Device and method for controlling an electric motor with a stepped control law

Abstract

The invention relates to a device (15) for controlling a synchronous electric motor (16) comprising a stator supplied with electricity by an electrical phase (U, V, W) of a power converter, the power converter comprising an electrical line provided with switching cells (M1, M2, M3, M4, M5, M6), wherein the power converter controls, using a stepped control law, each switching cell (M1, M2, M3, M4, M5, M6) by means of a control signal (SM1, SM2, SM3, SM4, SM5, SM6) which comprises a plurality of pulses (11, 12, 13, 14, 15) over a period (Tp) of the control signal (SM1, SM2, SM3, SM4, SM5, SM6) corresponding to a rotational increment of the rotor, the pulses (11, 12, 13, 14, 15) having a pulse duty cycle (Rln) that increases over the period (Tp) of the control signal (SM1, SM2, SM3, SM4, SM5, SM6).

Description

[0001] DESCRIPTION

[0002] TITLE: Device and method for controlling an electric motor with a stepper type control law

[0003] The invention relates to the field of electric motors and more particularly to a device for controlling an electric motor, an electromechanical actuator intended for driving a blackout device in a home automation installation and a control method.

[0004] The invention applies to the field of home automation installations comprising a device for concealing an opening of a building such as a door or a window. Said concealing device, for example an interior screen, a roller blind or a Venetian blind, is operable by means of an electromechanical actuator. The operation, carried out by an electric motor of the electromechanical actuator, consists of a deployment or a retraction of the concealing device and / or a modification of the orientation, that is to say of the angle of inclination, of slats of the concealing device.

[0005] A synchronous electric motor known for such an electromechanical actuator conventionally comprises a rotor comprising several poles, constituted in particular by permanent magnets, and a stator comprising at least one winding. Such a synchronous motor is for example a “brushless” direct current motor, also designated by the terminology BLDC (Brushless DC), or a permanent magnet synchronous motor, also designated by the English acronym PMSM (Permanent Magnet Synchronous Motor) or a synchronous motor with or without a permanent magnet.

[0006] In the remainder of the description, it is considered in a non-limiting manner that the stator comprises three windings.

[0007] Each stator winding is supplied with a three-phase periodic electrical supply current via three electrical phases, designated U, V and W in the remainder of the description, of a power converter.

[0008] The power converter is configured to generate the supply current on each electrical phase so as to supply each winding or group of windings, in order to create a rotating magnetic field relative to the stator and thus drive the rotor in rotation. The power converter comprises a plurality of switching cells, for example of the MOSFET type, which are controlled in opening and closing by a control law determined by a control device. The control law generates at least one control signal comprising a plurality of pulses. The control law makes it possible to vary a rotation speed of the rotor, in particular in the form of a ramp during transient phases of starting, stopping or modification of a nominal speed to adapt to different situations.

[0009] It is also known to control electric motors using a so-called "step-by-step" control. In such a control, the windings are powered in such a way as to rotate the rotor through a specific angle corresponding to a "step". The rotation angle, or the rotation step of the motor, depends on the number of electrical phases of the stator and the number of pairs of poles of the rotor. Several successive steps can be made in the same direction of rotation with or without the rotor stopping between each step. In other words, a step corresponds to a movement between two stable angular positions of the motor. Such a step-by-step control is carried out in an open loop.

[0010] This control has the advantage of allowing rotation at very low speed and good precision of the rotor position. However, it generates jerks of successive orders which lead to significant variations in a torque exerted by the motor. Thus the stepper control creates vibrations and audible noise during operation of the motor. These vibrations and this noise would be considered particularly annoying in home automation installations. The aim of the invention is to propose a stepper control law requiring little computing power and making it possible to reduce the vibrations and noise emitted compared to a conventional stepper control for an electromechanical actuator usable in home automation applications, particularly inside a building.

[0011] The subject of the invention is a device for controlling a synchronous electric motor comprising at least one rotor and at least one stator, said at least one stator being provided with at least one winding electrically powered by an electrical phase of a power converter, said power converter comprising for each electrical phase, at least one electrical line provided with switching cells, the control device controlling the power converter by means of a step-by-step type control law, characterized in that the control law controls each switching cell by means of a control signal which comprises a plurality of pulses over a period of the control signal corresponding to a rotation step of the rotor, said pulses having a pulse duty cycle increasing over the period of the control signal.

[0012] The power converter contains at least one electrical line, each of the parts of the electrical line connected to an electrical ground of the power converter will be referred to as the "ground side", or "low side" in English, and each of the parts of the electrical line connected to a power supply of the power converter will be referred to as the "power supply side" or "high side" in English. Each electrical line comprises on the ground side a first switching cell, for example of the MOSFET type or "IGBT" type transistor (acronym for the English term Insulated Gate Bipolar Transistor), also referred to as the "low side", and on the power supply side a second switching cell, for example of the MOSFET type or "IGBT" type transistor, also referred to as the "high side", according to a diagram known to those skilled in the art.

