JP4123362B2 - Absolute position detection method for fully closed control device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention provides an absolute position detection of a fully closed control apparatus having an absolute encoder capable of detecting an absolute position at an arbitrary point and an incremental encoder having a reference point with an equal interval and capable of detecting only a distance from the nearest reference point. Regarding the method.
[0002]
[Prior art]
In a conventional full cruise control apparatus, an absolute encoder capable of detecting an absolute position at an arbitrary point is generally used as a position detector of a full closed control loop. In this case, the absolute position may be obtained by a procedure according to the specifications of the absolute encoder. For example, in the case of the absolute pulse scale of Futaba Electronics Industry Co., Ltd., the multi-rotation serial data transmitted from the A phase is read within a certain time after the power is turned on, and then one rotation output from the A phase and the B phase. The absolute position was detected by the procedure of receiving the internal incremental pulse by the counter.
[0003]
In addition, there has been proposed a method for detecting an absolute position without using an absolute encoder as a position detector of a fully closed control loop (see, for example, Patent Document 1).
[0004]
[Patent Document 1]
JP-A-5-88751
FIG. 6 is a diagram showing the configuration of a full cruise control apparatus that implements this conventional method. An absolute encoder 2 is attached to the motor 1, a main shaft 4 that is a movable part is attached to the output shaft of the motor 1 via a transmission mechanism system 3 such as a speed reducer, and an incremental encoder 5 is attached to the main shaft 4. Yes. Signals from the absolute encoder 2 and the incremental encoder 5 are input to the control device 6 ′, and the control device 6 ′ outputs a control signal to the motor 1. As described above, the incremental encoder 5 is used for the position detector of the fully closed control loop that controls the main shaft 4 as the movable part, and the absolute encoder 2 is used for the position detector of the semi-closed control loop that controls the motor 1. It was.
[0006]
FIG. 7 is a diagram showing the detection position of the absolute encoder 2, FIG. 8 is a diagram showing the detection position of the incremental encoder 5, and FIG. 9 is a diagram showing the detection position relationship between these two encoders 2 and 5 in detail. It is. Now, assuming that the detection position of the absolute encoder 2 is B and the count number of one rotation of the incremental encoder 5 is λ,
n × λ + R = B (1)
As a result, the multi-rotation number n and the remaining count number R are calculated.
[0007]
On the other hand, when the detection position of the incremental encoder 5 is s, the offset value δ is
δ = R−s (2)
Given in. Therefore, the current position is
Current position = n × λ + δ + s (3)
Given in.
[0008]
FIG. 10 is a flowchart showing an absolute position detection operation performed by the control device 6 ′. First, at step 201, the detection position B of the absolute encoder 2 and the detection position s of the incremental encoder 5 are read. Next, when the servo lock is started such as when the power is turned on, the routine proceeds from step 202 to 203, where the multi-rotation number n and the offset value δ are calculated and stored according to the above formulas (1) and (2). After that, in step 204, the current position of the spindle 4 is calculated based only on the count number from the incremental encoder 5 according to the equation (3), and feedback control is performed.
[0009]
As described above, in the absolute position detection method of the conventional full-closed control device, the absolute encoder detection position and the incremental encoder detection position are read, and when the position control function is started such as when the power is turned on, the multi-rotation speed and A procedure has been taken in which an offset value is obtained, and the absolute position is detected from the multi-rotation number and offset value as the initial value and the detection position of the incremental encoder.
[0010]
[Problems to be solved by the invention]
However, in the absolute position detection method of the conventional full-closed control device described above, the multirotation speed and the offset value are obtained as initial values from the detection positions of the two encoders each time the position control function such as when the power is turned on is started. Therefore, depending on the installation conditions of the two encoders and the error in the detection positions of the two encoders due to mechanical errors in the transmission mechanism system, the multi-rotation numerical value may be deviated by one each time. There is a problem that you can not.
