CA1175376A - Apparatus for positioning a typing disk in a printing device - Google Patents
Apparatus for positioning a typing disk in a printing deviceInfo
- Publication number
- CA1175376A CA1175376A CA000372191A CA372191A CA1175376A CA 1175376 A CA1175376 A CA 1175376A CA 000372191 A CA000372191 A CA 000372191A CA 372191 A CA372191 A CA 372191A CA 1175376 A CA1175376 A CA 1175376A
- Authority
- CA
- Canada
- Prior art keywords
- stepping motor
- control loop
- motor
- improvement
- signal
- 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
Links
Classifications
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
- B41J—TYPEWRITERS; SELECTIVE PRINTING MECHANISMS, i.e. MECHANISMS PRINTING OTHERWISE THAN FROM A FORME; CORRECTION OF TYPOGRAPHICAL ERRORS
- B41J1/00—Typewriters or selective printing mechanisms characterised by the mounting, arrangement or disposition of the types or dies
- B41J1/22—Typewriters or selective printing mechanisms characterised by the mounting, arrangement or disposition of the types or dies with types or dies mounted on carriers rotatable for selection
- B41J1/24—Typewriters or selective printing mechanisms characterised by the mounting, arrangement or disposition of the types or dies with types or dies mounted on carriers rotatable for selection the plane of the type or die face being perpendicular to the axis of rotation
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- G—PHYSICS
- G05—CONTROLLING; REGULATING
- G05B—CONTROL OR REGULATING SYSTEMS IN GENERAL; FUNCTIONAL ELEMENTS OF SUCH SYSTEMS; MONITORING OR TESTING ARRANGEMENTS FOR SUCH SYSTEMS OR ELEMENTS
- G05B19/00—Programme-control systems
- G05B19/02—Programme-control systems electric
- G05B19/18—Numerical control [NC], i.e. automatically operating machines, in particular machine tools, e.g. in a manufacturing environment, so as to execute positioning, movement or co-ordinated operations by means of programme data in numerical form
- G05B19/19—Numerical control [NC], i.e. automatically operating machines, in particular machine tools, e.g. in a manufacturing environment, so as to execute positioning, movement or co-ordinated operations by means of programme data in numerical form characterised by positioning or contouring control systems, e.g. to control position from one programmed point to another or to control movement along a programmed continuous path
- G05B19/39—Numerical control [NC], i.e. automatically operating machines, in particular machine tools, e.g. in a manufacturing environment, so as to execute positioning, movement or co-ordinated operations by means of programme data in numerical form characterised by positioning or contouring control systems, e.g. to control position from one programmed point to another or to control movement along a programmed continuous path using a combination of the means covered by at least two of the preceding sub-groups G05B19/21, G05B19/27, and G05B19/33
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- G—PHYSICS
- G05—CONTROLLING; REGULATING
- G05B—CONTROL OR REGULATING SYSTEMS IN GENERAL; FUNCTIONAL ELEMENTS OF SUCH SYSTEMS; MONITORING OR TESTING ARRANGEMENTS FOR SUCH SYSTEMS OR ELEMENTS
- G05B2219/00—Program-control systems
- G05B2219/30—Nc systems
- G05B2219/43—Speed, acceleration, deceleration control ADC
- G05B2219/43006—Acceleration, deceleration control
Abstract
ABSTRACT OF THE DISCLOSURE
An apparatus for positioning a typing disk in a printing device such as a teleprinter has a stepping motor having a rotary field which is operated by control circuitry so as to simulate a commutator-controlled direct current motor. The typing disk is driven by the stepping motor and is positioned by the operation of a digital coarse control loop and a post-connected analog precision control loop. The drive shaft of the stepping motor is also con-nected to a timing disk which operates in combination with an optical position transmitter to provide signals to the control loops representing incremental angular position changes.
An apparatus for positioning a typing disk in a printing device such as a teleprinter has a stepping motor having a rotary field which is operated by control circuitry so as to simulate a commutator-controlled direct current motor. The typing disk is driven by the stepping motor and is positioned by the operation of a digital coarse control loop and a post-connected analog precision control loop. The drive shaft of the stepping motor is also con-nected to a timing disk which operates in combination with an optical position transmitter to provide signals to the control loops representing incremental angular position changes.
Description
1~7537~ 1 , BACKGROUND OF THE INVENTION
Field of the Invention The present invention relates to devices and circuitry for operating a stepping motor, and in particular for operating a s~epping motor to position a type carrier in a printing device in combination with a position transmitter connected to the motor shat.
Descrip~ion of the Prior Art It is known to those skilled in the art of teleprinting and typewriter design to position a type carrier such as, for example, a typing cylinder or a typing disk, by the use of a stepping motor ollowed by a printing operation undertaken with a printing hammer according to the selected type character.
A device of this type, in which a typewri~er employs a typing cylinder which is positioned by means of a stepping motor, is known from German OS 2,156,093, corresponding to United States Patent 3,823l265. The typing cylinder is connected to ~ timing disk which serves as a position transmitter, the timing disk having ~`
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marks thereon corresponding to the number of type columns carried on the typing cylinder. The marks are scanned by a scanning device during pre-adjustment of the type carrier. The driving stepping motor is connected by suitable gearing with the typing cylinder and the associated timin~ disk.
In conventional devices wherein a type carrier is pre-set by the use of a stepping motor, it is customary to bring the motor to a stop in a na~ural stop position. The number of such stop positions can be multiplied by th~ use of appropriate gear mechanisms so as to coincide with the number of type columns or, if a typing disk is employed as the type carrier, to coincide with the number of typing spokes on the typing disk~ This conventional technique of obtaining the desired num~er of stop positions by a gear mechanism has the disadvantages of reducing the control precîsion and being susceptible to wear due to abrasion necessitating conscientious preventive maintenance such as lubrication.
The use of a commutator-controlled direct current motor in place of a stepping motor similarly does not overcome the dis-advantages because of the limited service life and reliability of the commutator, which experiences significant wear as a result of abrasion by the brushes.
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SUMNARY ~F THE INVENTION
It is an object of the present invention to provide an apparatus for operating a stepping motor in a printing device for positioning the type carrier by which the stepping motor is directly connected to the type carrier, such as a typing disk. It is a further object of the present invention to provide such an apparatus by which the type carrier can be adjusted as precisely as possible ~n a relatively short adjustment time~
The above objects are inventively achieved by an apparatus for operating a stepping motor which operates the motor in a manner 53'7~ 1 so as to simulate a commutator-controlled direct current motor. Circuitry including a plurality of switches respectively associated with th~ windings of the stepping motor is provided with an additional switching arrangement which alternately activates the winding switches. The circuitry generates a stator field which is controlled in dependence upon a position trans-mitter which is displaced with respect to the permanent rotor field of the stepping motor by a pre-set phase difference. The stepping motor is main~
tained in a holding position by logic circuitry which inverts the stator field in dependence upon an analog control signal received from the posit-ion transmitter.
Thus, in accordance with a broad aspect of the invention, thereis provided, in an apparatus for operating a stepping motor for positioning a type carrier in a printing device, said stepping motor having a rotor corotatably connected to said type carrier and to a timing disk for an optical position transmitter in said printing device, the improvement of:
a means for operating said stepping motor to simulate a commutator-control-led direct current motor including a plurality of electronic switches connected to individual windings of said stepping motor, a rotary field ; switch for alternatingly actuating individual ones of said switches, said means generating a stator field in accordance with signals received from said optical position transmitter, said stator field being displaced by a predetermined phase difference with respect to a permanent rotary field of said stepping motor.
