JP2004282914A - Driver of stepping motor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a driver of a stepping motor having an inexpensive high accuracy microdrive function of simple structure. <P>SOLUTION: The driver has a function for controlling the motor current according to a current command, and a detector for detecting the command rotor pole position. The driver is arranged to operate a positional deviation ε, i.e. the difference between a positional command θ* being given to a positional command input terminal and a rotor pole position θf detected by the position detector, to multiply the positional deviation ε by a coefficient through a coefficient unit, and to subtract the output of the coefficient unit from the positional command θ* thus producing an exciting angle command. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

ただし、Ｔは軸トルク、Ｔｍはモータ最大トルク、δは位置偏差である
また、振動抑制部２０を図２のように構成したときの振動抑制部出力λは数式２となる。
【数２】

ここで、ｋは係数器２１の設定値、θ＊は端子１０に加えられる位置指令、θたｆは位置検出器９２の出力であるロータ磁極位置である。
振動抑制部２０の出力λは電流指令の角度となるから、ロータ磁極位置θｆとλの位相差が偏差δと考えることができるから、数式３が成り立つ。
【数３】

数式３を数式１に代入して数式４を得る。
【数４】

数式４の関係を図３に示す。図３において（ａ）はｋ＝０の場合、（ｂ）はｋ＞０の場合（代表値としてｋ＝０．５）、（ｃ）はｋ＜０の場合（代表値としてｋ＝−０．５）を示している。また、ｋと最大トルク発生角度の関係を図４に示す。即ち、図４に示すとおり、係数器の設定値ｋの大きさを変えることで、最大トルク発生の角度を制御することができることが分かる。また、図３に示すとおり安定点における位置偏差対発生トルクの割合（軸剛性と称する）も変化させることができる。
図３における（ａ）のｋ＝０という条件は通常のステッピングモータのオープン駆動に対応することは明らかであるから、ｋを正の値に取ることで軸剛性を小さくすることができる。この結果、振動を低減することができる。
また、ｋを負の値に取ることで軸剛性を大きくすることができるから、停止位置精度を向上することができる。
【０００９】
【実施例】
図１は本発明の第１の実施例である。
図１において、ステッピングモータ９１に対してＰＷＭインバータ７０でモータに所定の電圧を印加し、モータを回転させる。電流検出器８１、８２はモータ相電流ｉαｆ、ｉβｆを検出し、該モータ相電流ｉαｆ、ｉβｆを第１の加算器３１及び第２の加算器３２の一方の入力とする。一方、第１相の電流振幅指令入力端子６１と第２相の電流振幅指令入力端子にそれぞれｉα＊及びｉβ＊を印加する。
加算器３１、３２は電流指令と帰還電流の差分である電流誤差を演算するものであり、該電流誤差を電流補償器４１、４２で増幅したのち、該ＰＷＭインバータ７０の入力としている。
【００１０】
図２は該調整部２０の詳細を示す図である。
角度演算器２１は比較２２の出力である位置偏差εを係数倍（ｋ倍）し、加算器２３（異符号であるため減算となる）の一方の入力に接続する。加算器２３の他方の入力には位置指令θ＊を接続し、出力λを得ている。
【００１１】
係数ｋを０＜ｋ＜１に取ると、該調整部２０の出力λは、ロータ磁極位置が指令に対して偏差を持つ場合、角度指令を直接励磁電流の角度指令に用いるよりも小さな指令変化を過渡的に与えることができるため、振動低減効果が得られる。
【００１２】
係数ｋをｋ＜０に取ると、該調整部２０の出力λは、ロータ磁極位置が指令に対して偏差を持つ場合、角度指令を直接励磁電流の角度指令に用いるよりも大きな指令変化を過渡的に与えることができるため、モータの軸剛性を大きくできる。
【００１３】
【発明の効果】
図６は本発明の第２の実施例である。
図６と図１の共通部は同一番号を付しているが、図６では、対象モータが３相ステッピングモータになり、３相−２相固定座標変換器６３、及び２相−３相固定座標変換器６４、電流センサ３３が追加されている他は、同一の構成である。３相電流を検出する場合、対称性を利用して、２つの電流センサ検出出力で第３相電流を演算することで第３相目の電流センサを省略することも可能である。
尚、第１及び第２の実施例に示す機能は、構成部品を少なくするためにマイクロプロセッサを用いて実現することも可能である。
【００１４】
【図面の簡単な説明】
【図１】本発明の第１の実施例である。
【図２】本発明の第１の実施例の部分説明図である。
【図３】本発明の原理説明のための角度対軸トルクの関係を示す説明図である。
【図４】本発明の係数器係数対最大トルク発生角度の関係を示す説明図である。
【図５】第１の従来例ブロック図である。
【図６】第２の従来例ブロック図である。
【００１４】
【符号の説明】
１０ 位置指令入力端子
２０ 調整部
２１ 係数器
２２、２３ 加算器
３１、３２ 加算器
４１ 第１相電流制御器
４２ 第２相電流制御器
５１ 第１相基本電流指令発生器
５２ 第２相基本電流指令発生器
６１ 第１相電流振幅指令入力端子
６２ 第２相電流振幅指令入力端子
７０ ＰＷＭインバータ
８１、８２ 電流検出器
９１ ステッピングモータ
９２ 位置検出器
１０１ 加算器
１０２ 加算器
１０３ 加算器
１０４ 加算器
１０５ 加算器
１１０ 位置制御器
１２０ 速度制御器
１３０ 第１の座標変換器
１４１ 第１の電流制御器
１４２ 第２の電流制御器
１５０ ＰＷＭインバータ
１５４ 第１の電流検出器
１５５ 第２の電流検出器
１６０ 第２の座標変換器
１７０ 三角関数発生器
１８０ ステッピングモータ
１９０ 位置検出器
【整理番号】Ｌ２００３−０５[0001]
[Industrial applications]
The present invention relates to a driving device for a stepping motor for controlling an angle and a speed.
[0002]
[Prior art]
The motor is required to be able to rotate over a wide range with low vibration and low noise in accordance with the sophistication of the device.However, the stepping motor is stepped by switching the energization state of each winding instantaneously every time an external command pulse is applied. Because of the rotation, reduction of vibration noise generated at the time of switching of current and prevention of loss of synchronization are issues.
