FR2678449A1 - Power supply and control method and device for a stepper motor - Google Patents

Abstract

The present invention relates to a power supply and control method and device for a stepper motor. A device according to the invention includes a main microprocessor (9) which may receive digital control information via an interface (10) and includes a memory (11), from which the main microprocessor can control the power supply to the motor via a sequencer stage (12) which can control the closing of switches (1 ... 8) of power supply bridges for the coils of the motor as a function of advance control signals which are sent to it by the main microprocessor via electrical link means (32). The technical field of the invention is that of power supply devices for electric motors.

Description

Method and device for feeding and controlling a stepper motor
not.

DESCRIPTION
The present invention relates to a method and device for supplying and controlling a stepping motor.

 The technical field of invention is that of electric motor supply devices.

 Stepper motors are already known which comprise a rotor generally provided with permanent magnets and with a stator inductor which comprises at least two coils, these stepping motors being used in many automatic machines which require speed control. and in a fast and precise position.

 Patent application FR 2440642 (GILSON) describes and claims a device for controlling a stepping motor from a control signal, comprising supply circuits capable of injecting electric currents into the windings of the motor step by step according to a reference quantity, a selection circuit capable of reacting to the control signal by selectively actuating the supply circuits according to a pre-established correspondence with the control signal, in which the motor windings are distributed in pairs , the two windings of a pair cannot be switched on at the same time, such that two windings of the same pair are put in series through two respective switches with the same series resistance and such that the same circuit power supply acts on one of the two windings, in a controlled manner by a digital signal which defines both the state of the switches and the control quantity; this invention is intended to multiply the number of steps per revolution that a stepper motor can take.

 Other devices are known for controlling these stepping motors which use a microprocessor; patent application EP 94763 (KABUSHIKI KAISHA TOSHIBA) describes a stepping motor control device in particular intended to drive the carriage and the print head of a printer; according to this document the speed performance can be improved without being limited by the performance of the microprocessor, by means of a control device in which a microprocessor is provided to execute a program according to an interrupt signal applied to produce time information , which comprises a counting means for producing an impulse signal with a period defined by the time information and for supplying the interrupt signal to the microprocessor in synchronism with the impulse signal, as well as a motor control means for controlling rotation of the stepping motor in accordance with the impulse signal, in which the counting means has first and second operating modes, such that the first mode allows the application of the interrupt signal to the microprocessor, while the second mode prevents the application of the interrupt signal to the microprocessor, and such that the counting means is brought to u first mode at acceleration and deceleration of the engine and is brought to the second mode during the constant speed control of the engine.

 Patent application EP 35258 (SIEMENS) describes another stepping motor control device which allows rapid and precise positioning of the character carriers of a printer, which comprises a position sensor associated with the rotor and an electrical device producing a rotating field and which has a digital adjustment circuit which is arranged so that, depending on the destination point, the stepping motor is accelerated quickly, then coasting and is braked according to a characteristic braking curve stored in digital form, as provided, an additional analog servo-control circuit which, depending on the instantaneous value of the triangular-shaped signal from the position sensor, performs precise analog adjustment until the signal goes to zero triangular shape of the position sensor.

 The known devices and methods for controlling and supplying stepping motors nevertheless have numerous drawbacks.

 One of the drawbacks of known systems is that the user has several modules, for example a power supply module and a control module, which modules must be supplied separately, often by different voltage sources, and must be connected. between them; another significant drawback of the known devices is that the control modules have only manual adjustment means for defining the desired operating parameters of the count engine given its application; the parameters entered are generally the maximum speed, an acceleration value for the acceleration phase and possibly a different acceleration value for the braking phases.

 An objective of the present invention is to remedy these drawbacks.

 An objective of the invention is also to optimally use the performance of a stepping motor taking into account the machine which it has to drive, and thus make it possible to improve the speed of the stepping motor, it that is, to minimize the time required for the motor to perform a given number of steps.

 Another objective of the present invention is to avoid multiple power sources and the interconnections between several modules.

 An object of the invention is also to provide a control and supply device which is very simple to use, and which can almost instantly adapt to a new type of engine and to new operating conditions, or to variations thereof, in particular due to the wear of the driven machine, and to the variation of the friction forces which result from this wear.

 An objective of the invention is also to provide a very reliable control device, which allows in the event of a malfunction of the machine, of the engine, or in the event of variation of the operating characteristics of this engine and of the machine that it entails alerting the user and taking the necessary safety measures.

 The objectives of the present invention are achieved by providing a device for feeding and controlling a stepping motor comprising at least two bridges supplying respectively at least two coils of the inductor of said motor, which bridges comprise each at least four switches, such that it comprises calculation and control means which preferably comprise at least one main microprocessor, which calculation and control means can receive digital control information thanks to a digital interface, and said device comprises at least one memory in which kinematic data of said motor and of the kinematic chain of the driven machine can be recorded, so that said calculation and control means can control the supply of said motor from a single piece of information of command relating to a number of steps requested.

