A vertical micro-planet roller screw pair stroke error testing method and device

Abstract

The present application relates to the technical field of testing, in particular to a vertical micro-planet roller screw pair stroke error testing method and device, comprising placing a measured screw pair in a vertical testing station, coaxially clamping a single end of the measured screw pair, and performing zero point calibration; driving the main shaft of the measured screw pair to rotate, synchronously collecting the angular displacement signal of the main shaft, and combining the nominal lead of the measured screw pair to solve the theoretical straight line stroke in real time; controlling the positioning bearing platform to move synchronously in a straight line according to the lead corresponding to the theoretical straight line stroke. Through the vertical measurement architecture, the gravity of the measured screw pair itself and the gravity of the follow-up measurement component are used as the pre-tightening force, so that the transmission surface of the measured screw pair and the nut remains one-way stable adhesion, effectively eliminating the axial gap in the measurement direction, avoiding the position drift problem caused by the un-pre-tightened clearance in the traditional horizontal measurement, and ensuring the continuity, stability and authenticity of the full stroke error measurement.

Description

Technical Field

[0001] This invention relates to the field of testing technology, and in particular to a method and apparatus for testing the stroke error of a vertical micro-planetary roller screw pair. Background Technology

[0002] In recent years, with the accelerated evolution of high-end equipment manufacturing towards miniaturization and precision, especially in cutting-edge fields such as humanoid robot dexterous hands, precision medical devices, and miniature aerospace actuators, the demand for miniature linear transmission components has exploded. Miniature planetary roller screw pairs, due to their high load-bearing capacity and extremely compact structure, are gradually becoming the core transmission components of these high-end micro-systems. Their accuracy directly determines the microscopic positioning accuracy and response sensitivity of the terminal equipment; therefore, it is essential to detect their various key transmission errors. This detection requirement includes not only the overall stroke error of the planetary roller screw pair but also the stroke error measurement of the outer raceway of the miniature screw and the outer raceway of the rollers, thus providing reliable data support for the machining, shaping, and precision assembly of miniature planetary roller screws.

[0003] At present, there is no dedicated stroke error testing method for such micro-sized planetary roller screw pairs and their individual components in the industry. The existing traditional testing system based on medium and large screws has insurmountable technical defects when facing small objects: (1) The traditional method uses double centers to hold the center holes at both ends of the test part for clamping and positioning. However, micro-sized screws and rollers are limited by extremely small physical size and processing technology, and cannot be processed to produce standard center holes, which leads to the failure of traditional clamping and centering methods; (2) Traditional measuring equipment generally adopts a horizontal layout. The unpreloaded clearance in the horizontal state will cause the measuring mechanism to shift position during follow-up, which cannot meet the requirements of high-precision full-stroke continuous measurement; (3) Even if the clearance is forcibly eliminated by traditional mechanical means, the applied preload force can often only be concentrated on one side of the screw. This uneven force state not only cannot truly reflect the stable operation of the screw pair, but also easily causes elastic distortion of small parts or even damages the raceway morphology. Summary of the Invention

[0004] The technical problem solved by this invention is that in related technologies, there are problems such as difficulty in clamping micro-miniature planetary roller screws, easy interference from axial clearance in horizontal measurement, and measurement distortion caused by uneven preload.

[0005] To solve the above-mentioned technical problems, the present invention provides the following technical solution: a method for testing the stroke error of a vertical miniature planetary roller screw pair, comprising:

[0006] Step S1: Place the lead screw pair under test in a vertical testing position, coaxially clamp one end of the lead screw pair under test, and perform zero-point calibration.

[0007] Step S2: Drive the spindle of the tested lead screw pair to rotate, synchronously collect the angular displacement signal of the spindle, and calculate the theoretical linear stroke in real time by combining the nominal lead of the tested lead screw pair.

[0008] Step S3: Control the positioning bearing platform to move synchronously in a straight line according to the lead corresponding to the theoretical straight stroke. At the same time, the air-floating micro-motion platform mounted on the positioning bearing platform is in a floating state through low-friction support and gravity compensation.

[0009] Step S4: Establish the connection between the air-bearing micro-motion platform and the measured lead screw pair in the linear movement direction through the measuring frame, transmit the actual displacement generated by the measured lead screw pair to the air-bearing micro-motion platform, and collect the actual linear displacement signal of the air-bearing micro-motion platform.

[0010] Step S5: Simultaneously extract the theoretical linear travel and the actual linear displacement signals, perform spatiotemporal alignment and difference calculation on the two signals to obtain the travel error, and generate the full-stroke dynamic transmission error curve of the tested lead screw pair.

[0011] As a preferred embodiment of the vertical micro-miniature planetary roller screw pair stroke error testing method of the present invention, in step S1, the weight of the screw pair under test and the weight of the follow-up measuring component are used as preload to ensure that the transmission surface of the screw pair under test and the nut always maintains unidirectional stable contact, thereby eliminating axial clearance in the measurement direction.

