the elbow joint unloading efficiency is within the elbow joint unloading efficiency threshold, do not correct the running trajectory of the end effector; when the elbow joint unloading efficiency exceeds the elbow joint unloading efficiency threshold, correct the running trajectory of the end effector by changing the starting position of the end effector and reducing the motion envelope of the end effector.

[0066] elbow joint unloading efficiency η N1 η N2 The unloading efficiency η is a quantity independent of α and θ. N1 η N2 It is positively correlated with the centroid deviation caused during the movement of the end effector.

[0067] In the aforementioned low-gravity compensation method for a space robotic arm based on a single-point suspension system, the analysis method for shoulder joint unloading efficiency is as follows:

[0068] With the robotic arm's suspension position and suspension force remaining constant, and assuming the center of mass position of component B of the arm changes after the end effector's pose change, the position of this center of mass is... The torque generated at point M under lunar surface gravity of 1 / 6 is M. OM1 / 6g The torque generated under actual ground conditions is M. OM The elbow joint unloading efficiency is η M1 Then we can conclude that:

[0069]

[0070]

[0071]

[0072] Substituting formulas (18) and (19) into formula (20), we get:

[0073]

[0074] Similarly, it can be concluded that the position of the center of mass of component B of the boom is... The shoulder joint unloading efficiency is:

[0075]

[0076] The range of shoulder joint unloading efficiency is:

[0077] or

[0078] Set a shoulder joint unloading efficiency threshold; when the shoulder joint unloading efficiency is within the shoulder joint unloading efficiency threshold, do not correct the running trajectory of the end effector; when the elbow joint unloading efficiency exceeds the elbow joint unloading efficiency threshold, correct the running trajectory of the end effector by changing the starting position of the end effector and reducing the motion envelope of the end effector.

[0079] In the aforementioned low-gravity compensation method for a space robotic arm based on a single-point suspension system, ε1 and ε2 are coefficients:

[0080]

[0081]

[0082] The advantages of this invention compared to the prior art are:

[0083] (1) This invention realizes the overall single-point suspension gravity unloading of a large-range four-degree-of-freedom spatial robotic arm by establishing an unloading theoretical model; for the motion mechanism coupled by a three-degree-of-freedom rotary joint, the suspension position and suspension tension of the single-point suspension are determined; the center of mass of the robotic arm is transferred by combining the increase of the robotic arm's own weight, thereby avoiding interference and collision between the product itself and the gravity compensation device during the robotic arm deployment test.

[0084] (2) This invention quantifies the range of gravity unloading efficiency of the robotic arm by establishing an unloading efficiency model, providing support and basis for the optimization and correction of the motion trajectory of the end effector. The gravity unloading method can be applied to both mechanical suspension and air suspension methods, solving the problems of interference and collision and large loss of unloading capacity during the ground deployment test of robotic arms with complex motion trajectories;

[0085] (3) The gravity unloading method provided by the present invention can be applied to gravity unloading of robotic arms with multiple degrees of freedom, large range of motion, complex motion trajectory and motion configuration. Attached Figure Description

[0086] Figure 1 This is a flowchart of the single-point suspension gravity unloading method of the present invention;

[0087] Figure 2 This is a diagram showing the configuration of the robotic arm of the present invention;

[0088] Figure 3 This is a force analysis diagram of the single-point suspension of the robotic arm of the present invention;

[0089] Figure 4 This is a schematic diagram of the single-point suspension of the present invention. Detailed Implementation

[0090] The present invention will be further described below with reference to the embodiments.

[0091] This invention provides a low-gravity compensation method for a space robotic arm based on a single-point suspension system. Taking a four-degree-of-freedom lunar space robotic arm as an example, the gravity unloading method is illustrated. The mechanical suspension method applies suspension tension to the robotic arm via slings, while the air suspension method applies suspension tension via the lift of a helium balloon. This gravity unloading method is applicable to both methods, thereby achieving 1 / 6 gravity simulation during the ground deployment test of the space robotic arm. This aims to meet the requirements of adaptive following and high stability control throughout the entire motion process of the robotic arm.

[0092] Low gravity compensation methods for space robotic arms based on a single-point suspension system, such as Figure 1 As shown, the specific steps include the following:

[0093] Step 1: Divide the robotic arm body into arm A component and arm B component; arm A component includes shoulder joint support, shoulder joint, arm A, elbow joint, and elbow joint fixation support; arm B component includes elbow joint output support, arm B, wrist joint support, wrist joint, and end effector.

