A three-coordinate measurement probe based on negative feedback regulation and a measurement method

Abstract

A kind of three-coordinate measurement probe based on negative feedback regulation and measurement method, belong to precision measurement technical field.The present application solves the problems of poor precision and complex calibration process of three-coordinate measuring machine for measuring rigid object profile in prior art.The present application includes probe assembly, optical measurement system and elastic control module, the probe assembly includes first fixed plate and probe fixed on the bottom end of first fixed plate, the optical measurement system includes mirror frame fixed on the top surface of first fixed plate, reflecting mirror horizontally installed on the top of mirror frame, first refracting mirror and second refracting mirror vertically installed below mirror frame and distributed perpendicular to each other, laser interferometer arranged above reflecting mirror, first laser and first photosensitive position sensor distributed on both sides of first refracting mirror, and second laser and second photosensitive position sensor distributed on both sides of second refracting mirror, the elastic control module includes second fixed plate and a plurality of elastic columns.The present application is used for object profile measurement.

Description

TECHNICAL FIELD

[0001] The present application relates to a three-coordinate measurement probe based on negative feedback regulation and a measurement method, and belongs to the technical field of precision measurement. BACKGROUND

[0002] The elastic deformation caused by the probe contact force will introduce systematic measurement error when the current three-coordinate measuring instrument contact probe measures the profile of a rigid object. The existing technology usually relies on the rigidity of the probe material to suppress deformation or compensates for errors through a complex mechanical model. The former has insufficient accuracy under high measurement force conditions, and the latter has a complex calibration process and limited adaptability. Therefore, there is an urgent need for a probe structure that can actively and real-time compensate for probe deformation to improve profile measurement accuracy. SUMMARY

[0003] The present application is to solve the problem of poor accuracy and complex calibration process of the three-coordinate measuring instrument for measuring the profile of a rigid object in the prior art, and further provides a three-coordinate measurement probe based on negative feedback regulation and a measurement method.

[0004] The technical solution adopted by the present application to solve the above technical problems is:

[0005] A three-coordinate measurement probe based on negative feedback regulation, comprising a probe assembly, an optical measurement system and an elastic regulation module, wherein the probe assembly comprises a first fixed plate and a probe fixed to the bottom end of the first fixed plate, the optical measurement system comprises a mirror holder fixed to the top surface of the first fixed plate, a reflecting mirror horizontally mounted on the top of the mirror holder, a first refracting mirror and a second refracting mirror vertically mounted below the mirror holder and distributed perpendicular to each other, a laser interferometer arranged above the reflecting mirror, a first laser and a first photosensitive position sensor distributed on both sides of the first refracting mirror, and a second laser and a second photosensitive position sensor distributed on both sides of the second refracting mirror, the elastic regulation module comprises a second fixed plate and a plurality of elastic columns arranged between the second fixed plate and the first fixed plate and parallel to each other, the second fixed plate is located on one side of the mirror holder, and the first laser, the second laser, the first photosensitive position sensor, the second photosensitive position sensor, the laser interferometer and the second fixed plate are fixed to the three-coordinate measuring instrument.

[0006] Further, an adjusting screw is arranged below the second fixed plate to realize the regulation of the elastic pre-tightening force of the elastic column.

[0007] Further, the lower part of the elastic column is processed with an internal thread, the adjusting screw is a screw, and the screw is threadedly connected with the elastic column through the first fixed plate.

[0008] Further, the number of elastic columns is four and they are circumferentially distributed below the second fixed plate.

[0009] Further, the second fixed plate is arranged higher than the first and second refractive mirrors, and the elastic control module is located between the frame and the second photosensitive position sensor.

[0010] Further, the first fixed plate comprises integrally formed first and second mounting sections, the second fixed plate is mounted above the first mounting section, and the frame and the probe are mounted on the upper and lower sides of the second mounting section.

[0011] Further, the mirror is coaxially arranged with the probe.

[0012] Further, the probe is fixedly connected to the lower end face of the first fixed plate by means of a plurality of screws.

[0013] Further, the frame is a rigid rectangular frame.

