JP2009213244A - Stepping motor drive controller and control method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To efficiently drive a stepping motor, without having to use a complex excitation sequence, or the like, by changing the drive method of the stepping motor, and to attain stabilized drive by controlling transient phenomenon, when the drive method is changed. <P>SOLUTION: A stepping motor drive controller 1 controls a stepping motor 2, by changing the drive method between microstep drive and sensorless drive. The drive controller 1 estimates the load at the time of microstep drive by means of a load estimator 11, and controls the drive of the stepping motor 2, such that a current corresponding to the value of the load flows through the stepping motor 2, when the drive method is changed from microstep drive to sensorless drive by using a value of the load which is appropriate. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a stepping motor drive control device and a stepping motor drive control method, and more particularly to a stepping motor drive control device and a stepping motor drive control method for performing control by selectively switching a plurality of drive methods.

  Conventionally, constant current micro-step driving is generally known as a stepping motor driving method. However, this driving method has a problem that the efficiency is poor because the motor is driven by supplying a constant current regardless of the load. Therefore, in order to perform efficient control, it is considered to apply sensorless control. The sensorless control is a motor drive control method executed without using a sensor (position detection sensor, rotation speed sensor, etc.) that detects the rotor position and / or speed. The motor model of the stepping motor is the same as that of a general synchronous motor. Therefore, it is possible to apply sensorless control that has been proposed for general synchronous motors.

  As a method for driving a stepping motor using sensorless control, for example, Patent Document 1 can be cited. In the control method of Patent Document 1, open loop control is performed in the low speed region, and the back electromotive force generated in the stepping motor is calculated from the voltage and current from the driver in the high speed region, and the calculated back electromotive force is used. Thus, a closed loop control is used in which the positional relationship between the rotor and the stator is obtained and the position of the rotor is controlled using this positional relationship.

  In the drive control device disclosed in Patent Document 2, the rotation speed of the stepping motor is compared with a reference value, and when it is lower than the reference value, an open loop drive system is selected, and when it is higher than the reference value, a closed loop drive system is selected. Is configured to select.

The drive control device disclosed in Patent Document 3 is configured to turn on an open phase switching element for a short period of time immediately after the chopper is turned off, and to quickly charge and discharge the output capacitance of the switching element.
JP-A-9-322592 Japanese Patent Laid-Open No. 5-103500 Japanese Patent Laid-Open No. 10-42594

  However, the drive control of the stepping motor disclosed in Patent Documents 1 to 3 has the following problems. In the drive control devices disclosed in Patent Literature 1 and Patent Literature 2, when the motor is loaded, when switching between open loop control and closed loop control, a large transient phenomenon occurs at the time of switching. In the drive control disclosed in Patent Document 3, it is necessary to detect the back electromotive force using a complicated excitation sequence.

  In view of these problems of the prior art, the object of the present invention is to drive the stepping motor efficiently without using a complicated excitation sequence by switching the driving method of the stepping motor, and to switch the driving method. The purpose is to realize a stable drive by suppressing the transient phenomenon at the time.

  In order to achieve the above object, the present invention provides a stepping motor drive control device for controlling a stepping motor by switching between micro-step driving and sensorless driving, and a current detector for detecting an actual current flowing through the stepping motor; A sensorless control means for forming a sensorless drive command for determining a drive current to be passed through each phase of the stepping motor based on the position instruction and the detected actual current to execute the sensorless drive; A load estimator that estimates a load of the stepping motor at the time of step driving to obtain a first load estimated value, and the sensorless control means switches the estimated load when switching from microstep driving to sensorless driving. The sensorless drive for determining the drive current to meet It is configured to the decree formed using the first load estimate.

  The stepping motor drive control device further includes a speed indicator that forms a speed instruction based on the position instruction, and the sensorless control means includes a deviation between the speed instruction and an estimated speed estimated based on the actual current. When the sensorless drive command is generated using the torque component current instruction obtained by applying PI compensation to the sensor, and when the sensorless drive is switched, the PI compensation is calculated using the first load estimated value. An initial value of the integral element for setting may be set.

  In order to execute the micro-step drive, the sensor-less control unit includes a micro-step control unit that forms a micro-step drive command for determining a drive current to be passed through each phase of the stepping motor based on the position instruction. The control means estimates a load of the stepping motor at the time of the sensorless drive and calculates a second load estimated value, and the microstep control means performs the estimation when switching from the sensorless drive to the microstep drive. The micro-step drive command for determining the drive current corresponding to the load at the time of sensorless drive may be formed.

  Furthermore, an electrical angle indicator that forms an electrical angle indication based on the position indication is further provided, and the electrical angle indicator uses the second load estimated value when switching from sensorless driving to microstep driving. An electrical angle instruction may be formed, and the microstep control means may be configured to form the microstep drive command based on the electrical angle instruction.

  For example, the sensorless control means is configured to generate the sensorless drive command based on an estimated excitation current instruction that is set or calculated in advance, a torque current instruction, and an estimated electrical angle that is estimated based on the actual current. Form.

  As an example, the sensorless control means includes a speed / electrical angle estimator, and the speed / electrical angle estimator calculates the estimated speed and the estimated electrical angle from a difference between the actual current and an estimated current calculated from a motor model. Is calculated.

  As another example, the sensorless control means includes a current controller and an adaptive observer, and the current controller includes a dq axis current calculated from the actual current, the estimated excitation current instruction, and the torque current. A dq axis voltage instruction is formed from the instruction, and the adaptive observer calculates the estimated speed and the estimated electrical angle from the dq axis current and the dq axis voltage instruction.

