JPH11252994A - Device and method for control of stepping motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To stably control the operations of a stepping motor by further improving the load fluctuation characteristic. SOLUTION: A controller is provided with a stepping motor 7, a drive circuit 4, an encoder 8 which outputs a detect signal upon detecting an output rotational angle, a target command section 9 which outputs a command signal, a position comparison control section 1 which compares the command signal with the detect signal of the encoder 8, a selection control section 2 which decides a driving lead angle and a drive current based on the compared results of the control section 1 and outputs the angle and current, and an observer circuit 5 which outputs a lead angle correcting value and a current correction value for respectively correcting the drive lead angle, and driving the current outputted from the control section 2 based on the simulated results of the operation characteristic of the used stepping motor 7, command signal, and detection signal. Since the operations of the motor 7 are monitored in detail, the motor 7 is able to by cope with abrupt load fluctuations, etc., and stable operation is realized.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control device and a control method for a stepping motor having windings of a plurality of phases.

[0002]

2. Description of the Related Art Regarding closed-loop control of a stepping motor, a document [Application of the Closed-Loop Stepping]
Moter] (IEEE Trans.On Automatic Control, TRFREDRI
KSEN, Vol. AC 13, No. 5 Oct. 1968) has been proposed. The features of this closed loop control will be briefly described with reference to FIG.

First, an encoder 102 for detecting a position represented by the rotation angle of a motor 101
And the same number of output channels. For example, 4
In the case of a phase motor, the encoder has four channels of output signals. Thus, when the motor 101 stops, the excited phase can be easily grasped. Second, the winding 1 of the phase in which the current should flow based on the output signal of the encoder 102
03a to 103d, and the rotation state of the motor 101,
That is, stop, acceleration, deceleration, steady rotation, and high speed rotation are controlled. Third, the rotation angle displacement up to the final target rotation angle to be positioned and the rotation state of the motor 101 when passing through the final target rotation angle are determined in advance, or the remaining time required during the angular displacement is determined. The motor 101 is controlled by previously determining the number of pulses and the excitation conditions at the time of passage.

[0004] Such a closed-loop control of the stepping motor particularly improves the high-speed performance. However, if the load fluctuates during the operation of the motor, a large vibration is generated when the motor is stopped, positioning is not completed, and positioning time increases. Has the disadvantage of doing so.

Therefore, Japanese Patent Publication No. 57-34758 has been devised as a prior art in which the above disadvantages are improved. FIG.
The features will be described briefly using FIG.

First, based on the closed loop control of FREDRIKSEN, a feedback circuit of a rotation angle loop, a rotation angular velocity loop, and a current loop is added thereto, an external command signal is given, and the motor 201 responds to a load change during operation. The load fluctuation characteristics are improved by controlling the winding current. Second,
When the load increases, the rotation angular velocity of the motor 201 decreases. In order to compensate for the decreased rotational angular velocity, the excitation circuit 202 works so as to increase the winding current, thereby producing an effect of preventing the rotational angular velocity from decreasing. Third, when the load is reduced, the operation is completely opposite to the above-described first and second features, thereby also preventing the fluctuation of the rotational angular velocity. Fourth, the load fluctuation characteristic is improved by controlling the increase and decrease of the electric energy to the motor 201 by the excitation circuit 202 in response to the load fluctuation of the motor 201, and the vibration at the time of stop is suppressed.

[0007]

[Problems to be solved by the invention] Japanese Patent Publication No. 57-3475
8, the external command signal is for finely instructing the time variation of the rotation angle of the stepping motor 201, so that when a larger load disturbance occurs, the motor 201 falls into a low-speed rotation state and further stops. Can lead to In this state, even if the load disturbance is removed after a certain amount of time has elapsed, the external command signal has already ended, and the motor 201 cannot reach the final target rotation angle. Furthermore, there is a possibility that a problem that the motor 201 falls into an uncontrollable state may occur. This is originally a stepping motor 2
01 is a problem with the feedback control, and its improvement is difficult except for the introduction of a new control method.

