A ground test system and method for an on-orbit assembly robot based on an air flotation platform

Abstract

A ground-based test system and method for an on-orbit assembly robot based on an air-floating platform uses the air-floating platform as support. Two air-floating simulators floating on the platform provide gravity unloading. A robotic arm mounted on one of the air-floating simulators picks up the other air-floating simulator, and the high-tolerance docking joints on the crossbeams of the flexible simulation components mounted on the two air-floating simulators are brought closer together until docking is complete, thereby verifying the auxiliary docking capabilities of the space robotic arm. During this process, the vertical rod of the flexible simulation component is connected to the air-floating simulator at the robotic arm mounting end, providing horizontal flexible damping simulation. By combining different flexible simulation components with the air-floating device, vertical gravity unloading, horizontal controllable force and torque control, and flexible base damping disturbance during robotic arm actuation are simultaneously met, fully simulating the on-orbit working conditions of the space robotic arm and verifying the robotic arm's auxiliary docking capabilities.

Description

Technical Field

[0001] The present invention relates to a ground test system and method for a space robot based on an air-floating platform, and is particularly suitable for ground verification of technologies related to a space robot operating on a flexible base in a scenario of on-orbit assembly of large-area space structures. Background Art

[0002] An on-orbit assembly robot is a special robot used to connect different components in a space orbit to construct a new structure or unit body or other space facilities, or to recombine multiple structures. With the development of space on-orbit assembly robot technology, the demand for its testing and verification is also increasing. The main characteristics of its working conditions are the microgravity environment in which it is located and the flexible base disturbance caused by clinging to large space structures. At present, when conducting verification of related technologies such as robot control, a test system based on a fixed base is generally used. For robots working in a space environment such as on-orbit assembly robots, the cost of direct launch for on-orbit testing is too high, so it is necessary to simulate the space assembly working environment on the ground. However, the fixed base method cannot meet its microgravity and flexible base working conditions requirements. It is necessary to design a test system that can achieve partial gravity unloading on the ground.

[0003] Currently, when conducting ground-based tests of space mechanisms in my country, to achieve vertical gravity unloading, most systems use suspension and air-floating platforms. Suspension test systems are often suitable for large mechanisms with small actuation ranges and slow movements. These systems may experience slow response to the actuation testing requirements of on-orbit assembly robots, and during adjustments, they may experience lateral force disturbances caused by the position of the suspension cables and torsional torque interference caused by the cables, making them unsuitable for on-orbit assembly robot verification. While traditional air-floating platforms can achieve vertical gravity unloading, they cannot provide the controllable offset force and torque control and flexible base vibration damping required during the on-orbit assembly process. These platforms cannot realistically replicate the working conditions faced by on-orbit assembly robots and struggle to meet existing robot-related technical testing requirements.

[0004] In summary, there is an urgent need to develop a ground test system suitable for on-orbit assembly robots that can simultaneously meet the requirements of vertical gravity unloading, horizontal controllable force and torque control, and flexible base damping disturbance during actuation. This system can improve the efficiency and accuracy of verification of related technologies of on-orbit assembly robots by testing their capabilities of picking up, dragging, and docking components in space. Summary of the Invention

[0005] The technology of the present invention solves the problem: Overcoming the shortcomings of the existing technology, providing a ground test system and method suitable for on-orbit assembly robots, while meeting the working condition constraints of vertical gravity unloading, horizontal controllable force and torque control, and flexible base damping disturbance during actuation, for realizing ground testing of on-orbit assembly and docking assembly processes.

