JP3860324B2 - Motor speed control device - Google Patents

Description

となる。したがって、速度検出値の補正には、速度検出値Ｎｄ（θ）に対して、以下のようなΔＮ（θ）を加えて修正することが必要になる。
ΔＮ（θ）＝Ｎｄ（θ）・ｒ／Ｒ・ｃｏｓ（θ−δ）
【００１６】
この修正手段を有する速度検出器２の回路の一例について、図３を用いて説明する。まずエンコーダ７からのＡ相、Ｂ相のパルス信号はパルス加工部２１に入る。このパルス加工部２１ではパルス数をカウントするためのＵＰ信号、ＤＯＷＮ信号、パルスの変化点を示すパルスエッジ信号を出力する。このうち、パルスエッジ信号により時間カウンタ２２の値をラッチ２３でラッチする。また、ＵＰ信号、ＤＯＷＮ信号はパルスカウンタ２４でカウントされ、現在角度データとなる。ラッチ２３の時間ラッチデータおよびパルスカウンタ２４のパルスカウントデータは、それぞれ差分演算する演算器２５ａ、２５ｂに入り、ここでサンプリングクロックφs毎の差分データΔＴとΔＰになって出力される。そして除算演算する演算器２５ｃでΔＰ／ΔＴが演算されて暫定速度検出値Ｎｄ（θ）が得られる。しかし、この暫定速度検出値Ｎｄ（θ）は、前述したような回転軸ずれによる誤差を含むものであり、以下、その補正について説明する。まずθ−δであるが、これはパルスカウンタ２４をエンコーダ７の原点信号であるＺ相信号が入力される毎に、メモリ２６ａにあらかじめ設定されている軸ずれ方向角−δで初期化してやることにより作ることができる。このθ−δのデータはｃｏｓ関数演算器２５ｄでｃｏｓ（θ−δ）となる。ここでｃｏｓ関数演算器２５ｄはデータテーブルを用いてもよいし、既知の演算方法を用いてもよい。次に、この結果は、乗算演算する演算器２５ｅで速度検出値Ｎｄ（θ）とあらかじめ設定されているメモリ２６ｂの軸ずれ率ｒ／Ｒと乗算される。こうして、速度補正値ΔＮ（θ）を作り、最後に加算演算する演算器２５ｆで速度検出値Ｎｄ（θ）との和をとって、補正後の速度検出値Ｎｄｅｔができる。この例では、ｃｏｓ関数演算器２５ｄ、乗算演算器２５ｅ、加算演算器２５ｆ、メモリ２６ａ、２６ｂが回転速度検出値を修正する修正手段である。
【００１７】
このように、本実施例によれば、エンコーダ中心とエンコーダ回転中心とのずれの誤差距離と、エンコーダ原点軸に対するずれ方向の角度と、を用いることにより、軸のずれを考慮して修正した正確な回転速度検出値を得ることができるため、軸への取付けにずれが生じていても、モータの回転速度を正確に速度指令値とするモータ速度制御装置とすることができる。
【００１８】
実施例２を説明する。本実施例２のモータ速度制御装置は、モータ軸又はモータ軸によって駆動される軸に取り付けられ、かつ、２相パルスを出力するロータリエンコーダからの出力パルス数及びパルス検出時間から回転速度検出値を求める速度検出器と、前記回転速度検出値と速度指令値とを比較して偏差を算出する比較器３、前記偏差を０とするよう電流指令を出力する速度制御器と、電流指令によりモータ駆動電流を出力する電流アンプと、を具備し、更に、モータの一定速度運転を行う一定運転手段と、エンコーダ出力パルス信号から求めた速度検出値の回転に同期して変動する変動量と位相角とにより、エンコーダ中心軸とエンコーダ回転中心軸とのずれの誤差距離及びエンコーダ原点軸に対する軸ずれ方向の角度を計算する計算手段と、を有している。
【００１９】
このモータ速度制御装置を使用すると、実施例１において必要な、軸ずれの誤差距離ｒ及び軸ずれ方向の角度δを算出することができる。すなわち、本実施例のモータ速度制御装置によって、モータを一定速度Ｎｏで回転させて、回転速度検出値Ｎｄ（θ）を得、そして、得られた回転速度検出値Ｎｄ（θ）とｓｉｎθと又はｃｏｓθとで、相関をとることで実現できる。まず、
Ｎｄ（θ）＝Ｎｏ・（１−ｒ／Ｒ・ｃｏｓ（θ−δ））
であるから、ｓｉｎθと相関をとると、
【数１】

同様に、ｃｏｓθと相関をとると、
【数２】

となる。ここで求めたＳとＣとにより、ｒ／Ｒとδが計算でき、軸ずれの誤差距離ｒと軸ずれ方向の角度δとを求めることができる。なお、積分処理は、十分に短い時間でＮｄ（θ）をサンプリングすることで容易に実行可能となる。
【００２０】
【発明の効果】
本発明は、エンコーダ回転軸ずれの影響を受けた速度検出値を補正して正しい速度を検出することができるようになり、その結果として、高い速度制御応答を持ったモータの速度制御装置を得ることができる。
【図面の簡単な説明】
【図１】速度制御装置の全体の制御ブロックの説明図。
【図２】エンコーダ回転軸のずれがパルス検出に及ぼす影響の説明図。
【図３】実施例のモータ速度制御装置の速度検出装置の一例の説明図。
【図４】エンコーダパルスと速度検出方法の説明図。
【符号の説明】
１ 速度制御装置
２ 速度検出器
２１ パルス加工部
２２ 時間カウンタ
２３ 時間データラッチ
２４ パルスカウンタ
２５ａ 時間カウンタ差分器
２５ｂ パルス入力カウンタ差分器
２５ｃ 除算器
２５ｄ ｃｏｓ演算器
２５ｅ 乗算器
２５ｆ 加算器
２６ａ 回転軸ずれ方向角度
２６ｂ 回転軸ずれ率
３ 速度差分の減算器
４ 速度制御器
５ 電流アンプ
６ モータ
７ 速度センサ
７１ スリット
７２ エンコーダスリット中心軸
７３ エンコーダ回転中心軸
７４ エンコーダ原点軸
７５ エンコーダ回転中心ずれ軸
７６ スリット検出線
７７ スリット検出点[0001]
BACKGROUND OF THE INVENTION
The present invention is a motor speed control device, and in particular, the motor speed can be controlled by detecting the motor speed using a rotary encoder signal having a two-phase pulse output and a pulse output indicating the origin position. The present invention relates to an encoder speed detection method in a simple motor speed control device.