[0013] Each winding, or group of windings, of the motor stator is powered by an electrical phase of the power converter. Specifically, each electrical phase is connected to a power line between the ground-side commutation cell and the supply-side commutation cell.

[0014] Each switching cell of the power converter comprises an activated state in which the switching cell allows a current to flow and a blocking state in which said switching cell blocks said current to flow. Each switching cell is controlled by a control signal.

[0015] The control law of the control device corresponds to the set of control signals. The control device is therefore a set of electronic components, and a set of software programs which allow the switching cells of the power converter to be controlled.

[0016] The control law generates, at each rotation step of the rotor, i.e. over a period of the control signal, a control signal for each controlled switching cell. Said control signal comprises a plurality of pulses, one pulse corresponding to the control signal at a high level.

[0017] According to the invention, the control law is of the step-by-step type. One period of the control signal therefore corresponds to one rotation step. In other words, at each step, a new period of the control signal is created. Each signal period also corresponds to a switching sequence of the switching cells. The control is carried out in open loop.

[0018] The modulation duty cycle of the control signal is defined as the ratio between the sum of the pulse durations and the period of the control signal, according to the formula: [Math 1]

[0019] With

[0020] R m: modulation duty cycle of the control signal tin : time of the pulse n

[0021] T P : period of the control signal

[0022] During the period of the control signal, the pulses are produced according to a pulse frequency, or in other words according to a pulse period. The pulse frequency can be fixed or variable over the period of the control signal. The pulse duty cycle is defined as the ratio between the pulse duration and the pulse period, according to the formula:

[0023] [Math 2]

[0024] K pIn _ — T tln In

[0025] With

[0026] Rin: duty cycle of pulse n tin: time of pulse n

[0027] Tin: the period of the pulse n

[0028] So, a pulse duty cycle of 50% means that the control signal is high 50% of the time during the pulse period.

[0029] The pulses of the control signal according to the invention have an increasing duty cycle over each period of the control signal. In other words, over each period of the control signal, the duration of each successive pulse increases. The control signal therefore comprises a plurality of pulses, the duration of each pulse of which increases over the period of the control signal.

[0030] Thus, an average supply voltage of the at least one electrical phase, and therefore a supply current, varies increasingly between a minimum supply value and a maximum supply value, at each period of the control signal.

[0031] The invention, and more particularly the creation of a gradually increasing supply voltage, makes it possible to operate the motor at very low rotation speed with low speed variation and torque variation over a step. Thus, the position of the rotor varies less jerkily, which reduces the noise and vibrations emitted during operation of the motor.

[0032] The invention may also have one or more of the following features taken alone or in combination.

[0033] According to an embodiment not shown, the minimum value of the average supply voltage is zero between two successive periods of the control signal.

[0034] Thus, the movement of the motor has a stop between two successive steps.

[0035] According to one embodiment, the minimum value of the average supply voltage is different from zero between two successive periods of the control signal.

[0036] Thus, the movement of the motor is relatively constant.

[0037] According to one embodiment, the step-by-step control law is implemented by means of a pulse width modulation control law.

[0038] In order to be able to adjust the voltage level supplying the electrical phases of the motor, the stepper control law can be implemented by pulse width modulation (PWM) control law. A so-called "rotating" modulation is a modulation in which a different switching cell of the power converter is modulated at each switching.

[0039] This command has the advantage of being robust and requiring little computing power.

[0040] According to one embodiment, the step-by-step control law is implemented by means of a pulse frequency modulation control law. This reduces a maximum value of the harmonics generated during operation of the motor.

[0041] According to one embodiment, the pulse duty cycle increases linearly over the period of the control signal.

[0042] According to one embodiment, the increase in the pulse duty cycle has a growth slope dependent on a desired rotational speed of the rotor and / or a desired working torque.

[0043] In other words, the pulse duty cycle varies over the period of the control signal and / or with each control signal.

[0044] Thus, the movement of the motor is perfectly adapted to the constraints exerted on it.

[0045] According to one embodiment, a pulse frequency of the control signal varies as a function of a desired engine rotation speed.

[0046] The lower the desired motor rotation speed, the higher the pulse frequency.

[0047] According to one embodiment, the period of the control signal is determined by a stopping condition dependent on a movement of the rotor of the motor by a predefined rotation angle and / or a maximum supply voltage threshold.

[0048] The stop condition determines the period of the control signal and therefore a frequency between each rotation step.

[0049] The rotor movement-dependent stop condition allows a new period of the control signal to begin as soon as the rotor moves one step. In other words, the maximum value of the supply voltage supplied to the electrical phase corresponds to the minimum necessary to move the rotor one rotation step. This stop condition therefore allows a reduction in the motor's electrical consumption by taking into account a load from an environment external to the motor, in particular the weight of a screen of the occulting device to be driven by the motor. The maximum value of the supply voltage therefore varies between each step, or between each period of the control signal.

