EP0062273B1 - Procédé pour asservir un moteur pas à pas - Google Patents

Procédé pour asservir un moteur pas à pas Download PDF

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Publication number
EP0062273B1
EP0062273B1 EP82102626A EP82102626A EP0062273B1 EP 0062273 B1 EP0062273 B1 EP 0062273B1 EP 82102626 A EP82102626 A EP 82102626A EP 82102626 A EP82102626 A EP 82102626A EP 0062273 B1 EP0062273 B1 EP 0062273B1
Authority
EP
European Patent Office
Prior art keywords
duration
pulse
pulses
motor
control
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired
Application number
EP82102626A
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German (de)
English (en)
French (fr)
Other versions
EP0062273A1 (fr
Inventor
Mai Tu Xuan
Michel Grosjean
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Omega SA
Original Assignee
Omega SA
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Filing date
Publication date
Application filed by Omega SA filed Critical Omega SA
Publication of EP0062273A1 publication Critical patent/EP0062273A1/fr
Application granted granted Critical
Publication of EP0062273B1 publication Critical patent/EP0062273B1/fr
Expired legal-status Critical Current

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    • G—PHYSICS
    • G04—HOROLOGY
    • G04C—ELECTROMECHANICAL CLOCKS OR WATCHES
    • G04C3/00—Electromechanical clocks or watches independent of other time-pieces and in which the movement is maintained by electric means
    • G04C3/14—Electromechanical clocks or watches independent of other time-pieces and in which the movement is maintained by electric means incorporating a stepping motor
    • G04C3/143—Means to reduce power consumption by reducing pulse width or amplitude and related problems, e.g. detection of unwanted or missing step