  Further, it comprises a position error adjuster that compares the position indication with the estimated electrical angle and calculates a deviation between the two, and when the electrical angle indicator is switched from the sensorless drive to the microstep drive, A deviation may be added to the position instruction, and the electrical angle instruction may be formed from the position instruction obtained by adding the deviation and the second estimated load value.

  The present invention is also a stepping motor drive control method for controlling a stepping motor by switching between micro-step driving and sensorless driving, wherein a current detection step for detecting an actual current flowing through the stepping motor and the sensorless driving are executed. A sensorless control step for forming a sensorless driving command for determining a driving current to be passed through each phase of the stepping motor based on the position indication and the detected actual current; and the stepping at the time of the microstep driving. A first load estimating step for estimating a load of the motor to obtain a first load estimated value, and the sensorless control step corresponds to the estimated load when the microstep driving is switched to the sensorless driving. The sensor for determining the drive current; A drive command comprises forming with said first load estimate.

  The stepping motor drive control method includes a microstep control for forming a microstep drive command for determining a drive current to be passed through each phase of the stepping motor based on the position instruction in order to execute the microstep drive. And a second load estimating step of obtaining a second load estimated value by estimating a load of the stepping motor at the time of the sensorless driving, and the microstep control step is changed from the sensorless driving to the microstep driving. When the switching is performed, the micro-step drive command for determining the drive current corresponding to the estimated load at the time of the sensorless control may be formed.

  In the stepping motor drive control device and the stepping motor drive control method according to the present invention, the stepping motor is controlled by switching between microstep drive and sensorless drive. The micro-step drive generally has a property that it is not effective in all rotation speed regions but has a superiority in low speed regions. On the other hand, the sensorless drive generally has a property that it is superior in the middle and high speed regions than when the stepping motor is stopped and in the low speed region.

  In the present invention, since the stepping motor is controlled by switching between micro-step driving and sensorless driving without using a complicated excitation sequence or the like, microstep driving is executed at the time of stop and in the low speed region, and sensorless in the middle / high speed region. By executing the drive, it is possible to perform highly accurate and efficient control.

  Furthermore, the present invention provides a sensorless method for determining a motor drive current using a load estimation value obtained by estimating a load of a stepping motor at the time of microstep drive when switching from microstep drive to sensorless drive. A drive command is formed. Therefore, since the load estimated value at the time of microstep driving is reflected in the sensorless driving command immediately and immediately after switching from microstep driving to sensorless driving, a current corresponding to the load at the time of microstep driving flows to the stepping motor. . Therefore, it is possible to realize stable driving by suppressing transient phenomena such as speed fluctuations that occur when switching from microstep driving to sensorless driving.

Hereinafter, a first embodiment of the present invention will be described with reference to the accompanying drawings. FIG. 1 schematically shows a circuit diagram of a stepping motor drive control device according to the present embodiment. The stepping motor drive control device 1 executes rotor position control of the N-phase HB type stepping motor 2 based on a position instruction θ ^* given from the outside. In this position control, microstep driving and sensorless driving are selectively switched and executed. In the present embodiment, the stepping motor drive control device 1 is configured to perform micro-step driving when the stepping motor 2 is stopped and in a low speed region, and to perform sensorless driving in a middle / high speed region.

First, when stopping, the position is held by microstep driving, and when the position instruction θ ^* is input, the microstep driving is started. Thereafter, when the speed becomes medium to high, the driving method is switched to the sensorless driving by the driving method switching unit 3 that receives the position instruction θ ^* . When approaching the stop position, the stepping motor 2 decelerates, and when the speed becomes low, the drive method switcher 3 switches to microstep drive and stops at the stop position.

A speed threshold value that is a reference value for switching between microstep driving and sensorless driving is set in advance. The drive method switching unit 3 calculates a speed from the position instruction θ ^* , compares the calculated speed with a preset speed threshold value, and determines whether to perform microstep driving or sensorless driving. Thus, a switching signal is output, and microstep driving and sensorless driving are switched via the switch 4.

[When sensorless drive]
The sensorless driving in the steady state will be described below.
The speed indicator 5 calculates a speed instruction ω _s from the position instruction θ ^* and outputs it to the sensorless control unit 6. The sensorless control unit 6 calculates a sensorless drive command V _sN based on the speed instruction ω _s and the actual current i _N flowing in the stepping motor 2, and outputs it to the PWM inverter 7. The actual current i _N flowing through the stepping motor 2 is detected by the current detector 8. The sensorless driving command V _sN is a command value for determining a driving current to be passed through each phase of the stepping motor 2.

The sensorless control unit 6 in the present embodiment may be any means that performs sensorless control in the steady state to form the sensorless driving command _VsN , and is not limited to means for performing specific sensorless control.

An example of the sensorless control unit 6 will be briefly described below. The sensorless control unit 6 includes a speed controller having a PI controller (not shown). The speed controller calculates a difference between the speed instruction output from the speed indicator 5 and an estimated speed estimated based on the actual current i _N , performs PI control on the difference, and outputs a current component for torque. Form. The sensorless control unit 6 generates the sensorless driving command from the formed torque component current instruction, the pre-set or calculated estimated excitation component current instruction, and the estimated electrical angle estimated based on the actual current i _N. V _sN is calculated and output to the PWM inverter 7. The PWM inverter 7 amplifies the power of the sensorless driving command _VsN and drives the stepping motor 2 sensorlessly.

Incidentally, the sensorless control unit 6, while performing sensorless drive, and calculates the load estimated value T _s indicative of the value of the load during the sensorless drive. This load estimated value is used for drive control when switching from sensorless drive to microstep drive, as will be described later. The calculation of the estimated load value Ts will be described in detail later [when switching from sensorless drive to microstep drive].

