AIRCRAFT PROPULSION ASSEMBLY

Abstract

The present invention relates to an aircraft propulsion assembly (202) comprising: - a synchronous electric propulsion motor (208) comprising a rotor (R) and a stator (S); - a propeller (206) driven in rotation by the rotor; - a control device (302) for the electric propulsion motor, designed to implement sensorless closed-loop vector control to rotate the propeller. The propulsion assembly further comprises: - a position sensor (212), designed to detect when the propeller is within a predefined angular range (α); - the control device is further designed to: implement open-loop control to rotate the propeller; and, in response to detection by the position sensor that the propeller has entered the angular range, continue to implement open-loop control to maintain the propeller within the angular range. Figure 3 (for the abstract)

Description

Title of the invention: AIRCRAFT PROPULSION ASSEMBLY Technical field of the invention

[0001] The present invention relates to an aircraft propulsion assembly, an aircraft comprising such a propulsion assembly and a method for positioning a rotor of the propulsion assembly. Technological background

[0002] Climate change is a major concern for many legislative and regulatory bodies worldwide. Indeed, various restrictions on carbon emissions have been, are being, or will be adopted by various states. In particular, an ambitious standard applies to both new types of aircraft and those currently in operation, requiring the implementation of technological solutions to bring them into compliance with current regulations. Civil aviation has been actively working for several years now to contribute to the fight against climate change.

[0003] Technological research efforts have already led to very significant improvements in the environmental performance of aircraft. The Applicant takes into account the factors impacting all phases of design and development in order to obtain aeronautical components and products that are less energy-intensive, more environmentally friendly, and whose integration and use in civil aviation have moderate environmental impacts, with the aim of improving the energy efficiency of aircraft.

[0004] Consequently, the Applicant is constantly working to reduce its climate impact by using methods and operating virtuous development and manufacturing processes that minimize greenhouse gas emissions to the minimum possible in order to reduce the environmental footprint of its activity.

[0005] This sustained research and development work focuses on new generations of aircraft engines, the weight reduction of aircraft, in particular through the materials used and lighter on-board equipment, the development of the use of electrical technologies to provide propulsion, and, as essential complements to technological progress, aviation biofuels.

[0006] Prior art is known an aircraft propulsion assembly comprising: - an electric propulsion motor which is synchronous and which includes a rotor and a stator; - a propeller driven in rotation by the rotor; - a control device for the electric propulsion motor, designed to implement closed-loop vector control without sensors to rotate the propeller.

[0007] The control device is designed to apply stator voltages to stator windings of the motor, in order to supply stator currents to the latter.

[0008] In sensorless control, the propeller is generally accelerated in open loop, and then closed-loop vector control is implemented. For this, it is necessary to know the angular position of the rotor at all times. The rotor's rotational speed is deduced from its angular position, which is itself determined from measurements of the stator currents and / or voltages. Thus, it is not necessary to provide rotor position sensors.

[0009] Furthermore, it may be desirable to stop the propeller, and therefore the rotor, at a predefined angular position, or more generally within a predefined angular range. For example, this may be useful for storing the propeller in a small space into which the propeller can only fit when it is within the angular range. It is therefore necessary to be able to position the propeller within this angular range, which implies rotating the propeller at low speed.

[0010] With a closed-loop vector control system using a sensor, the sensor can be used to position the propeller, even at low speeds. However, the sensor is generally an electromechanical device that can fail, in which case the vector control system can no longer be implemented, and the entire propulsion system comes to a standstill. Therefore, it is preferable to do without a sensor and implement a sensorless closed-loop vector control system.

[0011] However, a sensorless closed-loop vector control cannot be reliably used to rotate the propeller at low speed, because below a certain speed, the position of the rotor is difficult to observe at low speed and when stopped.

[0012] To overcome this problem, there are techniques to make the position of the rotor observable at low speed and when stopped.