[0006] The technical solution of the present invention is: an on-orbit assembly robot ground test system based on an air flotation platform, comprising: an air flotation platform, an air flotation simulator, a flexible simulation part, a robotic arm, a hand-eye recognition camera, a circumferential motion capture camera, an air supply device, and a large-tolerance docking joint;

[0007] The air flotation platform is used to provide overall support for the system; the air flotation simulator is installed on the air flotation platform and is used to move on the air flotation platform to simulate the on-orbit assembly of components or spacecraft; the flexible simulation part is installed on the air flotation simulator and is used to provide the air flotation simulator with horizontal flexible base damping, and is also used to dock with the robotic arm to achieve equivalence with the large flexible time-varying base under on-orbit conditions; the robotic arm is the core actuating component of the entire experimental system and is used to equivalently replicate the on-orbit movements of the space robotic arm; the hand-eye recognition camera is installed at the end of the robotic arm to identify the target to be grasped by the robotic arm, and can cooperate with the robotic arm to recognize the posture and position of the grasped target The circumferential motion capture camera is used to monitor and measure the entire test system, and measures the spatial coordinates and posture of the characteristic target ball under the set reference in the form of a camera array, providing a feedback control basis for the flotation simulator and the robotic arm; the air supply equipment is used to provide compressed air, and the air model formed separates the flotation simulator from the flotation platform, thereby realizing the low-resistance movement of the flotation simulator; the large-tolerance docking joint is installed on the flexible simulation part to verify the docking range of the robotic arm after grasping the component, and by adjusting the maximum tolerance range of the docking joint, the picking and docking capability of the on-orbit assembly robotic arm under different conditions is verified.

[0008] The air-floating platform consists of an air-floating table and a level adjustment device, which is used to provide overall support for the system. The surface of the air-floating table is made of a composite plane composed of cast iron and honeycomb aluminum and is polished. The level adjustment device is located below the air-floating table and is used to adjust the overall flatness and horizontal height of the table.

[0009] There are two air flotation simulators, both of which adopt three degrees of freedom; each air flotation simulator is equipped with an air flotation foot support and a cold air injection device installed laterally.

[0010] The cold air injection device includes eight-directional injection electromagnetic valves to simulate the on-orbit motion state of a spacecraft with three degrees of freedom, namely, two translations and one rotation, on an air-floating platform.

[0011] The large-tolerance docking joint is divided into an active end and a passive end. The active end extends outward and closes by means of a claw to capture the passive end, thereby achieving the effect of expanding the tolerance and capture range, which is used to verify the docking range after the robot arm grasps the component; by adjusting the maximum tolerance range of the docking joint, the picking and docking capabilities of the on-orbit assembly robot arm under different conditions are verified.

[0012] The flexible simulation part includes a simulation part crossbeam and a simulation part vertical rod; one end of the simulation part vertical rod is fixed on the ground, and the other end is in contact with the air flotation simulator, which is used to provide flexible base-like damping in the horizontal direction for the air flotation simulator; the simulation part crossbeam adopts a T-shape, with two groups in total, the first group of simulation part crossbeams together with the robotic arm are fixed on one air flotation simulator, and the second group of simulation part crossbeams are fixed on another air flotation simulator; the active end and the passive end of the large-tolerance butt joint are respectively installed on the two groups of simulation part crossbeams, and with the assistance of the robotic arm, they move closer to the other group of simulation part crossbeams, achieving equivalence with a large-flexibility time-varying base under on-orbit conditions.

[0013] The robotic arm adopts a symmetrical distribution of degrees of freedom and consists of 7 joints, 1 end effector, 2 arm rods, 1 central controller and a set of end six-dimensional force sensing and measurement systems; the configuration of the robotic arm joints adopts a shoulder + elbow + wrist layout, that is, the shoulder rotation joint, shoulder yaw joint, shoulder pitch joint, elbow pitch joint, wrist pitch joint, wrist yaw joint and wrist rotation joint are arranged in sequence from the shoulder to the wrist of the robotic arm, and its end is docked with one end of a set of flexible simulation beams.

[0014] The air supply equipment is used to provide compressed air. The compressed air ejected from the flotation simulator forms an air film between the flotation platform and the flotation simulator, so that the flotation simulator as a whole floats and the flotation simulator is separated from the flotation platform, thereby achieving low-resistance movement of the flotation simulator, which is used to simulate the mechanical environment of on-orbit assembly components and spacecraft in the vacuum environment of space that is basically not subject to interference torque.

