A measurement system for quickly acquiring the rotation speed using a grating installed on the motor shaft

Abstract

The present invention discloses a measuring system for rapidly acquiring the rotation speed by using a grating piece installed on a motor shaft, 101) counting the number of tooth grooves of the grating piece, 102) obtaining the compensation coefficient of each tooth groove, 103) predicting the rotation speed; the present invention proposes a measuring system for rapidly acquiring the rotation speed by using a grating piece installed on a motor shaft, which can predict more quickly and accurately.

Description

Technical Field

[0001] The invention relates to a measuring system for rapidly acquiring rotation speed by utilizing a grating sheet installed on a motor shaft. Background Art

[0002] At present, most incremental encoders use the principle of grating plus photoelectric tube. No matter they are finished products or discrete ones, there are problems with the processing and installation accuracy of the grating. For some controls that require fast response speed, such as fast dynamometer, if the speed is not calculated by revolution but by the actual speed of each pulse time, there will be certain fluctuations. If the speed is calculated by revolution, there will be certain lag, which is not conducive to fast PID control and the accuracy of motor characteristic curve data. Summary of the invention

[0003] In view of the above technical defects, the present invention proposes a measurement system for quickly obtaining the rotation speed by using a grating piece installed on the motor shaft for faster and more accurate prediction.

[0004] In order to solve the above technical problems, the technical solution of the present invention is as follows:

[0005] A measurement system for quickly acquiring the rotation speed by using a grating sheet installed on a motor shaft specifically comprises the following steps:

[0006] 101) Count the number of teeth on the grating, and select any tooth to expand to the largest gap, and mark it as No. 1. Use the MCU to measure the time it takes for each tooth to pass through the phototube, and mark all the teeth in sequence. The rotation speed is obtained based on the time it takes for each tooth to pass through the phototube.

[0007] 102) Obtaining the compensation coefficient of each tooth slot, obtaining the current stable rotation speed according to the time for the grating piece to rotate one circle, and then obtaining the error compensation coefficient of each tooth slot in combination with the rotation speed of each tooth slot;

[0008] 103) Predict the speed. When the photoelectric tube measuring time of a tooth slot number is detected, the following formula is used

[0009] Sn = ( 1 / (60*Tn) )*60 rpm

[0010] Where n is the number of teeth, ranging from 1 to 60, S is the current rotation speed of the shaft, T is the time it takes for the teeth to rotate past the photoelectric tube, and rpm is the unit of rotation speed;

[0011] The error is then combined with the compensation coefficient K, through the following formula

[0012] S = Kn * Sn

[0013] The actual stable rotation speed of the current shaft is obtained, thereby predicting the stable rotation speed of the tooth slot that has not yet been measured.

[0014] Furthermore, the fixing part includes a circular chassis, a connecting fixing plate and a supporting plate. The connecting fixing plate is arranged on the circular chassis, the supporting plate is arranged on the connecting fixing plate, and concentric circular holes are arranged on the circular chassis, the connecting fixing plate and the supporting plate.

[0015] Furthermore, the grating plate includes a grating plate body and a connecting shaft, one end of the connecting shaft is fixed on the circular chassis of the fixing part, and the other end is connected to the grating plate body.

[0016] Furthermore, the photoelectric tube is arranged on the support plate of the fixed part. The photoelectric tube is generally n-shaped. Two upper and lower connecting bosses are arranged near the support plate. Connecting holes are arranged on the connecting bosses. The notch of the photoelectric tube covers the epitaxial tooth groove of the grating piece.

[0017] The beneficial effect of the present invention is that the present invention only needs to calculate the actual stable rotation speed of the current rotating shaft, so that we can calculate the current stable rotation speed when receiving any pulse time, without having to wait for the grating piece to complete a circle to calculate the stable rotation speed. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a structural diagram of the present invention;

[0019] Figure 2 It is a partial structural diagram of the present invention;

[0020] Figure 3 Modify the picture for the grating sheet of the present invention.