[In micro step drive]
The microstep drive in the steady state will be described below. The electrical angle indicator 9 calculates an electrical angle instruction θ _m from the input position instruction θ ^* . The electrical angle instruction θ _m is a value that indicates the excitation electrical angle of the stepping motor 2. Micro step control unit 10, the calculated electrical angle instruction theta _m and the actual current i _N a micro step current instruction given from the outside of the stepping motor 2 detected by the current detector 8 (micro-step drive set current value) Based on the above, a micro-step driving command V _mN is formed and output. The microstep drive command V _mN is a command value for determining a drive current to be passed through each phase of the stepping motor 2. The calculated micro-step driving command V _mN is output to the PWM inverter 7, and the PWM inverter 7 amplifies the power of the micro-step driving command V _mN and drives the stepping motor 2 by micro-step driving.

The load estimator 11, while performing the micro step drive, and calculates the load estimated value T _m indicative of the value of the load during the micro step drive. This estimated load value _Tm is used for drive control when switching from microstep drive to sensorless drive, as will be described later. The calculation of the load estimated value T _m is described in detail in [when switching from the micro step drive to sensorless driving] after.

[When switching from microstep drive to sensorless drive]
The operation of the stepping motor drive control device 1 when switching from microstep drive to sensorless drive will be described below.
In the driving of the stepping motor, when there is no load, the switching operation with no speed fluctuation can be performed by switching by matching the electrical angle in both the microstep driving and the sensorless driving. However, when there is a load, speed fluctuation occurs as a transient phenomenon. In particular, when switching from microstep driving to sensorless driving, a large speed fluctuation occurs, and in some cases, control becomes impossible.

  Many sensorless controls use a speed controller with an integrator to control the current so that a current corresponding to the required torque flows. Since sensorless driving is not performed at the time of switching the drive method, the torque current instruction at the time of switching is determined by the initial value of the integrator in the speed controller. That is, when the initial value of the integrator is set to zero, the torque current instruction at the time of switching is zero. Therefore, in the case of a load, speed fluctuation occurs until a torque component current instruction corresponding to the load is formed.

FIG. 3 is an experimental result showing the relationship between time and speed when switching from microstep driving to sensorless driving when the stepping motor is loaded.
In FIG. 3, the microstep drive is switched to the sensorless drive at time 0. As is clear from FIG. 3, a large speed fluctuation occurs in the period exceeding 0.4 seconds immediately after switching from the micro step drive to the sensorless drive.

  Therefore, in the present invention, a steady state load at the time of microstep driving is estimated, and control is performed so that a current corresponding to the estimated load flows to the stepping motor when switching from microstep driving to sensorless driving. Therefore, the speed fluctuation at the time of switching from the micro step drive to the sensorless drive is suppressed.

  In this embodiment, when switching from micro-step driving to sensorless driving, the initial value of integration corresponding to the load during micro-step driving is set in the integrator of the speed controller, so that the current corresponding to the load is stepped. It is controlled to flow to the motor.

鎖交磁束数φ_ａはモータ定数、電流Ｉ_ａは相電流のピーク値であって、予め設定値として与えられている。励磁位置θは電気角指示θ_ｍに対応する指示値であるため既知である。したがって、磁束位置（回転子位置）θ_ｒｅを推定できれば、負荷Ｔ_ｍ（発生トルクＴ）を推定することが出来る。 As described above, the load estimation value T _m indicating the load value during microstep driving is calculated by the load estimator 11 during microstep driving.
FIG. 2 schematically shows a circuit diagram of the load estimator 11. Hereinafter, with reference to FIG. 2 illustrating a method of calculating the load T _m. Generated torque T of the stepping motor 2 can be determined from the flux linkage number phi _a and current I _a and the magnetic flux position (rotor position) theta _re and excitation position (energized electrical angle) theta by the following equation.

Flux linkage number phi _a motor constant, a peak value of the current I _a is the phase current, given as a preset value. The excitation position theta known for an instruction value corresponding to the electrical angle instruction theta _m. Therefore, if the magnetic flux position (rotor position) θ _re can be estimated, the load T _m (generated torque T) can be estimated.

The induced electromotive force estimation calculation device 20 provided in the load estimator 11 estimates the induced electromotive force e _N of each phase from the actual current i _N detected by the current detector 8 and the microstep drive command V _mN . An N-phase to two-phase conversion device 21 is connected to the induced electromotive voltage estimation calculation device 20. N-two phase converter 21, the induced electromotive voltage eα converts the estimated phases of the induced electromotive force e _N 2-phase AC, seek Ibeta.

The load estimator 11 further includes a sin function generator 22 and a cos function generator 23. sin function generator 22 calculates the sin [theta ^est _re previously determined or estimated to rotor position estimated electrical angle theta ^est _re had as input. The multiplier 24 multiplies the calculated sin θ ^est _re and the estimated one-phase portion eβ of the two-phase AC induced electromotive voltage as inputs.

Similarly, cos function generator 23 calculates a cos [theta] ^est _re previously determined or estimated to rotor position estimated electrical angle theta ^est _re had as input. The multiplier 26 multiplies the calculated cos θ ^est _re and the estimated two-phase AC induced electromotive voltage eα for one phase as inputs. The values of eβ × sinθ ^est _re and eα × cosθ ^est _re obtained here are input to the subtracter 25 obtains a _{^{eα × cosθ est re -eβ × sinθ}} est re is the difference.