[0012] As a preferred embodiment of the vertical micro-miniature planetary roller screw pair stroke error testing method of the present invention, in step S1, the top end of the screw pair under test is non-destructively clamped by a pneumatic clamping device, and the bottom end is clamped by a tailstock.

[0013] As a preferred embodiment of the vertical micro-miniature planetary roller screw pair stroke error testing method of the present invention, the zero point calibration includes moving the drive positioning bearing platform to the stroke start end of the screw pair under test, and synchronously zeroing or setting an initial offset value for the sensor that collects angular displacement and the sensor that collects linear displacement at this position to establish the absolute zero point reference for this full stroke measurement.

[0014] As a preferred embodiment of the vertical micro-miniature planetary roller screw pair stroke error testing method of the present invention, wherein: the formula for calculating the theoretical linear stroke in step S2 is:

[0015] L x =(θ / 2π)P h ,

[0016] Among them, L x P represents the theoretical linear travel, θ represents the acquired spindle angular displacement, and Ph The nominal lead is preset for the test piece.

[0017] As a preferred embodiment of the vertical miniature planetary roller screw pair stroke error testing method of the present invention, wherein: in step S3:

[0018] The air-float micro-motion platform reduces friction through air flotation.

[0019] The constant force output of the constant force mechanism is equal in magnitude and opposite in direction to the total weight of the air-floating micro-motion platform and the follower components, thereby counteracting its own weight in the direction of gravity.

[0020] As a preferred embodiment of the vertical micro-miniature planetary roller screw pair stroke error testing method of the present invention, wherein: in step S4, establishing the connection between the air-bearing micro-motion platform and the screw pair under test includes a first test mode and a second test mode:

[0021] In the first test mode, when performing the comprehensive stroke error test of the lead screw pair under test, the V-block clamping fixture on the measuring frame is connected to the nut of the lead screw pair under test to obtain the actual displacement of the nut.

[0022] In the second test mode, when performing stroke error testing on the outer raceway of a single lead screw shaft or the outer raceway of a roller, the high-precision probe on the measuring frame is directly attached to the outer raceway of the lead screw pair being tested to obtain the actual displacement of the single raceway.

[0023] As a preferred embodiment of the vertical micro-miniature planetary roller screw pair stroke error testing method of the present invention, wherein the calculation formula for the stroke error in step 5 is:

[0024] ΔL=L y -L x =L y -(θ / 2π)P h ,

[0025] Where ΔL is the travel error, L y This represents the actual linear displacement collected.

[0026] A vertical micro-sized planetary roller screw pair stroke error testing device includes a vertical bed and a servo motor on the top of the vertical bed, wherein a circular grating is coaxially mounted on the output shaft of the servo motor.

[0027] A pneumatic clamping device is installed below the circular grating. The pneumatic clamping device is used to coaxially clamp the outer circle of the top end of the test lead screw pair. The measuring frame is installed on the air-bearing micro-motion platform and extends towards the test lead screw pair. One end of the measuring frame is connected to the air-bearing micro-motion platform, and the other end of the measuring frame is connected to the nut of the test lead screw pair or contacts the raceway according to the test mode.

[0028] A laser interference ruler is installed at the bottom of the vertical bed. The laser interference ruler is located directly below the air-bearing micro-motion platform. The laser interference ruler emits a laser beam upwards, which hits the reflector at the bottom of the air-bearing micro-motion platform.

[0029] As a preferred embodiment of the vertical micro-miniature planetary roller screw pair stroke error testing device of the present invention, the circular grating is used to acquire the angular displacement signal of the main shaft in real time, and its rotation axis coincides with the axis of the screw pair under test.

[0030] The beneficial effects of the present invention are as follows: (1) By using the vertical measurement structure, the weight of the lead screw pair under test and the weight of the follow-up measurement component are used as the preload force to keep the transmission surface of the lead screw pair under test and the nut in a stable unidirectional fit, effectively eliminating the axial clearance in the measurement direction, avoiding the positional shift problem caused by the lack of preload clearance in traditional horizontal measurement, and ensuring the continuity, stability and authenticity of the full stroke error measurement; (2) The present invention uses a high-precision pneumatic chuck to clamp one end of the workpiece under test, solving the problem of clamping difficulties caused by the inability to machine the center hole due to the size limitation of micro-small lead screws, and avoiding (3) The invention adopts a double-layer follower architecture. The bottom platform undertakes long stroke coarse positioning and isolates the main driving interference. The air-floating micro-motion platform establishes a higher precision and less interference error measurement environment through air-floating micro-friction support and constant spring gravity compensation. (4) The invention is not only applicable to the measurement of the overall comprehensive stroke error of planetary roller screw pair, but also can independently and accurately extract the individual stroke error of micro-small screw outer raceway and roller outer raceway, providing a multi-dimensional reliable means for the precision machining and shaping and error tracing of planetary roller screw pair. Attached Figure Description

[0031] Figure 1 This is a basic flowchart illustrating a method for testing the stroke error of a vertical micro-planetary roller screw pair, as provided in one embodiment of the present invention.

