JPH07308094A - Driving apparatus for stepping motor - Google Patents

Abstract

PURPOSE:To provide a driving apparatus for stepping motors that prevents the increase of hardware and/or software and makes possible accurate current control. CONSTITUTION:Current passing through switching elements 14a1-4 is detected by means of a shunt resistor 13a1, and input to an interrupt comparator 15. Target current is set through a microcomputer 11 and input to the comparator 15. When an actual current exceeds a target current, the computer 11 is interrupted, and an off command is output to the switching elements. When a specified interrupting time has passed, an on command is output to the switching elements.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a stepping motor driving device, and more particularly to a stepping motor driving device for partially controlling a driving current in a closed loop.

[0002]

2. Description of the Related Art Stepping motors include: Open-loop control is possible because the rotation angle is proportional to the number of input pulses. 2. Since the rotation speed is proportional to the frequency of the input pulse, a wide range of rotation speed control is possible. 3. The stop position is maintained when there is no input pulse, so no brake or lock mechanism is required. 4. High reliability because there are no sliding parts such as brushes. 5. Since it is driven by pulses, it can be driven directly by a digital device such as a microcomputer. It has been used in various fields because of its characteristics.

FIG. 1 is a functional diagram of a stepping motor drive device that has been conventionally used. A rotation direction / angle determining unit 111 includes an accelerator pedal (not shown) detected by an accelerator sensor (not shown), for example. Step A)
The throttle valve opening set value St is generated based on c. The drive pattern generation unit 112 uses the throttle valve opening setting value S
Phase switching signals Ta and Tb that determine the excitation current setting value It and the rotation direction based on t are generated.

The exciting currents Ia and Ib that actually flow through the stepping motor 12 are the exciting current detectors 13a and 1a.
3b, converted into a digital signal by the A / D converter 114, and then compared with the exciting current set value It in the exciting current control unit 113. The exciting current controller 113 controls the exciting current setting value It and the exciting currents Ia and I.
Based on the deviation current of b, the control signals Da and Db for controlling the duty ratio of the drive power source are output to the drive circuits 14a and 14b.

The drive circuits 14a and 14b are so-called H bridges, respectively, and have phase switching signals Ta and T, respectively.
The direction of the current flowing through the drive coils 12a and 12b is controlled by b, and the amount of the current flowing through the drive coils 12a and 12b is controlled by the control signals Da and Db. The rotation direction / angle determination unit 111, the drive pattern generation unit 112, the excitation current control unit 113, and the A / D converter 114 are configured as a so-called microcomputer system 11.

However, in order to accurately control the current, the exciting currents Ia and Ib must be taken into the microcomputer 11 at short time intervals of several tens of microseconds, and therefore the microcomputer must have high performance. Not only that, but also the software had to be large-scale. In order to solve the above problems, a stepping motor drive device has also been proposed in which a duty ratio for supplying a predetermined current is stored in advance and the current is open-loop controlled.

[0007]

However, when the stepping motor changes over time or the operating environment changes, the current actually flowing through the stepping motor cannot be maintained at a predetermined value and the drive characteristics deteriorate. It is difficult to avoid things. The present invention has been made in view of the above problems, and an object of the present invention is to provide a stepping motor drive device capable of suppressing an increase in hardware and software and performing accurate current control.

[0008]

A stepping motor drive device according to a first aspect of the present invention includes drive coil control means for controlling current supply to a drive coil of a stepping motor,
Current detection means for detecting a current flowing through the drive coil of the stepping motor controlled by the drive coil control means, target current setting means for setting a target current in at least one step, and the current detected by the current detection means is the target current. A current comparison unit whose output signal is inverted when a target current of at least one stage set by the setting unit is reached;
Command output means for outputting a current cutoff command to the drive coil control means after detecting the inversion of the output signal in the current comparison means and then outputting a current supply command to the drive coil control means. , Are provided.

In the stepping motor drive device according to the second aspect of the present invention, the command output means has at least one set of command output means corresponding to at least one step of the target current output from the target current output means. The target cutoff time which is the cutoff time being output and the command output time storage means which stores the target supply time which is the supply time when the command output means is outputting the current supply command, and the command output time storage means A current different from the at least one-step target current set by the target-current setting means based on at least one set of target cutoff time and target supply time corresponding to at least one-step target current set by the target-current setting means Supply for determining a cutoff time and a supply time for the drive coil control means for supplying the drive coil of the stepping motor It includes between determining means.

