System and method for measuring tooth space of wrist gear of industrial robot

Abstract

The invention discloses a system and method for measuring the tooth space of a wrist gear of an industrial robot, and relates to the field of industrial robots. The objective of the invention is to quantify the final assembly effect of the wrist gear and provide data evaluation for the final result of the wrist assembly of the industrial robot. The system comprises an upper computer, a driver, a mounting rack and a servo motor, the driver and the servo motor are fixed on the mounting rack, the upper computer controls the driver to work, the driver controls the servo motor to work, the servo motor is connected with a tested wrist and can drive the tested wrist to rotate, and the tested wrist is connected with the mounting rack. A tested wrist is fixed on the mounting rack, and the mounting rack is provided with a fixer used for connecting an output flange of the tested wrist. According to the measuring method, the fluctuation degree of the backlash of the gear in the measured wrist at different meshing positions can be represented, and whether the gear in the measured wrist is assembled too tightly or not can be determined.

Description

Technical Field

[0001] The invention relates to the technical field of industrial robots, and in particular to a system and method for measuring tooth gap of wrist gears of industrial robots. Background Art

[0002] With the development of engineering technology, robots are increasingly being used in industrial production. The current application level of industrial robots has become one of the important indicators of a country or region's industrialization level. With the widespread application of industrial robots, people's performance requirements for industrial robots are getting higher and higher. Clients will pay more and more attention to the robot's point accuracy, trajectory accuracy, and the shaking of the robot's end. Since the internal bevel gears of the robotic arm wrist are used for transmission and reversing, the quality of the bevel gear assembly will have a great impact on the overall use. If the tooth gap between the two bevel gears is too small, that is, the two bevel gears are installed too tightly, then the resistance of the wrist will be relatively large during operation, which can easily cause excessive wear of the bevel gears, low transmission efficiency, and shaking of the end during start and stop. If the tooth gap between the two bevel gears is too large, that is, the two bevel gears are installed too loosely, then the overall accuracy will decrease and the joint reversing performance will deteriorate. In addition, if the tooth gap is too large, the end load is prone to shaking under the action of external force, and the customer's senses are poor, which is easy to cause customer complaints.

[0003] Currently, the assembly of the bevel gear inside the wrist mainly relies on manual labor. The rationality of the bevel gear tooth gap after assembly also depends entirely on the worker's feel and experience. The final effect of the assembly also needs to be verified after the whole machine is assembled. Once there is a problem, the machine needs to be disassembled and reassembled. The overall efficiency is low and cannot be quantified. Summary of the invention

[0004] The technical problem to be solved by the present invention is to provide a system and method for measuring the tooth gap of an industrial robot wrist gear, which can quantify the final assembly effect of the wrist gear and provide data evaluation for the final result of the industrial robot wrist assembly.

[0005] One of the technical solutions provided by the present invention is a system for measuring the tooth gap of an industrial robot wrist gear, comprising a host computer, a driver, a mounting frame and a servo motor, wherein the driver and the servo motor are fixed on the mounting frame, the host computer controls the driver to work, the driver controls the servo motor to work, the servo motor is connected to the wrist to be measured and can drive the wrist to be measured to rotate, the wrist to be measured is fixed on the mounting frame, and a fixture for connecting the output flange of the wrist to be measured is provided on the mounting frame.

[0006] The invention discloses a system for measuring tooth gap of wrist gear of an industrial robot, wherein the driver is fixedly mounted on a mounting frame, and the driver is connected to a host computer through a debugging line.

[0007] The invention discloses a system for measuring tooth gap of wrist gear of an industrial robot, wherein the servo motor is fixedly mounted on a mounting frame, and the servo motor is connected to a driver through a connecting line.

[0008] The invention discloses a system for measuring tooth gap of a wrist gear of an industrial robot, wherein a motor shaft of a servo motor is connected with a coupling, and the coupling can be connected with an input side of a wrist to be measured.

[0009] The invention discloses a system for measuring tooth gap of wrist gear of an industrial robot, wherein the mounting frame comprises a base plate, a motor mounting frame is movably arranged on the base plate, and a wrist mounting frame is fixedly arranged on the base plate.

[0010] The invention discloses a system for measuring tooth gap of wrist gear of an industrial robot, wherein the motor mounting frame is installed in a waist-shaped hole on a base plate and can slide on the base plate.