The circuit disclosed and claimed herein results in an operation of the stepping motor which is analogous to a direct current motor and in effect operates as an "electronic commutator." Driving the stepping motor in this manner achieves the advantages of a direct current motor without the disadvantages of a genuine commutator, so that the service life and reliability of the motor is significantly improved for the reason that the wear normally associated with the action of the brushes on the commutator in a direct current motor is eliminated. The stepping motor can be operated I
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~75376 so as to stop precisely at positions corresponding to the number of spokes on a typîng disk by suitable inversion of the stator field.
For pre-adjustment of the typing disk~ a digital coarse control loop is included in the control circuitry~ A target point to which the typing disk is to be set is entered by a target address which is supplied to a device for generating a rotar~ field for operating the stepping motor so that the stepping motor is accelerated to a maximum speed which is stored in a memory and which is dependent upon the distance to the selected target position. The acceleration phase of the stepping motor may be followed, if necessary, by a coasting phase of constant rotational velocity.
;
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-3a-~7S376 which in turn is followed by a brake phase which is determined by a brake curve also stored in a memory. The stepping motor is braked until the typing disk is posi~ioned in the region of the target point at which time an analog fine control loop takes over and, in dependence upon the amplitude of the si~nal received from the position transmitter, undertakes precise positioning to the target point.
By the use of a control arrangement of the type described above, the control and positioning of the typing disk is undertaken digitally at first until the typing disk is positioned in the region of the target point, at which time positioning of the typing disk is undertaken by an analog process so that the disk can be adjusted with the required precision. This apparatus thus unites the advan-tages of digital control of the stepping motor with the advantages of precision adjustment heretofore obtainable only by ~he use of a servo direct current motor.
Moreover, a particularly rapid adjustment of the type carrier is possible with the above apparatus, because both the optimum acceleration characteristics and braking characteristics ~asso~ciated with a particular motor are stored for use, and can be called for each acceIeration and braking process.
DESCRIPTION OF THE DRAWINGS
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Fig. 1 is a block dia~ram of an apparatus for positioning a typing disk in a printing device constructed in accordance with the principles of the present invention~
Fig. 2 is a graphic representation of ~he output signals of the position transmitter employed in the apparatus of Fig. 1.
Fig. 3 is a graphic represent~tion of the manner by which the rotary field is controlled by the apparatus shown in Fig. 1 as a function of the position of the rotor of the stepping motor.
9,~7~37~
Fig. 4 is a schematic illustration of a three-phase stepping motor of the type employed in the present invention during operation with open winding.
Fig. 5 is a schematic representation of a three-phase stepping motor of the type employed in the present invention with short-circuited winding.
Fig. 6 is a graphic representation of the motor torque for compensation of the natural stop position.
Fig, 7 is a graphic representation of a signal for inverting the rotary field.
Fig. 8 is a block circuit diagram of the apparatus shown in Fig. 1 showing the coarse control loop in grea~er detail.
Fig. 9 is a graphic representation of a posi~ioning process undertaken by the apparatus of Figs. 1 and 8.
Fig. 10 is a graphic representation of the output of the ~ ~ poosition~transmitter during the positioning process of Fig. 9.
;~ ~ Fig. 11 is a block circuit diagram of the analog control :
loop employed in the apparatus of Figs. 1 and 8.
Fig. 12 is a circuit diagram of the value former employed in the fine control loop of Fig. 11.
Fig. 13 is a circuit diagram of the two-point current regulator and three-phase power bridge employed in ~he circuits of igs. l and ~. ~
DESC~IPTION OF THE PREFER~ED EMBODIMENTS
An apparatus is schematically shown in Fig. 1 for posi-tioning a typing disk T in a printing device such as, for example, ~a teletypewriter. The apparatus includes a three-phase stepping motor SM ha~ing a drive shaft which is corotationally coupled with the typing disk T and which is also corotati~nally coupled to a timing disk TS which is part of an incremental optical position transmitter PG. The timing disk TS has a number of apertures or ~'75376 slots corresponding to the number of spokes on the typing disk T, which apertures are scanned by an optical arrangement known to those skilled in the art, not shown in greater detail in Fig. 1.
The further elements of Fig. 1 together with the stepping motor form a closed control loop which includes a digital cOarse control loop DG which is connectable as required to the position transmitter PG by a switching device SE, as well as an analog fine control loop AF for precise positioning of the typing disk T, which is also connectable to the position transmitter PG via the switching device SE. The control loops ~F and DG are each connected to a rotary field switch DS which controls the s~epping motor SM, as well as to a two-point current regulator SR and a three-~hase power bridge LB~ By means of a conventional input device ~not shown) a signal SP such as a ta.rget signal or target address for the desired position of the typing disk T is supplied to the control loop.
After a completed positioning of the typing disk T, a printing hammer release signal is generated on line HF which brings about the~clearing and release of th~ printing hammer corresponding to the selected typing disk position.
The outputs of the position transmitter PG are graphically shown in:Fig. 2. Those output signals include a triangular control signal~:RS which:is shown in Fig.. 2 in dependence upon the angle of , : :
rotation DW of the stepping motor SM.
In addition to the control signal RS, the position transmitter PG also releases a rectangular index signal ID and a signal TTL, from which the direc~ion of movement of the typing disk T is deriv~d. The index signal ID and the direction signal TTL
are displaced with respect to the control signal RS by 90~.
The ~riangular control signal RS is required for ~he analog regulating process for precise positioning of the typing di~k T. As can be seen in Fig~ 2, certain portions of the ~riangular ~537~; 1 signal RS are in registr~ with portions of the signal TTL which are at O potential. Those portions of the signal RS correspond to the precision regulating region. The deviation of the potential of the signal RS in the vicinity of a printing point A is converted in the precision regulating region into a proportional motor current for controlling the'stepping motor SM~ At the zero passage A, depending upon the'sin, the motor direction, and corresponding torque, is invPrted ~ia the rotary field switch DS, whereby the position of the typing disk T is maintained. A signal AP has shaded regions shbwn beneath the control signal RS which define the clearing region in the vicinity of ~he printing position A
during which time the corresponding printing hammer is activated.
A brushless four-pole three-phase'stepping mo~or SM
serves as the drive for the typing disk T. The stepping motor SM
has the advantage over a commutator-controlled direct curren~ motor of operating with less abrasion and additionally has smaller external dimensions. As described above, the stepping motor SM is driven to simulate such a direct current motor by a suitable controlled elec-tronic rotary field.
During a revolution of the rotor of the stepping motor SM, the individual phases Pl, P2 and P3 are sequentially connected , to a current generator via the power bridge LB, as graphically shown in Fig. 3 and schematically represented in Figs. 4 and 5.
The result of such operation is the voltage pro~ression U shown in Fig. 3. The current course I during a motor phase Pl is also shown in Fig. 3. Beginning from the synchronized position, the angle of rotation DW is represented on the abscissa of the graph showing individual stop positions O to 11 which occur in the case of stepping motor operation with a short-circuited winding.
In order that the torque can be'released ~o the motor shaft, the stator fiel.d of the ~tepping motor SM must be phase displace'd with'respect' to the permanent rotor field by a pre-set ~753~6 phase difference angle, which for the purposes of this discussion is referenced PD, but is not shown in the drawings. The torque is theoretically proportional to the value of the sin PD and the motor current, which builds up the stator field. In the case of a homogenous field curve, the maximum is attained at a phase difference angle PD of 90 (mid-way between the stator and rotor field) al~hough the phase difference may be in the range of 60 to 120~ The stepping motor SM is controlled as shown in Fig. 4 such that of the three legs, in each case only two legs have current passing through them. In Figs. 4 and 5, the current vector is designated by i and the phases are designated by Pl, P2 and P3. The field switch over of the rotary field occurs in the region of + 30.
