Method for controlling an electromechanical actuator, electromechanical actuator and associated shading device

Abstract

Method for controlling an electromechanical actuator, electromechanical actuator and associated shading device. The present invention relates to a method for controlling an electromechanical actuator comprising a motor, the method comprising: determining (102) a setpoint speed (Vc) of the motor; generating (106) control signals from an inverter; supplying (108) by the inverter electrical supply currents, according to the control signals, in order to rotate the motor at a rotational speed (Vm); and measuring (110) the rotational speed (Vm) of the motor, by a speed sensor. A frequency of the generated control signals is fixed and determined according to the setpoint speed (Vc), and a duty cycle of the control signals is adapted according to the rotational speed (Vm) of the motor, measured by the speed sensor, so that the rotational speed (Vm) of the motor corresponds to the setpoint speed (Vc).Figure for the abbreviation: Figure 5.

Description

Title of the invention: Method for controlling an electromechanical actuator, electromechanical actuator and associated obscuring device

[0001] The present invention relates to a method for controlling an electromechanical actuator, an electromechanical actuator and an associated occulting device.

[0002] To control an asynchronous motor, it is known to use a phase-shifting capacitor, as described in EP1918506A2. It is also known to use a control method called U / f, in which the ratio between a voltage applied to the asynchronous motor and the motor control frequency remains constant to impose an output speed of the motor.

[0003] However, such a control method is complex and involves high computing resources in order to adapt the control by varying the control frequency to vary the rotational speed of the motor.

[0004] The aim of the invention is then to control an asynchronous motor with speed variations in a simpler way and without involving high computing resources.

[0005] To this end, the invention relates to a method for controlling an electromechanical actuator comprising a polyphase asynchronous motor, the method comprising at least the following steps: - determination of a setpoint speed for the motor, by a control device; - generation of control signals for an inverter, by the control device; - the inverter supplies electrical power, according to the control signals, to power the motor; the electrical power supplies supply the motor windings to rotate the motor at a specified speed, the inverter being powered by a direct current; and - measurement of the motor's rotational speed, by a speed sensor.

[0006] According to the invention, a frequency of the generated control signals is fixed and determined as a function of the setpoint speed, and in that a duty cycle of the control signals is adapted as a function of the motor's rotational speed, measured by the speed sensor, so that the motor's rotational speed corresponds to the setpoint speed.

[0007] Thanks to the invention, only the duty cycle is modified to vary the motor speed. Calculating the duty cycle is simpler and requires fewer resources than calculating a control frequency, which is performed for U / f control. Thus, using a fixed control frequency simplifies the control of the asynchronous motor and therefore reduces the resources needed to control motor speed variations, without limiting or degrading the motor's overall performance.

[0008] According to other advantageous aspects of the invention, the piloting method comprises one or more of the following features, taken individually or in all technically possible combinations:

[0009] - The electrical supply currents are generated from the signals of pulse width modulation control.

[0010] - The electrical supply currents are pseudo-sinusoidal.

[0011] - The piloting method includes a step of recording a curve optimized frequency characteristic of control signals as a function of set speed, such that, when the motor rotates at a given set speed and when the control signals have a frequency equal to the frequency given by the optimized characteristic curve for that given set speed, a motor efficiency at the given set speed is maximized, and in which the frequency of the generated control signals is determined as a function of the set speed from the optimized characteristic curve.

[0012] - The optimized characteristic curve includes a first point corresponding to a a setpoint speed of 25Hz and a control signal frequency of 45Hz, and a second point corresponding to a setpoint speed of 50Hz and a control signal frequency of 80Hz.

[0013] The invention also relates to an electromechanical actuator comprising a polyphase asynchronous motor, comprising several windings, an inverter, connected to the motor, and a control device, the electromechanical actuator being configured to implement the method described above.

[0014] According to other advantageous aspects of the invention, the electromechanical actuator comprises one or more of the following features, taken individually or in all technically possible combinations:

[0015] - The inverter comprises several branches, each branch comprising several switches, with a midpoint of each branch being connected to the motor.