[0094] The shoulder joint support is connected to the external base joint; the shoulder joint is mounted on the shoulder joint support; one axial end of arm A is connected to the shoulder joint; the other axial end of arm A is connected to the elbow joint fixation support; the elbow joint is mounted on the elbow joint fixation support; the elbow joint output support is connected to the elbow joint fixation support via the elbow joint; one end of arm B is connected to the elbow joint output support; the other end of arm B is connected to the wrist joint support; the wrist joint is mounted on the wrist joint support; the end effector is connected to the wrist joint; wherein, the end effector is considered as a fixed mass block; the position where the relative angle between the axis of the end effector and the axis of arm B is 0° is set as the initial orientation of the end effector, and the overall configuration of the robotic arm is as follows. Figure 2 As shown.

[0095] Define the shoulder joint position as point M and the elbow joint position as point N; calculate the torque M generated at point M when the robotic arm is in any position on the ground. OM The torque M generated at point N ON ; Calculate the torque M generated at point M under lunar surface gravity of 1 / 6. OM1 / 6g The torque M generated at point N ON1 / 6g Using a single-point suspension method for gravity unloading requires ensuring that the compensating torque generated by the robotic arm at the shoulder joint (M) and elbow joint (N) under any configuration is equal to the compensating torque generated under 1 / 6 lunar surface gravity. The force analysis diagram for the single-point suspension of the robotic arm is shown below. Figure 3 As shown.

[0096] Let the initial position of the single-point suspension be b4, and let the suspension force F be F; solve for the expressions of b4 and F.

[0097] When the robotic arm is in any position, the torque generated by the joint at point M is:

[0098] M OM =m1ga1cosα+m2g(lcosα+b2sinθ)-F(lcosα+b4sinθ) (1)

[0099] The torque generated at joint N is:

[0100] M ON =m2gb2sinθ-Fb4sinθ (2)

[0101] The torque generated at joint M under lunar surface gravity of 1 / 6 is:

[0102]

[0103] The torque generated at joint N is:

[0104]

[0105] To ensure that the torque generated at joints M and N during single-point suspension is equal to the torque generated by the robotic arm on the moon, i.e., (1) equals (3), and (2) equals (4), the solution is:

[0106]

[0107]

[0108] Where: m1 is the weight of component A of the boom;

[0109] m2 is the weight of component B of the boom;

[0110] a1 is the distance from the center of mass of component A of the arm bar to the center of the shoulder joint;

[0111] b2 is the distance from the center of mass of the arm-bar assembly A to the center of the elbow joint;

[0112] l is the distance between the centers of the shoulder joint and the elbow joint;

[0113] α is the angle between the axis of arm A and the horizontal plane in any posture;

[0114] θ is the angle between the arm B axis and the vertical plane in any posture;

[0115] F represents the single-point suspension tension;

[0116] b4 is the distance from the suspension position to the center of the elbow joint.

[0117] According to equations (5) and (6), when using a single suspension point, the point of application and the magnitude of the force are quantities independent of α and θ. That is, when the robotic arm moves to any position, the torque generated by the constant tension of the single suspension point on points M and N is always equal to the torque of the robotic arm on points M and N under 1 / 6 of the lunar surface gravity.

[0118] Step 2: Based on the mass characteristics of arm components A and B, the initial suspension position and suspension force of the robotic arm can be determined using the theoretical model from Step 1. If the suspension position is located within the envelope area of ​​the end effector, due to the limited space between the end effector and arm B, interference and collisions may occur between the end effector and the suspension point connection structure or suspension rope (sling) during its rotational movement. Arm A center of gravity adjustment discs and arm B center of gravity adjustment discs are used to transfer the center of gravity of arm components A and B, respectively. To increase the efficiency of center of gravity transfer, both arm A and arm B center of gravity adjustment discs are installed near the elbow joint. See Appendix for details. Figure 4 .