This results in the twelve switch over points shown in Fig. 3.
In the case of a conventional typing disk having 108 occupiable positions, the controlling arrangemen~ disclosed herein relays the stator field after nine mark or aperture divisions of the timing disk TS associated with the position transmitter PG are passed.
For satisfactory operation of the motor SM, it is neces-sary to relate the state of the stator field, as was done with the typing disk, to the synchronization position. In the case of static current flow, the initial position of the stator field is determined and the timing disk TS of the position transmitter PG
is oriented accordingly. me required phase difference of 90 is produced by the control arrangement, so that by means of this l'electronic commutator" the stepping motor SM behaves as a commutator-controlled direct current motor with twelve brushes.
- A typical operation for stepping motors with a 30 control system, of the type shown in Figs. 4 and S, whereby alter-natingly one winding conne~tion remains free, that is, two windings are operated in parallel, has disadvantages in the context of printing devices. ~ecause of the complete current degradation in ~ 7537~ 1 each case in the sh~rt-circuited winding, increased eddy curren~
losses result. The varying power consumption during switch over from the operating mode of Fig. 4 ~o an operating mode of Fig. 5 brings about torque fluctuations.
In order to maintain the stepping motor SM in a printing position A, by means of the control arrangement shown in Fig. 6 the rotary field is inverted by the rotary field switch DS, which cor-responds to a phase rotation of 180~. In Fig. 6, the vector BR
designa~es the rotor fieId direction and magnitude, the vector Ml represents the stator field with an associated inverse stator field represented by the vector M2, M designates the resultant torque vector and LW represents the load or stress angle of the stepping motor SM. The switch over of the rotary field proceeds with a frequency of approximately 5 kHz, whereby the position transmitter PG supplies the control signal RS for this process by means of the operational sin of the analog control signal RS. The current curve for the stepping motor I is shown in Fig. 7 plotted wi~h respect to time t, wherein TL and TR respectively represent ~he operating duration for left and right (or countercloclcwise and clockwise) rotation of the rotor. The'resulting moment M shown in Fig. 6 for the printing position A is determined by the equa~ion M = (Ml TL ~ sin LW) - (M2 TR sin LW).
A schematic block dia~ram is shown in Fig. 8 of the apparatus of Fig. 1 showing the coarse control loop DG, outlined by the dot and dash line, in greater detail. The digital course control loop DG obtains signals or the determination of the position in digital form which is indicated by RSD which is a digitalized version of the position signal RS. The loop DG also receives the rotation direction signal TT~ from the position transmitter PG. Proceeding from the'synchronized position, the positioning address SP is compared by a comparator VG with'the'actual position of the typin~
37f;
disk T which is determined by a known e~aluated circuit AUS, A logic circuit LA provided with the outpu~. of the comparator VG and an optimum brake curve supplied by a brake curve memory BKS selects the direction of rotation which provides the shortest connection or move-ment to the new posi~ion and the typing disk approaches the new posi-tion with maximum momen~, that is, with constant current. The digital control loop DG thus compares the velocity in each case given the time between the zero passages of the signal RS (and the correspondin&
digital signal RSD~ of the position transmitter with the desired value and determines whether to acceIerate, brake, or switch over to a coasting phase. The complete braking occurs by means of current reversal and takes place with maxi~um moment~
If the desired position is attained and the type which is to be printed is in the vicinity of the printing position A, switch over occurs to the analog position control loop AF, which takes over the precision control of the motor to move the typing disk T to the prin~ing position. The digital con~rol loop DG becomes active again only with a new address or as a result of a mechanical movement of the typing disk.
Positioning of the typing disk T to the next position proceeds via the shortest distance with the use of a velocity eurve o~ the type shown in Fig. 9. The rotary field is generated such that ~he motor attains its maximum r4tational velocity of appro-ximately 1400 revolutions per minute a~ter approximately 20 mark di~isions or apertures of the timing disk TS are scanned by the position transmitter PG, corresponding to approximately 70~ rotation.
As shown in Fig. 9, wherein the rotational ~elocity of the motor is presented on the ordinate and is plot~ed in dependence upon the distance between two positioni~g points A and B on the abscissa, the positioning pro~eeds f~m an initial position AN to the end position B as follows. The stepping motor SM is at firs~ accelerated ~17~376 up to position C. The point C is the'position where the velocity is attained which is pre-set by the braking curve. This acceleration phase is followed by a phase of constant velocity or coasting from point C to point Cl. From the point Cl to the tar~et or desired point B, the motor is braked corresponding to the'brake curve which is shown in Fig. 9 and which is stored in the brake curve memory BKS~
The brake curve contains the'rela~ionship between the velocity and distance up to the desired position B for an optimum braking process.
The curve is determined based on ~he most unfavorable conditions with respect to the magnetic tolerances of the motor, so that the motor comes to a stop in the target position B without significant overshoot. Different motors of course display different braking characteristics, however, these different characteristics are equalized by the braking curve associated with each motor which undertakes a ~continuous switch over between braking and coasting resulting in the step-shaped brake curve of the type shown in Fig. 9~ Each mo~or has an individual brake curve associated therewith, calculated and plotted in dependen e upon the'unique characteristîcs of the particular motor.
The brake curve is stored in the brake curve memory in the form of intervals3 so that the'angular velocity of the steppin~, motor SM is decreased to such an extent that ~omplete brakin~ can be undertaken in the vicinity o the target position B by the analog precision control loop AF. The actual braking proceeds such that at the beginning of each period of the received position transmitter signal RS, the measured actual velocity is compared with the pre-set value. In dependence upon the result of this comparison, during this signal period, a switch over occurs to braking or coas~ing as needed. When th~ distance to the desired position is smaller than 5 mark divisions, thls comparison is undertaken at each half mark division. In the next to last half mark division before the target position, depending upon thP ~easured vel'ocity, a selection is made 1~-~17~371~i 1 as to whether to permit the motor to coast, to emit a short brake pulse, or to emit a long brake pulse. In the last half mark division before the target position, the motor is actuated with a brake pulse having a duration dependent upon the measured velocity. Thus, the motor enters into the target position with a~propriate velocity. In the re~ion of the target position B, as stated above, the analog control loop AF brings the motor to the precise position. It is, of course, possible that the starting point AN and the target point B will be disposed closer to one another than in the example dis-cussed above, so ~hat no coasting period is necessary in between.
An accelerating and braking curve progression of this sort is also shown in Fig. 9, between the points Al, C2 and B.
A precise depiction of the positioning process from a point AN to a point B is shown in Fi~ 10, in which the control signal RS is plotted in dependence upon time t. The progression in Fig. 10 corresponds to the first example discussed in connection with Fig.~9, nameIy from the point AN to the point B. An accelera-tion region exists from the point AN to the point C, followed by a region of constant speed or coasting, which is not shown in Fig. 10, and finally followed by the actual braking which occurs in the region between the points Cl and the target point B. A deceleration region is referenced with V, which is divided into a number of different regions including region Vl, wherein the comparison takes place between the actual and desired value at the beginning of each period of the control signal RS, whereby the duration of a period of the control signal RS corresponds to one mark division.
Other comparisons are undertaken in the spacing of five mark divisions from the desired posi~ion B between the desired and actual values of the velocity in each half period of the signal RS, designated by the regions V2, Y3 and V4~ In the last half mark division V4 before the attainment of the target position B, the ~17~i37~; 1 velocity of the stepping motor is modulated to a constant target arrival velocity. The urther positioning is then taken over by the analog precision control loop AF. The entire process is divided into a digital control region DRB and an analog control region ARB.