 Advantageously, the supply device comprises a sequencing member which can control the closing of said switches or switch according to signals (or advance orders) which are communicated to it by said main microprocessor by means of electrical connection means.

 Advantageously, the device according to the invention comprises a member for controlling the rotation of said motor which receives the signals generated by a sensor, which member for controlling communicates with said main microprocessor by means of connection means and said member for controlling rotation is preferably connected to said main microprocessor by interrupting means.

 Advantageously, said rotation control member of said motor receives said control signals transmitted by said main microprocessor to said sequencing member.

 Advantageously, the device according to the invention comprises a digital analog converter device which is connected to said main microprocessor and which can supply current setpoint signals, and it comprises at least one comparator which can compare said current setpoint with a measured value of the current Ip crossing said bridge, which comparator can cause an opening command of at least one of said switches, preferably by means of a flip-flop.

 Advantageously, said digital analog converter comprises a multiplier and a divider, so that said current setpoint signals can take three states or levels corresponding respectively to a reduced intensity setpoint which is used when said motor is stopped, at an overcurrent set point which is used when said motor is in the starting or braking phase, and at a normal current set point which is used in other cases.

 Advantageously, the device according to the invention comprises, connected in parallel between a high supply equipotential and a low supply equipotential, said bridges, at least one energy accumulator, a branch comprising in series an energy dissipator and a dissipation switch, and it comprises a main rectifier which can supply said bridges from an alternating voltage source via said equipotentials and it comprises a measurement rectifier which is supplied by said alternating voltage source and which can delivering a DC output voltage substantially equal to the DC output voltage delivered by said main rectifier, which measuring rectifier delivers said output voltage between one of said supply equipotentials and a reference equipotential, and it includes a feedback which is connected to said feed equipotentials and which is connected to said reference equipotential so that said feedback controller can detect an overvoltage appearing between said supply equipotentials, and can control the commissioning of said energy dissipator via said dissipation switch.

 Advantageously, the device according to the invention further comprises means for memorizing the working rate of said energy dissipator, and means for comparing said working rate with a predetermined maximum working rate, and preferably said device comprises at least a storage capacitor which can be charged when closing said dissipation switch and whose charge potential is compared with at least one reference potential by at least one comparator, each of said comparators being able to generate a fault signal when said potential load exceeds said reference potential.

 Advantageously, the device according to the invention further comprises intensity limiting resistance means which are connected in series with said bridges, between the output of said main rectifier and one of said equipotential feeders, and preferably said means. comprise a current limiting resistor which can be short-circuited by a switch, which switch is controlled by a current limiting device, which current limiting device is connected with means for measuring the current intensity d power supplied by said main rectifier.

The objectives of the invention are also achieved by providing a control method comprising at least two respective supply bridges of at least two coils of the inductor of said motor, which bridges each comprise at least four respective switches, and in that that it includes the following operations:
a - a control device according to the invention is provided,
and in a preliminary phase,
b - at least one calculation program is recorded in a memory of said device,
c - kinematic data characteristic of said motor and of the machine driven by said motor are recorded in a memory of said device,
d - the execution by a microprocessor of said control device is triggered, of at least part of said calculation program, which execution provides at least one first series of speed data, which first series corresponds to an acceleration ramp, and which execution provides at least a second series of speed data, which second series corresponds to a deceleration ramp,
el - the first and second sequences of speed data are recorded in a memory of said device,
e2 - using said first and second sequences of speed data, the corresponding maximum speeds are calculated for predetermined numbers of steps,
e3 - said predetermined number of steps and said corresponding maximum speeds are recorded in a memory of said device,
and in a use phase,
f - said device is supplied via said digital interface at least one piece of information on the number of steps requested and one piece of information on the direction of rotation,
g - a first series of speed data is chosen from said first series of speed data, and a second series of speed data is chosen from said second series of speed data,
h - control sequences developed as a function of said first and second series of speed data are sent to said supply bridges.

 The term "ramp" used in this document should be considered in a general sense of "curve" (of evolution), which is generally not a straight line.

 Advantageously, said kinematic data characteristic of said motors and of said driven kinematic chain comprise data relating to the maximum speed of rotation of said motor, to the number of steps per revolution of said motor, to the torque of said motor, to the resistive torque of said driven machine, to the respective inertia of said motor and of said driven machine.

 Advantageously, in said phase of use, in said operation g, said first series of speed data corresponds to a part of said first series of speed data in which said speed data is lower than said maximum speed corresponding to said information of number of steps requested, and said second series of speed data corresponds to a part of said second series of speed data in which said speed data are lower than said maximum speed corresponding to said information on number of steps requested.

