CA1111903A - Apparatus for generating stepping motor pulses - Google Patents
Apparatus for generating stepping motor pulsesInfo
- Publication number
- CA1111903A CA1111903A CA300,884A CA300884A CA1111903A CA 1111903 A CA1111903 A CA 1111903A CA 300884 A CA300884 A CA 300884A CA 1111903 A CA1111903 A CA 1111903A
- Authority
- CA
- Canada
- Prior art keywords
- pulses
- stepping
- motor
- store
- deceleration
- 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
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Classifications
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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
- G05B19/40—Open loop systems, e.g. using stepping motor
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- Engineering & Computer Science (AREA)
- Human Computer Interaction (AREA)
- Manufacturing & Machinery (AREA)
- Physics & Mathematics (AREA)
- General Physics & Mathematics (AREA)
- Automation & Control Theory (AREA)
- Control Of Stepping Motors (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE
This invention relates to a circuit arrangement for generating stepping pulses for driving a stepping motor. The circuit arrangement generates stepping pulses by means of which, unlike prior art arrangements, a movement of the stepping motor in the optimum load angle range can be achieved. The stepping pulses are formed by means of several start pulses in short succession and a plurality of control pulses which are emitted whenever the rotor of the stepping motor has rotated by one stepping angle.
In this fashion the stepping motor is accelerated by the maximum dynamic torque. The stepping pulses are produced by means of a read-only memory (coefficient store), wherein data items coordinated with a particular characteristic have been stored. The data items determine the division ratio of a frequency divider which produces the stepping pulses from timing pulses of a predetermined repetition frequency.
This invention relates to a circuit arrangement for generating stepping pulses for driving a stepping motor. The circuit arrangement generates stepping pulses by means of which, unlike prior art arrangements, a movement of the stepping motor in the optimum load angle range can be achieved. The stepping pulses are formed by means of several start pulses in short succession and a plurality of control pulses which are emitted whenever the rotor of the stepping motor has rotated by one stepping angle.
In this fashion the stepping motor is accelerated by the maximum dynamic torque. The stepping pulses are produced by means of a read-only memory (coefficient store), wherein data items coordinated with a particular characteristic have been stored. The data items determine the division ratio of a frequency divider which produces the stepping pulses from timing pulses of a predetermined repetition frequency.
Description
The inYention relates to an apparatus for ~enerating stepping pulses fo~ driying a stepping motor.
Stepping pulse generators are'known in which a frequency divider is provided which is supplied with timing pulses of a preaetermined repetition frequency and which emits the stepping pulses whose relevant repetition frequency is equal to the repetition frequency of the timing pulses divided by adjustable factors, and wherein a counting ,-^~ stage is provided which, during the acceleration and deceleration of the stepping motor is caused by counting pulses to count upwards and downwards respectively, and which emits in accordance with its particular count numerical words to control the division factor of the frequency divider~
The publication "Celerate the Digital Stepping Motor", Electronic Design 1, 4 Jan. 1973, pages 84 to 87 has already disclosed a circuit arrangement for producing stepping pulses ior driving a stepping motor. m is circuit arrangement contains a frequency divider whose input is supplied with timing pulses of a predetermined repetition frequency and which emits the stepping pulses at its output.
The repetition frequency of the stepping pulses is equal to the repetition frequency of the timing pulses multiplied by a factor which is normally lower than 1. The factor is in each case determined by a data word which is fed to the frequency di~ider. The circuit arrangement further contains a counter ~hich is caused to count upwards or downwards by counting pulses' of a predetermined repetition freguency.
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The counter emits data words fxom its output, During the acceleration o~ the stepping motor r the counter is &aused to count upwards from an initial count to an end count by means of the counting pulses whose repetition frequency is considerably lower than that of the timing pulses. In dependence upon the relevant count of the counting state, due to the changing value of the data words, the repetition frequency of the stepping pulses constantly increases.
When the counting stage has reached its end count, further counting is prevented and the repetition frequency of the stepping pulses is no longer changed. During the deceleration of the stepping motor, the counting stage is again caused to count downwards by means of the counting pulses.
Similarly as in the case of the acceleration of the stepping motor, the repetition frequency of the stepping ~ulses is thus again reduced in dependènce upon the relevant count.
~cwn B The ~ne~ circuit arrangement can serve to set the repetition frequency of the stepping pulses in such manner that during the acceleration and deceleration of the stepping motor, it changes linearly, logarithmically or exponentially.
However, in this case the stepping motor is not operated in the optimum load angle range. If stepping moto~s are used for positioning drive means, it is frequently necessary, however, for the setting time to be as short as possible.
Ihe shorter the setting time is, the greater the torque of the stepping motor. The torque is dependent not only upon the properties of the stepping motor but also upon its mode , .:
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of operation. In the ~nown circuit arrangement, the repetition frequencies of the stepping pulses change sym~etrically during the acceleration and deceleration of the stepping motor. However, for specific applications it can be expedient to employ different, in particular asymmetrical time curves of the repetition frequencies of the stepping pulses.
Therefore an aim of the invention is to provide an apparatus by means of which arbitrary time curves of the repetition frequencies of the stepping pulses can be produced.
In accordance with the invention, there is provided an apparatus for generating stepping pulses for driving a stepping motor, comprising a variable frequency pulse generator for provid-ing the stepping pulses, a store having storage locations in which can be stored a plurality of data words, the store being addressable to supply a selected data word to the pulse generator for control of the repetition rate thereof, a counter arranged to supply addresses for the store, and means for supplying count pulses to the counter whereby successive data words are, in use, fed to the pulse generator for providing a desired acceleration or deceler-ation of the motor, the variable frequency pulse generator compris-ing a timing pulse generator and a divider arranged, in use, to divide the frequency of the timing pulses by a factor dependent on the data word fed to the generator, the counter comprising an up/
down counter which, in use, counts in one direction for acceleration of the motor and in the other direction for deceleration, the data words stored in the store being such as to provide, for acceleration of the motor, stepping pulses comprising start pulses followed by control pulses, the repetition rate of the start pulses being -4 ~
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greater than the initial repetition rate o~ the control pulsesl the sto:re containing two sets of data words addressable by the same add:resses, and means for selecting the one or the other set whereby dif:Eerent pulse sequences may be obtained during the acceleration and the deceleration.
This apparatus thus enables arbitrary acceleration and deceleration characteristics for the stepping mDtor to be set up in a simpler manner. The acceleration characteristic can, for example, be set in such manner that ':~
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gl~'3 during the entire setting motion the step~ing motor operates in the desired load angle range and setting can be carried out in a short length of time even when only al few steps are available. The theoretically possible power output of the stepping motor can in this way be satisfactorily exploited. In addition, the apparatus can be relatively simple and is particularly suitable, for exa.mple, for production as integrated circuit.
~-- Preferably the variable frequency pulse generator comprises a timing pulse generator and a divider arranged, in use, to divide the frequency of the timing pulses by a factor dependent on the data word fed to the generator.
In a preferred arrangement the counter is an up/
down counter which, in use, count~ in one direction ~or acceleration of the motor and in the other direction for deceleration.
Preferably the data words stored in the store are such as to provide, for acceleration of the motor, f"''`'`
~~ stepping pulses comprising at least one start pulse followed by control pulses.
If the stepping motor is designed in such manner that an odd number s of steps corresponds to hal~ a period of the static torque characteristic, it is advantageous or the number of start pulses to be equal to (s+l)/2.
For rapid setting of the dynamic torque, the repetition frequency of the start pulses is preferably considerably greater than the repetition frequency of the _5_ ~ ., .
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19~3 control pulses ~t the be~innin~ of the acceleration.
For xapid decleration process of the steppin~ motor, it is prefera~le for the deceleration process of the stepping ;motor to be introduced ~y a number of stepping pulses which bring the stepping motor directly into the negative load angle range.
