Aircraft propulsion assembly

Abstract

The present invention relates to an aircraft propulsion assembly (202) comprising: - an electric propulsion motor (208) which is synchronous and which comprises a rotor (R) and a stator (S); - a propeller (206) rotated by the rotor; - a device (302) for controlling the electric propulsion motor, designed to implement a sensor-free closed-loop vector control for rotating the propeller. The propulsion assembly further comprises: - a position detector (212) which is designed to detect when the propeller is in a predefined angular range (α); - the control device 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 in the angular range.

Description

Description TITLE: AIRCRAFT PROPULSION SYSTEM Technical field of the invention

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

[0002] The prior art documents W0-A1-2024 / 127319, CN-A-109921712, CN-B-115242154 and CN-B-101984554 are known.

[0003] 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 different countries. In particular, an ambitious standard applies to both new types of aircraft and those already 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.

[0004] 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 less energy-intensive and more environmentally friendly aeronautical components and products whose integration and use in civil aviation have moderate environmental impacts, with the aim of improving the energy efficiency of aircraft.

[0005] 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.

[0006] This sustained research and development work focuses on both new generations of aircraft engines and the weight reduction of aircraft, in particular through the materials used and lighter on-board equipment, the development of the use of electric technologies to provide propulsion, and, as essential complements to technological progress, aviation biofuels.

[0007] We know from the prior art an aircraft propulsion system 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.

[0008] The control device is designed to apply stator voltages to the stator windings of the motor, in order to supply stator currents to them.

[0009] The closed-loop control of a system, described for example in the prior art document W0-A1-2024 / 127319, is a control process (or method) that takes into account a response or feedback from that system.

[0010] For example, closed-loop motor rotor speed control, often called speed control, is a control method that uses feedback to maintain a setpoint or desired speed. In other words, when a speed setpoint is issued, the actual speed of the motor rotor is measured or estimated and then compared to the setpoint. If the actual speed differs from the setpoint, the system adjusts the current or voltage applied to the motor to correct the difference.

[0011] When a measurement or estimation of the motor rotor speed is not taken into account in the control process, this is referred to as open-loop control.

[0012] In the remainder of the description of this application, open loop (or closed loop) control means open loop (or closed loop) control of the angular position or speed of the rotor (or propeller).

[0013] In a sensorless control, the propeller is usually accelerated in open loop, then a closed-loop vector control is implemented. To achieve this, it is necessary to know the rotor's angular position 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. Therefore, it is not necessary to use rotor position sensors.

[0014] 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 can be useful for storing the propeller in a small space where the propeller can only fit when it is within the specified angular range. It is therefore necessary to be able to position the propeller within this angular range, which implies rotating the propeller at a low speed.

[0015] With a sensor-based closed-loop vector control system, the sensor can be used to position the propeller, even at low speeds. However, the sensor is usually an electromechanical device that can fail, in which case the vector control system can no longer be implemented, bringing the entire propulsion system to a standstill. Therefore, it is preferable to eliminate the sensor altogether and implement a sensorless closed-loop vector control system.

[0016] However, a sensorless closed-loop vector control cannot be reliably used to rotate the propeller at low speeds, because below a certain speed, the rotor position is difficult to observe at low speeds and when stopped.

[0017] To overcome this problem, there are techniques to make the position of the rotor observable at low speed and when stopped.

[0018] One of these techniques involves injecting high-frequency signals into the stator voltages (or into a rotor voltage if the rotor is wound). This injection induces a response in the stator currents, a response that depends on the rotor's position. Measuring the stator currents then allows the angular position of the rotor relative to the stator to be estimated, thus enabling the continued use of sensorless, closed-loop vector control, even at low speeds.

[0019] However, injecting high-frequency signals into a synchronous motor can present disadvantages.

[0020] First, the induced stator currents can cause significant propeller torque disturbances, especially for a low-salience motor. These torque disturbances can lead to propeller oscillations beyond the desired angular range for stopping the propeller.