[0119] Step 3: After the robotic arm's center of mass transfer is completed, the overall mass characteristics of the robotic arm change. The suspension point position and suspension force are recalculated using the theoretical model. When the robotic arm is in any position on the ground, the torque generated by the joint at point M is:

[0120] M OM =m1′ga1′cosα+m2′g(lcosα+b2′sinθ)-F(lcosα+b4sinθ) (7)

[0121] The torque generated at joint N is:

[0122] M ON =m2′gb2′sinθ-Fb4sinθ (8)

[0123] The torque generated at joint M under 1 / 6 gravity is:

[0124]

[0125] The torque generated at joint N is:

[0126]

[0127] We can conclude that:

[0128]

[0129]

[0130] Where: m1′ is the weight of (boom A component + boom A center of gravity adjustment disc);

[0131] m2′ is the weight of (boom component B + boom B center of gravity adjustment disc);

[0132] a1′ is the distance from the center of mass of (arm A component + arm A center of mass adjustment disc) to the center of shoulder joint;

[0133] b2′ is the distance from the center of mass of (arm B component + arm B center of mass adjustment disc) to the center of elbow joint;

[0134] After determining the suspension position and suspension force after the center of mass of the robotic arm is transferred, and confirming that the suspension point is outside the envelope area of ​​the end effector, the line of action of the suspension point is obtained. The line of action is perpendicular to the length direction of the arm. A suspension point connection structure is set up, and the suspension point is located on the line of action of the suspension point, realizing the physical connection between the robotic arm body and the sling or rope.

[0135] Step 4: Uninstallation efficiency analysis

[0136] During the actual operation of the robotic arm, the mass characteristics of component B of the arm change as the end effector rotates around the wrist joint axis. Therefore, it is necessary to analyze the unloading efficiency of the robotic arm with 1 / 6 gravity compensation based on the changes in the mass characteristics of component B of the arm. Based on the analysis results, the motion trajectory and range of the end effector can be corrected to ensure that the unloading efficiency meets the requirements.

[0137] A coordinate system is established with the central axis of arm B as the X-axis, the central axis of the elbow joint as the Y-axis, and the intersection of the central axes of arm B and elbow joint as the origin. The end effector is considered a fixed mass block, and the position where the relative angle between the length direction of the end effector and the length direction of the arm is 0° is set as the initial orientation of the end effector. The position of the center of mass of the arm B component in the X-direction at this orientation is set as... During the entire motion of the end effector, the range of the center of mass position of component B in the X direction is as follows: like Figure 4 As shown.

[0138] (1) Elbow joint unloading efficiency analysis:

[0139] If the suspension position and suspension force of the robotic arm remain unchanged, and the position of the center of mass of component B of the arm is assumed to be [value missing] after the end effector pose change. The torque generated at joint N under 1 / 6 lunar gravity is M. ON1 / 6g The torque generated under actual ground conditions is M. ON The elbow joint unloading efficiency is η N1 Then we can conclude that:

[0140]

[0141]

[0142]

[0143] Further conclusions can be drawn:

[0144]

[0145] It can be seen that the unloading efficiency of the elbow joint is a quantity independent of α and θ, and the unloading efficiency is positively correlated with the centroid deviation caused during the movement of the end effector.

[0146] Similarly, it can be concluded that the position of the center of mass of component B of the boom is... The elbow joint unloading efficiency is:

[0147] Therefore when When (b′2, b2, b″2 are all ≥ 0), the unloading efficiency range of the elbow joint is:

[0148]

[0149] Conversely At that time, the unloading efficiency range of the elbow joint is:

[0150]

[0151] (2) Shoulder joint unloading efficiency analysis:

[0152] If the suspension position and suspension force of the robotic arm remain unchanged, and the position of the center of mass of component B of the arm is assumed to be [value missing] after the end effector pose change. The torque generated at point M under lunar surface gravity of 1 / 6 is M. OM1 / 6g The torque generated under actual ground conditions is M. OM The elbow joint unloading efficiency is η M1 Then we can conclude that:

[0153]

[0154]

[0155]

[0156] Further conclusions can be drawn:

[0157]

[0158] set up but:

[0159]

[0160] Similarly, it can be concluded that the position of the center of mass of component B of the boom is... The shoulder joint unloading efficiency is:

[0161]

[0162] set up but:

[0163]

[0164] Therefore, the unloading efficiency range of the robotic arm shoulder joint during the entire motion process of the end effector is:

[0165] or

[0166] It can be seen that the unloading efficiency of the shoulder joint during the entire motion process of the end effector is related to the motion configuration of the robotic arm. At the same time, each robotic arm has a corresponding displacement azimuth angle α and θ, so the unloading efficiency of the shoulder joint under different typical motion configurations of the robotic arm can be obtained.

[0167] Based on the above unloading efficiency model, the range of unloading efficiency for the elbow and shoulder joints during the entire motion process of the robotic arm's end effector can be obtained. If the unloading efficiency does not meet the requirements, the motion trajectory of the end effector can be corrected according to this model. By changing the starting position of the end effector and reducing the motion envelope of the end effector, the gravity unloading efficiency of the robotic arm can be ensured to meet the requirements.

