JP3662201B2 - Stepping motor driving circuit and driving method thereof - Google Patents

Description

[0001]
[Industrial application fields]
The present invention relates to a driving method and a driving circuit that can effectively suppress a damping vibration when a stepping motor is stopped.
[0002]
[Prior art]
Since the stepping motor performs step driving, it is inevitable that vibration is generated during driving. On the other hand, various devices equipped with stepping motors are becoming lighter, more accurate, and faster, and vibrations generated when driving stepping motors have adversely affected the accuracy of the devices themselves. At present, the basic characteristics of stepping motors are being questioned as a serious problem. In particular, an inspection apparatus for a semiconductor device or a semiconductor substrate requires an inspection speed of several tens of milliseconds (milliseconds) or several hundreds of milliseconds for one cycle, and if the workpiece is not completely stopped during that time, measurement is performed. Therefore, how quickly the stepping motor reaches the predetermined position and stops is an important factor.
[0003]
The stepping motor is basically step-driven for each pulse input. Therefore, when moving from a certain point to the next point, the rotor of the stepping motor receives the rotational force from the exciting coil and is accelerated from the stopped state, rotated by a predetermined angle, and stopped at the next stopping position. Damping vibration that repeats overshoot and undershoot due to moment and restoring force (force to pull the rotor back to the stop position when the rotor rotates beyond the stop position) occurs.
[0004]
That is, the rotor of the stepping motor connected to the load does not stop at a predetermined position (predetermined stop angle) due to the moment of inertia and passes (overshoots) without stopping. The overshooting rotor is decelerated by the restoring force and is pulled back toward a predetermined position (predetermined stop angle). At this time, since the restoring force in the pullback direction (reverse rotation direction) acts on the rotor, when the rotor reverses in the pullback direction, it is accelerated by this restoring force, and again passes through a predetermined position (predetermined stop angle) to cause undershoot. Wake up. After such a damped vibration in which overshoot and undershoot are alternately repeated, the vibration is stopped at the predetermined position (predetermined stop angle). The time during which this damped vibration continues is called settling time. In the above-described inspection apparatus, one cycle time is shortened to shorten the inspection time, and how to shorten the settling time in order to improve productivity is a very important problem.
[0005]
The settling time is shorter as the friction load of the stepping motor and the rotating part connected thereto is larger, and is longer as the inertia load is larger. Also, the higher the speed at the end of deceleration, the longer. When some vibration occurs during rotation, it resonates, drags the vibration, and prolongs the settling time. Therefore, a viscous coupling inertia damper, a magnetic coupling inertia damper, or the like is used.
[0006]
The viscous coupling inertia damper is a component that vibrates the rotor due to the reaction against the speed difference between the outer ring and the inner ring generated in the viscous material filled in the gap between the outer ring and the inner ring. Need extra. The magnetically coupled inertia damper suppresses vibration of the rotor by mechanical friction due to magnetic attraction generated between the mild steel body and the inertial body. In this case, too, extra torque is required at the start-up as in the previous day. In other words, using a damper or applying a friction load to the stepping motor suppresses the damping vibration at the time of stopping to some extent, but on the other hand, the required torque at the time of starting increases, and the stepping motor loses its step. It becomes easy.
[0007]
To prevent step-out, it is necessary to reduce the start speed of the command pulse and the acceleration time constant (ms / kNz). This means that the rotation speed of the stepping motor is slowed down, and the working efficiency of the apparatus is deteriorated.
[0008]
[Problems to be solved by the invention]
It is an object of the present invention to develop a stepping motor driving method and a driving circuit for the stepping motor in which the settling time is significantly shortened while maintaining a high starting characteristic without using the damper.
[0009]
[Means for Solving the Problems]
  “Claim 1” relates to the basic driving method of the stepping motor (1) according to the present invention. “The stepping motor (1) is supplied with an excitation current (i2) through the stepping motor (1) and according to a predetermined excitation sequence. In the method of stepping driving the stepping motor (1) by inputting the excitation switching pulse (P) to the drive controller (2),
(B) Simultaneously with the stop of command pulse (S) input to generate the excitation sequence or
(C) During deceleration of the previous stepping motor (1) or
(B) Stepping from the rotational operating current value that generates the torque required for the rotation of the stepping motor (1) within the settling time (t) when the damping vibration is generated in the stepping motor (1) before and after the subsequent stop position Stop position holding current value that generates the torque required to stop the motor (1)The excitation current value over a predetermined time or stepwiseIt is characterized by "lowering".