[0021] 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.

[0022] 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.

[0023] 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 design two control systems (one for high speed and one for low speed), which is computationally expensive.

[0024] It may therefore be desirable to plan a propulsion system that makes it possible to overcome at least some of the aforementioned problems and constraints.

[0025] 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

[0026] A propulsion assembly is therefore proposed comprising: a synchronous electric propulsion motor comprising 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 further comprises: a position detector, designed to detect when the propeller is within a predefined angular range; and in that the control device is further designed to: implement open-loop control to rotate the propeller; and in response to detection by the position detector that the propeller has entered the angular range, continue to implement open-loop control to maintain the propeller within the angular range.

[0027] Thus, thanks to the invention, it is possible to easily position the propeller with a simple position detector, and without using complex calculations.

[0028] The invention therefore avoids bulking up the propulsion system and also offers cost savings because only existing current sensors are used. Propeller positioning does not require the addition of any new electrical measurements.

[0029] The invention may further include one or more of the following optional features, in any technically feasible combination.

[0030] Preferably, the propeller is rotated, by 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.

[0031] Preferably, the control device is also designed to slow the propeller below a predefined angular velocity, before implementing open-loop control to rotate the propeller.

[0032] Preferably also, the position detector includes 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 within the angular range when both sensors detect the propeller within their angular range.

[0033] Preferably, the propulsion assembly also includes: a DC voltage source; a switching inverter between the DC voltage source and the electric propulsion motor; and a switching inverter control unit.

[0034] Preferably, the control device also includes a memory designed to record stator voltage values ​​of the electric propulsion motor when the propeller enters the angular range.

[0035] Preferably, the control device is also 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.

[0036] Preferably, the propulsion assembly also includes a pylon with a first end carrying the electric propulsion motor.

[0037] An aircraft comprising a propulsion system according to the invention is also proposed.

[0038] Preferably, the aircraft comprises: an external wall having a housing for receiving the pylon and the propeller positioned in the angular interval; and a retractable electric motor designed to move the pylon from an extended position in which the propeller serves to propel the aircraft to a retracted position in the housing.

[0039] 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 sensorless closed-loop vector control to rotate the propeller; an implementation of open-loop control to rotate the propeller; and in response to detection by the position detector that the propeller has entered the angular range, continuing to implement the open-loop control to maintain the propeller in the angular range. Brief description of the figures

[0040] 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: Figure 1 is a three-dimensional view of an aircraft according to the invention; Figure 2 is a three-dimensional view of a longeron of the aircraft of Figure 1, carrying an auxiliary propulsion assembly according to the invention; Figure 3 is a functional view of a control device for an electric motor driving a propeller of the auxiliary propulsion assembly; Figure 4 is a view similar to that of Figure 3, where the control device implements sensorless closed-loop vector control; Figure 5 is a view similar to that of Figure 3, where the control device implements open-loop vector control;Figure 6 is a front view of a device for detecting correct propeller positioning, i.e., propeller positioning within a predefined angular range; Figure 7 is a front view of an alternative embodiment of the detection device of Figure 6; Figure 8 is a block diagram illustrating the steps of a method according to the invention for stopping the propeller; Figure 9 reproduces Figure 8 with the addition of one step; and Figure 10 is a block diagram illustrating the steps of another method according to the invention for stopping the propeller. Detailed description of the invention

[0041] With reference to Figure 1, an example of an aircraft 100 in which the invention is implemented will now be described. Aircraft 100 is, for example, a drone, as in the illustrated example. In other embodiments, aircraft 100 may be, for example, a vertical take-off and landing (VTOL) aircraft.

[0042] 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.

[0043] For example, as in the illustrated example, the aircraft 100 has a main fuselage 104 carrying the main propeller 102 and in which the turbomachine extends.

[0044] 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 the longerons 106 to the main fuselage 104 respectively.

[0045] With reference to Figure 2, the aircraft 100 further comprises at least one auxiliary propulsion unit 202 intended to complement or supplement the main propulsion unit.

