AU615752B2 - A control circuit for a stepping or self-switching motor - Google Patents

Description

615 ,5Re 7 971 FORM COMMONWEALTH OF AUSTRALIA PATENTS ACT 1952 COMPLETE SPECIFICATION

(ORIGINAL)

FOR OFFICE USE: Class Int Class Complete Specification Lodged: Accepted: Publ i shed: to.

SPriority: Related Art: SName and Address

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of Applicant: Crouzet S.A.

4, Rue Francois Ory 92128 Montrouge

FRANCE

Address for Service: Spruson Ferguson, Patent Attorneys Level 33 St Martins Tower, 31 Market Street Sydney, New South Wales, 2000, Australia Complete Specification for the invention entitled: A Control Circuit for a Steppl-g or Self-Switching Motor The following statement is a full description of this invention, including the best method of performing it known to me/us

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S 008085 9-6-89 5845/3

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I I'- LTiE A CONTROL CIRCUIT FOR A STEPPING OR SELF-SWITCHING MOTOR

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S 5505 A.B.1TRA U. U A control circuit for a motor of the disk-shaped magnet and angle encoder type in a stepping mode or self-switching with a speed regulation mode. The stepping control is ensured by a set of two conventional integrated circuits, the first one (CIl) supplying a control signal to the second one (CI2) serving as a driver, the first integrated circuit also comprising means for applying intermittent enabling signals to the second one when it receives a security signal indicating that the current in at least one of the phases is higher than a determined threshold (VREF).

Control in the self-switching mode is supplied by a programmable logic array (PLA). The first integrated circuit (CI1) is used for regulating the speed in the selfswitching mode, said first integrated circuit thus receiving at its security input the signal resulting from the frequency/voltage conversion of the output of one of the angle encoders.

*.Se 1A A CONTROL CIRCUIT FOR A STEPPING OR SELF-SWITCHING MOTOR BA.C.KGRQUI.NDO.FT..i....E.,.INZENTIQN

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i The present invention relates to the -control of electric motors.

In some applications it is desirable to cause the motor to operate sometimes as a stepping motor sometimes as a constant speed regulated motor.

i Generally, this problem being difficult to resolve, two motors have been used for this type of application, one i being controlled in the stepping mode, the other at a ~I 10 constant speed, those motors being alternatively engaged.

Si During the last few-years, motors which lend themselves to operate either in the stepping mode or in the normal 9 *mode have been developed. To exemplify such a motor, one S..can mention the disk-shaped magnet and the integrated angle 15 encoder motors such as the one marketed by company Portescap (France), referenced PP520.

Those motors effectively lend themselves to operate in either mode, but in the known application circuits, i distinct circuits are used for each of the two control 20 functions.

The object of the present invention is the alternate control of a motor such as of the disk-shaped magnet and I• integrated angle encoder type, in the stepping or continuous running mode, the operating speed in the continuous running mode being regulated, by using a single electronic circuit for the control of those two modes.

SSpecifically, the present invention aims at providing such a control circuit which is particularly simple and uses a minimum number of integrated circuits, those integrated circuits being shared for both functions.

-2- To achieve those objects, the present invention provides a circuit for controlling a motor having two phase windings in a stepping mode or a J speed-regulated continuous running mode, said motor being of the type 1 having a disk-shaped magnet and angle encoders, which produce sensing signals dependent on the speed of rotation of the motor, wherein said circuit comprises first and second integrated circuits, the first integrated circuit receiving stepping clock signals and supplying stepping mode motor phase control signals to the second integrated circuit, the first integrated circuit also comprising means for applying intermittent enabling signals to the second integrated circuit when it receives on a Ssecurity Input a signal Indicating that the current in one at least of the tl 1 phase windlngs is higher than a pre-determined threshold, the circuit I further comprising a programmable logic array for receiving the sensing signals from the angle encoders and producing speed-regulated mode motor 15 phase control signals therefrom, wherein the first integrated circuit regulates the speed in the speed-regulated mode by receiving at its security input a signal resulting from a frequency/voltage conversion of the output of one of the angle encoders, and the second integrated circuit amplifies the speed-regulated mode control signals and the stepping-mode control signals to produce control signals for controlling the motor.

BRIEF DESCRIPTION OF THE DRAWINGS The foregoing and other objects, features and advantages of the invention will be apparent from the following detailed description of a 25 preferred. embodiment as illustrated in the accompanying drawings wherein: i: Fig. 1 shows a stepping motor control device; Fig. 2 shows a dual stepping or continuously regulated control, according to the invention; Fig. 3 shows wave-shapes illustrating the operation of the circuit of Fig. 2; and amg/125ir

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lti 3 Fig. 4 shows an exemplary application of a dual controlled motor according to the invention.