[0050] The maximum voltage threshold dependent stopping condition corresponds to a supply of the electrical phase as long as the maximum value of the supply voltage has not reached the maximum voltage threshold. The maximum voltage threshold must therefore be chosen so as to ensure the movement of the rotor. In other words, the maximum voltage threshold takes into account the highest load in the external environment of the motor. However, this stopping condition does not require determining the realization of the rotor movement.

[0051] According to one embodiment, the movement of the rotor is determined by at least one position sensor.

[0052] According to one embodiment, the movement of the rotor is determined by means of at least one signal representative of the position of the rotor, different from a signal emitted by a position sensor. For example, the signal representative of the angular position of the rotor may relate to the counter-electromotive force generated by the motor at one or more of the windings as described in document WO2014 / 207387.

[0053] The invention also relates to an electromechanical actuator intended for driving a blackout device in a home automation installation, the electromechanical actuator comprising a synchronous electric motor provided with at least one rotor and at least one stator, the actuator also comprising a power converter, said at least one stator being provided with at least one winding electrically powered by an electrical phase of the power converter, said power converter comprising for each electrical phase, at least one electrical line provided with switching cells, the actuator also comprising a control device according to the invention, for controlling the power converter.

[0054] The invention also relates to a control method implementing a device for controlling a synchronous electric motor comprising at least one rotor and at least one stator, said at least one stator being provided with at least one winding electrically powered by an electrical phase of a power converter, said power converter comprising for each electrical phase, at least one electrical line provided with switching cells, the control device controlling the power converter by means of a step-by-step type control law, characterized in that the control law determines at least one variation of a pulse duty cycle over a period of a control signal corresponding to a rotation step of the rotor, the control device comprising a step of controlling a first switching cell with a first control signal, said control step comprising,as long as a stopping condition is not reached: a first phase in which the control signal comprises a first pulse with a first duty cycle value; then a second phase in which the control signal comprises a second pulse with a second duty cycle value, greater than the first duty cycle value. Thus, the average supply voltage of the at least one electrical phase, and therefore a supply current, varies increasingly between a first supply value and a second supply value.,

[0055] According to one embodiment, the stopping condition depends on a movement of the rotor of the motor by a predefined rotation angle and / or a maximum supply voltage threshold.

[0056] According to one embodiment, the method comprises a phase of determining the movement of the rotor of the motor by a predefined rotation angle.

[0057] According to one embodiment, the phase of determining the movement of the rotor implements at least one position sensor.

[0058] According to one embodiment, the phase of determining the movement of the rotor determines the movement of the rotor relative to a signal representative of the position of the rotor, different from a signal emitted by a position sensor.

[0059] The invention will be better understood, thanks to the following description, which relates to several embodiments according to the present invention, given as non-limiting examples and explained with reference to the appended schematic drawings, in which:

[0060] [Fig. 1] is a schematic representation of a period of a control signal according to the invention for a switching cell;

[0061] [Fig. 2] is a schematic representation of a control law according to the invention over an electrical period;

[0062] [Fig. 3] is a schematic cross-section of an installation according to one embodiment of the invention,

[0063] [Fig. 4] is a schematic perspective view of the installation illustrated in Figure 3,

[0064] [Fig. 5] Figure 3 is a schematic section of an electromechanical actuator of the installation illustrated in Figures 3 and 4, along a section plane passing through an axis of rotation of an output shaft of the electromechanical actuator,

[0065] [Fig. 6] is a schematic representation of a power converter and an electric motor;

[0066] [Fig. 7] is a modeling of a rotation speed, a torque, a position and the currents of each electrical phase of a motor controlled by means of a step-by-step type control law according to the state of the art;

[0067] [Fig. 8] is a model of the rotation speed, torque, position and currents of each electrical phase of the motor controlled by means of a step-by-step type control law according to the invention;

[0068] Only the elements necessary for understanding the invention have been shown. To facilitate reading of the drawings, the same elements bear the same references from one figure to another. We will first describe, with reference to Figures 3 and 4, an installation in accordance with the invention and installed in a building B comprising an opening 1, window or door, equipped with a screen 2 belonging to a blackout device 3, in particular a motorized roller blind.

[0069] The occultation device 3 can alternatively be a roller shutter, a blind with adjustable slats, or even a roller door. In practice, the present invention applies to all types of occultation device comprising a rotating motorized winding shaft.

[0070] A motorized blind according to one embodiment of the invention will be described with reference to Figures 3 to 5.

[0071] The screen 2 of the occulting device 3 is wound on a winding shaft 4, provided in the form of a winding tube, driven by a motorized drive device 5. The screen 2 is movable between a wound position, in particular a high position, and an unwound position, in particular a low position.

[0072] The motorized drive device 5 comprises an electromechanical actuator 11, in particular of the tubular type, making it possible to rotate the winding tube 4 so as to unwind or wind the screen 2 of the occulting device 3, that is to say that the winding tube allows the occulting device 3 to be deployed or folded.