[0011] The invention discloses a system for measuring tooth gap of wrist gear of an industrial robot, wherein the fixer is arranged on the outside of a wrist mounting frame, and a through hole for connecting the wrist to be measured is arranged on the fixer.

[0012] Another technical solution provided by the present invention is a method for measuring the backlash of an industrial robot wrist gear, comprising the following steps:

[0013] In the preparation stage, the wrist to be measured is installed on the mounting frame and the fixture, the host computer is connected to the driver and communication is established, the driver is connected to the servo motor, and the servo motor is connected to the input side of the wrist to be measured;

[0014] Change the operation mode of the driver to torque mode, control the driver to output a specified forward current, such as but not limited to a specified value in the range of 0.5-2A, and maintain it (it should be noted that the current here cannot be too large or too small. If the current is too small, the motor output is too small and cannot overcome the friction resistance of the joint. If the current is too large, the motor output is too large, and excessive torque is prone to impact and gear deformation). Collect and record the encoder position P1 of the servo motor at this time; after recording, control the driver to output a negative current equal to the forward current and maintain it, collect and record the encoder position P2 of the servo motor at this time. It is known that the resolution of the servo motor encoder is R, and the current wrist backlash calculation formula is:

[0015]

[0016] After the test is completed, loosen the fixture and the output flange of the wrist under test, control the servo motor to rotate a certain angle to make the gear end under test rotate a specified angle, such as but not limited to 30° / 45°, and then fix the fixture and the output flange of the wrist under test again. Repeat the above test to obtain multiple sets of data, and the average value of the internal tooth gap of the wrist under test can be obtained:

[0017]

[0018] Where, E is the average value of the internal tooth gap of the wrist being measured, S i is the result of measuring the tooth gap of the measured wrist at the specified position, n is the number of measurements, and the standard deviation of the tooth gap of the measured wrist can be obtained at the same time:

[0019]

[0020] Where θ is the standard deviation of the backlash of the wrist under test, which represents the fluctuation degree of the backlash of the internal gear of the wrist under test at different meshing positions.

[0021] The present invention provides a method for measuring the tooth gap of an industrial robot wrist gear, wherein after repeating the above-mentioned test to obtain multiple groups of data, the fixed connection between the fixer and the wrist to be measured is loosened, the working mode of the driver is changed by using a host computer to put it in a position mode, a program is written to make the driver control a servo motor to continuously rotate forward and reverse, and the wrist to be measured is warmed up for a specified time, such as but not limited to 30 minutes, and then the driver is used to measure the forward and reverse motor current of the servo motor when it is in a uniform speed section at different speeds, and the motor current is compared with the current of a standard wrist at this speed to confirm whether the gears inside the wrist to be measured are assembled too tightly.

[0022] The difference between the system and method for measuring the tooth gap of the wrist gear of an industrial robot disclosed by the present invention and the prior art is that the system for measuring the tooth gap of the wrist gear of an industrial robot disclosed by the present invention has a simple overall structure, low cost and high reliability; the position of the servo motor and the fixer can be adjusted through the waist-shaped hole, and it has a good adaptation effect on wrists of different sizes and types, and has good adaptability; the method for measuring the tooth gap of the wrist gear of an industrial robot disclosed by the present invention can quantify the data of the tooth gap of the measured wrist, effectively eliminating the inaccuracy of the sensory perception of the installer, and the result is more objective; this test method can not only test when the wrist gear is installed too loose, but also provide quantitative data when the gear is installed too tight, and the measurement is more comprehensive.

[0023] The following is a further description of a system and method for measuring tooth gap of an industrial robot wrist gear according to the present invention in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1It is a structural schematic diagram of a system for measuring backlash of wrist gear of an industrial robot according to the present invention;

[0025] Figure 2 It is a structural schematic diagram of a mounting frame in a system for measuring backlash of wrist gears of an industrial robot according to the present invention;

[0026] The markings in the figure are as follows: 1-host computer; 2-driver; 3-mounting frame; 31-base plate; 32-motor mounting frame; 33-wrist mounting frame; 4-servo motor; 5-coupling; 6-measured wrist; 7-fixture. DETAILED DESCRIPTION

[0027] The following examples are used to illustrate the present invention but are not intended to limit the scope of the present invention.

