RELATED APPLICATION/S

This application claims the benefit of priority of U.S. Provisional Patent Application No. 62/853,252 filed on May 28, 2019 and claims the benefit of priority of U.S. Provisional Patent Application No. 62/860,828 filed on June 13, 2019, the contents of both of which are incorporated herein by reference in their entirety.

FIELD AND BACKGROUND OF THE INVENTION

The present invention, in some embodiments thereof, relates to a system and method to control thrust and, more particularly, but not exclusively, to a control system for a propelled thrust producer in an airborne vehicle that is fully electrically propelled.

Electric propulsion engines for an airborne vehicle differ from reciprocating and turboprop engines. Reciprocating engines are known to have a relatively narrow power band at medium-high motor speeds. Turboprop engines are known to have a relatively narrow fuel efficiency band, e.g. low thrust specific fuel consumption (TSFC) close to the maximal power limit. In comparison, electric propulsion engines are known to be both torque capable and fuel efficient throughout a wide band of motor speeds that may span the entire operation range of an airborne vehicle. Another advantage of electric propulsion engines is reduced noise pollution as compared to reciprocating and turboprop engines.

SUMMARY OF THE INVENTION

According to an aspect of some embodiments of the present invention there is provided a system and method to control an electrically propelled thrust producer. Optionally and preferably, the system and method is configured to coordinate operation of a plurality of electrically propelled thrust producers included in an electrically propelled vehicle, such as airborne vehicle, hovercraft, and other marine/land vehicles. According to some example embodiments, the electrically propelled thrust producer includes a motor that is configured to drive a variable pitch propeller. According to some example embodiments, based on the constant torque and efficiency characteristics of electric propulsion, optimization of parameters of the propulsion, e.g. performance, noise and power, while enabling easy control over thrust to the vehicle operator is achieved. According to some example embodiments, the propulsion system health, enabling preventive maintenance is monitored based on the system and method as described herein. According to an aspect of some example embodiments there is provided a system for controlling at least one thrust producer that includes an electrical motor and a variable pitch propeller powered by the electrical motor, wherein the at least one thrust producer is included in a vehicle, the system comprising:

a controller configured provide control signals to control motor throttle and pitch angle of a thrust producer based on a momentary thrust of the thrust producer, a momentary pitch angle of the variable pitch propeller and a requested thrust, wherein the requested thrust is based on input from at least one of human operator of the vehicle and an avionic system of the vehicle.

Optionally, the controller is configured to match the momentary thrust to the requested thrust based on adjusting at least one of the motor throttle and pitch angle over a plurality of cycles in which the momentary thrust and the momentary pitch is determined.

Optionally, the momentary thrust is measured by a pressure gauge sensing a momentary pressure developing between the thrust producer and the vehicle.

Optionally, the controller is configured to monitor a momentary required power signal to reach the requested thrust and to adjust motor throttle based on difference between currently measured momentary required power signal and a previously measured momentary required power signal.

Optionally, the controller is configured to limit adjustment of the motor throttle to a defined range, wherein the defined range is determined based on input from the avionic system.

Optionally, the controller is configured to monitor a momentary required power signal to reach the requested thrust and to adjust the pitch angle based on difference between currently measured momentary required power signal and a previously measured momentary required power signal.

Optionally, the controller configured to provide control signals to the thrust producer based on a requested optimization, wherein the requested optimization is based on input from at least one of human operator of the vehicle and an avionic system of the vehicle.

Optionally, the requested optimization is selected from a group including: operating in optimal power usage mode, operating in optimal range per power source mode, operating in optimal maximal provided power at any given flight condition, operating in optimal noise signature, operating in optimal aerodynamic efficiency of the propeller's blades, operating in a mode of linear response of the provided thrust versus the throttle's position and operating in optimal power during failure scenarios.

Optionally, the requested optimization is operating at reduced noise. Optionally, the controller is configured to provide control signals to the thrust producer to operate at a working point within an operational envelope, the working point selected from a group including maximal momentary provided power, rotation per minute (RPM) equalization, noise reduction, and cooling provided by the propeller to the motor.