[0032] Figure 2 This is a schematic diagram of a vertical micro-miniature planetary roller screw pair stroke error testing device provided in one embodiment of the present invention.

[0033] Reference numerals: 1. Servo motor; 2. Circular grating; 3. Pneumatic clamping device; 4. Test lead screw pair; 5. Positioning bearing platform; 6. Measuring frame; 7. Air-bearing micro-motion platform; 8. Tailstock; 9. Laser interference ruler; 10. Vertical bed. Detailed Implementation

[0034] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0035] Example 1, referring to Figure 1 As an embodiment of the present invention, a method for testing the stroke error of a vertical micro-miniature planetary roller screw pair is provided, comprising the following steps.

[0036] Step S1: Place the lead screw assembly 4 to be tested in a vertical testing position, and use the pneumatic clamping device 3 to coaxially clamp one end of the lead screw assembly 4 to be tested, and perform zero-point calibration.

[0037] The preload is achieved by using the weight of the lead screw assembly 4 under test and the weight of the follow-up measuring component as preload, ensuring that the transmission surfaces of the lead screw assembly 4 and the nut maintain a stable unidirectional contact and eliminating axial clearance in the measurement direction. The top end of the lead screw assembly 4 is non-destructively clamped by a pneumatic clamping device 3, while the bottom end is clamped by a tailstock 8. The pneumatic clamping device 3 is used for non-destructive clamping of the top end of the lead screw assembly 4, and the tailstock 8 provides auxiliary support to the bottom end. This clamping method eliminates the need to machine center holes at both ends of the lead screw assembly 4, solving the problem of machining center holes for micro-sized parts due to size limitations.

[0038] The preload is the force required to eliminate axial backlash between the tested lead screw assembly 4 and the nut. The preload originates from the weight of the tested lead screw assembly 4 itself and the weight of the following measuring components, such as the measuring frame 6. In a vertical orientation, this gravity acts downwards along the axial direction, ensuring that the transmission surfaces (i.e., raceway contact surfaces) of the tested lead screw assembly 4 and the nut maintain a stable unidirectional contact. This contact method effectively eliminates axial backlash in the measurement direction, avoiding positional shifts caused by backlash in traditional horizontal measurements.

[0039] In practice, a pneumatic clamping device 3 is used to clamp the outer circle of one end of the tested lead screw pair 4, replacing the traditional method of using two centers to hold the center hole. This coaxial pneumatic clamping not only has high repeatability and positioning accuracy, but also avoids stress damage to the end face of the tiny parts by the centers, successfully solving the problem of being unable to clamp or inaccurately clamping tiny lead screws. At the same time, the gravity in the vertical position is used as a natural preload, replacing the traditional mechanical forced preload, avoiding problems such as one-sided preload concentration, extremely uneven force distribution, and elastic distortion of tiny parts, thus ensuring the accuracy of the measurement and the safety of the parts.

[0040] In this embodiment, the lead screw assembly 4 to be tested is placed at the test station, with its top end coaxially clamped by the pneumatic clamping device 3 and its bottom end clamped by the tailstock 8. In this vertical position, the weight of the lead screw assembly 4 itself and the weight of the follower components such as the measuring frame 6 are used as preload to ensure that the transmission surfaces of the lead screw assembly 4 and the nut always maintain a stable unidirectional fit, thereby eliminating the axial clearance between the lead screw assembly 4 and the nut in the measurement direction.

[0041] Zero-point calibration is performed before executing S2. Zero-point calibration involves moving the drive positioning platform to the beginning of the stroke of the lead screw pair 4 under test. At this position, the sensors for acquiring angular displacement and linear displacement are synchronously zeroed or have initial offset values ​​set, establishing an absolute zero-point reference for this full-stroke measurement. In this embodiment, zero-point calibration eliminates the uncertainty of the system's initial state, ensuring the comparability and accuracy of multiple measurement results, and providing a reliable starting point for generating the full-stroke error curve.

[0042] Step S2: Drive the spindle of the tested lead screw pair 4 to rotate, synchronously acquire the angular displacement signal of the spindle, and calculate the theoretical linear travel in real time by combining the nominal lead of the tested lead screw pair 4; the formula for calculating the theoretical linear travel is:

[0043] L x =(θ / 2π)P h ,

[0044] Among them, L x P represents the theoretical linear travel, θ represents the acquired spindle angular displacement, and P h The nominal lead is preset for the test piece.

[0045] In this embodiment, the vertical testing station is the installation position where the axis of the tested lead screw pair 4 is perpendicular to the horizontal plane, providing a physical basis for gravity preload. The vertical testing station is constructed by a vertical bed 10, with the tested lead screw pair 4 installed vertically, its top end facing upwards and its bottom end facing downwards. Spindle rotation drives the lead screw shaft of the tested lead screw pair 4 to rotate, which is a prerequisite for realizing helical transmission. The spindle rotation is driven by a servo motor 1, which is connected to the tested lead screw pair 4 through a transmission mechanism.