[0073] The blackout device 3 comprises the winding tube 4 for rolling up the screen 2. In the assembled state of the home automation system, the electromechanical actuator 11 is inserted into the winding tube 4.

[0074] The electromechanical actuator 11 and the winding tube 4 are both positioned coaxially along a longitudinal axis X. The inner diameter of the winding tube 4 is substantially equivalent to the outer diameter of the electromechanical actuator 11, so that the electromechanical actuator 11 can be inserted into the winding tube 4 when assembling the occulting device 3.

[0075] In a known manner, the screen 2 of the occultation device 3 is formed by a canvas, which is attached by one end to the winding tube and by the other end to a weighted bar 8.

[0076] The upper rolled-up position of the screen corresponds to the position of the weighted bar at the level of the winding tube and the lower unrolled position corresponds to the position of the weighted bar 8 of the screen 2 at the level of the threshold 7 of the opening 1. The deployment of the screen can be guided by slides 6.

[0077] The winding tube 4 can be arranged inside a box 9 or be visible. The winding tube 4 is rotatable relative to a support 10, such as a cheek, of the box 9. The motorized drive device 5 is controlled by a control unit. The control unit can be, for example, a local control unit 12, where the local control unit 12 can be connected in a wired or wireless connection to a central control unit 13. The control unit 12 is shown here in a radio version with an antenna 12a. The central control unit 13 controls the local control unit 12, as well as other similar local control units distributed throughout the building. It is shown here equipped with a radio antenna 13a.

[0078] The central control unit 13 may be in communication with one or more sensors, not shown, which may be configured to determine, for example, a temperature, an indoor or outdoor brightness.

[0079] A remote control 14, which may be a type of local control unit, and provided with a control keyboard, which comprises selection and possibly display means, furthermore allows a user to intervene on the electromechanical actuator 11 and / or the local control unit 12 and / or central control unit 13.

[0080] The motorized drive device 5 is preferably configured to execute the commands for unrolling or rolling up the screen 2 of the occulting device 3, which can be issued in particular by the remote control 14, the local control unit 12, the central control unit 13 or a sensor.

[0081] We will now describe in more detail the electromechanical actuator 11 belonging to the home automation installation of figures 3 to 5.

[0082] The electromechanical actuator 11 is supplied with electrical energy by a building's electrical supply network, for example by the AC mains network or by a direct current bus, or by means of a battery (not shown), which can be recharged, for example, by a photovoltaic panel. Here, the electromechanical actuator 11 comprises an electrical power supply cable 18 allowing it to be supplied with electrical energy from the mains power supply network.

[0083] Means for controlling the electromechanical actuator 11, allowing the screen 2 of the occulting device 3 to be moved, are constituted by at least one control device 15. The means for controlling the electromechanical actuator 11 comprise hardware and / or software means. By way of non-limiting example, the hardware means may comprise at least one microcontroller.

[0084] The control device 15 is capable of operating an electric motor 16 of the electromechanical actuator 11 and, in particular, of enabling the electric motor 16 to be supplied with electrical energy. Thus, the control device 15 controls, in particular, the electric motor 16, so as to open or close the screen 2, as described previously.

[0085] The control device 15 is in particular configured to control the electric motor 16 so as to set the screen 2 in motion to move it between a current position and a desired stop position. The control device 15 of the electromechanical actuator 11 may comprise an obstacle detection and end-of-travel device (not shown) when the screen 2 is rolled up and when this screen is unrolled.

[0086] The control device 15 comprises a module for receiving orders, in particular radio orders emitted by an order transmitter, such as the remote control 14, intended to control the electromechanical actuator 11. The order receiving module can thus receive position instructions and / or movement orders, such as, for example, opening or closing the screen 2, coming for example from a local control unit 12, a remote control 14, a central control unit 13 or a sensor of the home automation installation. The order receiving module can also allow the reception of orders transmitted by wired means.

[0087] Here, and as illustrated in Figure 5, the control device 15 is arranged inside a casing 17 of the electromechanical actuator 11.

[0088] In another embodiment not shown, the electromechanical actuator 11 is intended to be placed in a U-shaped rail and intended to drive in rotation a winding shaft on which cords associated with the screen are wound.

[0089] The casing 17 of the electromechanical actuator 11 is preferably cylindrical in shape. In one embodiment, the casing 17 may be made of a metallic material. The material of the casing of the electromechanical actuator is in no way limiting and may be different; in particular, it may be plastic.

[0090] The electromechanical actuator 11 also comprises a reducer 19, in particular an epicyclic reducer and an output shaft 20. Advantageously, the electric motor 16 and the reducer 19 are arranged inside the casing 17 of the electromechanical actuator 11.

[0091] The output shaft 20 of the electromechanical actuator 11 is arranged inside the winding tube 4 and, at least in part, outside the casing 17 of the electromechanical actuator 11.

