Five-axis machine tool end position dynamic accuracy measuring device and method

Abstract

The application provides a kind of five-axis machine tool end pose dynamic precision measuring device and method, the measuring device includes measuring head and standard ball, the measuring head is installed on machine tool spindle by tool holder, and the standard ball is installed on machine tool processing area;The measuring head is integrated with attitude measurement sensor and three displacement sensors, and the three displacement sensors are used to contact with the standard ball.The measuring head integrated with displacement sensor and attitude measurement sensor increases the tool shaft attitude measurement function on the basis of R-test, so that it can not only measure the tool tip point position, but also reflect the tool shaft attitude information such as pitch angle, roll angle, heading angle and the like, thereby increasing the accuracy of the measurement result, and the attitude measurement range of C-axis 0 to 360°, A-axis-60° to 60° can be realized.

Description

Technical Field

[0001] This invention relates to the field of machine tool motion accuracy measurement devices, specifically to a device and method for measuring the dynamic accuracy of the end-effector posture of a five-axis machine tool. Background Technology

[0002] CNC machine tools are the foundation of modern machinery manufacturing, and their precision directly affects the quality of the processed products. Five-axis CNC machine tools, by adding two new rotary axes to a traditional three-axis CNC machine tool, enable it to machine complex spatial surfaces. Depending on their topology, five-axis CNC machine tools can be categorized into various types, such as double-swivel-head, double-rotary-table, and swivel-head-rotary-table. Due to their excellent characteristics in machining complex spatial surfaces, they are widely used in the processing of high-removal-rate, high-precision workpieces such as aircraft parts, impellers, and propellers, and have a significant impact on aerospace, precision instruments, and other fields.

[0003] The introduction of two rotary axes makes it more difficult to test the motion accuracy of five-axis CNC machine tools. Determining whether a five-axis CNC machine tool meets accuracy requirements is a major research focus in the field of machine tool inspection. Furthermore, the limitations of traditional accuracy testing instruments such as laser interferometers, double ballbars, and laser trackers in the accuracy testing of multi-axis linkage machine tools are becoming increasingly apparent.

[0004] Since most high-end five-axis CNC machine tools are equipped with RTCP (Tool Tip Follower), utilizing the RTCP function to perform multi-axis linkage motion while the tool tip remains stationary can accurately determine the tool motion error during five-axis linkage and understand the machining accuracy of the machine tool. Based on the RTCP function, a new type of five-axis CNC machine tool motion accuracy tester, the R-test, has been developed. This tester can reflect the positional error of the tool tip during actual multi-axis linkage machining. However, the R-test can only be used to detect the displacement error of the tool tip in three axes on a five-axis CNC machine tool, and cannot simultaneously reflect the tool axis posture of the five-axis CNC machine tool, which will increase the inaccuracy of the measurement results to some extent. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the purpose of this invention is to provide a device and method for measuring the dynamic accuracy of the end-effector posture of a five-axis machine tool.

[0006] The five-axis machine tool end-effector dynamic accuracy measuring device provided by the present invention includes a measuring head and a standard ball. The measuring head is mounted on the machine tool spindle via a tool holder, and the standard ball is mounted on the machine tool machining area.

[0007] The measuring head integrates an attitude measurement sensor and three displacement sensors, which are used to measure the distance to a standard ball.

[0008] Preferably, it also includes a housing, a support, and an end cap, wherein the attitude measurement sensor is mounted on the end cap, and the end cap is mounted on the bottom of the housing;

[0009] The support is installed at the bottom of the end cap, and three displacement sensors are installed at the bottom of the support. The top of the housing is connected to the handle.

[0010] Preferably, in the three displacement sensors, the direction line of the third displacement sensor passes through the intersection of the direction lines of the first two displacement sensors.

[0011] Preferably, the attitude measurement sensor is coaxially arranged with the tool holder, and its axis passes through the intersection of the direction lines of the three displacement sensors.

[0012] Preferably, the number of standard balls is one or more;

[0013] The attitude measurement sensor includes a tilt sensor and a gyroscope.