 Advantageously, said kinematic data relating to the torque of said engine comprises a table of value of said engine torque as a function of the speed of said engine.

 Advantageously, said kinematic data relating to the resistive torque of said driven machine comprises a table of values of said resistive torque as a function of the speed of rotation of said motor.

Advantageously, in a development phase following said preliminary phase,
k - simulating said information on the number of steps requested and the direction of rotation,
1 - said operations g and h are executed and the effective rotation of said motor is checked, using a rotation control member, and when a stalling of said motor is detected, said suites of speed data are modified,
m - the operations k and I are executed at least two and preferably at least ten times without finding any faults, before validating said speed data suites.

 In a particular embodiment, said sequences of speed data are recorded in the form of an ordered table of relation of two variables, a first variable representing a number of steps, a second variable representing the period T of the control signal of said bridges .

 It is of course possible to choose to record, instead of said period T, the variation of said period T, either a speed information (or a variation information of said speed) or a frequency information ( or frequency variation) of said control signals.

 Advantageously, in said operation f), moreover, ceiling speed information is provided which is lower than the maximum speed of rotation, so that a high torque can be maintained.

 The numerous advantages provided by the invention will be better understood through the following description which refers to the appended drawings, which describe without any limiting character particular embodiments of devices according to the invention and control methods according to the invention .

 FIG. I represents a simplified diagram of an embodiment of a stepping motor control device according to the invention.

 FIG. 2 represents a simplified diagram of a part of an engine control device according to the invention.

 FIG. 3 represents a simplified diagram of another part of an engine control device according to the invention.

 FIGS. 4a and 4b illustrate in a simplified manner operations of the control method according to the invention.

 FIGS. 5a and 5b illustrate in a simplified manner data contained in the memories of a device according to the invention.

 FIG. 6 illustrates timing diagrams of signals of a device according to the invention.

 In FIG. I, it can be seen that a control device according to the invention comprises two bridges PC1 and PC2 for the respective supply of two coils Bi and B2 of the inductor of a stepping motor, which bridges are each provided four respective switches 1, 2, 3, 4 and 5, 6, 7.8; It can be seen that said bridges are capable of being supplied by means of a high supply equipotential + U and a low supply equipotential OV, between which there is a main supply voltage US1 which is delivered by a main rectifier P1 which can supply said bridges from an AC voltage source Ures; it can be seen that in the preferred embodiment shown in this figure, the control device comprises as input a fuse mJ, a filter F and two rectifiers, said main rectifier P1 which may for example be of the diode bridge rectifier type which supplies said supply voltage of said bridges PC1 and PC2 and a second rectifier called measurement rectifier P2 which delivers a voltage US2 between said high supply equipotential + U and a Urefl reference equipotential; We see that at the terminals of said bridges are respectively provided an energy accumulator, respectively C1 and C2 which are preferably constituted by a capacity.

 We see that in series with each of said bridges PC1 and PC2 is provided a resistance respectively RS1, RS2 which is crossed by the current passing through said bridge and which allows the measurement of this current by measuring the voltage appearing across said resistance respective of each of said bridges.

 It can also be seen that a branch comprising in series an energy dissipator Rdef (preferably a resistor), and a dissipation switch I3, is connected in parallel with said bridges, between said equipotentials of high + U and low OV supply ; It can also be seen that the control device comprises a control unit UC which comprises means 40 for controlling the state of said switches i, 2, 3, 4, 5, 6, 7 and which is connected to a digital interface 10 by means of which said control unit can receive information in digital form delivered for example by a computer or external control member (not shown).

We also see in this figure that the device according to the invention comprises a feedback controller i9 which is connected to said supply equipotentials + U, OV, and which is connected to said reference equipotential Urefi, so that said feedback controller can detect an overvoltage appearing between said power equipotentials and can control the commissioning of said energy dissipator by means of said dissipation switch I3.

Advantageously, a control device according to the invention comprises intensity limiting resistance means which are connected in series with said bridges, between the output of said main rectifier Pi and one of said supply equipotentials, and in the figure. 1, said intensity limiting means comprise a resistance Rd which can be short-circuited by a switch Ii, which switch is controlled by a current limiting device which is connected with means for measuring the current intensity supply supplied by said main rectifier, which measuring means comprise a voltage tap Urd appearing at the terminals of said intensity limiting resistor Rd also called starting resistor; we see that an additional resistor Ril is connected in series with said switch so that when the latter is closed by said device 20 intensity limiter, said device 20 can measure said voltage Urd appearing across said resistor Rii which is very low compared to said resistance Rd, and said current limiting device can compare said voltage Urd with a reference voltage Uref2 previously determined so that when said current limiting device detects an overvoltage
Urd corresponding to an overcurrent, this device can inform said control unit UC of this anomaly thanks to connection means 27 provided between said intensity limiting device and said control unit.