An object of the present invention is to provide a control device and a control method of a stepping motor capable of further improving load fluctuation characteristics and performing stable operation control.

[0009]

SUMMARY OF THE INVENTION The present invention provides a stepping motor, driving means for driving the stepping motor,
Detecting means for detecting an output rotation angle of the stepping motor and outputting a rotation angle signal; commanding means for storing a speed function from start to stop of the motor and outputting a target command signal based on the speed function; Comparing means for comparing the command signal and the rotation angle signal; control means for determining and outputting the drive advance angle and drive current of the stepping motor based on the comparison result; and simulating the operating characteristics of the stepping motor used. And an observer circuit that outputs a lead angle correction signal and a current correction signal for correcting the drive lead angle and the drive current output by the control means based on the target command signal and the rotation angle signal. This is a control device for a stepping motor.

According to the present invention, the output rotation angle of the stepping motor is detected, compared with the target rotation angle indicated by the target command signal, and driven based on the comparison result, so that the stepping motor is stabilized at the target rotation angle. Thus, the feedback control for rotating the rotation is realized. Furthermore, since the observer circuit uses the result of simulating the operating characteristics of the stepping motor, corrects the lead angle obtained by the feedback control based on the target command signal and the rotation angle signal, and corrects the current. The operation of the stepping motor is closely monitored, and it is possible to quickly respond to a sudden load change or the like, thereby realizing a stable operation.

Further, the present invention is characterized in that the observer circuit has a motor model for sequentially calculating a span worm equation describing operation characteristics of a stepping motor.

According to the present invention, the span warm equation ([Stepping Motored System Dynamics], Transactions
of ASME, JULY 1986, Vol.108 Dr.M.Kojima et.al.)
Can faithfully represent the operating characteristics of the stepping motor as an equation describing the stepping motor. The observer circuit is based on such an equation,
Since the sequential operation is performed and the stepping motor is controlled,
The operating characteristics can be accurately grasped, and more accurate control is possible.

Further, the present invention is characterized in that the observer circuit has a numerical solution table storing a result of previously calculating a span warm equation describing operation characteristics of a stepping motor.

According to the present invention, since a numerical solution table prepared by previously solving the above-described span worm equation is used for controlling the stepping motor, high-speed control is possible, and furthermore, it is possible to cope with a sudden load change. Thus, the stepping motor can be operated stably.

Further, the present invention further comprises current detecting means for detecting a driving current of the stepping motor and outputting a current signal, wherein the observer circuit controls the current based on a current signal, a target command signal and a rotation angle signal. The driving means outputs a lead angle correction signal and a current correction signal for correcting the driving lead angle and the driving current output by the means, respectively.

According to the present invention, the observer circuit obtains the lead angle correction signal and the current correction signal based on the detected current in addition to the target command signal and the rotation angle signal. Therefore, the operating characteristics can be accurately grasped, the lead angle and the current can be accurately corrected, and a more stable operation can be realized.

According to the present invention, a step of detecting the output rotation angle of the stepping motor to obtain a rotation angle signal, and comparing the target command signal with the rotation angle signal to determine a drive advance angle and a drive current of the stepping motor. Calculating a lead angle correction signal and a current correction signal based on a target command signal and a rotation angle signal by simulating operation characteristics of a stepping motor to be used; and calculating the calculated lead angle correction signal and current. Correcting the drive lead angle and the drive current based on a correction signal.

According to the present invention, feedback control for stably rotating the stepping motor at a desired target rotation angle is realized, and an observer circuit storing operation characteristics of the stepping motor is provided with a target command signal and a rotation control signal. Based on the angle signal, the lead angle obtained by the feedback control is corrected, and the current is corrected, so that the operation of the stepping motor is closely monitored. It is possible to realize.