[0021] Markings in the figure: fixed part 1, grating plate 2 and photoelectric tube 3. DETAILED DESCRIPTION

[0022] The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments.

[0023] A measuring system for quickly obtaining a rotation speed by using a grating piece 2 installed on a motor shaft comprises a fixing part 1, a grating piece 2 and a photoelectric tube 3. The fixing part 1 comprises a circular chassis, a connecting fixing plate and a supporting plate, wherein the connecting fixing plate is arranged on the circular chassis, and the supporting plate is arranged on the connecting fixing plate, and concentric circular holes are arranged on the circular chassis, the connecting fixing plate and the supporting plate, which are helpful to fix the grating piece 2 well and provide a long-lasting operation space. The grating piece 2 comprises a grating piece body and a connecting shaft, wherein one end of the connecting shaft is fixed on the circular chassis of the fixing part 1, and the other end is connected to the grating piece body. The connection method adopts bolts, which is convenient for adjustment and fixing, easy to disassemble and assemble, and has low maintenance cost. The photoelectric tube 3 is arranged on the supporting plate of the fixing part 1, and the photoelectric tube 3 is in an N-shape as a whole, and two upper and lower connecting bosses are arranged on the side close to the supporting plate, and a connecting hole is arranged on the connecting boss. The notch of the photoelectric tube 3 covers the outer tooth groove of the grating piece 2, so that the operation time of the part not blocked by the tooth groove can be quickly detected, and it is convenient to maintain and replace a section if there is a problem.

[0024] Its operation is as follows Figure 1 As shown, due to the processing and installation problems of the grating piece 2 and the rotating shaft, the concentricity of the installation and the consistency of the gap between the teeth of the grating piece 2 cannot be guaranteed, resulting in the measurement point photoelectric tube 3 The radius of each tooth groove of the grating piece 2 is inconsistent, that is, the spacing distance of the tooth grooves is inconsistent. In this way, at the same speed, the rotating shaft speed calculated by each tooth groove has a certain deviation and cannot represent the actual speed of the current rotating shaft. At this time, the data measured by rotating the grating piece 2 for one circle, that is, the interval time of all the teeth of the grating piece 2 must be measured, and the calculated speed is the stable speed of the current rotating shaft. In this way, it will be slow to obtain a stable and accurate speed. It takes at least one full circle to calculate it, which is not conducive to the rapid control of the motor speed.

[0025] Taking the grating 2 with 60 teeth as an example, when the motor rotates at a constant speed, the MCU measures the time it takes for each tooth to rotate through the photoelectric tube 3, which are represented by T1, T2, T3, ..., T60. The total time for one rotation is

[0026] T = T1+T2+T3+……+T60 Formula (1)

[0027] The current shaft speed

[0028] S = (1 / T)*60 rpm Formula (2)

[0029] The current calculated speed for each tooth slot

[0030] Sn = ( 1 / (60*Tn) )*60 rpm Where n is from 1 to 60 Formula (3)

[0031] In actual measurement, due to the fact that the machining clearance of each tooth groove of the grating plate 2 is not exactly the same, or the concentricity problem when installed on the rotating shaft, the Sn and S calculated by formula (1) and formula (2) here have certain errors. Therefore, if you want to use formula (3) to quickly obtain the rotation speed, the stability will be much worse, which is not conducive to some subsequent controls.