 The advantage of said limiting resistor Rd is obvious since, thanks to a resistor of the order of 20 ohms, the presence of this resistor which is put into operation during start-up makes it possible to limit the start-up intensity and therefore the intensity calling on the network at reasonable values of the order of a few tens of amperes, for example for driving a motor with a power of a few kW; in fact, in the absence of such a current limiting resistor, in particular at start-up, the internal resistance of the device located between the high and low equipotentials being of the order of 0.5 1, the current draw resulting from the powering up of the device could exceed several hundred amperes and would therefore require protections and supply devices particularly designed for this and of high cost. A control device according to the invention can of course be provided to operate with said alternating voltage Ures of 220 volts which allows the supply of the whole of the stepping motor control device and which makes it possible to have said main supply voltage of said bridges US1 of a value substantially equal to 3i0 volts, or well can be directly powered by a DC voltage source.

 At power-up, a starting resistance Rd limits the current draw of Ci to protect said main rectifier, and reduce the call on the user's network.

 An intensity limiting circuit 20 monitors the voltage Urd, image of the charging current of C1.

 When Urd drops below a limit Uref2, said intensity limiting circuit 20 closes the switch I1 which short-circuits the resistance Rd.

If during operation, said voltage Urd exceeds said threshold
Uref2, said intensity limiting circuit reopens the switch I1 for a minimum duration (of 5 ms for example).

 Note that the internal resistance of I1 (consisting for example of a MOSFET transistor) determines the reopening current Imax = Uref2 / Rii.

 the possible overvoltages on opening in the event of an inductive circuit are absorbed by the Ec clipper which is constituted by a zener diode.

 Said circuit 20 provides a report to said control unit through an opto-isolated link (OV and -U being different).

 In Figure 2, there is shown schematically and in a simplified manner a part of said control unit which is essentially digital in a stepper motor control device according to the invention.

 It can be seen that said device comprises a main microprocessor 9 which can receive digital control information thanks to a digital interface i0, and said device comprises a memory 11 in which kinematic data characteristic of said engine and of the kinematic chain of the machine driven by said motor, so that said main microprocessor can control the supply of said motor from a single control information item relating to the number of steps requested to be made to said motor, and the device also comprises a sequencing member 12 which can command the closing of said switches (references 1 to 8 of FIGS. 1 and 2), according to the order of advance which are communicated to it by said main microprocessor by means of two direct electrical connection means 32 between said main microprocessor and said sequencer; a control member 14 is also connected to the electrical connection means 32, which enables it to receive said control information sent by said microprocessor to said sequencer; it can be seen that the device illustrated in FIG. 2 also includes said control member 14 for the rotation of said motor which receives the signals generated by a rotation sensor 15, and said control member communicates with said main microprocessor by means 16 d interruption so that when said control member detects a phase difference between said control signals sent by said microprocessor to said sequencing member, and said signals supplied by said sensor which may advantageously be an optical encoder, said rotation control member informs said microprocessor main of this malfunction, thanks to said interrupt means 16. Said main microprocessor can be connected to said interface by said bus 13 and by means 28 for switching from said interface 10 to said bus, so as to receive said digital control information through this interface, and so to be able to isolate said interface from said bus when said microprocessor controls said sequencer member and dialogs with said sequencer member and said rotation control member.

 Advantageously, said main microprocessor can alternately receive said control signals (produced by an external device of known type) by means of direct electrical connection 31; in this case, said main microprocessor simply transmits said received signals to said sequencer.

 Said microprocessor is advantageously connected to a device which includes a digital analog converter 21 which can supply current setpoint signals 23 to two comparators 221 and 222 which can compare said current setpoint 23 with an image Upi, Up2 respectively of the measured value the respective current Ipl, Ip2 passing through each of said bridges, via said measurement resistors Rsl and Rs2, so that each of said comparators 221, 222 can cause an opening command of at least one of said switches (i to 8 ) via a flip-flop respectively 241, 242; Advantageously, said flip-flops are connected by their "Set" terminals (S) to said sequencing member and are connected by their "reset" terminals (R) to said comparators so that said comparators comparators which constitute safety devices have a higher priority level compared to the orders communicated by said sequencing unit auxdit es flip-flops. The assembly formed by said comparators and said flip-flops associated with AND gates for validating control orders from said sequencing unit to said switches, makes it possible to produce a kind of device for chopping said control signals from said switches.