[0013] One of these techniques involves injecting high-frequency signals into the stator voltages (or into a rotor voltage if the rotor is wound). Such an injection induces a response in the stator currents, this response depending on the rotor's position. Measuring the stator currents then makes it possible to estimate the angular position of the rotor relative to the stator, and thus to continue using sensorless closed-loop vector control, even at low speeds.

[0014] However, injecting high-frequency signals into a synchronous motor can present disadvantages.

[0015] First, the induced stator currents can cause significant disturbances in propeller torque, especially for a low-salience motor. These torque disturbances can cause propeller oscillations beyond the angular range within which the propeller is to be stopped.

[0016] In addition, the injection of high-frequency signals can also induce an uncertainty of 180° on the angular position of the rotor, requiring the application of specific procedures to reduce or eliminate this uncertainty.

[0017] Finally, the injection of high-frequency signals requires a computationally expensive signal processing algorithm to estimate the angular position of the rotor from the measured stator currents.

[0018] A second technique, usable when the synchronous electric motor has smooth poles or low saliency, consists of using a sensorless closed-loop control specifically adapted to low speeds and allowing the rotor position to be observed. However, such a control adapted to low speeds differs from that used at high speeds, so it is necessary to provide two control systems (high-speed and low-speed), which is computationally expensive.

[0019] It may therefore be desirable to provide a propulsion system which makes it possible to overcome at least some of the aforementioned problems and constraints.

[0020] To this end, the invention is the result of technological research aimed at significantly improving aircraft performance and, in this sense, contributes to reducing the environmental impact of aircraft. Summary of the invention

[0021] A propulsion system comprising: is therefore proposed. - an electric propulsion motor which is synchronous and which comprises a rotor and a stator; - a propeller driven in rotation by the rotor; - a control device for the electric propulsion motor, designed to implement sensorless closed-loop vector control to rotate the propeller; characterized in that it also comprises: - a position detector, designed to detect when the propeller is within a predefined angular range; and in that the control system is further designed to: - implement an open-loop control to rotate the propeller; and - in response to a detection by the position detector that the propeller has entered the angular range, continue to implement the open-loop control to maintain the propeller within the angular range.

[0022] Thus, thanks to the invention, it is possible to easily position the propeller with a simple position detector, and without using complex calculations.

[0023] The invention therefore avoids bulking up the propulsion system and also provides cost savings because only existing current sensors are used. Propeller positioning does not require the addition of new electrical measurements.

[0024] The invention may further include one or more of the following optional features, according to any technically possible combination.

[0025] Preferably, the propeller is rotated, by the open-loop control, at an angular speed of less than 2,000 revolutions per minute, preferably less than 1,700 revolutions per minute, and preferably even less than 100 revolutions per minute.

[0026] Preferably also, the control device is designed to slow the propeller below a predefined angular speed, before implementing the open-loop control to rotate the propeller.

[0027] Preferably also, the position detector comprises a first sensor and a second sensor, each with an angular range for detecting the propeller, the two sensors being positioned so that the propeller is detected in the angular range when both sensors detect the propeller in their angular range.

[0028] Preferably, the propulsion assembly also includes: - a direct current voltage source; - a switching inverter between the DC voltage source and the electric propulsion motor; and - a switching inverter control unit.

[0029] Preferably also, the control device further includes a memory designed to record stator voltage values ​​of the electric propulsion motor when the propeller enters the angular range.

[0030] Preferably also, the control device is further designed to, in response to a detection by a sensor of the detection device that the propeller enters an angular detection range of that sensor, continue to rotate the propeller in open loop, until the stator voltages reach the values ​​previously recorded in memory.

[0031] Preferably also, the propulsion assembly further comprises a pylon having a first end carrying the electric propulsion motor.

[0032] An aircraft comprising a propulsion assembly according to the invention is also proposed.

[0033] Preferably, the aircraft comprises: - an external wall with a housing for receiving the pylon and the helix positioned within the angular interval; and - an electric retraction motor designed to move the pylon from an extended position in which the propeller is used to propel the aircraft to a retracted position in the housing.