Optionally, the controller is configured to provide control signals to a plurality of thrust producers included in the vehicle.

Optionally, the controller is configured to provide control signals to concurrently operate each of the thrust producers at a different working point.

Optionally, the control signals provided by the controller is configured to independently control the pitch angle of each of the thrust producers.

Optionally, the control signals provided by the controller is configured to independently control the thrust provided each of the thrust producers.

According to an aspect of some example embodiments there is provided a method for controlling at least one thrust producer that includes an electrical motor and a variable pitch propeller powered by the electrical motor, wherein the at least one thrust producer is included in a vehicle, the method comprising: providing control signals to a thrust producer to control motor throttle of the electric motor and pitch angle of the variable pitch propeller based on a momentary thrust of the thrust producer, a momentary pitch angle of the variable pitch propeller and a requested thrust, wherein the requested thrust is based on input from at least one of human operator of the vehicle and an avionic system of the vehicle.

Optionally, the method includes matching the momentary thrust to the requested thrust based on adjusting at least one of the motor throttle and pitch angle over a plurality of cycles in which the momentary thrust and the momentary pitch is determined.

Optionally, the method includes the momentary thrust is measured by a pressure gauge sensing a momentary pressure developing between the thrust producer and the vehicle.

Optionally, the method includes monitoring a momentary required power signal to reach the requested thrust and adjusting motor throttle based on difference between currently measured momentary required power signal and a previously measured momentary required power signal.

Optionally, the adjustment of the motor throttle is limited to a defined range, wherein the defined range is determined based on input from the avionic system.

Optionally, the method includes monitoring a momentary required power signal to reach the requested thrust and adjusting the pitch angle based on difference between currently measured momentary required power signal and a previously measured momentary required power signal. Optionally, the method includes providing control signals to the thrust producer based on a requested optimization, wherein the requested optimization is based on input from at least one of human operator of the vehicle and an avionic system of the vehicle.

Optionally, the requested optimization is selected from a group including: operating in optimal power usage mode, operating in optimal range per power source mode, operating in optimal maximal provided power at any given flight condition, operating in optimal noise signature, operating in optimal aerodynamic efficiency of the propeller's blades, operating in a mode of linear response of the provided thrust versus the throttle's position and operating in optimal power during failure scenarios.

Optionally, the requested optimization is operating at reduced noise.

Optionally, the method includes providing control signals to the thrust producer to operate at a working point within an operational envelope, the working point selected from a group including maximal momentary provided power, rotation per minute (RPM) equalization, noise reduction, and cooling provided by the propeller to the motor.

Optionally, the method includes providing control signals to a plurality of thrust producers included in the vehicle.

Optionally, the method includes providing control signals to concurrently operate each of the thrust producers at a different working point.

Optionally, the control signals provided by the system controller is configured to independently control the pitch angle of each of the thrust producers.

Optionally, the control signals provided by the system controller is configured to independently control the thrust provided each of the thrust producers.

Optionally, the method includes controlling the momentary provided power of each of the motors by selecting the pitch angle of each of the thrust producers so as to comply with at least one flight mode from the following: optimal power usage mode; optimal range per power source mode; optimal/maximal provided power at all flight conditions; optimal aerodynamic efficiency of the propeller's blades; low noise signature mode; and mode of linear response of the provided thrust versus the throttle's position.

Unless otherwise defined, all technical and/or scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the invention pertains. Although methods and materials similar or equivalent to those described herein can be used in the practice or testing of embodiments of the invention, exemplary methods and/or materials are described below. In case of conflict, the patent specification, including definitions, will control. In addition, the materials, methods, and examples are illustrative only and are not intended to be necessarily limiting.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING(S)

Some embodiments of the invention are herein described, by way of example only, with reference to the accompanying drawings. With specific reference now to the drawings in detail, it is stressed that the particulars shown are by way of example and for purposes of illustrative discussion of embodiments of the invention. In this regard, the description taken with the drawings makes apparent to those skilled in the art how embodiments of the invention may be practiced.