[0046] The angular displacement signal is the angle data of the spindle rotation, used to calculate the theoretical displacement. The angular displacement signal is acquired in real time by a circular grating 2 coaxially mounted on the spindle. The circular grating 2 converts the rotation angle into an electrical signal and transmits it to the host computer system. The theoretical linear travel is the theoretical axial displacement of the lead screw pair calculated based on the principle of screw drive. The host computer system reads the angular displacement data and, combined with the preset nominal lead of the measured part, calculates the theoretical linear travel in real time. Servo motor 1 is started to drive the spindle of the measured lead screw pair 4 to rotate. Simultaneously, the angular displacement signal θ of the spindle is acquired in real time using the coaxially mounted circular grating 2. The host computer system reads this angular displacement data and, combined with the preset nominal lead P of the measured part... h The theoretical linear travel L of the tested lead screw pair 4 is calculated in real time. x .

[0047] Furthermore, the stroke error is the difference between the actual axial displacement and the theoretical displacement. The theoretical axial displacement is calculated from the angular displacement, i.e., the theoretical linear stroke L. x The stroke error curve and various stroke error indicators were obtained through the software of the test device.

[0048] Step S3: Control the positioning support platform 5 to move synchronously in a straight line according to the lead corresponding to the theoretical straight stroke. At the same time, the air-floating micro-motion platform 7 mounted on the positioning support platform 5 is in a floating state through low friction support and gravity compensation.

[0049] In step S3, the air-floating micro-motion platform 7 reduces friction through air floating; and by adjusting the constant force mechanism to output a constant force that is equal in magnitude and opposite in direction to the total weight of the air-floating micro-motion platform 7 and the follower components, it counteracts its own weight in the direction of gravity.

[0050] In this embodiment, the positioning support platform 5 is a basic platform used to support the measuring components and realize long-stroke movement. The positioning support platform 5 is mounted on the vertical bed 10 and controlled by a servo drive system. The positioning support platform 5 performs macroscopic synchronous linear movement according to the theoretical lead, undertaking the task of long-stroke coarse following, ensuring that the measuring components are always within the effective measurement range.

[0051] The air-floating micro-motion platform 7 is a highly sensitive floating platform used to transmit micro-displacements. The air-floating micro-motion platform 7 is mounted on the positioning and support platform 5. The air-floating micro-motion platform 7 achieves low-friction support, eliminating friction in the direction of movement; and through a constant force compensation mechanism, it outputs a constant force equal in magnitude and opposite in direction to the total weight of the air-floating micro-motion platform 7 and the measuring frame, thus counteracting its own weight in the direction of gravity. In one embodiment, the constant force compensation mechanism is a constant force spring. The constant force spring achieves constant force by applying a constant force equal to its weight to the air-floating micro-motion platform 7. The difference between a constant force spring and an ordinary spring is that its force variation does not conform to Hooke's law, meaning that it maintains the same force within a certain range of travel.

[0052] The floating state refers to the state in which the air-floating micro-motion platform 7 is unaffected by friction and its own weight in the direction of movement, and can freely respond to minute displacements. The air-floating micro-motion platform 7 is in a floating state of micro-friction and micro-gravity, and can sensitively respond to the microscopic actual displacement generated by the measured lead screw pair 4. Micro-friction is a friction state with extremely small values ​​(close to zero), and micro-gravity is the state in which the gravity acting on the air-floating micro-motion platform in the vertical direction and the air film support force it receives reach a high degree of static equilibrium.

[0053] In practice, the positioning platform 5 undertakes long-stroke coarse positioning, isolating the main driving interference; the air-bearing micro-motion platform 7, through air-bearing micro-friction support and constant spring gravity compensation, separates the error interference from the follower mechanism, guide rail, bed, etc. This dual-layer test bench measurement architecture establishes a higher precision and less interference error measurement environment, ensuring the fidelity of micro-displacement transmission.

[0054] While the main shaft rotates, the bottom positioning support platform 5 is controlled to move synchronously in a macroscopic manner according to the above-mentioned theoretical lead, undertaking the coarse following of the long stroke. At the same time, the air-bearing micro-motion platform 7 installed inside the positioning support platform 5 reduces friction through air buoyancy and counteracts its own weight in the direction of gravity through a constant force compensation device.

[0055] Step S4: Establish the connection between the air-bearing micro-motion platform 7 and the measured lead screw pair 4 in the linear movement direction through the measuring frame 6, transmit the actual displacement generated by the measured lead screw pair 4 to the air-bearing micro-motion platform 7, and collect the actual linear displacement signal of the air-bearing micro-motion platform 7.