In the stepping motor drive device according to the third aspect of the present invention, the stepping motor is provided between the drive coil control means and the power supply for supplying power to the drive coil control means, and the drive coil of the stepping motor. Allowable current setting means for determining the maximum allowable current, and drive coil control means for driving the cutoff means when the current detected by the current detection means exceeds the allowable current set by the allowable current setting means. Supply stopping means for stopping the power supply to the device.

[0011]

In the stepping motor drive device according to the first aspect of the present invention, it is judged by the comparator whether or not the actual current exceeds the target current, and when the actual current exceeds the target current, an interrupt is sent to the microcomputer. Light
This interruption outputs an OFF command to the switching element, and outputs an ON command to the switching element again after a lapse of a predetermined cutoff time.

In the stepping motor drive device according to the second aspect of the invention, when controlling the current between the target current levels, the on-time off time calculated from the on-time off-time of the switching element at the target current level. By controlling the switching element on the basis of, the microstep drive is realized. In the stepping motor drive device according to the third aspect of the present invention, the power supply is stopped when the current flowing through the switching element exceeds the maximum allowable current.

[0013]

FIG. 2 is a circuit diagram of a stepping motor drive device according to the present invention (only the A-phase drive circuit is shown). The same elements as those in the functional diagram shown in FIG. To do. That is, the microcomputer 11 is the bus 11
It is composed of a CPU 11b, a memory 11c, an input interface 11d, an output interface 11e, and a D / A converter 11f centering on a.

The drive circuit 14a is composed of bridge-connected switching elements 14a1 to 4a and a drive logic 14a5, and the A-phase drive coil 12a is connected to one diagonal of the bridge. The other diagonal of the bridge is connected to the power bus 19 and ground, and the bridge and power bus 1
A shunt resistor 13a1 for detecting a current flowing through the relay 18 and the bridge is provided between the shunt resistor 13a1 and the relay 9.

The voltage generated across the shunt resistor 13a1 is supplied to one input terminal of the interrupt comparator 15 and the stop comparator 1 via the buffer amplifier 13a2.
6 is connected to one terminal. Further, the other one terminal of the interrupt comparator 15 is connected to the D / A converter 11f, and the other one terminal of the stop comparator 16 is a reference voltage source corresponding to the maximum allowable current I _max that can be passed through the drive coil 12a. 161 is connected.

The output of the interrupt comparator 15 is the CPU
Connected to the interrupt terminal of 11b, stop comparator 1
The output of 6 is connected to the drive coil of the relay 18 via the logic circuit 17. FIG. 3 shows a microcomputer 11.
6 is a flowchart of a target current setting routine executed in step S6, which is executed at regular time intervals.

In step 31, for example, the accelerator pedal depression amount A which is the output of an accelerator sensor (not shown).
The stepping motor drive current I _p is determined according to c. In step 32, the index j indicating the current set level of the target current I _T is stored in j _b , and the process proceeds to step 33. In step 33, it is determined whether or not the drive current I _p is equal to or less than I _T (j). If a positive determination is made, the index j is decremented in step 34, and the process returns to step 33.

If a negative decision is made in step 34, it proceeds to step 35 to decide whether or not the drive current I _p is equal to or less than I _T (j + 1). If a negative decision is made, the index j is incremented in step 36. Step 33
Return to. If an affirmative decision is made at step 35, then the processing advances to step 37, at which it is decided whether or not the indexes j and j _b match, and if an affirmative decision is made, this routine is ended.

When a negative decision is made in step 37, the routine proceeds to step 38, where the target current I _T (j) is output and this routine is ended. The target current I _T (j) is converted into an analog voltage by the A / D converter 11f and supplied to the other terminal of the interrupt comparator 15. FIG. 4 is a flowchart of a command output routine executed by the microcomputer 11, which is executed every time an interrupt pulse is output from the interrupt comparator 15.

In step 41, the current target current I
Determine the cutoff time T _C as a function of _T (j). T _C = T _C { _IT (j)}. In step 42, the output interface 11
An off command is output to the switching element 15a1 or 15a2 via e and the drive logic 14a5.

In step 43, it is determined whether or not the cutoff time T _C has elapsed after the OFF command is output. If a negative determination is made, the process waits in step 43. If an affirmative decision is made at step 43, then the processing advances to step 44, at which an ON command is outputted to the switching element 15a1 or 15a2 in accordance with the rotation direction of the stepping motor, and this routine is ended.

FIG. 5 is a timing chart for explaining the operation of the stepping motor drive device according to the first invention.
The horizontal axis represents time, the vertical axis represents current, the interrupt pulse output from the interrupt comparator, and the current control command output. From time t ₀ to t ₁ , the target current level is I
_The target current level is _T (1), and the voltage corresponding to the target current level I _T (1) is output to the other terminal of the interrupt comparator 15.