 Advantageously, said digital analog converter comprises a multiplier and a divider so that said current setpoint signals 23 can take three states or levels respectively corresponding to a reduced intensity setpoint which is used when said motor is stopped, at an overcurrent setpoint which is used when said motor is in the starting or braking phase, and at an intensity setpoint which is used in other cases.

 In FIG. 3, it can be seen that an engine control device according to the invention makes it possible, when said engine is in the deceleration phase, which causes energy to be returned to the supply circuit by said engine, and causes the charging of said capacitor (reference Ci in FIG. i), and therefore causes an overvoltage between said equipotentials of supply + U and OV, which risks destroying components of a control device, a circuit 29 for voltage monitoring (which corresponds substantially to the reference 19 in FIG. 1) is provided which receives the reference potential Urefl delivered by said measuring rectifier P2 and compares said reference potential Urefl with the voltage appearing between said supply equipotentials; if the difference between these voltages exceeds a predetermined threshold value corresponding to the mark Uref3 in FIG. 3, said circuit 29 causes said dissipation switch I3 to close, which causes said dissipation resistance Rdef to be put into service; in this way, the energy returned between said equipotentials by said motor in the deceleration phase is absorbed by said dissipation resistor advantageously, a control device according to the invention comprises means for memorizing the working rate of said dissipation resistor d energy and means for comparing said work rate with a predetermined maximum work rate; these results are achieved by virtue of a storage capacitor C4 which is charged when a switch I4 is closed, which closing is controlled by said circuit 29 simultaneously with said control of said dissipation switch; the charging current of said capacitor C4 has a value substantially equal to the difference between a current la which passes through a resistor R5 connected between said high and low power equipotentials and a substantially constant current delivered by a current generator, so that said current 10 being judiciously chosen, a relative variation (of X%) of the voltage between said high and low equipotentials results in a double variation (of 2X%) on the charging current of said storage capacitor.

 Knowing on the other hand that the power dissipated by said dissipation resistance is proportional to the square of the voltage between said high and low equipotentials, and that for a small variation of X% of said voltage between said high and low equipotentials, the power dissipated by said resistance is substantially equal to 2X%, it is clear that the charge current of said capacitor corresponds to the image of the instantaneous power dissipated by said dissipation resistance; when said circuit 29 opens said switch I3 causing said dissipation resistor to go out of service, it simultaneously opens said switch I4, and said capacitor C4 discharges into a constant current source Ii.

Thus, the voltage Uc4 corresponds to an image of the average power dissipated by said dissipation resistance Rdef and, in other words, of its operating rate; said voltage Uc4 can advantageously be compared by comparators CO1 and C02 to reference potentials (or voltages) respectively Uref4 and
Uref5 predetermined, so that when said voltage Uc4 image of said operating rate of said dissipation resistor exceeds said value Uref4 or said Uref5 advantageously greater than Uref4, said control unit of said device according to the invention can be informed of said excess with respect to said predetermined values thanks to logic means 31 and connection means 27; moreover, when said voltage Uc4 exceeds said predetermined reference voltage Uref5 advantageously greater than Uref4, a timer 30 can be activated which locks said voltage monitoring device 29 preventing the commissioning of said dissipation resistance for a predetermined duration; said control unit can of course be informed of this event.

Advantageously, a method according to the invention, a calculation program is stored in said memory of said device associated with said main microprocessor and kinematic data characteristic of said motor controlled by said control device and of the machine driven by is recorded in a memory of said device. said motor; then, data relating to the maximum speed Vmax of rotation of said motor, to the number of steps per revolution NPM of said motor, to the torque CM of said motor, to the resistive torque CR of said driven machine, to inertia J1, J2 respectively are recorded said motor and said driven machine.

We can then calculate using said program and said main microprocessor a total inertia J3 of the system constituted by said motor and said driven machine, brought back to the motor shaft and we can then calculate the maximum speed increase (fi-fi-l) for a pitch of rotation of said motor by the formula::
f2i = f21-i + tcM - CR) NPM (in acceleration phase)
D3
and wherein said motor torque CM and said resistive torque
CR can advantageously be expressed as a function of the speed of rotation thanks to the prior introduction into one of said memories of said device, of a curve or table of this curve of variation of said motor torque as a function of speed and of said torque resistant as a function of speed, in particular in the case of a viscous type resistant torque.

 This iterative calculation makes it possible to calculate from a zero speed a first series of speed data which are lower than said maximum speed and which correspond to the maximum speeds which it is possible to reach at each successive step in a phase of acceleration of said engine; in the same way, using a formula equivalent to that mentioned above by changing the sign of the engine torque, calculate a second series of speed data corresponding to a deceleration phase starting from said maximum speed up to 'to reach a substantially zero speed.