In the drawings:

FIG. 1 is a simplified block diagram showing a plurality of electrically propelled thrust producers and a controller in accordance with some example embodiments;

FIG. 2 is a simplified flow diagram to dynamically control thrust of an electrically propelled thrust producer in accordance with some example embodiments;

FIG. 3 is a simplified flow diagram to dynamically control thrust together with noise level of an electrically propelled thrust producer in accordance with some example embodiments; and

FIG. 4 is a simplified flow charge of an example method to select a working point within an operational envelope in accordance with some example embodiments.

DESCRIPTION OF SPECIFIC EMBODIMENTS OF THE INVENTION

The present invention, in some embodiments thereof, relates to a system and method to control thrust and, more particularly, but not exclusively, to a control system for a propelled thrust producer in an airborne vehicle that is fully electrically propelled.

According to some example embodiments, the electrically propelled thrust producer is dynamically controlled to operate at a selected working point within an operational envelope. The working point may be selected to achieve maximal momentary provided power, rotation per minute (RPM) equalization, noise reduction, cooling provided by the propeller to the motor. According to some example embodiments, the working point may be dynamically changed over the course of flight (or propulsion) to adapt to surrounding conditions and/or requests by the pilot.

According to some example embodiments, one or more of pitch angle of the propeller blades and motor throttle (RPM and/or torque output of the motor) is dynamically controlled based on input received to provide a desired performance. The input received may be input from one or more sensors sensing a momentary aerodynamic condition, a momentary operating condition of the airborne vehicle, e.g. generated noise and/or input from a pilot. Sensed momentary operating condition may include momentary thrust and momentary pitch angle of the blades. Momentary aerodynamic conditions may be sensed with an avionic system. According to some example embodiments, propelled vehicle includes more than one electric motor and propeller pair and the system and method provides synchronizing and/or coordinating operation of the electric motors and propellers include in the propelled airborne vehicle to achieve a desired performance. Optionally, the synchronizing and/or coordinating includes adapting operation of one or more of the electric motors and propellers to compensate for a detected failure associated with other electric motors and propellers included in the airborne vehicle.

Reference is now made to FIG. 1 is a simplified block diagram showing a plurality of electrically propelled thrust producers and a controller in accordance with some example embodiments. According to some example embodiments, a system 100 for propelling a vehicle, e.g. an airborne vehicle includes one or more electrically propelled thrust producers 50 controlled with a system controller 120. Two thrust generators 50 are shown as an example. Optionally, system 100 may include only one thrust generator 50, two thrust generators 50 or more than two thrust generators 50.

According to some example embodiments, each of thrust generators 50 includes an electrical motor 140 powered with power source 130 and a propeller 150 driven with electric motor 140. According to some example embodiments, propellers 150 includes blades 152 with adjustable pitch angles and a propeller pitch controller 155 configured to dynamically adjust the pitch angle of blades 152. Electric motor 140 includes a motor controller 145 configured to control RPM and/or torque of motor 140. Motor controller 145 may optionally and preferably be configured to control and/or measure momentary power, momentary thrust and/or momentary torque provided by its thrust generator 50. Optionally, motor controller 145 may be configured to operate at a defined operational envelope, e.g., maximal momentary provided power, RPM equalization, noise reduction, and/or cooling provided by the propeller to the motor. Optionally, momentary torque may be determined based on the winding’s current (amperage) output of motor 140. Optionally, momentary thrust is measured with a pressure gauge that is configured to sense momentary pressure developing between the thrust generator and the airborne vehicle’s body. In other example embodiments, momentary thrust may be measured by a load cell or strain gauge. Motor controller 145 may be a built-in controller, may be disposed out of the motor casing and/or may be integrated with system controller 120. Optionally, motor controller 145 is additional configured to monitor vibrations and the noise produced by its thrust generator 50. In some example embodiments, thrust producer 50 includes a sensor 148 to monitor its noise level. Optionally, sensor 148 is a microphone, accelerometers, and vibration sensor. Optionally, motor controller 145 may additionally transmit commands to propeller pitch controller 155 to adjust a pitch angle of blades 152 and thereby regulate the generated thrust by thrust generator 50. According to some example embodiments, control commands provided by motor controller 145 is based on input from system controller 120.