[0168] This invention realizes the overall single-point suspension gravity unloading of a large-range four-degree-of-freedom spatial robotic arm by establishing an unloading theoretical model; for the motion mechanism coupled by a three-degree-of-freedom rotary joint, the suspension position and suspension tension of the single-point suspension are determined; by combining the robotic arm's own weight increase method to transfer the center of mass of the robotic arm, interference and collision between the product itself and the gravity compensation device are avoided during the robotic arm deployment test.

[0169] This invention quantifies the range of gravity unloading efficiency for robotic arms by establishing an unloading efficiency model, providing support and basis for optimizing and correcting the motion trajectory of the end effector. The gravity unloading method is applicable to both mechanical suspension and air suspension methods, solving the problems of interference and collision and significant unloading capacity loss during ground deployment tests of robotic arms with complex motion trajectories.

[0170] The gravity unloading method provided by this invention can be applied to gravity unloading of robotic arms with multiple degrees of freedom, large range of motion, complex motion trajectories and motion configurations.

[0171] Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make possible changes and modifications to the technical solutions of the present invention by utilizing the methods and techniques disclosed above without departing from the spirit and scope of the present invention. Therefore, any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solutions of the present invention shall fall within the protection scope of the technical solutions of the present invention.

Claims

1. A low-gravity compensation method for a space robotic arm based on an overall single-point suspension system, characterized in that: include: Step 1: Divide the robotic arm body into arm A component and arm B component; arm A component includes shoulder joint support, shoulder joint, arm A, elbow joint, and elbow joint fixation support; arm B component includes elbow joint output support, arm B, wrist joint support, wrist joint, and end effector. Define the shoulder joint position as point M and the elbow joint position as point N; calculate the torque generated at point M when the robotic arm is in any position on the ground. The torque generated at point N ; Calculate the torque generated at point M under lunar surface gravity of 1 / 6. The torque generated at point N ; The initial position of the single-point suspension is set as follows: Set the suspension tension for single-point suspension. Solve and The expression; Step 2: If the single-point suspension position is located within the envelope area of ​​the end effector's motion trajectory, install center-of-gravity adjustment discs on both boom A and boom B; install both center-of-gravity adjustment discs near the elbow joint to prevent single-point suspension. Located within the envelope region of the end effector's motion trajectory; Step 3: Calculate the position and suspension pressure of the single-point suspension again using the method in Step 1; after confirming that the suspension point is outside the envelope area of ​​the end effector's motion trajectory, obtain the line of action of the suspension point position, which is perpendicular to the length direction of the arm; realize the physical connection between the robotic arm and the external sling or rope through the suspension point connection structure; at the same time, avoid interference and collision between the robotic arm itself and the external sling or rope and the robotic arm during the movement of the robotic arm. Step 4: Analyze the unloading efficiency of the elbow and shoulder joints. Based on the unloading efficiency of the elbow and shoulder joints, correct the running trajectory of the end effector to ensure that the gravity unloading efficiency of the robotic arm meets the requirements and complete the low gravity compensation of the robotic arm.

2. The low gravity compensation method for a space robotic arm based on an overall single-point suspension method according to claim 1, characterized in that: In step one, the shoulder joint bracket is connected to the external base joint; the shoulder joint is mounted on the shoulder joint bracket; one axial end of arm A is connected to the shoulder joint; the other axial end of arm A is connected to the elbow joint fixation bracket; the elbow joint is mounted on the elbow joint fixation bracket; the elbow joint output bracket is connected to the elbow joint fixation bracket via the elbow joint; one end of arm B is connected to the elbow joint output bracket; the other end of arm B is connected to the wrist joint bracket. The wrist joint is mounted on a wrist joint support; the end effector is connected to the wrist joint; the end effector is considered as a fixed mass block; the position where the relative angle between the axis of the end effector and the axis of arm B is 0° is set as the initial orientation of the end effector.