[0032] Use a file to make the gap of one of the tooth grooves of the grating plate 2 larger, such as Figure 2 As shown, when the grating 2 rotates at a constant speed, our MCU can detect a pulse width time that is significantly greater than the other pulse width times. We mark the maximum pulse width time as 1, and the numbers behind are arranged in sequence. In this way, the pulse time of each number can be obtained as T1' T2' T3' T4' ... T59' T60'. According to the above formula (3), the speed of each tooth slot can be calculated as S1 S2 S3 S4 ... S59 S60. At the same time, using the above formula (2), we can calculate the current stable speed S, so that the error compensation coefficient of each tooth slot can be calculated:

[0033] Kn = S / Sn Where n is from 1 to 60 Formula (4)

[0034] This compensation coefficient Kn is caused by the processing and installation accuracy of the actual grating plate 2 and is an inherent characteristic. Thus, when measuring the actual rotation speed, once we measure the pulse width time of a tooth slot number such as Tn, we can calculate the rotation speed Sn calculated from the tooth slot data through the above formula (3), and use the following compensation formula

[0035] S = Kn * Sn Formula (5)

[0036] Calculate the actual stable speed of the current shaft, so that we can calculate the current stable speed when receiving any pulse time, without waiting for the grating 2 to complete a circle to calculate the stable speed. Therefore, we only need to change the shape of one of the tooth slots to obtain the mark of each tooth slot. With the mark, the compensation coefficient of each tooth slot can be calculated by the formula. The stable speed can be quickly calculated by the compensation coefficient, so as to facilitate more accurate real-time control, such as PID closed-loop control.

[0037] The above is only a preferred embodiment of the present invention. It should be pointed out that ordinary technicians in this technical field can make several improvements and modifications without departing from the concept of the present invention. These improvements and modifications should also be regarded as within the scope of protection of the present invention.

Claims

1. A measurement system for quickly acquiring the rotation speed by using a grating sheet installed on the motor shaft, characterized in that: The method comprises a fixing part, a grating sheet and a photoelectric tube, and specifically comprises the following steps: 101) Count the number of teeth on the grating, and select any tooth to expand it to the largest gap, and mark it as No.

1. Use the MCU to measure the time it takes for each tooth to rotate through the photoelectric tube, and mark all the teeth. According to the time, the rotation speed of the tooth can be obtained; 102) Obtaining a compensation coefficient for each tooth slot, obtaining a current stable speed according to the measured speed, and thereby obtaining an error compensation coefficient for each tooth slot in combination with the speed of each tooth slot; Kn = S / Sn Where n is the number of tooth slots, 1 to 60, S is the current rotation speed of the shaft, and Sn is the current rotation speed of a tooth slot; 103) Predict the speed. When the photoelectric tube measuring time of a tooth slot number is detected, the following formula is used Sn=(1 / (60*Tn))*60rpm Where T is the time it takes for a tooth slot to rotate past the photoelectric tube, Tn is the time it takes for a current tooth slot to rotate past the photoelectric tube; rpm is the unit of speed; Therefore, combined with the error compensation coefficient of each tooth slot, the following formula is used S=Kn*Sn The actual stable rotation speed of the current shaft is obtained, thereby predicting the stable rotation speed of the tooth slot that has not yet been measured.

2. A measurement system for quickly acquiring the rotation speed by using a grating sheet installed on the motor shaft according to claim 1, characterized in that: The fixing part comprises a circular bottom plate, a connecting fixing plate and a supporting plate. The connecting fixing plate is arranged on the circular bottom plate, the supporting plate is arranged on the connecting fixing plate, and concentric circular holes are arranged on the circular bottom plate, the connecting fixing plate and the supporting plate.

3. A measurement system for quickly acquiring the rotation speed by using a grating sheet installed on the motor shaft according to claim 2, characterized in that: The grating sheet comprises a grating sheet body and a connecting shaft, one end of the connecting shaft is fixed on a circular bottom plate of a fixing part, and the other end is connected to the grating sheet body.

4. A measurement system for quickly acquiring the rotation speed by using a grating sheet installed on the motor shaft according to claim 2, characterized in that: The photoelectric tube is arranged on the support plate of the fixed part. The photoelectric tube is in an N shape as a whole. Two upper and lower connecting bosses are arranged near the support plate. The connecting bosses are provided with connecting holes. The notch of the photoelectric tube covers the epitaxial tooth groove of the grating piece.

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