[0002]
[Prior art]
A motor speed control device having speed feedback is conventionally known. As shown in FIG. 1, the motor control control device 1 includes a speed detector 2, a comparator 3, a speed controller 4, and a current amplifier 5. A speed detection sensor 7 is directly attached to the motor shaft of the motor 6 to be controlled or a shaft driven by the motor shaft, and the output signal of the speed detection sensor 7 is converted into a speed detection signal by the speed detector 2, Next, the comparator 3 calculates the difference between the speed detection signal and the speed command signal Nref given to the motor speed control device, and gives the deviation to the speed controller 4. The speed controller 4 gives a current command to the current amplifier 5 so that the speed deviation is zero, and the current amplifier 5 outputs a motor drive current. Thus, the motor 6 automatically rotates at the speed given by the speed command signal. An analog output tachometer or the like may be used as the speed detection sensor 7, but with the digitization of the speed control device, a two-phase pulse output rotary encoder capable of highly accurate speed detection may be used. It has increased.
[0003]
Among these rotary encoders, for example, in the case of an optical rotary encoder, a disk with slits arranged on the circumference precisely at equal intervals, and a light emitting element and a light receiving element arranged between the disks. The light is applied to the light receiving element from the slit portion. Therefore, when the disk rotates, light hits the light receiving element at the interval of the slit, and a periodic signal synchronized with the rotation angle is output from the light receiving element. Although the output signal of the light receiving element is an analog signal, an appropriate threshold is provided so that the on / off duty is 50%, and the waveform is shaped and output as a pulse signal. In a general rotary encoder, two light receiving elements are arranged with an interval of 1/4 of the slit interval. As a result of waveform shaping of each output and output as a pulse, the two output pulses have a 1/4 cycle. It will have a phase difference. Depending on the encoder, two types of slits with a ¼ period deviation are provided, and two light receiving elements located at the same position with respect to rotation receive the light passing through each slit and output phase difference pulses. Some are doing it.
