Dynamic error detection system for small absolute photoelectric encoder

Abstract

The invention discloses a small absolute photoelectric encoder dynamic error detection system, which comprises a motor, a reference encoder, a detected encoder, a system electric box and a computer, and is characterized in that the detected encoder, the reference encoder and the motor are coaxially connected in sequence, the system electric box is electrically connected with the detected encoder, the reference encoder and the motor, and the computer is electrically connected with the detected encoder, the reference encoder and the motor. And the computer is electrically connected with the system electric box. According to the dynamic error detection system for the small absolute photoelectric encoder, dynamic error detection is carried out on the small detected encoder based on the designed error detection system, in the detection process, the rotating speed is variable, error detection of different angles is achieved, the detection result is visual and accurate, and the detection precision is high. And the method has the characteristics of high real-time performance, high precision and high resolution. The precision of the system is 1.26 '', the rotation range is 0-90r / min, and dynamic error detection of a small absolute photoelectric encoder with less than 16 bits can be realized.

Description

Technical Field

[0001] The invention belongs to the technical field of error detection, and in particular relates to a dynamic error detection system for a small absolute photoelectric encoder. Background Art

[0002] During the development and production of photoelectric encoders, errors and accuracy must be tested. Photoelectric encoder testing involves both static and dynamic error detection. Currently, there is no reliable dynamic error detection equipment in China; most equipment can only estimate dynamic error by measuring static error. Therefore, the development of dynamic error detection equipment for photoelectric encoders is necessary. In the absence of dynamic testing methods, photoelectric encoder research relies solely on increasing rigidity and strength to ensure dynamic accuracy, making miniaturization difficult.

[0003] Currently, there are two main common methods for testing photoelectric encoders. One method uses an autocollimator and a polyhedron to form a detection system. This polyhedron prism detection method is a more complex process. During testing, the polyhedron is coaxially connected to the photoelectric encoder under test. After adjusting the polyhedron's eccentricity and pyramidal error, the autocollimator is used to measure the photoelectric encoder's error. Each time the polyhedron rotates through one face, the photoelectric encoder under test is tested for error. The polyhedron prism detection method has a detection accuracy better than 0.5", making it suitable for testing high-resolution and high-precision photoelectric encoders. However, its limited number of detection points does not allow for error detection at multiple angles.

[0004] The other method is to use a high-precision angle reference instrument to detect low-precision photoelectric encoders. That is, the high-precision photoelectric encoder comparison detection method uses a high-precision reference photoelectric encoder to perform error detection on the low-precision photoelectric encoder under test. The detection process of the high-precision photoelectric encoder detection method is relatively simple. It requires that the resolution and accuracy of the reference photoelectric encoder be more than 3 times greater than the accuracy and resolution of the photoelectric encoder under test to complete the error detection of the photoelectric encoder under test. Therefore, this method is more suitable for error detection of small photoelectric encoders with low accuracy and resolution. This detection method can realize error detection of all position points of the photoelectric encoder under test.

[0005] At the same time, according to the idea of traditional dynamic error evaluation, during dynamic detection, the dynamic error of the photoelectric encoder must first be detected at a specified speed, and then its dynamic error must be evaluated. The evaluation result only includes the error evaluation result at the current speed. To evaluate the dynamic error of the photoelectric encoder within a speed range, the traditional dynamic error evaluation method is to perform an error test every time the speed increases within the speed range, and then evaluate all the test data together. The main disadvantages of this method are as follows: Limited by traditional statistical thinking, the more error sampling points, the more accurate the evaluation result. To accurately evaluate the dynamic error at each speed within the speed range, it is necessary to detect the error as much as possible within the speed range, which is both time-consuming and labor-intensive. The traditional error evaluation method only provides an evaluation value and cannot reflect the changing trend of the dynamic error within the speed range. Summary of the Invention

[0006] The purpose of the present invention is to solve the problems raised in the background technology and to provide a dynamic error detection system for a small absolute photoelectric encoder.