The actual current increases from time t ₀ to time t ₀₁ when the switching element 15a1 is turned on. This actual current is detected as a voltage generated across the shunt resistor 13a1 and is supplied to one terminal of the interrupt comparator 15 via the buffer amplifier 13a2.

When the actual current exceeds the target current level I _T (1) at time t ₀₁ , an interrupt pulse is output from the comparator 15 and the above-mentioned command output routine is executed. Breaking time T corresponding to the target current level I _T (1)
_{During C} , the switching element 15a1 is off.

At time t ₀₂ , the switching element 15a1 is turned on again when the cutoff time T _C has elapsed, and this operation is repeated thereafter. Target current level I at time t ₁
To increase the _T (1) to I _T (2), the switching element 15a1 until the actual current reaches the target current level I _T (2) is turned on continuously.

In order to make the stepping motor rotate smoothly, it is necessary to increase the number of target current levels I _T , but inevitably the interrupt comparator 15 is supplied with a voltage corresponding to the target current level I _T. D / A converter 1
It is also necessary to increase the number of bits of 1f. Therefore, according to the stepping motor drive device of the first invention, it is inevitable that the device becomes expensive.

A stepping motor drive device according to a second aspect of the present invention is for solving the above-mentioned problems, and
The present invention provides a stepping motor driving device that can realize so-called microstep driving without increasing the number of bits of the / A converter 11f. FIG. 6 is a timing chart for explaining the operation of the stepping motor drive device according to the second invention, which is a D / A converter 11f.
The target current level output from is, for example, two levels of _IT (1) and _IT (3).

FIG. 7 is a flow chart of an operation mode switching routine used in the stepping motor drive device according to the second invention. In step 71, it is determined whether or not the micro step drive is performed. If a negative determination is made in step 71, the process proceeds to step 72 to execute the on / off time storing process, and if a positive determination is made in step 71, the step 73 is performed.
Then, the routine proceeds to step 1 to execute the micro step drive processing, and this routine is ended.

FIG. 8 is a detailed flowchart of the on / off time storing process in step 72. In step 72a, it is determined whether or not there is a change in the target current level, for example, a change from level 1 to level 3, and if a negative determination is made, step 7
Proceed to 2b. In step 72b, it is determined whether or not the current target current level is "1", that is, whether the index j is "1".

If an affirmative decision is made in step 72b, the operation proceeds to step 72c, in which the switching element ON time T _ON (1)
The switching element off time T _OFF (1) is stored, and the process proceeds to step 72d. If a negative determination is made in step 72b, the process directly proceeds to step 72d. Step 72d
Whether the current target current level is “3”,
That is, it is determined whether or not the index j is "3".

If an affirmative decision is made in step 72d, the operation proceeds to step 72e, and the switching element ON time T _ON (3)
Then, the switching element off time T _OFF (3) is stored, and this processing ends. If a negative decision is made in step 72d, this routine is ended directly. Step 72a
If a positive determination is made in step 72f, the process proceeds to step 72f, the transition time T _ON (13) from reaching the target current level “1” to “3” is stored, and this processing ends.

FIG. 9 is a detailed flowchart of the microstep process of step 73. In step 73a, it is determined whether or not the target current level is changed, and if an affirmative determination is made, the process proceeds to step 73b. In step 73b, it is determined whether or not the level is changed from "1" to "2". If an affirmative determination is made, the switching time _Tc is calculated by the following equation in step 73c and the process proceeds to step 73d.

T _c = T _ON (12) = g {T _ON (13), _IT (3), _IT (2), I
_T (1)} If negative determination is made in step 73b, step 73d is directly executed.
Proceed to. In step 73d, it is determined whether or not the level is changed from "2" to "3". If an affirmative determination is made, the switching time _Tc is calculated by the following equation in step 73e and the process proceeds to step 73f.

T _c = T _ON (23) = G {T _ON (13), _IT (3), _IT (2), I
_T (1)} If negative determination is made in step 73d, step 73f is directly executed.
Proceed to. In step 73f, for example, an ON command is output to the switching element 14a1 and the process proceeds to step 73g.

In step 73g, it is determined whether or not the switching time _Tc after the ON command is output has elapsed, and if a negative determination is made, the process returns to step 73f. If an affirmative decision is made in step 73g, the operation proceeds to step 73h, for example, an OFF command is outputted to the switching element 14a1 and this routine is ended. When a negative determination is made in step 73a, the target current level I _T proceeds to step 73i is "2"
Or not.