[0004]
The optical rotary encoder with the two-phase pulse output as described above outputs the A-phase and B-phase pulses as shown in FIG. 4 with respect to the constant speed rotation of the shaft. A method for detecting the speed will be described below. First, in a digital speed control apparatus, speed control is generally performed at regular time intervals, and speed detection is also performed in synchronization with the control period at regular time intervals. This speed detection first requires the number of encoder pulses, which is counted at the rising and falling edges of the A-phase and B-phase encoder signals. Referring to FIG. 4, the number of pulses is 0 when the rise of the A phase occurs when the B phase is 0, the number of pulses is 1 at the next rise of the B phase, and the number of pulses at the next fall of the A phase. For example, the count is incremented at the edge of each pulse. In the case of reverse rotation, the countdown is performed at the A-phase and B-phase pulse edges. That is, the number of pulses is increased / decreased by a combination of the change of one pulse signal and the state of the other pulse signal. According to this method, the number of pulses is four times the actual number of encoder pulses, but this method is widely used in order to increase the resolution of speed detection.
[0005]
In FIG. 4, if the sampling for speed detection is performed at the time S0, S1, S2, and S3, the number of pulses in each sampling is 0, 2, 4, and 7, respectively. Since the sampling time interval is constant, there is a method of dividing the increase value of the number of pulses in one sampling interval by the sampling time to obtain a speed detection value, but the resolution of the speed detection value becomes very coarse. Normally, the speed is calculated using the time when the number of pulses changes. That is, the time when the pulse edges of P0, P1, P2, and P3 are input is also sampled to obtain respective time difference values t1, t2, and t3, and an accurate speed can be obtained by dividing the pulse number difference value by this time difference value. Will be required. In the example of FIG. 4, if the pulse interval (cycle) has a predetermined value, an accurate rotation speed can be obtained in any sampling by dividing the pulse difference value by each time difference value. It will be.
[0006]
However, the conventional speed detection method is based on the premise that the slit interval of the encoder is exactly constant at any rotation angle. Therefore, the slit interval of the encoder is unbalanced. If the center axis of the circumference of the slit and the actual center axis of rotation are shifted, the slit detection interval varies depending on the rotation angle, resulting in an error in the speed detection value. Looking at the actual encoder, the slits are processed by ultra-fine processing, so that there is almost no imbalance between the slits. However, the attachment of the slit disk of the encoder to the rotating shaft is mechanical, and it is unavoidable that the slit central axis and the rotating central shaft are displaced.
[0007]
This effect will be described below with reference to FIG. FIG. 2 shows the slits 71, which are arranged at equal intervals around the slit central axis 72. The slit 71 is detected at a point having a distance R from the slit central axis 72, and the slit interval is naturally constant on the circumference. However, if the center axis of rotation is at a point 73 deviated from the slit center axis 72 by a distance r, a circle having a distance R from here becomes a slit detection point, which becomes a circle 76. On this circle 76, the slit interval becomes non-uniform, and for example, the slit interval in the direction of the shift axis 75 of the rotation center axis with respect to the slit center 72 is (1 + r / R) times the regular interval. This error also appears in the speed detection value as it is, and if control is performed with such a speed detection value, torque ripple and speed ripple synchronized with rotation become impossible, and high-performance speed control cannot be performed. To deal with such problems, the conventional technology has been used where stable control can be achieved by lowering the speed control gain. However, in applications where a high speed control response is required, high encoder mounting accuracy must be ensured. It was not.
[0008]
[Problems to be solved by the invention]
An object of the present invention is to provide an encoder speed detecting device in a motor speed control device that solves the above-described problems and enables control with higher response.