In order to reduce vibration noise and prevent loss of synchronism, a micro step drive in which a winding current is smoothly changed using a pulse width modulation (hereinafter referred to as PWM) inverter is generally used. FIG. 5 is a block diagram of a micro step driving circuit according to the prior art.
[0003]
The micro-step drive can be realized by supplying a sinusoidal step current to the motor winding with a phase difference corresponding to the number of motor phases. FIG. 5 shows an example of the two-phase stepping motor. The output cos θ * of the first-phase basic current command generator 51 and the second-phase basic current command corresponding to the position command θ * applied to the external input terminal 10 are shown. An output sin θ * of the generator 52 is generated, the outputs of the phase basic current command generators 51 and 52 are connected to one input terminal of multipliers 63 and 64, and the current amplitude applied to the external input terminals 61 and 62 The command is connected to the other input terminals of the multipliers 63 and 64 to obtain a first phase current command Iα * cos θ * and a second phase current command Iβ * sin θ *. The adders 31 and 32, the current controllers 41 and 42, and the inverter 70 current detectors 81 and 82 include a first phase current command Iα * cos θ * and a second phase current command Iβ * sin θ applied to the adders 31 and 32, respectively. A current control system using * as a current command is configured to achieve desired characteristics.
The micro-step driving method according to FIG. 5 is an effective technique for reducing transient vibrations because the step-like operation can be miniaturized according to the resolution of the position command and can be approximated to smooth rotation. .
However, in the micro-step driving method, for example, the stop position error at the time of rest depends on the motor angle versus the generated torque characteristic, so that the stop position improvement effect cannot be expected. Similarly, the natural vibration of the motor indicates the natural characteristics of the stepping motor.
[0004]
In order to realize the micro-step function and the vibration reduction, for example, as described in JP-A-6-225595, there is a control device that converts each phase current into a dq rotating coordinate system and handles motor current control in a rotating coordinate system.
In the system described in JP-A-6-225595, an encoder is connected to a stepping motor, and current control, speed control, and position control are performed on the assumption that the stepping motor is the same model as the permanent magnet synchronous motor as shown in the configuration diagram of FIG. A specific method is described in which each closed loop control system is configured, and these are converted into a dq rotation coordinate system to realize position control. Further, for the purpose of simplifying the control configuration, it is specified that the non-interference element of the dq axis component is omitted and that the current command is directly given on the dq axis.
[0005]
However, the stepping motor has a feature that the number of magnetic poles is large and the basic current frequency ωre is higher than other control motors. For this reason, when the stepping motor is configured with the same control circuit as a permanent magnet type synchronous motor having the same structure, the current controller gain decreases as the speed increases due to the limit of the responsiveness of the current controller, and the motor current is controlled. There is a problem that errors increase. Further, since the motor generates the speed electromotive force Eemf, the state where the Eemf antagonizes the applied voltage or the motor current cannot be controlled at the number of rotations exceeding the applied voltage occurs due to an increase in the motor rotation speed.