[0010]
  Thus, before and after the stop position, the excitation current is changed from the rotation operating current value to the stop position holding current value.Take a predetermined time or step by stepBy pulling down, the restoring force (F) of the stepping motor (1) (the force that the rotor (3a) and the stator (3b) attract)graduallyDecreasing vibrations that repeat and overshoot or downshoot converge in a short time, and the rotor (3a) of the stepping motor (1) stops at a predetermined position at the stop position holding current value. The optimum timing for lowering the stop position holding current value from the rotation operating current value is selected in accordance with the conditions of the apparatus in the above.If the rotation operating current value is suddenly lowered from the stop position holding current value, the restoring force decreases rapidly. Depending on the load, the stepping motor (1) Rotor (3a) The return will be worse. However, if the current value is lowered gently or stepwise in this way, the rotor (3a) The restoring force can be reduced in accordance with the return of the rotor. (3a) Can be set more smoothly.
[0011]
  “Claim 2” is a further improvement of “Claim 1”. “Excitation switching pulse of the stepping motor (1) is supplied to the stepping motor (1) by passing an excitation current (i2) and in accordance with a predetermined excitation sequence. In the method of stepping the stepping motor (1) by inputting (P) to the drive control unit (2),
(B) Simultaneously with the stop of command pulse (S) input to generate the excitation sequence or
(C) During deceleration of the previous stepping motor (1) or
(B) Stepping from the rotational operating current value that generates the torque necessary for the rotation of the stepping motor (1) within the settling time (t) when the damping vibration is generated in the stepping motor (1) before and after the subsequent stop position Stop position holding current value that generates the torque required to stop the motor (1)Reduce the excitation current value over a predetermined time or in steps, and reduce the excitation current value over a predetermined time or in steps.ReductionThe stop position holding current value isAfter holdingBefore the input timing of the next first command pulse“Return to the rotational operating current value”.
[0012]
  In this case, in addition to claim 1, after the stop position holding current value is reduced from the rotation operating current value, the stop position holding current value isStop position holding current value after settlingAfter holding, `` Before the input timing of the next first command pulseThe rotational activation current value is restored. ”In this way, the next start-up can be performed quickly. The predetermined time( That is, before the input timing of the next first command pulse )Necessary measurement is performed, and after completion of the measurement, the rotation operating current value is restored.
[0014]
  "Claim 3" is a first embodiment of a driving circuit for carrying out the driving method.
  (a) Input command pulse (S) Stepper motor based on (1) Drive controller (2) Excitation switching pulse (P) Enter the stepper motor (1) Control circuit that drives step by step according to excitation sequence (3) When,
  (b) ( B ) Command pulse (S) At the same time as ( C ) Before or ( B ) Stepping motor after that (1) Excitation current (i2) Stepper motor (1) Stepping motor from the rotational operating current value required for driving (1) Reduced reference voltage to reduce to the stop position holding current value necessary to hold the (VREF-L) The reference voltage up to is output over a predetermined time or stepwise, and after the settling, the stop position holding current value is held and then raised to raise the stop position holding current value to the rotation operating current value. Reference voltage (VREF-H) Reference voltage changer that outputs (K) When,
  (c) Stepping motor (1) Current to drive (i1 + i2-i3) Or (i2-i3) Sense voltage generated by (V1 + 2) Or (V2) And the reference voltage (VREF-H) Or (VREF-L) Or, compared with the reference voltage in the middle of both, excitation current from the rotation operating current value to the stop position holding current value over a predetermined time or stepwise (i2) The reference voltage raised to raise the stop position holding current value to the rotational operating current value after holding the stop position holding current value after settling (VREF-H) Output voltage comparison circuit (Four) It is characterized by comprising.