[0009]
[Means for Solving the Problems]
The present invention relates to a speed detector that is attached to a motor shaft or a shaft driven by a motor shaft and obtains a rotational speed detection value from the number of output pulses and a pulse detection time from a rotary encoder that outputs a two-phase pulse, A comparator that calculates a deviation by comparing the rotational speed detection value and the speed command value, a speed controller that outputs a current command based on the deviation, and a current amplifier that outputs a motor drive current based on the current command. In the motor speed control apparatus provided, the speed detector rotates using a correction value calculated from an error distance of deviation between the encoder central axis and the encoder rotation central axis and an angle in the axis deviation direction with respect to the encoder origin axis. It is a motor speed control apparatus which has a correction means which corrects a speed detection value.
[0010]
The present invention also relates to a speed detector that is attached to a motor shaft or a shaft driven by the motor shaft and obtains a rotational speed detection value from the number of output pulses and a pulse detection time from a rotary encoder that outputs a two-phase pulse. A comparator that calculates a deviation by comparing the rotational speed detection value with a speed command value, a speed controller that outputs a current command based on the deviation, and a current amplifier that outputs a motor drive current based on the current command; In the motor speed control device comprising: a constant operation means for performing a constant speed operation of the motor, and a fluctuation amount and a phase angle that vary in synchronization with the rotation of the speed detection value obtained from the encoder output pulse signal. A calculation means for calculating an error distance of deviation between the axis and the encoder rotation center axis and an angle of the axis deviation direction with respect to the encoder origin axis. A speed controller.
[0011]
In the present invention, the speed detector uses a correction value calculated by the error distance of the deviation between the encoder central axis and the encoder rotation central axis calculated by the calculation means and the angle in the axis deviation direction with respect to the encoder origin axis. It is a motor speed control device having a correction means for correcting a rotation speed detection value.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described.
Hereinafter, the Example about the motor speed control apparatus of this invention is described using FIGS. 1-4. FIG. 1 is an explanatory diagram of the entire control block of the speed control apparatus. FIG. 2 is an explanatory diagram of the effect of encoder rotation axis deviation on pulse detection. FIG. 3 is an explanatory diagram of an example of a speed detection device of the motor speed control device according to the embodiment. FIG. 4 is an explanatory diagram of the encoder pulse and speed detection method.
[0013]
Example 1 will be described. As shown in FIG. 1, the motor speed control device 1 of this embodiment includes a speed detector 2, a comparator 3, a speed controller 4, and a current amplifier 5. Since the speed detector 2 is different from the conventional example, it will be described later. The comparator 3, the speed controller 4, and the current amplifier 5 are the same as in the conventional example. The comparator 3 compares the rotational speed detection value from the speed detector 2 with the input speed command value and calculates a deviation. The speed controller 4 outputs a current command so that the deviation from the comparator 3 is zero. The current amplifier 5 outputs a motor drive current according to a current command from the speed controller 4. With this motor drive current, the motor 6 rotates at the rotational speed of the input speed command value.
[0014]
The speed detector 2 in the motor speed control apparatus 1 of the present embodiment will be described. The speed detector 2 is attached to a motor shaft or a shaft driven by the motor shaft, and obtains a rotational speed detection value from the number of output pulses from the rotary encoder 7 that outputs a two-phase pulse and a pulse detection time. The speed detector 2 of the present embodiment uses the obtained rotational speed detection value as a provisional value, and corrects this provisional value. That is, there is a correcting means for correcting the provisional rotational speed detection value using a correction value calculated from the error distance of the deviation between the encoder central axis and the encoder rotation central axis and the angle in the axis deviation direction with respect to the encoder origin axis. ing. The error distance of deviation between the encoder central axis and the encoder rotation central axis and the angle in the axis deviation direction with respect to the encoder origin axis are set in advance. A method for obtaining the set value can be obtained by mechanical measurement, but can also be obtained by the method described in the second embodiment.