Definitions

  • the present invention relates to a method for controlling a single-phase stepping motor supplied by a train of bipolar pulses with the load presented by the mechanism of a timepiece. It offers various improvements to the servo system which has been described in patent application EP-A-0 022 270.
  • a supply device making it possible to detect the position of the rotor of a stepping motor with respect to the polarity of the driving pulses and to send to said motor a train of long pulses if this polarity is judged to be incorrect.
  • the rotor does not advance one step after having sent a motor pulse of correct polarity, it will receive a predetermined period of time later (a second for example) a new pulse of incorrect polarity and it is from this moment that the system comes into operation, the correction or the catch-up taking place by sending to the motor two long-lasting close pulses followed by a train of very large pulses.
  • the system proposed in the cited application envisages only two types of pulses: narrow pulses when the torque exerted on the motor is low and broad pulses when this torque has increased beyond a certain limit .
  • this couple can take very diverse values due, for example, to one of the following events or the combination of some of these events: change of calendar, friction in the bearings and their wear, aging oils, drop in temperature, influence of an external magnetic field, linear or angular shocks, manufacturing tolerances, etc.
  • Figure 1 of this presentation shows schematically a motor whose poles of the stator are separated by air gaps 1.
  • all the flux ⁇ ab from the magnetized rotor 2 passes through the core of the coil 3 to produce at the terminals of this coil a induced voltage Ui when the rotor is moving.
  • the air-gap motor receives a pulse of correct polarity, the voltage Ui collected across its coil will be of a sufficiently high amplitude to decide that it must continue to supply it with pulses of small width. It is a different matter if the system described in the cited application is applied to an engine with saturable zones.
  • Figure 2 schematically shows such a motor where the stator poles are joined by isthmus 4. In this case, we see that the flux created by the magnet is divided into a flux ⁇ f passing through the isthmus and into a flux ⁇ 1> ab passing through the core of the coil.
  • This method although applied to a motor with saturable isthmus, does not provide a system which maintains the saturation of the isthmus during the measurement of the induced voltage and this in order to obtain a signal of large amplitude, as is the case. case in the present invention. This method also does not indicate how it should go about detecting a comfortable amplitude voltage when the duration of the control pulse increases.
  • the pulses referenced n - 2 to n + 4 are the control pulses received by the motor coil. The start of each of them is separated by a constant period of time, for example one second, which advances the seconds hand of the watch in steps of one second.
  • This clock signal comes from the output of a chain of frequency dividers which is itself supplied by a time base oscillator according to an arrangement which is now well known.
  • two very large catch-up pulses T are sent to the motor to catch up with this delay at a short time after the end of the pulse n.
  • the first catch-up pulse is in the same direction as the n -1 pulse and the second in the opposite direction so that the large width pulses T a are somehow substituted to the control pulses n - 1 and n of width Tl which were not able to advance the rotor of the motor.
  • the duration T a is naturally chosen to be long enough to cause the rotor to progress under the most unfavorable load conditions.
  • the process which has just been described shows that the duration of the control pulses is adapted to the load imposed on the motor by successive rising levels when the load increases.
  • the process therefore makes it possible to save energy and this in even greater proportions than if only two types of pulses were available, as provided for in the cited application.
  • six different pulses have been chosen whose motor durations range from 3 to 9 ms in successive levels of 0.5 ms for the first three, 1.5 ms for the fourth and fifth and 2 ms for the sixth.
  • the duration of the catch-up pulse was chosen at 8 ms. This will appear in more detail when the diagram shown in Figure 12 is explained.
  • FIG. 4 presents a second variant of the method according to the invention where, after sending two catch-up pulses, the motor is still supplied with a pair of pulses of the same duration as that which existed before the correction.
  • the control pulses n + 1 and n + 2 have the same duration T, as that of the pulses n - 1 and n.
  • binding events have a fleeting nature such that they disappear very quickly.
  • An attempt to refuel the motor a second time with pulses whose duration did not advance its rotor a first time can be fruitful because, if the attempt succeeds, an increase in consumption will have been avoided due to an unnecessary widening of the pulses control. If the attempt is unsuccessful, the motor is supplied with pulses of longer duration T 2 after having sent the two catch-up pulses.
  • This second variant is not limited to the renewed sending of a single pair of pulses of the same duration TI and it will be understood that means can be used to continue supplying the motor with the pulses T, as long as a given number of catch-up pulses will not have been counted in a predetermined interval. For example, it can be decided that if the rotor has missed its step four times for 60 seconds, these missed steps having been followed by four pulses catch-up, then the motor is supplied with pulses of duration T2.
  • FIG. 5 shows the evolution of the positioning torque Ca and of the mutual torque Cab as found in a stepping motor.
  • the angular positions S ′ 2 , S, and S 2 are the stable equilibrium positions of the rotor and the positions l ′ 1 and I 1 are the unstable equilibrium positions of this rotor. Normally if the rotor takes its step in response to a positive impulse, it goes from position S, to position S 2 . In the particular case which has just been mentioned, it is therefore possible that the rotor stops in position 11 which represents only a half-step stroke. Although this position is unstable, it is possible that the rotor is maintained there by the frictions which act on it.
  • the rotor will either reverse into position SI, or advance into position S 2 .
  • the new control pulse will have an incorrect polarity and the catch-up pulses T a will make up for the two lost steps.
  • the rotor will have caught up with the lost step itself and no catching pulse will be sent to it.
  • the situation presents itself differently if the rotor remains fixed in position I 1 when the next pulse occurs. Indeed, this next negative impulse develops the mutual torque -Cab which happens to be in the same direction as the negative positioning torque -Ca.
  • FIG. 6 shows an arrangement which overcomes the drawback cited by proposing, according to a particular embodiment of the invention, to send to the motor coil a predetermined period of time after the end of the duration control pulse T t , a safety pulse of duration T S.
  • a pulse of very short duration will suffice to send it either to S 1 or to S 2 .
  • a negative safety pulse will bring it back to S, and the next normal command pulse will show up as incorrect, which will trigger the two catch-up pulses as explained above.
  • a positive safety pulse will bring the rotor to S 2 ; in this case, the next command pulse will appear to be correct and no catch-up will take place.
  • a negative safety pulse will be preferred since it takes less energy to bring the rotor from position 1 1 to position S, than from position I 1 to position S 2 .
  • a duration between 0.2 and 0.5 ms is chosen for T s and for the period of time separating the end of the control pulse from the safety pulse a duration of the order of 50 ms.
  • FIG. 7 shows the device used to obtain a very comfortable voltage Ui even if the motor is of the type with saturable zones.
  • This device comprises a bridge with four branches, each of which comprises a switch, the first diagonal of the bridge receiving a continuous power source and the second comprising the motor coil.
  • a resistor is arranged in series with this coil and is bridged by a switching device. Means are put into action to open said device when it is necessary to detect the rotation or the absence of rotation of the rotor.
  • FIG. 7 shows a resistor 40 connected in series with the coil 15 of the motor, a resistor which can be short-circuited when the switch 35 is closed.
  • the switch control sequence is established according to the table below for a positive pulse:
  • transistors play the role of switches. They receive their signals from a conventional shaping circuit.
  • U B is the only driving voltage useful to drive the rotor.
  • the resistor 40 is connected in series with the coil 15, the switch 35 is open. It is the period of measurement intended to take at the terminals of the coil the induced voltage Ui developed by the motor.
  • FIG. 9 represents the behavior of the motor during the measurement period T X.
  • the control voltage U is applied to the terminals 41 and 42 of the circuit which comprises the coil 3 and the resistor 40 connected in series.
  • the value of the resistance 40 is chosen so as to generate in the coil 3 a current l SAT which, in turn, will produce a flux ⁇ b sufficient to saturate the isthms 4 of the stator.
  • the flux ⁇ b produces across the coil an induced voltage where N b represents the number of turns of the coil.
  • FIG. 8 shows that at a predetermined time t x of the period T x , the voltage Ui, shown in dashed lines, is of large amplitude as a result of which the motor will continue to be supplied with the same width control pulses T n .
  • the induced voltage Ui will be measured in an interval T Ui included in the period T x , interval which can embrace, for example, the last two thirds of the period T X.
  • the shortest TRB period a duration of 3 ms and for the period T x a duration of 1 ms while the value of the resistance 40 is 15 kQ for a resistance of the coil. 3 kQ.
  • FIG. 10 illustrates the phenomenon which has just been explained and shows how the amplitude of the voltage Ui decreases when the pulse U B lengthens. It can be seen that the driving pulses of increasing duration U B1 , U B2 and U B3 correspond respectively to the induced voltages Ui 1 , Ui 2 and Ui 3 , the maximum of said voltages being located on an envelope whose shape is representative of the coupling factor. Cab / i, down to speed. For the U 84 pulse, the figure shows that no induced voltage is detected.
  • Figure 11 shows how we proceed according to a particular embodiment of the invention to overcome the drawback mentioned.
  • the control pulse U is composed of two driving pulses U B and U c separated by a period T x during which the induced voltage is measured according to the method which has been explained above.
  • the width T t of the control pulse U is greater than the duration T n from which the amplitude of the induced voltage Ui would be insufficient or zero, said induced voltage Ui is measured during an interval T Ui included in the period T x immediately preceding the end of the period T n .
  • the window method is also perfectly suitable if it is applied to a motor with air gaps (see Figure 1) where the phenomenon of extinction of the induced voltage also exists when the control pulse lengthens.
  • the coil of the motor with an open circuit can also be placed, as recommended in application EP-A-0 022 270, when it is desired to measure the induced voltage. If this is the case, the resistor 40 and the switch 35 shown in FIG. 7 will be deleted and all the switches 31 to 34 will be opened during the duration measurement window T X. It must also be said that if the open circuit voltage Ui is measured in the air gap motor, the graph in FIG. 11 remains the same except for the current i which is canceled out during the period T X.
  • FIG. 12 illustrates in an exemplary manner how the width of the control pulse is adapted to the load imposed on the motor and when the induced voltage is measured.
  • Figure 12 also shows the catch-up pulse of duration T, the width of which is chosen at 8 ms.
  • the voltage Ui is compared with a reference voltage in a comparator. If Ui is greater than said reference, a pulse of correct polarity has been sent to the motor and no signal appears at the output of the comparator. The control circuit continues to send pulses of the same duration. If, on the contrary, Ui is smaller than the reference, an incorrect polarity pulse has been sent to the motor and a signal appears at the output of the comparator which forces the control circuit to send two catching pulses then a control pulse train, as explained above.