[0034] A method for controlling an aircraft electric propulsion motor is also proposed, this electric propulsion motor being synchronous and comprising a rotor and a stator, the rotor driving a propeller, comprising the following steps: - an implementation of a sensorless closed-loop vector control to rotate the propeller; - an implementation of an open-loop control to rotate the propeller; and - in response to a detection by the position detector that the propeller has entered the angular range, continue to implement the open-loop control to maintain the propeller within the angular range. Brief description of the figures

[0035] The invention will be better understood with the aid of the following description, given solely by way of example and made with reference to the accompanying drawings in which: - [Fig.1] is a three-dimensional view of an aircraft according to the invention; - [Fig. 2] is a three-dimensional view of a longeron of the aircraft [Fig.1], carrying an auxiliary propulsion assembly according to the invention; - [Fig.3] is a functional view of a control device for an electric motor driving a propeller of the auxiliary propulsion assembly; - [Fig.4] is a view similar to that of [Fig.3], when the control device implements sensorless closed-loop vector control; - [Fig.5] is a view similar to that of [Fig.3], when the control device implements open-loop vector control; - [Fig.6] is a front view of a device for detecting proper propeller positioning, i.e., propeller positioning within a predefined angular range; - [Fig.7] is a front view of a variant embodiment of the detection device of [Fig.6]; - [Fig.8] is a block diagram illustrating the steps of a method according to the invention for stopping the propeller; - Figure 9 repeats Figure 8, adding one step; and - the [Fig. 10] is a block diagram illustrating the steps of another method according to the invention for stopping the propeller. Detailed description of the invention

[0036] With reference to [Fig. 1], an example of an aircraft 100 in which the invention is implemented will now be described. The aircraft 100 is, for example, a drone, as in the illustrated example. In other embodiments, the aircraft 100 may be, for example, a vertical take-off and landing (VTOL) aircraft.

[0037] The aircraft 100 includes, for example, a main propulsion unit comprising a main propeller 102 and a turbomachine (not shown) for driving the main propeller 102.

[0038] For example, as in the illustrated example, the aircraft 100 comprises a main fuselage 104 carrying the main propeller 102 and in which the turbomachine extends.

[0039] Also for example, as in the illustrated example, the aircraft 100 has two longerons 106 located on either side of the main fuselage 104, as well as wings 108 connecting respectively the longerons 106 to the main fuselage 104.

[0040] With reference to [Fig.2], the aircraft 100 further comprises at least one auxiliary propulsion unit 202 intended to complement or supplement the main propulsion unit.

[0041] For example, as in the illustrated example, two auxiliary propulsion assemblies 202 are provided, respectively carried by the longerons 106. Subsequently only one of the auxiliary propulsion assemblies 202 will be described, the other being similar.

[0042] The auxiliary propulsion unit 202 comprises a pylon 204 and a propeller 206 carried by a first end of the pylon 204, having, for example, two blades. The auxiliary propulsion unit 202 further comprises an electric propulsion motor 208, designed to drive the propeller 206. The electric propulsion motor 208 can, for example, be arranged at the first end of the pylon 204, as illustrated in [Fig. 2].

[0043] Furthermore, each longeron 106 has an external wall 210 equipped with a housing 212 into which the auxiliary propulsion unit 202 is retractable. For this purpose, the aircraft 100 includes, for each auxiliary propulsion unit 202, a retraction system 214 in the housing 206, for example provided in the longeron 106.

[0044] The retraction system 214 includes an electric retraction motor 216 connected to a second end of the pylon 204 in order to rotate the latter.

[0045] The retraction system 214 further includes a control unit 218 of the electric retraction motor 216, for moving the pylon 204 (and at the same time the propeller 206) from an extended position, as illustrated for example in [Fig.2], in which the propeller 206 is used to propel the aircraft 100, to a retracted position in which the pylon 204 (and at the same time the propeller 206) is stored in the housing 212.