The obtained eα × cos θ ^est _re −eβ × sin θ ^est _re is input to the first amplifier 27 and amplified. The output amplified by the first amplifier 27 is input to the first integrator 28 and integrated. The output result integrated by the first integrator 28 is further input to the second integrator 29 for integration, and the output from the first integrator 28 is paralleled to the second integrator 29. The second amplifier 30 is connected to the second amplifier 30 for amplification. Then, the integration result from the second integrator 29 and the amplification result from the second amplifier 30 are input to the adder 31 to add the integration output and the amplification output.

The sin function is used so that the calculated output θ ^est _re from the adder 31 is the estimated position of the rotor of the stepping motor 2 and the calculated output is replaced with the rotor position that has been obtained or estimated in advance. It feeds back to the generator 22 and the cos function generator 23 and repeats the calculation.

By repeating this operation, the calculated output from the adder 31 is used as the estimated rotor position θ ^est _re of the stepping motor 2. The estimated load value calculator 32 receives the estimated rotor position θ ^est _re and the electrical angle instruction (excitation electrical angle) θ _m output from the electrical angle indicator 9 as inputs, and the estimated load value T during microstep driving. _m is calculated.

Next, the operation of the load estimator 11 described above will be described in more detail using mathematical expressions.
If the applied voltage of each phase is V, the current is I, the induced electromotive voltage is E, and the impedance is Z, the current-voltage equation of the N-phase stepping motor is as follows.

ここで、Ｖ、Ｉ、ＥはＮ列の行列、ＺはＮ行Ｎ列の行列である。
電圧Ｖにはマイクロステップ駆動指令Ｖ_ｍＮを、電流Ｉには電流検出器８で検出した実電流ｉ_Ｎを、Ｎ相ステッピングモータのインピーダンスＺにはあらかじめ測定しておいた値（各相のインダクタンス値と抵抗値）を用いれば、誘起起電圧Ｅは次式から求められる。

Here, V, I, and E are N-column matrices, and Z is an N-row N-column matrix.
The micro step drive command V _mN to the voltage V, and the actual current i _N detected by the current detector 8 to the current I, the value measured in advance in the impedance Z of the N-phase stepping motor (phases of inductance Value and resistance value), the induced electromotive force E can be obtained from the following equation.

この計算を行う部分を誘起起電圧推定演算装置２０とする。求めた誘起起電圧の推定値を２相交流に変換する。例えば、３相交流を２相交流に変換する変換行列ｃは次式となる。

The part that performs this calculation is referred to as an induced electromotive force estimation calculation device 20. The obtained estimated value of the induced electromotive voltage is converted into a two-phase alternating current. For example, a conversion matrix c that converts a three-phase alternating current into a two-phase alternating current is as follows.

対象となるモータが３相であった場合は上式を用いる。相数により変換行列を変更する。Ｎ相２相変換装置２１は、誘起起電圧推定演算装置２０で求めたＮ相の誘起起電圧推定結果を変換行列で２相交流に変換し、２相交流の誘起起電圧の瞬時値を算出する。

When the target motor has three phases, the above equation is used. Change the transformation matrix according to the number of phases. The N-phase to two-phase converter 21 converts the N-phase induced electromotive force estimation result obtained by the induced electromotive force estimation arithmetic unit 20 into a two-phase alternating current using a conversion matrix, and calculates an instantaneous value of the induced electromotive voltage of the two-phase alternating current. To do.

Next, a method for obtaining position information from the estimated induced voltage information will be described.
The α and β phase armature winding interlinkage magnetic flux numbers ψ _fα and ψ _fβ for inducing the induced voltages eα and eβ are expressed by the following equations, where the maximum value is ψ _f ′.

このときの各相の誘起電圧ｅα、ｅβは次式となる。

Here, θ _re is a field angle (electrical angle) taken clockwise with respect to the α-phase armature winding, and is represented by the following equation where _ωre is an electrical angular velocity.

The induced voltages eα and eβ of each phase at this time are as follows.

この計算を行う部分は、ｓｉｎ関数発生器２２、ｃｏｓ関数発生器２３及び乗算器２４，２６である。 A sine (sin) value and a cosine (cos) value of the estimated position calculation result θ ^est _re of the rotor of the stepping motor 2 are obtained, and the respective values are multiplied by the induced voltages eα and eβ to obtain the following equation.

The parts that perform this calculation are a sin function generator 22, a cos function generator 23, and multipliers 24 and 26.

ここで、θ^ｅｓｔ _ｒｅ≒θ_ｒｅであれば、次式の関係が成り立つ。

When the equation (11) is subtracted from the equation (10), the following equation is obtained.

Here, if θ ^est _re ≈ θ _re , the following relationship is established.

前記（１４）式は、推定結果θ^ｅｓｔ _ｒｅと実測値θ_ｒｅの偏差に比例した値となることが分かる。この計算を行う部分が減算器２５である。 Substituting the equation (13) into the equation (12) yields the following equation.

It can be seen that the equation (14) is a value proportional to the deviation between the estimation result θ ^est _re and the actual measurement value θ _re . The part that performs this calculation is a subtractor 25.

前記（１５）式は、ステッピングモータ２の回転子の推定位置θ^ｅｓｔ _ｒｅと実位置θ_ｒｅとは、時間∽（無限大）で一致するトラッキングフィルタとなっていることを示している。 That is, the output result from the subtractor 25 in FIG. 2 is the calculation of θ _re −θ ^est _re . Therefore, the amplification factor of the first amplifier 27 is A1, the amplification factor of the second amplifier 30 is A2, the transfer functions of the first and second integrators 27 and 28 are 1 / s, and the induction in FIG. When the transfer function after the voltage estimation calculation device 20 is obtained, the following equation is obtained.