[0015] A method for conducting a ground test of an on-orbit assembly robot based on an air-floating platform using the above system comprises:

[0016] All equipment is turned on and on standby. The air supply equipment starts to supply air to the air flotation foot of the air flotation simulator, forming a high-rigidity air film between the air flotation foot and the air flotation platform. The air film is connected to the atmosphere at the inner and outer boundaries of the air flotation foot. The air flotation simulator is separated from the air flotation platform and floats on the air film.

[0017] The circumferential motion capture camera identifies the pre-set target and provides feedback on the position and posture of the existing air flotation simulator;

[0018] The cold air injection device of the flotation simulator is started, and the electromagnetic control on the nozzle opens or closes one or several nozzles according to the program control instructions, thereby obtaining the required control force or control torque, realizing attitude control, and making the flotation simulator enter the predetermined relative position;

[0019] The robotic arm obtains its own position information through feedback from its own encoder and circumferential measurement camera, and obtains the interface information on the crossbeam of the flexible simulation part through the hand-eye recognition camera, and then grasps it; after grasping, the robotic arm end is locked;

[0020] After the robot arm grabs the air flotation simulator, it establishes a rigid-flexible coupling connection and drags the grabbed air flotation simulator closer. The robot arm drags the active and passive ends of the large tolerance butt joint closer to each other and enters the predetermined tolerance capture area.

[0021] The active and passive ends of the large-tolerance butt joint enter the capture range, are connected to each other and locked, and the test ends.

[0022] The advantages of the present invention compared with the prior art are:

[0023] (1) The present invention changes the traditional docking test method by adopting a flexible simulation part, providing controllable offset force and torque control and flexible base vibration damping in the horizontal direction during the on-rail assembly process, effectively simulating the large flexibility and time-varying base conditions faced by the robot arm under the on-rail assembly working condition, and improving the authenticity and credibility of the test system.

[0024] (2) The present invention adopts a combination of a circumferential motion capture camera and a hand-eye recognition camera to provide control feedback information reference for the robotic arm and the flotation simulator at the same time, thereby reducing the recognition error of a single system and improving the test accuracy.

[0025] (3) The present invention achieves a lightweight design by adopting a honeycomb aluminum and cast iron composite air flotation platform surface. Compared with the traditional marble surface, it is lighter and cheaper, so that the experimental device can meet more site requirements and cost-effectiveness requirements, and has better promotion.

[0026] (4) The present invention achieves flexible and variable verification capabilities by adopting large-tolerance butt joints, which can adapt to the verification of on-orbit assembly robots of different sizes, different configurations, and different control algorithms, making the test device more versatile. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 Schematic diagram of the system composition of the present invention; DETAILED DESCRIPTION

[0028] like Figure 1As shown, the present invention provides an on-orbit assembly robot ground test system based on an air flotation platform, comprising an air flotation platform 1, a flexible simulation part, an air flotation simulator 2, a robotic arm 6, a hand-eye recognition camera 7, a circumferential motion capture camera 8, an air supply device 9, and a large-tolerance docking joint 5.

[0029] The air flotation platform is used to provide overall support for the system; the air flotation simulator is installed on the air flotation platform and is used to move on the air flotation platform to simulate the on-orbit assembly of components or spacecraft; the flexible simulation part is installed on the air flotation simulator and is used to provide the air flotation simulator with horizontal flexible base damping, and is also used to dock with the robotic arm to achieve equivalence with the large flexible time-varying base under on-orbit conditions; the robotic arm is the core actuating component of the entire experimental system and is used to equivalently replicate the on-orbit movements of the space robotic arm; the hand-eye recognition camera is installed at the end of the robotic arm to identify the target to be grasped by the robotic arm, and can cooperate with the robotic arm to recognize the posture and position of the grasped target The circumferential motion capture camera is used to monitor and measure the entire test system, and measures the spatial coordinates and posture of the characteristic target ball under the set reference in the form of a camera array, providing a feedback control basis for the flotation simulator and the robotic arm; the air supply equipment is used to provide compressed air, and the air model formed separates the flotation simulator from the flotation platform, thereby realizing the low-resistance movement of the flotation simulator; the large-tolerance docking joint is installed on the flexible simulation part to verify the docking range of the robotic arm after grasping the component, and by adjusting the maximum tolerance range of the docking joint, the picking and docking capability of the on-orbit assembly robotic arm under different conditions is verified.