[0014] A measurement method for measuring the contour of a rigid object by using the above-mentioned three-coordinate measurement probe, comprising the following steps:

[0015] Step one, mounting the probe on the three-coordinate measuring instrument;

[0016] Step two, calibration and debugging:

[0017] Adjust the elastic pre-tightening force of the elastic column to ensure that the probe is completely vertically placed, and record the initial positions X0, Y0 and Z0 of the probe at this time;

[0018] Step three, start measuring:

[0019] The three-coordinate measuring instrument drives the probe to move, and after touching the contour of the object, compares the position information X, Y and Z detected by the first and second photosensitive position sensors and the laser interferometer with the initial positions X0, Y0 and Z0 calibrated in step two, and calculates the offset of the probe at this time;

[0020] Step four, negative feedback adjustment:

[0021] According to the offset obtained in step three,

[0022] If it is determined that the probe has deviated, the probe is controlled to retreat, the elastic column is rebounded to the initial length, the motion path of the probe is re-planned according to the offset obtained in step three, and step five is executed.

[0023] If it is determined that the probe has not deviated, the contour point obtained at this time is the theoretical true value, and the data is recorded.

[0024] Step five, measure again:

[0025] According to the re-planned motion path of the probe in step four, the three-coordinate measuring instrument controls the probe to move again, and step three is repeated until the probe no longer deviates after contacting the object contour, and the data is recorded.

[0026] Compared with the prior art, the present application has the following effects:

[0027] Through the three-coordinate measuring probe of the present application, in the measurement process, the optical measurement system and the elastic regulation module can actively and real-time compensate the probe deformation, thereby effectively avoiding the problem of poor measurement accuracy caused by rigidly suppressing deformation in the prior art, thereby effectively improving the contour measurement accuracy, and at the same time, the present application adopts a negative feedback regulation mechanism, the measurement process is simpler and more adaptable. BRIEF DESCRIPTION OF DRAWINGS

[0028] Fig. 1 Fig. 1 is a first perspective view of the three-coordinate measuring probe based on negative feedback regulation of the present application (the structure of the three-coordinate measuring instrument is not shown);

[0029] Fig. 2 Fig. 2 is a second perspective view of the three-coordinate measuring probe based on negative feedback regulation of the present application (the structure of the three-coordinate measuring instrument is not shown);

[0030] Fig. 3 Fig. 3 is a front view of the three-coordinate measuring probe based on negative feedback regulation of the present application (the structure of the three-coordinate measuring instrument is not shown);

[0031] Fig. 4 Fig. 4 is a top view of the three-coordinate measuring probe based on negative feedback regulation of the present application (the structure of the three-coordinate measuring instrument is not shown);

[0032] Fig. 5 Fig. 5 is a schematic diagram of the laser beam refraction principle of the first laser, the first refracting mirror and the first photosensitive position sensor (i.e., the X / Y axis deviation detection principle diagram);

[0033] Fig. 6 Fig. 6 is a principle block diagram of the measurement method.

[0034] In the drawings:

[0035] 1, first fixed plate; 2, probe; 3, mirror holder; 4, reflecting mirror; 5, first refracting mirror; 6, second refracting mirror; 7, laser interferometer; 8, first laser; 9, first photosensitive position sensor; 10, second laser; 11, second photosensitive position sensor; 12, second fixed plate; 13, elastic column; 14, adjusting knob. DETAILED DESCRIPTION

[0036] Specific implementation one: combined with Figs. 1-6This description of embodiments provides a clear and complete description of the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0037] It should be noted that the descriptions of "front," "rear," "left," "right," "inner," "outer," "left side," "right side," "upper part," "lower part," "top," and "bottom" in this invention are defined based on the orientation or positional relationships shown in the accompanying drawings. They are merely for the convenience of describing the invention and for simplifying the description, and do not indicate or imply that the described structure must be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified.