An asymmetrical characteristic, i.e. a different characteristic during acceleration and deceleratior. may be ~--. achieved in a simple fashion if the data words emitted during acceleration differ from the data words emitted during the decleration when the same numerical words are applied.
In order to achieve different data words during the acceleration and deceleration when the same numerical words are applied from the counter, it is expeLient for the store to contain a change-over switch which, during the acceleration and deceleration of the stepping motor switches through the data words assigned to the acceleration and deceleration respectively to the frequency divider.
If the content of the store does not need to be changed, it is possible to provide a fixed word store as store.
If the duration of the deceleration of the stepping motor is shorter than that of the accelera~ion and thus fewer words are required for the deceleration than for the acceleration, the counting stage may be set at the beginning of the deceleration to a count which is equal to a predetermined fraction o~ the count reached prior to the , . ~ , .
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deceleration, The circuitry outlay is particularly low if the counting stage can be set to half the count reached prior to t~e deceleration of the stepping motor.
In order to achieve a characteristic which is independent of the absolute values of the repetition frequency of the stepping pulses, during the acceleration and decelera-tion of the stepping motor, it is advantageous for the counting stage to be supplied with the stepping pulses as ~-~ counting pulses.
With the motor connected to a load, preferably the data words stored in the store are such as to provide, for acceleration of the motor, at least one start pulse followed hy control pulses timed such that each control pulse after the first occurs after rotation of the motor by substantially one stepping angle.
In the following an exemplary embodiment of the circuit arrangement will be explained in detail making reference to the accompanying drawings in which ;-( Figure 1 is a time diagram of the angular speed of a stepping motor and of the stepping pulses fed thereto;
Figure 2 shows a curve of the static torque characteristic of the motor;
Figure 3 is a time diagram of the angle of rotation during the acceleration of the stepping motor;
Figure 4 is a block circuit diagram of one embodiment of the apparatus according to the ~resent in~ention;
Figure 5 is a circuit diagram of a frequency divider _ 7 _ . . . .
13 ~1~3 and of a change~oYer switch arranged in a store of the apparatus of figure 4, and Figure 6 is a circuit diagram of the counting stage of the apparatus of figure 4.
In the time diagram illustrated in figure 1, the time t is represented on the abscissa and the instantaneous values of stepping pulses SI produced by the apparatus and o~ the angular speed ~ of a stepping motor fed thereby are represented on the ordinate. Between ~he times tO and tl, the stepping motor is accelerated from a rest position to an angular speed ~s. Initially two start pulses occur as stepping pulse~, which are followed by three control pulses.
The repetition frequency of the start pulses is selected to be such that it is considerably greater than the repetition frequency of the control pulses at the beginning -of the acceleration. At the time tl, the angular speed of the stepping motor has reached its theoretical value ~a s and a plurality of control pulses of equal repetition frequency `~ are emitted.
Between the times t2 and t3, the stepping motor is decelerated and the repetition frequency of the stepping pulses SI is reduced accordingly. An additional, negative stepping pulse after the time t2 directly sets the load angle range which is the optimum for the deceleration. If the stepping motor is driven via an amplifier by a ring counter, the direction of rotation of the ring counter is reversed for the tlme durlng whloh the negatlve stepplng pulse occurs.
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; , - , 1~ ~ i ~ 3 The direction of rotation is represented by d in figure 1.
A~ter the time t3~ the stepping motor comes to a halt in the ~orm of a damped oscillation.
Figure 2 illustrates the static torque characteristic S of a typical stepping motor. The load angle ~ is shown in the abscissa direction. A load angle is to be understood as the angle by which the shaft of the stepping motor rotates as a result of loading with a predetermined, static torque relative to the unloaded state, the magnetic stop location. In this case no control pulses are fed to the stepping motor. m e static torque relative to the holding moment MH is plotted in the ordinate direction. Hexe the holding moment is to be understood as the maximum torque with which an excited stepping motor can be statically loaded without resulting in continuous rotation. The following observations are based on the assumption that the torquP characteristic is in the form of a sinusoidal cur~e.
f ~- m e dy~amic torque of the stepping motor is determined from the static torque characteristir. Here the dynamic torque is to be understood as the average torque which is available on the motor shaft during the course of a rotation by an angle a~ . Here it has been assumed that each control pulse is triggered precisely following a rotation by one step. It can be seen from the torque characteristic that in the event of a rotation by the stepping angle ~ the stepping motor produces its maximum dynamic torque Mmax - .
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wheneyer the load angle ~etween t~o control pulses is symmetrical to the peak value, the holding moment MH~ By simple calculation, the maximum dynamic torque is found to be Mmax = p oc 2 sin P 2 and the minimum dynamic torque Mmin ~ p-cc. [1 - cos pcc]
where p is the number of pole pairs of the stepping motor and ~ is the stepping angle.
In investigating the manner in which the repetition frequency of the control pulses and the angle of rotation of the rotor of the stepping motor change as a function of time when a constant, dynamic torque M is to be constantly produced at the motor shaft, it is established that when the stepping motor is started from the magnetic stop location, a run-up occurs in the form of a uniformly accelerated mo~ement when the repetition frequency f follows the equation C. f = MmJ1n . ~ . t where J represents the total moment of inertia of the motor load.
I~, in contrast, the repetition frequency f increases to a lesser extent, in the time between two control pulses the rotor does not rotate through the angle ~ so ~hat the condition of oonstant torque is no longer fulfilled.
If the repetition frquency f rises linearly but more rapidly, it can occur that after a few. control pulses - . . - -- ~ , . .
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the motor falls out of action and becomes stationary as then the load angle ~ in the static torque chzractexistic passes into the unstable equilibrium region.
In the event of a linear rise in the repetition frequency f, the acceleration capacity provided by the stepping motor is not fully exploited as the difference between the minimum and maximum dynamic torque can be very great. Basically it is possible to accelerate the stepping motor with a repetition frequency f of the control pulses SI of Mmax ~ = J . cc . t but this repetition frequency represents the theoretical critical maximum situation and this repetition frequency f cannot be exceeded.
If only a very few steps are available for the run-up of the stepping motor, a linear increase in the repetition frequency f is no longer satisfactory or, due to the small number of steps, no longer possible. In this case it is no longer expedient to allow the repetition frequency f to rise in aocordance with a monotonously increasing function, but it should be arranged that the load angle is brought as rapidly as possible into the optimum operating range which is governed by the equation 2p ~ ~~ 2p ~ 2 In the time diagram shown in figure 3, the load angle ~ is brought as rapidly as possible into the optimum operating range in that~ at the times tO' and tl', initially . ,',, ' - . ' .' ~ :
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two start pulses are emitted at a short interYal. The ~nteryal of tLme is 50 short that the rotor of the stepping motor has not rotated or has rotated only very slightly during this time in comparison to the size of a step. The number n of these directly consecutive start pulses must be such that the load angle ~ 1 = ~ + C~
is reached either exactly or approximately so that n ~ 2~
where n is a whole number. At the latest following the arrival of n+l start pulses, at the time t2' the run-up of the stepping motor takes place with the greatest possible acceleration moment Mmax. In the time diagram the angle of rotation ~ has been shown in the ordinate dlrection relative to the stepping angle CC . Also shown are the stepping pulses SI whlch are formed at the times t0' and tl' from start pulses and following the time t2l from control pulses.
The repetition frequency f of the stepping pulses has : (; also been shown. It can be seen from the time diagr2m that the repetition frequency of the start pulses is considerably greater than the repetition frequency of the following control pulses.
If, in accordance with the torque characteristic illustrated in figure 2, an odd number s of steps is required in order to pass through a half period of the static torque characteristic, the equals sign can be used in the last equation so that the number n of start pulses can be .
