Testing method for terminal motion trajectory of space deployment mechanism

Abstract

The present invention relates to a method for testing the motion trajectory of a spatial deployment mechanism's terminal end, comprising the following steps: a. establishing the relationship between the terminal housing and the terminal axis of the spatial deployment mechanism; b. calibrating the relationship between a fixed reference and a test table; and c. conducting a motion test on the spatial deployment mechanism to calculate the vibration, velocity, acceleration, and error of the terminal end. This method enables high-precision, automated, and rapid measurement of the motion trajectory curve and motion of a multi-degree-of-freedom spatial manipulator.

Description

Technical Field

[0001] The invention relates to a method for testing a terminal motion trajectory of a space deployment mechanism. Background Art

[0002] A space manipulator is a specialized robot that performs missions in space, including space station construction and operational support, satellite assembly and servicing, and planetary exploration and experimentation. Depending on the mission they perform, space manipulators can be categorized into two types: on-orbit manipulators and planetary exploration manipulators. On-orbit manipulators perform tasks such as on-orbit assembly, maintenance, inspection, and assisting astronauts. Planetary exploration manipulators perform patrol maneuvers, sample collection, scientific measurement, and assisting astronauts in exploration.

[0003] The space manipulator is generally a multi-degree-of-freedom serial configuration, mainly composed of three parts: the manipulator joint, the arm assembly and the end effector. Depending on the space structure and the requirements of the operation, the number of degrees of freedom of the space manipulator and its supporting joints can be 4 to 7. It can be seen that the multi-degree-of-freedom space manipulator is a complex system with strong systematization, and the joints and arm interfaces are highly matched. It has the characteristics of large arm envelope size, weak product rigidity and complex motion trajectory. At the same time, complex space missions also require the manipulator to have good flexibility and high posture control accuracy. Therefore, in order to ensure the success of the mission, the space manipulator needs to undergo a large number of functional and performance tests during the ground testing phase, and the manipulator's motion trajectory curve, vibration, speed and acceleration must be tested and analyzed.

[0004] In existing technology, the end-of-arm motion trajectory testing of a space manipulator is primarily accomplished through contact measurement using a single laser tracker to manually capture target points. This method is extremely inefficient and lacks guaranteed accuracy. Therefore, there is an urgent need to design a manipulator end-of-arm motion trajectory testing and calculation method that can meet the requirements for efficient and high-precision testing of the end-of-arm motion trajectory curve, vibration, velocity, and acceleration of a multi-degree-of-freedom space manipulator. Summary of the Invention

[0005] The purpose of the present invention is to provide a method for testing the motion trajectory of the terminal end of a space deployment mechanism.

[0006] To achieve the above-mentioned object of the invention, the present invention provides a method for testing the motion trajectory of the terminal end of a space deployment mechanism, comprising the following steps:

[0007] a. Establish the relationship between the end shell and the end axis of the spatial deployment mechanism;

[0008] b. Calibrate the relationship between the fixed reference and the test table;

[0009] c. Conduct motion tests on the spatial deployment mechanism and calculate the vibration amount, velocity, acceleration and their errors at the end.

[0010] According to one aspect of the present invention, during the assembly process of the spatial deployment mechanism, the fixed reference is calibrated to the target point of the support structure, and the end axis target point of the spatial deployment mechanism is calibrated to the end housing target point.

[0011] According to one aspect of the present invention, in step (a), a dynamic target sphere is set on the end shell target point of the space deployment mechanism, and then a laser tracker is used to establish the relationship between the dynamic target sphere and the end axis target point, and the relationship between the end shell target point and the end axis target point is calibrated.

[0012] According to one aspect of the present invention, before the functional performance test, the target point of the support structure is restored to the fixed reference, and the target point of the end shell is restored to the target point of the end axis.

[0013] According to one aspect of the present invention, in step (b), target points are set on the fixed reference and the test table, and the relationship between the target point of the fixed reference and the target point of the test table is calibrated;

[0014] The target point on the test table is used as a reference for the fixed reference, and a laser tracker is used to establish a fixed reference coordinate system.

[0015] According to one aspect of the present invention, in step (c), before conducting a motion test on the spatial deployment mechanism, a laser tracker is used to unify the target point of the measurement table to a fixed reference coordinate system, and the laser tracker is used to pull the end axis target point.