[0028] Example

[0029] like Figure 1 As shown, a system for measuring backlash of an industrial robot wrist gear of the present invention comprises a host computer 1, a driver 2, a mounting frame 3 and a servo motor 4. The driver 2 and the servo motor 4 are fixed on the mounting frame 3, the host computer 1 is electrically connected to the driver 2, and the driver 2 is electrically connected to the servo motor 4.

[0030] like Figure 2 As shown, the mounting frame 3 includes a base plate 31, on which a motor mounting frame 32 is movably mounted, and a wrist mounting frame 33 is fixedly mounted. The base plate 31 is provided with multiple groups of waist-shaped holes, and the motor mounting frame 32 is fixed to the waist-shaped holes of the base plate 31 by bolts. The position of the motor mounting frame 32 can slide left and right on the base plate 31 to adapt to different sizes of wrists 6 to be measured, so as to facilitate the connection of the motor with different sizes of wrists 6 to be measured. The wrist mounting frame 33 is fixedly connected to the end of the base plate 31 by bolts or adhesives, and the wrist mounting frame 33 is used to fix the wrist 6 to be measured. A fixer 7 is installed on the outside of the wrist mounting frame 33. The fixer 7 is provided with a through hole for connecting the wrist 6 to be measured, and the through hole at the top of the fixer 7 is connected to the output flange of the wrist 6 to be measured by bolts, so as to fix the output end of the wrist 6 to be measured.

[0031] The driver 2 is mounted on the base plate 31 of the mounting frame 3 by bolts or adhesives, and can move with the mounting frame 3. The driver 2 is connected to the host computer 1 through a debugging line. The host computer 1 can control the operation mode of the servo motor 4 by changing the working state of the driver 2, thereby realizing the measurement of the wrist tooth gap.

[0032] The servo motor 4 is mounted on the motor mounting frame 32 of the mounting frame 3 by means of bolts or the like, and is connected to the driver 2 by a connecting line. The driver 2 can control the motion state of the servo motor 4 by changing the output state of its current, thereby realizing the measurement of the tooth gap.

[0033] The wrist 6 to be tested is mounted on the wrist mounting frame 33 of the mounting frame 3, the output flange of the wrist 6 to be tested is connected to the fixture 7, and the input side of the wrist 6 to be tested is connected to the motor shaft of the servo motor 4 through the coupling 5. The rotation of the motor shaft of the servo motor 4 can be transmitted to the wrist 6 to be tested through the coupling 5, thereby realizing the application of torque to the internal transmission gear of the wrist 6 to be tested and the transmission of power.

[0034] When installing a measuring system for the backlash of an industrial robot wrist gear of the present invention, the driver 2 is first mounted on a base plate 31 and fixed, and a motor mounting frame 32 is mounted on the waist-shaped hole of the base plate 31 by means of bolts or the like. The waist-shaped hole has a certain adjustment space, and the mounting position of the motor mounting frame 32 can be adjusted to achieve the test of wrists 6 of different sizes; the servo motor 4 is mounted on the motor mounting frame 32, and the driver 2 and the servo motor 4 are communicated and controlled by a connecting line; the wrist mounting frame 33 is fixedly connected to the front end of the base by means of bolts, adhesives, etc., and a threaded hole is opened on the upper side of the wrist 6 to be measured. The wrist 6 is mounted on the wrist mounting frame 33 by bolt fixing; one end of the coupling 5 is fixed to the motor shaft of the servo motor 4, and the other end is connected to the input shaft of the wrist 6 to be measured, and the power of the servo motor 4 can be transmitted to the wrist 6 to be measured through the coupling 5; the fixer 7 is mounted on the outer side of the wrist mounting frame 33, and a waist-shaped hole is opened on the side of the fixer 7. The fixer 7 can adjust its final position through the waist-shaped hole to adapt to the wrist 6 to be measured of different sizes; the upper end of the fixer 7 is opened with a through hole, and the opening position corresponds to the output flange hole of the wrist 6 to be measured, and the output end of the wrist 6 to be measured can be fixed by the fixer 7.

[0035] A system for measuring backlash of an industrial robot wrist gear of the present invention can achieve measurement, data collection and analysis of backlash of the wrist gear in the following manner.