[0056] In step S4, establishing the connection between the air-float micro-motion platform 7 and the outer raceway stroke error test includes a first test mode and a second test mode:

[0057] In the first test mode, when the comprehensive stroke error test of the lead screw pair 4 is performed, the V-block clamping fixture on the measuring frame 6 is connected to the nut of the lead screw pair 4 to obtain the actual displacement of the nut; different V-block clamping fixtures are used depending on the diameter of the nut, and the V-block clamping fixture is inside the measuring frame 6.

[0058] In the second test mode, when performing stroke error testing on the outer raceway of a single lead screw shaft or the outer raceway of a roller, the high-precision probe on the measuring frame 6 is directly attached to the outer raceway of the part being tested to obtain the actual displacement of the single raceway.

[0059] When performing the comprehensive stroke error test on the tested lead screw assembly 4 (first test mode), the tested lead screw assembly 4 is clamped in place, and the measuring frame 6 is connected to the nut. After starting the test, the servo motor 1 drives the lead screw to rotate, and the nut moves axially. The positioning bearing platform 5 follows synchronously, and the air-bearing micro-motion platform 7 is in a floating state. The movement of the nut is transmitted to the air-bearing micro-motion platform 7 through the measuring frame 6, and the laser interferometer 9 collects the actual displacement. The host computer system calculates the error in real time and generates a curve.

[0060] When performing a single-unit lead screw shaft outer raceway stroke error test (second test mode), the lead screw shaft is clamped as the test piece, and the probe on the measuring frame 6 is placed against the outer raceway of the lead screw shaft. As the lead screw rotates, the probe moves relative to the raceway, and the shape error of the raceway causes the probe to produce axial micro-motion. This micro-motion is transmitted to the air-bearing micro-motion platform 7 through the measuring frame 6, and the laser interferometer 9 collects this micro-motion displacement. The host computer system calculates the difference between this displacement and the theoretical displacement to obtain the raceway stroke error.

[0061] In this embodiment, the measuring frame 6 is a mechanical structure used to connect the air-bearing micro-motion platform 7 and the tested lead screw pair 4. One end of the measuring frame 6 is connected to the air-bearing micro-motion platform 7, and the other end is connected to the tested lead screw pair 4 according to the testing requirements. The measuring frame 6 defines the connection relationship in the linear movement direction as the axial displacement of the tested lead screw pair 4 being transmitted to the air-bearing micro-motion platform 7 through the measuring frame 6.

[0062] The actual linear displacement signal is the real displacement data generated by the air-bearing micro-motion platform 7 as it follows the movement of the measured lead screw pair 4. The actual linear displacement signal is acquired by a laser interference ruler 9. The laser interference ruler 9 is arranged at the bottom and emits an upward laser beam that hits the reflector of the air-bearing micro-motion platform 7, acquiring the actual linear displacement signal of the platform in real time and at high frequency.

[0063] In practical implementation, by changing the connection between the measuring frame 6 and the tested lead screw pair 4, this method is not only applicable to the measurement of the overall comprehensive stroke error of the planetary roller lead screw pair, but also can independently and accurately extract the individual stroke errors of the micro-sized lead screw outer raceway and roller outer raceway. This breaks the limitation of traditional equipment that can only measure the stroke error of the lead screw and lead screw pair but cannot measure smaller rollers, providing a multi-dimensional and reliable means for the precision machining and shaping and error tracing of planetary roller lead screw pairs. By establishing the connection between the air-bearing micro-motion platform 7 and the tested lead screw pair 4 through the measuring frame 6 in the linear movement direction, the air-bearing micro-motion platform 7 is always in a floating state of micro-friction and micro-gravity.

[0064] Step S5: Synchronously extract the theoretical linear travel and actual linear displacement signals, perform spatiotemporal alignment and difference calculation on the two signals to obtain the travel error, and generate the full-stroke dynamic transmission error curve of the tested lead screw pair 4.

[0065] The formula for calculating the travel error in step 5 is:

[0066] ΔL=L y -L x =L y -(θ / 2π)P h ,

[0067] Where ΔL is the travel error, L y This represents the actual linear displacement collected.

[0068] In this embodiment, the clock reference is a time reference source used for synchronously acquiring multiple signals. Under a unified high-frequency clock reference, the host computer system synchronously extracts the theoretical linear travel generated by the circular grating 2 link and the actual linear displacement acquired by the laser interferometer 9 link.

[0069] Spatiotemporal alignment is a process that eliminates the time difference and spatial starting point difference between the two signals. The system performs spatiotemporal synchronization processing on the two signals to ensure that the theoretical values ​​and actual values ​​correspond one-to-one in time and space.

[0070] The actual displacement in the direction of movement generated by the tested lead screw pair 4 during the rotary feed process is transmitted to the air-bearing micro-motion platform 7 through the measuring frame 6. The laser interference scale 9 arranged at the bottom emits a laser beam upward, which strikes the reflector of the air-bearing micro-motion platform 7, and the actual linear displacement signal L of the air-bearing micro-motion platform 7 is acquired in real time and at high frequency. y .

