JP3849729B2 - Rotation angle calculation device in encoder pulse switching - Google Patents

Description

時間当たりの変化量が一定の場合（一定速度でエンコーダが回転している状態）では、ＭＰＵ内部角度は、図２のようになる。時間当りの変化量が一定なので傾きは一定となり（単調増加）、３２ビットで１回転して０にもどる。
【００１０】
９００００パルス発生器１３が選択された場合の計算式も同様に、次のようになる。

切替後、前回ＭＰＵ内部角度を初期値とすることで、原点復帰することなく連続して角度算出をすることができる。
切替時のパルスカウンタ４の入力パルスについて述べる。
４０９６パルス発生器１２と９００００パルス発生器１３の出力が図３のようになっているとする。なお、図３に示す９００００パルスについては分かり易くするため、その時間軸を４０９６パルスに比べて拡大して図示している。
【００１１】
両パルス発生器１２、１３間の切替点（ａ）、（ｂ）、（ｃ）点ような、切替点の前後でパルスのハイレベル、ローレベルの状態が違うところでは誤パルスが発生し、パルスカウンタはパルスが変化したものとしてパルスの１カウント分の誤検出を招き、角度演算に誤差を生じる。すなわち、パルス発生器１２からパルス発生器１３へと、点（ａ）にて切替が起こった場合のパルスカウンタへの入力波形は、図４のようになる。
この誤差の補正方法について述ベる。
切替後に最初に原点パルスを検出した時のエンコーダ回転角度について、予め一定の設定値を用意して不揮発メモリ等に格納しておく。
この設定値としては、例えば、エンコーダがサーボモータ等の有磁電動機のシャフトに取り付けられている場合を説明する。エンコーダの原点パルスとサーボモータの磁気位置が一致するように取り付けると、設定値は０となる。また、サーボモータを工作機械の主軸モータなどに用いられるビルトイン構造とした場合、エンコーダの原点パルスとサーボモータの磁気位置を正確に位置決めして取り付けることが難しい。これは、ビルトイン構造の場合、サーボモータとエンコーダを工作機械に組み込む時、焼ばめなどの工程を必要とするためである。この場合は、組み込み後、エンコーダの原点パルスとサーボモータの磁気位置のずれを測定し、その値を設定値として設定する。
【００１２】
そして、切替後に最初の原点パルスの検出に同期して、それまでのＭＰＵ内部角度に代えて不揮発メモリに格納してある設定値を用いて置換える。
補正方法を図面に基づいて具体的に説明する。図５は回転角度の補正方法を説明するための図である。同図において、４０９６パルス発生器１２から９００００パルス発生器１３への切替がＡ点で起こり、切替時に角度誤差が生じた場合を点線より落込んだ実線で表わしている。切替後は落込んだ実線に沿ってパルスカウント値が増加するものの、そのカウント値は誤差を含んだままである。そこで、切替後に最初に原点パルスを検出した時点Ｂで、それまでのパルスカウント値に代えて予め用意した設定値で置換えることにより落込む前の元の実線上に戻ることができるので、角度誤差が補正されたことになる。
【００１３】
次に、第２の実施例について説明する。
原点パルス検出は、図６に示すように、時計回りか反時計回りのいづれの回転方向かにより、回転角度が原点の幅分だけ異なる。そこで、角度演算部では、予め原点パルス幅の角度分を不揮発メモリ等に格納しておく。原点パルス検出時は、回転方向により、そのまま設定値を使用する場合と、さらに設定値に原点パルスの幅分を補正する場合とに分けて実施をすることによって、より精密に角度誤差を補正することができる。
【００１４】
【発明の効果】
以上述べたように、本発明によれば、２種類以上の出力パルスをもつエンコーダにおける回転角度算出装置において、１つのパルスカウンタを用い、出力パルス切替が行われても、その後の最初の原点パルス検出に同期してカウント誤差を補正するので、原点復帰動作なしに連続した角度算出を行うことができる。
また、工作機械の主軸に用いられるビルトイン構造の場合、エンコーダの原点パルスとサーボモータの磁極位置を正確に位置決めして取り付けることが難しいが、この場合、エンコーダの原点パルスとサーボモータの磁極位置のずれを設定値とすることで、組み立て作業を平易にすることができる。さらに、回転方向によって原点パルス幅の角度分をも補正することができる。
【図面の簡単な説明】
【図１】本発明の回転角度算出装置のブロック図
【図２】ＭＰＵ内部で算出される回転角度を表す図
【図３】４０９６パルス発生器と９００００パルス発生器の出力パルスの図
【図４】切替が起こった場合のパルスカウンタへの入力波形図
【図５】回転角度の補正方法を表す図
【図６】原点パルスラッチ時の回転方向と設定位置を表す図
【図７】従来の回転角度算出装置のブロック図
【符号の説明】
１ 回転位置発生器
１１ 原点パルス発生器
１２ ４０９６パルス発生器
１３ ９００００パルス発生器
２ 原点パルスラッチ判断部
３ パルス列切替部
４ パルスカウンタ
５ 角度演算部
６ パルス列切替信号
２０ 回転位置発生器
２１ 原点パルス発生器
２２ ４０９６パルス発生器
２３ ９００００パルス発生器
２４ 原点パルスラッチ判断部
２５ 第１パルスカウンタ
２６ 第２パルスカウンタ
２７ 第１角度演算部
２８ 第２角度演算部
２９ パルス列切替信号[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an angle calculation apparatus that detects an angle of rotation by an encoder, and more particularly to an apparatus that uses an encoder having two or more different output pulses and calculates the angle by switching each output pulse.
[0002]
[Prior art]