[0036] When starting the test, first connect the host computer 1 and the driver 2 and establish communication, change the operation mode of the driver 2 to the torque mode, control the driver 2 to output a specified positive current and keep it, collect and record the encoder position P1 of the servo motor 4 at this time; after recording, control the driver 2 to output a specified negative current and keep it, collect and record the encoder position P2 of the servo motor 4 at this time. It is known that the resolution of the servo motor 4 encoder is R, so we can get the current wrist backlash calculation formula as:

[0037]

[0038] After the test is completed, the fixation between the fixture 7 and the output flange of the wrist 6 to be tested is released, and the servo motor 4 is controlled to rotate a smaller angle and then the fixture 7 and the output flange of the wrist 6 to be tested are fixed again. The above test is repeated to obtain multiple sets of data. Finally, the data are sorted to obtain the expected value and standard deviation of the tooth gap of the wrist 6 to be tested, so as to evaluate the tooth gap of the wrist 6 to be tested and the overall fluctuation degree. The relevant calculation formula is as follows:

[0039]

[0040] Where, E is the average value of the internal backlash of the wrist 6 under test, S i is the result of measuring the backlash of the wrist 6 at the specified position; n is the number of measurements, is the standard deviation of the backlash of the wrist 6 under test, which characterizes the fluctuation degree of the backlash of the gears inside the wrist 6 under test at different meshing positions. After the measurement is completed, loosen the connection between the fixture 7 and the wrist 6 under test, and use the host computer 1 to change the working mode of the driver 2 to put it in the position mode. Write a program to make the driver 2 control the servo motor 4 to continuously rotate forward and reverse, thereby realizing the heat-up of the wrist 6 under test. After the specified heat-up time, use the driver 2 to measure the forward and reverse motor current of the servo motor 4 at different speeds in the uniform speed section, and compare it with the current of the standard wrist at this speed to confirm whether the gears inside the wrist 6 under test are assembled too tight.

[0041] The actual test cases of this method are as follows: Assemble the host computer 1, driver 2, mounting frame 3 and servo motor 4 and establish communication. Install the wrist assembly to be tested on the mounting frame 3 and establish a mechanical connection with the servo motor 4. The encoder bit number of the servo motor 4 is 17 bits, that is, the resolution R is 131072. After the test of the tested tooth is completed, the servo motor is controlled to rotate a certain angle to make the tested gear end rotate 30°. Such a complete gear test requires 12 tooth clearance tests, collect the corresponding data and use the formula to calculate the tooth clearance of the tested tooth. The relevant data and calculation results are shown in the following table.

[0042] Serial number Forward output encoder code number Reverse output encoder code number Encoder Bits Backlash (rad) 1 -23874711 -23875062 131072 0.016826 2 -23863824 -23864194 131072 0.017737 3 -23852490 -23852908 131072 0.020038 4 -23842205 -23841775 131072 0.020613 5 -23830759 -23831195 131072 0.0209 6 -23820405 -23820021 131072 0.018408 7 -23809034 -23809399 131072 0.017497 8 -23798745 -23798412 131072 0.015963 9 -23787310 -23787647 131072 0.016155 10 -23776643 -23776301 131072 0.016394 11 -23765336 -23765672 131072 0.016107 12 -23754875 -23754534 131072 0.016346

[0043] By sorting out the above backlash data and combining it with the calculation formula, it can be calculated that the overall backlash of the wrist is 0.017748637rad, and the overall fluctuation degree of the gear rotation is 0.001754792. Loosen the connection between the fixture and the wrist under test, change the working mode of the driver to make it in position mode, control the motor to continuously rotate forward and reverse to warm up the wrist under test, collect the forward and reverse current of the motor after 30 minutes of warm-up, and calculate the friction force of the gear of the wrist under test through the current, compare and verify the above results with the standard data, and then judge whether the assembly of the component is qualified.

[0044] Through the above method, the staff can quantify the gear backlash inside the newly assembled wrist, and then confirm whether the internal gear assembly of the wrist 6 under test is qualified.