[0016] According to one aspect of the present invention, in step (c), the moving coordinates of the dynamic target ball are dynamically collected to obtain a coordinate point cloud;

[0017] The coordinate point cloud of the dynamic target ball is converted into a point cloud in a fixed reference coordinate system to obtain the motion trajectory curve. The conversion model is:

[0018]

[0019] Among them, TrackerCal is the device coordinate system, △x, △y, and △z are the offsets between the device coordinate system and the fixed reference coordinate system in three directions; x T 、y T 、z T is the coordinate axis of the device coordinate system; ε is the angle between the device coordinate system and the corresponding coordinate axis of the fixed reference coordinate system;

[0020] According to one aspect of the present invention, the time domain data of the Z coordinate value of the end motion trajectory is subjected to Fourier transformation and modulo, and the horizontal axis and vertical axis of the spectrum are calculated to obtain a spectrum diagram and vibration amount;

[0021] Among them, the sampling frequency F S The sampling frequency is 1000Hz, and the number of sampling points N is 4096 points as a unit;

[0022] The calculation model of velocity and acceleration is:

[0023]

[0024]

[0025] Where v(n) is the velocity at point n; a(n) is the acceleration at point n; Δt is the time interval, △v(n) is the velocity difference between the n+mth point and the nmth point; Δs(n) is the distance between the nmth point and the n+mth point. The calculation formula is:

[0026]

[0027] The error transfer functions of velocity and acceleration are established as follows:

[0028]

[0029] as well as

[0030]

[0031] The error analysis models of velocity and acceleration obtained by transformation are:

[0032]

[0033] as well as

[0034]

[0035] Where i = 1, 2; P = 2, Xi is the input, X1 is Δs(n), X2 is Δ(t), Y is the output, i.e. v(n), k is the sampling frequency; Δs is the displacement; u is the measurement uncertainty;

[0036] According to one aspect of the present invention, two laser trackers are used for transfer measurement, and a TTL data synchronization system is used to provide pulse trigger signals to the two laser trackers to synchronously control the two laser trackers.

[0037] According to one aspect of the present invention, the space deployment mechanism is a space manipulator;

[0038] The test object of the method is the end effector of the space manipulator, and the supporting structure is the support vehicle of the space manipulator;

[0039] The space manipulator further comprises a shoulder yaw joint, a shoulder pitch joint, a first arm, an elbow pitch joint, a second arm and a wrist pitch joint connected in sequence;

[0040] The end effector is arranged on the wrist pitch joint, and the shoulder yaw joint is arranged on the support vehicle.

[0041] According to one solution of the present invention, dual laser trackers are used in conjunction with a TTL data synchronization system for testing, and corresponding solution methods are used to calculate the vibration, velocity, acceleration, and errors during the motion process, thereby improving measurement accuracy and efficiency. This allows for high-precision, automated, and rapid measurement of multi-degree-of-freedom spatial robotic arm motion trajectory curves and motion quantities, overcoming the shortcomings of existing single-laser tracker manual contact measurement, which suffers from poor accuracy and low efficiency.

[0042] According to one solution of the present invention, the test accuracy of the test method is less than 0.08mm, the vibration measurement accuracy is less than 0.2mm, the speed measurement error is less than 0.3mm / s, and the acceleration measurement accuracy is less than 0.3mm / s. 2 , and can be applied to various types of space deployment mechanism products and equipment with motion trajectory curve, vibration, speed, and acceleration test requirements. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 A flow chart schematically illustrating a method for testing the motion trajectory of the terminal end of a space deployment mechanism according to an embodiment of the present invention;

[0044] Figure 2 A structural diagram schematically shows a four-degree-of-freedom serial spatial robot according to an embodiment of the present invention. DETAILED DESCRIPTION

[0045] To more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be derived from these drawings without inventive effort.

[0046] When describing the embodiments of the present invention, the orientation or positional relationship expressed by the terms "longitudinal", "transverse", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside" and "outside" are based on the orientation or positional relationship shown in the relevant drawings. They are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operate in a specific orientation. Therefore, the above terms should not be understood as limiting the present invention.

[0047] The present invention will be described in detail below with reference to the accompanying drawings and specific embodiments. The embodiments cannot be described one by one here, but the embodiments of the present invention are not limited to the following embodiments.

[0048] See also Figure 1 and Figure 2 The present invention's method for measuring the motion trajectory of the end effector of a large, multi-degree-of-freedom space deployment mechanism is applicable to ground testing of various space deployment mechanisms requiring motion trajectory curves, vibration, velocity, and acceleration. This trajectory measurement method requires obtaining the motion trajectory of the end effector's coordinate system relative to a fixed reference for the space deployment mechanism. Therefore, establishing a fixed reference and acquiring real-time position information of the end effector's axis are necessary to provide basic data for dynamic tracking measurement of the space deployment mechanism's motion testing.