[0030] The air-floating platform consists of an air-floating table and a level adjustment device, which is used to provide overall support for the system. The surface of the air-floating table is made of a composite plane composed of cast iron and honeycomb aluminum and is polished. The level adjustment device is located below the air-floating table and is used to adjust the overall flatness and horizontal height of the table.

[0031] There are two air flotation simulators, both of which adopt three degrees of freedom; each air flotation simulator is equipped with an air flotation foot support and a cold air injection device installed laterally.

[0032] The cold air injection device includes eight-directional injection electromagnetic valves to simulate the on-orbit motion state of a spacecraft with three degrees of freedom, two translations and one rotation, on an air-floating platform.

[0033] The large-tolerance docking joint is divided into an active end and a passive end. The active end extends outward and closes by means of a claw to capture the passive end, thereby achieving the effect of expanding the tolerance and capture range, which is used to verify the docking range after the robot arm grasps the component; by adjusting the maximum tolerance range of the docking joint, the picking and docking capabilities of the on-orbit assembly robot arm under different conditions are verified.

[0034] The flexible simulation component includes a simulation component crossbeam 4 and a simulation component vertical rod 3; one end of the simulation component vertical rod is fixed on the ground, and the other end is in contact with the flotation simulator, which is used to provide flexible base-like damping in the horizontal direction for the flotation simulator; the simulation component crossbeam adopts a T-shape, with two groups in total, the first group of simulation component crossbeams together with the robotic arm are fixed on one flotation simulator, and the second group of simulation component crossbeams are fixed on another air flotation simulator; the active end and the passive end of the large-tolerance butt joint are respectively installed on the two groups of simulation component crossbeams, and with the assistance of the robotic arm, they move closer to the other group of simulation component crossbeams, achieving equivalence with a large-flexibility time-varying base under on-orbit conditions.

[0035] The robotic arm adopts a symmetrical distribution of degrees of freedom and consists of 7 joints, 1 end effector, 2 arm rods, 1 central controller and a set of end six-dimensional force sensing and measurement systems; the configuration of the robotic arm joints adopts a shoulder + elbow + wrist layout, that is, the shoulder rotation joint, shoulder yaw joint, shoulder pitch joint, elbow pitch joint, wrist pitch joint, wrist yaw joint and wrist rotation joint are arranged in sequence from the shoulder to the wrist of the robotic arm, and its end is docked with one end of a set of flexible simulation beams.

[0036] The air supply equipment is used to provide compressed air. The compressed air ejected from the flotation simulator forms an air film between the flotation platform and the flotation simulator, so that the flotation simulator as a whole floats and the flotation simulator is separated from the flotation platform, thereby achieving low-resistance movement of the flotation simulator, which is used to simulate the mechanical environment of on-orbit assembly components and spacecraft in the vacuum environment of space that is basically not subject to interference torque.

[0037] The present invention also relates to a ground test method for an on-orbit assembly robot based on an air flotation platform, which specifically includes the following steps:

[0038] (1) All equipment is turned on and on standby. The air supply equipment starts to supply air to the air foot of the three-degree-of-freedom air flotation simulator, forming a high-rigidity air film between the air foot and the cast iron platform. The air film is connected to the atmosphere at the inner and outer boundaries of the air foot, creating a zero-gravity, frictionless dynamic environment similar to that in space. Both air flotation simulators are separated from the cast iron platform and float on the air film.