[0007] To achieve the above object, the technical solution adopted by the present invention is:

[0008] The present invention proposes a small absolute photoelectric encoder dynamic error detection system, comprising:

[0009] Motor, reference encoder, encoder under test, system electrical box and computer, including:

[0010] The encoder under test, the reference encoder and the motor are coaxially connected in sequence, the system electric box is electrically connected to the encoder under test, the reference encoder and the motor respectively, and the computer is electrically connected to the system electric box;

[0011] When error detection is performed within a preset time period, the computer controls the motor to rotate at a preset speed through the system electrical box;

[0012] The system electrical box collects the output data of the encoder under test and the reference encoder respectively, and compares the output data of the corresponding encoder under test and the reference encoder. When the output data of the two are inconsistent, the output data of the current encoder under test and the reference encoder are latched;

[0013] Then, the output data of the encoder under test and the reference encoder corresponding to the latched state are subtracted to obtain the error data of the encoder under test;

[0014] Each error data is input into the FIFO queue of the system electrical box, and each error data passing through the FIFO queue is input into the computer to calculate the error accuracy of the encoder under test.

[0015] Preferably, the small absolute photoelectric encoder dynamic error detection system also includes a spindle, a tray, a bracket, a first coupling and a second coupling, the spindle is installed on the reference encoder, the base of the motor is installed on the bracket, and the output end of the motor is connected to one end of the spindle through the first coupling, the encoder to be measured is connected to the other end of the spindle through the second coupling, and the encoder to be measured is detachably mounted on the tray, and the tray is mounted on the reference encoder.

[0016] Preferably, before performing error detection, the computer clears the reference encoder data at the zero position of the encoder under test.

[0017] Preferably, the computer controls the rotation speed of the motor through a system electrical box to perform variable speed rotation at a preset frequency and a preset speed.

[0018] Preferably, the system electrical box includes an FPGA module, a USB transmission module and a memory, wherein the FPGA module is used to respectively collect the output data of the tested encoder and the reference encoder, and the output data of the tested encoder and the reference encoder are both output in parallel, and the corresponding output data of the tested encoder and the reference encoder are compared. When the output data of the two are inconsistent, the data output by the current tested encoder and the reference encoder are stored in the memory for latching;

[0019] The FPGA module then reads the data output by the corresponding encoder under test and the reference encoder from the memory and performs subtraction to obtain the error data of the encoder under test;

[0020] The FPGA module inputs each error data into the FIFO queue of the USB transmission module to wait for transmission, and each error data passing through the FIFO queue is input into the computer;

[0021] The computer calculates the root mean square or standard deviation of all received error data to obtain the final accuracy error of the encoder under test within a preset time period.

[0022] Preferably, the system electrical box further comprises an automatic identification module. When the output data of the encoder under test is serial output, the automatic identification module collects the serial data output by the encoder under test, converts the serial data into a form that can be read by the FPGA, and then inputs the serial data into the FPGA module.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] This small absolute photoelectric encoder dynamic error detection system performs dynamic error detection on small encoders under test based on a designed error detection system. During the detection process, the rotation speed varies, enabling error detection at different angles. The test results are intuitive and accurate, and feature high real-time performance, high precision, and high resolution. This system has an accuracy of 1.26" and a rotation range of 0 to 90 r / min, enabling dynamic error detection on small absolute photoelectric encoders with resolutions up to 16 bits. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 Schematic diagram of the structure of the dynamic error detection system of a small absolute photoelectric encoder of the present invention;

[0026] Figure 2 Schematic diagram of the output data of the encoder under test of the present invention;

[0027] Figure 3 This is a schematic diagram of the module of the electrical box of the system of the present invention;

[0028] Figure 4 The figure is a flow chart of error detection for the encoder under test according to the present invention. DETAILED DESCRIPTION

[0029] In order to make the purpose, technical solutions and advantages of this application more clear, the following further describes this application in detail with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain this application and are not intended to limit this application.

