CN111855183A - A multi-degree-of-freedom motion branch chain resolution test platform and test method - Google Patents

Abstract

The invention discloses a multi-degree-of-freedom motion branched chain resolution test platform and a test method, belonging to the technical field of machinery, and can directly measure the radial runout error of a bearing located in the motion branched chain and the resolution of the multi-degree-of-freedom motion platform motion branched chain Rate. Including: laser displacement meter; fixing device; straight beam type flexible hinge connected with the fixing device; moving platform fixedly connected with the straight beam type flexible hinge; The upper end is connected to the lower end surface of the moving platform through a flexible ball hinge, and the lower end is connected to the fixing device through a Hooke hinge; the laser displacement meter is placed above the moving platform; the fixing device has five fixing points, which are symmetrically distributed; The beam-type flexible hinge and the moving platform are integrally processed and formed, and the straight beam-type flexible hinge and the fixing device are connected by a ball-head screw and a spring; the Hooke hinge is respectively connected with the fixing device and the moving platform by screws.

Description

A multi-degree-of-freedom motion branch chain resolution test platform and test method

technical field

The invention belongs to the technical field of machinery, and in particular relates to a multi-degree-of-freedom motion branched chain resolution test platform and a test method.

Background technique

The multi-degree-of-freedom motion branch chain is the main component of various parallel kinematic mechanisms including the 6-DOF motion platform. The precision requirements of the platform are also getting higher and higher. Due to the relatively high displacement output accuracy of the current high-precision motor, the error of the multi-degree-of-freedom parallel kinematics mechanism is mainly due to the multi-degree-of-freedom shafting design of the Hooke hinge at the connection between the motion branch and the table. However, due to the special structural limitation of Hooke hinges, the traditional shafting error measurement method is useless to test the motion accuracy of Hooke hinges. Therefore, there is currently no domestic research on the motion branches of multi-degree-of-freedom mechanisms and the motion accuracy of Hooke hinges. Related special research, considering that the accuracy of multi-degree-of-freedom kinematic mechanisms mainly depends on the motion accuracy of each kinematic branch, so in the process of multi-degree-of-freedom kinematic mechanism design and research, it is necessary to first systematically study its kinematic branches.

The flexible motion mechanism is different from the traditional rigid motion mechanism, and its motion has the characteristics of continuity, so it has the characteristics of infinitely small motion resolution.

SUMMARY OF THE INVENTION

The invention mainly provides a multi-degree-of-freedom motion branch chain resolution test platform and a test method, which can directly measure the motion accuracy of the multi-degree-of-freedom motion platform motion branch chain. The test platform has a simple and compact structure, and the test method is efficient and accurate.

In order to achieve the above purpose, the technical solution adopted in the present invention is: a multi-degree-of-freedom motion branched chain resolution test platform, comprising: a laser displacement meter; a fixing device; a straight beam type flexible hinge connected with the fixing device; a moving platform fixedly connected with a flexible hinge; and a linear drive assembly arranged between the fixing device and the moving platform; the upper end of the linear drive assembly is connected with the lower end surface of the moving platform through a flexible ball hinge, and the lower end is connected with the fixing device through a Hooke hinge; the There are four straight beam type flexible hinges, which are symmetrically and evenly distributed with the moving platform as the center; the laser displacement meter is placed above the moving platform, and the test point is the center point of the moving platform; the fixing device has five fixed points, symmetrically distributed , four threaded holes are evenly distributed on each fixation; the straight beam type flexible hinge and the moving platform are integrally processed and formed; the upper end surface of the fixing device has a spherical counterbore, and the ball head screw passes through the straight beam type flexible hinge , the ball head is placed in the countersunk hole to adjust the connection position, the spring is placed between the fixing device and the flexible hinge to connect the two; the center of the lower end face of the moving platform is installed with a flexible spherical hinge support; the Hooke The hinges are respectively connected with the upper end face of the fixing device and the lower end face of the moving platform through screws.

Among them, the flexible ball hinge structure adopted is a spherical incision type, with three degrees of freedom, and can be deflected at any angle and direction to meet the installation of five different fixed points.