[0038] A coordinate measuring machine (CMM) probe based on negative feedback adjustment includes a probe assembly, an optical measurement system, and an elastic adjustment module. The probe assembly includes a first fixed plate 1 and a probe 2 fixed to the bottom of the first fixed plate 1. The optical measurement system includes a mirror frame 3 fixed to the top surface of the first fixed plate 1, a reflector 4 horizontally mounted on the top of the mirror frame 3, a first refractor 5 and a second refractor 6 vertically mounted below the mirror frame 3 and perpendicularly distributed to each other, a laser interferometer 7 arranged above the reflector 4, a first laser 8 and a first photosensitive position sensor 9 distributed on both sides of the first refractor 5, and a second laser 10 and a second photosensitive position sensor 11 distributed on both sides of the second refractor 6. The elastic adjustment module includes a second fixed plate 12 and a plurality of elastic columns 13 arranged parallel to each other between the second fixed plate 12 and the first fixed plate 1. The second fixed plate 12 is located on one side of the mirror frame 3, and the first laser 8, the second laser 10, the first photosensitive position sensor 9, the second photosensitive position sensor 11, the laser interferometer 7, and the second fixed plate 12 are all fixed on the CMM.

[0039] The coordinate measuring machine is existing technology, and its specific structure will not be described in detail here. The control center on the coordinate measuring machine receives displacement signals from each photosensitive position sensor and the laser interferometer 7, and controls the movement of the probe 2.

[0040] The probe 2 is rigidly connected to the first fixing plate 1.

[0041] The first refracting mirror 5, the second refracting mirror 6, and the reflecting mirror 4 are integrated onto the first fixed plate 1 via the mirror frame 3 to form an optical coupling mechanism.

[0042] The second fixing plate 12 is a base fixing plate, and the probe assembly is installed below the second fixing plate 12 through several elastic pillars 13.

[0043] Working principle:

[0044] The object to be measured is fixed and has a certain rigidity. After the coordinate measuring machine drives the probe 2 to contact the surface of the object, the contact reaction force causes the elastic column 13 to undergo slight deformation, which causes the first fixed plate 1 to shift in position. At the same time, the optical coupling mechanism formed by the reflector 4 and the two refractors changes in position, which in turn causes the light spot of the corresponding photosensitive position sensor to shift. The laser interferometer 7 and the reflector 4 are used to realize Z-axis distance measurement. The negative feedback adjustment is performed based on the light spot offset vector, that is, the deformation of the elastic column 13 is calculated to obtain the offset of the probe 2. The coordinate measuring machine controls the probe 2 to retract. At this time, the elastic column 13 rebounds to its original length. The motion path is replanned again according to the previous offset, that is, the compensation amount. The probe 2 is moved again, and the above actions are repeated until the probe 2 contacts the contour but the elastic column 13 is kept in a zero deformation state. At this time, the contour point is recorded as the theoretical true value.

[0045] Measurement Principle: The first laser 8 emits an X-axis laser, and the second laser 10 emits a Y-axis laser. The X-axis laser and the Y-axis laser pass through the first refractor 5 and the second refractor 6 on the probe assembly, respectively, and hit the corresponding first photosensitive position sensor 9 and second photosensitive position sensor 11. The position of the refractors shifts, which causes the position of the laser hitting the corresponding photosensitive position sensor to change. The X and Y axis offsets can be calculated based on the specific value of the position change. The Z-axis offset is obtained by comparing the distance measured by the laser rangefinder on the Z axis with the starting distance. The movement trajectory of the coordinate measuring machine is then calculated based on the offset. This process is repeated until the probe contacts the contour but keeps the elastic column 13 in a zero-deformation state. At this point, the contour point is recorded as the theoretical true value.

[0046] With the coordinate measuring probe of the present invention, during the measurement process, the optical measurement system and elastic control module can actively and in real time compensate for the deformation of probe 2, thereby effectively avoiding the problem of poor measurement accuracy caused by rigid suppression of deformation in existing methods, and thus effectively improving the contour measurement accuracy. At the same time, the present invention adopts a negative feedback adjustment mechanism, making the measurement process simpler and more adaptable.

[0047] An adjustment knob 14 is arranged below the second fixing plate 12, and the elastic preload of the elastic column 13 can be controlled by adjusting the knob 14.

[0048] The elastic column 13 and the adjusting knob 14 can have various structures, as long as they can achieve the adjustment of the elastic preload of the elastic column by adjusting the knob. For example:

[0049] In the first scenario, the lower part of the elastic column 13 is machined with internal threads, and the adjusting knob 14 is a screw that passes through the first fixing plate 1 and is threadedly connected to the elastic column 13. The elastic column 13 can be made of a high-hardness rubber material, sufficient to provide a certain buffering effect on the first fixing plate 1 and the probe 2. The elastic preload of the elastic column can be adjusted by rotating the screw (i.e., the adjusting knob) clockwise or counterclockwise.