[0092] The output shaft 20 of the electromechanical actuator 11 is coupled by a connecting accessory 30 to the winding tube 4, in particular a wheel-shaped connecting accessory.

[0093] The electromechanical actuator 11 also comprises a torque support 21, mounted at one end of the casing 17 opposite the output shaft 20 and closing the end of the casing 17. The casing 17 and the torque support 21 are fixed in rotation relative to each other. The torque support 21 of the electromechanical actuator 11 is fixed to the support 10 of the box 9 of the concealing device 3. The torque support 21 is also called the “fixed point” of the electromechanical actuator 11.

[0094] The electromechanical actuator 11 also comprises a bearing crown mounted on the casing 17 and free to rotate relative to the casing 17. The bearing crown is fixed in rotation to the winding tube 4, so that the bearing crown provides a bearing function in rotation of the winding tube 4 on the casing 17, near the torque support 21.

[0095] The control device 15 of the electromechanical actuator 11 comprises a rectification circuit D1, D2, D3, D4 for the alternating voltage of the electrical supply network making it possible to transform the alternating current of the supply network into a direct current, and a power converter. The power converter is thus electrically connected to an alternating voltage source V1. The value of the alternating voltage V1 is defined relative to a reference voltage. Alternatively, the rectification circuit for the alternating voltage of the electrical supply network may be external to the electromechanical actuator 11.

[0096] The power converter contains three electrical lines, each of the parts of the electrical lines connected to an electrical ground of the alternating voltage source V1 of the power converter will be called the "ground side", or "low side" in English, and each of the parts of the electrical lines connected to a power supply of the alternating voltage source V1 of the power converter will be called the "power supply side" or "high side" in English. Each electrical line comprises on the ground side a first switching cell M4, M5, M6, for example of the MOSFET type or "IGBT" type transistor (acronym for the English term Insulated Gate Bipolar Transistor), also called the "low side", and on the power supply side a second switching cell M1, M2, M3, for example of the MOSFET type or "IGBT" type transistor, also called the "high side", as shown in Figure 6.

[0097] Electrical phases U, V, W supplying windings, or group of windings, Ph1, Ph2, Ph3 of the motor stator are connected by the power lines of the inverter. More particularly, each phase U, V, W is connected to a power line of the power converter, between the switching cell on the ground side M4, M5, M6 and the switching cell on the power side M1, M2, M3.

[0098] Each switching cell M1, M2, M3, M4, M5, M6 of the power converter comprises an activated state in which the switching cell M1, M2, M3, M4, M5, M6 allows a current to flow and a blocking state in which said switching cell M1, M2, M3, M4, M5, M6 blocks said current flow. Each switching cell is controlled by a control signal.

[0099] A control law of the power converter corresponds to the set of control signals. The electrical converter thus supplies electrical energy to the windings, or group of windings, Ph1, Ph2, Ph3, so as to produce the rotating electromagnetic field causing the rotor of the electric motor 16 to rotate. Finally, the power converter includes an electrical resistor R2 positioned in series between the electrical supply network V1 and the switching cell M6. This resistor is also called shunt resistor R2.

[0100] The electric motor 16 comprises a stator and a rotor positioned coaxially around the longitudinal axis or axis of rotation X.

[0101] The electric motor 16 is synchronous, for example a “brushless” motor with electronic commutation, or a permanent magnet synchronous motor, called “PMSM” (acronym for the English term Permanent Magnetic Synchron Motor), or a synchronous motor with or without permanent magnets.

[0102] The motor comprises a rotor provided with poles and a stator comprising the windings, or group of windings Ph1, Ph2, Ph3, in this case three, electrically connected to each other, as illustrated schematically in figure 6. More precisely, the windings Ph1, Ph2, Ph3 are connected to each other so that when they are alternately traversed by a supply current, they produce a rotating electromagnetic field which drives the rotor in rotation.

[0103] Each winding, or group of windings, Ph1, Ph2, Ph3 of the stator is supplied by an electrical phase U, V, W as can be seen in figure 6.

[0104] The control device 15 of the electromechanical actuator 11 also comprises a device for determining the angular position of the rotor (not shown). This device is configured to provide the control device 15 with a signal representative of the angular position of the rotor relative to the stator. The angular position is here defined relative to the positions of the windings Ph1, Ph2, Ph3 on the stator and expressed in the form of an angle, called an electrical angle, which can take a value in the interval [0°, 360°] modulo 360°. Thus, the angle 360° corresponds to the angle 0°. The original position of the angle is here chosen to be equal to 0°. According to one embodiment, the determination device can be a physical sensor. The device for determining the angular position of the rotor comprises at least one sensor positioned in a fixed manner relative to the stator, preferably integrated therein.Preferably, this angular position determination device comprises at least one Hall effect sensor with binary output. In a known manner, such sensors are configured to react to the magnetic fluxes of the rotor magnets and to each provide a signal representative of the angular position of the rotor making it possible to determine the position and speed of the rotor. In other words, the at least one sensor is capable of providing an angular position of the rotor of the electric motor around the X axis and therefore an equivalent angular position of the output shaft of the electromechanical actuator 11. Alternatively, other types of sensors may also be used, such as wheel encoders.According to another embodiment, the device for determining the angular position of the rotor determines the position of the rotor by means of at least one signal representative of the position of the rotor, different from a signal emitted by a position sensor, for example by measuring the counter-electromotive force generated by the motor at one or more of the windings Ph1, Ph2, Ph3.