[0015]
  “Claim 4”Is a drive circuit for carrying out the drive method.In the second embodiment,
  (a) A control circuit that inputs the excitation switching pulse (P) to the drive controller (2) of the stepping motor (1) based on the input command pulse (S) and drives the stepping motor (1) stepwise according to the excitation sequence (3) and
  (b) (b) Simultaneously with input stop of command pulse (S), or (c) Before or (b) After that, the excitation current (i2) of the stepping motor (1) is changed to the stepping motor (1) Reduced reference voltage (VREF-L) to reduce the rotation operating current value required for driving the motor to the stop position holding current value required to hold the stepping motor (1) at the stop positionThe reference voltage up toOutput,After holding the stop position holding current value after settling,A reference voltage changing unit (K) for outputting a raised reference voltage (VREF-H) for raising the stop position holding current value to the rotation operating current value;
  (c) Stepping motor (1) Current to drive (i1 + i2-i3) Or (i2-i3) Sense voltage generated by (V1 + 2) Or (V2) And the reference voltage (VREF-H) Or (VREF-L) Alternatively, after comparing the reference voltage in the middle of the two and reducing the excitation current from the rotation operating current value to the stop position holding current value over a predetermined time or stepwise, and holding the stop position holding current value after settling Next first command pulse (Ps) The reference voltage raised to raise the stop position holding current value to the rotation operating current value before the input timing of (VREF-H) OutputAnd a voltage comparison circuit.
[0016]
  "Claim 5""Claim 3 or 4In the drive circuit described in `` The reference voltage changing unit (K) measures the cycle of the input command pulse (S), and when the cycle of the input command pulse (S) becomes longer than the predetermined time, The command pulse (S) is judged to be the final command pulse, and the reference voltage (VREF-L) is output ”. Also,"Claim 6""Claim 3 or 4In the drive circuit described in `` The reference voltage changing unit (K) counts the number of input command pulses (S), and when the count reaches a predetermined number, the reference voltage (VREF-L) is "It is designed to output".
[0017]
In the former case, the reference voltage (VREF-L) is output after the final command pulse (S), but in the latter case, the reference voltage (VREF-L) is output before or simultaneously with the final command pulse (S). Will be.
[0019]
  As shown in claims 3 and 4,After a predetermined time( In other words, the next first command pulse (Ps) Before input timing )Since the lowered reference voltage (VREF-L) can be restored to the reference voltage (VREF-H), the stepping motor (1) is surely stopped at the stop position during workpiece measurement. Therefore, even if it is held by the weak stop position holding current value, it can be started immediately when the next operation command pulse is input to the stepping motor (1). Even if (1) is held, the rise characteristic is not impaired.
[0020]
BEST MODE FOR CARRYING OUT THE INVENTION
The present invention will be described below with reference to the illustrated embodiments. The first embodiment of FIG. 1 is a drive circuit for a five-phase stepping motor (1). Of course, the applied stepping motor (1) is not limited to a five-phase motor, but here, a five-phase motor will be described as a representative example. This drive circuit includes a control circuit (3) for inputting an excitation switching pulse to the drive control unit (2) of the stepping motor (1) and step-driving the stepping motor (1) according to the excitation sequence, and the stepping motor (1). A voltage comparison circuit (4) that detects the drive current, compares it with the reference voltage (VREF), and outputs a control signal to the control circuit (3) that lowers the excitation current from the rotation operating current value to the stop position holding current value; The trigger signal is connected to the reference voltage terminal of the trigger circuit (5) and voltage comparison circuit (4) that generates a trigger signal that drops from the rotation operating current value to the stop position holding current value before or after the excitation pulse stops. The reference voltage (VREF) is composed of a reference current reduction circuit (6) for reducing the current value from the rotation operating current value to the stop holding current value. Phase half step Of course, the complementary excitation (for example, by finely changing the excitation duty four-phase excitation and 5-phase excitation and go mode) in which it is able to fine division step drive by.
[0021]
This is an example in which the windings (A) to (E) of the stepping motor (1) in FIG. Output stage transistors (Tr1) to (Tr10) as switching means are (Tr1) (Tr2), (Tr3) (Tr4), (Tr5) (Tr6), (Tr7) (Tr8), (Tr9) (Tr10) The two sets are connected in series by one set, and the five sets are connected in parallel to form the drive control unit (2). The odd-numbered sides of the output stage transistors (Tr1) to (Tr10) constituting the drive control unit (2) are connected to the (+) side, and are connected to the even-numbered side (GND) side. The wire windings (A) to (E) are connected to a series of output stage transistors (Tr1) (Tr2), (Tr3) (Tr4), (Tr5) (Tr6), (Tr7) connected in series. It is connected to the connection part of (Tr8), (Tr9) and (Tr10). The output stage transistors (Tr1), (Tr2) to (Tr9), and (Tr10) are connected in parallel. (PD1) to (PD10) are connected in parallel to the output stage transistors (Tr1) to (Tr10). It is a diode. Further, a motor drive voltage (DV) for driving the stepping motor is always applied to the plus side of the drive control unit (2).