RTAIL.ED...D...RIDERIZINQ..Q,.TH...INENT I.OQN Fig. 1 shows a motor M fed by a stepping control circuit. This motor receives signals onto two windings, namely a phase signal 1 between output conductors P11 and P12 and a phase signal 2 between output conductors P21 and P22. Conventionally, this control is carried out by means of two integrated circuits available on the market, namely a first control integrated circuit CI1 such as circuit L297 manufactured by SGS corporation and a second driver integrated circuit CI2 such as circuit L298 also manufactured by SGS.

The control circuit CI1 receives an ON/OFF command 15 signal M/A, a rotation-direction control signal ROT, a clock signal CL supplying the stepping control pulses, and a signal OSC from an oscillator operating at a high frequency with respect to the motor frequency. This circuit SCI1 supplies for the control of phase 1 a signal on lines C11 and C12 and for the control of phase 2 a signal on S lines C21 and C22.

S* In addition, the integrated circuit CI2 of the abovementioned type comprises outputs I1 and 12 representing the currents in phase 1 and phase 2. Those outputs are applied to a current/voltage converter 10 and the integrated S circuit CI1 comprises corresponding inputs V1 and V2 permitting to compare the voltages V1 and V2 resulting from the voltage transformation of currents II and 12 with a reference voltage VREF. On the drawing of Fig. 1, voltages V1 and V2 have been added in an adder 11 and the input terminals V1 and V2 of circuit CIl are interconnected. The integrated circuit CII compares the sum of voltages V1 and V2 with a reference voltage VREF and, if this sum is higher than the reference voltage VREF, circuit CI1 supplies to 7 a 1 circuit CI2 a signal OSC1 resulting from the control by signal OSC to allow the output signals to flow only when the oscillator signal is high, thus chopping those signals and reducing the electric power available for the motor.

Thus, the comparison of VI V2 with VREF constitutes a protection against overvoltages in case currents II and 12 exceed a predetermined value. However, it will be noted that in normal operation, when the circuit operates without trouble, values V1 and V2 are close to zero and the security loop does not supply any signal.

Fig. 2 shows an embodiment of the dual control circuit according to the invention. Motor M, integrated circuits CI1 and CI2 and the security loop comprising components and 11 are shown again. Motor M is a disk-shaped magnet 15 motor provided with integrated angle encoders supplying signals Si and S2 which are square pulses corresponding to the rotating speed of the motor (a given number of square pulses per rotation). Conventionally, such a motor is controlled by supplying from signal SI and S2, through a 20 PLA combinational circuit, signals C11-C12 and C21-C22 designed, after amplification by an amplifier that can be the above-mentioned circuit CI2, to supply signals P11-P12 and P21-P22 for controlling the two phases of the motor.

Conventionally, the PLA circuit receives the direction command signal ROT to determine the way signals C11-C12 and C21-C22 will be derived from signals S1 and S2 for providing the appropriate rotation direction to the motor.

The present invention provides for regulating the speed of motor M by using the integrated circuit CI1. Thus, one of the signals S1 or S2 of the motor encoders is sent to a frequency/voltage converter circuit 20 which applies its output to adder 11 near the above-mentioned interconnected inputs V1 and V2. Thus, when the motor speed increases above or decreases under a reference value, the sum VI V2 T T

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becomes higher or lower than the reference voltage and the output signal OSC1 acts upon integrated circuit CI2 in order to regulate the speed. Circuit 20 receives a setting signal R and a selection signal SEL to be activated only if it is desired to obtain the continuous running (or selfswitching) mode. Similarly, the PLA circuit is controlled by signal SEL for, in the self-switching mode, supplying the appropriate signals to integrated circuit CI2 from signals S1 and S2 and, in the stepping mode, directly transmitting the outputs of integrated circuit CI1.

Fig. 3 shows the wave-shapes appearing on various points of the circuit shown in Fig. 2 to explain the operation of this circuit. It is assumed in this figure that motor M is in a regulated self-switching operation 15 mode.

Signals S1 and S2 of the sensors incorporated in motor M, for example Hall sensors, have the shape of square pulses with a 0.5 duty cycle, those square pulses being shifted one with respect to the other by r/2 according to the rotation direction. In the given example, signal S2 is lagging by n/2 with respect to SI.

Output signal V1 V2 of the frequency/voltage (F/V) converter 20, derived from signal S1 in the given example, is a saw-tooth signal, the rising edge of signal S1 corresponds to the start of signal V1 V2. One has shown the operation at the regulated state, that is, voltage VREF corresponds to an intermediate value between the minimum and maximum values of signal V1 V2. Besides, it will be noted that the amplitude of this signal V1 V2 is adjusted by an input R to converter The regulation signal OSC1 from integrated circuit CI1 is a high level signal when V1 V2 is lower than VREF and a signal having a frequency corresponding to the signal from oscillator OSC when V1 V2 is higher than VREF.

