FR2471077A1 - REAL-TIME DETECTION WITH DYNAMIC ROTATION DETECTION FOR STEP-BY-STEP MOTOR - Google Patents

Abstract

THE PRESENT INVENTION RELATES TO A CONTROL DEVICE FOR A STEP-BY-STEP MOTOR. THIS DEVICE IS CHARACTERIZED IN THAT IT INCLUDES MEANS TO DETECT THE PASSAGE OF CURRENT BY A RELATIVE MAXIMUM AND MEANS TO INCREASE THE MINIMUM DURATION T OF THE CONTROL PULSE BY A VALUE T. DETECTION OF THE PASSAGE BY A MAXIMUM IS DONE BY A DEVICE WHICH GENERATES AN INTERRUPTED DETECTION PULSE, FOR EXAMPLE, SIMULTANEOUSLY WITH THE MINIMUM CONTROL PULSE T.

Description

24,710 77

  The present invention relates to a control device of a

  step motor, supplying electrical control pulses to the bobbin

  motor, and comprising a device for detecting the variation of the current flowing in the motor winding during each control pulse, and a device for adapting the duration of each control pulse, as a function of

  resistance torque exerted on this motor.

  In multiple applications of micromotors, particularly in the field of watchmaking, the energy source used for the training of

  motors consists of an electric battery.

  The present invention proposes to reduce the electrical energy consumption of the engine and, consequently, to make possible the use of batteries of very small size and / or to extend the life of the source. In addition, it proposes to increase the reliability of

  of the motor, real-time servo-control with a dy-

of its rotation.

  Control pulses for motors of the type mentioned above must be

  enough time for the rotor to overcome the torque

  standing and taking a step. This condition is fulfilled when the current

  pouring the motor winding passes through a relative maximum.

  Consequently, the control device according to the invention is

  characterized in that the detection device comprises means for detecting

  the passage of the motor current by a relative maximum, and means for increasing

  ter the minimum duration T0 of the pulse of a predetermined value AT.

  According to an alternative embodiment of the present invention, the

  positive control is characterized in that the detection device com-

  takes means to detect the passage of the motor current by a maximum relative to

  tif, and means for interrupting the control pulse at the end of an inter-

  time interval AS T, after the passage of the current by said relative maximum.

  According to a preferred embodiment, the detection device comprises a comparator which changes state when the current decreases after passing through said relative maximum. It also includes a unit of

  memory for storing the peak value of the current, and means for comparing

  continuously adjust the instantaneous value of the current to this peak value.

  To ensure the detection of current flow by a maximum relative to

  tif, the detection device preferably comprises means for generating

  a detection pulse and means for interrupting the pulse of detec--

  at the same time as the minimum motor control pulse TO, or after the current has been passed to the relative maximum. It also comprises means for delaying the detection pulse with respect to the control pulse of the

  motor, and means for interrupting the detection pulse when a maximum

  it 2. relative mum is not detected within a specified time interval. According to a particular embodiment, the value AT, which prolongs the control pulse

  of the motor after the passage of the current by said relative maximum, may be

  be of several intervals at Ti, for example equal, so that AT is an integer multiple of ATi.

  The present invention will be better understood with reference to the description

  FIG. 1 is a graphic representation of the shape of the current, when the motor is rotating by one step, FIG. 2 is a graphical representation of the shape of the current when the motor has not rotated completely or is blocked, FIG. 3 partially represents a block diagram of the control device according to the invention,

  Figure 4 graphically represents the shape of the compression pulse.

  mande and the corresponding detection pulse, for a first embodiment of the invention,

  Figure 5 graphically represents the shape of the compression pulse.

  and the corresponding detection pulse, for a second embodiment of the invention. FIG. 6 is a graphical view showing the current, the sense pulse, and the control pulse for said second embodiment, in FIG. the case where the engine normally rotates by one step (T: represents subsequently the effective duration

the detection pulse).

  * Figure 7 represents successively the shape of the current, that of

  the detection pulse and that of the control pulse for said second

  in the case where the motor rotates with difficulty, FIG. 8 represents the shape of the current, that of the detection pulse and that of the control pulse, when the motor is blocked, and FIG. 9 represents, successively and by way of comparison, the shape of the motor control pulses in the case of the first variant, that of the

  motor control pulses in the case of the second variant, that of the

  control pulse in the case of a multiple pulse servo, and that

  of the control pulse in the absence of the servo according to the invention.

  The detection of the rotation of a stepper motor, as it is

  obtained by the control device of the present invention, is effectively

  dynamic detection as it occurs during motor rotation.

  Figs. 1 and 2 graphically represent the intensity of the current in the bobbin

  stroke of the motor as a function of time. When the motor is running normally, this intensity passes through a relative maximum, called Imax or I peak, to decrease and go through a minimum. In the case where the motor is blocked, the intensity

-2 47 10 7 7

  continually approaching the peak value asymptotically.