[0046] 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.

[0047] The auxiliary propulsion unit 202 comprises a pylon 204 and a propeller 206 mounted on one end of the pylon 204, which may, for example, have 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 may, for example, be located at the first end of the pylon 204, as illustrated in Figure 2.

[0048] 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.

[0049] 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.

[0050] The retraction system 214 further includes a control unit 218 for the electric retraction motor 216, to move the pylon 204 (and consequently the propeller 206) from an extended position, as illustrated for example in Figure 2, in which the propeller 206 is used to propel the aircraft 100, to a position recess in which pylon 204 (and at the same time propeller 206) is stored in housing 212.

[0051] With reference to Figure 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 (P o = 3), or even seven pairs of poles (Po = 7).

[0052] The rotor R is designed to provide a rotor magnetic field in a specific direction. To achieve this, the rotor R can be wound. Alternatively, the 208 electric propulsion motor can be brushless, with a permanent magnet rotor R.

[0053] Although, in the example illustrated in figure 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.

[0054] The rotor R has, relative to the stator S, an angular position denoted 0 and an angular velocity denoted co. Generally, there can 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 the propeller 206.

[0055] The auxiliary propulsion unit 202 also includes a control device 302 for the electric propulsion motor 208.

[0056] In general, the 302 control device is designed to apply stator voltages V A , V B , V c to stator windings (not shown) of stator S, in order to supply them with stator currents l A IB, the. These are periodic at an electrical frequency denoted F, in order to generate a rotating magnetic field that drives the rotor R in rotation. The electrical frequency F is related to the angular velocity co by the formula: co = 60 x F / P o (in revolutions per minute).

[0057] 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 sensorless closed-loop vector control to rotate the propeller 206.

[0058] As is known in itself, vector control involves considering the stator currents l A , IB, the and the stator voltages V A , V B , V cas 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 the quadrature stator currents lq_ in order 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 l. A , IB, the, rather than using a sensor to measure them.

[0059] For example, the control device 302 includes a DC voltage source 304 designed to provide a DC voltage V D c, as well as a 306 switching inverter designed to convert the DC voltage V D c in the stator voltages V A , V B , V c for the stator windings in order to supply the stator currents l A , L B, to the latter. The control device 302 then further comprises a control unit 308 of the switching inverter 306.

[0060] The control device 302 also includes a current sensor 310 designed to measure stator currents l A , L B , the, as well as a position detector 312 designed to detect when the propeller 206 is within a predefined angular range a. The position detector 312 will be described in more detail later, with reference to Figure 6.

[0061] An example of the implementation of the control unit 308 for the implementation of the normal operating mode will now be described.

[0062] The control unit 308 includes a speed controller 314 designed to calculate a quadrature current setpoint l q * based on a difference of The speed AOÜ is determined between a set angular velocity co* and an estimated angular velocity co of the rotor R, such that the estimated angular velocity co follows the set angular velocity co*. The speed controller 310 is, for example, a proportional-integral controller.

[0063] The control unit 308 further includes a torque controller 316 designed to calculate a quadrature voltage setpoint V* q from a current difference Al q between the quadrature current setpoint l q * and a quadrature current measured l q , so that the measured quadrature current lq follows the quadrature current setpoint lq*. The torque controller 316 is, for example, a proportional-integral controller.

[0064] 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, p (V = V* a , V* p ), from an estimate of the rotor angle 0.

[0065] 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 V A , V B , V c conforming to the stator voltage setpoint V = V* a , V*p.

[0066] To estimate the quadrature current lq, the rotor angle and the rotor speed, the control unit 308 also includes the following modules.

[0067] The 308 control unit thus includes a DQZ 322 transform module designed to express the measured stator currents. A , IB, the in the fixed frame dq, to ​​give the measured stator current lq (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.