According to some example embodiments, system controller 120 is configured to control operation of each of thrust generators 50 to achieve a desired performance for the electrically propelled vehicle. System controller 120 may be provide commands to achieve a desired level of thrust, a desired level of noise emissions, a desired level of power efficiency and/or any combination thereof for each of thrust generators 50 as well for a combination of thrust generators 50, e.g. all thrust generators 50. For example, system controller 120 may operate thrust generators 50 to provide a required thrust while optimizing power at the expense of noise and/or minimizing noise at the expense of power efficiency.

According to some example embodiments, system controller 120 may receive input from a plurality of different sources based on which commands to each of thrust generators 50 are generated. According to some example embodiments, system controller 120 receives command requests from an avionic system 116 and/or a pilot 110. Avionic input from avionic controller 116 may be based on input from a plurality of sensors sensing parameters associated with movement of the vehicle, operation of the vehicle, e.g. power consumption of the vehicle and surrounding conditions. For example, avionic system 116 may be configured to identify undesired wind or turbulence induced movements of a vehicle based on input from sensors and issue a request to adjust a momentary thrust of one or more thrust generators 50 to assist in compensating or eliminating such movements. This compensation may be performed without user input. According to some example embodiments, avionic system and and/or its functionality may be partially or fully integrated with system controller 120.

System controller 120 may additionally receive command requests 208 from a pilot 110 operating the vehicle. Pilot input, e.g. command requests may include for example, a thrust request and/or a request to limit noise generated by thrust generators 50. System controller 120 additionally receives momentary input, e.g. feedback from each of thrust generators 50. Input from each of thrust generators 50 may include one or more of a momentary propeller pitch angle, noise and/or vibration levels measured at one or more thrust generator 50, and/or one or more of a momentary torque, momentary thrust and/or momentary power produced by each of thrust generators 50. Furthermore, system controller 120 may also provide feedback to a pilot regarding operation of the vehicle via a user interface 111.

According to some example embodiments, system controller 120 includes and/or is associated with non-volatile memory 125 configured for storing data, e.g. in one or more databases and/or tables accumulated over time. The accumulated data may be used to provide an “initial guess” to define thrust generator operational parameters, e.g. RPM, torque and/or propeller pitch to achieve a desired performance in a given situation and/or ambient condition based on past results. In some example embodiments, the accumulated data may also be used to identify malfunction based on comparing a current performance of one or more of thrust generators 50 with stored performance parameters in a comparable situation.

According to some example embodiments, based on the input received, system controller 120 may provide a command to a propeller pitch controller 155 to adjust a pitch angle of blades 152 and/or a command to motor controller 145 to adjust RPM and/or the produced torque of motor 140. Communication between system controller 12 and thrust generator 50 may be via a communication channel 60, e.g. a tethered or wireless communication channel.

According to some example embodiments, system controller 120 is configured to dynamically control momentary thrust of a vehicle based on avionic command requests from avionic input 212 provided by avionic system 116, pilot command requests based on pilot input 208 received from pilot 110, data accumulated in memory 125 and feedback from thrust generators 50 to achieve a desired performance of the vehicle as it is being propelled.

Reference is now made to FIG. 2 showing a simplified flow diagram to dynamically control thrust of an electrically propelled thrust producer in accordance with some example embodiments. According to some example embodiments, the dynamic control may be performed by system controller 120 (FIG. 1). According to some example embodiments, pilot input 208 and/or avionic input 212 may include a thrust request for one or more thrust generators 50 and/or for the airborne vehicle as a whole. Optionally, pilot input 208 is provided via the pilot throttle controlled by the pilot. Avionic input 212 may provide a request to assist in compensating or eliminating undesired movement of the vehicle due to wind or turbulence.