The equation (15) indicates that the estimated position θ ^est _re and the actual position θ _re of the rotor of the stepping motor 2 are tracking filters that coincide with each other at time ∽ (infinite).

  Further, in order to obtain the estimated position of the rotor by a response of a desired damping factor or natural frequency, the amplification factor A1 of the first amplifier 27 and the amplification factor A2 of the second amplifier 30 are set as follows. Can be set.

Load estimated value calculating section 32 with (not illustrated) the subtractor, the estimated rotor position (electrical angle) theta ^est _re output electrical angle instruction from the electrical angle indicator 9 (excitation electrical angle) between theta _m Calculate the difference. Here, the obtained rotor estimated position θ ^est _re is an estimation result of the electrical angle of the induced voltage taken clockwise with respect to the α-phase armature winding. Therefore, the field position is an angle advanced by 90 °. Therefore, π / 2 is added to the difference calculated by the subtracter by an adder (not shown) to estimate the load angle θ− _θre .

The estimated load value calculator 32 calculates the estimated load value T _m from the estimated load angle θ−θ _re , the preset peak current value i _a of the phase current and the motor constant φ _a using the equation (1). calculate. As described above, the load estimator 11 calculates the load estimated value T _m using the rotor position estimated by the tracking filter represented by the equation (15). Since the tracking filter has a filter function for cutting high-frequency components, when the load estimator 11 calculates the load estimated value _Tm , it is possible to remove fluctuations in the load estimated value due to detection noise.

When switched from the micro step drive for the sensorless control, sensorless control unit acquires the estimated load estimated value calculating section 32 load estimated value T _m, load the initial value of the integrator provided in the speed controller set to a value appropriate to estimate T _m. Here, load estimated value The T _m is the load estimated value T _m calculated immediately before is switched from the micro step drive to sensorless driving. The initial integral value is determined by dividing the estimated load value _Tm by a torque constant, converting it to a current, and further dividing by a control gain.

  In this way, by setting the initial value of the integrator of the speed controller to a value commensurate with the load value at the time of microstep driving, the load at the time of microstep driving immediately after and immediately after switching from microstep driving to sensorless driving. Is controlled so that a current commensurate with the current flows in the stepping motor, and speed fluctuations when switching from microstep driving to sensorless driving can be suppressed.

FIG. 4 shows experimental results showing the relationship between time and speed when the stepping motor drive control device 1 is switched from microstep drive to sensorless drive.
As is apparent from FIG. 4, in this embodiment, the transient phenomenon when switching from the microstep drive to the sensorless drive is suppressed, and the speed fluctuation at the time of switching hardly occurs.

[When switching from sensorless drive to microstep drive]
At the time of switching from the sensorless drive to the microstep drive, the electrical angle indicator 9 obtains the load estimated value T _s indicating the load value of the motor 2 at the time of the sensorless drive from the sensorless control unit 6, and the estimated load Based on the value T _s and the input position instruction θ ^* , an electrical angle instruction θ _m is formed so that a current corresponding to the estimated load value T _s flows through the stepping motor 2.

In sensorless control, the position of the magnetic flux is generally estimated using an observer or a motor inverse model, and the magnitude of the torque component current is controlled based on the estimated magnetic flux position. Therefore, the sensorless control unit 6 calculates the load estimated value T _s from the torque constant and the torque current.

When switching from the sensorless drive to the micro step drive, load estimate electrical angle indicator 9 obtains T _s, the load estimated value T _s to just before is switched from the sensorless drive to the micro step drive calculated by the sensorless control unit 6 It is.

As described above, when switched from the sensorless drive to the micro step drive, the current commensurate with the estimated load value T _s flows through the stepping motor 2, to suppress the velocity fluctuation at the time of switching to the micro step drive from the sensorless drive Can do.

As described above, in the present embodiment, efficient position control is realized by selectively switching between microstep driving and sensorless driving, and switching is performed when switching between microstep driving and sensorless driving. Since the current corresponding to the value of the previous load is controlled to flow to the stepping motor 2, the speed fluctuation at the time of switching is suppressed and stable control is realized.
Furthermore, since the above-described method is executed as the load estimation method in the load estimator 11, no detection winding or the like is used for the motor, so that no special motor is required. In addition, since no detection winding or the like is used, a special detection circuit is not required, and the calculation can be performed by the CPU.

[Second Embodiment]
FIG. 5 shows a second embodiment. As in the first embodiment, the stepping motor drive control device 40 performs microstep driving when the N-phase HB type stepping motor 39 is stopped and in the low speed region, and performs sensorless driving in the middle and high speed regions. It is configured. The switching of the driving method is executed by the driving method switching unit 42 as in the first embodiment. By switching the switches 43 and 44 according to the switching signal output from the driving method switching device 42, the driving method is switched. In FIG. 5, the switches 43 and 44 have selected micro-step driving.

  The subtractor 46, the speed controller 47, the current controller 48, the motor model 49, the speed / electrical angle estimator 50, and the coordinate converter 51 connected to the speed indicator 45 are the sensorless control unit 6 in the first embodiment. Corresponding to A coordinate converter 53, a subtractor 54, and a current controller 55 connected to the electrical angle indicator 52 correspond to the microstep control unit 10 in the first embodiment. The load estimator 56 performs the same processing as that of the load estimator 11 in the first embodiment.

In sensorless driving in the steady state, the speed instruction ω _s output from the speed indicator 45 that receives the position instruction θ ^* and the estimated speed estimated based on the actual current i _N detected by the current detector 41 Is input to the subtractor 46, and the difference between the speed instruction ω _s and the estimated speed is input to the speed controller 47. The speed controller 47 includes a PI controller, performs PI control on the input difference, and outputs it to the current controller 48 as a torque component current instruction.