For the precise regulation of the typing disk T to the printing position an analog control loop of the type shown in Fig. 11 in detail is employed. During the analog control phase ARB, a constant direction rotary field is supplied to an inverter IN based on information received from an analog evaluator AUS' and an analog control unit DRS~. The inverter IN supplies a signal to the rotary field switch DS to invert the rotary field after attainment of the printing position in order to hold the motor in the requested target position.
The analog precision control loop AF employs the amplitude of the analog transmitter signal RS of the position transmi~ter PG
as a regulated value, whereby the motor moment is regulated in dependence upon this value in rate and amplitude in such a manner that the tor comes to rest with an attenuated movement in the zero passage of the control signal. For monitoring, an additional ampli-fier (not shown) is provided, to which is supplied the transmitter signal RS, and which supplies an output signal which indicates whether the typing disk T is positioned sufficiently precisely in the printing position. If the printing position is attained, by means of the analog evalua~or AUS', after a pre-set time of approximately 2 ms, during which the position may no longer change, the printing is cleared.
After a printing operation, the amplification of the analo~ precision control loop is lowered to such an extent that the motor SM still is maintained in the desired position, h~wever, a disturbance noise which is only weakly audible as a result of the constant rotary field inversion via the inverter IN is produced.
~753~
The analog precision control loop AF contains a propor-tional-differential regulator PD, which is connect d to an int gral regulator IR. A value former BB is post-connected to the propor-tional-differential regulator PD, which is connected throu~h a two-point current regulator SR with the rotary field switch DS.
The integral regulator IR performs the function of sub-stantially increasing the amplification for signals which are almost static at a low an~ular velocity or standstill, so that the influence of ~he permanent motor stop moment is suppressed and a better posi-tioning precision is attained. For fast movements, however, the integral regulator IR is substantially without effect.
The proportional-differential regulator PD performs the function of compensat;ng the lagging mechanical and electrical phase displacement of the motor SM. The amplification progression is thereby accommodated to the motor movement such that the attenuation of the rotational movement proceeds in the zero passage of the output signal of the position transmitter RS. By this operation, the . , oscillation tendency of the entire analog control loop is significantly attenuated.
The output signal of the proportional-differential regulator PD is supplied to one side of the inverter IN and is also supplied to the value former BB, which converts the deviation from the zero point into a proportional direct voltage.
This direct voltage is converted in the two-point current regulator SR into a proportional current and thus into a proportional motor moment.
The value former BB shown in Fig. 12, which is employed in the fine control loop AF, is a precision rectifier with a low zeroing error~ The value formar BB consists of two operational amplifier~ OPl and OP2, which have a common output and which are connected such that one amplifier has an amplification factor of ~ 753716 1 ~1 and the other amplifier has an amplification factor of -1. For this purpose, the inverting input of the first operational amplifier OPl is directly coupled to the output thereof, while the invertin~
input of the second operational amplifier OP2 is connected through a resistor Rl which may, for example, have a value of 10 kQ, to the common output UA. An input signal is supplied to the inverting in-put of the amplifier OP2 through a resistor R2, which may, for example, have a value of 10 kQ, and is supplied directly to the non-inverting input of the amplifier OPl. The'operation of the ~alue former BB on an input signal OV, supplied to the input W , is shown by the resulting output signal OV' appearing at the output UA, which is negatively rectified.
As described a~ove, the stepping motor SM is operated with an impressed current which in the'target or printing position can be regulated to zero. This occurs as shown in Fig. 13 by means of the operation of the rotary field switch DS in combination with a power bridge LB having six transistors T connected in Darlington pairs for actuating the stepping motor SM with a corresponding current.
For the coasting phase, the power bridge LB is in a blocking state and the motor is essentially currentless. The two-point regulator operates with a set frequency of approximately 40 kHz, which is supplied to an operational amplifier OP3. In the amplifier OP3, the preampliied current signal, which is measured by a resistor R3, is compared in the analog control loop AF to the output signal of the value former BB, or, in the'digital coarse control loop DG, is compared to a constan~ voltage. The result of either comparison controls a switching transistor ST. Corresponding to the control signal received at the base of the transistor ST, the transistor activates the'stepping motor SM through a feeder reactor L with an operating voltage of approximatPly 40 volts. Upon dis-connection of the switching tranaistor ST, in order to avoid im-precisions in controlling the motor, it is nece'ssary to quickly ~L7~371f~ 1 dissipate energy which is stored in the entire circuit arrangement.
This is undertaken by means of a feedback transformer RT, the primary winding of which is connected through a coasting diode D3 with the output of the switching transistor ST, and the secondary winding of which is connected through a feedback diode D2 with a direct voltage source S~ The windings of the feedback transformer R~ are connected electrically oppositely 7 SO that the ratio amounts to 1:2. The feedback transformer RT dissipates the energy stored in the circuit in the disconnected state of the switching transistor ST by diverting the'energy back to the'voltage'supply S.
In the disconnected state of the switching transistor ST, the output of the transistor ST is at a potential of -20 volts as a result of the presence of the feeder reactor L. This voltage leads to a voltage of 40 volts at the feedback transformer RT on the secondary side,' whereby through thP feedback diode D2 a feedback of the stored energy results to the direct voltage source S. In addi-tion to the diodes D2 and D3, a further coasting diode Dl is dis-posed between the'output of the feeder reactor L and the voltage source S. The coasting diode, which.is associated w~th the stepping motor SM, perorms the function of guiding the'energy stored in the feeder reactor L back to the'direct voltage supply S during blocking of the transistors T through the rotary field control switch DS.
Al~hough modifications and ehanges may be suggested by those skilled in the art it is the intention of the inventors to 'embody within the patent warranted hereon all changes and modifica-tions as reasonably and properly come within the scope of their contribution to th~'art.
Field of the Invention The present invention relates to devices and circuitry for operating a stepping motor, and in particular for operating a s~epping motor to position a type carrier in a printing device in combination with a position transmitter connected to the motor shat.
Descrip~ion of the Prior Art It is known to those skilled in the art of teleprinting and typewriter design to position a type carrier such as, for example, a typing cylinder or a typing disk, by the use of a stepping motor ollowed by a printing operation undertaken with a printing hammer according to the selected type character.
A device of this type, in which a typewri~er employs a typing cylinder which is positioned by means of a stepping motor, is known from German OS 2,156,093, corresponding to United States Patent 3,823l265. The typing cylinder is connected to ~ timing disk which serves as a position transmitter, the timing disk having ~`
i ~ ~7S3~
marks thereon corresponding to the number of type columns carried on the typing cylinder. The marks are scanned by a scanning device during pre-adjustment of the type carrier. The driving stepping motor is connected by suitable gearing with the typing cylinder and the associated timin~ disk.
In conventional devices wherein a type carrier is pre-set by the use of a stepping motor, it is customary to bring the motor to a stop in a na~ural stop position. The number of such stop positions can be multiplied by th~ use of appropriate gear mechanisms so as to coincide with the number of type columns or, if a typing disk is employed as the type carrier, to coincide with the number of typing spokes on the typing disk~ This conventional technique of obtaining the desired num~er of stop positions by a gear mechanism has the disadvantages of reducing the control precîsion and being susceptible to wear due to abrasion necessitating conscientious preventive maintenance such as lubrication.
The use of a commutator-controlled direct current motor in place of a stepping motor similarly does not overcome the dis-advantages because of the limited service life and reliability of the commutator, which experiences significant wear as a result of abrasion by the brushes.
: ~ ~ .
