A gravity compensation system for three-dimensional motion of space manipulator

Abstract

The present invention relates to the technical field of ground test equipment for aerospace engineering, and in particular to a three-dimensional motion gravity compensation system for a space manipulator. It comprises a compensated manipulator arm, a follower mechanism, a bracket and a wire suspension system, wherein the compensated manipulator arm is arranged at the bottom of the bracket, the follower mechanism is arranged at the top of the bracket, and is connected to the compensated manipulator arm through the wire suspension system; the compensated manipulator arm and the follower mechanism have the same configuration, and the three-dimensional motion gravity compensation of the compensated manipulator arm is achieved by synchronously controlling the motion of the compensated manipulator arm and the follower mechanism. The present invention performs multi-axis and three-dimensional motion gravity compensation on the compensated manipulator arm, so as to achieve the purpose of simulating the microgravity working state of space on the ground.

Description

Technical Field

[0001] The invention relates to the technical field of ground test equipment for aerospace engineering, and in particular to a three-dimensional motion gravity compensation system for a space manipulator. Background Art

[0002] With the continuous development of space exploration activities, space manipulators are becoming more and more effective tools for completing space operation tasks. They can replace astronauts to complete extravehicular operations, greatly reducing the risk of astronauts' extravehicular activities. They can also assist astronauts in completing in-cabin experiments on orbit and reduce the labor intensity of astronauts. The actual working environment of the space manipulator is a microgravity environment. When verifying its motion performance on the ground, it is necessary to construct a microgravity simulation environment for it to verify and evaluate its positioning accuracy, motion speed, operating force, torque and other performance indicators under the actual working state. The methods commonly used for ground gravity compensation of space manipulators include water flotation, air flotation and wire suspension. The water flotation method requires the construction of a dedicated water pool test system, and the compensated manipulator needs to be sealed, which is costly. The air flotation method is usually used for gravity compensation of planar motion mechanisms. For systems like manipulators that have multiple freedoms and move in three-dimensional space, if the air flotation method is used, it is generally necessary to divide the mechanism into several parts and perform motion simulation tests under gravity compensation in different planes separately. During ground testing of space manipulators, long-term motion life tests are required. If the three-dimensional motion of the manipulator is decomposed into several different plane motions and tested separately in air-floating microgravity simulation, it will not only take a huge amount of time, but also fail to fully simulate the dynamic characteristics under microgravity. The wire suspension method is widely used in microgravity simulation. Its advantages are low cost and simple implementation. Its disadvantage is that there may be interference between the wires. Therefore, it is usually difficult to use for three-dimensional motion mechanisms, unless a clever configuration is designed to avoid interference between the wires. The application of the wire suspension method is greatly affected by the specific configuration of the manipulator, and there is no universal solution. In addition, when wire counterweights are used in space manipulators, usually only some joints that are more affected by gravity are counterweighted.

[0003] In response to the ground motion test needs of a small six-degree-of-freedom space robotic arm, a ground microgravity simulation environment is built for it. In order to achieve lightweight and miniaturized design, the motor torque of the space robotic arm is designed according to the load in the microgravity environment. It is necessary to compensate for gravity for the joints whose driving performance is greatly affected by gravity. In order to complete the most comprehensive assessment and testing, the robotic arm needs to perform long-term three-dimensional space motion. At present, there is no ready-made gravity compensation system available. It is necessary to design a gravity compensation system that can be applied to the three-dimensional motion of the robotic arm to assist it in completing multiple test tasks such as ground motion performance testing, fatigue life testing, and function and performance index testing. Summary of the invention

[0004] In view of the above problems, the purpose of the present invention is to provide a three-dimensional motion gravity compensation system for a space robot arm, which performs multi-axis, three-dimensional motion gravity compensation on a space robot arm, thereby achieving the purpose of simulating the microgravity working state in space on the ground.

[0005] In order to achieve the above object, the present invention adopts the following technical solutions:

[0006] A three-dimensional motion gravity compensation system for a space manipulator comprises a compensated manipulator, a follower mechanism, a bracket and a wire suspension system, wherein the compensated manipulator is arranged at the bottom of the bracket, the follower mechanism is arranged at the top of the bracket and connected to the compensated manipulator through the wire suspension system;

[0007] The compensated mechanical arm and the follower mechanism have the same configuration, and the three-dimensional motion gravity compensation of the compensated mechanical arm is achieved by synchronously controlling the motion of the compensated mechanical arm and the follower mechanism.