The current controller 48 outputs a dq axis voltage instruction V _dqs to the coordinate converter 58 via the switch 43 from the estimated excitation current instruction and the torque current instruction that are set or calculated in advance. The coordinate converter 58 is further estimated electrical angle calculated based on the actual current i _N detected by the current detector 41 is inputted through the switch 44.

The coordinate converter 58 performs dq-3 phase conversion with the dq axis voltage instruction V _dqs and the estimated electrical angle as inputs, and outputs a sensorless drive command V _sN to the PWM inverter 59. The PWM inverter 59 amplifies the power of the sensorless drive command V _sN and drives the stepping motor 2 sensorlessly.

  The estimated speed and the estimated electrical angle are calculated by a speed / electrical angle estimator 50. The speed / electrical angle estimator 50 receives the model current acquired from the motor model 49 and the actual current that has undergone axis conversion via the coordinate converter 51. The motor model 49 is a mathematical model of the motor, and estimates the current value from the voltage speed. The coordinate converter 51 receives the phase current detected by the current detector 41 and the estimated electrical angle that is fed back, performs a three-phase-dq conversion, calculates the excitation current and the torque current, and calculates the speed / electricity. This is output to the angle estimator 50.

  The speed / electrical angle estimator 50 calculates the speed and the electrical angle from the difference (error) between the model current and the actual current (the excitation current and the torque current that have been subjected to the three-phase-dq conversion). The estimated electrical angle is output.

In the micro step drive in the steady state, the electrical angle indicator 52 receives the position instruction θ ^* and outputs an electrical angle instruction (excitation electrical angle) θ _m . The coordinate converter 53 receives the electrical angle instruction θ _m and the actual current i _N detected by the current detector 41 as input, performs a three-phase-dq conversion, calculates a DC current, and sends the DC current to the subtractor 54. Output. The subtractor 54 calculates a difference between the input microstep current instruction and the direct current and outputs the difference to the current controller 55. Current controller 55 performs PI control on the input value and outputs dq axis voltage instruction V _dqm .

The output dq axis voltage instruction V _dqm is output to the coordinate converter 58 via the switch 43. Further, the electrical angle instruction θ _m output from the electrical angle indicator 52 is input to the coordinate converter 58 via the switch 44. The coordinate converter 58 receives the dq axis voltage instruction V _dqm and the electrical angle instruction θ _m as input, performs dq-3 phase conversion, and inputs a microstep drive command V _mN to the PWM inverter 59. The PWM inverter 59 amplifies the power of the microstep drive command V _mN and drives the stepping motor 39 by microstep.

When switching from micro-step driving to sensorless driving, an integral initial value corresponding to the estimated load value T _m estimated by the load estimator 56 is set in the integrator of the speed controller 47 as in the first embodiment. . Accordingly, it is possible to suppress speed fluctuations when switching from microstep driving to sensorless driving. In this embodiment, since the dq axis voltage instruction V _dqs is calculated using the motor inverse model, it is not necessary to provide a PI controller in the current controller 48. Therefore, there is no need to set an integral initial value in the current controller 48 when switching from microstep driving to sensorless driving.

When the sensorless drive is switched to the microstep drive, the estimated load value T _s indicating the load value during the sensorless drive is output from the speed controller 47 to the electrical angle indicator 52. The speed controller 47 calculates a load estimated value T _s by multiplying a torque component current calculated based on the difference between the speed instruction ω _s and the estimated speed by a motor constant given in advance.

The electrical angle indicator 52 further receives a position instruction θ ^* . This position instruction θ ^* is also input to the position error adjuster 57 when switching to the microstep drive. Hereinafter, the position error adjuster 57 will be described. The estimated electrical angle estimated by the speed / electrical angle estimator 50 is input to the position error adjuster 57. The position error adjuster 57 receives the estimated electrical angle and the position instruction θ ^* as input, calculates a deviation between the two, and outputs the deviation to the electrical angle indicator 52. The electrical angle indicator 52 adds the input deviation to the position instruction θ ^* . The electrical angle indicator 52 uses the electrical angle instruction (excitation electrical angle) θ so that the current corresponding to the load during sensorless driving flows to the motor 39 from the position indication θ ^* obtained by adding the deviation and the load estimated value T _{s. m} is formed and output to the coordinate converter 53.

The position error adjuster 57 has an object of eliminating a calculation error that occurs when switching between sensorless driving as a speed control system and microstep driving as a position control system. That is, in sensorless driving, position and speed conversion is performed, for example, the speed instruction ω _s is calculated from the position instruction θ ^* via the speed indicator 45. Therefore, there is a possibility that the speed instruction and the position instruction cannot be matched due to the calculation error generated during the conversion process.

Therefore, the position error adjuster 57 calculates a deviation between the input estimated electrical angle and the input position instruction θ ^* and outputs the deviation to the electrical angle indicator 52 in order to match the speed instruction and the position instruction. is doing. Then, the electrical angle indicator 52 forms an electrical angle instruction theta _m by adding the deviation to the position indicator theta ^*. Accordingly, when switching the micro step drive, a calculation error or the like so that the resolved electrical angle instruction theta _m is output.