[0068] The control unit 308 further includes an estimation module 328 designed to estimate the rotor angle and rotor speed from the stator currents l A , IB, the and stator voltages V a , Vp applied. For example, the estimation module 328 uses the average of the stator voltages V a , Vp obtained through the applied duty cycle and the voltage V D c. This estimation can be performed using methods such as back electromotive force estimation, or active flux (from the English "active flux"), 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 electrical.

[0069] 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 l a , lp.

[0070] These modules 314 to 330 used in normal operating mode are illustrated in isolation in figure 4.

[0071] Returning to Figure 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 specifically designed to position the propeller 206 in the angular range a.

[0072] In this positioning mode, the piloting device 302 can first be designed to slow the propeller 206 down to a low speed, or even to a stop of the propeller 206.

[0073] The control device 302 is further designed to implement open-loop control to rotate the propeller 206, and, in response to detection by the position detector 312 that the propeller 206 has entered the angular range a, to continue to implement open-loop control in order to maintain the propeller 206 in the angular range a.

[0074] The control device 302 can thus command the retraction of the auxiliary propulsion unit 202 into the housing 212.

[0075] These different functions of the control device 302 will be described in more detail later with reference to figure 8.

[0076] To implement open-loop control, the control device 302 includes, for example, a stop module 332.

[0077] To slow the propeller 206 down to the speed threshold m in, the stop module 332 is for example designed to provide this comin speed threshold as co* speed setpoint.

[0078] To slow the propeller 206 below the speed threshold m In, the shutdown module is for example designed to disable modules 314 to 330.

[0079] To rotate the propeller 206 at low speed in open loop, the shutdown module 332 is designed, for example, 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 shutdown module 332 is designed to leave the DQZ transform module 322 active (in particular, modules 324 and 326). The shutdown module 332 is then designed to provide stator current commands l* a and l*p.

[0080] The control device 302 then includes current controllers 334, 336 designed to respectively calculate the voltage setpoints V* a and V* p based on current differences between each current setpoint l* a and the* p and the measured currents aand lp. Current controllers 334, 336 are, for example, proportional-integral controllers.

[0081] Modules 332, 334, 336, 320, 322 used in the shutdown mode are illustrated in isolation in Figure 5.

[0082] In some embodiments, the control device 302 may also include a memory 338, accessible by the module 332.

[0083] With reference to Figure 6, an example of an implementation of the position detector 312 will now be described.

[0084] The position detector 312, for example, includes three sensors 602, 604, and 606, each designed to detect when a blade of the propeller 206 is near the sensor in question. Thus, each sensor 602, 604, and 606 has a detection angular range around the sensor in question: the sensor 602, 604, and 606 is designed to provide a detection signal when a blade of the propeller 206 is within this detection angular range, but not when no blade of the propeller 206 is within this detection angular range. In Figure 6, only the detection angular ranges of the first and second sensors 602 and 604 are shown, with the references Peo2 and Peo4.

[0085] The first and second sensors 602, 604 are positioned so that they simultaneously detect a blade of the propeller 206 over the angular interval a. Thus, the angular interval a can be chosen to be very small, even if the first and second sensors 602, 604 are not very precise, that is to say their respective angular detection ranges P6o2, Peo4 are extended.

[0086] If the propeller 206 has only two blades, as in the illustrated example, the first and second sensors 602 and 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 and 604 detects a blade. Thus, when a detection occurs simultaneously with both sensors 602 and 604, it means that the propeller 206 is within the angular interval a.

[0087] 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. 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 and 606 shown in Figure 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 and 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.

[0088] With reference to Figure 7, the first and second sensors 602, 604 could be side by side, with their angular detection ranges P6o2, Peo4 overlapping, this overlap forming the angular interval a.

[0089] With reference to figure 8, a method 800 according to the invention, for stopping the propeller 206 will now be described.

[0090] Initially, the control device 302 is assumed to be in normal operating mode, i.e. that the control device 302 controls the electric propulsion motor 208 by implementing a closed-loop control without sensor, for example as illustrated in Figure 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.

[0091] The 800 shutdown procedure then comprises the following steps.