[0008] The compensated mechanical arm includes six joints which are rotatably connected in sequence.

[0009] The hanging wire suspension system comprises a plurality of hanging wire assemblies, both ends of each hanging wire assembly are respectively connected to the corresponding joints of the compensated mechanical arm and the follower mechanism, and each hanging wire assembly is kept in a vertically stretched state.

[0010] The hanging wire assembly includes a hanging wire, a counterweight, a pulley assembly and a fixed installation assembly, wherein the fixed installation assembly is connected to a joint of the follower mechanism, and the pulley assembly is arranged on the fixed installation assembly;

[0011] The hanging wire passes through a pulley assembly, and one end is connected to a counterweight, and the other end is connected to a joint of the compensated mechanical arm.

[0012] The hanging wire comprises a lower hanging wire and an upper hanging wire, and the lower hanging wire and the upper hanging wire are connected via a tension sensor.

[0013] The other end of the hanging wire is rotatably connected to a non-destructive tooling component, and the non-destructive tooling component is connected to the compensated mechanical arm.

[0014] The hanging wire components are in four groups, and are respectively connected to the output ends of the compensated mechanical arm and the first to fourth joints of the follower mechanism.

[0015] The six joints of the compensated mechanical arm are joint I, joint II, joint III, joint IV, joint V and joint VI, wherein joint I is connected to the bottom of the bracket and can move along an arc trajectory;

[0016] The rotation axis of the joint II is parallel to the rotation axis of the joint I;

[0017] The rotation axis of the joint III is perpendicular to the rotation axis of the joint II;

[0018] The rotation axis of the joints IV and V is parallel to the rotation axis of the joint III;

[0019] The rotation axis of the joint VI is perpendicular to the rotation axis of the joint V.

[0020] The joint III and the joint IV are connected via a first connecting rod; the joint IV and the joint V are connected via a second connecting rod.

[0021] The three-dimensional motion gravity compensation system of the space robot arm also includes an electrically connected control system and a display system, wherein the control system is connected to the compensated robot arm and the follower mechanism.

[0022] The advantages and beneficial effects of the present invention are:

[0023] The present invention has more comprehensive functions: the present invention realizes gravity compensation for a mechanism with four degrees of freedom and three-dimensional motion through an innovative mechanism design.

[0024] The configuration of the present invention is simpler: the follow-up mechanism of the present invention adopts a series arm configuration, which greatly reduces the complexity of the mechanism, improves the reliability of the system, and reduces the control difficulty compared with the traditional overhead crane follow-up mechanism.

[0025] The gravity compensation accuracy of the present invention is higher: the follow-up mechanism and the unloaded mechanical arm have exactly the same configuration, and by controlling the synchronous movement of the two mechanisms, accurate synchronization of each lifting point can be achieved without complex position calculation, thereby significantly improving the dynamic compensation accuracy.

[0026] The operation of the present invention is safer: the hanging wire is connected to the unloaded mechanical arm through non-destructive tooling, thereby avoiding structural damage to the unloaded mechanical arm; and by installing a tension sensor in the hanging wire, the tension of the hanging wire is monitored in real time to prevent damage to the system caused by excessive force caused by synchronous control errors; and current protection and emergency stop functions are set in the control program to achieve multiple protections for the system. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is a structural schematic diagram of the gravity compensation system for three-dimensional motion of a space manipulator of the present invention;

[0028] Figure 2 It is a schematic diagram of the structure of the compensated mechanical arm in the present invention;

[0029] Figure 3 It is a structural schematic diagram of the follower mechanism in the present invention;

[0030] Figure 4 It is a structural schematic diagram of the hanging wire suspension system in the present invention;

[0031] Figure 5 It is a structural schematic diagram of the hanging wire assembly of the present invention.