[0046] With reference to [Fig. 3], the electric propulsion motor 208 is synchronous and equipped with a rotor R for driving the propeller 206 and a stator S having stator windings (not shown). For example, the stator S comprises a number Po of pole pairs, for example three pole pairs (Po = 3), or even seven pole pairs (Po = 7).

[0047] The rotor R is designed to provide a rotor magnetic field in a certain direction. For this purpose, the rotor R can be wound. Alternatively, the electric propulsion motor 208 can be brushless, with the rotor R being a permanent magnet.

[0048] Although, in the example illustrated in [Fig.3], the stator S surrounds the rotor R, the invention can also be applied in the case where the rotor R surrounds the stator S.

[0049] The rotor R has, relative to the stator S, an angular position denoted 0 and an angular velocity denoted co. Generally, there may be a gear ratio between the rotation of the rotor R and the rotation of the propeller 206 (as in the case of a gear between the two). However, in the example described, it will be assumed that this ratio is equal to one, so that the angular position 0 and the angular velocity co will apply equally to the rotor R and to the propeller 206.

[0050] The auxiliary propulsion assembly 202 further includes a control device 302 for the electric propulsion motor 208.

[0051] In general, the control device 302 is designed to apply stator voltages VA, VB, Vc to stator windings (not shown) of the stator S, in order to supply them with stator currents IA, IB, le- These are periodic at an electrical frequency denoted F, in order to generate a rotating magnetic field driving the rotor R in rotation. The electrical frequency F is related to the angular speed co by the formula: co = 60 x F / Po (in revolutions per minute).

[0052] The control device 302 is designed to operate in a first operating mode, called the normal operating mode, in which the control device 302 implements a sensorless closed-loop vector control to rotate the propeller 206.

[0053] As is known in itself, vector control consists of considering the stator currents IA, IB, Ic and the stator voltages VA, VB, Vc as Vectors, hereafter denoted respectively I and V. These vectors I and V can be expressed in different coordinate systems. In particular, it is common to use a dq coordinate system attached to the rotor R, comprising a direct component, denoted respectively Id and Vd, in the direction of the rotor magnetic field, and a quadrature component, denoted respectively Iq and Vq, perpendicular to the direct components Id and Vd. The direct stator current Id allows for the weakening of the rotor magnetic field, and the quadrature current Iq defines a torque applied to the rotor R. In the example described below, it will be assumed that no field weakening is used, so that the direct stator current Id is zero, as is the direct stator voltage Vd. Thus, only the quadrature current Iq will be described hereafter. Nevertheless, a person skilled in the art can easily adapt the described example to the case of a non-zero direct current Id.Furthermore, closed-loop vector control involves estimating or measuring the direct stator currents Id and quadrature stator currents Iq to control them according to respective setpoints. Finally, sensorless closed-loop vector control involves estimating the rotor angle 0 and the angular velocity co from the rotor currents IA, IB, Ic, rather than using a sensor to measure them.

[0054] For example, the control device 302 includes a DC voltage source 304 designed to supply a DC voltage VDc, and a switching inverter 306 designed to convert the DC voltage VDC into stator voltages VA, VB, Vc for the stator windings in order to supply the stator currents IA, IB, Ic to them. The control device 302 further includes a control unit 308 for the switching inverter 306.

[0055] The control device 302 further includes a current sensor 310 designed to measure the stator currents IA, IB, Ic, and a position detector 312 designed to detect when the propeller 206 is within a predefined angular range α. The position detector 312 will be described in more detail later, with reference to [Fig. 6].

[0056] An example of an embodiment of the control unit 308 for the implementation of the normal operating mode will now be described.

[0057] The control unit 308 includes a speed controller 314 designed to calculate a quadrature current setpoint Iq* from a speed difference Aco between an angular velocity setpoint œ* and an estimated angular velocity co of the rotor R, such that the estimated angular velocity co follows the angular velocity setpoint œ*. The speed controller 310 is, for example, a proportional-integral controller.