According to some example embodiments, control loop 200 provides a stabilized yet dynamic method of setting the momentary values of power/torque and the momentary values of pitch angle to achieve momentary thrust with controllable efficiency, by setting a working point within the performance envelope at the desired set point. According to some example embodiments, a control loop 200 includes an external control loop 210 configured to control momentary propeller pitch angle based on measured momentary thrust as compared to a current thrust request and an internal control loop 250 configured to control thrust performance of the system with power by adjusting the motor throttle. Optionally, internal loop 250 provides stabilized power changes that are used as input to the external control loop 210.

According to some example embodiments, the momentary thrust requests from the pilot and/or the avionic system may be received and optionally combined at block 220. Output from block 220 may be provided to control loop feedback signal adder 230. Control loop feedback signal adder 230 may compare the received requests to a measured momentary thrust 270 and define a momentary delta (or differential) control signal based on the comparing. The momentary delta control signal may be provided to block 251. In block 251, a motor-throttle setting is defined to provide a desired adjustment to the measured momentary thrust based on the momentary delta signal.

At block 252, momentary power required to adjust the thrust may be measured and compared in decision block 253 to a previous measurement of the required power. If the momentary required power is less than the previous measurement of the required power (YES), then the control may return to block 251 to re-adjust the mo tor- throttle. In some example embodiments, this internal control loop provides a stabilized control loop by converging the momentary thrust to the desired thrust over a plurality of increments. Optionally, convergence to a desired thrust may be accelerated by forwarding the measurement of the momentary required power in block 252 to block 254 during the first cycle. In some example embodiments, based on input from block 252, a control command is defined in block 254 to increase propeller pitch angle. Optionally, the increase is predefined. In some embodiments, the signal for increasing the propeller pitch given at block 215 may be set, or may be confined between defined lower and upper limits, by a signal from the avionic system, for example so that the initial propeller pitch increase signal is set to be within a predefined range, as set in block 215. According to some example embodiments, the increase is selected to provide a pre-defined correction tendency. Optionally, during other control cycles, e.g. cycles other than the first cycle, block 254 may act as neutral control line that does not provide input to block 251.

According to some example embodiments, at decision block 253, when the momentary required power is not less than the previous measurement of the required power (NO), the propeller pitch angle may be decreased in block 240. Optionally, input from block 215 may be provided to define range of propeller pitch angle that may be used to decrease the momentary propeller pitch angle. The decrease signal from block 240 may be provided to block 260. In block 260 the throttle is adjusted to reach the thrust requested on block 220. A new momentary thrust may be measured in block 270 and provided to signal adder 230.

The method for controlling thrust as described herein, involves making small variations of the motor RPM/torque and the propeller blades pitch, while measuring thrust and/or power. Since, generally speaking, the thrust increases while increasing RPM/torque and the same, while increasing the propeller blades pitch (coarser pitch), in the plane of a graph of RPM/torque vs. propeller blade pitch, one of plurality of work points for a given required thrust may be selected.

Reference is now made to FIG. 3 showing a simplified flow diagram to dynamically control thrust together with noise level of an electrically propelled thrust producer in accordance with some example embodiments. According to some example embodiments, the dynamic control may be performed by system controller 120 (FIG. 1). According to some example embodiments, pilot input 208 and/or avionic input 212 includes a thrust request and/or a noise reduction request.

Optionally, pilot input 208 is provided via the pilot throttle controlled by the pilot and/or by a pilot user interface.