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~ 9 determined from the equation n - oC' (~ ~ ~ = 5+1 All the further control pulses are produced whenever the rotor of the stepping motor has rotated on average by the stepping angle qC. The motor then runs up with uniform acceleration with the torque Mmax.
- If for example a four-pole motor (p=21 having a three-line winding is provided, and the stepping angle amounts ~- - to oC=30, the number of the start pulses is thus n=2. At .._ the beginning of the run-up~ two start pulses are consequently triggered, This situation is illustrated in figure 3.
If the number s is even, the number n is determined in accordance with the equation '~ ' S
n=~ . 2 ~ 2 .
In contrast to the situation in which s is odd, the first following control pulse is triggered as soon as the rotor has rotated by half a stepping angle. All the further control pulses are emitted in such manner that the torque Mmax is reached. The stepping motor then operates in the optimum load angle range.
qhus the stepping motor in which s is an even number can be accelerated in the same way as a stepping motor for which the value s is odd from the start with the greatest possible torque ~max.
The same facts apply to the deceleration of the st~pping motor, which can be considered as negative acceleration, as to the acceleration itself. In this case . . .
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the optimum load angle can be set in that either a number of stepping pulses is omitted or a num~er of negatiye stepping pulses is emitted. The stepping pulses SI normally control a ring counter which is arranged in a motor amplifier and with the aid of which the individual windings of the stepping motor are driven. If the ring counter is normally advan~ed in a positive direction, in the event of deceleration it is advanced in a negative direction by the negative stepping pulses. In this way, the deceleration of the stepping motor likewise takes place with the maximum torque Mmax if the number of negative stepping pulses is selected to be such that the load angle ~ 2r +
is achieved as accurately as possible.
Figure 4 illustrates one embodiment of apparatus for the production of stepping pulses for driving a stepping motor in a teleprinter for the control of the carriage return. The carriage return needs to be carried out in the shortest possible time and the repetition frequency of the stepping pulses must consequently ~e as high as possible. The movement of the carriage during the return motion is composed of three sections, namely the acceleration, movement at constant speed, and deceleration. A carriage return command which is triggered for example by the closure of a switch SWl sets the carriage return in motion. me switch SWl feeds a signal Sl assigned to the carriage return command to a frequency divider FT. SW2 is a limit switch which shuts off the system at the end of the carriage return.
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r~he frequenc~ diyider FT is sup~lied with tLming pulses T
produced in a pulse yenerator TG, From its output~ the ~Ere~uency divider FT emits stepping pulses SI which are iEed via an amplifier stage V to a stepping motor SM. me repetition frequency of the stepping pulses SI is equal to the repetition frequency of the timing pulses T, divided by a factor. The factor is indicated by a data word DW
which is likewise fed to the inputs of the frequency divider FT.
The data words DW are stored in a store SP which may for example be a fixed word store~ me addressing of the data words DW in the store SP is effected with numerical words ZW which are fed to the store SP from a counting stage ZS. The store SP contains an address decoder AD which produces signals, assigned to the numexical words ZW for addressing the data words in the store SP. The store SP further contains a change-over switch UM which, under the control of a signal S3 emitted by a switch SW3, ~_ assumes a first or second position in which data words assigned to the acceleration and deceleration respectively of the stepping motor are read out from the store SP.
The data words assi~ned to the acceleration of the stepping motor are assembled in an acceleration programme BP, and the data words DW assigned to the deceleration are assembled in a deceleration programme VP. The operation of the apparatus arrangement will be explained with reference to the time diagram illustrated in figure 1.
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At the time tOr a carriage return command is txiggered b~ the closure o~ the switch SWl. The switch SWl emits the s~gnal Sl to the fre~uency divider FT and releases the latter. The switches SW2 and SW3 are open and the change-over switch UM controlled by the signal S3 occupies the position represented in a continuous line in figure 4.
The counting stage ZS has the count 0 and emi~s a numerical word ZW assigned to this count to the store SP. The C address decoder AD calls up the data words DW stored under the address 0 in the store~ although only the data word ~W contained in the acceleration programme is read out via the change-over switch UM and fed to the input of the frequency divider FT.
The frequency divider FT contains a counter which counts upwards from a variable starting count, which can be indicated by the data word DW, to a fixed end count.
When the end count has been reached, the frequency divider FT emits a stepping pulse SI and resets the starting count to the value indicated by the data word DW.
m e signal S3 sets the counting stage ZS in such a way that it counts upwards when the switch SW3 is open, thus during acceleration. The countin~ stage ZS is supplied with the stepping pulses SI as counting pulses. Following the first stepping pulse SI (a start pulse) emitted by the frequency divider FT, the count of the counting stage ZS
is increased by one unit and a corresponding numerical word ZW is emitted to the store SP. In dependence upon this 111~.~
numexical word Z~ the store SP emit~ a new data word DW
to the frequenc~ diyider FT and thus t~e repetition frequency of thestepping pulses is changed in dependence upon the new data word.
The data words DW assigned to the repetition frequencies f of the stepping pulses SI are stored in the store SP. The data words DW form a control programme which determines the angle speed of the stepping motor SM. In order to achieve a time curve of the repetition frequency f of the stepping pulses SI corresponding to figure 1 or figure 3, the data words DW assigned to the two start pulses have a high value, to obtain a high repetition rate, and the data words DW assigned to corresponding control pulses have values which are proportional to the intervals of time between the control pulses.
It will be assumed that the counting stage ZS initially has the count 0. The counting stage ZS feeds the store with an address word AD which reads out and feeds the frequency divider FT with the data word which is stored under the address 0 in the store SP and which is assigned to the first start pulse. When, at the time tO, the first start pulse is emitted as stepping pulse SI, the count of the counting stage - ZS is also increa~ed by 1. m e new address word AD reads out from the store SP the data word DW assigned to the second start pulse. The counting stage ZS is advanced correspondingly b~ the stepping pulses SI and the data words DW assigned to the control pulses are read out and fed to .. . . . ..
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~3 the frequency diyider FT. The repetition frequency of the stepping pulses SI is changed in accordance with t~e data words DW so that the time curve illustrated in figure 1 and figure 3 is reached.
With each stepping pulse SI, the counting stage ZS
is increased ~y one counting unit and at the time tl reaches a predetermined, maximum count. m is count is recognised by the address decoder AD in the store SP, and the store SP emits a signal S4 to the counting stage ZS which prevents ~' further upwards counting. Thus between the times tl and t2 there is no change in the numerical word Z~ and the same data word DW is always emitted from the store SP. Thus the repetition frequency of the stepping pulses SI remains constant and i5 contrived to be such that it is assi~ned to the maximum speed of the stepping motor SM.
Thus the carriage of the teleprinter reaches its which maximum speed at the time tl/it maintains unttl, at the time t2, in the vicinity of the left-hand stop, the carriage itself closes the switch SW3 in order to initiate the deceleration of the stepping motor SM.
With the closure of the switch SW3, the signal S3 brings the change-over switch UM into the position shown in broken lines in figure 4, and the counting stage ZS is set in such manner that it counts downwards. With the following stepping pulses SI, the count in the counting stage ZS is in each case reduced ~y one unit and similarly as between the times tO and tl, between the times t2 and t3 different :: :
' data words D~ in accordance with the desired deceleration characteristic are read out from the stoLe SP, ~oweYer~
due to the different position of the change-over switch UM, now the data words DW stored in the deceleration programme VP are read out and the repetition frequency of the stepping pulses SI is reduced in accordance with the deceleration cha acteristic.
