Ground test method for overall characteristics of space docking mechanism

Abstract

The application relates to the field of spacecraft ground simulation test, and relates to a docking mechanism whole machine characteristic test table which is necessary equipment for docking mechanism development and production, and is mainly used for whole machine performance test and adjustment after docking mechanism assembly, transportation and other whole machine tests. The application provides a docking mechanism whole machine characteristic test method which contains stiffness test, connection and separation resistance test and guiding precision test, explains the test principle and method, and provides a complete test platform construction implementation method based on an industrial mechanical arm and a six-dimensional force sensor.

Description

Technical Field

[0001] This invention relates to the field of spacecraft ground simulation testing, specifically a ground testing method for the overall characteristics of a space docking mechanism. Background Technology

[0002] The space docking mechanism is the executing component for rendezvous and docking in space, used to achieve mechanical docking, docking retention, and separation operations between two spacecraft. Space docking mechanism structures include conical rod type, outward-turned heterogeneous isomorphic peripheral type, inward-turned heterogeneous isomorphic peripheral type, and LIDS, among others. Regardless of the type of docking mechanism, it is a crucial component for the connection and separation of spacecraft, and its performance is subject to high requirements. These requirements include stiffness after connection, drag during connection, guidance accuracy during connection, drag during separation, and guidance accuracy during separation. All these data must be tested during the development of the docking mechanism.

[0003] Industrial robots or robotic arms are mature products, and their six degrees of freedom (DOF) position and posture motion enables them to perform many functions, meeting the application needs of various occasions. Existing six-DOF industrial robots also achieve a high level of operational accuracy, adapting to some high-precision application environments. The use of industrial six-dimensional force sensors in conjunction with robots to complete force servo motion is also a common working mode. The combination of six-dimensional force measurement and six-DOF motion control provides us with a flexible application environment. Summary of the Invention

[0004] This invention proposes a test method for the overall characteristics of a spatial docking mechanism that includes stiffness testing, connection and separation resistance testing, and guidance accuracy testing. It explains the testing principles and methods and provides a complete method for building and implementing a test platform based on an industrial robotic arm and a six-dimensional force sensor.

[0005] The technical solution adopted by the present invention to achieve the above objectives is as follows:

[0006] A ground-based testing method for the overall characteristics of a space docking mechanism, implemented through a testing platform equipped with a robotic arm and a mechanical interface, wherein the mechanical interface is used to set the space docking mechanism to be tested, includes the following steps:

[0007] The gravity compensation parameters of the space docking mechanism under test are calibrated using a robotic arm and a six-dimensional force sensor.

[0008] Perform at least one of stiffness testing, connection separation testing, or guidance accuracy testing, and measure and record the test data in real time using a six-dimensional force sensor.

[0009] The calibration of the gravity compensation parameters of the space docking mechanism under test is specifically as follows: the space docking mechanism under test is moved to N known postures, and M six-dimensional force measurement results are recorded in each of the N known postures. The average value of the M measurement results in each posture is calculated to obtain the six-dimensional force measurement values ​​of the N postures. The least squares method is used to solve for A undetermined coefficients using the N known measurement results.

[0010] The stiffness test specifically includes:

[0011] The robot arm operates the docking mechanism in the space under test and records the amount of robot motion during the operation.

[0012] The combined stiffness test results of the space docking mechanism under test and the test platform are obtained by calculation, namely the relationship between six-dimensional force and deformation.

[0013] The stiffness of the test platform is calibrated to obtain the stiffness of the robotic arm itself.

[0014] By combining the stiffness of the test platform with the stiffness of the test platform itself, the stiffness of the space docking mechanism under test is obtained based on the stiffness series formula.

[0015] The process of calibrating the stiffness of the test platform involves closing the mechanical interface of the test platform and operating the robotic arm while the docking mechanism of the space under test is removed.

[0016] The mechanical interface includes two mounting interfaces. The first mounting interface is connected to the robotic arm, and the second mounting interface is located on the test platform. The first mounting interface and the second mounting interface are adapted to each other and are used to fix the docking mechanism of the space under test.

[0017] The connection separation test specifically includes:

[0018] Load the space docking mechanism under test onto the test platform. The X-axis of the docking mechanism's coordinate system coincides with the X-axis of the test platform's motion system. In the connected state, run the test platform and set the six-dimensional force to 0.