Noise produced by thrust generator 50 may be affected by several parameters including propeller 150 given blade distribution of the pitch angle along blade 152, controllable blade momentary pitch angle, given length of blade 152, given number of blades 152 in propeller 150, RPM of propeller 150, airspeed, air density and humidity. Similar to the relationship between selected RPM and/or torque vs. propeller blade pitch for a given required thrust, with respect to noise produced by propeller 150 of thrust generator 50, a plurality of different pairs of pitch angles and RPM of motor 140 may be selected for a given required thrust and a given airspeed. From these plurality of pairs, some pairs may produce more noise than others. Thus, when energetic efficiency of one of thrust generators 50 and the noise it produces are considered, in the space of design/control defined by RPM of motor 140, pitch angle, produced noise, provided thrust - an operation envelope confined within a defined range of changes for each of the above mentioned variables may be defined. For example, a small variation, which includes decreasing the RPM and/or torque of motor 140 while increasing pitch angle, may generate roughly the same thrust. Similarly, a small variation which includes increasing the RPM and/or torque of motor 140 while decreasing pitch angle, may also generate roughly the same thrust. Yet, due to the variation, the efficiency of the system may change, so power consumption may vary as well along with a noise signature. According to some example embodiments, a control loop 300 includes an external control loop 310 configured to control momentary motor throttle based on measured momentary thrust and/or noise, and an internal control loop 350 configured to control thrust performance and/or noise of the system with power by adjusting propeller pitch angle. Optionally, internal loop 350 provides stabilized power changes that are used as input to the external control loop 310.

According to some example embodiments, the momentary thrust and/or noise requests received from pilot input 208 and/or avionic input 212 may be received and optionally combined at block 320. Output from block 320 may be provided to control loop feedback signal adder 330. Control loop feedback signal adder 330 may compare the received requests to a measured momentary thrust or noise 370 and define a momentary delta (or differential) control signal based on the comparing. The momentary delta control signal may be provided to block 351. Optionally, both momentary thrust and momentary noise is measured and a delta for each is defined. In block 351, a propeller pitch angle is defined to provide a desired adjustment to the measured momentary thrust and/or noise based on the momentary delta signal(s).

At block 352, momentary required power required to adjust the thrust may be measured and compared in decision block 353 to a previous measurement of the required power. If the current required power is less than the previous measurement of the required power (YES), then the control may return to block 351 to re-adjust the power by controlling propeller pitch angle. In some example embodiments, this internal control loop provides a stabilized control loop by converging to the desired thrust over a plurality of increments. Optionally, convergence to a desired thrust may be accelerated by forwarding the measurement of the momentary required power in block 352 to block 354 during the first cycle. In some example embodiments, based on input from block 352, a control command is defined in block 354 to increase motor throttle. In some embodiments, the signal for increasing the motor throttle given at block 315 may be set, or may be confined between defined lower and upper limits, by a signal from the avionic system, for example so that the initial propeller pitch increase signal is set to be within a predefined range, as set in block 315. According to some example embodiments, the increase is selected to provide a pre-defined correction tendency. Optionally, during all other control cycles, block 354 may act as neutral control line that does not provide input to block 351.

According to some example embodiments, at decision block 353, when the current required power is not less than the previous measurement of the required power (NO), the motor throttle may be decreased in block 340. Optionally, input from block 315 may be provided to define range of motor throttle changes that may be used to decrease the momentary propeller pitch. The decrease signal from block 340 may be provided to block 360. In block 360 the propeller pitch angle is adjusted to reach the thrust requested on block 320. A new momentary thrust may be measured in block 370 and provided to signal adder 330.

The method for controlling thrust as described herein, involves making small variations of the motor RPM and/or torque and the propeller blades pitch angle, while measuring thrust, power and/or noise level. Since roughly the thrust increases while increasing RPM and/or torque and the same, while increasing the propeller blades pitch (coarser pitch), a small variation which includes decreasing the RPM and/or torque while increase the propeller blades pitch (or vice versa) will generate roughly the same thrust as before. Yet, due to the variation, the efficiency of the system may change, so power consumption as well noise signature may vary.

Reference is now made to FIG. 4 showing a simplified flow charge of an example method to select a working point within an operational envelope in accordance with some example embodiments. According to some example embodiments, a working point within an envelope for achieving a thrust request (or a noise request) may be selected to provide optimization of one or more parameters. Optionally, the one or more parameters includes power consumption, and/or noise. Optionally, optimization includes minimizing power consumption and/or minimizing noise for a given thrust request.