SUMNARY ~F THE INVENTION
It is an object of the present invention to provide an apparatus for operating a stepping motor in a printing device for positioning the type carrier by which the stepping motor is directly connected to the type carrier, such as a typing disk. It is a further object of the present invention to provide such an apparatus by which the type carrier can be adjusted as precisely as possible ~n a relatively short adjustment time~
The above objects are inventively achieved by an apparatus for operating a stepping motor which operates the motor in a manner 53'7~ 1 so as to simulate a commutator-controlled direct current motor. Circuitry including a plurality of switches respectively associated with th~ windings of the stepping motor is provided with an additional switching arrangement which alternately activates the winding switches. The circuitry generates a stator field which is controlled in dependence upon a position trans-mitter which is displaced with respect to the permanent rotor field of the stepping motor by a pre-set phase difference. The stepping motor is main~
tained in a holding position by logic circuitry which inverts the stator field in dependence upon an analog control signal received from the posit-ion transmitter.
Thus, in accordance with a broad aspect of the invention, thereis provided, in an apparatus for operating a stepping motor for positioning a type carrier in a printing device, said stepping motor having a rotor corotatably connected to said type carrier and to a timing disk for an optical position transmitter in said printing device, the improvement of:
a means for operating said stepping motor to simulate a commutator-control-led direct current motor including a plurality of electronic switches connected to individual windings of said stepping motor, a rotary field ; switch for alternatingly actuating individual ones of said switches, said means generating a stator field in accordance with signals received from said optical position transmitter, said stator field being displaced by a predetermined phase difference with respect to a permanent rotary field of said stepping motor.
The circuit disclosed and claimed herein results in an operation of the stepping motor which is analogous to a direct current motor and in effect operates as an "electronic commutator." Driving the stepping motor in this manner achieves the advantages of a direct current motor without the disadvantages of a genuine commutator, so that the service life and reliability of the motor is significantly improved for the reason that the wear normally associated with the action of the brushes on the commutator in a direct current motor is eliminated. The stepping motor can be operated I
.~
~75376 so as to stop precisely at positions corresponding to the number of spokes on a typîng disk by suitable inversion of the stator field.
For pre-adjustment of the typing disk~ a digital coarse control loop is included in the control circuitry~ A target point to which the typing disk is to be set is entered by a target address which is supplied to a device for generating a rotar~ field for operating the stepping motor so that the stepping motor is accelerated to a maximum speed which is stored in a memory and which is dependent upon the distance to the selected target position. The acceleration phase of the stepping motor may be followed, if necessary, by a coasting phase of constant rotational velocity.
;
~, ~
~:
-3a-~7S376 which in turn is followed by a brake phase which is determined by a brake curve also stored in a memory. The stepping motor is braked until the typing disk is posi~ioned in the region of the target point at which time an analog fine control loop takes over and, in dependence upon the amplitude of the si~nal received from the position transmitter, undertakes precise positioning to the target point.
By the use of a control arrangement of the type described above, the control and positioning of the typing disk is undertaken digitally at first until the typing disk is positioned in the region of the target point, at which time positioning of the typing disk is undertaken by an analog process so that the disk can be adjusted with the required precision. This apparatus thus unites the advan-tages of digital control of the stepping motor with the advantages of precision adjustment heretofore obtainable only by ~he use of a servo direct current motor.
Moreover, a particularly rapid adjustment of the type carrier is possible with the above apparatus, because both the optimum acceleration characteristics and braking characteristics ~asso~ciated with a particular motor are stored for use, and can be called for each acceIeration and braking process.
DESCRIPTION OF THE DRAWINGS
;: ~
Fig. 1 is a block dia~ram of an apparatus for positioning a typing disk in a printing device constructed in accordance with the principles of the present invention~
Fig. 2 is a graphic representation of ~he output signals of the position transmitter employed in the apparatus of Fig. 1.
Fig. 3 is a graphic represent~tion of the manner by which the rotary field is controlled by the apparatus shown in Fig. 1 as a function of the position of the rotor of the stepping motor.
9,~7~37~
Fig. 4 is a schematic illustration of a three-phase stepping motor of the type employed in the present invention during operation with open winding.
Fig. 5 is a schematic representation of a three-phase stepping motor of the type employed in the present invention with short-circuited winding.
Fig. 6 is a graphic representation of the motor torque for compensation of the natural stop position.
Fig, 7 is a graphic representation of a signal for inverting the rotary field.
Fig. 8 is a block circuit diagram of the apparatus shown in Fig. 1 showing the coarse control loop in grea~er detail.
Fig. 9 is a graphic representation of a posi~ioning process undertaken by the apparatus of Figs. 1 and 8.
Fig. 10 is a graphic representation of the output of the ~ ~ poosition~transmitter during the positioning process of Fig. 9.
;~ ~ Fig. 11 is a block circuit diagram of the analog control :
loop employed in the apparatus of Figs. 1 and 8.
Fig. 12 is a circuit diagram of the value former employed in the fine control loop of Fig. 11.
Fig. 13 is a circuit diagram of the two-point current regulator and three-phase power bridge employed in ~he circuits of igs. l and ~. ~
DESC~IPTION OF THE PREFER~ED EMBODIMENTS
An apparatus is schematically shown in Fig. 1 for posi-tioning a typing disk T in a printing device such as, for example, ~a teletypewriter. The apparatus includes a three-phase stepping motor SM ha~ing a drive shaft which is corotationally coupled with the typing disk T and which is also corotati~nally coupled to a timing disk TS which is part of an incremental optical position transmitter PG. The timing disk TS has a number of apertures or ~'75376 slots corresponding to the number of spokes on the typing disk T, which apertures are scanned by an optical arrangement known to those skilled in the art, not shown in greater detail in Fig. 1.
The further elements of Fig. 1 together with the stepping motor form a closed control loop which includes a digital cOarse control loop DG which is connectable as required to the position transmitter PG by a switching device SE, as well as an analog fine control loop AF for precise positioning of the typing disk T, which is also connectable to the position transmitter PG via the switching device SE. The control loops ~F and DG are each connected to a rotary field switch DS which controls the s~epping motor SM, as well as to a two-point current regulator SR and a three-~hase power bridge LB~ By means of a conventional input device ~not shown) a signal SP such as a ta.rget signal or target address for the desired position of the typing disk T is supplied to the control loop.
After a completed positioning of the typing disk T, a printing hammer release signal is generated on line HF which brings about the~clearing and release of th~ printing hammer corresponding to the selected typing disk position.
The outputs of the position transmitter PG are graphically shown in:Fig. 2. Those output signals include a triangular control signal~:RS which:is shown in Fig.. 2 in dependence upon the angle of , : :
rotation DW of the stepping motor SM.
In addition to the control signal RS, the position transmitter PG also releases a rectangular index signal ID and a signal TTL, from which the direc~ion of movement of the typing disk T is deriv~d. The index signal ID and the direction signal TTL
are displaced with respect to the control signal RS by 90~.
The ~riangular control signal RS is required for ~he analog regulating process for precise positioning of the typing di~k T. As can be seen in Fig~ 2, certain portions of the ~riangular ~537~; 1 signal RS are in registr~ with portions of the signal TTL which are at O potential. Those portions of the signal RS correspond to the precision regulating region. The deviation of the potential of the signal RS in the vicinity of a printing point A is converted in the precision regulating region into a proportional motor current for controlling the'stepping motor SM~ At the zero passage A, depending upon the'sin, the motor direction, and corresponding torque, is invPrted ~ia the rotary field switch DS, whereby the position of the typing disk T is maintained. A signal AP has shaded regions shbwn beneath the control signal RS which define the clearing region in the vicinity of ~he printing position A
during which time the corresponding printing hammer is activated.
A brushless four-pole three-phase'stepping mo~or SM
serves as the drive for the typing disk T. The stepping motor SM
has the advantage over a commutator-controlled direct curren~ motor of operating with less abrasion and additionally has smaller external dimensions. As described above, the stepping motor SM is driven to simulate such a direct current motor by a suitable controlled elec-tronic rotary field.