[0014] The five-axis machine tool end-effector dynamic accuracy measurement method according to the present invention, using the aforementioned five-axis machine tool end-effector dynamic accuracy measurement device, includes the following steps:

[0015] Step 1: Mount the measuring head onto the machine tool spindle via the tool holder, and install the standard ball in the machine tool machining area;

[0016] Step 2: Adjust the position of the machine tool spindle, define the intersection of the three displacement sensors in the measuring head as the tool tip point, make the three displacement sensors contact the standard ball, and make the intersection of the three displacement sensors coincide with the center of the standard ball;

[0017] Step 3: Perform static measurement of the end effector position of the machine tool.

[0018] Keeping the theoretical coordinates of the blade tip unchanged, the C-axis rotates to multiple preset angles in sequence, the A-axis rotates to multiple preset angles in sequence, and after each pose is held for a preset time, the end-effector pose dynamic accuracy measuring device is controlled to collect data.

[0019] Alternatively, perform dynamic measurement of the machine tool end effector's position and orientation:

[0020] The machine tool runs along a conical trajectory, and the end-effector dynamic accuracy measurement device collects data at a preset sampling frequency;

[0021] Step 4: Calculate the tool tip position information and tool axis posture information based on the collected data.

[0022] Preferably, in the static measurement of the machine tool end position posture, the rotation angle range of the C-axis is 0° to 360°, and the rotation angle range of the A-axis is -60° to 60°.

[0023] Preferably, in step 3, the data acquisition includes:

[0024] The relative displacement of the center of a standard sphere is collected using three displacement sensors;

[0025] The pitch angle α and roll angle β of the cutter shaft are acquired by a tilt sensor, and the axial rotational angular velocity of the cutter shaft is acquired by a gyroscope.

[0026] Preferably, in step 4, the calculation of the blade tip position information includes the following steps:

[0027] The coordinates of the standard sphere's center in the measuring head coordinate system are calculated based on the relative displacement of the standard sphere's center using the sphere center solution algorithm, thereby obtaining the coordinates of the tool tip in the machine tool coordinate system.

[0028] The calculation of the tool axis posture information includes the following steps:

[0029] Based on the pitch angle α, roll angle β, and axial rotational angular velocity of the cutter shaft Calculate the size of the tool axis heading angle γ.

[0030] Compared with the prior art, the present invention has the following beneficial effects:

[0031] 1. This invention adopts the technical means of integrating an attitude measurement sensor on the measuring head. Based on R-test, it adds the tool axis attitude measurement function, so that it can not only measure the position of the tool tip, but also reflect the tool axis attitude information such as pitch angle, roll angle, and yaw angle, thereby increasing the accuracy of the measurement results.

[0032] 2. This invention uses the technical means of installing displacement sensors, tilt sensors and gyroscopes on the machine tool spindle and installing standard balls on the machine tool machining area, which solves the technical problem in the prior art that the detection device needs to be fixedly connected to the tool holder and the worktable at the same time, resulting in a complex structure, cumbersome operation and low reliability of the measuring device.

[0033] 3. This invention uses an angle sensor and a gyroscope as the tool axis attitude detection device, which solves the technical problem in the prior art that the attitude measurement range is limited by the displacement sensor's measurement range when the tool axis direction is measured by the displacement sensor. It can achieve an attitude measurement range of 0 to 360° for the C-axis and -60° to 60° for the A-axis. Attached Figure Description

[0034] Other features, objects, and advantages of the present invention will become more apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings:

[0035] Figure 1 This is an exploded structural diagram of the pose dynamic accuracy measurement device in this invention;

[0036] Figure 2 This is a schematic diagram of the overall structure of the pose dynamic accuracy measurement device in this invention;

[0037] Figure 3 This is a schematic diagram showing the installation of the posture dynamic accuracy measurement device and the machine tool in this invention.