[Third Embodiment]
FIG. 6 shows a third embodiment. In a stepping motor drive control device 60 that drives and controls an N-phase HB motor 61, a subtractor 63, a speed controller 64, a current controller 65, an adaptive observer 66, an integrator 67, and coordinate conversion connected to a speed indicator 62 The device 68 corresponds to the sensorless control unit 6 in the first embodiment. A coordinate converter 70 connected to the electrical angle indicator 69 and a current controller 71 including a subtracter (not shown) correspond to the microstep control unit 10 in the first embodiment. The load estimator 72 executes the same processing as that of the load estimator 11 in the first embodiment. The switching of the driving method and the steady-state microstep driving by the driving method switching unit 73 are the same as those in the second embodiment, and thus the description thereof is omitted. In FIG. 6, the switches 74 and 75 are selected to perform microstep driving.

In the sensorless driving in the steady state, the speed indicator 62 calculates the speed instruction ω _s with the position instruction θ ^* as an input, and inputs it to the subtracter 63. The subtractor 63 calculates a difference between the speed instruction ω _s output from the speed indicator 62 and the estimated speed estimated based on the actual current detected by the current detector 76 and outputs the difference to the speed controller 64. The speed controller 64 includes a PI controller, performs PI control on the inputted difference to form a torque current instruction, and outputs the torque current instruction to the current controller 65.

The current controller 65 includes a PI controller, and an excitation current and torque calculated from an estimated excitation current instruction and a torque current instruction that are set or calculated in advance and an actual current detected by the current detector 76. The PI control is executed by calculating the difference from the _divided current, and the dq axis voltage instruction V _dqs is formed and output. The dq axis voltage instruction V _dqs is input to the coordinate converter 77 via the switch 74. Further, an estimated electrical angle estimated based on the actual current detected by the current detector 76 is input to the coordinate converter 77 via the switch 75.

The coordinate converter 77 receives the dq axis voltage instruction V _dqs and the estimated electrical angle as input, performs dq-3 phase conversion, and inputs a sensorless driving command V _sN to the PWM inverter 78. The PWM inverter 78 amplifies the power of the sensorless drive command V _sN and drives the stepping motor 61 sensorlessly.

  The estimated speed and the estimated electrical angle are calculated by the adaptive observer 66. The actual current detected by the current detector 76 is input to the adaptive observer 66 via the coordinate converter 68. The coordinate converter 68 performs a three-phase-dq conversion from the estimated electrical angle fed back and the input actual current (phase current) to calculate an excitation current and a torque current (dq axis current). To the adaptive observer 66.

The adaptive observer 66 calculates an estimated speed from the input actual current (dq axis current) and the voltage of the dq axis voltage instruction V _dqs output from the current controller 65, and uses the estimated speed via the integrator 67. The estimated electrical angle is calculated by integrating.
If the adaptive observer 66 is used as the sensorless control means as in the present embodiment, the gain setting of each control part is facilitated.

When switching from the micro step drive in the sensorless drive, as in the second embodiment, setting the integration initial value commensurate with the load estimated value T _m calculated by the load estimator 72 to the integrator of the speed controller 64. In addition, in the present embodiment, since the PI control is also executed in the current controller 65, the integral initial value corresponding to the load estimated value T _m calculated by the load estimator 72 also in the integrator of the current controller 65. Set.

When switching from the sensorless drive the micro step drive inputs said as in the second embodiment, the load estimated value T _s during sensorless drive output from the speed controller 64 to the electrical angle indicator 69. The position error adjuster 79 receives the position instruction θ ^* and the estimated electrical angle estimated by the adaptive observer 66 and outputs the deviation between them to the electrical angle indicator 69. The electrical angle indicator 69 uses an electrical angle instruction (excited electrical angle) so that a current corresponding to the load at the time of sensorless driving flows to the stepping motor 61 from the position instruction θ ^* obtained by adding the deviation and the load estimated value T _s. ) Θ _m is formed.

[Other Embodiments]
As mentioned above, although embodiment of this invention was described, this invention is not limited to above-mentioned embodiment, Various deformation | transformation and change are possible based on the technical idea of this invention.
For example, sensorless control and microstep control during steady state in the above embodiment are not limited to the above embodiment. Various sensorless control and microstep control performed by other components and controls can be applied to the present invention.
In the load estimator in the first embodiment, the estimated rotor position is calculated using a tracking filter, but the present invention is not limited to this. For example, the rotor estimated position θ ^est _re can be calculated using an arctangent. In this case, induced electromotive voltages eα and eβ obtained by converting into two-phase alternating current by the N-phase to two-phase converter 21 are input to an arc tangent function, and an output from the arc tangent function is input to a filter, it may be configured to output the output from the filter to the load estimated value calculating section 32 as the rotor position estimate theta ^est _re.
In the above-described embodiment, the N-phase HB type stepping motor is employed as the motor to be driven. However, the present invention is not limited to this, and another type of stepping motor may be the driving object.

In the second and third embodiments, the position error adjuster operates when switching from sensorless driving to microstep driving. However, the position error adjusters 57 and 79 can also operate during sensorless driving to adjust the position error. In this case, the position error adjusters 57 and 79 calculate a deviation between the position instruction θ ^* and the estimated electrical angle during the sensorless drive and output the deviation to the speed indicators 45 and 62. Speed indicator 45,62 is by calculating the speed instruction from the position indicator theta ^* obtained by adding the deviation by adding the deviation to the position indicator theta ^*, and outputs a speed instruction operation error or the like is corrected. As described above, when the speed instruction output from the speed indicators 45 and 62 during the sensorless driving is already adjusted via the position error adjusters 57 and 79, the estimated electric power is changed when switching to the microstep driving. It is not necessary to correct an error with respect to the corner position instruction θ ^* . Therefore, in the second and third embodiments, when the speed instruction is adjusted via the position error adjusters 57 and 79 during sensorless driving, the position error adjusters 57 and 79 There is no need to output to the angle indicators 52 and 69.