[0015]
The calculation of the correction amount will be specifically described with reference to FIG. FIG. 2 shows the slit 71 of the encoder, its center axis 72, and the actual rotation center axis 73. Let r be the distance between the slit central axis 72 and the actual rotational central axis 73 (axis deviation error distance). As the origin of rotation of the encoder, a Z-phase signal that is normally output by one pulse per rotation is used. The axis where this Z-phase exists is defined as the encoder origin axis 74. With respect to the encoder origin axis 74, a deviation axis 75 passing from the slit center axis 72 through the rotation center axis 73 is taken, and an angle with respect to the origin axis 74 (an angle in the axis deviation direction) is defined as δ. The circumference 76 through which the detection point of the slit passes by such an encoder is separated from the rotation center axis 73 by a distance R, and the speed detection point 77 at an angle θ from the origin axis on this circumference will be described. At this detection point 77, the width L (θ) of the slit is a width represented by the following equation, where the normal slit width is Lo.
L (θ) = Lo · (1 + r / R · cos (θ−δ))
For this reason, the speed detection value Nd (θ) is affected by the axis deviation depending on the value of the angle θ.

It becomes. Therefore, correction of the speed detection value requires correction by adding the following ΔN (θ) to the speed detection value Nd (θ).
ΔN (θ) = Nd (θ) · r / R · cos (θ−δ)
[0016]
An example of the circuit of the speed detector 2 having this correcting means will be described with reference to FIG. First, the A-phase and B-phase pulse signals from the encoder 7 enter the pulse processing unit 21. The pulse processing unit 21 outputs an UP signal for counting the number of pulses, a DOWN signal, and a pulse edge signal indicating a pulse change point. Among these, the value of the time counter 22 is latched by the latch 23 by the pulse edge signal. The UP signal and the DOWN signal are counted by the pulse counter 24 and become current angle data. The time latch data of the latch 23 and the pulse count data of the pulse counter 24 are respectively input to arithmetic units 25a and 25b for calculating a difference, and are output as differential data ΔT and ΔP for each sampling clock φs. Then, ΔP / ΔT is calculated by an arithmetic unit 25c that performs a division operation, and a provisional speed detection value Nd (θ) is obtained. However, the provisional speed detection value Nd (θ) includes an error due to the rotational axis deviation as described above, and the correction will be described below. First, θ−δ. This is done by initializing the pulse counter 24 with the axis deviation direction angle −δ set in advance in the memory 26a every time the Z-phase signal which is the origin signal of the encoder 7 is inputted. Can be made. This data of θ−δ becomes cos (θ−δ) by the cos function calculator 25d. Here, the cos function calculator 25d may use a data table or a known calculation method. Next, this result is multiplied by a speed detection value Nd (θ) and a preset axis deviation rate r / R in the memory 26b by a computing unit 25e that performs multiplication. In this way, the speed correction value ΔN (θ) is generated, and finally, the arithmetic unit 25f that performs the addition operation takes the sum with the speed detection value Nd (θ) to obtain the corrected speed detection value Ndet. In this example, the cos function calculator 25d, the multiplication calculator 25e, the addition calculator 25f, and the memories 26a and 26b are correction means for correcting the rotation speed detection value.
[0017]
As described above, according to the present embodiment, by using the error distance of the deviation between the encoder center and the encoder rotation center and the angle in the deviation direction with respect to the encoder origin axis, the correction is performed in consideration of the axis deviation. Therefore, even if there is a deviation in the attachment to the shaft, a motor speed control device that accurately sets the rotation speed of the motor as a speed command value can be obtained.
[0018]
A second embodiment will be described. The motor speed control device according to the second embodiment is attached to a motor shaft or a shaft driven by the motor shaft, and the rotation speed detection value is obtained from the number of output pulses and the pulse detection time from a rotary encoder that outputs a two-phase pulse. A speed detector to be calculated; a comparator 3 that compares the detected rotational speed value with a speed command value to calculate a deviation; a speed controller that outputs a current command so that the deviation becomes 0; A current amplifier for outputting a current, a constant operation means for performing a constant speed operation of the motor, a variation amount and a phase angle that vary in synchronization with the rotation of the speed detection value obtained from the encoder output pulse signal, And calculating means for calculating an error distance of deviation between the encoder center axis and the encoder rotation center axis and an angle in the axis deviation direction with respect to the encoder origin axis.