55 S S S. S 6 By way of example, signals CI1 and CI12 controlling phase 1 and C21 and C22 controlling phase 2 at the output 'of the PLA circuit are shown. They are signals with opposite phases on the two conductors of a same phase and shifted by T/2 from one phase to the other.

Signal OSCI arriving on integrated circuit CI2 determines that output signals P11, P12, P21 and P22 correspond to the passage of those signals C11-C22 through AND gates, the other input of which corresponds to signal OSC1. Thus, the signals P11-P22 are obtained, as shown.

Consequently, if the amplitude of VI V2 increases, the chopping of signals P11-P22 increases and, conversely, it decreases if signal V1 V2 decreases. It is thus ascertained that motor M runs at a constant speed.

e 5 It will be understood that a characteristic of the S" invention is to use the integrated circuit CI1 and the 0° security function that is usually associated with o integrated circuits CI1 and CI12 for ensuring the speed .regulation of the motor in the self-switching mode.

Moreover, as shown in Fig. 2, even in the regulation mode, it is possible to continue using the security function ensured by the current/voltage converter 10 for reducing S the power supplied to the motor in case of emergency, that is, in case of overvoltage on a phase.

A motor control according to the present invention is especially usable in a ticket validation device. It is for example a fixed or hand-carried device, for example in a Sbus, designed to check magnetic track tickets.

A schematic exemplary device is illustrated in Fig. 4.

The user puts his ticket into a wicket GE. The ticket is taken along by a transport web 1 rotating around rolls 2 and 3 and is driven by the above-mentioned motor M.

The ticket is detected by an input sensor CE and swallowed into the validation device. A slot shutter OF is T -I 0* .0e.

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SO S then operated by an electromagnet preventing any other admission while the ticket is being processed inside the device. The ticket is then driven in front of a magnetic head TM for the reading of digital coded information on the magnetic track. The processing of this information is carried out (validation checking, decrease of the residual value, etc. then the travel of the transport web is reversed to drive the ticket again under the magnetic head TM in order to code new data. Synchronization is ensured by an encoding sensor CC. The travel is then once more reversed in order to read again the information that has just been encoded (code checking). Once those operations are completed, the ticket is driven to a printing system TI, for example an impact printing system.

In all the above travels, especially for magnetic reading, the motor had to run at a constant speed in either direction. Then, it has to be stopped and be driven stepby-step in order to permit the transversal printing of a series of lines, dots or characters.

20 Lastly, the ticket is driven to an output wicket GS where it can be withdrawn by the user. The output sensor CS permits to check the withdrawal of the ticket. The input slot shutter is then released and the device is ready to process a new ticket.

It can be seen that in such a system wherein a combination of continuous travels at a constant speed and in the stepping mode is needed, the control system according to the invention is particularly well adapted.

Of course, the invention is liable of numerous variations and modifications. Especially, specific motors and integrated circuits have been exemplified hereinabove.

Any other motor and integrated circuit exhibiting equivalent functions are usable.

Claims (4)

1. A circuit for-controlling a motor having two phase windings in a stepping mode or a speed-regulated continuous running mode, said motor being of the type having a disk-shaped magnet and angle encoders, which 5 produce sensing signals dependent on the speed of rotation of the ,otor, wherein said circuit comprises first and second integrated circuits, the first integrated circuit receiving stepping clock signals and supplying stepping mode motor phase control signals to the second integrated circuit, the first integrated circuit also comprising means for applying intermittent enabling signals to the second integrated circuit when it receives on a security input a signal indicating that the current in one at least of the phase windings is higher than a pre-determined threshold, the circuit further comprising a programmable logic array for receiving the sensing signals from the angle encoders and producing speed-regulated mode motor phase control signals therefrom, wherein the first integrated circuit regulates the speed in the speed-regulated mode by receiving at its security input a signal resulting from a frequency/voltage conversion of the output of one of the angle encoders, and the second integrated circuit amplifies the speed-regulated mode control signals and the stepping-mode control signals to produce control signals for controlling the motor.

2. A circuit for controlling a motor substantially as hereinbefore described with reference to Figures 2 to 4 of the drawings.

3. A method of controlling a motor used in a magnetic reading and 25 printing system for tickets by using the circuit of either claim 1 or cl'aim 2

4. A magnetic reading and printing system comprising a motor having a disk-shaped magnet and angle encoders, and the circuit of either claim 1 or claim 2. DATED this TWENTY-THIRD day of JULY 1991 Crouzet S.A. Patent Attorneys for the Applicant SPRUSON FERGUSON 251r a a a a a *a a a. a a a a a a a .aa. a a a a a a. a. a ROT k C2 2 CL Oso Osci Vi V2 Vr,6f Figure 1