Conventionally, as a method of calculating the rotation angle by switching between encoders having two different output pulses, the origin return operation is performed to acquire the origin pulse in order to obtain the initial position of the rotation angle after switching the output pulse. There was a thing. The rotation angle calculated by the N pulse generator (for example, 4096 pulses / rotation) is calculated as an angle of 360/4096 (°) per encoder output pulse. The rotation angle calculation by the M pulse generator (for example, 90000 pulses / rotation) is calculated as an angle of 360/90000 (°) per encoder output pulse. After switching, the origin return operation is performed by the origin pulse, the initial value of the angle calculation is set in synchronization with the origin pulse capture, and the angle is calculated by counting the number of pulses thereafter.
[0003]
FIG. 7 is a block diagram of a conventional rotation angle calculation device. As shown in FIG. 7, there is no pulse train switching unit, pulse counters 25 and 26 are attached to each output pulse, and two angles are added. There is a method in which the calculation units 27 and 28 always calculate two angles.
[0004]
[Problems to be solved by the invention]
However, in the former method, after the output pulse is switched, there is a problem that an origin return operation for obtaining the initial value of the rotation angle is required, and continuous work cannot be performed. For example, the origin return operation on the spindle of a machine tool (lathe) reduces work efficiency as wasted time during which cutting work cannot be performed. In the latter method, the number of pulse counters is two, which increases the price. In addition, the calculation of two angles has to be performed at all times, which increases the calculation time.
Accordingly, the present invention provides an angle calculation device that does not perform a return to origin operation even when output pulses are switched, and that can perform continuous angle calculation without increasing the pulse counter, in order to solve the drawbacks of the prior art. The purpose is to do.
[0005]
[Means for Solving the Problems]
In order to solve the above problems, the present invention provides an N pulse generator generated at a rate of N pulses / rotation, an M pulse generator (N ≠ M) generated at a rate of M pulses / rotation, and 1 pulse / rotation. A rotation position generator that outputs three types of pulse trains of the origin pulse generator that is generated at a rate of, a pulse train switching unit that switches the pulse trains output from the N pulse generator and the M pulse generator, and the pulse train switching unit A rotation angle having a pulse counter that counts the number of pulses, an origin pulse latch determination unit that detects an origin pulse that is an output of the origin pulse generator, and an angle calculation unit that calculates a rotation angle based on the output of the pulse counter In the calculation device, when the N pulse generator and the M pulse generator are switched by the pulse train switching unit, the angle calculation unit performs a pulse change after switching. Switch to the rotation angle calculation in accordance with the generator, further the origin pulse latch determination unit in synchronism with capture of the first origin pulse after switching by the encoder pulse to replace the previously provided set value of the rotation angle value so far It is a rotation angle calculation device for switching.