[0038] The diagram shows:

[0039] Tool holder 1, displacement sensor 6

[0040] Shell 2, Standard Sphere 7

[0041] Tilt sensor 3, machine tool spindle 8

[0042] Gyroscope 4 Machine tool processing area 9

[0043] Support 5 Detailed Implementation

[0044] The present invention will now be described in detail with reference to specific embodiments. These embodiments will help those skilled in the art to further understand the present invention, but do not limit the invention in any way. It should be noted that those skilled in the art can make several changes and improvements without departing from the concept of the present invention. These all fall within the protection scope of the present invention.

[0045] This invention discloses a dynamic accuracy measurement device and method for the end effector posture of a five-axis machine tool. Based on the R-test, an attitude measurement sensor is added, which can not only measure the position of the tool tip, but also reflect the tool axis attitude information such as pitch angle, roll angle, and yaw angle, thereby increasing the accuracy of the measurement results.

[0046] The five-axis machine tool end-effector dynamic accuracy measurement device provided by the present invention, such as Figure 3 As shown, it includes a measuring head and a standard ball 7. The measuring head is mounted on the machine tool spindle 8 via a tool holder 1, and the standard ball 7 is mounted on the machine tool machining area 9. Preferably, the number of standard balls 7 can be one or more.

[0047] Specifically, such as Figure 1 , Figure 2As shown, the measuring head integrates an angle sensor 3, a gyroscope 4, and three displacement sensors 6. The angle sensor 3 and the gyroscope 4 form an attitude measurement sensor, and the three displacement sensors 6 are used to measure the distance to the standard ball 7. The measuring head also includes a housing 2, a support 5, and an end cap. The angle sensor 3 is mounted on the top of the end cap, the gyroscope 4 is mounted on the bottom of the end cap, and the end cap is mounted on the bottom of the housing 2. The support 5 is mounted on the bottom of the end cap, and the three displacement sensors 6 are mounted on the bottom of the support 5. The top of the housing 2 is connected to the handle 1.

[0048] In the three displacement sensors 6, the direction line of the third displacement sensor 6 passes through the intersection of the direction lines of the first two displacement sensors 6. The tilt sensor 3 and the gyroscope 4 are both coaxially mounted with the tool holder 1, and their axes pass through the intersection of the direction lines of the three displacement sensors 6. The displacement sensors 6 can be contact or non-contact sensors. In a preferred embodiment, all three displacement sensors 6 are contact sensors, and the distance between the contact surfaces of the three displacement sensors 6 and the intersection point is the same.

[0049] Example 1

[0050] This embodiment provides a method for measuring the dynamic accuracy of the end effector pose of a five-axis machine tool. The method utilizes the aforementioned five-axis machine tool end effector pose dynamic accuracy measuring device to measure the tool tip position and tool axis posture of the machine tool.

[0051] The tool tip position measurement is performed by three displacement sensors 6 and a standard ball 7. The measuring head is mounted on the machine tool spindle 8, and the intersection of the three displacement sensors 6 is defined as the tool tip. The displacement sensors 6 are in contact with the standard ball 7, and the relative displacement change of the center of the standard ball 7 is measured. The coordinates of the center of the standard ball 7 in the measuring head coordinate system are calculated by the ball center solving algorithm, thereby obtaining the coordinates of the tool tip in the machine tool coordinate system.

[0052] The tool axis attitude measurement is performed by a tilt sensor 4 and a gyroscope 5. The tilt sensor 4 can measure the pitch and roll angles of the tool axis, and the gyroscope 5 can measure the axial rotational angular velocity of the tool axis. Based on the measurement data of the tilt sensor 4 and the gyroscope 5, the heading angle of the tool axis can be calculated, thereby obtaining the complete attitude information of the tool axis.

[0053] The measurement method specifically includes the following steps:

[0054] Step 1: Install the measuring head on the machine tool spindle 8 via the tool holder 1, and install the standard ball 7 on the machine tool machining area 9;

[0055] Step 2: Adjust the position of the machine tool spindle 8, define the intersection of the three displacement sensors 6 in the measuring head as the tool tip point, make the three displacement sensors 6 contact the standard ball 7, and make the intersection of the three displacement sensors 6 (the origin of the measuring head) coincide with the center of the standard ball 7. In this step, the deviation must be less than 1μm. During the multi-axis linkage process, the theoretical position of the tool tip point is unchanged, and the displacement sensor reading does not change. However, due to the geometric errors of each motion axis of the machine tool, the actual position of the tool tip point changes. Therefore, in step 3, it is necessary to measure the magnitude of the displacement deviation through the position sensor 6.