At the time t3, shortly before the left~hand stop of the carriage of the teleprinter, the counting stage ZS
again reaches the count 0 and the address decoder AD emits a signal S5 which recognises this count 0 and prevents further downwards counting o~ the counting stage ZS. In the store SP, a data word DW assigned to a low repetition freq~ency of the stepping pulses SI can be stored under the address 0. As the count of the counting stage ZS
does not change, similarly as between the times tl and t2 the same data word DW is always read out from the store SP and the carriage of the teleprinter then.continues --to move at .a cons.tant, low speed, in contrast to the time diagram illustrated in figure 1.
When the carriage of the teleprinter reaches the left-hand stop and closes the switch SW2, a signal S2 emitted from the switch SW2 blocks the frequency divider FT and no further stepping pulses SI are emitted. At the same time the stepping motor SM stops.
If the acceleration characteristic and deceleration characteristiC are symmetrical, only one single programme is ' ' ~' ' : ' ' .
g~3 .required in the stoxe S~ and it is possible to dispense with the ch~nge~oYex S~itch UM. In this caset independently of the acceIeration or deceleration, the numerical words ZW are always assigned the same data words.
If, however, the deceleration of the stepping motor requires a shorter length of time, at the beginning of the acceleration the counting stage ZS can be set at a count which is equal to the number o data words required for the representation of the deceleration characteristic.
If, for example, ~he counting stage ZS rPaches the count 63 as the maximum count at the time t2, and the deceleration of the stepping motor has a duration which is only half of the acceleration, at the time t2 the counting stage can be set ~t the value 31. In this case the deceleration is terminated already after 31 stepping pulses SI and thus the deceleration characteristic has a considerably steeper gradient.
The circuit diagram in figure 5 illustrates the construction of the frequency divider FT and that of the change-ovex switch UM in the store SP.
The frequency divider FT contains a counter ZAl, two AND-gates Ul and U2 and a flip-flo~ Fl. The counter ZAl is designed, for example, as eight-stage counter. The siynal Sl sets the flip-flop Fl, and the signal at the output of the flip-flop Fl releases the AND-gate Ul which switches through the timing pulses T to the counter ZAl.
Commencing from a starting count, the count of the counter -~0--.
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~ 3 ZAl is increased b~ one unit with each timing pulse T, When the counte~ ZAl has xeached the count 254, the ~ND~
gate U2 emits a stepping pulse SI which is on the one hand fed via the amplifier stage V to the step~ing motor SM and on the other hand to the setting input of the counter ZA1. On the occurrence of the stepping pulse SI, the counter ZA1 is set to a starting count which is indicated by the signals DWl to DW8 assigned to the relevant data word DW. The higher the value of the data word, the more rapidly does the counter ZAl reach the count 254, and consequently the higher is the repetition frequency of the stepping pulses SI.
At the end of the carriage return, the signal S2 resets the flip-flop Fl. The signal at t~e output of the flip-flop Fl blocks the AND-gate Ul and no further timing pulses T are switched through to the counter ZAl so that the latter is blocked and emits no furt~er stepping pulses SI to the stepping motor.
The change-over switch UM arranged in the store SP
contains eight AND/OR-gates U01 to U08, and one fliprflop F2. At the beginning of the carriage return, the signal Sl sets the flip-flop F2, and consequently the signal at the non-inverting output o~ the flip-flop F2 releases the l~ft-hand AND-gates in the AND/OR-gates U01 to U08. Thus the ~ 25 data words which have been assembled in the acceleration A programme BP and which are represented by the signals BPl to BP8 are switched through to the frequency divider FT by . .
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.-. ~ 3 the signals DWl to DW8 emitted at the outputs of the AND/
OR-gates U0.1 to U08~ At the beginning of the deceleration of the stepping motox, the signal S3 resets the flip-flop :F2, and the signal at the inverting output of the flip-flop F2 releases the relevant right-hand AND-gates in the AND/OR-gates U0l to U08, whereas the left-hand AND-gates in the AND/OR~gates U0l to U08 are simultaneously blocked. Consequently, during the deceleration, the data words which have been assembled in the deceleration ~rogramme VP and are represented by the signals VPl to VP8 are swtiched through to the frequency divider FT by the signals DWl .to DW8 emitted from the output of the AND/OR-gates U01 to U08.
The counting sta~Je ZS illustrated in figure 6 contains a counter ZA2, a AND-gate U3, a NOR-gate N and a flip-flop F3 which can be the same device as the flip-flop ~ F2. At the beginning of the acceleration of the stepping ; motor, the signal Sl sets the flip-flop F3, and the signal at the output of the flip-flop F3 sets the counter ZA2 in such manner that it is caused to count upwards by the stepping pulses SI emitted via the AND-gate U3. The counter ZA2 i8 designed, for example, as a six-stage counter and counts from the count 0 to the end count 63. When the counter has reached the coun. 63, the address decoder AD emits the signal S4 and the AND-gate U3 is blocked via the NOR-gate N so that no ~urther stepping pulses SI reach the counting inputo~ the counter ZA2.: At the beginning of the deceleration ..
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of the stepping motor~ the signal S3 resets the flip-flop :F3 and thus sets the counter ZA2 in such manner that it is causea to count downwards by the stepping ~ulses SI.
:Furthermore, the signal S3 sets the counter ZA2 at a starting count which is equal to a fraction of the maximum count 63, for example to t~e starting value 31.
This is achieved in a particularly simple manner in that the outputs of the counter ZA2 are connected to the setting inputs, each displaced by one position towards the left, of the counter ZA2. When the counter ZA2 has reached its starting count O, the address decoder AD in the store SP emits the signal S5 and the AND-gate U3 is blocked again so that no further stepping pulses reach the counting input of the counter ZA2. In order to prevent a self-obstruction of the counter ZA2 due to the blockage of the AND-gate U3 by the signals S4 and S5, the signal S4 is discontinued as soon as the counter ZA2 counts downwards and the signal S5 is discontinued as soon as the counter ZA2 counts u~wards.
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Stepping pulse generators are'known in which a frequency divider is provided which is supplied with timing pulses of a preaetermined repetition frequency and which emits the stepping pulses whose relevant repetition frequency is equal to the repetition frequency of the timing pulses divided by adjustable factors, and wherein a counting ,-^~ stage is provided which, during the acceleration and deceleration of the stepping motor is caused by counting pulses to count upwards and downwards respectively, and which emits in accordance with its particular count numerical words to control the division factor of the frequency divider~
The publication "Celerate the Digital Stepping Motor", Electronic Design 1, 4 Jan. 1973, pages 84 to 87 has already disclosed a circuit arrangement for producing stepping pulses ior driving a stepping motor. m is circuit arrangement contains a frequency divider whose input is supplied with timing pulses of a predetermined repetition frequency and which emits the stepping pulses at its output.
The repetition frequency of the stepping pulses is equal to the repetition frequency of the timing pulses multiplied by a factor which is normally lower than 1. The factor is in each case determined by a data word which is fed to the frequency di~ider. The circuit arrangement further contains a counter ~hich is caused to count upwards or downwards by counting pulses' of a predetermined repetition freguency.
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The counter emits data words fxom its output, During the acceleration o~ the stepping motor r the counter is &aused to count upwards from an initial count to an end count by means of the counting pulses whose repetition frequency is considerably lower than that of the timing pulses. In dependence upon the relevant count of the counting state, due to the changing value of the data words, the repetition frequency of the stepping pulses constantly increases.
When the counting stage has reached its end count, further counting is prevented and the repetition frequency of the stepping pulses is no longer changed. During the deceleration of the stepping motor, the counting stage is again caused to count downwards by means of the counting pulses.
Similarly as in the case of the acceleration of the stepping motor, the repetition frequency of the stepping ~ulses is thus again reduced in dependènce upon the relevant count.
~cwn B The ~ne~ circuit arrangement can serve to set the repetition frequency of the stepping pulses in such manner that during the acceleration and deceleration of the stepping motor, it changes linearly, logarithmically or exponentially.