[0039] (2) The circumferential motion capture camera identifies the pre-set target and feeds back the position and posture of the existing air flotation simulator;

[0040] (3) The cold air injection device of the three-degree-of-freedom flotation simulator is started and controlled by the electromagnetic control valve on the nozzle. The control valve opens or closes one or several nozzles according to the instructions of the program control device, thereby obtaining the appropriate control force or control torque to achieve attitude control and make the two flotation simulators enter the predetermined relative position.

[0041] (4) The seven-degree-of-freedom robotic arm obtains its own position information through the feedback of its own encoder and circumferential measurement camera, obtains the interface information on the flexible simulation part through the hand-eye recognition camera, and then grasps it. This process verifies the robotic arm's ability to pick up parts under the flexible base working condition. After grasping, the end of the robotic arm is locked;

[0042] (5) After the robot arm grabs, a rigid-flexible coupling connection is established between the two air-floating simulators, and the grabbed air-floating simulator is dragged close to it. This process verifies the dragging docking capability of the robot arm under the flexible base working condition. The dragging of the robot arm makes the active end and the passive end of the large tolerance docking joint approach each other and enter the predetermined tolerance capture area;

[0043] (6) The active end and the passive end of the large tolerance butt joint enter the capture range, connect with each other, and lock, and the test ends.

[0044] Although the present invention has been disclosed above in terms of preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art may make possible changes and modifications to the technical solutions of the present invention using the technical contents disclosed above without departing from the spirit and scope of the present invention. Therefore, any simple modifications, equivalent changes, and modifications 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 scope of protection of the technical solutions of the present invention.

Claims

1. A ground test system for an on-orbit assembly robot based on an air-floating platform, characterized in that: include: Air flotation platform, air flotation simulator, flexible simulation parts, robotic arm, hand-eye recognition camera, circumferential motion capture camera, air supply equipment and large tolerance docking joints; The air flotation platform is used to provide overall support for the system; the air flotation simulator is installed on the air flotation platform and is used to move on the air flotation platform to simulate the on-orbit assembly of components or spacecraft; the flexible simulation part is installed on the air flotation simulator and is used to provide the air flotation simulator with flexible base damping in the horizontal direction, and is also used to dock with the robotic arm to achieve equivalence with a large flexible time-varying base under on-orbit conditions; the robotic arm is the core actuating component of the entire experimental system and is used to equivalently replicate the on-orbit movements of the space robotic arm; the hand-eye recognition camera is installed at the end of the robotic arm to identify the target to be grasped by the robotic arm, and can cooperate with the robotic arm to identify the posture and position of the grasped target, providing information feedback to the robotic arm; The circumferential motion capture camera is used to monitor and measure the entire test system. The camera array measures the spatial coordinates and posture of the characteristic target sphere under a set reference, providing feedback control for the air flotation simulator and robotic arm. The air supply equipment is used to provide compressed air, and the resulting air model separates the air flotation simulator from the air flotation platform, thereby achieving low-resistance movement of the air flotation simulator. The large-tolerance docking joint is installed on the flexible simulation part to verify the docking range after the robotic arm grasps the component. By adjusting the maximum tolerance range of the docking joint, the picking and docking capabilities of the on-orbit assembly robotic arm under different conditions are verified. There are two air flotation simulators, both with three degrees of freedom; each air flotation simulator is equipped with an air flotation foot support and a cold air injection device installed laterally; The cold air injection device contains eight-directional jet electromagnetic valves to simulate the on-orbit motion state of a spacecraft with three degrees of freedom, two translations and one rotation, on an air-floating platform; The large-tolerance docking joint is divided into an active end and a passive end. The active end extends and closes outwards through a claw method to capture the passive end, thereby expanding the tolerance and capture range. This is used to verify the docking range after the robot arm grasps the component. By adjusting the maximum tolerance range of the docking joint, the picking and docking capabilities of the on-orbit assembly robot arm under different conditions are verified. The flexible simulation part includes a simulation part crossbeam and a simulation part vertical rod; one end of the simulation part vertical rod is fixed on the ground, and the other end is in contact with the air flotation simulator, which is used to provide flexible base-like damping in the horizontal direction for the air flotation simulator; the simulation part crossbeam adopts a T-shape, with two groups in total, the first group of simulation part crossbeams together with the robotic arm are fixed on one air flotation simulator, and the second group of simulation part crossbeams are fixed on another air flotation simulator; the active end and the passive end of the large-tolerance butt joint are respectively installed on the two groups of simulation part crossbeams, and with the assistance of the robotic arm, they move closer to the other group of simulation part crossbeams, achieving equivalence with a large-flexibility time-varying base under on-orbit conditions.