[0050] In the second scenario: the elastic column 13 includes a column body and a spring fitted onto the column body. The spring is located between the first fixed plate 1 and the second fixed plate 12. The lower part of the column body passes through a corresponding aperture on the first fixed plate 1. A nut is located below the first fixed plate 1, and the nut is threadedly connected to the bottom of the column body. This design allows for adjustment of the spring compression via the nut, thereby controlling the elastic preload of the elastic column 13. After the probe 2 contacts the surface of the object being measured, the contact reaction force causes a slight deformation in the elastic column 13, which in turn causes a positional shift in the first fixed plate 1. At this time, the first fixed plate 1 can slide along the column body, further compressing the spring. The spring also prevents the first fixed plate 1 from excessively shifting. The nut is the adjusting knob 14.

[0051] There are four elastic columns 13, which are evenly distributed circumferentially below the second fixed plate 12.

[0052] The second fixing plate 12 is positioned higher than the first refracting mirror 5 and the second refracting mirror 6, and the elastic adjustment module is located between the frame 3 and the second photosensitive position sensor 11. This design, since the second photosensitive position sensor 11 is fixedly mounted on the coordinate measuring machine, effectively avoids interference between the second photosensitive position sensor 11 and the probe assembly, the elastic adjustment module, or the frame 3 by placing the elastic adjustment module between them. Furthermore, by positioning the second fixing plate 12 higher than the first refracting mirror 5 and the second refracting mirror 6, the laser beam emitted by the second laser 10 can smoothly reach the second photosensitive position sensor 11 to form a light spot, thereby ensuring accurate offset measurement.

[0053] The first fixing plate 1 includes an integrally formed first mounting section and a second mounting section. The second fixing plate 12 is installed above the first mounting section, and the lens frame 3 and the probe 2 are respectively installed on the upper and lower sides of the second mounting section.

[0054] The reflector 4 and the probe 2 are arranged coaxially.

[0055] The probe 2 is fixed to the lower end face of the first fixing plate 1 by a number of screws.

[0056] The frame 3 is a rigid rectangular frame.

[0057] A measurement method for measuring the contour of a rigid object using the aforementioned coordinate measuring probe includes the following steps:

[0058] Step 1: Install the probe on the coordinate measuring machine;

[0059] Step 2, Calibration and Debugging:

[0060] Adjust the elastic preload of the elastic column 13 to ensure that the probe 2 is placed completely vertically, and record the initial positions X0, Y0, and Z0 of the probe 2 at this time. The method to ensure that the probe 2 is completely vertical is as follows: the laser beam emitted by the first laser 8 in the X-axis direction hits the center position of the first photosensitive position sensor 9, and the laser beam emitted by the second laser 10 in the Y-axis direction hits the center position of the second photosensitive position sensor 11. At this time, the probe 2 is completely vertical. When the probe 2 is not placed completely vertically, an alarm program is triggered, allowing technicians to make corresponding adjustments. Z0 is the height position of the probe 2 fed back by the laser interferometer 7.

[0061] Step 3, begin measurement:

[0062] The coordinate measuring machine moves the probe 2 and touches the outline of the object. The position information X, Y and Z detected by the first photosensitive position sensor 9, the second photosensitive position sensor 11 and the laser interferometer 7 are compared with the initial position X0, Y0 and Z0 calibrated in step two, and the offset of the probe 2 at this time is calculated.

[0063] Step 4, Negative Feedback Adjustment:

[0064] Based on the offset obtained in step three,

[0065] If it is determined that probe 2 has deviated, then control probe 2 to retract, so that elastic column 13 rebounds to its initial length. The motion path of probe 2 is replanned according to the offset obtained in step three, and step five is executed.

[0066] If it is determined that probe 2 has not shifted, then the contour point measured at this time is the theoretical true value, and the data is recorded;

[0067] Step 5, measure again:

[0068] Based on the replanned motion path of probe 2 in step four (for example, if the X-axis movement is too large, the corresponding value of the X-axis will be reduced in the second movement), the coordinate measuring machine controls probe 2 to move again, repeating step three until probe 2 no longer deviates after contacting the object contour, and the data is recorded.