However, in this case the stepping motor is not operated in the optimum load angle range. If stepping moto~s are used for positioning drive means, it is frequently necessary, however, for the setting time to be as short as possible.
Ihe shorter the setting time is, the greater the torque of the stepping motor. The torque is dependent not only upon the properties of the stepping motor but also upon its mode , .:
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of operation. In the ~nown circuit arrangement, the repetition frequencies of the stepping pulses change sym~etrically during the acceleration and deceleration of the stepping motor. However, for specific applications it can be expedient to employ different, in particular asymmetrical time curves of the repetition frequencies of the stepping pulses.
Therefore an aim of the invention is to provide an apparatus by means of which arbitrary time curves of the repetition frequencies of the stepping pulses can be produced.
In accordance with the invention, there is provided an apparatus for generating stepping pulses for driving a stepping motor, comprising a variable frequency pulse generator for provid-ing the stepping pulses, a store having storage locations in which can be stored a plurality of data words, the store being addressable to supply a selected data word to the pulse generator for control of the repetition rate thereof, a counter arranged to supply addresses for the store, and means for supplying count pulses to the counter whereby successive data words are, in use, fed to the pulse generator for providing a desired acceleration or deceler-ation of the motor, the variable frequency pulse generator compris-ing a timing pulse generator and a divider arranged, in use, to divide the frequency of the timing pulses by a factor dependent on the data word fed to the generator, the counter comprising an up/
down counter which, in use, counts in one direction for acceleration of the motor and in the other direction for deceleration, the data words stored in the store being such as to provide, for acceleration of the motor, stepping pulses comprising start pulses followed by control pulses, the repetition rate of the start pulses being -4 ~
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greater than the initial repetition rate o~ the control pulsesl the sto:re containing two sets of data words addressable by the same add:resses, and means for selecting the one or the other set whereby dif:Eerent pulse sequences may be obtained during the acceleration and the deceleration.
This apparatus thus enables arbitrary acceleration and deceleration characteristics for the stepping mDtor to be set up in a simpler manner. The acceleration characteristic can, for example, be set in such manner that ':~
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gl~'3 during the entire setting motion the step~ing motor operates in the desired load angle range and setting can be carried out in a short length of time even when only al few steps are available. The theoretically possible power output of the stepping motor can in this way be satisfactorily exploited. In addition, the apparatus can be relatively simple and is particularly suitable, for exa.mple, for production as integrated circuit.
~-- Preferably the variable frequency pulse generator comprises a timing pulse generator and a divider arranged, in use, to divide the frequency of the timing pulses by a factor dependent on the data word fed to the generator.
In a preferred arrangement the counter is an up/
down counter which, in use, count~ in one direction ~or acceleration of the motor and in the other direction for deceleration.
Preferably the data words stored in the store are such as to provide, for acceleration of the motor, f"''`'`
~~ stepping pulses comprising at least one start pulse followed by control pulses.
If the stepping motor is designed in such manner that an odd number s of steps corresponds to hal~ a period of the static torque characteristic, it is advantageous or the number of start pulses to be equal to (s+l)/2.
For rapid setting of the dynamic torque, the repetition frequency of the start pulses is preferably considerably greater than the repetition frequency of the _5_ ~ ., .
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19~3 control pulses ~t the be~innin~ of the acceleration.
For xapid decleration process of the steppin~ motor, it is prefera~le for the deceleration process of the stepping ;motor to be introduced ~y a number of stepping pulses which bring the stepping motor directly into the negative load angle range.
An asymmetrical characteristic, i.e. a different characteristic during acceleration and deceleratior. may be ~--. achieved in a simple fashion if the data words emitted during acceleration differ from the data words emitted during the decleration when the same numerical words are applied.
In order to achieve different data words during the acceleration and deceleration when the same numerical words are applied from the counter, it is expeLient for the store to contain a change-over switch which, during the acceleration and deceleration of the stepping motor switches through the data words assigned to the acceleration and deceleration respectively to the frequency divider.
If the content of the store does not need to be changed, it is possible to provide a fixed word store as store.
If the duration of the deceleration of the stepping motor is shorter than that of the accelera~ion and thus fewer words are required for the deceleration than for the acceleration, the counting stage may be set at the beginning of the deceleration to a count which is equal to a predetermined fraction o~ the count reached prior to the , . ~ , .
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deceleration, The circuitry outlay is particularly low if the counting stage can be set to half the count reached prior to t~e deceleration of the stepping motor.
In order to achieve a characteristic which is independent of the absolute values of the repetition frequency of the stepping pulses, during the acceleration and decelera-tion of the stepping motor, it is advantageous for the counting stage to be supplied with the stepping pulses as ~-~ counting pulses.
With the motor connected to a load, preferably the data words stored in the store are such as to provide, for acceleration of the motor, at least one start pulse followed hy control pulses timed such that each control pulse after the first occurs after rotation of the motor by substantially one stepping angle.
In the following an exemplary embodiment of the circuit arrangement will be explained in detail making reference to the accompanying drawings in which ;-( Figure 1 is a time diagram of the angular speed of a stepping motor and of the stepping pulses fed thereto;
Figure 2 shows a curve of the static torque characteristic of the motor;
Figure 3 is a time diagram of the angle of rotation during the acceleration of the stepping motor;
Figure 4 is a block circuit diagram of one embodiment of the apparatus according to the ~resent in~ention;
Figure 5 is a circuit diagram of a frequency divider _ 7 _ . . . .
13 ~1~3 and of a change~oYer switch arranged in a store of the apparatus of figure 4, and Figure 6 is a circuit diagram of the counting stage of the apparatus of figure 4.
In the time diagram illustrated in figure 1, the time t is represented on the abscissa and the instantaneous values of stepping pulses SI produced by the apparatus and o~ the angular speed ~ of a stepping motor fed thereby are represented on the ordinate. Between ~he times tO and tl, the stepping motor is accelerated from a rest position to an angular speed ~s. Initially two start pulses occur as stepping pulse~, which are followed by three control pulses.
The repetition frequency of the start pulses is selected to be such that it is considerably greater than the repetition frequency of the control pulses at the beginning -of the acceleration. At the time tl, the angular speed of the stepping motor has reached its theoretical value ~a s and a plurality of control pulses of equal repetition frequency `~ are emitted.
Between the times t2 and t3, the stepping motor is decelerated and the repetition frequency of the stepping pulses SI is reduced accordingly. An additional, negative stepping pulse after the time t2 directly sets the load angle range which is the optimum for the deceleration. If the stepping motor is driven via an amplifier by a ring counter, the direction of rotation of the ring counter is reversed for the tlme durlng whloh the negatlve stepplng pulse occurs.
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; , - , 1~ ~ i ~ 3 The direction of rotation is represented by d in figure 1.
A~ter the time t3~ the stepping motor comes to a halt in the ~orm of a damped oscillation.
Figure 2 illustrates the static torque characteristic S of a typical stepping motor. The load angle ~ is shown in the abscissa direction. A load angle is to be understood as the angle by which the shaft of the stepping motor rotates as a result of loading with a predetermined, static torque relative to the unloaded state, the magnetic stop location. In this case no control pulses are fed to the stepping motor. m e static torque relative to the holding moment MH is plotted in the ordinate direction. Hexe the holding moment is to be understood as the maximum torque with which an excited stepping motor can be statically loaded without resulting in continuous rotation. The following observations are based on the assumption that the torquP characteristic is in the form of a sinusoidal cur~e.
f ~- m e dy~amic torque of the stepping motor is determined from the static torque characteristir. Here the dynamic torque is to be understood as the average torque which is available on the motor shaft during the course of a rotation by an angle a~ . Here it has been assumed that each control pulse is triggered precisely following a rotation by one step. It can be seen from the torque characteristic that in the event of a rotation by the stepping angle ~ the stepping motor produces its maximum dynamic torque Mmax - .