During a revolution of the rotor of the stepping motor SM, the individual phases Pl, P2 and P3 are sequentially connected , to a current generator via the power bridge LB, as graphically shown in Fig. 3 and schematically represented in Figs. 4 and 5.
The result of such operation is the voltage pro~ression U shown in Fig. 3. The current course I during a motor phase Pl is also shown in Fig. 3. Beginning from the synchronized position, the angle of rotation DW is represented on the abscissa of the graph showing individual stop positions O to 11 which occur in the case of stepping motor operation with a short-circuited winding.
In order that the torque can be'released ~o the motor shaft, the stator fiel.d of the ~tepping motor SM must be phase displace'd with'respect' to the permanent rotor field by a pre-set ~753~6 phase difference angle, which for the purposes of this discussion is referenced PD, but is not shown in the drawings. The torque is theoretically proportional to the value of the sin PD and the motor current, which builds up the stator field. In the case of a homogenous field curve, the maximum is attained at a phase difference angle PD of 90 (mid-way between the stator and rotor field) al~hough the phase difference may be in the range of 60 to 120~ The stepping motor SM is controlled as shown in Fig. 4 such that of the three legs, in each case only two legs have current passing through them. In Figs. 4 and 5, the current vector is designated by i and the phases are designated by Pl, P2 and P3. The field switch over of the rotary field occurs in the region of + 30.
This results in the twelve switch over points shown in Fig. 3.
In the case of a conventional typing disk having 108 occupiable positions, the controlling arrangemen~ disclosed herein relays the stator field after nine mark or aperture divisions of the timing disk TS associated with the position transmitter PG are passed.
For satisfactory operation of the motor SM, it is neces-sary to relate the state of the stator field, as was done with the typing disk, to the synchronization position. In the case of static current flow, the initial position of the stator field is determined and the timing disk TS of the position transmitter PG
is oriented accordingly. me required phase difference of 90 is produced by the control arrangement, so that by means of this l'electronic commutator" the stepping motor SM behaves as a commutator-controlled direct current motor with twelve brushes.
- A typical operation for stepping motors with a 30 control system, of the type shown in Figs. 4 and S, whereby alter-natingly one winding conne~tion remains free, that is, two windings are operated in parallel, has disadvantages in the context of printing devices. ~ecause of the complete current degradation in ~ 7537~ 1 each case in the sh~rt-circuited winding, increased eddy curren~
losses result. The varying power consumption during switch over from the operating mode of Fig. 4 ~o an operating mode of Fig. 5 brings about torque fluctuations.
In order to maintain the stepping motor SM in a printing position A, by means of the control arrangement shown in Fig. 6 the rotary field is inverted by the rotary field switch DS, which cor-responds to a phase rotation of 180~. In Fig. 6, the vector BR
designa~es the rotor fieId direction and magnitude, the vector Ml represents the stator field with an associated inverse stator field represented by the vector M2, M designates the resultant torque vector and LW represents the load or stress angle of the stepping motor SM. The switch over of the rotary field proceeds with a frequency of approximately 5 kHz, whereby the position transmitter PG supplies the control signal RS for this process by means of the operational sin of the analog control signal RS. The current curve for the stepping motor I is shown in Fig. 7 plotted wi~h respect to time t, wherein TL and TR respectively represent ~he operating duration for left and right (or countercloclcwise and clockwise) rotation of the rotor. The'resulting moment M shown in Fig. 6 for the printing position A is determined by the equa~ion M = (Ml TL ~ sin LW) - (M2 TR sin LW).
A schematic block dia~ram is shown in Fig. 8 of the apparatus of Fig. 1 showing the coarse control loop DG, outlined by the dot and dash line, in greater detail. The digital course control loop DG obtains signals or the determination of the position in digital form which is indicated by RSD which is a digitalized version of the position signal RS. The loop DG also receives the rotation direction signal TT~ from the position transmitter PG. Proceeding from the'synchronized position, the positioning address SP is compared by a comparator VG with'the'actual position of the typin~
37f;
disk T which is determined by a known e~aluated circuit AUS, A logic circuit LA provided with the outpu~. of the comparator VG and an optimum brake curve supplied by a brake curve memory BKS selects the direction of rotation which provides the shortest connection or move-ment to the new posi~ion and the typing disk approaches the new posi-tion with maximum momen~, that is, with constant current. The digital control loop DG thus compares the velocity in each case given the time between the zero passages of the signal RS (and the correspondin&
digital signal RSD~ of the position transmitter with the desired value and determines whether to acceIerate, brake, or switch over to a coasting phase. The complete braking occurs by means of current reversal and takes place with maxi~um moment~
If the desired position is attained and the type which is to be printed is in the vicinity of the printing position A, switch over occurs to the analog position control loop AF, which takes over the precision control of the motor to move the typing disk T to the prin~ing position. The digital con~rol loop DG becomes active again only with a new address or as a result of a mechanical movement of the typing disk.
Positioning of the typing disk T to the next position proceeds via the shortest distance with the use of a velocity eurve o~ the type shown in Fig. 9. The rotary field is generated such that ~he motor attains its maximum r4tational velocity of appro-ximately 1400 revolutions per minute a~ter approximately 20 mark di~isions or apertures of the timing disk TS are scanned by the position transmitter PG, corresponding to approximately 70~ rotation.
As shown in Fig. 9, wherein the rotational ~elocity of the motor is presented on the ordinate and is plot~ed in dependence upon the distance between two positioni~g points A and B on the abscissa, the positioning pro~eeds f~m an initial position AN to the end position B as follows. The stepping motor SM is at firs~ accelerated ~17~376 up to position C. The point C is the'position where the velocity is attained which is pre-set by the braking curve. This acceleration phase is followed by a phase of constant velocity or coasting from point C to point Cl. From the point Cl to the tar~et or desired point B, the motor is braked corresponding to the'brake curve which is shown in Fig. 9 and which is stored in the brake curve memory BKS~
The brake curve contains the'rela~ionship between the velocity and distance up to the desired position B for an optimum braking process.
The curve is determined based on ~he most unfavorable conditions with respect to the magnetic tolerances of the motor, so that the motor comes to a stop in the target position B without significant overshoot. Different motors of course display different braking characteristics, however, these different characteristics are equalized by the braking curve associated with each motor which undertakes a ~continuous switch over between braking and coasting resulting in the step-shaped brake curve of the type shown in Fig. 9~ Each mo~or has an individual brake curve associated therewith, calculated and plotted in dependen e upon the'unique characteristîcs of the particular motor.
The brake curve is stored in the brake curve memory in the form of intervals3 so that the'angular velocity of the steppin~, motor SM is decreased to such an extent that ~omplete brakin~ can be undertaken in the vicinity o the target position B by the analog precision control loop AF. The actual braking proceeds such that at the beginning of each period of the received position transmitter signal RS, the measured actual velocity is compared with the pre-set value. In dependence upon the result of this comparison, during this signal period, a switch over occurs to braking or coas~ing as needed. When th~ distance to the desired position is smaller than 5 mark divisions, thls comparison is undertaken at each half mark division. In the next to last half mark division before the target position, depending upon thP ~easured vel'ocity, a selection is made 1~-~17~371~i 1 as to whether to permit the motor to coast, to emit a short brake pulse, or to emit a long brake pulse. In the last half mark division before the target position, the motor is actuated with a brake pulse having a duration dependent upon the measured velocity. Thus, the motor enters into the target position with a~propriate velocity. In the re~ion of the target position B, as stated above, the analog control loop AF brings the motor to the precise position. It is, of course, possible that the starting point AN and the target point B will be disposed closer to one another than in the example dis-cussed above, so ~hat no coasting period is necessary in between.