[0019] Drive the docking mechanism of the space under test to move along the X-axis of the test platform kinematic system until it separates from the test platform, and record the six-dimensional force during the separation process;

[0020] Drive the docking mechanism of the space under test to move along the X-axis of the test platform kinematic system until it docks with the test platform, and record the resistance during the connection process.

[0021] The guiding accuracy test specifically includes:

[0022] Load the space docking mechanism under test onto the test platform. The X-axis of the docking mechanism's coordinate system coincides with the X-axis of the test platform's motion system. In the connected state, run the test platform and set the six-dimensional force to 0.

[0023] Drive the docking mechanism under test to move along the X-axis of the test platform's motion system to the guide accuracy test point;

[0024] The space docking mechanism under test is driven to run in the positive Y-axis direction, negative Y-axis direction, positive Z-axis direction, negative Z-axis direction, positive RY-axis direction, negative RY-axis direction, positive RZ-axis direction, and negative RZ-axis direction, respectively. The six-dimensional attitude and six-dimensional force during the operation are recorded. The distance traveled and the single-direction loading result are used as indicators to measure the guidance accuracy.

[0025] A ground-based testing system for the overall characteristics of a space docking mechanism includes a test platform, a robotic arm mounted on the test platform, and a mechanical interface. The mechanical interface is used to mount the space docking mechanism under test. The mechanical interface includes two mounting interfaces: a first mounting interface connected to the robotic arm and a second mounting interface mounted on the test platform. The first and second mounting interfaces are adapted to each other and are used to fix the space docking mechanism under test. A six-dimensional force sensor is installed between the first mounting interface and the robotic arm. The six-dimensional force sensor is used to measure test data during the test process to calibrate the gravity compensation parameters of the space docking mechanism under test, thereby achieving at least one of stiffness testing, connection / separation testing, or guidance accuracy testing.

[0026] The present invention has the following beneficial effects and advantages:

[0027] 1. This invention divides the overall characteristic testing of docking mechanisms into stiffness testing, connection / separation resistance testing, and guidance accuracy testing. Detailed methods for completing these three tests on a single testing device are provided. The testing methods of this invention provide a comprehensive standard for testing the overall characteristics of space docking mechanisms.

[0028] 2. The stiffness calibration process of the test bench itself in this invention can effectively improve the accuracy of the test bench stiffness test, expand the adaptability of the test bench to the product under test, realize the stiffness test of high-stiffness products (the stiffness of the product under test is similar to that of the test bench itself), and increase the stiffness measurement range of the test bench by an order of magnitude. The six-dimensional force gravity compensation of the tested object can enable the test bench to measure the pure loading force, improving the test accuracy.

[0029] 3. This invention has broad compatibility and adaptability for testing products. Testing can be achieved simply by creating adapter fixtures for different products. The testing algorithm is universal; six-dimensional motion control and six-dimensional force measurement for different products can be achieved by modifying parameters. When the system state changes, parameters can be automatically calibrated, and the equipment is easy to use.

[0030] 4. The hardware equipment used in the test platform provided in this invention are all readily available products in modern industry. The use of non-standard parts is limited to a very small range and is easy to reproduce. Attached Figure Description

[0031] Figure 1 This is a flowchart of the testing method of the present invention;

[0032] Figure 2 This is a hardware composition diagram of the present invention;

[0033] Figure 3 This is a stiffness self-calibration state diagram of the present invention;

[0034] Figure 4 This is a diagram of the installation interface of the present invention. Detailed Implementation

[0035] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments.

[0036] The overall characteristic test of the docking mechanism is divided into stiffness test, connection and separation resistance test, and guidance accuracy test.

[0037] The stiffness testing scheme involves establishing a loading state equation and designing a proportional feedback loading controller to implement a six-degree-of-freedom loading function. The procedure is as follows: First, with the docking mechanism connected, the system is used to apply load, and the robot's motion during the loading process is recorded. The combined stiffness test results of the docking mechanism and the test platform are then calculated. Next, a special fixture is used to connect the testing equipment, and the loading model is run to measure the stiffness of the test platform itself. Finally, the stiffness of the docking mechanism is calculated using the combined stiffness and the stiffness of the test platform itself.

[0038] The connection and separation resistance test method is as follows: The space docking mechanism is loaded onto the test equipment and connected. The X-axis of the docking mechanism's coordinate system coincides with the X-axis of the test platform's motion system. While connected, the loading function is run, setting the six-dimensional force load to 0. The test equipment is then driven along the X-axis of the motion system until the docking mechanism is separated, and the six-dimensional force during the separation process is recorded. The equipment is then driven again along the X-axis of the motion system until the docking mechanism is connected, and the resistance during the connection process is recorded.