[0022]
The control circuit (3) is a pulse width modulation circuit (7) that performs pulse width modulation control of a DC current supplied from a DC power supply voltage, and is, for example, a transistor or FET that performs chopping control of the DC current by the pulse width modulation circuit (7). The configured chopper (8), the reactor (9) connected in series to the chopper (8), and the smoothing capacitor (C1) connected between the (+) side and the ground side (GED) of the control circuit (3) ) And a counter / excitation sequence generation circuit (10) for inputting a switching signal to the output stage transistors (Tr1) (Tr2) to (Tr9) (Tr10) of the drive control unit (2) according to the excitation sequence.
[0023]
A command pulse is input to the counter / excitation sequence generation circuit (10), and a counter (not shown) of the circuit (10) counts the command pulse to execute the excitation sequence. It has become.
[0024]
(R1) is a first sense resistor connected in series between the (−) side of the smoothing capacitor (C1) and the ground (GND), and (R2) is a second sense resistor connected to the output side of the drive circuit. It is connected in series between the (−) side of the capacitor (C1). Although not shown, the sense resistor may be only the second sense resistor (R2).
[0025]
One input terminal of the voltage comparison circuit (4) is connected to the output side of the drive control unit (2), and the other input terminal is connected to a reference current reduction circuit (6) described later, and its output The terminal is connected to the aforementioned pulse width modulation circuit (7). The operation of the voltage comparison circuit (4) compares the sum of the sense voltages of the first sense resistor (R1) and the second sense resistor (R2) with the reference voltage (VREF-H) or (VREF-L) to determine the current ( This is for controlling the pulse width modulation circuit (7) so that i1 + i2-i3) is constant. “When the sense resistor is only the second sense resistor (R2), the sense voltage generated by the current (i2−i3) flowing through the second sense resistor (R2) and the reference voltage (VREF-H) or (VREF-L ) Will be compared. "
[0026]
The trigger circuit (5) constituting the reference voltage changing unit (K) measures the period of the input command pulse (S), and after the command pulse (S) is input, the next command pulse (S) is predetermined. If the command pulse (S) is not input even after the time (Td) has elapsed, the command pulse (S) is judged as the last command pulse (S) in that step, and the rotation operating current value is reduced to the stop position holding current value. The trigger signal (Tg) is output to a reference voltage changing circuit (6) constituting a reference voltage changing unit (K) described later. Therefore, in this trigger circuit (5), the trigger signal output timing is after the excitation pulse stops. Of course, this method is not used, the command pulse is counted, and the trigger signal can be output when the predetermined number of pulses are input. In this case, the trigger signal is output when the predetermined number of pulses are input. If the trigger signal is output immediately before counting the predetermined number of command pulses, the trigger signal can be output immediately before the excitation pulse is stopped.
[0027]
Next, the operation of the drive circuit of FIG. 1 will be described. The current (i1) supplied from the DC power supply charges the capacitor (C1) through the chopper (8) and the reactor (9) and raises and lowers the motor drive voltage (DV). The current (i2) is an excitation current for driving the stepping motor generated by the discharge of the capacitor (C1). As shown by the broken line in the figure, the capacitor (C1), the drive control unit (2), the second sense resistor (R2) It circulates like that. The current (i3) is a reverse surplus current (i3) generated by the electromotive force of the motor. This surplus current (i3) circulates through the diodes (D1) to (D10) of the drive control unit (2) as a capacitor (C1), a second sense resistor (R2), and a drive control unit (2). As a result, a current (i2−i3) obtained by subtracting the surplus current (i3) from the excitation current (i2) flows through the second sense resistor (R2). The voltage comparison circuit (4) compares the sum (V1 + 2) of the sense voltages of the first and second sense resistors (R1, 2) with the reference voltage, and this current (i1 + i2-i3) becomes constant. Thus, pulse width modulation control is performed. “When the sense resistor is only the second sense resistor (R2), the sense voltage generated at the second sense resistor (R2) is (V2).”
[0028]
When the stepping motor (1) is operating, the command pulse (S) is input to the counter / excitation sequence generation circuit (10), and the counter / excitation sequence generation circuit (10) receives the command pulse to drive according to the predetermined excitation sequence. An excitation switching pulse (P) is output to the bases of the output stage transistors (Tr1) to (Tr10) of the control unit (4) to drive the stepping motor (1).