In other words, in an actual device with a limited applied voltage as compared with the control method of the stepping motor described in Japanese Patent Application Laid-Open No. 6-225595, it becomes difficult to control the current as the rotation speed increases, and the controllable range is limited. There was a problem.
Further, a stepping motor control device described in Japanese Patent Application Laid-Open No. H6-225595 discloses a current perpendicular to a magnetic flux for controlling generated torque, that is, a q-axis. The configuration is such that the current is controlled in accordance with the speed deviation, and a position controller and a speed controller need to be provided in order to realize the position control. Therefore, the configuration has been a complicated and expensive control device.
[0006]
[Problems to be solved by the invention]
As described above, the position change amount per step of the stepping motor is subdivided in the conventional method for the purpose of suppressing the vibration, but the characteristic with respect to the vibration and the stop accuracy with respect to the load change is the characteristic characteristic of the stepping motor. Was. Further, in the conventional method in which the vibration characteristics are positively improved, the configuration is complicated and the control device is expensive.
An object of the present invention is to realize a driving device for a stepping motor which has a vibration suppressing effect, has a simple configuration and is inexpensive. It is another object of the present invention to realize a stepping motor driving device having an effect of improving the positional accuracy when stopping (zero speed).
[0007]
[Means to solve the problem]
In order to solve the above problem, according to the present invention, in a driving device for a polyphase stepping motor for supplying a sinusoidal step current to the stepping motor, a position detector for detecting a rotor magnetic pole position is provided, which is provided to a position command input terminal. Using the position command θ * and the rotor magnetic pole position θf detected by the position detector, a position deviation ε, which is the difference between the position command θ * and the rotor magnetic pole position θf, is calculated, and the position deviation ε is multiplied by a coefficient unit. After that, the value obtained by subtracting the output of the coefficient unit from the position command θ * is used as the excitation angle command.
Further, the coefficient k of the coefficient unit is adjusted to be 0 <k <1 for the purpose of suppressing vibration, and the coefficient k is changed within the range of k <0 for the purpose of stop accuracy control.
[0008]
[Action]
With the above configuration, a low-vibration, high-precision driving device, which is an object of the present invention, can be realized at low cost. The grounds are described below.
Assuming that the shaft torque of the motor is a sine function of the deviation between the rotor magnetic pole position and the excitation position, that is, the position δ, the shaft torque can be expressed by Equation 1.
(Equation 1)