[0006]
Further, an angle value corresponding to the origin pulse width in the N pulse generator and the M pulse generator is stored in a non-volatile memory, and the set value is corrected by the width of the origin pulse according to the rotation direction. It is characterized by.
[0007]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 is a block diagram of a rotation angle calculation apparatus of the present invention. In the figure, reference numeral 1 denotes a rotational position generator (encoder) including an origin pulse generator 11, a 4096 pulse generator 12 and a 90000 pulse generator 13 which are generated at a rate of 1 pulse / rotation. Outputs of the 4096 pulse generator 12 and the 90000 pulse generator 13 are connected to the pulse counter 4 via the pulse train switching unit 3. In response to the pulse train switching signal 6, the pulse train switching section 3 connects the output of either the 4096 pulse generator 12 or the 90000 pulse generator 13 to the pulse counter 4. The pulse train switching signal 6 is connected to the angle calculation unit 5 and conveys information on whether the output pulse train is the 4096 pulse generator 12 or the 90000 pulse generator 13. Reference numeral 2 denotes an origin pulse latch determination unit that detects an origin pulse output from the origin pulse generator 11 and notifies the angle calculation calculation unit 5 that the origin pulse has been detected.
[0008]
First, angle calculation when the 4096 pulse generator 12 is selected will be described. The pulse train switching signal 6 outputs a connection command to the 4096 pulse generator 12. In response to this, the pulse train switching unit 3 connects the 4096 pulse generator 12 and the pulse counter 4, and the angle calculation unit 5 calculates the amount of pulse change per time as 360 ° / 4096 pulses and calculates the rotation angle. in this case,
Rotation angle = 360 ° / 4096 pulses (1)
It becomes.
In addition, the angle calculation when switching to the 90000 pulse generator 13 will be described. The pulse train switching signal 6 outputs a connection command to the 90000 pulse generator 13. In response to this, the pulse train switching unit 3 connects the 90000 pulse generator 13 and the pulse counter 4, and the angle calculation unit 5 calculates the rotation angle by calculating the amount of pulse change per time as 360 ° / 90,000 pulses. in this case,
Rotation angle = 360 ° / 90,000 pulses (2)
It becomes.
[0009]
Next, the calculation by the angle calculator 5 will be described in detail. The angle calculation unit 5 is configured by using a microprocessor (MPU), and replaces 360 ° of one rotation with a digital quantity inside the MPU (for example, 32 bits = 4294967296 is set to 360 °).
The calculation formula when the 4096 pulse generator 12 is selected is as follows.