[0049] First, it is necessary to establish the relationship between the end shell and the end axis of the space deployment mechanism. During the assembly process of the space deployment mechanism, the fixed reference (whole arm reference) is calibrated to the target point of the support structure (i.e., the target seat), and the end axis target point of the space deployment mechanism is calibrated to the end shell target point. Specifically, a dynamic target ball (a component of the laser tracker) is set on the target points at two different positions of the end shell of the space deployment mechanism, so that the tracking of its axis can be achieved. The laser tracker is then used to establish the relationship between the dynamic target ball and the end axis target point to calibrate the relationship between the end shell target point and the end axis target point, thereby establishing the relationship between the end shell target point and the axis through the dynamic target ball.

[0050] Before the functional performance test, the target point of the support structure needs to be restored to the fixed reference (a surface of the support structure), and the target point of the end shell needs to be restored to the target point of the end axis. Specifically, since the fixed reference of the spatial deployment mechanism is blocked after assembly, it is necessary to stick several targets on the fixed reference and the test table (the platform surface where the mechanism is placed or the surface with unchanged positional relationship) before assembly, calculate and calibrate the relationship between the target point of the fixed reference and the target point of the test table, and thus calibrate the relationship between the fixed reference and the test table. In this way, the target point of the test table can be used as a reference for the fixed reference, providing a reference for establishing a fixed reference coordinate system for the laser tracker (i.e., the test instrument).

[0051] Subsequently, a motion test can be carried out on the space deployment mechanism in order to calculate the vibration amount, velocity, acceleration and its error at the end. Of course, before carrying out a motion test on the space deployment mechanism, it is necessary to first use two laser trackers to unify the target points on the measuring table to a fixed reference coordinate system, and use two laser trackers to pull (i.e., collect) the target points on the end axis respectively. During the dynamic tracking measurement process, the moving coordinates of the dynamic target ball are dynamically collected to obtain a coordinate point cloud. The coordinate point cloud of the dynamic target ball dynamically measured under the laser tracker is converted into a point cloud in a fixed reference coordinate system to obtain a motion trajectory curve. The conversion model is:

[0052]

[0053] Among them, TrackerCal is the device coordinate system, △x, △y, and △z are the offsets between the device coordinate system and the fixed reference coordinate system in three directions; x T 、y T 、z T is the coordinate axis of the device coordinate system; ε is the angle between the device coordinate system and the corresponding coordinate axis of the fixed reference coordinate system;

[0054] After the motion test is completed, the vibration, velocity and acceleration can be calculated. Specifically, the present invention adds the sampling time information (i.e., collecting t, x, y, z), so that the vibration value during the movement of the terminal of the space unfolding mechanism can be calculated. First, the object of the vibration analysis is set to the Z coordinate value of the terminal motion trajectory, and the time domain data (waveform) of the Z coordinate value is Fourier transformed and modulo-modulated to calculate the horizontal and vertical axes of the corresponding spectrum to obtain the spectrum diagram and vibration amount. Among them, the sampling frequency F S The sampling frequency is 1000 Hz, and the number of sampling points N is 4096 points as a unit.

[0055] At the same time, due to the addition of sampling time information (i.e., collecting t, x, y, z), it is possible to establish a calculation model for the speed and acceleration of the end motion of the spatial deployment mechanism, as well as an error model, and perform error analysis to obtain the corresponding speed values, acceleration values, and corresponding error values. The calculation model for speed and acceleration is:

[0056]

[0057]

[0058] Where v(n) is the velocity at point n; a(n) is the acceleration at point n; Δt is the time interval, △v(n) is the velocity difference between the n+mth point and the nmth point; Δs(n) is the distance between the nmth point and the n+mth point. The calculation formula is:

[0059]

[0060] From the above, we can see that the velocity and acceleration of the present invention are obtained by indirect calculation, while the actual measured quantities are displacement Δs and time interval Δt. Therefore, the error transfer functions of velocity and acceleration are established as follows:

[0061]

[0062] as well as

[0063]

[0064] The error analysis models of velocity and acceleration obtained by transformation are:

[0065]

[0066] as well as

[0067]

[0068]

[0069] Where i = 1, 2; P = 2, Xi is the input, X1 is Δs(n), X2 is Δ(t), Y is the output, i.e. v(n), k is the sampling frequency; Δs is the displacement; u is the measurement uncertainty;

[0070] It can be seen that in u Δs(n) 、u Δt Under the premise of being determined by actual measurement, u v(n) and Proportional to, approximately proportional to v(n); in u Δs(n) 、u Δt If you are sure, u a(n) and Directly proportional to, approximately proportional to 2a(n).

[0071] In the present invention, two laser trackers can be used for transfer measurements during actual measurements. To address the time difference between data acquisition by multiple laser trackers, the present invention uses a TTL data synchronization system to provide pulse trigger signals to the two laser trackers, thereby synchronously controlling the two laser trackers and ensuring data acquisition at the same time, thereby reducing measurement errors introduced by asynchronous data acquisition between the two devices.