[0011]
In view of such problems, the object of the present invention is that there is no restriction on the installation method of the two encoders, and the detection position error of the two encoders due to a mechanical error of the transmission mechanism system is within a certain value. Another object of the present invention is to provide an absolute position detection method for a fully closed control device, which can determine an absolute position on an incremental encoder.
[0012]
[Means for Solving the Problems]
In order to achieve the above object, an absolute position detection method for a fully closed control apparatus according to the present invention includes a step of reading detection positions of an absolute encoder and an incremental encoder, and a reference point of the incremental encoder at an origin of the absolute encoder. The nearest reference point is the origin of the incremental encoder, and the distance between the absolute encoder origin and the incremental encoder origin is once determined and stored, and the distance between the stored origins is detected from the incremental encoder origin. calculated by determining the number of equally spaced reference point nearest the reference point at the position, the number of the reference points, the distance between the reference point of the incremental encoder from the detected position of the incremental encoder, incremental Having a step of determining the absolute position of the encoder, the.
[0013]
In this way, the distance between the origins of the two encoders is obtained only once after installation, and the absolute position on the incremental encoder is obtained using the distance between the origins. If the error in the detection position of the two encoders is smaller than ± 1/4 of the distance between the reference points (absolute amount = 1/2), the absolute position on the incremental encoder can be set without limitation on the installation method of the two encoders. It can be determined uniquely.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
Next, embodiments of the present invention will be described with reference to the drawings.
[0015]
FIG. 1 is a diagram showing the configuration of a full-closed control device that implements the absolute position detection method of the present invention, and only the processing of the control device 6 is different from the conventional device of FIG.
[0016]
FIG. 2 is a diagram showing in detail the detection position relationship between the absolute encoder and the incremental encoder of FIG. 1, FIG. 2 (1) is the detection position of the absolute encoder 2 capable of detecting the absolute position B at an arbitrary point, and FIG. 2 (2). Indicates a detection position of the incremental encoder 5 having reference points of equal intervals λ and capable of detecting only the distance s from the nearest reference point. There are cases where there are several reference points at equal intervals λ within one rotation, there are cases where there are only one reference point, there are cases where there are linear scales arranged on a linear axis, and the reference points differ depending on the incremental encoder.
[0017]
FIG. 3 is a flowchart showing a processing procedure for detecting an absolute position in the control device 6.
[0018]
First, in step 101, the detection position is read according to the specifications of the encoders 2 and 5.
[0019]
In step 102, the detection position B of the absolute encoder 2 obtained in step 101 is determined by the difference in resolution between the two encoders 2 and 5 and the gear ratio of the transmission mechanism system 3 between the two encoders 2 and 5. It is converted into a position on the incremental encoder 5 at a ratio. For example, the resolution of the absolute encoder 2 is X pulses per revolution, the resolution of the incremental encoder 5 is Y pulses per revolution, and the incremental encoder 5 is rotated N times by M rotation of the absolute encoder 2 according to the gear ratio of the transmission mechanism 3. Assuming that, B is multiplied by a constant of (Y × N) / (X × M) and converted.
[0020]
In step 103, when the distance δ between the origins of the two encoders 2 and 5 is not stored, the distance δ between the origins is obtained. Consider the reference point closest to the absolute encoder origin as the origin of the incremental encoder 5, and set the distance δ between the origins to
n ₀ = (B−s) / λ (4)
δ = B− (n ₀ × λ + s) (5)
It is obtained by the following calculation. Here, s and δ are values in the range of −λ / 2 <s and δ ≦ λ / 2, but when the detected value s of the incremental encoder 5 is only a positive value, s and δ Is a value in the range of 0 ≦ s and δ <λ. Here, the calculation of n _{0 in} the equation (4) is rounded off after the decimal point. The exact rounding calculation is performed by, for example, comparing the value of (B−s) −n ₀ × λ with ± λ / 2 using n ₀ calculated once, and if it is larger than λ / 2, n _0. +1, and if it is -λ / 2 or less, n ₀ can be reduced by -1. In the example of FIG. 2, if 0 ≦ δ ≦ λ / 2, n ₀ = 3, and if −λ / 2 <δ <0, n ₀ = 4.