When the amount of change per time is constant (in a state where the encoder is rotating at a constant speed), the MPU internal angle is as shown in FIG. Since the amount of change per time is constant, the slope is constant (monotonically increasing), and rotates once in 32 bits and returns to zero.
[0010]
Similarly, the calculation formula when the 90000 pulse generator 13 is selected is as follows.

After switching, by setting the previous MPU internal angle as an initial value, the angle can be calculated continuously without returning to the origin.
An input pulse of the pulse counter 4 at the time of switching will be described.
Assume that the outputs of the 4096 pulse generator 12 and the 90000 pulse generator 13 are as shown in FIG. For the sake of clarity, the 90000 pulse shown in FIG. 3 is illustrated with its time axis enlarged compared to 4096 pulses.
[0011]
An erroneous pulse is generated where the high and low levels of the pulse are different before and after the switching point, such as the switching points (a), (b), and (c) between the two pulse generators 12 and 13. The pulse counter causes an erroneous detection for one count of pulses, assuming that the pulse has changed, and causes an error in angle calculation. That is, the input waveform to the pulse counter when switching from the pulse generator 12 to the pulse generator 13 occurs at the point (a) is as shown in FIG.
A method for correcting this error will be described.
For the encoder rotation angle when the origin pulse is first detected after switching, a predetermined set value is prepared in advance and stored in a nonvolatile memory or the like.
As this set value, for example, a case where the encoder is attached to the shaft of a magnetic motor such as a servo motor will be described. If the encoder's origin pulse and the servo motor's magnetic position are matched, the set value is zero. Further, when the servo motor has a built-in structure used for a spindle motor of a machine tool or the like, it is difficult to accurately position and attach the origin pulse of the encoder and the magnetic position of the servo motor. This is because the built-in structure requires a process such as shrink fitting when the servo motor and the encoder are incorporated into the machine tool. In this case, after installation, the deviation between the encoder origin pulse and the servo motor magnetic position is measured, and the value is set as a set value.
[0012]
Then, in synchronization with the detection of the first origin pulse after switching, the setting value stored in the non-volatile memory is replaced in place of the MPU internal angle so far.
The correction method will be specifically described with reference to the drawings. FIG. 5 is a diagram for explaining a method of correcting the rotation angle. In the figure, the case where the switching from the 4096 pulse generator 12 to the 90000 pulse generator 13 occurs at point A and an angle error occurs at the time of switching is represented by a solid line dropped from the dotted line. After switching, the pulse count value increases along the dropped solid line, but the count value still contains an error. Therefore, at the time point B when the origin pulse is detected for the first time after switching, it is possible to return to the original solid line before dropping by replacing with the preset value instead of the previous pulse count value. The error has been corrected.
[0013]
Next, a second embodiment will be described.
In the origin pulse detection, as shown in FIG. 6, the rotation angle differs by the width of the origin depending on whether the rotation direction is clockwise or counterclockwise. Therefore, the angle calculation unit stores the angle of the origin pulse width in advance in a nonvolatile memory or the like. When detecting the origin pulse, the angle error is corrected more precisely by performing the process separately for the case where the set value is used as it is and the case where the width of the origin pulse is corrected to the set value depending on the rotation direction. be able to.
[0014]
【The invention's effect】
As described above, according to the present invention, in the rotation angle calculation apparatus in an encoder having two or more types of output pulses, even if output pulse switching is performed using one pulse counter, the first origin pulse after that is changed. Since the count error is corrected in synchronization with the detection, it is possible to perform continuous angle calculation without the origin return operation.
In addition, in the case of a built-in structure used for the spindle of a machine tool, it is difficult to accurately position and install the encoder origin pulse and the servo motor magnetic pole position. By making the deviation a set value, the assembly work can be simplified. Further, the angle of the origin pulse width can be corrected according to the rotation direction.
[Brief description of the drawings]
FIG. 1 is a block diagram of a rotation angle calculation device of the present invention. FIG. 2 is a diagram showing a rotation angle calculated inside an MPU. FIG. 3 is a diagram of output pulses of a 4096 pulse generator and a 90000 pulse generator. [Figure 5] Figure showing the input waveform to the pulse counter when switching occurs [Figure 5] Figure showing the rotation angle correction method [Figure 6] Figure showing the rotation direction and setting position at the time of origin pulse latching [Figure 7] Conventional rotation Block diagram of angle calculation device [Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Rotation position generator 11 Origin pulse generator 12 4096 pulse generator 13 90000 pulse generator 2 Origin pulse latch judgment part 3 Pulse train switching part 4 Pulse counter 5 Angle calculation part 6 Pulse train switching signal 20 Rotation position generator 21 Origin pulse generation 22 4096 pulse generator 23 90000 pulse generator 24 origin pulse latch determination unit 25 first pulse counter 26 second pulse counter 27 first angle calculation unit 28 second angle calculation unit 29 pulse train switching signal

Claims (2)

N pulse generator that generates at a rate of N pulses / rotation, M pulse generator that generates at a rate of M pulses / rotation (N ≠ M), and an origin pulse generator that generates at a rate of 1 pulse / rotation A rotation position generator for outputting a pulse train; a pulse train switching portion for switching pulse trains output from the N pulse generator and the M pulse generator; a pulse counter for counting the number of pulses from the pulse train switching portion; and the origin pulse In the rotation angle calculation device comprising an origin pulse latch determination unit that detects an origin pulse that is an output of the generator and an angle calculation unit that calculates a rotation angle based on the output of the pulse counter, the pulse train switching unit generates the N pulses. When the generator and the M pulse generator are switched, the angle calculation unit switches to the rotation angle calculation corresponding to the switched pulse generator. Further in synchronization with the incorporation of the first origin pulse after switching by the origin pulse latch determination unit, the rotation angle calculation unit in the encoder pulse switching, characterized in that to replace the previously provided set value of the rotation angle value so far .  The angle calculation unit stores an angle value corresponding to the origin pulse width in the N pulse generator and the M pulse generator in the nonvolatile memory, and corrects the set value by the width of the origin pulse according to the rotation direction. The rotation angle calculation apparatus in encoder pulse switching according to claim 1, wherein

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