[0029]
At the same time, the command pulse (S) is also input to the trigger circuit (5) of the reference voltage changing unit (K), and the cycle of the command pulse (S) is measured in the trigger circuit (5). When the next command pulse (S) is not input to the trigger circuit (5) even after a predetermined time (Td) has elapsed since the last input command pulse (S) as shown in FIG. Determines that the command pulse (S) is the final command pulse (S) and outputs a trigger signal (Tg) to the reference voltage changing circuit (6).
[0030]
In the reference voltage changing circuit (6), upon receiving the trigger signal (Tg), the reference voltage (VREF) is set to a high reference voltage (VREF) for outputting the rotation operating current value necessary for driving the stepping motor (1). VREF-H) is changed to a low reference voltage (VREF-L) to output the stop position holding current value required to hold the stepping motor (1) in place, and the lowered low reference voltage (VREF-L) -L) is output.
[0031]
In the voltage comparison circuit (4), the sense voltage (V1 + 2) generated by the sense resistors (R1) and (R2) is reduced to “the sense voltage is (V2) when the sense resistor is only the sense resistor (R2)”. Compared to the lower reference voltage (VREF-L), the sense voltage (V1 + 2) or (V2) is sufficiently higher than the lower reference voltage (VREF-L). high. Therefore, the voltage comparison circuit (4) outputs a control signal to the pulse width modulation circuit (7) where the sense voltage (V1 + 2) "or (V2)" matches the low reference voltage (VREF-L). To do.
[0032]
The pulse width modulation circuit (7) receives the control signal from the voltage comparison circuit (4) and chopper-controls the chopper (8) to greatly reduce the current (i1). Since the current value charged in the smoothing capacitor (C1) is a low stop position holding current value necessary to hold the rotor (3a) of the stepping motor (1) in a predetermined position, it is discharged from the smoothing capacitor (C1). The exciting current (i2) is also a low current value, and the magnetic force generated between the stator (3b) and the rotor (3a) is also a weak force necessary to hold the rotor (3a) in a predetermined position.
[0033]
Normally, in the stepping motor (1), when stepping from one stop position to the next stop position, acceleration is performed from the stop position, and after reaching a predetermined speed, this speed is maintained for a certain period of time, and the next stop position is A so-called “trapezoidal drive” is performed in which the vehicle decelerates just before reaching. Even in this deceleration region, a large excitation current (i2) necessary for the rotational drive of the stepping motor (1) is applied to the windings (A) to (E), and the rotor (3a) and the stator (3b) A large magnetic force acts between them, and the rotor (3a) passes through the stop position due to the inertial force of the rotor and the load connected to the rotor (3a). In the conventional example, since the large excitation current (i2) necessary for the rotational drive of the stepping motor (1) was applied to the windings (A) to (E) even at this time, the large magnetic force passed the stop position. It works as a large “restoring force” that pulls the rotor (3a) back toward the stop position, and pulls the rotor (3a) back strongly. As a result, the number of reciprocations before and after the stop position increased, and the settling time (t) became longer as will be described later.
[0034]
On the other hand, if the magnetic force generated between the stator (3b) and the rotor (3a) is reduced by reducing the excitation current (i2) as described above, the force to pull the rotor (3a) back to a predetermined position is also weakened. The amount of undershoot that passes a predetermined position on the return path is significantly reduced. As a result, the number of reciprocations before and after the stop position is remarkably reduced, and the settling time (t) is shortened as will be described later. When the rotor (3a) is held at a predetermined position, the rotor (3a) is held at a predetermined position with a small stop position holding current value, and during this period, against the workpiece on the load connected to the rotor (3a) Necessary measurements.
[0035]
When the hold time for the predetermined position of the rotor (3a) elapses, the trigger signal (Tg) is output from the trigger circuit (5) to the reference voltage changing circuit (6), and the low reference voltage (VREF-L) is set to the high reference voltage ( VREF-H) and output to the voltage comparison circuit (4). The trigger signal (Tg) is generated by a timer. The generation timing is preferably earlier than the timing at which the first command pulse (S) is input to the counter / excitation sequence generation circuit (10). This is because when the command pulse (S) is input, the rotor (3a) starts rotating toward the next stop position, but if the excitation current (i2) is low at that time, sufficient acceleration cannot be obtained and the rising speed Because it becomes late.