[0058] The control unit 308 further includes a torque controller 316 designed to calculate a quadrature voltage setpoint V*q from a current difference AIq between the quadrature current setpoint Iq* and a measured quadrature current Iq, so that the measured quadrature current Iq follows the quadrature current setpoint Iq*. The torque controller 316 is, for example, a proportional-integral controller.

[0059] The control unit 308 further includes an inverse Clarke transform module 318 designed to express the stator voltage setpoint V (the quadrature voltage setpoint V*q in the example described) in the fixed frame a, [3 (V = V*a, V*p), from an estimate of the rotor angle 0.

[0060] The control unit 308 further includes a control module 320 designed to calculate CMD commands, for example in the form of pulse width modulation, according to a certain duty cycle, so that the inverter 306 provides stator voltages VA, VB, Vc in accordance with the stator voltage setpoint V = V*a, V*p.

[0061] To estimate the quadrature current Iq, the rotor angle and the rotor speed, the control unit 308 further comprises the following modules.

[0062] The control unit 308 thus includes a DQZ transform module 322 designed to express the measured stator currents IA, IB, and I in the fixed dq reference frame, to give the measured stator current Iq (the forward stator current Id is zero). For example, as in the illustrated example, the transform module 322 comprises a Clarke transform module 324 followed by a Park transform module 326.

[0063] The control unit 308 further includes an estimation module 328 designed to estimate the rotor angle and rotor speed from the applied stator currents IA, IB, and stator voltages Va and Vp. For example, the estimation module 328 uses the average of the stator voltages Va and Vp obtained through the applied duty cycle and the voltage VDC. This estimation can be performed via methods such as back electromotive force estimation, or active flux estimation, or more complex iterative methods such as a Kalman filter. These methods work for electrical speeds above a common speed threshold, generally, for example, around 200 Hz.

[0064] For example, as in the illustrated example, the estimation module 328 comprises the Clarke transform module 324 followed by an estimation module 330 designed to estimate the rotor angle and rotor speed from the stator currents Ia, Ip.

[0065] These modules 314 to 330 used in normal operating mode are illustrated in isolation on [Fig.4].

[0066] Returning to [Fig.3], the piloting device 302 is further designed to operate in a second operating mode, called positioning mode, in which the piloting device 302 is in particular designed to position the propeller 206 in the angular range a.

[0067] In this positioning mode, the piloting device 302 can first be designed to slow down the propeller 206 to a low speed, or even to the stop of the propeller 206.

[0068] The control device 302 is further designed to implement an open-loop control to rotate the propeller 206, and, in response to a detection by the position detector 312 that the propeller 206 has entered the angular interval a, to continue to implement the open-loop control in order to maintain the propeller 206 in the angular interval a.

[0069] The control device 302 can thus control the retraction of the auxiliary propulsion assembly 202 into the housing 212.

[0070] These different functions of the control device 302 will be described in more detail later with reference to [Fig.8].

[0071] To implement open-loop control, the control device 302 includes, for example, a stop module 332.

[0072] To slow down the propeller 206 to the comin speed threshold, the stop module 332 is for example designed to provide this comin speed threshold as the speed setpoint œ*.

[0073] To slow the propeller 206 below the comin speed threshold, the stop module is for example designed to deactivate modules 314 to 330.

[0074] To rotate the propeller 206 at low speed in open loop, the stop module 332 is, for example, designed to deactivate the speed controller 314, the torque controller 316, and the inverse Clarke transform module, as well as the estimation module 328 (in particular the estimation module 330). Conversely, the stop module 332 is designed to leave the DQZ transform module 322 active (in particular modules 324 and 326). The stop module 332 is then designed to provide stator current setpoints I*a and I*p.