 Furthermore, in certain cases of use of a method and a device according to the invention, it is useful to use as the "ceiling" speed, not said maximum speed contained in said recorded kinematic data, but a value lower than the value of said maximum speed, which makes it possible to maintain sufficient engine torque throughout the duration of the control of said engine; in this case, said ceiling speed value can be supplied to said main microprocessor each time that information on the number of steps requested is supplied to said main microprocessor, which main microprocessor can substitute said ceiling speed for said maximum speed recorded.

 It is then possible to record in one of said memories of said device in the form of an ordered table of relations of two variables, for example a first variable representing a number N of steps, a second variable representing a variation DT of the period T of the signal for controlling said bridges or alternatively in the form of an ordered table of relationship of two variables, a first variable representing the number N of steps, a second variable representing a variation DF of the frequency F of said control signal of said bridges as shown in FIG. Figure 5A.

 The difference of said period between two successive points of said ordered table is given by application of the iterative calculation formula defined above.

 Said deviation can be bounded by a minimum value and in this case, the corresponding number of steps requested is accumulated by said main microprocessor until the sum of said numbers of steps requested is greater than this minimum value (which for example may be the resolution of the control device).

 The table of said variables represented in this figure corresponds to the diagram of the speeds as a function of the number of steps taken represented in FIG. 4A. It can be seen in these two figures that at the first step the maximum increase in speed calculated according to the above formulas corresponds to an increase in the frequency of rotation of said DF1 motor, and that for each of the following successive steps are increased frequency of respective rotation DF2, DF3, DF4, DFs and DF6, all of these speed increases constituting said acceleration curve which is limited by the speed Vmax introduced for said motor which corresponds to the frequency of rotation Fmax in FIG. 4A; in the same way, in the speed calculation phase in a deceleration phase DE, successive decreases in rotation frequency DF7, DF8, DF9, DFiO and DFll were successively calculated until a rotation frequency corresponding to a substantially zero speed; in FIG. 4A, it can be seen that on the speed diagram is provided a PAL level between said phase of acceleration AC and said phase of deceleration DE.

 It can be seen that in the corresponding table, which can be recorded in one of said memories of said device, which is represented in FIG. 5A, the address Adr of said memory (represented in the form of a table) takes successive values i, 2, 3 , ... il, and at each address there is a value of the number N of step increments (which in this particular case is constant and equal to 1); for each increment N in the table corresponds an increment or decrement of the rotation frequencies DF identified in this table DF1 up to DF11. The number of steps and the number of speed increments (or frequency) mentioned in FIG. 4A and in Table 5A is deliberately very small compared to reality for reasons of simplicity of the description. Advantageously, during the phase for calculating said series of speed data in said acceleration and deceleration phases, a lexicon table as represented in FIG. 5B can be established as the calculation progresses, in which one can indicate for each number of cumulative steps NPC appearing in the first column of the table of FIG. 5B, the maximum frequency of rotation reached respectively fO and fl for a number of accumulated steps of 7 or 8 and to which a jump address is made which in this case is the address 9 with reference to the table in FIG. 5A. We can see in FIG. 4B in which a diagram of the speeds corresponding to a number of pa has been represented. s asked NPD of 7 that, given the number of steps requested, it is impossible to reach said speed Vmax corresponding to said frequency Fmax of FIG. 4A and that consequently, thanks to said lexicon table of FIG. 5B, said microprocessor can know that it must be limited to a maximum frequency of rotation fo which will preferably be maintained for a number of steps corresponding to the reference PALmin in FIG. 4B. In this way, when said microprocessor receives said command of requested number of steps NPD equal to 7, he chooses in said table of FIG. 5A the sequence of speed data corresponding to the sequence of frequency data DF1, DF2, DF3 until reaching said rotation frequency Fg mentioned in the glossary table, then said microprocessor causes to be executed said PALmin stage at constant speed corresponding to said frequency Fg, then causes said stages of the deceleration phase DF9, DFiO and Du'li to be executed using the x jumps in said table of FIG. 5A at the address 9 which is mentioned in said lexical table of FIG. 5B, address corresponding to the number of cumulative steps requested NPC equal to 7.

 FIG. 6 illustrates timing diagrams of control signals of a device according to the invention; the control signals 30, 31, 33, 34, 35, 36, 37, 38, 39 are identified with reference to the references in FIG. 2 with the same numbers; the timing diagram identified Ib is a timing diagram of the intensity crossing the coil B1 with reference to FIG. 1; the timing diagram marked 40 is the timing diagram of the voltage across said coil marked B1 in Figure i.