[0105] The step-by-step type control law according to the invention will be described in detail with reference to Figures 1 and 2. The control law comprises a control signal SMI, SM2, SM3, SM4, SMS, SM6 for each switching cell M1, M2, M3, M4, M5, M6. The control law generates, at each rotation step of the rotor, i.e. over a period T Pof the control signal, a control signal SMI, SM2, SM3, SM4, SMS, SMS for each controlled switching cell M1, M2, M3, M4, M5, M6. Said control signal SMI, SM2, SM3, SM4, SMS, SM6 comprises a plurality of pulses h, I2, I3, k, I5, a pulse h, I2, I3, k, I5, corresponding to the control signal at a high level.

[0106] According to the invention, the control law is of the step-by-step type. In such a control, the power supply to the windings Ph1, Ph2, Ph3 is carried out so as to rotate the rotor by a determined angle corresponding to a "step". The rotation angle, or the rotation step of the motor, depends on the number of electrical phases of the stator and the number of pairs of poles of the rotor. Several successive steps can be carried out in the same direction of rotation with or without a stop of the rotor between each step. In other words, a step corresponds to a movement between two stable angular positions of the motor. Such a step-by-step control is carried out in an open loop.

[0107] Period T P of the control signal SMI, SM2, SM3, SM4, SMS, SMS therefore corresponds to a rotation step. In other words, at each step, a new period Tp of the control signal SMI, SM2, SM3, SM4, SMS, SMB is created.

[0108] A modulation duty cycle of the control signal SMI, SM2, SM3, SM4, SMS, SMB is the ratio between the sum of the durations tu, ti2, ti3, ti4, tis of pulse h, I2, h, k, Is, and the period T P of the control signal, according to the formula:

[0109] [Math 1]

[0110] With

[0111] R m : modulation duty cycle of the control signal tin : time of the pulse n

[0112] T P : period of the control signal

[0113] During period T P of the control signal SMI, SM2, SM3, SM4, SMS, SMB, the pulses h, I2, I3, k, Is, are produced according to a pulse frequency, or in other words according to a pulse period Ti. The pulse frequency can be fixed or variable over the period T P of the control signal SMI, SM2, SM3, SM4, SMS, SMS.

[0114] The pulse duty cycle is the ratio between the duration tu, ti2, ti3, ti4, tis of the pulse h, I2, I3, k, I5 and the period Ti of the pulse h, I2, I3, k, I5, according to the formula:

[0115] [Math 2]

[0116] With

[0117] Rin: duty cycle of pulse n tin: time of pulse n Tin: period of pulse n

[0118] Thus, a pulse duty cycle Rin of 50% means that the control signal SMI, SM2, SMS, SM4, SM5, SM6 is at high level 50% of the time of the pulse period Ti h, I2, h, k, I5.

[0119] The pulses h, I2, h, I4, of the control signal SMI, SM2, SM3, SM4, SMS, SMS according to the invention have an increasing duty cycle. In other words, over each period Tp of the control signal SMI, SM2, SM3, SM4, SMS, SMS, the duration tu, ti2, ti3, ti4, tis of each successive pulse h, I2, I3, I4, h increases. The control signal SMI, SM2, SM3, SM4, SMS, SMS therefore comprises a plurality of pulses h, I2, I3, k, h, the duration of each pulse h, I2, h, k, b of which is increasing over the period Tp of the control signal SMI, SM2, SM3, SM4, SMS, SMS.

[0120] As illustrated in Figure 2, the control signals of two switching cells are modulated over a period T Pof the control signal SMI, SM2, SM3, SM4, SMS, SMS. In a known manner, when the switching cell M1 is modulated and another cell M5 or M6 is switched to a high state, the electrical phase U is powered, when the switching cell M2 is modulated and another cell M4 or M6 is switched to a high state, the electrical phase V is powered, when the switching cell M3 is modulated and another cell M4 or M5 is switched to a high state, the electrical phase W is powered.

[0121] Thus, an average supply voltage of each electrical phase U, V, W, and therefore a supply current, varies increasingly between a minimum supply value and a maximum supply value at each period Tp of the control signal SMI, SM2, SM3, SM4, SM5, SM6.

[0122] According to an embodiment not shown, the minimum value of the average supply voltage is zero between two successive periods Tp of the control signal SMI, SM2, SM3, SM4, SM5, SM6.