[0030] In one embodiment, Figure 2 As shown, a small absolute photoelectric encoder dynamic error detection system is provided, comprising: a motor 7, a reference encoder 6, a measured encoder 1, a system electrical box 10 and a computer 9, wherein:

[0031] The encoder under test 1, the reference encoder 6 and the motor 7 are coaxially connected in sequence (as Figure 1 As shown, the three are set in sequence from top to bottom);

[0032] In this embodiment, the small absolute photoelectric encoder dynamic error detection system further includes a spindle 4, a tray 2, a bracket 8, a first coupling 5, and a second coupling 3. The spindle 4 is mounted on the reference encoder 6, the base of the motor 7 is mounted on the bracket 8, and the output end of the motor 7 is connected to one end of the spindle 4 via the first coupling 5. The encoder 1 to be tested is connected to the other end of the spindle 4 via the second coupling 3. The encoder 1 to be tested is detachably mounted on the tray 2, and the tray 2 is mounted on the reference encoder 6.

[0033] The system electric box 10 is electrically connected to the encoder under test 1, the reference encoder 6 and the motor 7 respectively, and the computer 9 is electrically connected to the system electric box 10;

[0034] During use of this system, the encoder 1 under test is mounted on the tray 2, and the second coupling 3 is tightened to fix the encoder 1 under test to the main shaft 4, and then fix the encoder 1 under test to the reference encoder 6 and the motor 7. When the motor 7 is started, it drives the reference encoder 6 and the encoder 1 under test to rotate synchronously.

[0035] Before error detection, the computer 9 clears the data of the reference encoder 6 at the zero position of the encoder 1 under test;

[0036] When error detection is performed within a preset time period, the computer 9 controls the motor 7 to rotate at a preset speed through the system electrical box 10 (in this embodiment, the computer 9 controls the motor 7 to rotate at a preset speed at a preset frequency through the system electrical box 10, that is, the speed of the motor 7 within the preset time period is variable. The specific speed change frequency and the speed at which the motor 7 rotates can be set according to actual needs. In this embodiment, the rotation range is 0 to 90 r / min);

[0037] The system electrical box 10 collects the output data of the tested encoder 1 and the reference encoder 6 respectively, and compares the output data of the corresponding tested encoder 1 and the reference encoder 6. When the output data of the two are inconsistent, the output data of the current tested encoder 1 and the reference encoder 6 are latched;

[0038] Then, the data output by the encoder under test 1 and the reference encoder 6 corresponding to the latched state are subtracted to obtain the error data of the encoder under test 1;

[0039] Each error data is input into the FIFO queue of the system electrical box 10 , and each error data passing through the FIFO queue is input into the computer 9 to calculate the error accuracy of the encoder 1 under test.

[0040] It should be noted that, in this embodiment, the reference encoder 6 is a 23-bit high-resolution, high-real-time, high-precision photoelectric encoder. After error compensation of the reference photoelectric encoder, its accuracy is better than 0.7", and it can achieve code-by-code output of data below 5r / s. The accuracy of the small photoelectric encoder (i.e., the encoder 1 under test) is not better than 10", and the maximum number of data output bits is 16 bits; the accuracy of the reference encoder 6 is 0.7", and the number of bits is 23, which is much higher than the accuracy and resolution of the small photoelectric encoder (i.e., the encoder 1 under test), and is suitable for accuracy detection of the encoder 1 under test. The motor 7 is a high-torque position sensorless brushless DC motor 7 with a rated power of 60W and an output rated torque of 2N·m.

[0041] Each encoder converts the angle information into digital information and outputs it in binary code. An n-bit encoder 1 divides a circle into two n The resolution δ is:

[0042]

[0043] When collecting the output data of the encoder 1 under test (i.e., the angle information of the encoder 1 under test is converted into digital information and output as binary information), an angle error of β is caused compared with the actual angle, and the maximum β is:

[0044] β max =δ;

[0045] The lower the output bit of the encoder 1 under test, the greater the β max The larger the error is. For the 16-bit encoder 1 under test, the maximum error is 20". To eliminate the error, when β = 0, the binary information output by the encoder 1 under test is It is the true value of the measured angle information. At this time, the measured encoder 1 outputs binary information. becomes The critical point, such as Figure 2 shown.