When a positive determination is made in step 73i, that is, when the target current I _T cannot be set in the interrupt comparator 15, the process proceeds to step 73j, and the ON time of the switching element when the target current level I _{T is set} to "2". The T _ON and the off time T _{OF F} are calculated by the following equations. T _ON (2) = h {T _ON (3), T _ON (1), _IT (3), I
_T (2), _IT (1)} T _OFF (2) = H {T _ON (3), T _ON (1), _IT (3), I
_T (2), in I _T (1)} step 73k, the routine ends by controlling on and off of the switching element based on the on-time T _ON and the off time T _OFF which set in step 73j.

When a negative decision is made in step 73i, the routine proceeds to step 73l, where the command output routine shown in FIG. 4 is executed and this routine is ended. According to the stepping motor drive device of the third aspect of the present invention, it is possible to reliably prevent the current flowing through the switching elements 14a1 to 14a from exceeding the maximum allowable current.

Therefore, the stop comparator 16, the logic circuit 17 and the relay 18 are additionally provided. A voltage proportional to the actual current detected by the shunt resistor 13a1 is applied to one terminal of the stop comparator 16, and a reference voltage corresponding to an allowable current is applied from the constant voltage source 161 to the other terminal.

When the actual current exceeds the allowable current, the output of the stop comparator 16 is inverted, the relay 18 is cut off via the logic circuit 17, and the power supply to the stepping motor is stopped. A stop signal output from the microcomputer 11 is also input to the logic circuit 17.

[0040]

According to the stepping motor drive device of the first aspect of the present invention, it is possible to accurately control the current flowing through the switching element with a simple configuration by appropriately distributing the functions in hardware and software. It will be possible. According to the stepping motor drive device of the second aspect of the present invention, it is possible to realize the micro step drive of the stepping motor without increasing the hardware.

According to the stepping motor drive device of the third invention, by adding simple hardware, it is possible to prevent the current flowing through the switching element from exceeding the maximum allowable current and damaging the switching element. It will be possible.

[Brief description of drawings]

FIG. 1 is a functional diagram of a stepping motor drive device that has been conventionally used.

FIG. 2 is a circuit diagram of a stepping motor drive device according to the present invention.

FIG. 3 is a flowchart of a target current setting routine.

FIG. 4 is a flowchart of a command output routine.

FIG. 5 is a timing chart for explaining the operation of the stepping motor drive device according to the first invention.

FIG. 6 is a timing chart for explaining the operation of the stepping motor drive device according to the second invention.

FIG. 7 is a flowchart of an operation mode switching routine.

FIG. 8 is a flowchart of an on / off time storage process.

FIG. 9 is a flowchart of a micro step drive process.

[Explanation of symbols]

 11 ... Microcomputer 12a ... Stepping motor drive coil 13a1 ... Shunt resistor 13a2 ... Buffer amplifier 14a1-4 ... Switching element 14a5 ... Drive logic 15 ... Interrupt comparator 16 ... Stop comparator 17 ... Logic circuit 18 ... Relay

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI technical display location H02P 8/22

Claims (3)

[Claims] 1. A drive coil control means for controlling current supply to a drive coil of a stepping motor, and a current detection means for detecting a current flowing through a drive coil of the stepping motor controlled by the drive coil control means, at least 1. When a target current setting means for setting a step target current and the current detected by the current detection means reach at least one step target current set by the target current setting means, the output signal is inverted. A current cutoff command is output to the drive coil control means for a predetermined time after detecting inversion of the output signal of the current comparison means and the current comparison means, and then a current is output to the drive coil control means. A stepping motor drive device comprising: a command output unit that outputs a supply command. 2. A cutoff time during which the command output means outputs a current cutoff command by at least one set of the command output means corresponding to at least one step target current output from the target current output means. And a target output time storage means for storing a target supply time that is a supply time during which the command output means outputs a current supply command, and the target current setting stored in the command output time storage means. Based on at least one set of target cutoff time and target supply time corresponding to at least one step target current set by the means, a current different from the at least one step target current set by the target current setting means is set. Interruption supply time determining means for determining interruption time and supply time for the drive coil control means for supplying to the drive coil of the stepping motor When the stepping motor driving device according to claim 1 comprising a. 3. A breaking means installed between the drive coil control means and a power supply for supplying electric power to the drive coil control means, and a maximum allowable current that can flow to the drive coil of the stepping motor. Power supply to the drive coil control means by driving the cut-off means when the current detected by the current detection means is equal to or more than the current allowed by the current detection means. The stepping motor drive device according to claim 1 or 2, further comprising: a supply stopping means for stopping.