[0071] Under a unified high-frequency clock reference, the host computer system extracts the theoretical linear travel L generated by the circular grating 2-link. x And the actual linear displacement L acquired by the laser interferometer scale 9 link. y The system performs spatiotemporal synchronization and difference calculation on the two signals to obtain the stroke error. By continuously recording and fitting this difference, the full-stroke dynamic transmission error curve and key accuracy indicators of the tested micro-planetary roller screw pair can be generated.

[0072] The full-stroke dynamic transmission error curve is a continuous curve showing how the stroke error changes with the stroke position. The system generates the full-stroke dynamic transmission error curve and key accuracy indicators of the tested micro-planetary roller screw pair by continuously recording and fitting the differences.

[0073] In practice, the host computer system obtains continuous stroke error data through high-frequency acquisition and real-time calculation. This method overcomes the shortcomings of not being able to meet the requirement of continuous measurement of the entire stroke due to the lack of pre-tightened clearance in the horizontal position, and achieves more accurate dynamic measurement. It effectively solves the current industry problem of not being able to perform high-fidelity full-stroke measurement of micro-sized planetary roller screw pairs.

[0074] This invention achieves high-precision, full-stroke, and dynamic error testing of micro-sized planetary roller screw pairs and their individual components through a vertical measurement architecture, gravity preload, a double-layer follower platform, and a multi-mode connection design. This method effectively solves technical bottlenecks such as the difficulty in clamping tiny parts, large backlash interference, and susceptibility to damage from preload, providing a new and reliable means for performance evaluation of micro-sized high-precision transmission components.

[0075] Example 2, refer to Figure 2In another embodiment of the present invention, based on the previous embodiment, this embodiment differs from the first embodiment in that it provides a vertical miniature planetary roller screw pair stroke error testing device, including a vertical bed 10 and a servo motor 1 on the top of the vertical bed 10. A circular grating 2 is coaxially mounted on the output shaft of the servo motor 1. A pneumatic clamping device 3 is mounted below the circular grating 2, which is used to coaxially clamp the outer circle of the top end of the screw pair 4 under test. A measuring frame 6 is mounted on an air-bearing micro-motion platform 7 and extends towards the screw pair 4 under test. One end of the measuring frame 6 is connected to the air-bearing micro-motion platform 7, and the other end of the measuring frame 6 is connected to the nut of the screw pair 4 under test or contacts the raceway, depending on the test mode. A laser interference ruler 9 is mounted at the bottom of the vertical bed 10, located directly below the air-bearing micro-motion platform 7. The laser interference ruler 9 emits a laser beam upward, which strikes a reflector at the bottom of the air-bearing micro-motion platform 7. The circular grating 2 is used to acquire the angular displacement signal of the spindle in real time, and its rotation axis coincides with the axis of the lead screw pair 4 being measured.

[0076] In this embodiment, a vertical bed 10 serves as the overall support foundation. The vertical bed 10 is placed vertically, with its axis perpendicular to the horizontal plane, providing rigid support and installation reference for the entire testing system. All functional components are arranged sequentially from top to bottom along the vertical direction, forming a vertical measurement architecture. The servo motor 1 is mounted in the top area of ​​the vertical bed 10, serving as the drive source for the spindle rotation. The output shaft of the servo motor 1 extends downwards along the vertical direction.

[0077] Furthermore, the circular grating 2 is coaxially mounted on the output shaft of the servo motor 1, located between the servo motor 1 and the pneumatic clamping device 3. The circular grating 2 is used to acquire the angular displacement signal of the spindle in real time, and its rotation axis coincides with the axis of the lead screw pair 4 being measured.

[0078] Furthermore, the pneumatic clamping device 3 is installed below the circular grating 2 and fixed to the upper part of the vertical bed 10. The clamping center of the pneumatic clamping device 3 is located on the vertical axis and is used to coaxially clamp the outer circle of the top end of the lead screw assembly 4 under test. The lead screw assembly 4 under test is installed along the vertical axis, with its top end clamped by the pneumatic clamping device 3 and its bottom end supported by the tailstock 8. The lead screw assembly 4 under test is suspended in the vertical position, and its own weight acts downward along the axis.

[0079] Furthermore, the tailstock 8 is located below the bottom of the lead screw assembly 4 being tested and is installed in the lower area of ​​the vertical bed 10. The tailstock 8 is used to assist in supporting the bottom end of the lead screw assembly 4 being tested, and together with the pneumatic clamping device 3 at the top, it forms a stable clamping state.

[0080] Furthermore, the positioning bearing platform 5 is installed in the middle area of ​​the vertical bed 10, located on one side of the lead screw pair 4 being measured. The positioning bearing platform 5 can move vertically along the guide rails of the vertical bed 10, undertaking long-stroke coarse following tasks.