[0075] The control device 302 then includes current controllers 334, 336 designed to calculate the voltage setpoints V*a and V*p respectively from the current differences between each current setpoint I*a and I*p and the measured currents L and Ip. The current controllers 334, 336 are, for example, proportional-integral controllers.

[0076] Modules 332, 334, 336, 320, 322 used in the shutdown mode are illustrated in isolation on [Fig. 5].

[0077] In some embodiments, the control device 302 may also include a memory 338, accessible by the module 332.

[0078] With reference to [Fig.6], an example of an embodiment of the position detector 312 will now be described.

[0079] The position detector 312 comprises, for example, three sensors 602, 604, 606, each designed to detect when a blade of the propeller 206 is near the sensor 602, 604, 606 in question. Thus, each sensor 602, 604, 606 has an angular detection range around the sensor 602, 604, 606 in question: the sensor 602, 604, 606 is designed to provide a detection signal when a blade of the propeller 206 is within this angular detection range, but not when no blade of the propeller 206 is within this angular detection range. In [Fig. 6], only the angular detection ranges of the first and second sensors 602, 604 are shown, with the reference numerals P6 02, Pe cm-

[0080] The first and second sensors 602, 604 are positioned so that they detect a blade of the propeller 206 at the same time as over the angular interval a. Thus, the angular interval a can be chosen very small, even if the first and second sensors 602, 604 are not very precise, that is to say that their respective angular detection ranges P6 02, Pe 04 are extended.

[0081] If the propeller 206 has only two blades, as in the illustrated example, the first and second sensors 602, 604 can be located 180° ± a apart. In this case, when the propeller 206 is positioned within the angular interval a, the first sensor 602 detects a blade. Conversely, when the propeller 206 is outside the angular interval a, either none or only one of the first and second sensors 602, 604 detects a blade. Thus, when a detection occurs simultaneously with both sensors 602, 604, it means that the propeller 206 is within the angular interval a.

[0082] The detection system 312 can also enable the control device 308, for example module 332, to roughly determine the speed of the propeller 206. To do this, it simply needs to determine the time between two successive detections by two sensors, respectively. For example, the third sensor 706 can be used for this purpose. Thus, considering the direction of rotation and the positions of the second and third sensors 604, 606 shown in [Fig. 6], module 332 can be designed to determine the time between the detection by the third sensor 606 and the detection by the second sensor 604, and to deduce the speed of the propeller 206 by dividing the angle between sensors 604, 606 by the determined time. In other embodiments, the same sensors could be used to detect the positioning of the propeller 206 within the angular interval α and to measure the speed of the propeller 206.

[0083] With reference to [Fig.7], the first and second sensors 602, 604 could be side by side, with their angular detection ranges P6 02, Pe 04 overlapping, this overlap forming the angular interval a.

[0084] With reference to [Fig.8], a method 800 according to the invention, for stopping the propeller 206 will now be described.

[0085] Initially, the control device 302 is assumed to be in normal operating mode, i.e., the control device 302 controls the electric propulsion motor 208 by implementing sensorless closed-loop control, for example as illustrated in [Fig. 4]. This normal operating mode corresponds, for example, to a flight phase where the propulsion assembly 202 is in the extended position, i.e., outside the housing 212, to propel the aircraft 100.

[0086] The stopping method 800 then comprises the following steps.

[0087] During a step 802, the control device 302, for example module 332, receives a stop request RQ.

[0088] In response, during a step 804, the control device 302 causes a slowing down of the rotor R.

[0089] To achieve this, if the speed co is greater than the closed-loop operating threshold comin, the control device 302 begins, for example, by slowing the propeller 206 down to this threshold comin by implementing sensorless closed-loop vector control. For example, module 332 provides the threshold comin as the speed co setpoint.

[0090] Once the comin threshold is reached, the control device 302 causes the rotor R to slow down. For example, the control device 302 stops energizing the electric propulsion motor 208 so that the propeller 206 freewheels and slows down due to friction. Alternatively, the control device 302 could operate the electric propulsion motor 208 as a generator, so as to extract kinetic energy from the propeller 206, for example, to charge the DC voltage source 304. Thus, the propeller 206 would be slowed down more quickly than by friction alone.