[0021]
In step 104, δ obtained in step 103 is stored. In the processing of step 103 and step 104, as shown in FIG. 4, the distance δ between the origins may be obtained every time and only δ may be stored once.
[0022]
The reason why the distance δ between the origins is calculated every time is to compare the calculated δ with the stored δ and use it for monitoring whether the error is within an allowable range.
[0023]
Finally, in step 105, using δ stored in step 104,
n = (B−δ−s) / λ (6)
A = n × λ + s (7)
The absolute position A of the incremental encoder 5 is obtained by the following calculation. Here, the calculation of n in the equation (6) is rounded off after the decimal point as in step 103. n becomes the same value as n _{0 in the} equation (4), and the following result is obtained in the example of FIG.
[0024]
A = 3λ + s (when 0 ≦ δ ≦ λ / 2) (8a)
A = 4λ + s (when −λ / 2 <δ <0) (8b)
Thus, the value of A changes by λ depending on the value of δ.
[0025]
Next, FIG. 5 shows the positional relationship between the absolute encoder 2 and the incremental encoder 5 when there is an error ε at the detection positions of the two encoders 2 and 5 due to a mechanical error of the transmission mechanism system 3. The operation will be specifically described. The absolute position detected by the absolute encoder 2 changes from B by an error ε to B ′. Then, the distance δ ′ between the origins obtained in step 103 is
n ₀ = (B′−s) / λ (9)
δ ′ = B ′ − (n ₀ × λ + s) (10)
Is given by the calculation In the example of FIG. 5, if 0 ≦ δ + ε ≦ λ / 2, n ₀ = 3, and if −λ / 2 <δ + ε <0, n ₀ = 4. In step 105, δ ′ stored in step 104 is used,
n = (B′−δ′−s) / λ (11)
A = n × λ + s (7)
The absolute position A is obtained by the following calculation. n becomes the same value as n _{0 in the} formula (9), and the following result is obtained in the example of FIG.
[0026]
A = 3λ + s (when 0 ≦ δ + ε ≦ λ / 2) (12a)
A = 4λ + s (when −λ / 2 <δ + ε <0) (12b)
Thus, the value of A changes by λ depending on the value of δ + ε.
[0027]
The results of the equations (12a) and (12b) are obtained by obtaining the absolute position of the incremental encoder 5 by obtaining the multi-rotation number n and the offset value δ every time the position control function such as when the power is turned on. This results in the same result as the conventional method. That is, it means that the value of δ + ε changes by 1 depending on whether 0 ≦ δ + ε ≦ λ / 2 or −λ / 2 <δ + ε <0, for example, δ is close to λ / 2. Under the installation conditions of the two encoders 2 and 5, the allowable range of the error ε becomes very small.
[0028]
Finally, it will be described that the absolute position A is uniquely determined by the method of the present invention if the error ε of the detection positions of the two encoders 2 and 5 is in the range of | ε | <λ / 4. Now, let B ′ be the absolute position detected by the absolute encoder 2 when the error ε = ε ′, and let δ ′ be the distance between the origins obtained in step 103. The distance δ ′ between the origins is stored, and the absolute position A when the error ε = ε ″ is obtained. N obtained in step 105 is as follows from the equations (10) and (11). However, the absolute position detected by the absolute encoder 2 when the error ε = ε ″ is B ″.
[0029]
n = (B ″ −δ′−s) / λ
= ((B + ε ″) − (B ′ − (n ₀ × λ + s)) − s) / λ
= ((B + ε ″) − ((B + ε ′) − (n ₀ × λ + s)) − s) / λ
= N ₀ + (ε ″ −ε ′) / λ (13)
Here, since | ε ′ | <λ / 4 and | ε ″ | <λ / 4, it is | ε ″ −ε ′ | <λ / 2, and n in the equation (13) is rounded off after the decimal point. As a result, it becomes equal to n ₀ . Further, n ₀ in this case is the one when error ε = ε ′, and n and n ₀ at that time are equal. From the above, since n when the error ε = ε ″ is equal to n when the error ε = ε ′, the absolute position A of the incremental encoder 5 obtained by the equation (7) is uniquely determined. Proven.