[0081] Furthermore, the air-bearing micro-motion platform 7 is mounted on the positioning support platform 5 and located between the positioning support platform 5 and the tested lead screw pair 4. The air-bearing micro-motion platform 7 is suspended on the positioning support platform 5 and is in a floating state, used to transmit micro-displacements.

[0082] Furthermore, the measuring frame 6 is mounted on the air-bearing micro-motion platform 7 and extends towards the lead screw assembly 4 under test. One end of the measuring frame 6 is connected to the air-bearing micro-motion platform 7, and the other end is connected to the nut of the lead screw assembly 4 under test or contacts the raceway, depending on the test mode, to establish a connection in the linear movement direction.

[0083] Furthermore, the laser interference ruler 9 is installed at the bottom of the vertical bed 10, directly below the air-bearing micro-motion platform 7. The laser interference ruler 9 emits a laser beam upwards, which strikes a reflector at the bottom of the air-bearing micro-motion platform 7, and is used to acquire the actual linear displacement signal of the air-bearing micro-motion platform 7 in real time.

[0084] Furthermore, the positioning bearing platform 5 and the air-bearing micro-motion platform 7 are located on one side of the lead screw pair 4 under test, and are connected to the lead screw pair 4 under test through the measuring frame 6; the laser interference ruler 9 is located at the bottom and measures the displacement of the air-bearing micro-motion platform 7 upwards.

[0085] Furthermore, the vertical layout allows the gravity of the tested lead screw assembly 4 and the follow-up measuring components to act downwards along the axial direction, forming a natural and uniform preload force, effectively eliminating axial clearance and providing a basic condition for high-precision measurement.

[0086] This embodiment provides an experimental verification of a method for testing the stroke error of a vertical micro-planetary roller screw pair. This verification aims to demonstrate the effectiveness of the technology used in this method and to confirm its actual effectiveness.

[0087] In this embodiment, the method of the present invention is used to measure the overall error of the entire stroke of a miniature planetary roller screw pair with a length of 150 mm. The main parameters of the miniature planetary roller screw pair are shown in Table 1 below:

[0088] Table 1: Main parameters of miniature planetary roller screw pairs.

[0089] parameter numerical values <![CDATA[Nominal diameter d0 (mm)]]> 4.0 <![CDATA[Lead P h (mm)]]> 2.0 Effective thread length of the lead screw (mm) 100

[0090] The measurement using this method specifically includes the following:

[0091] The micro-planetary roller screw assembly to be tested is placed in the test station, with the top end coaxially clamped by the pneumatic clamping device 3 and the bottom end clamped by the tailstock 8. In this vertical position, the weight of the screw assembly 4 under test and the weight of the follower components such as the measuring frame 6 are used as preload to eliminate axial backlash in the measurement direction.

[0092] The servo motor 1 is started to drive the tested lead screw pair 4 to rotate, initiating the dynamic following test. At a certain high-frequency sampling point during the dynamic test, the circular grating 2 measures the spindle angular displacement θ = 180°. Based on the formula, the theoretical linear travel L is calculated. x =1.0000mm.

[0093] The positioning support platform 5 at the bottom layer is controlled to move in a macroscopic synchronous linear motion according to the theoretical guide; at the same time, the air-floating micro-motion platform 7 mounted on the positioning support platform 5 and the constant force compensation device achieve a floating and following state with micro-friction and micro-gravity.

[0094] The actual linear displacement of the air-floating micro-motion platform 7 was synchronously acquired by the laser interference ruler 9, and was L. y =1.0015mm.

[0095] Under a unified high-frequency clock reference, the host computer system performs difference calculations on the two signals to obtain the stroke error ΔL = +0.0015mm at this position. By continuously acquiring and fitting this difference ΔL at high frequency, the full-stroke dynamic transmission error curve of this miniature planetary roller screw pair can be generated.

[0096] This method enables full-stroke dynamic travel error measurement of miniature planetary roller screw pairs. Compared to traditional horizontal measurement systems, it overcomes the drawback of not being able to meet the requirement of continuous full-stroke measurement due to the lack of preload clearance in the horizontal position. Furthermore, by utilizing gravity as the preload force of the screw pair in a vertical position, it solves the problems of unilateral preload concentration, extremely uneven force distribution, and elastic distortion of small parts caused by the forced preload of traditional horizontal mechanical systems. This method achieves higher accuracy measurement while ensuring the continuity and accuracy of the measurement, effectively solving the current industry problem of being unable to perform high-fidelity full-stroke measurement of miniature planetary roller screw pairs.