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wheneyer the load angle ~etween t~o control pulses is symmetrical to the peak value, the holding moment MH~ By simple calculation, the maximum dynamic torque is found to be Mmax = p oc 2 sin P 2 and the minimum dynamic torque Mmin ~ p-cc. [1 - cos pcc]
where p is the number of pole pairs of the stepping motor and ~ is the stepping angle.
In investigating the manner in which the repetition frequency of the control pulses and the angle of rotation of the rotor of the stepping motor change as a function of time when a constant, dynamic torque M is to be constantly produced at the motor shaft, it is established that when the stepping motor is started from the magnetic stop location, a run-up occurs in the form of a uniformly accelerated mo~ement when the repetition frequency f follows the equation C. f = MmJ1n . ~ . t where J represents the total moment of inertia of the motor load.
I~, in contrast, the repetition frequency f increases to a lesser extent, in the time between two control pulses the rotor does not rotate through the angle ~ so ~hat the condition of oonstant torque is no longer fulfilled.
If the repetition frquency f rises linearly but more rapidly, it can occur that after a few. control pulses - . . - -- ~ , . .
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the motor falls out of action and becomes stationary as then the load angle ~ in the static torque chzractexistic passes into the unstable equilibrium region.
In the event of a linear rise in the repetition frequency f, the acceleration capacity provided by the stepping motor is not fully exploited as the difference between the minimum and maximum dynamic torque can be very great. Basically it is possible to accelerate the stepping motor with a repetition frequency f of the control pulses SI of Mmax ~ = J . cc . t but this repetition frequency represents the theoretical critical maximum situation and this repetition frequency f cannot be exceeded.
If only a very few steps are available for the run-up of the stepping motor, a linear increase in the repetition frequency f is no longer satisfactory or, due to the small number of steps, no longer possible. In this case it is no longer expedient to allow the repetition frequency f to rise in aocordance with a monotonously increasing function, but it should be arranged that the load angle is brought as rapidly as possible into the optimum operating range which is governed by the equation 2p ~ ~~ 2p ~ 2 In the time diagram shown in figure 3, the load angle ~ is brought as rapidly as possible into the optimum operating range in that~ at the times tO' and tl', initially . ,',, ' - . ' .' ~ :
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two start pulses are emitted at a short interYal. The ~nteryal of tLme is 50 short that the rotor of the stepping motor has not rotated or has rotated only very slightly during this time in comparison to the size of a step. The number n of these directly consecutive start pulses must be such that the load angle ~ 1 = ~ + C~
is reached either exactly or approximately so that n ~ 2~
where n is a whole number. At the latest following the arrival of n+l start pulses, at the time t2' the run-up of the stepping motor takes place with the greatest possible acceleration moment Mmax. In the time diagram the angle of rotation ~ has been shown in the ordinate dlrection relative to the stepping angle CC . Also shown are the stepping pulses SI whlch are formed at the times t0' and tl' from start pulses and following the time t2l from control pulses.
The repetition frequency f of the stepping pulses has : (; also been shown. It can be seen from the time diagr2m that the repetition frequency of the start pulses is considerably greater than the repetition frequency of the following control pulses.
If, in accordance with the torque characteristic illustrated in figure 2, an odd number s of steps is required in order to pass through a half period of the static torque characteristic, the equals sign can be used in the last equation so that the number n of start pulses can be .
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~ 9 determined from the equation n - oC' (~ ~ ~ = 5+1 All the further control pulses are produced whenever the rotor of the stepping motor has rotated on average by the stepping angle qC. The motor then runs up with uniform acceleration with the torque Mmax.
- If for example a four-pole motor (p=21 having a three-line winding is provided, and the stepping angle amounts ~- - to oC=30, the number of the start pulses is thus n=2. At .._ the beginning of the run-up~ two start pulses are consequently triggered, This situation is illustrated in figure 3.
If the number s is even, the number n is determined in accordance with the equation '~ ' S
n=~ . 2 ~ 2 .
In contrast to the situation in which s is odd, the first following control pulse is triggered as soon as the rotor has rotated by half a stepping angle. All the further control pulses are emitted in such manner that the torque Mmax is reached. The stepping motor then operates in the optimum load angle range.
qhus the stepping motor in which s is an even number can be accelerated in the same way as a stepping motor for which the value s is odd from the start with the greatest possible torque ~max.
The same facts apply to the deceleration of the st~pping motor, which can be considered as negative acceleration, as to the acceleration itself. In this case . . .
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the optimum load angle can be set in that either a number of stepping pulses is omitted or a num~er of negatiye stepping pulses is emitted. The stepping pulses SI normally control a ring counter which is arranged in a motor amplifier and with the aid of which the individual windings of the stepping motor are driven. If the ring counter is normally advan~ed in a positive direction, in the event of deceleration it is advanced in a negative direction by the negative stepping pulses. In this way, the deceleration of the stepping motor likewise takes place with the maximum torque Mmax if the number of negative stepping pulses is selected to be such that the load angle ~ 2r +
is achieved as accurately as possible.
Figure 4 illustrates one embodiment of apparatus for the production of stepping pulses for driving a stepping motor in a teleprinter for the control of the carriage return. The carriage return needs to be carried out in the shortest possible time and the repetition frequency of the stepping pulses must consequently ~e as high as possible. The movement of the carriage during the return motion is composed of three sections, namely the acceleration, movement at constant speed, and deceleration. A carriage return command which is triggered for example by the closure of a switch SWl sets the carriage return in motion. me switch SWl feeds a signal Sl assigned to the carriage return command to a frequency divider FT. SW2 is a limit switch which shuts off the system at the end of the carriage return.
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r~he frequenc~ diyider FT is sup~lied with tLming pulses T
produced in a pulse yenerator TG, From its output~ the ~Ere~uency divider FT emits stepping pulses SI which are iEed via an amplifier stage V to a stepping motor SM. me repetition frequency of the stepping pulses SI is equal to the repetition frequency of the timing pulses T, divided by a factor. The factor is indicated by a data word DW
which is likewise fed to the inputs of the frequency divider FT.
The data words DW are stored in a store SP which may for example be a fixed word store~ me addressing of the data words DW in the store SP is effected with numerical words ZW which are fed to the store SP from a counting stage ZS. The store SP contains an address decoder AD which produces signals, assigned to the numexical words ZW for addressing the data words in the store SP. The store SP further contains a change-over switch UM which, under the control of a signal S3 emitted by a switch SW3, ~_ assumes a first or second position in which data words assigned to the acceleration and deceleration respectively of the stepping motor are read out from the store SP.
The data words assi~ned to the acceleration of the stepping motor are assembled in an acceleration programme BP, and the data words DW assigned to the deceleration are assembled in a deceleration programme VP. The operation of the apparatus arrangement will be explained with reference to the time diagram illustrated in figure 1.
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At the time tOr a carriage return command is txiggered b~ the closure o~ the switch SWl. The switch SWl emits the s~gnal Sl to the fre~uency divider FT and releases the latter. The switches SW2 and SW3 are open and the change-over switch UM controlled by the signal S3 occupies the position represented in a continuous line in figure 4.
The counting stage ZS has the count 0 and emi~s a numerical word ZW assigned to this count to the store SP. The C address decoder AD calls up the data words DW stored under the address 0 in the store~ although only the data word ~W contained in the acceleration programme is read out via the change-over switch UM and fed to the input of the frequency divider FT.
The frequency divider FT contains a counter which counts upwards from a variable starting count, which can be indicated by the data word DW, to a fixed end count.