[0092] During a step 802, the control device 302, for example module 332, receives a stop request RQ.

[0093] In response, during step 804, the control device 302 causes a slowing down of the rotor R.

[0094] 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 down the propeller 206 until this threshold co m by implementing sensorless closed-loop vector control. For example, module 332 provides the threshold co m in as a speed instruction co.

[0095] From the threshold co mIn this case, 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.

[0096] 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.

[0097] During a step 806, the piloting device 302, for example 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 cüf, for example 1,000 revolutions per minute or less, preferably 550 revolutions per minute or less, preferably again 500 revolutions per minute or less.

[0098] During step 808, the control device 302 implements open-loop control to rotate the propeller at a speed lower than, for example, 2,000 rpm, preferably lower than 1,700 rpm, and even more preferably lower than 100 rpm. For example, the propeller 206 is rotated at a constant speed, for example, 85 rpm. To achieve this, the module 332 provides, for example, stator current commands l* a , l*p, which are compared to the measured stator currents l a, lp, and the comparisons are provided to 334, 336 to obtain the stator voltage V* instructions a , V*p, as illustrated for example in figure 5.

[0099] 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.

[0100] In response to the detection of the correct positioning of the propeller 206, during a step 812, the piloting device 312 continues to implement the open-loop control but now to maintain the propeller 206 within the angular range a.

[0101] To achieve this, the control device 302, for example, controls the electric propulsion motor 208 in order to stabilize the rotating magnetic field. For example, module 332 maintains the stator currents l a , lp to their value when detecting the correct positioning of propeller 206.

[0102] While the propeller 206 is held in the angular interval a, during a step 814, the piloting device 302, for example module 332, commands the electric retraction motor 216 to retract the propulsion assembly 202 into the housing 212.

[0103] With reference to Figure 9 and Figure 10, a variant of the invention will now be described. This variant aims to maintain the ability to stop the propeller 206 even in the event of a failure of one of the sensors 602, 604.

[0104] With reference to Figure 9, the process 800 is modified to add a step 902 during which the control device, for example module 332, records in memory 338 the values ​​of the stator voltages V, expressed for example in the ABC frame, when the correct positioning of the propeller 206 is detected.

[0105] With reference to Figure 10, in the event of failure of one of the sensors 602, 604, the following process 1000 can then be implemented.

[0106] The steps common to process 800 in Figure 8 are not described again.

[0107] Following step 808, during a step 1002, the still valid sensor 602 detects that propeller 206 enters its angular detection range P6o2.

[0108] In response, during step 1004, the piloting device 302, module 332, continues to rotate the propeller 206 in an open loop, until the stator voltages V reach the values ​​previously recorded in memory 338.

[0109] 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.

[0110] The invention therefore avoids bulking up the propulsion system and also offers cost savings because only existing current sensors are used. Rotor positioning does not require the addition of new electrical measurements.

[0111] It is also not necessary to accurately estimate the position at rest and at low speed to position the rotor. Thus, the rotor positioning process is simplified.

[0112] It should also be noted that the invention is not limited to the embodiments described above. Indeed, it will 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.

[0113] For example, in some embodiments, the detection device 312 could include only a single sensor to detect the correct positioning of the propeller 206. In this case, the stator voltage values ​​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, the method 1000 of Figure 10 is used for each stop of the propeller 206. This allows the use of a less precise sensor, i.e., one with a large detection range, while still enabling the propeller 206 to be stopped within the angular interval a.

[0114] 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 operate in a propeller positioning mode: by implementing 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 open-loop control, at an angular velocity 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 (Peo2, Peo4) for detecting the propeller (206), the two sensors (602, 604) being positioned such that the propeller (206) is detected in the angular interval (a) when both sensors (602, 604) detect the propeller (206) in their angular range (Peo2, Peo4). [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 (P6o2, Peo4) 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 controlling 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 range (a), continuing to implement the open-loop control to maintain the propeller (206) in the angular range (a).

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