[0036]
The switching from the high reference voltage (VREF-H) to the low reference voltage (VREF-L) may be performed instantaneously, but it may be performed slowly over time (Ts) or in several steps. You may divide it gradually and let it go down gradually. When the load is large, it is preferable to slow down or stepwise. In addition, switching from the reference voltage (VREF-H) to the lower reference voltage (VREF-L) may be performed at the same time as the trigger signal (Tg) is input, but depending on the state of the load and rotor (3a) You may delay by time (tm). FIG. 5 shows an example in which the switching of the reference voltage is delayed by (tm) time after the trigger signal (Tg) is input.
[0037]
Example 1; FIGS. 6 (a) and 6 (b) are comparative examples showing the relationship between a driving example (a) when stopped by a conventional method in a five-phase stepping motor and a driving example (b) when stopped by the method of the present invention. It is. The command pulse cycle (td) is measured by the trigger circuit, and when the cycle (td) becomes 1 ms or more, the reference voltage is lowered from the high reference voltage (VREF-H) to the low reference voltage (VREF-L), and excitation is performed. The current (i2) was about 40% of the current value during rotation. It can be seen that the conventional method takes a long time to settle, but the method of the present invention settles in a short time.
[0038]
Note that such a stop method is not only 4-phase excitation full-step drive and 4-5-phase excitation half-step drive, but also complementary excitation (for example, a method of finely changing the excitation duty of 4-phase excitation and 5-phase excitation). The present invention can be applied to minute division step driving.
[0039]
FIG. 2 is a circuit diagram of a second embodiment of the present invention. The counter / excitation sequence generation circuit (10) is connected to the pulse width modulation circuit (7), and the pulse width modulation circuit (7) is connected to the output stage transistors (Tr1) to (Tr4) of the drive control unit (2). Connected directly to the base. The stepping motor (1) is a two-phase motor. The motor drive power supply is directly connected to the input side of the winding (A) (-A) (B) (-B) of the stepping motor (1). The collectors of the output stage transistors (Tr1) to (Tr4) are connected to the output side of (A) (-A) (B) (-B), and a pair of output stage transistors (Tr1) (Tr2), (Tr3) (Tr4 ) Emitter current detection sense resistors (RA) (RB) for the phases (A) (-A) and (B) (-B) are connected between the emitter of) and ground (GND). The input side of this current detection sense resistor (RA) (RB) and the pair of voltage comparison circuits (4A) (4B) for (A) (-A), (B) (-B) phase ( +) And the sensing voltage (Va) (Vb) sensed by the sense resistor (RA) (RB) is input to the voltage comparison circuit (4A) (4B) from the input terminal (+). It has become.
[0040]
The command pulse (S) is input to the counter / excitation sequence generation circuit (10) and the trigger circuit (5). As described in the first embodiment, the final command pulse is detected ( Alternatively, the trigger pulse (Tg) is output to the circuit (6) for the next reference voltage change by counting the input command pulses. The reference voltage changing circuit (6) is connected to the reference voltage terminal (-) of the voltage comparison circuit (4A) (4B), and the first voltage change circuit (6) is input by the trigger signal (Tg) output from the trigger circuit (5). As described in detail in the embodiment, the reference voltage (VREF) is reduced, and the drive excitation current supplied directly from the motor drive power source to the windings (A) (-A), (B) (-B) is reduced ( Rotation operating current value → stop position holding current value) are performed individually. Then, after the elapse of a predetermined time, (stop position holding current value → rotation operating current value) is individually performed. The timing of raising and lowering the drive excitation current is as in the first embodiment.
[0041]
Example 2; FIGS. 7 (a) and 7 (b) show a driving example (a) when stopped by a conventional method in a two-phase stepping motor and a driving example (b) when stopped by the method “circuit of FIG. 7” of the present invention. It is a comparative example which shows the relationship. As in “Example 1,” the period (td) of the command pulse is measured by the trigger circuit, and when the period (td) becomes 1 ms or more, the reference voltage is changed from a high reference voltage (VREF-H) to a low reference voltage ( VREF-L), and the excitation current (i2) was set to about 50% of the current value during rotation. It can be seen that the conventional method takes a long time to settle, but the method of the present invention settles in a short time.
[0042]
In addition, such a stop method is not only four-phase excitation full-step drive and 4-5-phase excitation half-step drive, but also complementary excitation (for example, a method of finely changing the excitation duty of 4-phase excitation and 5-phase excitation). The present invention can be applied to minute division step driving.