An accelerating and braking curve progression of this sort is also shown in Fig. 9, between the points Al, C2 and B.
A precise depiction of the positioning process from a point AN to a point B is shown in Fi~ 10, in which the control signal RS is plotted in dependence upon time t. The progression in Fig. 10 corresponds to the first example discussed in connection with Fig.~9, nameIy from the point AN to the point B. An accelera-tion region exists from the point AN to the point C, followed by a region of constant speed or coasting, which is not shown in Fig. 10, and finally followed by the actual braking which occurs in the region between the points Cl and the target point B. A deceleration region is referenced with V, which is divided into a number of different regions including region Vl, wherein the comparison takes place between the actual and desired value at the beginning of each period of the control signal RS, whereby the duration of a period of the control signal RS corresponds to one mark division.
Other comparisons are undertaken in the spacing of five mark divisions from the desired posi~ion B between the desired and actual values of the velocity in each half period of the signal RS, designated by the regions V2, Y3 and V4~ In the last half mark division V4 before the attainment of the target position B, the ~17~i37~; 1 velocity of the stepping motor is modulated to a constant target arrival velocity. The urther positioning is then taken over by the analog precision control loop AF. The entire process is divided into a digital control region DRB and an analog control region ARB.
For the precise regulation of the typing disk T to the printing position an analog control loop of the type shown in Fig. 11 in detail is employed. During the analog control phase ARB, a constant direction rotary field is supplied to an inverter IN based on information received from an analog evaluator AUS' and an analog control unit DRS~. The inverter IN supplies a signal to the rotary field switch DS to invert the rotary field after attainment of the printing position in order to hold the motor in the requested target position.
The analog precision control loop AF employs the amplitude of the analog transmitter signal RS of the position transmi~ter PG
as a regulated value, whereby the motor moment is regulated in dependence upon this value in rate and amplitude in such a manner that the tor comes to rest with an attenuated movement in the zero passage of the control signal. For monitoring, an additional ampli-fier (not shown) is provided, to which is supplied the transmitter signal RS, and which supplies an output signal which indicates whether the typing disk T is positioned sufficiently precisely in the printing position. If the printing position is attained, by means of the analog evalua~or AUS', after a pre-set time of approximately 2 ms, during which the position may no longer change, the printing is cleared.
After a printing operation, the amplification of the analo~ precision control loop is lowered to such an extent that the motor SM still is maintained in the desired position, h~wever, a disturbance noise which is only weakly audible as a result of the constant rotary field inversion via the inverter IN is produced.
~753~
The analog precision control loop AF contains a propor-tional-differential regulator PD, which is connect d to an int gral regulator IR. A value former BB is post-connected to the propor-tional-differential regulator PD, which is connected throu~h a two-point current regulator SR with the rotary field switch DS.
The integral regulator IR performs the function of sub-stantially increasing the amplification for signals which are almost static at a low an~ular velocity or standstill, so that the influence of ~he permanent motor stop moment is suppressed and a better posi-tioning precision is attained. For fast movements, however, the integral regulator IR is substantially without effect.
The proportional-differential regulator PD performs the function of compensat;ng the lagging mechanical and electrical phase displacement of the motor SM. The amplification progression is thereby accommodated to the motor movement such that the attenuation of the rotational movement proceeds in the zero passage of the output signal of the position transmitter RS. By this operation, the . , oscillation tendency of the entire analog control loop is significantly attenuated.
The output signal of the proportional-differential regulator PD is supplied to one side of the inverter IN and is also supplied to the value former BB, which converts the deviation from the zero point into a proportional direct voltage.
This direct voltage is converted in the two-point current regulator SR into a proportional current and thus into a proportional motor moment.
The value former BB shown in Fig. 12, which is employed in the fine control loop AF, is a precision rectifier with a low zeroing error~ The value formar BB consists of two operational amplifier~ OPl and OP2, which have a common output and which are connected such that one amplifier has an amplification factor of ~ 753716 1 ~1 and the other amplifier has an amplification factor of -1. For this purpose, the inverting input of the first operational amplifier OPl is directly coupled to the output thereof, while the invertin~
input of the second operational amplifier OP2 is connected through a resistor Rl which may, for example, have a value of 10 kQ, to the common output UA. An input signal is supplied to the inverting in-put of the amplifier OP2 through a resistor R2, which may, for example, have a value of 10 kQ, and is supplied directly to the non-inverting input of the amplifier OPl. The'operation of the ~alue former BB on an input signal OV, supplied to the input W , is shown by the resulting output signal OV' appearing at the output UA, which is negatively rectified.
As described a~ove, the stepping motor SM is operated with an impressed current which in the'target or printing position can be regulated to zero. This occurs as shown in Fig. 13 by means of the operation of the rotary field switch DS in combination with a power bridge LB having six transistors T connected in Darlington pairs for actuating the stepping motor SM with a corresponding current.
For the coasting phase, the power bridge LB is in a blocking state and the motor is essentially currentless. The two-point regulator operates with a set frequency of approximately 40 kHz, which is supplied to an operational amplifier OP3. In the amplifier OP3, the preampliied current signal, which is measured by a resistor R3, is compared in the analog control loop AF to the output signal of the value former BB, or, in the'digital coarse control loop DG, is compared to a constan~ voltage. The result of either comparison controls a switching transistor ST. Corresponding to the control signal received at the base of the transistor ST, the transistor activates the'stepping motor SM through a feeder reactor L with an operating voltage of approximatPly 40 volts. Upon dis-connection of the switching tranaistor ST, in order to avoid im-precisions in controlling the motor, it is nece'ssary to quickly ~L7~371f~ 1 dissipate energy which is stored in the entire circuit arrangement.
This is undertaken by means of a feedback transformer RT, the primary winding of which is connected through a coasting diode D3 with the output of the switching transistor ST, and the secondary winding of which is connected through a feedback diode D2 with a direct voltage source S~ The windings of the feedback transformer R~ are connected electrically oppositely 7 SO that the ratio amounts to 1:2. The feedback transformer RT dissipates the energy stored in the circuit in the disconnected state of the switching transistor ST by diverting the'energy back to the'voltage'supply S.
In the disconnected state of the switching transistor ST, the output of the transistor ST is at a potential of -20 volts as a result of the presence of the feeder reactor L. This voltage leads to a voltage of 40 volts at the feedback transformer RT on the secondary side,' whereby through thP feedback diode D2 a feedback of the stored energy results to the direct voltage source S. In addi-tion to the diodes D2 and D3, a further coasting diode Dl is dis-posed between the'output of the feeder reactor L and the voltage source S. The coasting diode, which.is associated w~th the stepping motor SM, perorms the function of guiding the'energy stored in the feeder reactor L back to the'direct voltage supply S during blocking of the transistors T through the rotary field control switch DS.
Al~hough modifications and ehanges may be suggested by those skilled in the art it is the intention of the inventors to 'embody within the patent warranted hereon all changes and modifica-tions as reasonably and properly come within the scope of their contribution to th~'art.
Claims (9)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. In an apparatus for operating a stepping motor for positioning a type carrier in a printing device, said stepping motor having a rotor coro-tatably connected to said type carrier and to a timing disk for an optical position transmitter in said printing device, the improvement of: a means for operating said stepping motor to simulate a commutator-controlled direct current motor including a plurality of electronic switches connected to individual windings of said stepping motor, a rotary field switch for alter-natingly actuating individual ones of said switches, said means generating a stator field in accordance with signals received from said optical position transmitter, said stator field being displaced by a predetermined phase difference with respect to a permanent rotary field of said stepping motor.