Claims

1. A method for testing the stroke error of a vertical miniature planetary roller screw pair, characterized in that, include: Step S1: Place the lead screw pair (4) under test in a vertical test position, coaxially clamp one end of the lead screw pair (4) under test, and perform zero-point calibration. Step S2: Drive the spindle of the tested lead screw pair (4) to rotate, synchronously collect the angular displacement signal of the spindle, and calculate the theoretical linear stroke in real time by combining the nominal lead of the tested lead screw pair (4). Step S3, control the positioning bearing platform (5) to move synchronously in a straight line according to the lead corresponding to the theoretical straight stroke, while the air-floating micro-motion platform (7) mounted on the positioning bearing platform (5) is in a floating state through low friction support and gravity compensation; Step S4: Establish the connection between the air-floating micro-motion platform (7) and the measured lead screw pair (4) in the linear movement direction through the measuring frame (6), transmit the actual displacement generated by the measured lead screw pair (4) to the air-floating micro-motion platform (7), and collect the actual linear displacement signal of the air-floating micro-motion platform (7); Step S5: Simultaneously extract the theoretical linear stroke and the actual linear displacement signal, perform time-space alignment and difference calculation on the two signals to obtain the stroke error, and generate the full stroke dynamic transmission error curve of the tested lead screw pair (4).

2. The method for testing the stroke error of a vertical miniature planetary roller screw pair as described in claim 1, characterized in that: In step S1, the weight of the lead screw pair (4) under test and the weight of the follow-up measuring component are used as the preload force to ensure that the transmission surface of the lead screw pair (4) under test and the nut always maintains a stable unidirectional fit, thus eliminating axial clearance in the measurement direction.

3. The method for testing the stroke error of a vertical miniature planetary roller screw pair as described in claim 1, characterized in that: In step S1, the top end of the test lead screw pair (4) is non-destructively clamped by a pneumatic clamping device (3) and the bottom end is clamped by a tailstock (8).

4. The method for testing the stroke error of a vertical miniature planetary roller screw pair as described in claim 1, characterized in that: The zero-point calibration in step S1 includes moving the drive positioning bearing platform (5) to the beginning of the stroke of the lead screw pair (4) under test, and at this position, synchronously clearing or setting the initial offset value of the sensor for collecting angular displacement and the sensor for collecting linear displacement, and establishing the absolute zero-point reference for this full stroke measurement.

5. The method for testing the stroke error of a vertical miniature planetary roller screw pair as described in claim 1, characterized in that: The formula for calculating the theoretical straight-line travel in step S2 is as follows: L x =(θ / 2π)P h , Among them, L x P represents the theoretical linear travel, θ represents the acquired spindle angular displacement, and P h The nominal lead is preset for the test piece.

6. The method for testing the stroke error of a vertical miniature planetary roller screw pair as described in claim 5, characterized in that: In step S3, the air-floating micro-motion platform (7) reduces friction through air floating; and by adjusting the constant force mechanism to output a constant force that is equal in magnitude and opposite in direction to the total weight of the air-floating micro-motion platform (7) and the follower components, it counteracts its own weight in the direction of gravity.

7. The method for testing the stroke error of a vertical miniature planetary roller screw pair as described in claim 6, characterized in that: In step S4, establishing the connection between the air-float micro-motion platform (7) and the tested lead screw pair (4) includes a first test mode and a second test mode: In the first test mode, when the comprehensive stroke error test of the lead screw pair (4) is carried out, the V-block clamping fixture on the measuring frame (6) is connected to the nut of the lead screw pair (4) to obtain the actual displacement of the nut. In the second test mode, when performing the stroke error test of the outer raceway of a single screw shaft or the outer raceway of a roller, the high-precision probe on the measuring frame (6) is directly attached to the outer raceway of the screw pair (4) being tested to obtain the actual displacement of the single raceway.

8. The method for testing the stroke error of a vertical miniature planetary roller screw pair as described in claim 7, characterized in that: The formula for calculating the travel error in step 5 is as follows: ΔL=L y -L x =L y -(θ / 2π)P h , Where ΔL is the travel error, L y This represents the actual linear displacement collected.

9. A vertical miniature planetary roller screw pair stroke error testing device, characterized in that, Includes a vertical bed (10) and a servo motor (1) on top of the vertical bed (10), wherein a circular grating (2) is coaxially mounted on the output shaft of the servo motor (1). A pneumatic clamping device (3) is installed below the circular grating (2). The pneumatic clamping device (3) is used to coaxially clamp the top outer circle of the test lead screw pair (4). The measuring frame (6) is installed on the air-floating micro-motion platform (7) and extends towards the test lead screw pair (4). One end of the measuring frame (6) is connected to the air-floating micro-motion platform (7), and the other end of the measuring frame (6) is connected to the nut of the test lead screw pair (4) or in contact with the raceway according to the test mode. The vertical bed 10 is equipped with a laser interference ruler (9) at the bottom. The laser interference ruler (9) is located directly below the air-floating micro-motion platform (7). The laser interference ruler (9) emits a laser beam upwards and hits the reflector at the bottom of the air-floating micro-motion platform (7).

10. The vertical miniature planetary roller screw pair stroke error testing device as described in claim 9, characterized in that: The circular grating (2) is used to acquire the angular displacement signal of the main shaft in real time, and its rotation axis coincides with the axis of the lead screw pair (4) being measured.

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