[0123] Thus, the movement of the motor has a stop between two successive steps.

[0124] According to one embodiment, the minimum value of the average supply voltage is different from zero between two successive periods Tp of the control signal SMI, SM2, SM3, SM4, SM5, SM6. Thus, the movement of the motor is relatively constant.

[0125] According to one embodiment, the step-by-step control law is implemented by means of a pulse width modulation control law.

[0126] In order to be able to adjust the voltage level supplying the electrical phases of the motor, the step-by-step control law can be achieved by pulse width modulation (PWM) control law. A so-called "rotating" modulation is a modulation in which a switching cell M1, M2, M3, M4, M5, M6 different from the power converter is modulated at each switching.

[0127] This command has the advantage of being robust and requiring little computing power.

[0128] According to one embodiment, the step-by-step control law is implemented by means of a pulse frequency modulation control law. This reduces a maximum value of the harmonics generated during operation of the motor.

[0129] According to one embodiment, the pulse duty cycle Rin increases linearly over the period Tp of the control signal SMI, SM2, SM3, SM4, SMS, SMS.

[0130] According to one embodiment, the increase in the pulse duty cycle in has a growth slope dependent on a desired rotational speed of the rotor and / or a desired working torque.

[0131] According to one embodiment, a pulse frequency of the control signal SMI, SM2, SM3, SM4, SM5, SM6 varies as a function of a desired motor rotation speed.

[0132] According to one embodiment, the period Tp of the control signal SMI, SM2, SM3, SM4, SMS, SMS is determined by a stopping condition dependent on a movement of the rotor of the motor by a predefined rotation angle and / or a maximum supply voltage threshold.

[0133] The stop condition determines the period Tp of the control signal SMI, SM2, SM3, SM4, SMS, SMS and therefore a frequency between each rotation step.

[0134] The rotor movement-dependent stopping condition allows a new period Tp of the control signal SMI, SM2, SM3, SM4, SMS, SMS to begin as soon as the rotor has moved one step. In other words, the maximum value of the supply voltage supplied to the electrical phase U, V, W corresponds to the minimum necessary to move the rotor one rotation step. This stopping condition therefore allows a reduction in the electrical consumption of the motor by taking into account a load from an environment external to the motor, in particular the weight of a screen 2 of the occulting device 3 to be driven by the motor. The maximum value of the supply voltage therefore varies between each step, or between each period Tp of the control signal SMI, SM2, SM3, SM4, SMS, SMS.

[0135] The stopping condition dependent on a maximum voltage threshold corresponds to a supply of the electrical phase U, V, W as long as the maximum value of the supply voltage has not reached the maximum voltage threshold. The maximum voltage threshold must therefore be chosen so as to ensure the movement of the rotor. In other words, the maximum voltage threshold takes into account the highest load of the external environment of the motor. However, this stopping condition does not require determining the realization of the rotor movement.

[0136] The control device 15 implements a control method comprising a step of controlling a first switching cell M1, M2, M3, M4, M5, M6 with a first control signal SMI, SM2, SM3, SM4, SMS, SMS, said control step comprising, as long as a stop condition is not reached: a first phase in which the control signal SMI, SM2, SM3, SM4, SM5, SM6 comprises a first pulse h with a first duty cycle value; then a second phase in which the control signal SMI, SM2, SM3, SM4, SM5, SM6 comprises a second pulse h with a second duty cycle value, greater than the first duty cycle value.

[0137] According to one embodiment, the method comprises a phase of determining the movement of the rotor of the motor by a predefined rotation angle using at least one position sensor and / or determining the movement of the rotor by means of at least one signal representative of the position of the rotor, different from a signal emitted by the position sensor.

[0138] Figure 7 illustrates a modeling of a rotation speed, a torque, a position and the currents of each electrical phase U, V, W, of a motor controlled by means of a step-by-step type control law according to the state of the art, the control imposing a speed setpoint of 30 rpm and a resistive torque of 10 mNm.

[0139] The current of each motor phase U, V, W has a substantially square wave shape at each step of the motor or over each period Tp of the control signal. Thus, at each step, the rotation speed has fluctuations varying by 44rad / s, the motor torque varies by 22mNm and the rotor position quickly reaches the position of step P'1 then oscillates around this position before stabilizing.

[0140] For comparison, Figure 8 illustrates a modeling of the rotation speed, torque, position and currents of each electrical phase U, V, W, of the motor controlled by means of the step-by-step type control law according to the invention, the control imposing a speed setpoint of 30 rpm and a resistive torque of 10 mNm as previously.