[0019]

(First Embodiment) FIG. 1 is a block diagram showing an electrical configuration of a first embodiment of the present invention.
The control device includes a control circuit 10, a drive circuit 4, an observer circuit 5, a current detection circuit 6, a stepping motor 7, an encoder 8, and a target command unit 9. The control circuit 10 further includes a position comparison control unit 1, a selection control circuit 2, and a current control circuit 3. The target command section 9 receives a start pulse as a start signal and outputs a command pulse c1 to the position comparison control section 1 and the observer circuit 5. The command pulse c1 is a signal indicating the target rotation angle or angular velocity of the stepping motor.

The position comparison control section 1 of the control circuit 10 receives the command pulse c1 from the target command section 9 and counts the number thereof, receives the detection pulse from the encoder 8 and counts the number thereof. And calculate the deviation. If the command pulse c1 and the encoder signal c6 are position or rotation angle signals, the deviation is calculated directly. If the command pulse c1 and the encoder signal c6 are speed or rotation angular velocity signals, the deviation of the integral value of each signal is calculated. Position deviation signal c indicating deviation of rotation angle
2 is output to the selection control circuit 2. Selection control circuit 2
Receives the position deviation signal c2 and selects a corresponding reference lead angle (lead angle) and reference current. The selection control circuit 2 corrects the reference advance angle based on the advance angle correction signal c7 from the observer circuit 5, and outputs the corrected advance angle signal c3 to the drive circuit 4 as excitation timing. The current control circuit 3 corrects the reference current based on the current correction signal c8 from the observer circuit 5, and outputs the corrected current signal c5 to the drive circuit 4.

The drive circuit 4 has an excitation timing according to the correction advance angle from the selection control circuit 2 and the current control circuit 3
And generates a pulse signal corresponding to the current value level according to the current signal c5 from the controller, and drives the stepping motor. The current detection circuit 6 detects a current for driving the stepping motor 7 and outputs a detection signal c9 to the observer circuit 5. The encoder 8 detects the rotation angle of the output shaft of the stepping motor 7 and outputs an encoder signal c6 to the position comparison control unit 1 and the observer circuit 5. Also,
Instead of the encoder 8, a tachometer may be used to detect the rotational angular velocity of the output shaft of the stepping motor, and integrate and output the detected angular velocity.

The observer circuit 5 receives the target rotation angle or angular velocity from the target command section 9, the current from the current detection circuit 6, and the output rotation angle from the encoder 8, and selectively controls the lead angle correction signal c 7. The current correction signal c8 is output to the current control circuit 3.

FIG. 2 is a block diagram showing the observer circuit 5 of FIG. 1 in more detail. The observer circuit 5 includes a current comparison control unit 11, a speed comparison control unit 12, an observer control unit 13, a lead angle calculation unit 18a, and a current data memory 15. The lead angle calculation unit 18a further includes a model calculation CPU 14, a motor model memory 16, and a RAM.
17 is provided.

The speed comparison control unit 12 receives the command pulse c1 from the target command unit 9 and the signal c6 from the encoder 8 and converts them into data representing angular displacement per unit time, that is, angular velocity. And calculate
A speed deviation signal is generated and output to the observer control unit 13. When the command pulse c1 and the encoder signal c6 are position signals, the deviation of the differential value of each signal is calculated, and when it is a speed signal, the deviation is calculated directly. The current comparison control unit 11 compares the current detection value from the current detection circuit 6 with the correction current value from the observer control unit 13, generates a current correction signal, and outputs it to the current control circuit 3.

The current data memory 15 stores an input current set value relating to the motor winding. The motor model memory 16 stores a theoretical expression describing the operation characteristics of the stepping motor 7. The RAM 17 temporarily stores values calculated during the calculation by the CPU 14 for model calculation. The model calculation CPU 14 calculates the input lead angle set value by solving the theoretical formula in the motor model memory 16, and outputs it to the observer control unit 13.