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  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Control Of Stepping Motors (AREA)
  • Electromechanical Clocks (AREA)
EP82102626A 1981-03-31 1982-03-29 Procédé pour asservir un moteur pas à pas Expired EP0062273B1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
CH216581A CH644983GA3 (enrdf_load_stackoverflow) 1981-03-31 1981-03-31
CH2165/81 1981-03-31

Publications (2)

Publication Number Publication Date
EP0062273A1 EP0062273A1 (fr) 1982-10-13
EP0062273B1 true EP0062273B1 (fr) 1986-07-23

Family

ID=4227396

Family Applications (1)

Application Number Title Priority Date Filing Date
EP82102626A Expired EP0062273B1 (fr) 1981-03-31 1982-03-29 Procédé pour asservir un moteur pas à pas

Country Status (6)

Country Link
US (1) US4456866A (enrdf_load_stackoverflow)
EP (1) EP0062273B1 (enrdf_load_stackoverflow)
JP (1) JPS57177296A (enrdf_load_stackoverflow)
CA (1) CA1174060A (enrdf_load_stackoverflow)
CH (1) CH644983GA3 (enrdf_load_stackoverflow)
DE (1) DE3272080D1 (enrdf_load_stackoverflow)

Families Citing this family (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CH649187GA3 (enrdf_load_stackoverflow) * 1982-10-13 1985-05-15
JPS5980147A (ja) * 1982-10-29 1984-05-09 Rhythm Watch Co Ltd 時計用小型モ−タ
JPH0681551B2 (ja) * 1984-10-16 1994-10-12 セイコ−電子工業株式会社 ステップモ−タの回転検出方法
DE69413668T2 (de) * 1993-01-18 1999-04-15 Seiko Instruments Inc., Tokio/Tokyo Zeitgeber

Family Cites Families (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4158287A (en) * 1976-08-12 1979-06-19 Citizen Watch Company Limited Driver circuit for electro-mechanical transducer
JPS5385467A (en) * 1976-12-30 1978-07-27 Seiko Epson Corp Electronic wristwatch
JPS53132385A (en) * 1977-04-23 1978-11-18 Seiko Instr & Electronics Ltd Electronic watch
JPS5477169A (en) * 1977-12-02 1979-06-20 Seiko Instr & Electronics Ltd Electronic watch
CH625384B (fr) * 1977-12-20 Ebauches Electroniques Sa Dispositif de detection de la non rotation de moteurs pas a pas pour piece d'horlogerie et de rattrapage des pas perdus.
FR2461399A1 (fr) * 1979-07-09 1981-01-30 Suisse Horlogerie Detecteur de position d'un moteur pas a pas

Also Published As

Publication number Publication date
EP0062273A1 (fr) 1982-10-13
CA1174060A (en) 1984-09-11
JPS57177296A (en) 1982-10-30
US4456866A (en) 1984-06-26
CH644983GA3 (enrdf_load_stackoverflow) 1984-09-14
DE3272080D1 (en) 1986-08-28

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