In the second and third embodiments, the load estimated value T _s during sensorless control is calculated based on the torque current in the speed controller 47,64, not limited to this. For example, the load estimated value T _s at the time of sensorless control is calculated by multiplying the torque component current output from the coordinate converters 51 and 68 by a motor constant via an arbitrary calculation means, and the calculated load estimated value T _You may comprise so that s may be input into the electrical angle indicator 52,69.

1 is a schematic circuit diagram of a stepping motor drive control device according to a first embodiment. It is a typical circuit diagram of a load estimator according to the first embodiment. It is a graph which shows the speed fluctuation | variation when switching microstep drive and sensorless drive. It is a graph which shows the speed fluctuation | variation when a microstep drive and a sensorless drive are switched by the stepping motor drive control apparatus which concerns on 1st Embodiment. It is a typical circuit diagram of a stepping motor drive control device according to a second embodiment. FIG. 10 is a schematic circuit diagram of a stepping motor drive control device according to a third embodiment.

Explanation of symbols

1, 40, 60 Stepping motor drive control device 2, 39, 61 Stepping motor 3, 42, 73 Drive method switching device 5, 45, 62 Speed indicator 6 Sensorless control unit 8, 41, 76 Current detector 9, 52, 69 Electrical angle indicator 10 Microstep controller 11, 56, 72 Load estimator 47, 64 Speed controller 48, 65 Current controller 49 Motor model 50 Speed / electrical angle estimator 57, 79 Position error adjuster 66 Adaptive observer

Claims (10)

A stepping motor drive control device for controlling a stepping motor by switching between micro-step driving and sensorless driving,
A current detector for detecting an actual current flowing through the stepping motor;
Sensorless control means for forming a sensorless drive command for determining a drive current to be passed through each phase of the stepping motor based on the position instruction and the detected actual current to execute the sensorless drive;
A load estimator that estimates a load of the stepping motor at the time of the microstep drive and obtains a first load estimated value;
The sensorless control means uses the first load estimated value to form the sensorless drive command for determining the drive current corresponding to the estimated load when the microstep drive is switched to the sensorless drive. A stepping motor drive control device configured as described above. A speed indicator that forms a speed indication based on the position indication;
The sensorless control means forms the sensorless drive command using a torque current instruction obtained by performing PI compensation on a deviation between the speed instruction and an estimated speed estimated based on the actual current. In addition, when switching to the sensorless drive, the initial value of the integral element for the PI compensation is set using the first load estimated value. The stepping motor drive control device described. In order to execute the microstep drive, microstep control means for forming a microstep drive command for determining a drive current to be passed through each phase of the stepping motor based on the position instruction,
The sensorless control means calculates a second load estimated value by estimating a load of the stepping motor during the sensorless driving,
The microstep control means is configured to form the microstep drive command for determining the drive current commensurate with the estimated load during the sensorless drive when the sensorless drive is switched to the microstep drive. The stepping motor drive control device according to claim 1 or 2. An electrical angle indicator that forms an electrical angle indication based on the position indication;
The electrical angle indicator forms an electrical angle indication using the second load estimated value when switching from sensorless drive to microstep drive,
The stepping motor drive control device according to claim 3, wherein the microstep control means forms the microstep drive command based on the electrical angle instruction.   The sensorless control means forms the sensorless drive command based on an estimated excitation current instruction, preset or calculated, a torque current instruction, and an estimated electrical angle estimated based on the actual current. The stepping motor drive control device according to any one of claims 2 to 4, wherein The sensorless control means includes a speed / electrical angle estimator,
6. The stepping motor drive according to claim 5, wherein the speed / electrical angle estimator calculates the estimated speed and the estimated electrical angle from a difference between the actual current and an estimated current calculated from a motor model. Control device. The sensorless control means includes a current controller and an adaptive observer.
The current controller forms a dq-axis voltage instruction from the dq-axis current calculated from the actual current, the estimated excitation current instruction, and the torque current instruction.
6. The stepping motor drive control device according to claim 5, wherein the adaptive observer calculates the estimated speed and the estimated electrical angle from the dq-axis current and the dq-axis voltage instruction. A position error adjuster that compares the position indication with the estimated electrical angle and calculates a deviation between the two;
The electrical angle indicator adds the deviation to the position instruction when the sensorless driving is switched to the microstep driving, and the electric power is calculated from the position instruction obtained by adding the deviation and the second load estimated value. The stepping motor drive control device according to claim 5, wherein the stepping motor drive control device is dependent on claim 4. A stepping motor drive control method for controlling a stepping motor by switching between micro-step drive and sensorless drive,
A current detection step of detecting an actual current flowing through the stepping motor;
A sensorless control step for forming a sensorless drive command for determining a drive current to be passed through each phase of the stepping motor based on the position instruction and the detected actual current in order to execute the sensorless drive;
A first load estimating step of estimating a load of the stepping motor during the microstep driving to obtain a first load estimated value;
The sensorless control step is a step of forming the sensorless drive command for determining the drive current corresponding to the estimated load using the first load estimated value when switching from microstep drive to sensorless drive. A stepping motor drive control method. A micro-step control step for forming a micro-step drive command for determining a drive current to be supplied to each phase of the stepping motor based on the position instruction in order to execute the micro-step drive;
A second load estimating step of estimating a load of the stepping motor during the sensorless driving to obtain a second load estimated value;
The microstep control step is configured to form the microstep drive command for determining the drive current commensurate with the estimated load during the sensorless control when the sensorless drive is switched to the microstep drive. The stepping motor drive control method according to claim 9.

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