2. The ground test method of an on-orbit assembly robot based on an air-floating platform according to claim 1 is characterized in that: The air-floating platform consists of an air-floating table and a level adjustment device, which is used to provide overall support for the system. The surface of the air-floating table is made of a composite plane composed of cast iron and honeycomb aluminum and is polished. The level adjustment device is located below the air-floating table and is used to adjust the overall flatness and horizontal height of the table.

3. The ground test method of an on-orbit assembly robot based on an air-floating platform according to claim 1 is characterized in that: The robotic arm adopts a symmetrical distribution of degrees of freedom and consists of 7 joints, 1 end effector, 2 arm rods, 1 central controller and a set of end six-dimensional force sensing and measurement systems; the configuration of the robotic arm joints adopts a shoulder + elbow + wrist layout, that is, the shoulder rotation joint, shoulder yaw joint, shoulder pitch joint, elbow pitch joint, wrist pitch joint, wrist yaw joint and wrist rotation joint are arranged in sequence from the shoulder to the wrist of the robotic arm, and its end is docked with one end of a set of flexible simulation beams.

4. The ground test method of an on-orbit assembly robot based on an air-floating platform according to claim 1 is characterized in that: The air supply equipment is used to provide compressed air. The compressed air ejected from the flotation simulator forms an air film between the flotation platform and the flotation simulator, so that the flotation simulator as a whole floats and the flotation simulator is separated from the flotation platform, thereby achieving low-resistance movement of the flotation simulator, which is used to simulate the mechanical environment of on-orbit assembly components and spacecraft in the vacuum environment of space that is basically not subject to interference torque.

5. A method for conducting ground testing of an on-orbit assembly robot based on an air-floating platform using the system of claim 1, characterized in that: include: All equipment is turned on and on standby. The air supply equipment starts to supply air to the air flotation foot of the air flotation simulator, forming a high-rigidity air film between the air flotation foot and the air flotation platform. The air film is connected to the atmosphere at the inner and outer boundaries of the air flotation foot. The air flotation simulator is separated from the air flotation platform and floats on the air film. The circumferential motion capture camera identifies the pre-set target and provides feedback on the position and posture of the existing air flotation simulator; The cold air injection device of the flotation simulator is started, and the electromagnetic control on the nozzle opens or closes one or several nozzles according to the program control instructions, thereby obtaining the required control force or control torque, realizing attitude control, and making the flotation simulator enter the predetermined relative position; The robot arm obtains its own position information through feedback from its own encoder and circumferential measurement camera, and obtains the interface information on the crossbeam of the grasping flexible simulation part through the hand-eye recognition camera, and then grasps it; The end of the robotic arm is locked after grasping; After the robot arm grabs the air flotation simulator, it establishes a rigid-flexible coupling connection and drags the grabbed air flotation simulator closer. The robot arm drags the active and passive ends of the large tolerance butt joint closer to each other and enters the predetermined tolerance capture area. The active and passive ends of the large-tolerance butt joint enter the capture range, are connected to each other and locked, and the test ends.

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