  The block diagram of FIG. 3 represents, by way of example, an embodiment of the control device according to the invention. A block 10 provides control and detection of the motor current. In particular, the power supply of the motor is preferably by a transistor bridge known per se. The output of the block 10 is connected to a current-voltage converter 11 whose output is connected directly to one of the inputs of a comparator 12 and indirectly via a voltage storage block. peak 13 at the other input of the comparator 12. The storage block 13 comprises a capacitor 14 connected in series with a diode 15, so that this capacitor

  charge until the current reaches its maximum, that is to say its

  their peak, which allows to put in memory this value. The reset of the storage device is provided by a device 16 known per se. The

  comparator output is connected to a pulse generator which, in the example

  represented, allows to provide two pulses of different duration. Com-

  paratrix 12 is connected to one of the inputs of a NAND gate 17, whose other input is connected to a frequency divider 18, connected to an oscillator, by

  example, a crystal oscillator 19. The frequency divider 18 can, for example,

  xample provide signals at the frequency of one hundred and twenty-eight Hz brought to the

  The input of the NAND gate 17 and the sixty-four Hz signals to one of the inputs of a NAND gate 19. The other input of the NAND gate is connected to the output of the NAND gate. AND via an inverter 20. In this way, we find, at the output of the NONOU gate, pulses of 3.9 ms

or 7.8 ms.

  Fig. 4 represents the shape of the motor control pulse and

  that of the detection pulse which correspond to the device described in

  FIG. 3. The control pulse, represented graphically by a voltage as a function of time, has a minimum duration T0 which can be extended

  once with a duration A \ T, for example equal to TO if a relative maximum of the cou-

  rant is not detected during the TO interval. The detection pulse is preferably delayed by a duration TA with respect to the control pulse, and

  terminates simultaneously with the command pulse TO-

  This adaptation of the duration of the control pulse, as a function of the resisting torque exerted on the motor, is obtained by means of the comparator of FIG. 3 that changes state when the current decreases after going through a

relative maximum.

  The operating program of the device described above is

  38 rolls as follows: 4. Beginning of the control pulse I. ,, Time delay TA before the detection pulse Start of the detection pulse The comparator yes + yes has it changed? control impulse T impulse T prolonged control control | after T J

  According to another embodiment of the device described, liimpul-

  sion can have an incremental variation in its duration. With reference to FIG. 5, which graphically represents the control pulse and the corresponding detection pulse, it can be seen that the motor control pulse can have a minimum duration T 0 which stops at the moment when the current exceeds its current.

  relative maximum, that is to say at the moment of the change of state of the comparator.

  However, depending on the resistor-applied torque, this minimum pulse can be extended by one or more time intervals & Ti, for example AT1, T1 + ZT2, T1 + AT2 + AT3, S T1 + / T2 + 4T3 + iT4 or / TT1 + T2 + AT3 + AT4 + / T5. The intervals A Ti may have a

  any duration, but are preferably equal, so that the minimum pulse

  T0, which corresponds to the duration of the minimum pulse for a motor

  normally, can be extended by an integer multiple of intervals / Ti

elementary.

  The operating program of the device described proceeds as follows: 5. When the motor is running normally, the curves of the current in the winding and the shape of the control and detection pulses correspond

  respectively to the graphs in fig. 6. A TA timer defines the

  purpose of the detection pulse. This impulse is prolonged until the

  current i begins to decrease after passing through its relative or va-

  their crest. At this time, the comparator changes state. The minimum duration T0 of the motor control pulse is extended by one increment, c T1, so

  that the total pulse has a duration T0 + d Tl.

  In the case where the motor rotates with difficulty, the aforementioned curves have the appearance represented by the graphs of FIG. 7. As before,

  a delay TA defines the start of the detection pulse. This impulse

  will be longer, because the transition to the maximum current, which

  39 the change of state of the comparator, is delayed by a resisting torque.

  In the example shown, the control pulse has a duration T.sub.t + 4.sub.Ti or T.sub.t + T.sub.t + T.sub.t + TnT.sub.3 + T.sub.4, o.sub.T represents the minimum pulse, in

  the case where the engine is running normally.

  In fact, the duration of the detection pulse is TM = TA + TB. This duration corresponds to a pulse stopping within the third increment.

  C Ti. The control pulse is prolonged until the end of the third

  crement and we add, for safety, a fourth increment T4.

  In the case of FIG. 8, the motor is blocked. The pulse of detection

  tion is timed in such a way that it is triggered after a

  TA, and its end after a time TA + TB max. The control pulse is stopped

  at the same time as this detection pulse and has a total duration

T0 + 5 Ti.

  By way of example, TA = 2 s; TO = i3 s; Ti - I s.

128 128 128

  So that the control pulse can take the following values:

  vantes: TO + Ti = s. TO + 2 LSTi = 1-2a '

  TO +3 Ti = 6-8-s.TO + 4 itsTi = 7 s.

128 128

T0 + 3.t4.Ti 67Ws T0 + T '7

T0 + 5 È Ti = 8 s.