[0016] - The motor is a two-phase asynchronous motor, comprising two windings connected to each other by a neutral point; - the inverter comprises three branches, each branch comprising two switches, the midpoint of each branch being located between the two switches of the branch; - the midpoints of the first and second branches among the three branches are respectively connected to one of the motor windings; and - the midpoint of the third branch is connected to the neutral point.

[0017] The invention also relates to a blackout device comprising the electromechanical actuator described above and a blackout screen, driven by the electromechanical actuator, the blackout screen being configured to be moved when the motor is running.

[0018] Advantageously, the shading device further includes a capacitive rectifier, connected to the inverter and configured to convert alternating electric current into direct electric current to power the inverter.

[0019] The invention will become clearer upon reading the following description, given solely by way of non-limiting example, and made with reference to the drawings in which: - [Fig.1] [Fig.1] schematically represents an occultation device according to one embodiment of the invention; - [Fig.2] [Fig.2] is an electrical diagram of an electromechanical actuator according to an embodiment of the invention, which belongs to the occultation device of the [Fig.1]; - [Fig.3] [Fig.3] is a graph representing a command frequency in function of a setpoint speed of an asynchronous motor of the electromechanical actuator of the [Fig.2], controlled according to a method according to the invention; - [Fig.4] [Fig.4] is a graph representing the intensity of a current electrical power supply generated by an inverter belonging to the electromechanical actuator of [Fig.2]; and - [Fig. 5] [Fig. 5] is a flowchart of a control process according to the invention.

[0020] Figure 1 is a view of a blackout device 10 according to the invention, comprising a screen 12, a winding shaft 14, and an electromechanical actuator 16. The screen 12 is, for example, a blackout fabric or a set of slats, such as a roller shutter. The screen 12 is fixed to the winding shaft 14 and driven in movement by the winding shaft 14. For example, the screen 12 is configured to be moved in translation along a direction of movement D, by being wound or unwound around of the winding shaft 14. The winding shaft 14 is configured to be driven in rotation by the electromechanical actuator 16.

[0021] In the example shown in [Fig. 2], the electromechanical actuator 16 is connected to a power source 18 by a phase conductor 19 and a neutral conductor 21. The source 18 supplies alternating current. The source 18 is, for example, an electrical outlet connected to the mains power supply. In the example in [Fig. 2], the shading device 10 further includes a capacitive rectifier 22, connected between the source 18 and the electromechanical actuator 16. The capacitive rectifier 22 is configured to convert the alternating current received from the source 18 into direct current. Alternatively, a rectifier of a different type than capacitive is connected between the source 18 and the electromechanical actuator 16. Alternatively, the rectifier 22 is integrated into the electromechanical actuator 16.

[0022] In an alternative not shown, the source 18 provides a direct electric current and is directly connected to the electromechanical actuator 16 or even integrated into the electromechanical actuator 16, for example if the source 18 consists of batteries.

[0023] The electromechanical actuator 16 comprises an asynchronous motor 24, also referred to simply as the motor in what follows. The motor 24 is polyphase and comprises a plurality of windings 26. The windings 26, in particular an output of the windings 26, are advantageously connected to each other via a neutral point 28. In the example of [Fig. 2], the motor 24 comprises two windings 26 and is therefore a two-phase asynchronous motor. An output of each winding 26 is connected to the neutral point 28. The windings 26 are, for example, included in a stator of the motor 24. A rotor of the motor 24 is, for example, made of a metal cage, also known as a squirrel cage.

[0024] The electromechanical actuator 16 further comprises an inverter 30, connected to the motor 24. Advantageously, and as shown in [Fig.2], the inverter 30 is connected to the capacitive rectifier 22. The inverter 30 is thus connected between the motor 24 and the capacitive rectifier 22.