[0091] Alternatively, the propeller 206 could be slowed down all along by friction and / or by operation of the electric propulsion motor 208 as a generator.

[0092] During a step 806, the piloting device 302, for example the module 332, detects that the angular velocity co of the propeller 206, measured for example by the detection device 312 as explained above, falls below a level cof, for example of 1,000 revolutions per minute or less, preferably 550 revolutions per minute or less, preferably again 500 revolutions per minute or less.

[0093] During a step 808, the control device 302 implements an open-loop control to rotate the propeller, at a speed lower, for example, than 2,000 revolutions per minute, preferably lower than 1,700 revolutions per minute, and even more preferably lower than 100 revolutions per minute. For example, the propeller 206 is rotated at a constant speed, for example, 85 revolutions per minute. For this purpose, the module 332 provides, for example, stator current setpoints I*a, I*p, which are compared to the measured stator currents L, Ip, and the comparisons are provided to the 334, 336 to obtain the stator voltage setpoints V*a, V*p, as illustrated, for example, in [Fig. 5].

[0094] During a step 810, the detection device 312 detects a good positioning of the propeller 206, that is to say that the propeller 206 enters the angular interval a.

[0095] In response to the detection of the correct positioning of the propeller 206, during a step 812, the control device 312 continues to implement the open-loop control but now to maintain the propeller 206 within the angular range a.

[0096] To this end, the control device 302, for example, controls the electric propulsion motor 208 in such a way as to fix the rotating magnetic field. For example, the module 332 maintains the stator currents L, Ip at their value when the correct positioning of the propeller 206 is detected.

[0097] While the propeller 206 is held in the angular interval a, during a step 814, the piloting device 302, for example the module 332, commands the electric retraction motor 216 to retract the propulsion assembly 202 into the housing 212.

[0098] With reference to [Fig. 9] and [Fig. 10], a variant of the invention will now be described. This variant aims to continue to be able to stop the propeller 206 even in the event of a failure of one of the sensors 602, 604.

[0099] With reference to [Fig.9], the process 800 is modified to add a step 902 during which the control device, for example the module 332, records in memory 338, the values ​​of the stator voltages V, expressed for example in the reference ABC, when the correct positioning of the propeller 206 is detected.

[0100] With reference to [Fig. 10], in the event of failure of one of the sensors 602, 604, the following method 1000 can then be implemented.

[0101] The steps common to process 800 of [Fig.8] are not described again.

[0102] Following step 808, during a step 1002, the still valid sensor 602 detects that the propeller 206 enters its angular detection range P602.

[0103] In response, during a step 1004, the control device 302, the module 332, continues to rotate the propeller 206 in open loop, until the stator voltages V reach the values ​​previously recorded in memory 338.

[0104] In conclusion, it is clear that the invention makes it possible to do without precise position sensors to position the rotor relative to the stator within a predefined angular range.

[0105] The invention therefore avoids bulking up the propulsion assembly and also provides cost savings because only existing current sensors are used. Rotor positioning does not require the addition of new electrical measurements.

[0106] It is also not necessary to make a precise estimation of the position at rest and at low speed to proceed with rotor positioning. Thus, the rotor positioning process is simplified.

[0107] It should also be noted that the invention is not limited to the embodiments described above. It will indeed be apparent to those skilled in the art that various modifications can be made to the embodiments described above, in light of the information just disclosed to them.

[0108] For example, in some embodiments, the detection device 312 could include only one sensor to detect the correct positioning of the propeller 206. In this case, the values ​​of the stator voltages V when the propeller 206 enters the angular interval could be measured and recorded beforehand in the memory 338, for example on a test bench. Thus, method 1000 of [Fig. 10] is used for each stop of the propeller 206. This makes it possible to use a less precise sensor, i.e., one with a large detection range, while still allowing the propeller 206 to be stopped within the angular interval a.