Here, T is the shaft torque, Tm is the motor maximum torque, and δ is the position deviation. Further, the output λ of the vibration suppression unit when the vibration suppression unit 20 is configured as shown in FIG.
(Equation 2)

Here, k is a set value of the coefficient unit 21, θ * is a position command applied to the terminal 10, and θ / f is a rotor magnetic pole position which is an output of the position detector 92.
Since the output λ of the vibration suppressing unit 20 is the angle of the current command, the phase difference between the rotor magnetic pole positions θf and λ can be considered as the deviation δ, and therefore, Equation 3 holds.
[Equation 3]

Equation 3 is substituted into Equation 1 to obtain Equation 4.
(Equation 4)

FIG. 3 shows the relationship of Expression 4. 3A shows a case where k = 0, FIG. 3B shows a case where k> 0 (k = 0.5 as a representative value), and FIG. 3C shows a case where k <0 (k = −0 as a representative value). .5). FIG. 4 shows the relationship between k and the maximum torque generation angle. That is, as shown in FIG. 4, it can be seen that the angle of the maximum torque generation can be controlled by changing the magnitude of the set value k of the coefficient unit. In addition, as shown in FIG. 3, the ratio of the position deviation at the stable point to the generated torque (referred to as shaft rigidity) can also be changed.
Since it is clear that the condition of k = 0 in FIG. 3A corresponds to the normal open drive of the stepping motor, the shaft rigidity can be reduced by setting k to a positive value. As a result, vibration can be reduced.
Further, by setting k to a negative value, the shaft rigidity can be increased, so that the stop position accuracy can be improved.
[0009]
【Example】
FIG. 1 shows a first embodiment of the present invention.
In FIG. 1, a predetermined voltage is applied to a stepping motor 91 by a PWM inverter 70 to rotate the motor. The current detectors 81 and 82 detect the motor phase currents iαf and iβf, and use the motor phase currents iαf and iβf as one input of the first adder 31 and the second adder 32. On the other hand, iα * and iβ * are applied to the first phase current amplitude command input terminal 61 and the second phase current amplitude command input terminal, respectively.
The adders 31 and 32 calculate a current error which is a difference between the current command and the feedback current. The current errors are amplified by the current compensators 41 and 42 and then input to the PWM inverter 70.
[0010]
FIG. 2 is a diagram showing details of the adjustment unit 20.
The angle calculator 21 multiplies the position deviation ε output from the comparison 22 by a factor (k times), and connects it to one input of an adder 23 (subtraction is performed because of a different sign). A position command θ * is connected to the other input of the adder 23 to obtain an output λ.
[0011]
When the coefficient k is set to 0 <k <1, the output λ of the adjusting unit 20 has a smaller command change than when the angle command is directly used as the angle command of the exciting current when the rotor magnetic pole position has a deviation from the command. Can be provided transiently, so that a vibration reduction effect can be obtained.
[0012]
When the coefficient k is set to k <0, when the rotor magnetic pole position has a deviation with respect to the command, the output λ of the adjusting unit 20 changes a command change larger than the case where the angle command is used directly as the angle command of the excitation current. Can be given to the motor, so that the shaft rigidity of the motor can be increased.
[0013]
【The invention's effect】
FIG. 6 shows a second embodiment of the present invention.
6 and FIG. 1 have the same reference numerals, but in FIG. 6, the target motor is a three-phase stepping motor, and the three-phase / two-phase fixed coordinate converter 63 and the two-phase / three-phase fixed The configuration is the same except that a coordinate converter 64 and a current sensor 33 are added. When detecting a three-phase current, it is also possible to omit the third-phase current sensor by calculating the third-phase current using two current sensor detection outputs by utilizing the symmetry.
The functions shown in the first and second embodiments can be realized by using a microprocessor to reduce the number of components.
[0014]
[Brief description of the drawings]
FIG. 1 is a first embodiment of the present invention.
FIG. 2 is a partial explanatory view of the first embodiment of the present invention.
FIG. 3 is an explanatory diagram showing a relationship between an angle and an axial torque for explaining the principle of the present invention.
FIG. 4 is an explanatory diagram illustrating a relationship between a coefficient factor coefficient and a maximum torque generation angle according to the present invention.
FIG. 5 is a block diagram of a first conventional example.
FIG. 6 is a block diagram of a second conventional example.
[0014]
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 Position command input terminal 20 Adjuster 21 Coefficient unit 22, 23 Adder 31, 32 Adder 41 First phase current controller 42 Second phase current controller 51 First phase basic current command generator 52 Second phase basic current Command generator 61 First phase current amplitude command input terminal 62 Second phase current amplitude command input terminal 70 PWM inverters 81, 82 Current detector 91 Stepping motor 92 Position detector 101 Adder 102 Adder 103 Adder 104 Adder 105 Adder 110 position controller 120 speed controller 130 first coordinate converter 141 first current controller 142 second current controller 150 PWM inverter 154 first current detector 155 second current detector 160 2 coordinate converter 170 trigonometric function generator 180 stepping motor 190 position detector [reference number] L2003-05

Claims (4)

A stepping motor drive device for applying a sinusoidal step current to a stepping motor includes a current control function for controlling a motor current according to a current command, and a position detector for detecting a command rotor magnetic pole position, which is provided to a position command input terminal. A position deviation ε, which is a difference between the position command θ * and the rotor magnetic pole position θf, is calculated using the position command θ * and the rotor magnetic pole position θf detected by the position detector, and the position deviation ε is multiplied by a coefficient unit. And a stepping motor driving device configured to set a value obtained by subtracting the output of the coefficient unit from the position command θ * as an excitation angle command. 2. The stepping motor driving device according to claim 1, wherein k is a coefficient of the coefficient unit, and k is determined in a range of 0 ≦ k <1. 2. The stepping motor drive device according to claim 1, wherein the coefficient k of the coefficient unit is determined in a range of k ≦ 0. 2. The stepping motor driving device according to claim 1, wherein the coefficient k of the coefficient unit is set to 0 ≦ k <1 when the motor is rotating, and is determined within a range of k ≦ 0 when the motor is stopped.

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