When the end count has been reached, the frequency divider FT emits a stepping pulse SI and resets the starting count to the value indicated by the data word DW.
m e signal S3 sets the counting stage ZS in such a way that it counts upwards when the switch SW3 is open, thus during acceleration. The countin~ stage ZS is supplied with the stepping pulses SI as counting pulses. Following the first stepping pulse SI (a start pulse) emitted by the frequency divider FT, the count of the counting stage ZS
is increased by one unit and a corresponding numerical word ZW is emitted to the store SP. In dependence upon this 111~.~
numexical word Z~ the store SP emit~ a new data word DW
to the frequenc~ diyider FT and thus t~e repetition frequency of thestepping pulses is changed in dependence upon the new data word.
The data words DW assigned to the repetition frequencies f of the stepping pulses SI are stored in the store SP. The data words DW form a control programme which determines the angle speed of the stepping motor SM. In order to achieve a time curve of the repetition frequency f of the stepping pulses SI corresponding to figure 1 or figure 3, the data words DW assigned to the two start pulses have a high value, to obtain a high repetition rate, and the data words DW assigned to corresponding control pulses have values which are proportional to the intervals of time between the control pulses.
It will be assumed that the counting stage ZS initially has the count 0. The counting stage ZS feeds the store with an address word AD which reads out and feeds the frequency divider FT with the data word which is stored under the address 0 in the store SP and which is assigned to the first start pulse. When, at the time tO, the first start pulse is emitted as stepping pulse SI, the count of the counting stage - ZS is also increa~ed by 1. m e new address word AD reads out from the store SP the data word DW assigned to the second start pulse. The counting stage ZS is advanced correspondingly b~ the stepping pulses SI and the data words DW assigned to the control pulses are read out and fed to .. . . . ..
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~3 the frequency diyider FT. The repetition frequency of the stepping pulses SI is changed in accordance with t~e data words DW so that the time curve illustrated in figure 1 and figure 3 is reached.
With each stepping pulse SI, the counting stage ZS
is increased ~y one counting unit and at the time tl reaches a predetermined, maximum count. m is count is recognised by the address decoder AD in the store SP, and the store SP emits a signal S4 to the counting stage ZS which prevents ~' further upwards counting. Thus between the times tl and t2 there is no change in the numerical word Z~ and the same data word DW is always emitted from the store SP. Thus the repetition frequency of the stepping pulses SI remains constant and i5 contrived to be such that it is assi~ned to the maximum speed of the stepping motor SM.
Thus the carriage of the teleprinter reaches its which maximum speed at the time tl/it maintains unttl, at the time t2, in the vicinity of the left-hand stop, the carriage itself closes the switch SW3 in order to initiate the deceleration of the stepping motor SM.
With the closure of the switch SW3, the signal S3 brings the change-over switch UM into the position shown in broken lines in figure 4, and the counting stage ZS is set in such manner that it counts downwards. With the following stepping pulses SI, the count in the counting stage ZS is in each case reduced ~y one unit and similarly as between the times tO and tl, between the times t2 and t3 different :: :
' data words D~ in accordance with the desired deceleration characteristic are read out from the stoLe SP, ~oweYer~
due to the different position of the change-over switch UM, now the data words DW stored in the deceleration programme VP are read out and the repetition frequency of the stepping pulses SI is reduced in accordance with the deceleration cha acteristic.
At the time t3, shortly before the left~hand stop of the carriage of the teleprinter, the counting stage ZS
again reaches the count 0 and the address decoder AD emits a signal S5 which recognises this count 0 and prevents further downwards counting o~ the counting stage ZS. In the store SP, a data word DW assigned to a low repetition freq~ency of the stepping pulses SI can be stored under the address 0. As the count of the counting stage ZS
does not change, similarly as between the times tl and t2 the same data word DW is always read out from the store SP and the carriage of the teleprinter then.continues --to move at .a cons.tant, low speed, in contrast to the time diagram illustrated in figure 1.
When the carriage of the teleprinter reaches the left-hand stop and closes the switch SW2, a signal S2 emitted from the switch SW2 blocks the frequency divider FT and no further stepping pulses SI are emitted. At the same time the stepping motor SM stops.
If the acceleration characteristic and deceleration characteristiC are symmetrical, only one single programme is ' ' ~' ' : ' ' .
g~3 .required in the stoxe S~ and it is possible to dispense with the ch~nge~oYex S~itch UM. In this caset independently of the acceIeration or deceleration, the numerical words ZW are always assigned the same data words.
If, however, the deceleration of the stepping motor requires a shorter length of time, at the beginning of the acceleration the counting stage ZS can be set at a count which is equal to the number o data words required for the representation of the deceleration characteristic.
If, for example, ~he counting stage ZS rPaches the count 63 as the maximum count at the time t2, and the deceleration of the stepping motor has a duration which is only half of the acceleration, at the time t2 the counting stage can be set ~t the value 31. In this case the deceleration is terminated already after 31 stepping pulses SI and thus the deceleration characteristic has a considerably steeper gradient.
The circuit diagram in figure 5 illustrates the construction of the frequency divider FT and that of the change-ovex switch UM in the store SP.
The frequency divider FT contains a counter ZAl, two AND-gates Ul and U2 and a flip-flo~ Fl. The counter ZAl is designed, for example, as eight-stage counter. The siynal Sl sets the flip-flop Fl, and the signal at the output of the flip-flop Fl releases the AND-gate Ul which switches through the timing pulses T to the counter ZAl.
Commencing from a starting count, the count of the counter -~0--.
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~ 3 ZAl is increased b~ one unit with each timing pulse T, When the counte~ ZAl has xeached the count 254, the ~ND~
gate U2 emits a stepping pulse SI which is on the one hand fed via the amplifier stage V to the step~ing motor SM and on the other hand to the setting input of the counter ZA1. On the occurrence of the stepping pulse SI, the counter ZA1 is set to a starting count which is indicated by the signals DWl to DW8 assigned to the relevant data word DW. The higher the value of the data word, the more rapidly does the counter ZAl reach the count 254, and consequently the higher is the repetition frequency of the stepping pulses SI.
At the end of the carriage return, the signal S2 resets the flip-flop Fl. The signal at t~e output of the flip-flop Fl blocks the AND-gate Ul and no further timing pulses T are switched through to the counter ZAl so that the latter is blocked and emits no furt~er stepping pulses SI to the stepping motor.
The change-over switch UM arranged in the store SP
contains eight AND/OR-gates U01 to U08, and one fliprflop F2. At the beginning of the carriage return, the signal Sl sets the flip-flop F2, and consequently the signal at the non-inverting output o~ the flip-flop F2 releases the l~ft-hand AND-gates in the AND/OR-gates U01 to U08. Thus the ~ 25 data words which have been assembled in the acceleration A programme BP and which are represented by the signals BPl to BP8 are switched through to the frequency divider FT by . .
:
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.-. ~ 3 the signals DWl to DW8 emitted at the outputs of the AND/
OR-gates U0.1 to U08~ At the beginning of the deceleration of the stepping motox, the signal S3 resets the flip-flop :F2, and the signal at the inverting output of the flip-flop F2 releases the relevant right-hand AND-gates in the AND/OR-gates U0l to U08, whereas the left-hand AND-gates in the AND/OR~gates U0l to U08 are simultaneously blocked. Consequently, during the deceleration, the data words which have been assembled in the deceleration ~rogramme VP and are represented by the signals VPl to VP8 are swtiched through to the frequency divider FT by the signals DWl .to DW8 emitted from the output of the AND/OR-gates U01 to U08.