[0032] In the figure: 1 is the compensated robot arm; 11 is joint I; 12 is joint II; 13 is joint III; 14 is the first connecting rod; 15 is joint IV; 16 is the second connecting rod; 17 is joint V; 18 is joint VI; 2 is the follower mechanism; 21 is the follower joint I; 22 is the follower joint II; 23 is the follower joint III; 24 is the follower joint IV; 3 is the bracket; 4 is the hanging wire suspension system; 41 is the hanging wire assembly I; 42 is the hanging wire assembly II; 43 is the hanging wire assembly III; 44 is the hanging wire assembly IV; 441 is the non-destructive tooling assembly; 442 is the lower hanging wire; 443 is the tension sensor; 444 is the upper hanging wire; 445 is the counterweight; 446 is the pulley assembly; 447 is the fixed installation assembly; 5 is the control system; 6 is the display system. DETAILED DESCRIPTION

[0033] In order to make the purpose, technical solutions and advantages of the present invention more clear, the present invention is described in detail below with reference to the accompanying drawings and specific embodiments.

[0034] like Figure 1 As shown, a spatial manipulator three-dimensional motion gravity compensation system provided by the present invention comprises a compensated manipulator 1, a follower mechanism 2, a bracket 3 and a hanging wire suspension system 4, wherein the bracket 3 provides installation and support functions for the system, the compensated manipulator 1 is arranged at the bottom of the bracket 3, the follower mechanism 2 is arranged at the top of the bracket 3, and is connected to the compensated manipulator 1 through the hanging wire suspension system 4; the compensated manipulator 1 and the follower mechanism 2 have the same configuration, and the motion of the compensated manipulator 1 and the follower mechanism 2 is synchronously controlled to achieve the spatial three-dimensional motion gravity compensation of the compensated manipulator 1. The hanging wire suspension system 4 is used to connect the compensated manipulator 1 and the follower mechanism 2, provide an upward pulling force for the compensated manipulator 1, and eliminate the influence of gravity on its joint drive.

[0035] In the embodiment of the present invention, the compensated robot arm 1 is a six-degree-of-freedom 6R spatial robot arm, including six joints connected in rotation in sequence. Figure 2 As shown, the six joints of the compensated robot arm 1 are joint I11, joint II12, joint III13, joint IV15, joint V17 and joint VI18, wherein joint I11 is connected to the bottom of the bracket 3 and can move along a circular arc trajectory; the rotation axis of joint II12 is parallel to the rotation axis of joint I11, the rotation axis of joint III13 is perpendicular to the rotation axis of joint II12, the rotation axes of joint IV15 and joint V17 are parallel to the rotation axis of joint III13, and the rotation axis of joint VI18 is perpendicular to the rotation axis of joint V17.

[0036] Furthermore, joint III 13 and joint IV 15 are connected by a first connecting rod 14, and joint IV 15 and joint V 17 are connected by a second connecting rod 16, so that the robot arm meets the requirements of the operating space. Hollow wiring is used in the structural design of each joint, and the cables pass through the center holes of each joint to achieve ±180° rotational motion. Joint I 11 provides rotational motion, which is a rotating joint composed of a circular arc guide rail and a ring gear pair. The support and drive design of the circular arc guide rail and the circular arc gear ring can achieve a wide range of reach while making the structure lightweight and high in rigidity.

[0037] In the embodiment of the present invention, the six joints of the compensated mechanical arm 1 are all revolute joints, forming a 6R joint configuration. During the ground motion test, the first four joints of the compensated mechanical arm 1 are greatly affected by gravity and need to be gravity compensated. When performing gravity compensation, joint V17 and joint VI18 remain stationary and are equivalent to a part of the output mechanism of joint IV15. The rotation angles of the first four joints of the compensated mechanical arm 1 are θ1, θ2, θ3, and θ4, respectively. Figure 2 shown.

[0038] like Figure 3 As shown, in the embodiment of the present invention, the follower mechanism 2 has the same configuration as the first four joints of the compensated mechanical arm 1, including a follower joint I 21, a follower joint II 22, a follower joint III 23 and a follower joint IV 24 which are connected in rotation in sequence, and their rotation angles are respectively and Since the configuration and connecting rod size of the follower mechanism 2 are exactly the same as those of the four-degree-of-freedom robot composed of the first four joints of the unloaded robot arm 1, as long as the follower mechanism 2 and the corresponding joints of the compensated robot arm 1 are ensured to move synchronously, the wire suspension system 4 can always be in the vertical direction to achieve high-precision dynamic compensation. Therefore, during the movement of the compensated robot arm 1, the follower mechanism 2 moves synchronously with the compensated robot arm 1, so that the wire always remains in a vertical state, satisfying the multi-axis dynamic compensation function.