[0039] The guidance accuracy test method involves loading the space docking mechanism onto the test equipment and connecting the docking mechanism. The X-axis of the docking mechanism's coordinate system coincides with the X-axis of the test platform's motion system. While connected, the loading function is run, setting the six-dimensional force loading to 0. The test equipment is then driven to move along the X-axis of the motion system to the guidance accuracy test point. Loading is then applied in the +Y, -Y, +Z, -Z, +RY, -RY, +RZ, and -RZ directions, respectively. The six-dimensional attitude and six-dimensional force during the loading process are recorded. The distance traveled and the single-direction loading results are used as indicators to measure guidance accuracy.

[0040] In the construction and use of the test bench, the self-stiffness calibration and the six-dimensional force gravity compensation algorithm are two noteworthy technical points.

[0041] The method for calibrating the self-stiffness involves connecting the two mounting interfaces of the test bench using a fixture. The stiffness of the connecting fixture is assumed to be infinite, based on the design and the order of magnitude of the test bench's stiffness. The stiffness data measured under these conditions represents the stiffness of the test bench itself.

[0042] The six-dimensional force gravity compensation algorithm of this invention can automatically calibrate and calculate gravity compensation parameters based on the robot's motion and six-dimensional force measurement results. The algorithm effectively removes the weight of the measured object from the six-dimensional force sensor measurements, yielding pure collision force, tension force, and pressure force. The calibrable parameters include the weight of the measured object, the three-dimensional coordinates of its center of mass, and six zero-drift constants from the six-dimensional force acquisition process. The calibration method involves moving the measured object to 30 known postures on a test platform, recording 1000 six-dimensional force measurements in each of these postures, averaging the 1000 measurements for each posture to obtain the six-dimensional force measurement values ​​for the 30 postures, and then using the least squares method to solve for 10 undetermined coefficients based on these 30 known measurement structures.

[0043] The main hardware equipment of the testing platform specified in this invention includes an industrial robotic arm, a six-dimensional force sensor, a PXI controller, a computer, a mechanical base, and a mechanical interface. The industrial robotic arm, six-dimensional force sensor, mechanical base, and mechanical interface are configured according to... Figure 2 The PXI controller communicates with the robot and the six-dimensional force sensor to perform calculations, while the computer communicates with the PXI controller and provides the user interface.

[0044] The space docking mechanism in this invention is existing technology and can be the space docking mechanism with patent number CN111361767A or CN105151328A.

[0045] like Figure 1 As shown, this invention provides a method for ground-based testing of the overall characteristics of a space docking mechanism.

[0046] Step 1: Prepare for the test.

[0047] Step 1.1: Start the equipment, power on the robot, six-dimensional force sensor, controller, and computer, run the test software, and establish connections.

[0048] Step 1.2: Drive the device to a position that is easy to install, and use a torque wrench to install the docking mechanism to the test bench mounting interface. If necessary, an adapter can be used.

[0049] Step 1.3: Move the test robot with the product under test to an open space, run the self-calibration program to measure the six-dimensional force gravity compensation parameters, and use the parameters as the parameters for this test.

[0050] Step 1.4: Based on the product parameters, set the motion coordinate system to the product mating surface.

[0051] Step 1.5: By combining manual movement with loading movement, slowly and safely connect the active and passive ends of the docking mechanism and calibrate the connection posture.

[0052] Step 2: Three individual tests can be run separately.

[0053] Step 2.1: With the docking mechanism open, move in the set direction and record the six-dimensional force measured during the process.

[0054] Step 2.2: With the docking mechanism open, move to one or more test points designed for the docking mechanism, perform a loading test in the non-movement direction, and record the six-dimensional force measured during the process.

[0055] Step 2.3: With the docking mechanism closed, run the loading program, record the relationship between the six-dimensional force measured during overshoot and the relative pose of the docking mechanism, and analyze and calculate the test results.

[0056] Step 3: End the test.

[0057] Step 3.1: Run the loading mode to uninstall. The uninstallation method is to load the six-dimensional force to a uniform value of 0, start loading, and uninstallation is completed when the device is stable.

[0058] Step 3.2: After unloading is complete, open the locking mechanism of the docking mechanism.

[0059] Step 3.3: Manually move the product under test to the separation position and observe the six-dimensional force measurement results during the movement.