The counting sta~Je ZS illustrated in figure 6 contains a counter ZA2, a AND-gate U3, a NOR-gate N and a flip-flop F3 which can be the same device as the flip-flop ~ F2. At the beginning of the acceleration of the stepping ; motor, the signal Sl sets the flip-flop F3, and the signal at the output of the flip-flop F3 sets the counter ZA2 in such manner that it is caused to count upwards by the stepping pulses SI emitted via the AND-gate U3. The counter ZA2 i8 designed, for example, as a six-stage counter and counts from the count 0 to the end count 63. When the counter has reached the coun. 63, the address decoder AD emits the signal S4 and the AND-gate U3 is blocked via the NOR-gate N so that no ~urther stepping pulses SI reach the counting inputo~ the counter ZA2.: At the beginning of the deceleration ..
; -22-.
,' . . "
of the stepping motor~ the signal S3 resets the flip-flop :F3 and thus sets the counter ZA2 in such manner that it is causea to count downwards by the stepping ~ulses SI.
:Furthermore, the signal S3 sets the counter ZA2 at a starting count which is equal to a fraction of the maximum count 63, for example to t~e starting value 31.
This is achieved in a particularly simple manner in that the outputs of the counter ZA2 are connected to the setting inputs, each displaced by one position towards the left, of the counter ZA2. When the counter ZA2 has reached its starting count O, the address decoder AD in the store SP emits the signal S5 and the AND-gate U3 is blocked again so that no further stepping pulses reach the counting input of the counter ZA2. In order to prevent a self-obstruction of the counter ZA2 due to the blockage of the AND-gate U3 by the signals S4 and S5, the signal S4 is discontinued as soon as the counter ZA2 counts downwards and the signal S5 is discontinued as soon as the counter ZA2 counts u~wards.
~,;' .
-~23-. .
'`' ': . . ,,. : ~
, ~ , ., ,. . .. , . -.:
- .. .
.
.. ,, -:. . .
..
Claims (7)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. An apparatus for generating stepping pulses for driving a stepping motor, comprising a variable frequency pulse generator for providing the stepping pulses, a store having storage locations in which can be stored a plurality of data words, the store being addressable to supply a selected data word to the pulse generator for control of the repetition rate thereof, a counter arranged to supply addresses for the store, and means for supplying count pulses to the counter whereby successive data words are, in use, fed to the pulse generator for providing a desired acceleration or deceleration of the motor, the variable frequency pulse generator comprising a timing pulse generator and a divider arranged, in use, to divide the frequency of the timing pulses by a factor dependent on the data word fed to the generator, the counter comprising an up/down counter which, in use, counts in one direction for acceleration of the motor and in the other direction for deceler-ation, the data words stored in the store being such as to provide, for acceleration of the motor, stepping pulses comprising start pulses followed by control pulses, the repetition rate of the start pulses being greater than the initial repetition rate of the control pulses, the store containing two sets of data words addressable by the same addresses, and means for selecting the one or the other set whereby different pulse sequences may be obtained during the acceleration and the deceleration.
2. An apparatus according to claim 1, in which the store has separate outputs for the two sets of data words and the means for selecting comprises change-over switching means for selectively switching through the data words from one or other output to the frequency divider for acceleration or deceleration.
3. An apparatus according to claim 1, in which means are provided for, at the beginning of deceleration, setting the counter at a count which is equal to a predetermined fraction of the count reached prior to the deceleration.
4. An apparatus according to claim 3, in which said predeter-mined fraction is one-half.
5. An apparatus and motor according to claim 1, in which the pulse generator includes means for initiating deceleration of the stepping motor by providing a number of stepping pulses which bring the stepping motor directly into the negative load angle range.
6. An apparatus and motor according to claim 5, in which the motor is connected to a load and the data words stored in the store are such as to provide, for acceleration of the motor, at least one start pulse followed by control pulses timed such that each control pulse after the first occurs after rotation of the motor by sub-stantially one stepping angle.
7. A teleprinter having a movable carriage including a stepping pulse generating apparatus and motor according to claim 4, 5 or 6 in which the motor is arranged for effecting carriage return.
Applications Claiming Priority (4)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DEP2721240.4 | 1977-05-11 | ||
| DEP2721282.4 | 1977-05-11 | ||
| DE2721240A DE2721240C3 (en) | 1977-05-11 | 1977-05-11 | Circuit arrangement for operating a stepper motor in the optimal load angle range |
| DE2721282A DE2721282B2 (en) | 1977-05-11 | 1977-05-11 | Circuit arrangement for generating step pulses for driving a stepping motor |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1111903A true CA1111903A (en) | 1981-11-03 |
Family
ID=25772009
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA300,884A Expired CA1111903A (en) | 1977-05-11 | 1978-04-11 | Apparatus for generating stepping motor pulses |
Country Status (13)
| Country | Link |
|---|---|
| JP (1) | JPS53139116A (en) |
| BR (1) | BR7802933A (en) |
| CA (1) | CA1111903A (en) |
| CH (1) | CH624801A5 (en) |
| FI (1) | FI72414C (en) |
| GB (1) | GB1560373A (en) |
| IN (1) | IN150615B (en) |
| IT (1) | IT1095737B (en) |
| MX (1) | MX145064A (en) |
| NL (1) | NL7804540A (en) |
| SE (1) | SE444098B (en) |
| SU (1) | SU818506A3 (en) |
| TR (1) | TR20195A (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4510266A (en) * | 1981-10-08 | 1985-04-09 | Oce-Nederland B.V. | Stepping motor controller |
Families Citing this family (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE10322620A1 (en) | 2003-05-20 | 2004-12-16 | Bayer Materialscience Ag | High-solids binder combinations for scratch-resistant top coats |
| CN112059732B (en) * | 2020-08-31 | 2023-02-28 | 苏州铼铂机电科技有限公司 | PLC control method of polishing machine swing arm stepping motor |
-
1977
- 1977-12-20 CH CH1563777A patent/CH624801A5/en not_active IP Right Cessation
-
1978
- 1978-03-22 GB GB11284/78A patent/GB1560373A/en not_active Expired
- 1978-04-11 CA CA300,884A patent/CA1111903A/en not_active Expired
- 1978-04-19 MX MX173177A patent/MX145064A/en unknown
- 1978-04-27 NL NL7804540A patent/NL7804540A/en not_active Application Discontinuation
- 1978-04-28 SE SE7804937A patent/SE444098B/en not_active IP Right Cessation
- 1978-05-03 IT IT22953/78A patent/IT1095737B/en active
- 1978-05-09 JP JP5492378A patent/JPS53139116A/en active Pending
- 1978-05-10 BR BR7802933A patent/BR7802933A/en unknown
- 1978-05-10 SU SU782619952A patent/SU818506A3/en active
- 1978-05-10 TR TR20195A patent/TR20195A/en unknown
- 1978-05-10 FI FI781473A patent/FI72414C/en not_active IP Right Cessation
- 1978-12-15 IN IN1336/CAL/78A patent/IN150615B/en unknown
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4510266A (en) * | 1981-10-08 | 1985-04-09 | Oce-Nederland B.V. | Stepping motor controller |
Also Published As
| Publication number | Publication date |
|---|---|
| IT1095737B (en) | 1985-08-17 |
| SE7804937L (en) | 1978-11-12 |
| FI781473A (en) | 1978-11-12 |
| CH624801A5 (en) | 1981-08-14 |
| IN150615B (en) | 1982-11-13 |
| TR20195A (en) | 1980-11-01 |
| JPS53139116A (en) | 1978-12-05 |
| BR7802933A (en) | 1979-03-20 |
| IT7822953A0 (en) | 1978-05-03 |
| SU818506A3 (en) | 1981-03-30 |
| FI72414C (en) | 1987-05-11 |
| NL7804540A (en) | 1978-11-14 |
| MX145064A (en) | 1982-01-04 |
| GB1560373A (en) | 1980-02-06 |
| SE444098B (en) | 1986-03-17 |
| FI72414B (en) | 1987-01-30 |
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Legal Events
| Date | Code | Title | Description |
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| MKEX | Expiry |