[0069] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A coordinate measuring probe based on negative feedback adjustment, characterized in that: The system includes a probe assembly, an optical measurement system, and a flexible adjustment module. The probe assembly includes a first fixed plate (1) and a probe (2) fixed to the bottom of the first fixed plate (1). The optical measurement system includes a lens frame (3) fixed to the top surface of the first fixed plate (1), a mirror (4) horizontally mounted on the top of the lens frame (3), a first refracting mirror (5) and a second refracting mirror (6) vertically mounted below the lens frame (3) and perpendicularly distributed to each other, a laser interferometer (7) arranged above the mirror (4), a first laser (8) distributed on both sides of the first refracting mirror (5), and a first photosensitive position sensor. The elastic control module includes a second fixed plate (12) and several elastic columns (13) arranged parallel to each other between the second fixed plate (12) and the first fixed plate (1). The second fixed plate (12) is located on one side of the frame (3), and the first laser (8), the second laser (10), the first photosensitive position sensor (9), the second photosensitive position sensor (11), the laser interferometer (7) and the second fixed plate (12) are all fixed on the coordinate measuring machine.

2. The coordinate measuring probe based on negative feedback adjustment according to claim 1, characterized in that: An adjustment knob (14) is arranged below the second fixed plate (12), and the elastic preload of the elastic column (13) can be controlled by adjusting the knob (14).

3. A coordinate measuring probe based on negative feedback adjustment according to claim 2, characterized in that: The lower part of the elastic column (13) is machined with internal threads, the adjusting knob (14) is a screw, and the screw passes through the first fixing plate (1) and is threadedly connected to the elastic column (13).

4. A coordinate measuring probe based on negative feedback adjustment according to claim 1, characterized in that: The number of elastic columns (13) is four and they are evenly distributed circumferentially below the second fixed plate (12).

5. A coordinate measuring probe based on negative feedback adjustment according to claim 1, characterized in that: The second fixing plate (12) is arranged above the first refracting mirror (5) and the second refracting mirror (6), and the elastic adjustment module is located between the frame (3) and the second photosensitive position sensor (11).

6. A coordinate measuring probe based on negative feedback adjustment according to claim 1, characterized in that: The first fixing plate (1) includes an integrally formed first mounting section and a second mounting section. The second fixing plate (12) is installed above the first mounting section, and the frame (3) and the probe (2) are installed on the upper and lower sides of the second mounting section respectively.

7. A coordinate measuring probe based on negative feedback adjustment according to claim 1, characterized in that: The reflector (4) and the probe (2) are arranged coaxially.

8. A coordinate measuring probe based on negative feedback adjustment according to claim 1, characterized in that: The probe (2) is fixed to the lower end face of the first fixing plate (1) by a number of screws.

9. A coordinate measuring probe based on negative feedback adjustment according to claim 1, characterized in that: The frame (3) is a rigid rectangular frame.

10. A measurement method for measuring the contour of a rigid object using the coordinate measuring probe described in any one of claims 1 to 9, characterized in that: Includes the following steps: Step 1: Install the probe on the coordinate measuring machine; Step 2, Calibration and Debugging: Adjust the elastic preload of the elastic column (13) to ensure that the probe (2) is placed completely vertically, and record the initial positions X0, Y0 and Z0 of the probe (2) at this time; Step 3, begin measurement: The coordinate measuring machine drives the probe (2) to move. After touching the outline of the object, the position information X, Y and Z detected by the first photosensitive position sensor (9), the second photosensitive position sensor (11) and the laser interferometer (7) are compared with the initial position X0, Y0 and Z0 calibrated in step two, and the offset of the probe (2) at this time is calculated. Step 4, Negative Feedback Adjustment: Based on the offset obtained in step three, If it is determined that the probe (2) has deviated, then control the probe (2) to retract, so that the elastic column (13) rebounds to the initial length, replan the motion path of the probe (2) according to the offset obtained in step three, and execute step five; If it is determined that the probe (2) has not shifted, then the contour point measured at this time is the theoretical true value, and the data is recorded; Step 5, measure again: According to the replanned motion path of probe (2) in step four, the coordinate measuring machine controls probe (2) to move again, repeating step three until probe (2) no longer deviates after contacting the object contour, and records the data.

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