[0019]
When this motor speed control device is used, it is possible to calculate the axis deviation error distance r and the axis deviation direction angle δ necessary in the first embodiment. That is, the motor speed control device according to the present embodiment rotates the motor at a constant speed No to obtain the rotational speed detection value Nd (θ), and the obtained rotational speed detection value Nd (θ) and sin θ or This can be realized by taking a correlation with cos θ. First,
Nd (θ) = No · (1−r / R · cos (θ−δ))
Therefore, taking a correlation with sin θ,
[Expression 1]

Similarly, when correlated with cos θ,
[Expression 2]

It becomes. Based on S and C obtained here, r / R and δ can be calculated, and an axial deviation error distance r and an axial deviation angle δ can be obtained. The integration process can be easily executed by sampling Nd (θ) in a sufficiently short time.
[0020]
【The invention's effect】
The present invention makes it possible to detect a correct speed by correcting a speed detection value affected by the encoder rotational axis deviation, and as a result, obtain a motor speed control apparatus having a high speed control response. be able to.
[Brief description of the drawings]
FIG. 1 is an explanatory diagram of an overall control block of a speed control device.
FIG. 2 is an explanatory diagram of an influence of a deviation of an encoder rotation axis on pulse detection.
FIG. 3 is an explanatory diagram of an example of a speed detection device of the motor speed control device according to the embodiment.
FIG. 4 is an explanatory diagram of an encoder pulse and speed detection method.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Speed controller 2 Speed detector 21 Pulse processing part 22 Time counter 23 Time data latch 24 Pulse counter 25a Time counter differencer 25b Pulse input counter differencer 25c Divider 25d cos calculator 25e Multiplier 25f Adder 26a Rotation axis deviation Direction angle 26b Rotational axis deviation rate 3 Speed difference subtractor 4 Speed controller 5 Current amplifier 6 Motor 7 Speed sensor 71 Slit 72 Encoder slit center axis 73 Encoder rotation center axis 74 Encoder origin axis 75 Encoder rotation center deviation axis 76 Slit detection Line 77 Slit detection point

Claims (3)

A speed detector that is attached to a motor shaft or a shaft driven by the motor shaft and that obtains a rotational speed detection value from the number of output pulses and a pulse detection time from a rotary encoder that outputs a two-phase pulse, and the rotational speed detection value A motor speed comprising: a comparator that compares the speed command value with a speed command value to calculate a deviation; a speed controller that outputs a current command based on the deviation; and a current amplifier that outputs a motor drive current based on the current command. In the control device,
The speed detector corrects the rotation speed detection value using a correction value calculated from an error distance of deviation between the encoder central axis and the encoder rotation central axis and an angle in the axis deviation direction with respect to the encoder origin axis. A motor speed control device comprising: A speed detector that is attached to a motor shaft or a shaft driven by the motor shaft and that obtains a rotational speed detection value from the number of output pulses and a pulse detection time from a rotary encoder that outputs a two-phase pulse, and the rotational speed detection value A motor speed comprising: a comparator that compares the speed command value with a speed command value to calculate a deviation; a speed controller that outputs a current command based on the deviation; and a current amplifier that outputs a motor drive current based on the current command. In the control device,
The deviation between the encoder center axis and the encoder rotation center axis is determined by the constant operation means that performs constant speed operation of the motor and the fluctuation amount and phase angle that vary in synchronization with the rotation of the speed detection value obtained from the encoder output pulse signal. A motor speed control device comprising: calculation means for calculating an error distance and an angle of an axis deviation direction with respect to an encoder origin axis. The motor speed control device according to claim 2, wherein
The speed detector corrects the rotational speed detection value using a correction value calculated by the error distance of the deviation between the encoder central axis and the encoder rotation central axis calculated by the calculation means and the angle in the axis deviation direction with respect to the encoder origin axis. A motor speed control device characterized by comprising a correcting means.

Images