The observer control unit 13 corrects the input lead angle set value according to the deviation amount based on the speed deviation signal. That is, when a larger load disturbance occurs and the rotation angle of the stepping motor 7 fluctuates greatly, the lead angle is corrected to surely compensate for this state by the energy generated by the stepping motor 7 itself. This lead angle correction signal is output to the selection control circuit 2 of FIG. Further, the observer control unit 13 extracts an input current set value from the current data memory 15 based on the speed deviation signal from the speed comparison control unit 12, and generates a corrected current value. For example,
When a larger load disturbance occurs and the motor rotation speed is greatly reduced, the current value is corrected so as to increase the current value in order to surely compensate for the reduced amount with the input energy.

FIG. 3 is a graph showing a target rotational angular velocity on which a command pulse is based. According to the graph, first, the stepping motor 7 starts from the stationary state at the angular acceleration A0. Thereafter, the angular velocity of the stepping motor 7 increases as the angular acceleration increases. When the angular acceleration reaches the maximum angular acceleration A1, the angular velocity increases while the angular acceleration decreases. When the angular velocity reaches ω1, the stepping motor 7 continues to rotate at a constant angular velocity ω1. Thereafter, the stepping motor 7 starts to decelerate, and its angular acceleration decreases until it reaches the negative maximum angular acceleration A2, and the angular velocity also decreases accordingly. When the negative maximum angular acceleration A2 is reached, the angular velocity decreases while the absolute value of the angular acceleration decreases. The angular acceleration decreases to A3, and the angular velocity and the angular acceleration become zero, that is, the stepping motor 7 stops.

In order to make the stepping motor 7 perform such a rotational movement, the target command unit 9 directly or integrates the graph of FIG. 3 and sequentially outputs the target angular velocity or the target rotation angle as a command pulse. As a result, the stepping motor 7 calculates the number of steps s from the rotation angle of the start position.
Accelerate smoothly in the acceleration section up to 1 and the number of steps s
The rotation is performed at a constant angular speed of up to two constant velocity portions, and the speed is smoothly reduced to the target positioning position of the number of steps s3.

FIG. 4 is a table showing the contents stored in the current data memory 15. An input current set value is stored in the current data memory 15. The input current set value is a value that determines the winding current according to the command pulse, and is an average current value between each command pulse in a state where there is no disturbance. A table exists for each of the acceleration section, constant velocity section, and deceleration section. The counter indicates the number of command pulses counted. In the acceleration unit, first, the input current set value is set to 1.0 amp, the torque required for starting is secured, and the current value is gradually decreased as the angular velocity of the stepping motor 7 increases. The required driving current decreases as the speed increases due to the influence of the inductance of the windings and the like, so that acceleration is continued even if the current value is reduced.

In the constant velocity section, a constant input current set value of 0.
Although the current is 5 amps, the acceleration is suppressed by smoothly reducing the current value to 0.45 amperes, which is lower than 0.5 amps, before shifting to the constant speed section. Is possible. After reducing the current value to 0.45 amps at the transition from the constant velocity section to the deceleration section,
The current value is gradually increased. Also, by increasing the input current set value to 1.0 amp before stopping,
The rotation of the stepping motor 7 is stopped smoothly.

FIG. 5A shows a reference lead angle table used by the selection control circuit 2, and FIG. 5B shows a reference current table. In FIG. 5 (a), when the stepping motor 7 is rotated at a relatively low speed and a high torque, such as at the time of startup, ones near the selection numbers 4 to 6 are selected. on the other hand,
When braking the rotation of the stepping motor, such as during deceleration, a smaller selection number is selected. Also, as the rotation speed increases, a larger reference lead angle is selected to secure a necessary current. The acceleration unit starts at the reference lead angle of 1.5 steps, and switches to 2.0 steps in the high speed range. In the constant velocity section, the lead angle is 2.
Operation is continued at step 0. In the deceleration section, the lead angle is 2.0
From the steps, 1.5 steps, 1.0 steps, 0.
The stepping motor 7 is stopped by sequentially switching from 5 steps to 0 steps.