 In FIG. 6 are represented the timing diagrams of said signals for three successive steps Ni, N2, N3 of duration equal to a predetermined value T1; the timing diagrams illustrated in FIG. 6 explain the control of said coil Bi by the bridge marked PCi in FIG. 1 which include said switching means 1, 2, 3, 4; the control of said bridges (marks PCi and PC2 in FIG. i) being intertwined over time, it can be seen in FIG. 6 on said chronogram lb of the intensity crossing one of said coils that said intensity takes a positive value during said step marked N1, takes a substantially zero value during said step marked N2 and takes a negative value (substantially equal to the opposite of the value taken during said step N1) during said step N3.

 With reference to FIGS. 3 and 2, said timing diagrams 35 and 36 represent the evolution as a function of time of the control signals of said switches 1 and 3 respectively of said bridge PC1, said timing diagrams 37 and 38 respectively represent the evolution as a function of time respective control signals of said switches or switches 4 and 2 of said bridge PCi; said timing diagrams 33 and 34 illustrate the control signals of said respective switches 1 and 3, which control signals come from said sequencer 12, before their passage in a logic module 41 ensuring the logic function AND between said signals illustrated in timing diagrams 33 and 34 and the flip-flop output signal 31; with reference to FIG. 2, said timing diagram 30 illustrates signals from said sequencing unit 12 to reset each of said flip-flops 241 and 242, said timing diagram 39 representing the signal from a comparator 221 of the intensity absorbed by the corresponding bridge, by compared to a predetermined intensity.

 It can be seen in FIG. 6 that said control signal 30 coming from the sequencer is a permanent signal with fixed frequency of period T2 which can for example be close to 100 micro seconds; as illustrated by the arrow F1, during the passage of said signal 30 from a state O (low level) to a state 1 (or high level), and provided that said signal 39 is in state 0, which corresponds to a state where the intensity crossing said bridge does not exceed a predetermined value, said passage of said reset signal 30 from state O to state i causes the rise (or passage from state O to state 1) of the output signal 31 of the corresponding flip-flop.

 As indicated by arrow F2, the transition to state 1 of said signal 31, taking into account the high state (equal to 1) of said signal 33, causes the transition to being 1 (high) of said signal 35 of control of the switch marked 1 in FIG. 1 (by means of said module 41 ensuring the AND logic function illustrated in FIG. 2).

 As indicated by the arrows F3, the transition to state 1 of said signal 35 which is the control signal of said switch i, taking into account the high state (equal to 1) of said control signal 37 of said switch 4 of said bridge PCi , said switches 1 and 4 being then closed, causes the appearance of a voltage identified by the timing diagram 40, which appears at the terminals of said coil Bi of said bridge PCi, which voltage at the terminals of said coil causes the increase of current Ib crossing said coil as indicated by arrow F4.

When said intensity Ib exceeds a predetermined value Ibl, causing through said comparators (reference 221 in FIG. 2) as indicated by arrow F5, the passage to the high state (equal to i) of said signal 3O, this causes, as indicated by arrow F6, the resetting of said flip-flop (item 24i in FIG. 2) and subsequently the resetting of said signal 31 in FIG. 6; ; the zero crossing of said signal 31 causes, as indicated by the arrow
F7, the fallout of said signal 35 and therefore of said voltage 40 across said coil B1, which taking into account the reactance of said coil, causes, as indicated by arrow F8, a reduction in said intensity Ib passing through said coil, and therefore maintaining said intensity at a value close to said predetermined Ibi value.

Claims (11)