[0030]
【The invention's effect】
As described above, according to the present invention, even when the position detector of the fully closed loop is not an absolute encoder, the encoder has an equally spaced reference point and can detect only the distance from the nearest reference point. If there are two encoders, the absolute position of the semi-closed control loop can be detected and the error of the detection positions of the two encoders is less than ± 1/4 of the distance between the reference points. Without being limited to the method, there is an effect that it is possible to provide an absolute position detection method for a fully closed control device having an absolute position detection function.
[Brief description of the drawings]
FIG. 1 is a diagram showing a configuration of a fully closed control apparatus to which an absolute position detection method of the present invention is applied.
FIG. 2 is a diagram showing a positional relationship between an absolute encoder and an incremental encoder according to an embodiment of the present invention.
FIG. 3 is a flowchart showing a processing procedure of an absolute position detection operation performed by a control device 6;
FIG. 4 is a flowchart showing a processing procedure of a modification of the method of FIG. 3;
FIG. 5 is a diagram showing a positional relationship between an absolute encoder and an incremental encoder when there is an error in the detection positions of two encoders in an embodiment of the present invention.
FIG. 6 is a configuration diagram of a fully closed control device to which a conventional absolute position detection method is applied.
FIG. 7 is a diagram showing a detection position of an absolute encoder in a conventional method.
FIG. 8 is a diagram showing a detection position of an incremental encoder in a conventional method.
FIG. 9 is a diagram showing a positional relationship between an absolute encoder and an incremental encoder in a conventional method.
FIG. 10 is a flowchart showing a processing procedure of a conventional method.
[Explanation of symbols]
1 Motor 2 Absolute encoder 3 Transmission mechanism 4 Spindle 5 Incremental encoder 6, 6 'Controller B Detection position of absolute encoder 2 Detection position s of incremental encoder 5 Distance between reference points of incremental encoder 5 δ Absolute encoder origin and incremental encoder Distance from encoder origin ε Error in detection position of two encoders 2 and 5 Absolute position of incremental encoder 5

Claims (3)

An absolute position detection method for a fully closed control apparatus comprising an absolute encoder capable of detecting an absolute position at an arbitrary point and an incremental encoder having a reference point with equal intervals and capable of detecting only the distance from the nearest reference point. ,
Reading detection positions of the absolute encoder and the incremental encoder;
Among the reference points of the incremental encoder, the nearest reference point at the origin of the absolute encoder is set as the origin of the incremental encoder, and the distance between the origin of the absolute encoder and the origin of the incremental encoder is obtained once and stored, and
Using the distance between the stored origins, the number of equally spaced reference points from the incremental encoder origin to the nearest reference point at the detection position is obtained, and the number of the reference points and the incremental encoder reference point and distance from the detection position of the incremental encoder, and a step of calculating an absolute position of the incremental encoder, the absolute position detection method of a full-closed control system.   The detection positions of the absolute encoder and the incremental encoder are read, and the detection position of the absolute encoder is determined at a rate determined by the difference in resolution between the encoders and the gear ratio of the transmission mechanism system between the encoders. 2. The full position according to claim 1, wherein the distance between the origins is calculated by converting to an upper position, and calculating the absolute encoder position after conversion, the detection position of the incremental encoder, and the reference point interval of the incremental encoder. An absolute position detection method for a closed control device.   The distance between the origin of the absolute encoder and the origin of the incremental encoder is obtained once, and instead of storing the distance, the distance between the origins is obtained every time, and only the first obtained distance is stored. Absolute position detection method for a fully closed control device.

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