[0025] Advantageously, the inverter 30 comprises a plurality of branches. In the example of [Fig.2], the inverter comprises three branches 31, 32 and 33. Each branch 31, 32, 33 comprises a plurality of switches, for example two switches, respectively 41 and 42 for branch 31, 43 and 44 for branch 32 and 45 and 46 for branch 33.

[0026] Advantageously, the switches are semiconductor switches, transistors, for example insulated-gate bipolar transistors or IGBTs, or field-effect transistors with insulated gate, or MOSFET, from the English "Metal Oxide Semiconductor Field Effect Transistor".

[0027] Each branch 31, 32, 33 comprises a midpoint, respectively 51, 52, 53, each midpoint 51, 52, 53 being connected to the motor 24. Advantageously, and as shown in [Fig. 2], each midpoint 51, 52, 53 is located between the switches of its respective branch 31, 32, 33. Thus, midpoint 51 is located between switches 41 and 42, midpoint 52 is located between switches 43 and 44, and midpoint 53 is located between switches 45 and 46.

[0028] Advantageously, the midpoints of a first branch and a second branch among the three branches 31, 32 and 33 are respectively connected to one of the windings 26 of the motor 24, and the midpoint of the third branch is connected to the neutral point 28. In the example of [Fig.2], the midpoints 51 and 52 are respectively connected to one of the windings 26, in particular to an input of the windings 26, and the midpoint 53 is directly connected to the neutral point 28.

[0029] According to an alternative configuration not shown, the motor 24 is a three-phase motor, in either a star or delta configuration. In the case of a star motor, the motor 24 comprises three windings 26, connected to each other via the neutral point 28. Each midpoint 51, 52, 53 of the inverter 30 is then connected to one of the windings 26 of the motor 24. In the case of a delta motor, the three windings 26 are connected to each other in delta, and are connected to the midpoints 51, 52, 53 of the inverter 30. For example, a first winding 26 is connected to the midpoints 51 and 52, a second winding 26 is connected to the midpoints 52 and 53, and a third winding 26 is connected to the midpoints 53 and 51.

[0030] The electromechanical actuator 16 further includes an electronic control unit 55 comprising a control device 56. The control device 56 is for example made in the form of a programmable logic component, such as an FPGA (Field Programmable Gate Array), or an integrated circuit, such as an ASIC (Application Specified Integrated Circuit).

[0031] In general, the control device 56 includes software components, stored in unrepresented memory and executable by a processor associated with the memory and also unrepresented.

[0032] The control device 56 is connected to switches 41 to 46 in order to control these switches by switching between a conducting configuration, in which the switches carry an electric current, and a blocked configuration, in which the switches do not carry an electric current. The connection of the control device 56 to each switch 41 to 46 is not shown.

[0033] In the case where the switches 41 to 46 are transistors, the control device 56 is connected to the gate of each switch 41 to 46 for switching controls.

[0034] The control device 56 is configured to regulate a rotational speed Vm of the motor 24. For this purpose, the control device 56 advantageously includes a Proportional Integral Derivative, or PID, controller.

[0035] The electromechanical actuator 16 comprises at least one speed sensor 58. Alternatively, the electromechanical actuator 16 comprises several speed sensors 58, each speed sensor 58 being formed by a Hall effect sensor. The speed sensor(s) 58 are connected to the control device 56, preferably by a respective connecting line 59. The speed sensor(s) 58 advantageously cooperate with a pole wheel mounted on the rotor. The speed sensor(s) 58 can be used as position sensors for the screen 12.

[0036] Advantageously, the electromechanical actuator 16 also includes sensors 62 for the intensity of an electric current flowing in each of the branches 31, 32, 33. In the example of [Fig.2], the intensity sensors 62 are shunt resistors, connected in series to one of the branches 31, 32, 33, a voltage measurement being taken across these resistors, and received by the control device 56 in order to deduce the intensity flowing in each branch 31, 32, 33. Alternatively, the intensity sensors 62 are Rogowski coils, or magnetoresistive sensors, or MEMS.

[0037] The blackout device 10 advantageously includes a control unit, for example, a remote control 66, connected with or without wire to the electromechanical actuator 16 to control the blackout device 10.