[0039] like Figure 4 As shown, in the embodiment of the present invention, the wire suspension system 4 includes a plurality of wire assemblies, both ends of each wire assembly are respectively connected to the corresponding joints of the compensated mechanical arm 1 and the follower mechanism 2, and each wire assembly maintains a vertically stretched state.

[0040] In this embodiment, the hanging wire suspension system 4 includes four groups of hanging wire assemblies, namely, hanging wire assembly I 41, hanging wire assembly II 42, hanging wire assembly III 43 and hanging wire assembly IV 44. The four groups of hanging wire assemblies are respectively connected between the compensated mechanical arm 1 and the first four corresponding joints of the follower mechanism 2, and are respectively used for gravity compensation of the output end mechanism of the 1st to 4th joints of the compensated mechanical arm 1.

[0041] like Figure 5 As shown, in the embodiment of the present invention, the four groups of hanging wire assemblies have the same structure, and all include hanging wires, counterweights 445, pulley assemblies 446, and fixed installation assemblies 447, wherein the fixed installation assemblies 447 are connected to a joint of the follower mechanism 2, and the pulley assemblies 446 are arranged on the fixed installation assemblies 447; the hanging wire passes through the pulley assemblies 446, and one end is connected to the counterweight 445, and the other end is connected to the joint of the compensated mechanical arm 1. The weight of the counterweight 445 is the same as the weight of the compensated mechanism.

[0042] In the embodiment of the present invention, the hanging wire comprises a lower hanging wire 442 and an upper hanging wire 444, and the lower hanging wire 442 and the upper hanging wire 444 are connected via a tension sensor 443, and the tension in the hanging wire is dynamically measured in real time via the tension sensor 443.

[0043] Furthermore, the other end of the hanging wire is rotatably connected to a non-destructive tooling assembly 441, and the non-destructive tooling assembly 441 is connected to the compensated mechanical arm 1. Specifically, the non-destructive tooling assembly 441 is used to connect the corresponding mechanism on the compensated mechanical arm 1, and is connected to the compensated mechanical arm 1 by a clamping ring, thereby avoiding structural damage to the compensated mechanical arm 1, and the upper and lower parts of the non-destructive tooling assembly 441 are connected by a movable hinge, so that when the mechanical arm moves, the hanging wire can always be kept in the vertical direction, and its extension line passes through the center of gravity of the compensated mechanism.

[0044] On the basis of the above-mentioned embodiments, a spatial manipulator three-dimensional motion gravity compensation system provided by the present invention also includes an electrically connected control system 5 and a display system 6, and the control system 5 is connected to the compensated manipulator 1 and the follower mechanism 2. The function of the control system 5 is to plan the motion trajectory and issue motion instructions to the compensated manipulator 1 and the follower mechanism 2 to make them move synchronously. In addition, the joint position, speed, position and tension information of the hanging wire are collected back to the control system in real time, and are processed for storage and display. The display system 6 mainly provides a human-machine interface function, and displays the state of the motion mechanism and the effect of gravity compensation in real time in the form of charts, lines, numbers, etc.

[0045] In this embodiment, the compensated mechanical arm is a spatial six-degree-of-freedom mechanical arm with a 6R series configuration. The first joint is a rotary joint composed of a circular arc guide rail and a ring gear pair, and the last five joints are modular rotary joints. After analysis, the driving performance of the first four joints is greatly affected by the gravity of the mechanism, and gravity compensation is required. The center of gravity of the output mechanism of the last two joints is close to the rotary axis, so the joint driving performance is less affected by the gravity factor and gravity compensation is not required.

[0046] In the embodiment of the present invention, the hanging wire suspension system 4 mainly provides the gravity compensation function of each joint. One end of the hanging wire is located directly above the center of gravity of the output mechanism of the compensated mechanical arm joint, and the other end of the hanging wire is connected to a weight through a pulley to always provide an upward pulling force to the joint, thereby eliminating the influence of gravity on the joint driving performance. A tension sensor is installed on each hanging wire to display the gravity compensation effect in real time. The lower part of the hanging wire is fixedly connected to the compensated mechanical arm through a clamping ring-type non-destructive tooling to avoid structural damage or destruction to the compensated mechanical arm. During gravity compensation, the gravity of the non-destructive tooling is simultaneously compensated to eliminate the disturbance torque caused by the non-destructive tooling to the movement of each joint.