[0046] exist Figure 2 In the example, when the encoder 1 is rotated, the binary information it outputs is changed from Increase to The output data of encoder 1 under test is Jump to The edge moment of is the exact moment when the angle information of the encoder 1 is measured.

[0047] The encoder under test 1 uses a high-precision A / D conversion chip to complete angle segmentation. There is a processing delay between the conversion of the angle signal to the digital signal. When the speed is too fast, the encoder under test 1 will not be able to respond in time, and its output data will jump, resulting in system delay and code jumping. At this time, it is impossible to collect errors at all resolution points of the encoder under test 1. Therefore, during dynamic error detection, 360 angles are taken in the circle, that is, an error point is latched every 1°. Assume that the current speed is ω 0 / s, the data output delay of encoder 1 under test is t d , then when rotating, the frequency of the output data of the encoder 1 under test changes for:

[0048]

[0049] In this embodiment, an error sampling point is selected every 1° within the circumference, so the error sampling point frequency f c for:

[0050] f c =ω;

[0051] When the system speed reaches the maximum value of 90r / min, f c =540Hz, and the output data delay of a general small photoelectric encoder (the encoder under test (1)) will not exceed 500us (based on experience), so according to the formula get 2kHz is at least three times greater than 540Hz. According to Shannon's sampling theorem, error sampling at every 1° point can be achieved.

[0052] In one embodiment, Figure 3 As shown, the system electrical box 10 includes an FPGA module, a USB transmission module and a memory, wherein the FPGA module is used to respectively collect the output data of the encoder under test 1 and the reference encoder 6, and the output data of the encoder under test 1 and the reference encoder 6 are both output in parallel, and the corresponding output data of the encoder under test 1 and the reference encoder 6 are compared. When the output data of the two are inconsistent, the output data of the current encoder under test 1 and the reference encoder 6 are stored in the memory for latching; wherein, for each encoder that outputs data in parallel, the FPGA module can directly read the output data of each encoder;

[0053] The FPGA module then reads the corresponding data output by the encoder under test 1 and the reference encoder 6 from the memory and performs subtraction to obtain the error data of the encoder under test 1;

[0054] The FPGA module inputs each error data into the FIFO queue of the USB transmission module for transmission, and each error data passing through the FIFO queue is input into the computer 9. The USB transmission module is designed using the USB chip CY7C68013A. The CY7C68013A chip integrates an enhanced 51 core, and its instruction set is compatible with the standard 8051. The chip provides a serial interface engine that can handle most USB 2.0 protocol processing, thereby greatly reducing the workload of USB protocol processing. It also provides a 4KB FIFO queue to ensure the reliability of high-speed data transmission. In this embodiment, the CY7C68013A chip adopts the Slave FIFO mode. Based on the transmission in this working mode, the CPU will not be involved, which greatly improves data transmission efficiency.

[0055] The computer 9 calculates the root mean square or standard deviation of all received error data to obtain the final accuracy error of the encoder 1 under test within a preset time period.

[0056] In one embodiment, the system electrical box 10 further includes an automatic identification module. When the output data of the encoder 1 under test is serial output, the automatic identification module collects the serial data output by the encoder 1 under test, converts the serial data into a form readable by the FPGA, and then inputs the serial data into the FPGA module. The automatic identification module uses a MAX3160E chip, which can automatically identify the 232 / 485 bus and realize the collection and switching of serial data. The MAX3160E chip can serve as both a 232 bus controller and a 485 bus controller.

[0057] This small absolute photoelectric encoder dynamic error detection system performs dynamic error detection on small encoders under test based on a designed error detection system. During the detection process, the rotation speed varies, enabling error detection at different angles. The test results are intuitive and accurate, and feature high real-time performance, high precision, and high resolution. This system has an accuracy of 1.26" and a rotation range of 0 to 90 r / min, enabling dynamic error detection on small absolute photoelectric encoders with resolutions up to 16 bits.