3. The low gravity compensation method for a space robotic arm based on an overall single-point suspension method according to claim 1, characterized in that: Torque in ground condition The calculation method is as follows: （1） In the formula, The weight of component A of the boom; The weight of component B of the boom; The distance between the center of mass of arm component A and the center of shoulder joint; The distance between the center of mass of the arm-bar assembly A and the center of the elbow joint; The distance between the centers of the shoulder joint and the elbow joint; The angle between the boom A axis and the horizontal plane in any posture; The angle between the B-axis of the boom and the vertical plane under any orientation; For single-point suspension tension; The distance from the suspension position to the center of the elbow joint; It is the acceleration due to gravity; torque The calculation method is as follows: （2）。 4. The low gravity compensation method for a space robotic arm based on an overall single-point suspension method according to claim 3, characterized in that: Under lunar surface gravity of 1 / 6, torque The calculation method is as follows: （3） torque The calculation method is as follows: （4）。 5. The low gravity compensation method for a space robotic arm based on an overall single-point suspension method according to claim 4, characterized in that: To ensure that the torque generated at joints M and N during single-point suspension is equal to the torque generated by the robotic arm on the moon, we make equations (1) and (3) equal, and equations (2) and (4) equal, thus obtaining: （5） （6）。 6. The low gravity compensation method for a space robotic arm based on an overall single-point suspension method according to claim 5, characterized in that: By adjusting the positions of the two center-of-gravity adjustment disks, the center of gravity of boom A and boom B can be transferred. After the center of mass transfer is completed, the overall mass characteristics of the robotic arm change, and the torque in the ground state changes. The calculation method is as follows: （7） In the formula, Weight adjustment disc for boom A component + boom A center of gravity; Adjust the weight of the boom component B + boom B center of gravity adjustment disc; The distance between the center of gravity of the armbar A component and the center of gravity of the armbar A center of gravity adjustment disc and the center of the shoulder joint; The distance between the center of gravity of the B component of the boom and the center of gravity of the B component's center of gravity adjustment disc and the center of the elbow joint; torque The calculation method is as follows: （8）。 7. A low-gravity compensation method for a space robotic arm based on an overall single-point suspension method according to claim 6, characterized in that: To ensure that the torque generated at joints M and N when the robotic arm is suspended from a single point after the center of mass shift is equal to the torque generated by the robotic arm on the moon, we make formula (7) equal to formula (3), and formula (8) equal to formula (4), thus obtaining: （9） （10）。 8. The low gravity compensation method for a space robotic arm based on an overall single-point suspension method according to claim 7, characterized in that: In step four, the position of the centroid of component B of the arm along the length of the arm is set to the initial orientation of the robotic arm. The range of the center of mass position along the length of the boom is [ , ]; The method for analyzing elbow joint unloading efficiency is as follows: With the robotic arm's suspension position and suspension force remaining constant, and assuming the center of mass position of component B of the arm changes after the end effector's pose change, the position of this center of mass is... The torque generated at joint N under 1 / 6 lunar gravity is The torque generated under actual ground conditions is The elbow joint unloading efficiency is Then we get: （11） （12） （13） Substituting formulas (11) and (12) into formula (13), we get: （14） Similarly, after the end effector's pose changes, the position of the center of mass of component B of the boom is... At that time, the unloading efficiency of the elbow joint is: （15） The range of elbow joint unloading efficiency is: when At that time, the unloading efficiency range of the elbow joint is: （16） Conversely At that time, the unloading efficiency range of the elbow joint is: （17） Set an elbow joint unloading efficiency threshold; when the elbow joint unloading efficiency is within the elbow joint unloading efficiency threshold, do not correct the running trajectory of the end effector; when the elbow joint unloading efficiency exceeds the elbow joint unloading efficiency threshold, correct the running trajectory of the end effector by changing the starting position of the end effector and reducing the motion envelope of the end effector. elbow joint unloading efficiency , To and , Irrelevant quantities and unloading efficiency , It is positively correlated with the centroid deviation caused during the movement of the end effector.

9. A low-gravity compensation method for a space robotic arm based on an overall single-point suspension method according to claim 8, characterized in that: The method for analyzing shoulder joint unloading efficiency is as follows: With the robotic arm's suspension position and suspension force remaining constant, and assuming the center of mass position of component B of the arm changes after the end effector's pose change, the position of this center of mass is... The torque generated at joint M under 1 / 6 lunar gravity is The torque generated under actual ground conditions is The shoulder joint unloading efficiency is Then we can conclude that: （18） （19） （20） Substituting formulas (18) and (19) into formula (20), we get: （21） Similarly, it can be concluded that the position of the center of mass of component B of the boom is... The shoulder joint unloading efficiency is: （22） The range of shoulder joint unloading efficiency is: or (twenty three) in, , For coefficients: （24） （25） Set a shoulder joint unloading efficiency threshold; when the shoulder joint unloading efficiency is within the threshold, do not correct the trajectory of the end effector; when the shoulder joint unloading efficiency exceeds the threshold, correct the trajectory of the end effector by changing the starting position of the end effector and reducing the motion envelope of the end effector.

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