[0038] A method for controlling the electromechanical actuator 16 is described below, with reference in particular to [Fig.5].

[0039] According to one example, a user manipulates the remote control 66, for example by pressing one of its buttons 68, to move the screen 12. The electronic control unit 55 receives the command issued by the remote control 66 during an optional control step 102, for example via a receiver, not shown, included in the electronic control unit 55. The user can, for example, specify a slow or fast speed for moving the screen 12

[0040] The control device 56 then determines a setpoint speed Vc of the motor 24 during a determination step 104. For example, the control device 56 determines the setpoint speed Vc corresponding to the speed of movement of the screen 12 corresponding to the control command. For example, a slow speed of movement of the screen corresponds to a setpoint speed Vc of the motor 24 equal to 25Hz, or 1500 revolutions per minute, and a fast screen movement speed 12 corresponds to a motor setpoint speed Vc equal to 50Hz, or 3000 revolutions per minute.

[0041] Alternatively, the control device 56 includes a timer or clock and performs step 104, for example at a fixed time, without the need for control step 102. Alternatively, the control command received by the electronic control unit 55 can originate automatically from a sensor or remote control, without user intervention.

[0042] The control device 56 generates control signals for the inverter 30 during a generation step 106. The control signals are, for example, electrical pulses sent to the switches 41 to 46 in order to control them in switching. Advantageously, a control signal is sent to each switch 41 to 46.

[0043] During generation step 106, the control device 56 generates control signals at a fixed frequency fcmde. The frequency fcmde of the control signals is also called the control frequency. The control frequency fcmde is determined as a function of the setpoint speed Vc determined in determination step 104. Advantageously, the control signals are generated in step 106 also as a function of the current intensities in branches 31, 32, and 33 measured by the current sensors 62.

[0044] Advantageously, the control frequency fcmde of the control signals generated during the generation step 106 is determined as a function of the setpoint speed Vc from an optimized characteristic curve C, visible in [Fig.3].

[0045] In this case, the control method includes a preliminary recording step 100, carried out, for example, during the construction of the electromechanical actuator 16. The preliminary recording step 100 consists of recording the optimized characteristic curve C of the control frequency fcmde as a function of the setpoint speed Vc. The optimized characteristic curve C is determined such that, when the motor 24 rotates at a given setpoint speed Vc and the control signals have a frequency fcmde equal to the frequency given by the optimized characteristic curve C for this given setpoint speed Vc, the efficiency of the motor 24 at the given setpoint speed Vc is maximized.

[0046] The efficiency of the motor 24 is the ratio of the output power and the input power of the motor 24.

[0047] The optimized characteristic curve C is advantageously established by a series of tests, during which the efficiency of the motor 24 is calculated as a function of the control frequency fcmde, for different setpoint speeds Vc. For each speed of Given the setpoint Vc, the control frequency corresponding to maximum efficiency is recorded. Thus, the optimized characteristic curve C of the control frequency fcmde as a function of the setpoint speed Vc allows, during generation step 106, the determination of the control frequency fcmde to obtain maximum efficiency of motor 24.

[0048] In the example of [Fig. 3], the optimized characteristic curve C comprises a first point A corresponding to a setpoint speed Vc of 25 Hz and a control signal frequency fcmde of 45 Hz, and a second point B corresponding to a setpoint speed of 50 Hz and a control signal frequency fcmde of 80 Hz. According to one example, when the user indicates a slow travel speed, the control device 56 determines, during the generation step 106, a control signal with a frequency fcmde equal to 45 Hz, and when the user indicates a fast travel speed, the control device 56 determines, during the generation step 106, a control signal with a frequency fcmde equal to 80 Hz.

[0049] Thus, the fixed control frequency fcmde corresponding to a given setpoint speed Vc is much greater than the speed, or frequency, of rotation of the rotor.

[0050] Alternatively, the control frequency fcmde is, for example, determined in step 106 by a constant function or even a piecewise constant function, chosen by the manufacturer of the electromechanical actuator 16.