[0058] The above-described embodiments merely represent several implementation methods of the present application. While the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that a person skilled in the art could make various modifications and improvements without departing from the spirit of the present application, all of which fall within the scope of protection of the present application. Therefore, the scope of protection of the present patent application shall be determined by the appended claims.

Claims

1. A small absolute photoelectric encoder dynamic error detection system, characterized by: The small absolute photoelectric encoder dynamic error detection system comprises: a motor (7), a reference encoder (6), a measured encoder (1), a system electric box (10) and a computer (9), wherein: The encoder under test (1), the reference encoder (6) and the motor (7) are coaxially connected in sequence, the system electric box (10) is electrically connected to the encoder under test (1), the reference encoder (6) and the motor (7) respectively, and the computer (9) is electrically connected to the system electric box (10); When error detection is performed within a preset time period, the computer (9) controls the motor (7) to rotate at a preset speed through the system electrical box (10); The system electric box (10) collects the output data of the encoder under test (1) and the reference encoder (6) respectively, and compares the output data of the corresponding encoder under test (1) and the reference encoder (6). When the output data of the two are inconsistent, the output data of the current encoder under test (1) and the reference encoder (6) are latched. Then, the data outputted by the encoder under test (1) and the reference encoder (6) corresponding to the latched state are subtracted to obtain error data of the encoder under test (1); Each error data is input into a FIFO queue of a system electric box (10), and each error data passing through the FIFO queue is input into a computer (9) to calculate the error accuracy of the encoder (1) under test.

2. The small absolute photoelectric encoder dynamic error detection system according to claim 1, characterized in that: The small absolute photoelectric encoder dynamic error detection system further comprises a main shaft (4), a tray (2), a bracket (8), a first coupling (5) and a second coupling (3), wherein the main shaft (4) is mounted on a reference encoder (6), the base of the motor (7) is mounted on the bracket (8), and the output end of the motor (7) is connected to one end of the main shaft (4) through the first coupling (5), the encoder to be measured (1) is connected to the other end of the main shaft (4) through the second coupling (3), and the encoder to be measured (1) is detachably mounted on the tray (2), and the tray (2) is mounted on the reference encoder (6).

3. The dynamic error detection system of a small absolute photoelectric encoder according to claim 1, wherein: Before error detection, the computer (9) clears the data of the reference encoder (6) at the zero position of the encoder under test (1).

4. The dynamic error detection system of a small absolute photoelectric encoder according to claim 1, wherein: The computer (9) controls the rotation speed of the motor (7) through the system electric box (10) to perform variable speed rotation at a preset frequency and a preset speed.

5. The small absolute photoelectric encoder dynamic error detection system according to claim 1, wherein: The system electrical box (10) includes an FPGA module, a USB transmission module and a memory, wherein the FPGA module is used to respectively collect output data of the tested encoder (1) and the reference encoder (6), and the output data of the tested encoder (1) and the reference encoder (6) are both output in parallel, and the output data of the corresponding tested encoder (1) and the reference encoder (6) are compared. When the output data of the two are inconsistent, the data output by the current tested encoder (1) and the reference encoder (6) are stored in the memory for latching; The FPGA module then reads the data output by the corresponding encoder under test (1) and the reference encoder (6) from the memory and performs subtraction to obtain error data of the encoder under test (1); The FPGA module inputs each error data into the FIFO queue of the USB transmission module to wait for transmission, and each error data passing through the FIFO queue is input into the computer (9); The computer (9) calculates the root mean square or standard deviation of all received error data to obtain the final accuracy error of the encoder (1) under test within a preset time period.

6. The dynamic error detection system of a small absolute photoelectric encoder according to claim 1, wherein: The system electrical box (10) further comprises an automatic identification module. When the output data of the encoder under test (1) is a serial output, the automatic identification module collects the serial data output by the encoder under test (1), converts the serial data into a form that can be read by the FPGA, and then inputs the serial data into the FPGA module.

Images