Also, in FIG. 5B, a smaller reference current value is selected as the rotation becomes more stable as in a constant velocity portion, and a larger reference current value as the rotation becomes faster as in an acceleration portion and a deceleration portion. The value is selected. When the normal rotation angle deviation is small, 1.0 amp is selected as the reference current value in the acceleration section and the deceleration section, and 0.5 amp in the constant velocity section.

Further, when the external load torque increases during the operation of the stepping motor 7, the acceleration section and the constant velocity section increase the value of the lead angle table and also increase the value of the current table. A selection operation is performed.
This is control for increasing the acceleration torque. In the deceleration section, the value of the current table is reduced while the slope of the decrease curve of the lead angle is relaxed. This is a control for reducing the brake torque. Furthermore, the external load torque is
If the value decreases during the operation of the stepping motor 7, a selection operation is performed in the acceleration unit and the constant speed unit such that the value of the lead angle table is reduced and the value of the current table is also reduced. This is control for reducing the acceleration torque. In the deceleration unit, the value of the current table is increased while the slope of the lead angle decreasing curve is steep. This is control for increasing the brake torque.

FIG. 6A is a graph showing signals from the target command unit 9 and the encoder 8 to the position comparison control unit 1, and FIG. 6B is a graph showing signals from the position comparison control unit 1 to the selection control unit 2. It is a graph which shows a signal. First, as shown in FIG. 6A, the position of the target rotation angle indicated by the command pulse is fixed to the rotation angle ω2 from time t0 to time t1. At time t0, the position of one output rotation angle is smaller than the target rotation angle, and increases rapidly until time t2 to follow the target rotation angle. When the output rotation angle matches the target rotation angle at time t2, the rate of change becomes gentle. continue,
At time t1, when the position of the target rotation angle is switched and increases to ω3 in a stepwise manner, the position of the output rotation angle rapidly increases again and approaches ω3. A similar signal change is seen for speed.

As shown in FIG. 6B, at times t0 to t2
, The position deviation signal c2 is the rotation angle ω4, and the encoder signal c6 is regarded as being delayed by the rotation angle ω4 from the command pulse c1. From time t2 to t1, the position deviation signal c2 has the rotation angle ω5, and it is assumed that the encoder signal c6 has advanced by the rotation angle ω5 with respect to the command pulse c1. In addition, after t1, such a concept is continued. FIG. 6B does not correspond to the absolute value deviation shown in FIG. 6A, but shows a general deviation signal.

FIG. 7A is a graph showing signals from the position comparison control unit 1 to the selection control unit 2 as in FIG. 6B, and FIG. 7B is a graph showing signals from the observer circuit 5 to the selection control circuit 2.
FIG. 7C is a graph showing a signal from the selection control circuit 2 to the drive circuit 4, and FIG.
(D) is a graph showing a signal from the selection control circuit 2 to the current control circuit 3. With respect to the position deviation signal of FIG. 7A, a pulse signal having a constant pulse rate is input to the selection control circuit 2 as a lead angle correction signal and modulated as shown in FIG. A pulse signal having an uneven pulse rate as shown in c) is output to the drive circuit 4. This pulse signal is a signal representing the final lead angle. Time t
The vicinity of 2 indicates that the stepping motor 7 is decelerating, and the vicinity of time t1 indicates that it is accelerating. The reference current value signal in FIG. 7D is a signal having the same shape based on the position deviation signal, and indicates that the reference current is proportional to the position deviation.

FIG. 8A is a graph showing signals from the selection control circuit 2 to the current control circuit 3 as in FIG. 7D, and FIG. 8B is a graph showing signals from the observer circuit 5 to the current control circuit 3.
FIG. 8C is a graph showing a signal from the current control circuit 3 to the drive circuit 4. FIG.
As shown in (b), the current correction signal is a signal for decreasing the current value in a stepwise manner.
The signal is modulated by the reference current value, and becomes a signal for commanding the final current shown in FIG.