[0051] Advantageously, during the generation step 106, the control device 56 also determines a duty cycle for the control signals. The duty cycle is, for example, initially a default duty cycle, enabling start-up; that is, the duty cycle is established for a torque greater than the nominal torque, for example, for a torque equal to one and a half times the nominal torque of the electromechanical actuator 16.

[0052] Advantageously, during the generation step 106, the control signals are generated by the control device 56 by pulse width modulation, or PWM.

[0053] During a supply step 108, the inverter 30 generates supply currents, with a frequency equal to the control frequency fcmde, to power the motor 24, according to the control signals generated in step 106. Each supply current has an intensity I and a voltage U. In the example of [Fig. 2], the inverter 30 thus supplies each winding 26 of the motor 24 with a supply current, in order to rotate the motor at the rotational speed Vm. The motor 24 then drives the winding shaft 14, which moves the screen 12.

[0054] The electric supply currents supplied to each winding 26 are identical but out of phase by 90° with respect to each other, for the example of [Fig.2] with two windings 26.

[0055] The intensity I of one of the electrical supply currents is shown in [Fig.4],

[0056] In order to power the motor 24, the inverter 30 is supplied with a direct current. The direct current is advantageously supplied by the capacitive rectifier 22, or alternatively, directly by the source 18. In one example, the inverter 30 is supplied with direct current as soon as the capacitive rectifier 22 is connected to the source 18. Alternatively, in step 108, the control device 56 commands the capacitive rectifier 22 to supply the inverter 30 with direct current.

[0057] Advantageously, the power supply currents provided by the inverter 30 are pseudo-sinusoidal. Thus, the generation of the control signals that are sent to each switch 41 to 46, during step 106, is simplified and requires less computing power and energy compared to a control system where the power supply currents are sinusoidal. In particular, the intensity I of the power supply currents is pseudo-sinusoidal, as can be seen in [Fig. 4].

[0058] The supply currents, more precisely, the value of the voltage U representing the supply currents, depends directly on the duty cycle and allows the motor 24 to rotate at the rotational speed Vm. Since the motor 24 is an asynchronous motor, the rotational speed Vm of the motor 24 is not equal to the frequency of the supply currents, and therefore is not equal to the control frequency fcmde.

[0059] The speed sensors 58 measure the rotational speed Vm of the motor 24 during a measurement step 110.

[0060] If the rotational speed Vm of the motor 24 is substantially equal to the setpoint speed Vc, then the control unit 56 continues to control the inverter, maintaining the duty cycle of the control signals unchanged, and performs measurement step 110 again. Iterative operation is then implemented. "Substantially equal to the setpoint speed Vc" means equal to the setpoint speed Vc plus or minus 5%. A tolerance on this setpoint speed Vc is thus accepted.

[0061] If the rotational speed Vm of the motor 24 differs from the setpoint speed Vc, the control unit 56 repeats steps 106 to 110. An iterative operation is then implemented. Generation step 106 is performed by modifying the duty cycle of the control signals. This modifies the voltage U of the motor control signal supplied in step 108; in particular, this modifies the amplitude of voltage. This therefore modifies the rotational speed Vm of motor 24. Thus, the duty cycle of the control signals is adapted according to the rotational speed Vm so that the latter corresponds to the setpoint speed Vc.

[0062] The duty cycle of the control signals thus varies according to the torque seen by the motor, which tends to vary the rotational speed Vm measured by the speed sensor 58 in step 110, in order to maintain the setpoint speed Vc.

[0063] Thus, the control frequency fcmde does not change when the rotation speed Vm of the motor 24 changes.

[0064] The method of controlling an electromechanical actuator as described is particularly well suited when the electromechanical actuator includes a friction brake.

[0065] Advantageously, the electrical diagram and the method make it possible to do without a bulky phase-shifting capacitor, conventionally used with a two-phase asynchronous motor, which is of particular interest in certain applications, such as motorization for outdoor Venetian blinds or 120V mains supplies for which the phase-shifting capacitor must be particularly large.