[0045] A system and method for measuring backlash of an industrial robot wrist gear of the present invention has the following characteristics:

[0046] 1. The overall structure is simple, the cost is low and the reliability is high;

[0047] 2. The waist-shaped hole can be used to adjust the position of the servo motor and the holder, and it has a good adaptation effect on wrists of different sizes and types, and has good adaptability;

[0048] 3. The tooth gap of the measured wrist can be quantified, effectively eliminating the inaccuracy of the installation workers' senses, and the results are more objective;

[0049] 4. This test method can not only test when the wrist gear is installed too loosely, but also provide quantitative data when the gear is installed too tight, making the measurement more comprehensive.

[0050] Although the present invention has been described in detail above by general description and specific embodiments, it is obvious to those skilled in the art that some modifications or improvements can be made to the present invention. Therefore, these modifications or improvements made without departing from the spirit of the present invention all belong to the scope of protection claimed by the present invention.

Claims

1. A system for measuring backlash of wrist gears of industrial robots, characterized by: It includes a host computer, a driver, a mounting frame and a servo motor. The driver and the servo motor are fixed on the mounting frame. The host computer controls the driver to work, and the driver controls the servo motor to work. The servo motor is connected to the wrist to be measured and can drive the wrist to be measured to rotate. The wrist to be measured is fixed on the mounting frame, and a fixture for connecting the output flange of the wrist to be measured is provided on the mounting frame.

2. A system for measuring backlash of wrist gears of industrial robots according to claim 1, characterized in that: The driver is fixedly mounted on a mounting frame, and the driver is connected to a host computer via a debugging line.

3. A system for measuring backlash of wrist gears of industrial robots according to claim 1, characterized in that: The servo motor is fixedly mounted on the mounting frame, and the servo motor is connected to the driver via a connecting line.

4. A system for measuring backlash of wrist gears of industrial robots according to claim 1 or 3, characterized in that: The motor shaft of the servo motor is connected with a coupling, and the coupling can be connected to the input side of the wrist to be measured.

5. The system for measuring backlash of wrist gears of industrial robots according to claim 1, characterized in that: The mounting frame comprises a base plate, on which a motor mounting frame is movably arranged and a wrist mounting frame is fixedly arranged.

6. A system for measuring backlash of wrist gears of industrial robots according to claim 5, characterized in that: The motor mounting frame is installed in the waist-shaped hole on the base plate and can slide on the base plate.

7. The system for measuring backlash of wrist gears of industrial robots according to claim 5, characterized in that: The fixer is arranged on the outside of the wrist mounting frame, and a through hole for connecting the wrist to be measured is arranged on the fixer.

8. A method for measuring the backlash of an industrial robot wrist gear, characterized in that: The following steps are involved: In the preparation stage, the wrist to be measured is installed on the mounting frame and the fixture, the host computer is connected to the driver and communication is established, the driver is connected to the servo motor, and the servo motor is connected to the input side of the wrist to be measured; Change the operation mode of the driver to torque mode, control the driver to output a specified positive current and keep it, collect and record the encoder position P1 of the servo motor at this time; after recording, control the driver to output a specified negative current and keep it, collect and record the encoder position P2 of the servo motor at this time. It is known that the resolution of the servo motor encoder is R, then the current wrist backlash calculation formula is: After the test is completed, loosen the fixation between the fixture and the output flange of the wrist under test, control the servo motor to rotate a small angle, and then fix the fixture and the output flange of the wrist under test again. Repeat the above test to obtain multiple sets of data, and the average value of the internal tooth gap of the wrist under test can be obtained: Where, E is the average value of the internal tooth gap of the wrist being measured, S i is the result of measuring the tooth gap of the measured wrist at the specified position, n is the number of measurements, and the standard deviation of the tooth gap of the measured wrist can be obtained at the same time: In the formula, is the standard deviation of the backlash of the tested wrist, which represents the fluctuation degree of the backlash of the internal gear of the tested wrist at different meshing positions.

9. A method for measuring backlash of an industrial robot wrist gear according to claim 8, characterized in that: After repeating the above test to obtain multiple sets of data, loosen the connection between the fixture and the wrist under test, use the host computer to change the working mode of the driver to put it in position mode, write a program to make the driver control the servo motor to continuously rotate forward and reverse, and warm up the wrist under test. After the warm-up time is specified, use the driver to measure the forward and reverse motor current of the servo motor when it is in a uniform speed section at different speeds, and compare it with the current of the standard wrist at this speed to confirm whether the gears inside the wrist under test are assembled too tight.

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