  FIG. 9 represents, by way of example, the shape of the control pulses of the motor, in the case where it normally turns with difficulty,

  in the case of multi-pulse servoing and in the case of a

  without servo. TS is the duration of the stabilization of the

  tor, which is here of the order of 15.6 ms.

  The table below compares the experimental results

  obtained, corresponding to the graphs in fig. 9.

  Case I: corresponds to the graph of fig. 4.

  Case II: corresponds to the graph of fig. 5.

  Case III: corresponds to a multiple pulse servo.

  Case IV: corresponds to a command without-servo.

  This table makes it possible to understand that the actual consumption is

  equal to half that of a device without servocontrol when the engine Engine Case I Case II Case III Case IV runs normally 3.9 ms 3.9 ms 3.9 ms 7.8 ms hardly 7.8 ms 4.9 / 5.9 / 6.8 / 7.8 ms> 11.7 ms 7.8 ms not at all 7.8 ms 7.8 ms> 11.7 ms 7.8 ms Duration of control pulses 7.

  turns normally. It is much lower than that of a system to assert

  multi-pulse operation in difficult cases. Case II, which illustrates

  the second embodiment described in detail with reference to FIG. 5, is more flexible thanks to its five possible pulse durations and saves more energy in difficult cases. -

  In the two versions described, the energy saving obtained does not affect

  in no way the reliability of the operation of the system, which is essentially the

  same as that of known systems.

  Other experiments have been carried out on the device of the invention.

  tion. In particular, the accelerated forward drive with servo.

  The table below summarizes the numerical results obtained.

  As in the real-time servo, there is only one pulse per engine step. Fast forward can be as fast as in

  non-controlled systems, which is not the case for pulse systems.

multiple sions.

  In addition, there is also energy saving during the

  accelerated forward movement, already registered for normal walking.

  Case I Case II Case III Case I V Minimum total time 23.4 23.4> 42.9 23.4 for one step (in ms) Maximum frequency 42 42 <23 42 motor (step / second)

REVJENDICATIONS

  l. Device for controlling a stepper motor, providing

  electrical control pulses to the motor winding, comprising a

  detection of the variation of the current flowing in the winding of the motor.

  each control pulse, and a device for adapting the

  each of the control pulses of the motor, as a function of the resistive torque exerted on the motor, characterized in that the detection device comprises means for detecting the passage of the motor current by a relative maximum, and means for increasing the minimum duration To the command pulse,

of a predetermined AT value.

  2. Device according to claim 1, characterized in that the arrangement

  detection system comprises means for generating a detection pulse.

  and means for interrupting the detection pulse simultaneously with

  the minimum command pulse TO.

  3. Device according to claim 2, characterized in that the arrangement

  detection system comprises means for delaying the detection pulse

  relative to the motor control pulse.

  4. Device according to claim 2, characterized in that it comprises means for interrupting the control pulse T (+ AT, when a maximum

  relative current is not detected during the detection pulse.

  5. Device according to claim 1, characterized in that the arrangement

  detection system includes a comparator which changes state when the current

  decreases after passing through a maximum.

  6. Device according to claim 1, characterized in that the arrangement

  detection system comprises a storage unit for storing the peak value of the current and means for comparing the instantaneous value of the current with the peak value, for at least a fraction of each control pulse

of the motor.

  7. Device for controlling a stepper motor, providing

  - electrical control pulses to the motor winding, comprising a

  detection of the variation of the current passing through the winding of the

  each control pulse, and a device for adapting the

  each of the control pulses of the motor, as a function of the resistive torque exerted on the motor, characterized in that the detection device comprises means for detecting the passage of the motor current by a relative maximum, and means for interrupting the pulse after an interval

  time T, after the passage of the current by said relative maximum.

  8. Device according to claim 7, characterized in that the arrangement

  detection system comprises means for generating a detection pulse.

  39 and means for interrupting the detection pulse after the passage 9.

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  current by said relative maximum.

  9. Device according to claim 7, characterized in that the arrangement

  detection system comprises means for delaying the detection pulse

  relative to the motor control pulse.

  10. Device according to claim 7, characterized in that it comprises means for interrupting the detection pulse, when a relative maximum current is not detected for a time TB; determined from the beginning

of this impulse.

  he. Device according to claim 7, characterized in that it comprises means for interrupting the control pulse, when a relative maximum

  current is not detected during the duration of the detection pulse.

  12. Device according to claim 11, characterized in that it comprises means for extending the control pulse of at least one increment A Ti

  of predetermined duration, after the duration of the detection pulse.

  13. Device according to claim 7, characterized in that the arrangement

  detection system includes a comparator which changes state when the current

  decreases after passing through a relative maximum.

  14. Device according to claim 7, characterized in that the arrangement

  detection system comprises a storage unit for storing the peak value of the current, and means for comparing the instantaneous value of the current with the peak value, for at least a fraction of each control pulse

22 of the engine.