A multi-degree-of-freedom motion branched chain resolution test method, using the above-mentioned multi-degree-of-freedom motion branched chain resolution test platform, the test method is carried out in two steps:

The first step is to first give an input displacement curve to the nanoscale calibration linear displacement driver. The linear drive component transmits the displacement curve to the moving platform. The laser displacement meter can obtain the linear drive component by measuring the displacement curves of the four symmetrical points on the moving platform. During the movement of the linear drive assembly, if there is no bearing radial runout, the output displacement curve will be smooth, continuous and unique, but due to the existence of the bearing radial runout error, the output displacement curve is no longer smooth and continuous. Moreover, the displacement of the linear drive is nm, and the error caused by the radial runout of the bearing inside the Hooke hinge is μm, so the radial runout error of the bearing can be easily distinguished through finite element simulation and experimental calibration. During the test process, due to the characteristics of straight beam flexible hinge and flexible ball hinge without gap and friction, the continuity of output displacement is ensured, so that the measurement result has only one variable, which is the radial runout error caused by the internal bearing of the Hook hinge; Since the Hook hinge has two degrees of freedom, and each Hook hinge has two sets of bearings inside, it is necessary to measure the displacement error of more than two degrees of freedom, so five fixed points are set on the fixing device, and one is set in the center of the fixing device. The fixed point, the other four fixed points are symmetrically and evenly distributed with the middle fixed point as the center, and the displacement measurement with five degrees of freedom not only meets the measurement requirements of the two degrees of freedom of the Hooke hinge, but also solves the problem of the angle of the straight beam flexible hinge. The problem of limited measurement range caused by the small size increases the measurement range. When the linear drive components are placed in different fixed positions, the vertical height difference is reduced. achieve the ideal height difference;

The second step is to replace the nanoscale calibrated linear displacement driver with the motion branch of the multi-degree-of-freedom parallel motion platform to be measured, and measure the motion resolution of its five degrees of freedom.

The beneficial effects of the present invention are:

(1) The multi-degree-of-freedom motion branch chain resolution test platform and test method of the present invention use a laser displacement meter to measure the output displacement, the measurement method is simple, direct and efficient, and the measurement results are accurate and easy to analyze.

(2) The multi-degree-of-freedom motion branched chain resolution test platform of the present invention adopts a straight beam type flexible hinge, which has the advantages of no friction, no gap, and high motion accuracy. And it ensures the continuity of the output displacement of the test platform and will not affect the test results.

(3) The fixing device of the present invention has five fixed points and five measurement degrees of freedom, which not only meets the measurement requirements of the two degrees of freedom of the Hooke hinge, but also makes up for the shortcoming of the limited movement range of the straight beam type flexible hinge, Increased measurement range.

(4) The flexible spherical hinge of the present invention has three degrees of freedom, low friction resistance, zero clearance, and high precision, which ensures the continuity of output displacement and will not affect the test results.

(5) The straight beam type flexible hinge of the present invention is connected with the fixing device by a ball head screw and a spring, and the connection position is adjustable to meet the multi-degree-of-freedom measurement requirements.

Description of drawings

1 is a schematic diagram of a multi-degree-of-freedom motion branch chain resolution test platform and a test method of the present invention;

2 is a schematic diagram of the distribution of fixed points of the fixing device of the present invention;

Among them, 1 is the laser displacement meter, 2 is the moving platform, 3 is the straight beam type flexible hinge, 4 is the ball head screw, 5 is the spring, 6 is the flexible ball hinge, 7 is the linear drive assembly, 8 is the Hooke hinge, 9 for the fixed device.

Detailed ways

The embodiments of the present invention will be further described below with reference to the accompanying drawings.