[0072] In the present invention, the spatial deployment mechanism is a four-degree-of-freedom spatial manipulator. The test object of this method is the spatial manipulator's end effector 8, and the supporting structure is the spatial manipulator's support vehicle 9. Furthermore, the spatial manipulator comprises a shoulder yaw joint 2, a shoulder pitch joint 3, a first arm 4, an elbow pitch joint 5, a second arm 6, and a wrist pitch joint 7, which are connected in sequence. The end effector 8 is mounted on the wrist pitch joint 7, and the shoulder yaw joint 2 is mounted on the support vehicle 9.

[0073] The above description is merely one embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art will readily appreciate that the present invention is susceptible to various modifications and variations. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention shall be included within the scope of protection of the present invention.

Claims

1. A method for testing the motion trajectory of the terminal end of a space deployment mechanism, comprising the following steps: a. Establish the relationship between the end shell and the end axis of the spatial deployment mechanism; b. Calibrate the relationship between the fixed reference and the test table; c. Conduct motion tests on the space deployment mechanism and calculate the vibration, velocity, acceleration and error of the terminal; The time domain data of the Z coordinate value of the end motion trajectory is subjected to fast Fourier transform and modulo, and the horizontal and vertical axes of the spectrum are calculated to obtain the spectrum diagram and vibration amount; Among them, the sampling frequency F S The sampling frequency is 1000Hz, and the number of sampling points N is 4096 points as a unit; The calculation model of velocity and acceleration is: Where v(n) is the velocity at point n; a(n) is the acceleration at point n; Δt is the time interval, △v(n) is the velocity difference between point n+m and point nm; Δs(n) is the distance between the nmth point and the n+mth point, and the calculation formula is: The error transfer functions of velocity and acceleration are established as follows: as well as The error analysis models of velocity and acceleration obtained by transformation are: as well as Where i = 1, 2; P = 2, Xi is the input, X1 is Δs(n), X2 is Δ(t), Y is the output, i.e. v(n), k is the sampling frequency; Δs is the displacement; u is the measurement uncertainty; Two laser trackers are used for transfer measurement, and a data synchronization system is used to provide pulse trigger signals to the two laser trackers to synchronously control the two laser trackers.

2. The method according to claim 1, characterized in that During the assembly process of the space deployment mechanism, the fixed reference is calibrated to the target point of the support structure, and the end axis target point of the space deployment mechanism is calibrated to the end shell target point.

3. The method according to claim 2, characterized in that In step a, a dynamic target ball is set on the end shell target point of the space deployment mechanism, and then a laser tracker is used to establish the relationship between the dynamic target ball and the end axis target point, and the relationship between the end shell target point and the end axis target point is calibrated.

4. The method according to claim 2, characterized in that Before the functional performance test, the target point of the support structure is restored to the fixed reference, and the target point of the end shell is restored to the target point of the end axis.

5. The method according to claim 4, characterized in that In step b, target points are set on the fixed reference and the test table, and the relationship between the target point of the fixed reference and the target point of the test table is calibrated; The target point on the test table is used as a reference for the fixed reference, and a laser tracker is used to establish a fixed reference coordinate system.

6. The method according to claim 5, characterized in that In the step c, before carrying out the motion test on the space deployment mechanism, the target point of the measuring table is unified to the fixed reference coordinate system using a laser tracker, and the terminal axis target point is pulled using the laser tracker.

7. The method according to claim 6, characterized in that In the step c, the moving coordinates of the dynamic target ball are dynamically collected to obtain a coordinate point cloud; The coordinate point cloud of the dynamic target ball is converted into a point cloud in a fixed reference coordinate system to obtain the motion trajectory curve. The conversion model is: Among them, TrackerCal is the device coordinate system, △x, △y, and △z are the offsets between the device coordinate system and the fixed reference coordinate system in three directions; x T 、y T 、z T is the coordinate axis of the device coordinate system; ε is the angle between the device coordinate system and the corresponding coordinate axis of the fixed reference coordinate system.

8. The method according to claim 1, characterized in that The space deployment mechanism is a space manipulator; The test object of the method is the end effector (8) of the space robot arm, and the supporting structure is the support vehicle (9) of the space robot arm; The space manipulator further comprises a shoulder yaw joint (2), a shoulder pitch joint (3), a first arm (4), an elbow pitch joint (5), a second arm (6) and a wrist pitch joint (7) which are connected in sequence; The end effector (8) is arranged on the wrist pitch joint (7), and the shoulder yaw joint (2) is arranged on the support vehicle (9).

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