[0066] Any feature described for an embodiment or variant in the foregoing may be implemented for the other embodiments and variants described above, provided that it is technically feasible.

Claims

Demands

1. Method for controlling an electromechanical actuator (16) comprising a polyphase asynchronous motor (24), the method comprising at least the following steps: - determining (102) a setpoint speed (Vc) of the motor (24), by a control device (56); - generating (106) control signals for an inverter (30), by the control device (56); - supplying (108) by the inverter (30) electrical supply currents, according to the control signals, to power the motor (24), the electrical supply currents powering the windings (26) of the motor (24) in order to rotate the motor (24) at a rotational speed (Vm), the inverter (30) being powered by a direct current;and - measurement (110) of the rotational speed (Vm) of the motor (24), by a speed sensor (58), characterized in that a frequency of the control signals (fcmde ) generated is fixed and determined as a function of the setpoint speed (Vc) and in that a duty cycle of the control signals is adapted as a function of the rotational speed (Vm) of the motor (24), measured by the speed sensor (58), so that the rotational speed (Vm) of the motor (24) corresponds to the setpoint speed (Vc).;

2. A control method according to claim 1, wherein the supply electric currents are generated from the control signals by pulse width modulation.

3. A control method according to any one of the preceding claims, wherein the supply electrical currents are pseudo-sinusoidal.

4. A control method according to any one of the preceding claims, comprising a step of recording (100) an optimized characteristic curve (C) of the frequency of the control signals (fcmde) as a function of the setpoint speed (Vc), such that, when the motor (24) rotates at a given setpoint speed (Vc) and when the control signals have a frequency (fcmde) equal to the frequency given by the optimized characteristic curve (C) for this given set speed (Vc), a motor efficiency (24) at the given set speed (Vc) is maximum, and in which the frequency (fcmde) of the generated control signals is determined as a function of the set speed (Vc) from the optimized characteristic curve (C).

5. A control method according to claim 4, wherein the optimized characteristic curve (C) comprises a first point (A) corresponding to a setpoint speed (Vc) of 25Hz and a control signal frequency (fcmde) of 45Hz, and a second point (B) corresponding to a setpoint speed (Vc) of 50Hz and a control signal frequency (fcmde) of 80Hz.

6. Electromechanical actuator (16) comprising a polyphase asynchronous motor (24), comprising several windings (26), an inverter (30), connected to the motor (24), and a control device (56), the electromechanical actuator (16) being configured to implement a method according to any one of the preceding claims.

7. Electromechanical actuator (16) according to claim 6, wherein the inverter (30) comprises several branches (31, 32, 33), each branch (31, 32, 33) comprising several switches (41, 42, 43, 44, 45, 46), a midpoint (51, 52, 53) of each branch (31, 32, 33) being connected to the motor (24).

8. Electromechanical actuator (16) according to claim 7, wherein: - the motor (24) is a two-phase asynchronous motor, comprising two windings (26) connected together by a neutral point (28); - the inverter (30) comprises three branches (31, 32, 33), each branch (31, 32, 33) comprising two switches (41, 42, 43, 44, 45, 46), the midpoint (51, 52, 53) of each branch (31, 32, 33) being located between the two switches (41, 42, 43, 44, 45, 46) of the branch (31, 32, 33); - the midpoints (51, 52) of a first and a second branch (31, 32) among the three branches (31, 32, 33) are respectively connected to one of the windings (26) of the motor (24); and - the midpoint (53) of the third branch (33) is connected to the neutral point (28).

9. A blackout device (10) comprising the electromechanical actuator (16) according to any one of claims 6 to 8 and a blackout screen (12), driven by the electromechanical actuator (16), the blackout screen (12) being configured to be moved when the motor (24) is running.

10. A blackout device (10) according to claim 9, further comprising a capacitive rectifier (22), connected to the inverter (30) and configured to convert alternating electric current into direct electric current to power the inverter (30).

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