[0109] In the detailed presentation of the invention given above, the terms used shall not be interpreted as limiting the invention to the embodiments set forth in this description, but shall be interpreted as including all equivalents which can be foreseen by a person skilled in the art by applying their general knowledge to the implementation of the teaching which has just been disclosed to them.

Claims

Demands

1. Aircraft propulsion assembly (202) comprising: - an electric propulsion motor (208) which is synchronous and which has a rotor (R) and a stator (S); - a propeller (206) driven in rotation by the rotor (R); - a control device (302) for the electric propulsion motor (208), designed to implement sensorless closed-loop vector control to rotate the propeller (206); characterized in that it further comprises: - a position detector (212), designed to detect when the propeller (206) is within a predefined angular range (a); and in that the control device (302) is further designed to: - implement open-loop control to rotate the propeller (206);and - in response to a detection by the position detector (212) that the propeller (206) has entered the angular interval (a), continue to implement the open-loop control to maintain the propeller (206) in the angular interval (a).;

2. Propulsion assembly (202) according to claim 1, wherein the propeller (206) is rotated, by the open-loop control, at an angular velocity of less than 2,000 revolutions per minute, preferably less than 1,700 revolutions per minute, preferably even less than 100 revolutions per minute.

3. Propulsion assembly (202) according to claim 1, wherein the piloting device (302) is designed to slow the propeller (206) below a predefined angular velocity, before implementing open-loop control to rotate the propeller (206).

4. Propulsion assembly (202) according to any one of claims 1 to 3, wherein the position detector (312) comprises a first sensor (602) and a second sensor (604) each with an angular range (P602, Pau) for detecting the propeller (206), the two sensors (602, 604) being positioned so that the propeller (206) is detected in the angular interval (a) when both sensors (602, 604) detect the propeller (206) within their angular range (P602, Pôm)-

5. Propulsion assembly (202) according to any one of claims 1 to 4, further comprising: - a DC voltage source (304); - a switching inverter (306) between the DC voltage source (304) and the electric propulsion motor (208); and - a control unit (308) for the switching inverter (306).

6. Propulsion assembly (202) according to any one of claims 1 to 5, wherein the piloting device (308) further comprises a memory (338) designed to record stator voltage values ​​of the electric propulsion motor (208) when the propeller (206) enters the angular range (a).

7. Propulsion assembly (202) according to claim 6, wherein the piloting device (308) is further designed to, in response to a detection by a sensor (602, 604) of the detection device (312) that the propeller (206) enters an angular detection range (P602, P604) of this sensor (602, 604), continue to rotate the propeller (206) in open loop, until the stator voltages reach the values ​​previously recorded in the memory (338).

8. Propulsion assembly (202) according to any one of claims 1 to 7, further comprising a pylon (204) having a first end carrying the electric propulsion motor (208).

9. Aircraft (100) comprising a propulsion unit (202) according to any one of claims 1 to 8.

10. Aircraft (100) according to claim 9, comprising a propulsion assembly (202) according to claim 8, comprising: - an outer wall (210) having a housing (212) for receiving the pylon (204) and the propeller (206) positioned in the angular interval (a); and - a retractable electric motor (216) designed to move the pylon (114) from an extended position in which the propeller (206) serves to propel the aircraft (100) to a retracted position in the housing (212).

11. Method (800) of driving an aircraft electric propulsion motor (208), this electric propulsion motor (208) being synchronous and comprising a rotor (R) and a stator (S), the rotor (R) driving a propeller (206), comprising the following steps: - an implementation of a sensorless closed-loop vector control to rotate the propeller (206); - an implementation of an open-loop control to rotate the propeller (206); and - in response to a detection by the position detector (212) that the propeller (206) has entered the angular interval (a), continue to implement the open-loop control to maintain the propeller (206) in the angular interval (a).

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