2. The improvement of claim 1 further comprising a logic circuit in said means for operating said stepping motor for providing signals to said rotary field switch for inverting said stator field in dependence upon an analog control signal received from said position transmitter to maintain said stepping motor in a selected stop position.
3. The improvement of claim 1 wherein said stepping motor is a three pole stepping motor having three leads, and during operation of said stepping motor at any time only two of said leads receive operating current from said means for operating said motor.
4. The improvement of claim 1 wherein said preselected phase difference is in the range of 60° to 120°.
5. The improvement of claim 1 wherein said means for operating said stepping motor to simulate a commutator-controlled direct current motor includes a digital control loop, said digital control loop having a means for receiving a signal representing a target point at which said type carrier is to be positioned, said digital control loop further including a means for comparing said target point with the actual position of said type carrier, said digital control loop supplying a signal to said rotary field switch and to a power bridge connected thereto for maximally accelerating said stepping motor to a rotational speed which is dependent upon the distance to the target position, said acceleration being deter-mined by an acceleration curve stored in a memory contained in said digital control loop, said digital control loop subsequently operating said stepping motor at a constant rotational velocity if necessary followed by a braking phase which is determined by a braking curve stored in said memory for braking said stepping motor in the vicinity of said target point, said improvement further com-prising an analog control loop connected to said digital control loop and to said optical position transmitter for precisely posi-tioning said type carrier at said target point.
6. The improvement of claim 5 wherein said position transmitter generates a first output signal which is a sawtooth wave having a plurality of zero crossings representing printable target points for said type carrier, a second output signal which is a rectangular pulse wave which is displaced with respect to said first signal by a predetermined phase angle for derivation of the direction of movement of said type carrier, and a third signal which is a rectangular pulse signal for synchronizing said type carrier.
7. The improvement of claim 6 wherein said analog control loop is comprised of a proportional differential regulator which is post-connected to said position transmitter and connected to an integral regulator, said proportional differential regulator having an output connected to a value former for converting the deviation from the zero point of said output from said proportional differen-tial regulator to a proportional direct voltage, said value former connected through a two-point regulator with said rotary field switch for operating said stepping motor.
8. The improvement of claim 7 wherein said value former has an input and an output and is comprised of a first operational amplifier and a second operational amplifier each having an output connected to the output of said value former, the output of said first operational amplifier being further connected to the inverting input thereof, and the output of said second operational amplifier being further connected through a first resistor to the inverting input thereof, said first operational amplifier having a non-inverting input directly connected to the input of said value former and said second operational amplifier being connected to the input of said value former through a second resistor having a value equal to said first resistor connected to the inverting input of said second opera-tional amplifier.
9. The improvement of claim 7 wherein said two-point regulator is comprised of a feedback transformer connected to said stepping motor and to a direct voltage supply, and a feedback switching diode connected to said feedback transformer whereby when said feedback transformer is disconnected said transformer transfers energy drawn from the stepping motor to said voltage supply.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DEP3008289.4 | 1980-03-04 | ||
| DE19803008289 DE3008289C2 (en) | 1980-03-04 | 1980-03-04 | Arrangement for positioning a type disc in a teletypewriter |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1175376A true CA1175376A (en) | 1984-10-02 |
Family
ID=6096249
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000372191A Expired CA1175376A (en) | 1980-03-04 | 1981-03-03 | Apparatus for positioning a typing disk in a printing device |
Country Status (4)
| Country | Link |
|---|---|
| EP (1) | EP0035258B1 (en) |
| JP (1) | JPS5910159B2 (en) |
| CA (1) | CA1175376A (en) |
| DE (1) | DE3008289C2 (en) |
Families Citing this family (11)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE3272994D1 (en) * | 1981-05-21 | 1986-10-09 | Dataproducts Corp | Incremental motion motor control system |
| US4461588A (en) * | 1981-06-19 | 1984-07-24 | Matsushita Electric Industrial Co., Ltd. | Serial printing mechanism |
| DE3309433A1 (en) * | 1983-03-16 | 1984-09-20 | Siemens AG, 1000 Berlin und 8000 München | METHOD AND ARRANGEMENT FOR POSITIONING WITH STEPPER MOTORS |
| JPH0655037B2 (en) * | 1983-07-15 | 1994-07-20 | シャープ株式会社 | Servo motor speed control method |
| DE3401461A1 (en) * | 1984-01-17 | 1985-07-25 | Siemens AG, 1000 Berlin und 8000 München | Digitally controlled positioning arrangement |
| EP0189732B1 (en) * | 1985-01-29 | 1991-12-18 | Asgalium S.A. | Driving device for an electric motor with permanent magnetized rotor |
| US4618808A (en) * | 1985-01-30 | 1986-10-21 | International Business Machines Corporation | Electromagnetic actuator system using stepper motor with closed loop position sensing, electronic commutation and dynamic position and anomaly correction |
| DD235534A1 (en) * | 1985-03-14 | 1986-05-07 | Robotron Bueromasch | ARRANGEMENT FOR THE FAST POSITIONING OF A STEPPER MOTOR |
| NL8501027A (en) * | 1985-04-09 | 1986-11-03 | Philips Nv | MAGNETIC TAPE DEVICE. |
| JPH0268342U (en) * | 1988-11-15 | 1990-05-23 | ||
| CN108233801B (en) * | 2016-12-14 | 2021-01-15 | 中国航空工业集团公司北京航空精密机械研究所 | Method for realizing function of stepping motor by using servo motor |
Family Cites Families (9)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3444447A (en) * | 1966-09-22 | 1969-05-13 | Mesur Matic Electronics Corp | Multi-phase step motor control circuits including means for supplementing the normal energization of the windings |
| DE1958032C3 (en) * | 1969-11-19 | 1974-11-07 | Erc Electronic Research Corp., Basel (Schweiz) | Electric stepper motor |
| US3849714A (en) * | 1972-06-06 | 1974-11-19 | Ibm | Stepper motor control system |
| DD97789A1 (en) * | 1972-06-13 | 1973-05-14 | ||
| US3826966A (en) * | 1972-08-10 | 1974-07-30 | Yaskawa Denki Seisakusho Kk | Device for driving a stepping motor |
| DD113147A1 (en) * | 1974-08-29 | 1975-05-12 | ||
| DE2442688C2 (en) * | 1974-09-06 | 1982-06-16 | Siemens AG, 1000 Berlin und 8000 München | Arrangement for scanning a disk-shaped type carrier |
| US4025837A (en) * | 1975-06-30 | 1977-05-24 | International Business Machines Corporation | Adaptive control circuit for a stepping motor |
| US4137491A (en) * | 1977-09-14 | 1979-01-30 | Exxon Research & Engineering Co. | Stepper motor with analog positioning |
-
1980
- 1980-03-04 DE DE19803008289 patent/DE3008289C2/en not_active Expired
-
1981
- 1981-02-27 EP EP19810101448 patent/EP0035258B1/en not_active Expired
- 1981-03-03 CA CA000372191A patent/CA1175376A/en not_active Expired
- 1981-03-04 JP JP3109181A patent/JPS5910159B2/en not_active Expired
Also Published As
| Publication number | Publication date |
|---|---|
| DE3008289C2 (en) | 1982-06-24 |
| JPS5910159B2 (en) | 1984-03-07 |
| EP0035258B1 (en) | 1985-11-06 |
| DE3008289A1 (en) | 1981-09-10 |
| EP0035258A2 (en) | 1981-09-09 |
| EP0035258A3 (en) | 1982-05-26 |
| JPS56139099A (en) | 1981-10-30 |
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Legal Events
| Date | Code | Title | Description |
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| MKEX | Expiry |