1, the multi-degree-of-freedom motion branched chain resolution test platform of the present invention includes: a laser displacement meter 1; a fixing device 9; a straight beam type flexible hinge 3 connected with the fixing device 9; and a straight beam type flexible hinge 3 The fixed moving platform 2; and the linear drive assembly 7 arranged between the fixing device 9 and the moving platform 2, the upper end of the linear drive assembly 7 is connected with the lower end surface of the moving platform through the flexible ball hinge 6, and the lower end is connected to the fixed platform through the Hook hinge 8 The device 9 is connected; there are four straight beam type flexible hinges 3, which are symmetrically and evenly distributed with the moving platform 2 as the center; the laser displacement meter 1 is placed above the moving platform 2, and the test point is the center point of the moving platform; the fixed There are five fixing points on the device 9, which are symmetrically distributed, and four threaded holes are evenly distributed on each fixing; the straight beam type flexible hinge 3 and the moving platform 2 are integrally processed and formed; Spherical counterbore, the ball head screw 4 passes through the straight beam type flexible hinge, the ball head is placed in the counterbore to adjust the connection position, and the spring 5 is placed between the fixing device and the flexible hinge to connect the two; the moving platform 2. A flexible spherical hinge support is installed at the center of the lower end surface; the Hooke hinge 8 is respectively connected with the upper end surface of the fixing device 9 and the lower end surface of the moving platform through screws.

The flexible ball hinge 6 adopted in the present invention is of spherical incision type, which is simpler in structure than ordinary ball hinges, has three degrees of freedom, and can be deflected at any angle and direction to meet the installation of five different fixed points.

The working principle of the present invention:

The motion curve of the restraint test platform based on flexible hinges has unique continuous function characteristics, and the precise input and output functions of the restraint test platform based on flexible hinges can be obtained by combining finite element simulation and experimental calibration.

The test is performed in two steps:

1. Select the nanoscale calibrated linear displacement driver to ensure that only the radial runout of the inner bearing of the Hooke hinge is the variable in the entire testing process to measure its error.

2. On the basis of the above test structure, use the motion branch chain to be tested to replace the nanoscale calibrated linear displacement driver, and measure the motion resolution of its five degrees of freedom respectively.

The first step is to first give an input displacement curve to the nanoscale calibration linear displacement driver, the linear drive component 7 transmits the displacement curve to the moving platform 2, and the laser displacement meter 1 can obtain the displacement curve by measuring the displacement curves of the four symmetrical points on the moving platform. The output displacement curve of the linear drive assembly 7 is obtained. During the movement of the linear drive assembly 7, if there is no bearing radial runout, the output displacement curve will be smooth, continuous and unique, but due to the existence of the bearing radial runout error, the output displacement curve is no longer smooth and continuous, and, The displacement of the linear actuator is nm level, while the error caused by the radial runout of the inner bearing of Hook hinge 8 is μm level, so the radial runout error of the bearing can be easily distinguished through finite element simulation and experimental calibration. In the whole testing process, due to the characteristics of straight beam flexible hinge 3 and flexible spherical hinge 6 without gap and friction, the continuity of output displacement is ensured, so that there is only one variable in the measurement result, which is the diameter caused by the internal bearing of the Hook hinge. runout error.

Referring to FIG. 2, since the Hook hinge 8 has two degrees of freedom, and each Hook hinge 8 has two sets of bearings inside, it is necessary to measure the displacement error of more than two degrees of freedom, so the fixing device 9 is provided with five fixed There is a fixed point in the center of the fixture, and the other four fixed points are symmetrically and evenly distributed with the middle fixed point as the center, and the displacement measurement with five degrees of freedom not only meets the measurement requirements of the two degrees of freedom of the Hooke hinge, but also The problem of limited measurement range caused by the small rotation angle of the straight beam type flexible hinge 3 is solved, and the measurement range is increased. When the linear drive assembly 7 is placed in different fixed positions, the height difference in the vertical direction is reduced. At this time, it can be adjusted by rotating the ball screw 4 on the fixing device 9 to achieve the desired height difference.

The second step is to replace the nanoscale calibrated linear displacement driver with the motion branch of the multi-degree-of-freedom parallel motion platform to be tested, and measure the motion resolution of the motion branch to be tested according to the same testing methods and steps described above.