[0056] Step 3: Perform static measurement of the end effector position of the machine tool.

[0057] The machine tool motion program is designed using the tool tip tracking function (RTCP) of a five-axis machine tool. The theoretical coordinates of the tool tip remain unchanged. The C-axis rotates sequentially to multiple preset angles, and the A-axis rotates sequentially to multiple preset angles. After a preset time at each pose, the end-effector dynamic accuracy measurement device is controlled to collect data. In a preferred embodiment, the C-axis rotates sequentially to 0°, 60°, 120°, 180°, 240°, and 300°, and the A-axis rotates sequentially to -60°, -30°, 0°, 30°, and 60°. Data is collected after a 3-second pause at each pose.

[0058] Alternatively, perform dynamic measurement of the machine tool end effector's position and orientation:

[0059] The machine tool motion program is designed using the tool tip tracking function (RTCP) of a five-axis machine tool to make the machine tool run a conical trajectory. The end-effector dynamic accuracy measurement device collects data at a preset sampling frequency. In a preferred embodiment, the conical trajectory is the AK3 trajectory in ISO10791-6:2014. The dynamic performance of the machine tool is analyzed through the pose measurement data.

[0060] During the multi-axis linkage process of the machine tool in step 3, the posture of the tool axis is constantly changing. The relative displacement of the center of the standard ball 7 is collected by three displacement sensors 6; the pitch angle α and roll angle β of the tool axis are collected by the tilt sensor 3; and the axial rotational angular velocity of the tool axis is collected by the gyroscope 4. This allows for precise measurement of the actual orientation of the tool axis and the actual position of the tool tip in each pose.

[0061] In step 3 of this embodiment, data is collected using both static and dynamic measurement methods. From this data, errors in different aspects of the machine tool can be analyzed.

[0062] Step 4: Calculate the tool tip position information and tool axis posture information based on the collected data, specifically including the following steps:

[0063] Steps for calculating the tool tip position information: Using the sphere center solving algorithm, calculate the coordinates of the center of the standard sphere 7 in the measuring head coordinate system based on the relative displacement of the center of the standard sphere 7, thereby obtaining the coordinates of the tool tip in the machine tool coordinate system.

[0064] Steps for calculating tool axis attitude information:

[0065] Based on the axial rotational angular velocity of the cutter shaft Calculate the current angle increment Δθ i ;

[0066] Calculate the current heading angle increment Δγ using the following formula. i :

[0067]

[0068] Where Δβ i The roll angle increment is Δβ. i =β i -β i-1 ,β i β is the current tool axis roll angle. i-1 α is the tool axis roll angle at the previous moment. i This is the current tool axis pitch angle;

[0069] Based on the current heading angle increment Δγ i Calculate the current heading angle γ.

[0070] Those skilled in the art will understand that, besides implementing the system and its various devices, modules, and units provided by this invention in the form of purely computer-readable program code, the same functions can be achieved entirely through logical programming of the method steps, making the system and its various devices, modules, and units of this invention function in the form of logic gates, switches, application-specific integrated circuits, programmable logic controllers, and embedded microcontrollers. Therefore, the system and its various devices, modules, and units provided by this invention can be considered as a hardware component, and the devices, modules, and units included therein for implementing various functions can also be considered as structures within the hardware component; alternatively, the devices, modules, and units for implementing various functions can be considered as both software modules implementing the method and structures within the hardware component.

[0071] In the description of this application, it should be understood that the terms "upper", "lower", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this application.

[0072] Specific embodiments of the present invention have been described above. It should be understood that the present invention is not limited to the specific embodiments described above, and those skilled in the art can make various changes or modifications within the scope of the claims, which do not affect the essence of the present invention. Unless otherwise specified, the embodiments and features described in this application can be arbitrarily combined with each other.