[0047] The present invention proposes a three-dimensional motion gravity compensation system for a space robot arm. It is the first time to propose using a follower mechanism with the same configuration as the compensated robot arm to perform gravity compensation on the space robot arm. It innovatively designs multiple sets of hanging wire suspension systems and connection methods, which not only solves the problem that the hanging wire counterweight method is difficult to apply to gravity compensation of three-dimensional motion mechanisms, but also reduces the difficulty of synchronous control, greatly improves the accuracy of real-time dynamic gravity compensation, and realizes real-time and high-precision gravity compensation of three-dimensional ground motion of the space robot arm at a relatively low cost.

[0048] The above description is only an embodiment of the present invention and is not intended to limit the protection scope of the present invention. Any modification, equivalent replacement, improvement, expansion, etc. made within the spirit and principle of the present invention are included in the protection scope of the present invention.

Claims

1. A three-dimensional motion gravity compensation system for a space manipulator, characterized in that: The invention comprises a compensated mechanical arm (1), a follower mechanism (2), a bracket (3) and a wire suspension system (4), wherein the compensated mechanical arm (1) is arranged at the bottom of the bracket (3), the follower mechanism (2) is arranged at the top of the bracket (3) and is connected to the compensated mechanical arm (1) via the wire suspension system (4); The compensated mechanical arm (1) and the follower mechanism (2) have the same configuration, and the three-dimensional motion gravity compensation of the compensated mechanical arm (1) is achieved by synchronously controlling the motion of the compensated mechanical arm (1) and the follower mechanism (2); The compensated mechanical arm (1) comprises six joints which are connected in rotation in sequence; The wire suspension system (4) comprises a plurality of wire assemblies, the two ends of each wire assembly being respectively connected to the corresponding joints of the compensated mechanical arm (1) and the follower mechanism (2), and each wire assembly is kept in a vertically stretched state; The hanging wire assembly comprises a hanging wire, a counterweight (445), a pulley assembly (446) and a fixed installation assembly (447), wherein the fixed installation assembly (447) is connected to a joint of the follower mechanism (2), and the pulley assembly (446) is arranged on the fixed installation assembly (447); The hanging wire passes through a pulley assembly (446), and one end is connected to a counterweight (445), and the other end is connected to a joint of the compensated mechanical arm (1); The hanging wire comprises a lower hanging wire (442) and an upper hanging wire (444), and the lower hanging wire (442) and the upper hanging wire (444) are connected via a tension sensor (443); The hanging wire components are four groups, and are respectively connected to the output ends of the first to fourth joints of the compensated mechanical arm (1) and the follower mechanism (2); During the movement of the compensated mechanical arm (1), the follower mechanism (2) moves synchronously with the compensated mechanical arm (1), so that the hanging wire always remains in a vertical state, thereby satisfying the multi-axis dynamic compensation function.

2. The three-dimensional motion gravity compensation system of a space manipulator according to claim 1, characterized in that: The other end of the hanging wire is rotatably connected to a non-destructive tooling component (441), and the non-destructive tooling component (441) is connected to the compensated mechanical arm (1).

3. The three-dimensional motion gravity compensation system of a space manipulator according to claim 1, characterized in that: The six joints of the compensated robot arm (1) are joint I (11), joint II (12), joint III (13), joint IV (15), joint V (17) and joint VI (18) in sequence, wherein joint I (11) is connected to the bottom of the bracket (3) and can move along an arc trajectory; The rotation axis of the joint II (12) is parallel to the rotation axis of the joint I (11); The rotation axis of the joint III (13) is perpendicular to the rotation axis of the joint II (12); The rotation axes of the joints IV (15) and V (17) are parallel to the rotation axis of the joint III (13); The rotation axis of the joint VI (18) is perpendicular to the rotation axis of the joint V (17).

4. The three-dimensional motion gravity compensation system of a space manipulator according to claim 3, characterized in that: The joint III (13) and the joint IV (15) are connected via a first connecting rod (14); the joint IV (15) and the joint V (17) are connected via a second connecting rod (16).

5. The three-dimensional motion gravity compensation system of a space manipulator according to any one of claims 1 to 4, characterized in that: It also includes an electrically connected control system (5) and a display system (6), wherein the control system (5) is connected to the compensated mechanical arm (1) and the follower mechanism (2).

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