Claims (3)

1. A multi freedom motion branch resolution test platform which is characterized in that: the method comprises the following steps: a laser displacement meter (1); a fixing device (9); a straight beam type flexible hinge (3) connected to the fixing device (9); a movable platform (2) fixedly connected with the straight beam type flexible hinge (3); and a linear driving assembly (7) arranged between the fixing device (9) and the movable platform (2); the upper end of the linear driving component (7) is connected with the lower end face of the movable platform through a flexible spherical hinge (6), and the lower end of the linear driving component is connected with a fixing device (9) through a Hooke hinge (8); the number of the straight beam type flexible hinges (3) is four, and the straight beam type flexible hinges are symmetrically and uniformly distributed by taking the movable platform (2) as a center; the laser displacement meter (1) is placed above the movable platform (2), and the test point is the center point of the movable platform; the fixing device (9) is provided with five fixing points which are symmetrically distributed, and four threaded holes are uniformly distributed on each fixing point; the straight beam type flexible hinge (3) and the movable platform (2) are integrally processed and formed; the upper end face of the fixing device (9) is provided with a spherical counter bore, a ball head screw rod (4) penetrates through the straight beam type flexible hinge, a ball head is arranged in the counter bore to play a role in adjusting the connecting position, and a spring (5) is arranged between the fixing device and the flexible hinge to connect the fixing device and the flexible hinge; a flexible spherical hinge support is arranged at the center of the lower end face of the movable platform (2); and the hook joint (8) is respectively connected with the upper end surface of the fixing device (9) and the lower end surface of the movable platform through screws.

2. The multi-degree-of-freedom motion branched-chain resolution testing platform according to claim 1, characterized in that: the adopted flexible ball hinge (6) structure is in a spherical notch shape, has three degrees of freedom, and can deflect at any angle and direction to meet the installation of five different fixed points.

3. A multi-degree-of-freedom motion branched chain resolution test method utilizes the multi-degree-of-freedom motion branched chain resolution test platform of claim 1 or 2, and is characterized in that: the test method is carried out in two steps:

firstly, an input displacement curve is firstly given to a nanoscale calibration linear displacement driver, a linear driving assembly (7) transmits the displacement curve to a movable platform (2), a laser displacement meter (1) can obtain an output displacement curve of the linear driving assembly (7) by measuring the displacement curves of four symmetrical points on the movable platform, if the displacement curve output by the radial runout of a bearing is smooth, continuous and unique in the motion process of the linear driving assembly (7), the output displacement curve is not smooth and continuous due to the radial runout error of the bearing, moreover, the displacement of the linear driving assembly is in a nm level, and the error caused by the radial runout of the bearing in a Hooke hinge (8) is in a mum level, so the radial runout error of the bearing can be easily distinguished through finite element simulation and experimental calibration, and in the whole test process, because the characteristics of no clearance and no friction between a straight beam type flexible hinge (3) and a flexible spherical hinge (6), the continuity of output displacement is ensured, and the measuring result has only one variable, namely the radial runout error caused by the bearing in the Hooke joint; the Hooke's joint (8) has two degrees of freedom, each Hooke's joint (8) has two groups of bearings inside, so need measure the displacement error more than two degrees of freedom, so set up five fixed points on the fixing device (9), the fixing device center has a fixed point, other four fixed points regard middle fixed point as the symmetrical uniform distribution of center, have displacement measurement of five degrees of freedom, not only satisfied the measurement requirement of two degrees of freedom of Hooke's joint, still solved the problem that the measuring range is limited that the corner of the straight beam type flexible hinge (3) is minor and causes, has increased the measuring range, when the straight line driving assembly (7) is placed in different fixed positions, the vertical direction difference in height is reduced, can adjust through the ball screw (4) on the rotary fixture (9) at this moment, in order to reach the ideal difference in height;

and secondly, replacing the nanoscale calibration linear displacement driver with a motion branched chain of the multi-degree-of-freedom parallel motion platform to be measured, and measuring the motion resolution of five degrees of freedom of the motion branched chain respectively.

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