Hereinafter, the theoretical formula stored in the observer circuit 5 will be described.

[0039]

(Equation 1)

Equation (1) is a spanworm equation for the stepping motor 7. The span worm equation is an equation of motion related to the rotation angle of the stepping motor 7. Where t is time, θ is stepping motor 7
, M is the order of the Fourier series, n is the phase number, k is a step function representing the integrated value of the signal pulse, tc is the activation time of the first signal pulse, θo is the advance angle per single step,
θπ is the half wavelength of the driving torque distribution, θs is the origin angle position set at θ, I is the moment of inertia, C is the damping coefficient, Q is the load torque, q is the driving torque, φ is the phase angle, and φm is the Fourier series of φ. The m-th order coefficient of expansion, Γ, is a torque weighting function.

By solving this equation (1) on the basis of various approximations,
As shown in Expression (2), a linear approximation solution that qualitatively indicates the starting limit and the behavior is obtained.

[0042]

(Equation 2)

Here, ts is the time of the set origin, to
Is the pulse interval time, γ is the damping ratio, po is the primary resonance point, sgn (x) is a function that is 1 when x is positive and 0 when x is negative, and Π (x) is a step function of Heaviside. It is. The observer circuit 5 is useful when, for example, such an approximate solution is stored and applied near the start time.

[0044]

(Equation 3)

FIG. 9A is a circuit diagram showing a drive circuit for a four-phase motor, and FIG. 9B is a circuit diagram showing a pair of phases extracted from the drive circuit of FIG. 9A. is there. Equation (3)
Is the voltage equation of FIG. Where i1 is R
, Rw1 and the current flowing through L1, i2 is the current flowing through Rw1 and Rw2
, L2, C and L1, R is a series resistance component, Rw1 is the electric resistance component of the excited winding, Rw2 is the electric resistance component of the non-excited winding, and L1 is the excited winding. L2 is the inductance component of the non-excited winding, C is the damping coefficient between Rw1 and Rw2, V is the back electromotive force voltage, and Vs is a constant applied voltage. In equation (3), the voltage V as the back electromotive force
If it understands, the back electromotive force coefficient Ke will be calculated | required by following Formula (4).

[0046]

(Equation 4)

Further, the first term of the driving torque is expressed by the following equation (5).
Required by

[0048]

(Equation 5)

Equations (1) and (3) express the operating characteristics of the stepping motor 7 in consideration of the character constant of the current rise of the electric circuit. Can be analyzed.

FIG. 10 is a diagram showing the control operation of the first embodiment. In step a1, a command pulse indicating the target rotation angle or the target rotation angular velocity is output from the target command unit 9. On the other hand, in step a2, a signal indicating the output rotation angle or the output rotation angular velocity is output from the encoder 8. Next, in step a3, 2) position or speed deviation data is generated from 1) output rotation angle, that is, current position data, or rotation angular speed, that is, current speed data. In step a4, the drive current of the stepping motor 7 is detected to obtain the current data. Next, in step a5, 1) solve the span warm equation using the current speed data and current data,
2) Estimate the load of the stepping motor 7 from the deviation data and 3) Calculate the optimal lead angle (lead angle) and the optimal current value.

As described above, in the control device which drives the stepping motor 7 by designating the excitation timing for each command pulse, the rotation angle of the stepping motor 7 is fed back to newly select the excitation timing determined by the command pulse. The reference current value is corrected, and the excitation timing and the current value are re-corrected by the processing of the observer circuit based on the rotation speed and the actually measured current value.
The observer circuit 5, which is a feature of the present invention, obtains an expected rotation state of the motor based on a theoretical equation of motion, further obtains an ideal input current set value in advance, and obtains data obtained by feedback. Is further corrected again.