[0141] The current of each motor phase U, V, W has a substantially linearly increasing shape at each step of the motor or over each period Tp of the control signal. Thus, at each step, the rotation speed has fluctuations varying by 16rad / s, the motor torque varies by 2mNm, it is therefore highly smoothed, and the position P1 of the rotor is reached progressively. The movement of the motor achieved with the control law according to the invention allows a less jerky movement than in the state of the art. The invention, and more particularly the creation of a gradually increasing supply voltage, makes it possible to operate the motor at very low rotation speed with a small variation in speed and a small variation in torque over a step. Thus, the position of the rotor varies in a less jerky manner, which reduces the noise and vibrations emitted during operation of the motor.

[0142] Of course, the invention is not limited to the embodiments described and shown in the attached figures. Modifications remain possible, particularly from the point of view of the constitution of the various elements or by substitution of technical equivalents, without departing from the scope of protection of the invention.

Claims

CLAIMS 1. Control device (15) for a synchronous electric motor (16) comprising at least one rotor and at least one stator, said at least one stator being provided with at least one winding (Ph1, Ph2, Ph3) electrically powered by an electrical phase (U, V, W) of a power converter, said power converter comprising for each electrical phase (U, V, W), at least one electrical line provided with switching cells (M1, M2, M3, M4, M5, M6), the control device (15) controlling the power converter by means of a step-by-step type control law, characterized in that the control law controls each switching cell (M1, M2, M3, M4, M5, M6) by means of a control signal (SMI, SM2, SM3, SM4, SM5, SMS) which comprises a plurality of pulses (h, h, I3, I4, I5) over a period (T P) of the control signal (SMI, SM2, SM3, SM4, SMS, SMS) corresponding to a rotation step of the rotor, said pulses (h, I2, I3, k, I5) having a pulse duty cycle (Rin) increasing over the period (T P ) of the control signal (SMI, SM2, SM3, SM4, SMS, SMS).

2. Control device (15) according to claim 1, in which the pulse duty cycle (Rin) increases linearly over the period (T P ) of the control signal (SMI, SM2, SM3, SM4, SMS, SMS).

3. Control device (15) according to claim 1 or 2, wherein the increase in the pulse duty cycle (Rin) has a growth slope dependent on a desired rotational speed of the rotor and / or a desired working torque.

4. Control device (15) according to any one of the preceding claims, wherein a pulse frequency of the control signal (SMI, SM2, SM3, SM4, SMS, SMS) varies as a function of a desired engine rotation speed.

5. Control device (15) according to any one of the preceding claims, in which the period (T P ) of the control signal (SMI, SM2, SM3, SM4, SMS, SMS) is determined by a stopping condition dependent on a movement of the motor rotor (16) by a predefined rotation angle and / or a maximum supply voltage threshold.

6. Control device (15) according to claim 5, wherein the movement of the rotor is determined by at least one position sensor.

7. Control device (15) according to claim 5, in which the movement of the rotor is determined by means of at least one signal representative of the position of the rotor, different from a signal emitted by a position sensor.

8. Electromechanical actuator (11) intended for driving a blackout device (3) in a home automation installation, the electromechanical actuator (11) comprising a synchronous electric motor (16) provided with at least one rotor and at least one stator, the actuator (11) also comprising a power converter, said at least one stator being provided with at least one rotor and at least one stator. at least one winding (Ph1, Ph2, Ph3) electrically powered by an electrical phase (U, V, W) of the power converter, said power converter comprising for each electrical phase (U, V, W), at least one electrical line provided with switching cells (M1, M2, M3, M4, M5, M6), the actuator also comprising a control device (15) according to at least one of the preceding claims, for controlling the power converter.

9. Control method implementing a control device (15) for a synchronous electric motor (16) comprising at least one rotor and at least one stator, said at least one stator being provided with at least one winding (Ph1, Ph2, Ph3) electrically powered by an electrical phase (U, V, W) of a power converter, said power converter comprising for each electrical phase (U, V, W), at least one electrical line provided with switching cells (M1, M2, M3, M4, M5, M6), the control device controlling the power converter by means of a step-by-step type control law, characterized in that the control law determines at least one variation of a pulse duty cycle (Rin) over a period (T P) of a control signal (SMI, SM2, SM3, SM4, SMS, SMS) corresponding to a rotation step of the rotor, the control device (15) comprising a step of controlling a first switching cell with a first control signal, said control step comprising, as long as a stopping condition is not reached: a first phase in which the control signal comprises a first pulse with a first duty cycle value; then a second phase in which the control signal comprises a second pulse with a second duty cycle value, greater than the first duty cycle value.

10. Method according to claim 9, wherein the stopping condition depends on a movement of the rotor of the motor by a predefined rotation angle and / or a maximum supply voltage threshold.

11. Method according to any one of claims 9 or 10, comprising a phase of determining the movement of the rotor of the motor by a predefined rotation angle.

12. Method according to claim 11, in which the phase of determining the movement of the rotor implements at least one position sensor.

13. Method according to any one of claims 11 or 12, in which the phase of determining the movement of the rotor determines the movement of the rotor relative to a signal representative of the position of the rotor, different from a signal emitted by a position sensor.

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