[0060] Step 3.4: Move the test bench to a comfortable disassembly position and remove the product.

[0061] Step 3.5: Run the test bench to the stored posture.

[0062] Step 3.6: Close the software and power off the test bench.

[0063] Figure 2 The hardware composition diagram of the invention is given, with 1 being the test platform base, 2 being the robot, 3 being the six-dimensional force sensor, and 4 being the interface tooling.

[0064] Figure 3 A state diagram for self-stiffness calibration is given, and part No. 5 in the diagram is the connecting tooling.

[0065] Mechanical interfaces are existing technology; this embodiment can employ... Figure 4The structure shown features a mechanical interface consisting of nine M10 threaded holes arranged in a circumference with a diameter of 875 mm. These nine mounting holes are arranged in three groups at 120-degree intervals, with a 10-degree gap between adjacent threaded holes within each group. A 275 mm depth clearance is provided between the three groups of mounting holes.

[0066] This invention is mainly used for overall performance testing and adjustment of the docking mechanism after assembly, transportation, and other overall machine tests. The overall machine characteristic tests cover stiffness testing, motion force testing, accuracy testing, and so on.

Claims

1. A ground-based testing method for the overall characteristics of a space docking mechanism, implemented through a testing platform, wherein the testing platform is equipped with a robotic arm and a mechanical interface, the mechanical interface being used to set up the space docking mechanism to be tested, characterized in that... Includes the following steps: The gravity compensation parameters of the space docking mechanism under test are calibrated using a robotic arm and a six-dimensional force sensor. Perform at least one of stiffness testing, connection separation testing, or guidance accuracy testing, and measure and record the test data in real time through a six-dimensional force sensor. The calibration of the gravity compensation parameters of the space docking mechanism under test is specifically as follows: the space docking mechanism under test is moved to N known postures, and M six-dimensional force measurement results are recorded in each of the N known postures. The average value of the M measurement results in each posture is calculated to obtain the six-dimensional force measurement values ​​of the N postures. The least squares method is used to solve for A undetermined coefficients using the N known measurement results. The stiffness test specifically includes: The robot arm operates the docking mechanism in the space under test and records the amount of robot motion during the operation. The combined stiffness test results of the space docking mechanism under test and the test platform are obtained by calculation, namely the relationship between six-dimensional force and deformation. The stiffness of the test platform is calibrated to obtain the stiffness of the robotic arm itself. By utilizing the combined stiffness and the stiffness of the test platform itself, the stiffness of the space docking mechanism under test is obtained based on the stiffness series formula. The guiding accuracy test specifically includes: Load the space docking mechanism under test onto the test platform. The X-axis of the docking mechanism's coordinate system coincides with the X-axis of the test platform's motion system. In the connected state, run the test platform and set the six-dimensional force to 0. Drive the docking mechanism under test to move along the X-axis of the test platform's motion system to the guide accuracy test point; The space docking mechanism under test is driven to run in the positive Y-axis direction, negative Y-axis direction, positive Z-axis direction, negative Z-axis direction, positive RY-axis direction, negative RY-axis direction, positive RZ-axis direction, and negative RZ-axis direction, respectively. The six-dimensional attitude and six-dimensional force during the operation are recorded. The distance traveled and the single-direction loading result are used as indicators to measure the guidance accuracy.

2. The ground testing method for the overall characteristics of a space docking mechanism according to claim 1, characterized in that, The process of calibrating the stiffness of the test platform involves closing the mechanical interface of the test platform and operating the robotic arm while the docking mechanism of the space under test is removed. The mechanical interface includes two mounting interfaces. The first mounting interface is connected to the robotic arm, and the second mounting interface is located on the test platform. The first mounting interface and the second mounting interface are adapted to each other and are used to fix the docking mechanism of the space under test.

3. The ground testing method for the overall characteristics of a space docking mechanism according to claim 1, characterized in that, The connection separation test specifically includes: Load the space docking mechanism under test onto the test platform. The X-axis of the docking mechanism's coordinate system coincides with the X-axis of the test platform's motion system. In the connected state, run the test platform and set the six-dimensional force to 0. Drive the docking mechanism of the space under test to move along the X-axis of the test platform kinematic system until it separates from the test platform, and record the six-dimensional force during the separation process; Drive the docking mechanism of the space under test to move along the X-axis of the test platform kinematic system until it docks with the test platform, and record the resistance during the connection process.

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