(Second Embodiment) FIG. 11 shows a second embodiment of the present invention.
FIG. 3 is a block diagram of an observer circuit 55 constituting the embodiment. In the control device according to the second embodiment, the lead angle calculation unit 18a of the observer circuit 5 in FIG. 2 is replaced with a numerical solution table storage unit to form an observer circuit 55. The numerical solution table storage unit 18 stores a numerical solution table obtained by simultaneously solving the equations (1) and (3) of the first embodiment. Accordingly, the command pulse is directly output to the observer control unit 13, and the observer control unit 13 performs control to retrieve an appropriate numerical solution by referring to the numerical solution table storage unit 18.

FIG. 12 is a table stored in the numerical solution table storage unit. The table includes the motor rotation speed indicated by the command pulse and the correction advance angle. Thus, the motor rotation speed V _p1, V _p2, ..., corrected lead angle theta _v1 corresponding to _{V pn, θ v2, ...,} θ vn is selected. A plurality of such tables are prepared so as to be compatible with various types of stepping motors.

FIG. 13 is a flowchart showing the processing flow of the second embodiment. In step b1, a command pulse indicating the target rotation angle or the target rotation angular velocity is output from the target command unit 9. On the other hand, in step b2, a signal indicating the output rotation angle or the output rotation angular velocity is output from the encoder 8. Next, in step b3, 2) position or speed deviation data is generated from 1) output rotation angle, that is, current position data, or rotation angular velocity, that is, current speed data. In step b4, the drive current of the stepping motor 7 is detected to obtain the current data. Further, in step b5, the advance worm data table is created by solving the span worm equation using predetermined speed data and current data. Next, in step b6, a lead angle correction value and a current correction value are calculated in step b7 based on the current position or speed data, the current data, and the deviation data while referring to the current data table and the lead angle data table. Then, the optimum current value and the optimum lead angle are calculated.

As described above, also in the second embodiment, the optimum current value and the optimum lead angle can be obtained as in the first embodiment. However, in the second embodiment, since the spanworm equation is solved before driving the stepping motor 7, it is only necessary to refer to the created table during driving, and high-speed control is possible.

In both the first embodiment and the second embodiment, a configuration without a current detection circuit is possible. In this case, the observer circuit advances based on only the target rotation angle and the output rotation angle. An angle correction value and a current correction value are calculated.

[0057]

As described above, according to the present invention, the observer circuit storing the operating characteristics of the stepping motor corrects the lead angle and the current based on the target rotation angle and the output rotation angle. Since the operation of the stepping motor is closely monitored, it is possible to cope with a sudden load change and the like, and to realize a stable operation.

According to the present invention, the observer circuit includes:
Since the stepping motor is controlled based on the span worm equation, the operating characteristics can be accurately grasped, and more accurate control is possible.

Further, according to the present invention, since the numerical solution table prepared by previously solving the above-described span worm equation is used for controlling the stepping motor, high-speed control is possible, and it is possible to cope with a sudden load change. Thus, the stepping motor can be operated stably.

According to the present invention, the observer circuit includes:
In addition to the target rotation angle and the output rotation angle, the lead angle correction value and the current correction value are obtained based on the detected current.
The operating characteristics can be accurately grasped based on more information, and the lead angle and the current can be accurately corrected to realize more stable operation.

According to the present invention, as described above, the observer circuit storing the operation characteristics of the stepping motor corrects the lead angle and corrects the current while referring to the target rotation angle and the output rotation angle. As a result, the operation of the stepping motor is monitored in detail, so that it is possible to cope with a sudden load change or the like, and to realize a stable operation.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an electrical configuration of a first embodiment of the present invention.

FIG. 2 is a block diagram showing the observer circuit 5 of FIG. 1 in further detail.

FIG. 3 is a graph showing a target rotation angular velocity on which a command pulse is based;

FIG. 4 is a table showing contents stored in a current data memory 15;

5A is a reference lead angle table used by the selection control circuit 2, and FIG. 5B is a reference current table.