CLAIMS i - Device for supplying and controlling a stepping motor comprising at least two bridges (PC1, PC2) for supplying respective at least two coils (B1, B2) of the inductor of said motor, which bridges each have at least four respective switches (i, 2, 3, 4) and (5, 6, 7, 8), characterized in that it comprises a main microprocessor (9) which can receive digital control information by to a digital interface (10), and said device comprises at least one memory (Ii) in which kinematic data characteristic of said motor and of the kinematic chain of the machine driven by said motor can be recorded, so that said main microprocessor can controlling the supply of said motor from control information relating to the number of steps requested to be carried out to said motor, and in that it comprises a sequencing member (i2) which can control the closing of said s switches (1, ... 8) as a function of advance orders which are communicated to it by said main microprocessor.  2 - Device according to claim 1 characterized in that it comprises a control member (14) of the rotation of said motor which receives the signals generated by a sensor (15), which control member (14) is connected to said main microprocessor by means (16) of interruption.  3 - Device according to any one of claims 1 to 2 characterized in that it comprises a digital analog converter device (21) which is connected to said main microprocessor and which can supply signals (23) of current setpoint, and it comprises at least one comparator (22) which can compare said current setpoint with a measured value of the current (Ip) passing through one of said bridges, which comparator can cause an opening command of at least one of said switches, preferably by l 'through a rocker (24).  4 - Device according to claim 3 characterized in that said digital analog converter comprises a multiplier and a divider, so that said current setpoint signals (23) can take three states or levels corresponding respectively to a reduced current setpoint which is used when said motor is stopped, at an overcurrent setpoint which is used when said motor is in the starting or braking phase, and at a normal current setpoint which is used in other cases.  5 - Device according to any one of claims 1 to 4 characterized in that it comprises, connected in parallel between a high supply equipotential (+ U) and a low supply equipotential (OV), said bridges (PC1 , PC2), at least one energy accumulator (C1), a branch comprising in series an energy dissipator (Rdef) and a dissipation switch (I3), and it comprises a main rectifier (P1) which can supply from an alternative voltage source (Ures) said bridges via said supply equipotentials (+ U, OV) and it comprises a measurement rectifier (P2) which is supplied by said alternating voltage source and which can delivering a DC output voltage (US2) substantially equal to the DC output voltage (US1) supplied by said main rectifier, which measuring rectifier delivers said output voltage (US2) between one of said equipotential supply lines (+ U , OV), and a reference equipotential (Urefi), and it comprises a feedback controller (19) which is connected to said supply equipotentials (+ U, OV) and which is connected to said reference equipotential (Urefl) so that said controller feedback can detect an overvoltage appearing between said power equipotentials, and can control the commissioning of said energy sink via said dissipation switch.  6 - Device according to claim 5 characterized in that it further comprises means for memorizing the working rate of said energy sink, and means for comparing said working rate with a predetermined maximum working rate, and preferably said device comprises at least one storage capacitor (C4) which can be charged when closing said dissipation switch (I3), and whose charge potential (UC4) is compared with at least one reference potential (Uref4, Uref5 ) by at least one comparator (COi, Cl2), each of said comparators being able to generate a fault signal when said load potential exceeds said reference potential.  7 - Device according to any one of claims 5 to 6 characterized in that it further comprises intensity limiting resistance means which are connected in series with said bridges, between the output of said main rectifier (P1) and one of said supply equipotentials, and preferably said means comprises a resistor (Rd) for limiting the intensity which can be short-circuited by a switch (li), which switch is controlled by a device (20) limiting d intensity, which intensity limiting device is connected with means for measuring the intensity of the supply current delivered by said main rectifier.  8 - Method for controlling a stepping motor comprising at least two bridges (PCi), (PC2) respective supply of at least two coils (Bi, B2) of the inductor of said motor, which bridges each comprise at least four respective switches (1, ... 4) and (5, ... 8), characterized in that it comprises the following operations:  a - a control device according to any one of claims 1 to 7 is provided,  and in a preliminary phase,  b - at least one calculation program is recorded in a memory of said device,  c - kinematic data characteristic of said motor and of the machine driven by said motor are recorded in a memory of said device, which kinematic data comprise at least one data relating to the torque (CM) of said motor, at least one data relating to the resisting torque ( CR) of said driven machine and at least one piece of data relating to the inertia of said motor and of said driven machine,  d - the execution by a microprocessor of said control device is triggered, of at least part of said calculation program, which execution provides at least one first series of speed data, which first series corresponds to an acceleration ramp, and which execution provides at least a second series of speed data, which second series corresponds to a deceleration ramp,  el - the first and second sequences of speed data are recorded in a memory of said device,  e2 - using said first and second sequences of speed data, the predetermined maximum speeds (VMi, VM2, ...) are calculated for predetermined numbers of steps requested (NPi, NP2, ...),  e3 - said predetermined number of steps and said corresponding maximum speeds are recorded in a memory of said device  and in a use phase,  f - at least one piece of information (NPD) of requested number of steps is supplied to said device via said digital interface (10),  g - a first series of speed data is chosen from said first series of speed data, and a second series of speed data is chosen from said second series of speed data,  h - control sequences developed as a function of said first and second series of speed data are sent to said supply bridges.  9 - Method according to claim 8 characterized in that, in said operation g of said phase of use, said first series of speed data corresponds to a part of said first series of speed data in which said speed data are lower at said maximum speed corresponding to said requested number of steps (NPD) information, and said second series of speed data corresponds to a part of said second sequence of speed data in which said speed data is lower than said corresponding maximum speed to said information (NPD) of number of steps requested.  10 - Method according to any one of claims 8 to 9 characterized in that, in a development phase consecutive to said preliminary phase,  k - we simulate said information on the number of steps requested,  1 - said operations g and h are executed and the effective rotation of said motor is checked, using a rotation control member (14), and when a stalling of said motor is detected, said data suites are modified of speed,  m - operations k and 1 are executed at least twice without finding any faults, before validating said speed data suites.  11 - Method according to any one of claims 8 to 10 characterized in that in said operation f), it also provides ceiling speed information lower than the maximum speed of rotation, so that one can maintain a torque Student.