[0043]
FIG. 3 is a circuit diagram of a third embodiment of the present invention. The counter / excitation sequence generation circuit (10) is connected to the frequency modulation circuit (7a), and there is no trigger circuit (5). From the counter and excitation sequence generation circuit (10) to the reference voltage reduction circuit (6) 2 and the point that the outputs of the pair of voltage comparison circuits (4A) and (4B) are connected to the frequency modulation circuit (7a) are different from the second embodiment of FIG. Other than the above, the second embodiment is the same as the second embodiment shown in FIG. The frequency modulation circuit (7a) can vary the on-time while the off-time of the output stage transistor is constant, and can perform variable = frequency modulation of one cycle.
[0044]
When the command pulse (S) is input to the counter / excitation sequence generation circuit (10), the number of input pulses is counted here, and the number of pulses with a moving angle of 7.2 ° is input as in the second embodiment. Lowering the reference voltage (VREF), raising and lowering the drive excitation current directly supplied to the windings (A) (-A), (B) (-B) from the motor drive power supply (rotation operating current value → stop position) Holding current value) is performed individually. Then, after a predetermined time has elapsed, (stop position holding current value → rotation operating current value) is individually performed. The timing of raising and lowering the drive excitation current is as in the first embodiment. In this case, since the command pulse (S) input to the counter / excitation sequence generation circuit (10) is counted, the reference voltage is input simultaneously with or before the input of the number of pulses with a moving angle of 7.2 °. It is also possible to lower (VREF). It is also possible to decrease the reference voltage (VREF) instantaneously, over a certain period of time, or stepwise.
[0045]
Embodiment 3; FIGS. 8 (a) and 8 (b) show a driving example (a) when stopping by a conventional method in a two-phase stepping motor and a driving example (b) when stopping by the method “circuit of FIG. 3” of the present invention. It is a comparative example which shows the relationship. The counter / excitation sequence generation circuit is input with a pulse number of 72 ° (here, 80 pulses), and after 1 ms, the reference voltage is changed from a high reference voltage (VREF-H) to a low reference voltage (VREF-L). The excitation current (i2) was set to about 50% of the current value during rotation. It can be seen that the conventional method takes a long time to settle, but the method of the present invention settles in a short time.
[0046]
In addition, such a stop method is not only four-phase excitation full-step drive and 4-5-phase excitation half-step drive, but also complementary excitation (for example, a method of finely changing the excitation duty of 4-phase excitation and 5-phase excitation). The present invention can be applied to micro divided step driving or micro step driving of a two-phase stepping motor that performs step driving by finely dividing one step.
[0047]
【The invention's effect】
In the present invention, when the stepping motor is stopped, the stepping motor is rotated during the settling time when the stepping motor is decelerating at the same time as the command pulse input stop or during the deceleration of the stepping motor before or after the stop position after that. Since the exciting current value is reduced from the current value to the stop position holding current value, the restoring force of the rotor against the stator during the settling time is greatly reduced, and the damping vibration that repeats overshoot and downshoot converges in a short time and stops at the stop position. The rotor (3a) of the stepping motor stops at a predetermined position at the holding current value. As a result, the cycle time of the apparatus can be shortened and the work efficiency can be greatly improved. In addition, the stop position holding current value can be reduced from the rotation operating current value over time or stepwise, and further, with respect to a timing load that reduces the stop position holding current value from the rotation operating current value. Optimal conditions can be selected. Also, after the excitation current has been reduced for a certain period of time, the excitation current is returned to the rotation operating current value before the next step command pulse is input, so that the pulse motor is sufficient when the next step command pulse is input. Therefore, a smooth rising acceleration can be obtained.
[Brief description of the drawings]
FIG. 1 is a circuit diagram of a first embodiment of the present invention.
FIG. 2 is a circuit diagram of a second embodiment of the present invention.
FIG. 3 is a circuit diagram of a third embodiment of the present invention.
FIG. 4 is a schematic explanatory diagram of a stepping motor to which the present invention is applied.
FIG. 5 is a comparative time chart of the present invention and a conventional example.
FIG. 6 is a comparison graph of settling time between the present invention (first embodiment) and a conventional example in a five-phase stepping motor.
FIG. 7 is a comparison graph of settling time between the present invention (second embodiment) and a conventional example in a two-phase stepping motor.