FIG. 6A shows a target command unit 9 and an encoder 8;
6A and 6B are graphs respectively showing signals from the position comparison control unit 1 to the position comparison control unit 1. FIG.
6 is a graph showing a signal to the control unit.

7A is a graph showing signals from the position comparison control unit 1 to the selection control unit 2 as in FIG. 6B, and FIG. 7B is a graph showing signals from the observer circuit 5 to the selection control circuit 2; 7 (c) is a graph showing a signal from the selection control circuit 2 to the drive circuit 4, and FIG. 7 (d) is a graph showing a signal from the selection control circuit 2 to the drive circuit 4.
Is a graph showing signals from the selection control circuit 2 to the current control circuit 3.

8A is a graph showing signals from the selection control circuit 2 to the current control circuit 3 as in FIG. 7D, and FIG. 8B is a graph showing signals from the observer circuit 5 to the current control circuit 3; FIG. 8C is a graph showing a signal from the current control circuit 3 to the drive circuit 4.

9 (a) is a circuit diagram showing a drive circuit 4 for a four-phase motor, and FIG. 9 (b) is a circuit obtained by extracting a pair of phases from the drive circuit 4 of FIG. 9 (a). FIG.

FIG. 10 is a diagram illustrating a control operation according to the first embodiment.

FIG. 11 is a block diagram of an observer circuit 55 constituting a second embodiment of the present invention.

FIG. 12 is a table stored in a numerical solution table storage unit 18.

FIG. 13 is a flowchart illustrating a processing flow according to the second embodiment.

FIG. 14 is a diagram showing conventional closed-loop control of a stepping motor by FREDRIKSEN.

FIG. 15 is a diagram showing closed loop control of Japanese Patent Publication No. 57-34758.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Position comparison control part 2 Selection control circuit 3 Current control circuit 4 Drive circuit 5,55 Observer circuit 6 Current detection circuit 7 Stepping motor 8 Encoder 9 Target command part 10 Control circuit 11 Current comparison control part 12 Speed comparison control part 13 Observer control Unit 14 Model calculation CPU 15 Current data memory 16 Motor model memory 17 RAM 18 Numerical solution table storage unit

Claims (5)

[Claims] 1. A stepping motor, driving means for driving the stepping motor, detecting means for detecting an output rotation angle of the stepping motor and outputting a rotation angle signal, and storing a speed function from start to stop of the motor. Commanding means for outputting a target command signal based on the speed function; comparing means for comparing the target command signal with the rotation angle signal; and determining a drive advance angle and a drive current of the stepping motor based on the comparison result. Control means for correcting the drive advance angle and the drive current output by the control means based on the target command signal and the rotation angle signal by simulating the operation characteristics of the stepping motor to be used. An observer circuit for outputting a lead angle correction signal and a current correction signal. Control device. 2. The control device for a stepping motor according to claim 1, wherein the observer circuit has a motor model for sequentially calculating a span worm equation describing operation characteristics of the stepping motor. 3. The control device for a stepping motor according to claim 1, wherein said observer circuit has a numerical solution table storing a result of previously calculating a span warm equation describing operation characteristics of the stepping motor. 4. A current detecting means for detecting a driving current of the stepping motor and outputting a current signal, wherein the observer circuit outputs a current signal, a target command signal, and a rotation angle signal based on an output of the control means. 2. The stepping motor control device according to claim 1, wherein the controller outputs a lead angle correction signal and a current correction signal for correcting the driving lead angle and the driving current, respectively. 5. A step of detecting an output rotation angle of a stepping motor to obtain a rotation angle signal; a step of comparing a target command signal and the rotation angle signal to determine a drive advance angle and a drive current of the stepping motor; Calculating a lead angle correction signal and a current correction signal based on the target command signal and the rotation angle signal by simulating the operation characteristics of the stepping motor to be used; Correcting the drive advance angle and the drive current based on the control method, respectively.