Claims

1. A device for measuring dynamic accuracy of end position of a five-axis machine tool, characterized in that, The measuring head is installed on the machine tool spindle (8) through the tool holder (1), and the standard ball (7) is installed on the machine tool machining area (9); The measuring head is integrated with a posture measurement sensor and three displacement sensors (6) for measuring the distance from the standard ball (7); The number of standard balls (7) is one or more; The posture measurement sensor includes an inclination sensor (3) and a gyroscope (4); The inclination sensor (3) is used to collect the pitch angle and roll angle of the tool shaft, and the gyroscope (4) is used to collect the axial rotation angular velocity of the tool shaft, and the size of the tool shaft heading angle is calculated according to the pitch angle, roll angle and axial rotation angular velocity. According to the axial rotation angular velocity of the tool shaft Calculating the current angular increment ; The current heading angle angular increment is calculated according to the following formula : wherein is a roll angle delta, and , is a current tool shaft roll angle, is a previous tool shaft roll angle, is a current tool shaft pitch angle; According to the current heading angle angular increment The magnitude of the current heading angle is calculated.

2. The dynamic accuracy measuring device for the end position of a five-axis machine tool according to claim 1, characterized in that It also includes a shell (2), a support (5) and an end cover, the posture measurement sensor is installed on the end cover, and the end cover is installed at the bottom of the shell (2); The support (5) is installed at the bottom of the end cover, and the bottom of the support (5) is provided with three displacement sensors (6), and the top of the shell (2) is connected with the tool holder (1).

3. The end position dynamic accuracy measuring device for five-axis machine tools according to claim 1, characterized in that Among the three displacement sensors (6), the direction line of the third displacement sensor (6) passes through the intersection of the direction lines of the first two displacement sensors (6).

4. The end position dynamic accuracy measuring device for five-axis machine tools according to claim 3, characterized in that The posture measurement sensor and the tool holder (1) are coaxially arranged, and the axis passes through the intersection of the direction lines of the three displacement sensors (6).

5. A method for measuring dynamic accuracy of end position of a five-axis machine tool, characterized in that, The five-axis machine tool end position dynamic precision measuring device of any one of claims 1-4 comprises the following steps: Step 1: install the measuring head on the machine tool spindle (8) through the tool holder (1), and install the standard ball (7) on the machine tool machining area (9); Step 2: adjust the position of the machine tool spindle (8), define the intersection of the three displacement sensors (6) in the measuring head as the tool tip point, make the three displacement sensors (6) contact with the standard ball (7), and make the intersection of the three displacement sensors (6) coincide with the center of the standard ball (7); Step 3: perform machine tool end position static measurement: Keep the theoretical coordinates of the tool tip point unchanged, rotate the C-axis to a plurality of preset angles in turn, rotate the A-axis to a plurality of preset angles in turn, and after staying at each position for a preset time, control the end position dynamic precision measuring device to collect data; Or, perform machine tool end position dynamic measurement: Make the machine tool run a preset trajectory, and the end position dynamic precision measuring device collects data at a preset sampling frequency; Step 4: calculate the tool tip point position information and tool shaft attitude information according to the data collected by the displacement sensor and the attitude sensor.

6. The dynamic accuracy measurement method of the end position of the five-axis machine tool according to claim 5, characterized in that, In the machine tool end position static measurement, the rotation angle range of the C-axis is 0° to 360°, and the rotation angle range of the A-axis is -60° to 60°.

7. The dynamic accuracy measurement method of the end position of the five-axis machine tool according to claim 5, characterized in that, In step 3, the data collection includes: Collecting the relative displacement of the center of the standard ball (7) through the three displacement sensors (6).

8. The dynamic accuracy measurement method of the end position of the five-axis machine tool according to claim 7, characterized in that, In step 4, the tool tip point position information calculation includes the following steps: Through the center of the ball solving algorithm, the coordinates of the center of the standard ball (7) in the measuring head coordinate system are calculated according to the relative displacement of the center of the standard ball (7), so as to obtain the coordinates of the tool tip point in the machine tool coordinate system.

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