FIG. 8 is a comparison graph of settling time between the present invention (third embodiment) and a conventional example in a two-phase stepping motor.
[Explanation of symbols]
(1) Stepping motor
(2) Drive controller
(P) Excitation switching pulse
(i2) Excitation current
(t) Settling time

Claims (6)

In the method of driving the stepping motor step by stepping the excitation current to the stepping motor and inputting the excitation switching pulse of the stepping motor to the drive control unit according to a predetermined excitation sequence,
Simultaneously with the stop of command pulse input to generate the excitation sequence, or
During deceleration of the previous stepping motor or
Stop position for generating the torque required for stopping the stepping motor from the rotation operating current value for generating the torque required for the rotation of the stepping motor within the settling time in which the damping vibration is generated in the stepping motor before and after the subsequent stop position lowered the or stepwise the excitation current value over a predetermined time period to the holding current value, after settling also maintained the stop position holding current value driving method of a stepping motor according to claim Rukoto. In the method of driving the stepping motor step by stepping the excitation current to the stepping motor and inputting the excitation switching pulse of the stepping motor to the drive control unit according to a predetermined excitation sequence,
Simultaneously with the stop of command pulse input to generate the excitation sequence, or
During deceleration of the previous stepping motor or
Stop position for generating the torque required for stopping the stepping motor from the rotation operating current value for generating the torque required for the rotation of the stepping motor within the settling time in which the damping vibration is generated in the stepping motor before and after the subsequent stop position Decrease the exciting current value over a predetermined time or stepwise to the holding current value, hold the stop position holding current value even after settling, and then change it to the rotation operating current value before the input timing of the next first command pulse. A stepping motor driving method, wherein the stepping motor is returned. (a)   A control circuit for stepping driving the stepping motor according to the excitation sequence by inputting an excitation switching pulse to the drive control unit of the stepping motor based on the input command pulse;
(b)   Stop position required to hold the stepping motor at the stop position based on the rotational operating current value required for driving the stepping motor at the same time as the command pulse input stop or before or after Reduced reference voltage to reduce to holding current value (VREF-L) The reference voltage up to is output over a predetermined time or stepwise, and after holding the stop position holding current value, it is raised to raise the stop position holding current value to the rotation operating current value Reference voltage (VREF-H) A reference voltage changing unit that outputs
(c) Sense voltage generated by current for driving the stepping motor, and the reference voltage (VREF-H) Or (VREF-L) Or, compared with the reference voltage in the middle of the both, after reducing the excitation current from the rotation operating current value to the stop position holding current value over a predetermined time or stepwise, after holding the stop position holding current value, Increased reference voltage to raise the stop position holding current value to the rotation operating current value (VREF-H) And a voltage comparison circuit that outputs a stepping motor drive circuit. (a) a control circuit for stepping driving the stepping motor according to the excitation sequence by inputting an excitation switching pulse to the drive control unit of the stepping motor based on the input command pulse;
(b) Necessary to hold the stepping motor at the stop position from the rotation operating current value necessary for driving the stepping motor at the same time as the command pulse input stop or before or after it The reference voltage up to the reduced reference voltage (VREF-L) for reducing to a stable stop position holding current value is output over a predetermined time or in stages, and the stop position holding current value is maintained even after settling After that, a reference voltage changing unit that outputs a raised reference voltage (VREF-H) for raising the stop position holding current value to the rotation operating current value,
(c) Compare the sense voltage generated by the current for driving the stepping motor with the reference voltage (VREF-H) or (VREF-L) or a reference voltage in the middle of both, and take a predetermined time. Alternatively , the excitation current is gradually reduced from the rotation operating current value to the stop position holding current value, the stop position holding current value is held even after settling, and then the stop position holding current value before the input timing of the next first command pulse. A stepping motor drive circuit comprising: a voltage comparison circuit that outputs a raised reference voltage (VREF-H) for raising the rotation operating current value from 1 to 2. Reference voltage changing section (K) Is the input command pulse (S) Command cycle (S) The command pulse when the period of (S) Is the final command pulse and the reference voltage (VREF-L) The stepping motor drive circuit according to claim 3 or 4, wherein the stepping motor drive circuit according to claim 3 is output. The reference voltage changing unit counts the number of input command pulses, and when the count reaches a predetermined number, the reference voltage (VREF-L) The stepping motor drive circuit according to claim 3 or 4, wherein the stepping motor drive circuit according to claim 3 is output.

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