According to some embodiments of the present invention, system controller 120 receives a thrust request (block 405). In addition, the system controller may also receive a request to optimize a propulsion parameter of the vehicle or a specific thrust generator (block 410). Optionally, the requested optimization is to minimize power consumption and/or minimize noise. Additional parameters may be a request to minimize motor power per given speed, maximize power, provide a linear response to the provided thrust versus throttle position, and/or achieve maximum cooling of one or more thrust generators. A combination of parameters for optimization may be requested. The thrust request (block 405) as well as the optimization request (block 410) may originate from the pilot 110 or from the avionic system 116. According to some example embodiments, system controller is configured to incrementally adjust motor throttle and pitch angle of one more thrust generators to achieve the requested thrust (block 415). The incremental adjustment may be as disclosed in reference to FIG. 2 and FIG. 3. Noise and/or power consumption may be measured during the incremental adjusting and a trend in the noise and/or power consumption measured over a plurality of cycles, e.g. at least two cycles may be monitored (block 420). Decision block 425 determines if the incremental changes to achieve a desired thrust is providing a desired optimum. If the increments defined are leading to an optimum, system controller 120 may continue to adjust motor throttle and pitch angle in a same direction until the thrust request is achieved. If the increments defined are not leading to an optimum, system controller 120 may switch a direction at which it is adjusting motor throttle and pitch angle to achieve the thrust request while also optimizing power consumption and/or noise (block 430). Once a desired and/or defined optimum is achieved, system 120 may maintain that optimum while continuing making small variations in both directions from time to time to ensure that the optimization is still valid for current flight conditions. If the surrounding conditions have changed, optimization may be updated.

In this way, the optimization is performed continuously so that, per each envelope point(s) defined by altitude, air density, humidity, ambient temperature, air speed and/or vehicle weight, etc. a local optimum may be maintained.

The optimization results, such as minimal power consumption and/or minimal noise setup per required thrust per operation envelope point, can further be stored in a non-volatile memory 125 generating a database which can be used as an“initial guess” to initialize the setup after a thrust request change has been received or at the beginning of the takeoff, in order to save optimization time. This database may also be used as a reference to help identify attrition, problems, failures and malfunctions of the propulsion units, by comparing the nominal (known) optimization results (torque, pitch, as stored in the database, and the prior achieved optimization values (power, thrust, noise) to the current, instantaneous optimization results. A major difference (beyond a pre-set threshold) can indicate about a problem in the propulsion system. Any anomalies in the measured parameters can further be stored and then studied after landing, as part of maintenance and preventive maintenance procedure. Thus, system controller 120 may also be used as a HUMS (Health and Usage Monitoring System). For instance, optimal range per power mode may be defined as a mode of operation in which minimal motor power is produced / dissipated per given speed. Another optimization mode of operation may be an optimal maximal power mode, which may be defined as operation of the propeller blades at RPM ensuring blade tip airspeed below 0.8 Mach and blade pitch angle just below stall angle. In another example, optimal aerodynamic efficiency mode of the propeller's blades may be defined as operation of the propeller in conditions providing highest thrust-to-blades aerodynamic drag ratio. In an embodiment, a mode of linear response of the provided thrust versus the throttle's position may be defined as mode of operation at which the change of magnitude of thrust per a given change of the throttle position is equal throughout the entire range of change of the throttle position between flight idle and full power positions.

Furthermore, per constant torque and pitch command, the measured thrust variations, noise, and vibrations can be measured and used as an indication for the propeller balancing status, and also be used to perform automatic motor cut-off in case of severe imbalance, for example in a case where the propeller has been hit by a bird or by runway debris.

Another important advantage of embodiments according to the subject matter is that the thrust closed loop control, as disclosed herein, for a vehicle with more than one motor/propeller may automatically generate a linear relation between the pilot’s throttle position and the provided thrust, which is more intuitive and easier to control for the airborne vehicle operator. Thus, one throttle may be used by the pilot to indicate the trust demand for the aircraft, while the control system will distribute the thrust control signal to each of the multiple motors/propellers on the aircraft, saving the pilot the effort to balance the thrust of the different motors. In some embodiments the system may control the thrust of each of the electrical motors to achieve operation in maximal energy efficiency by means of setting the thrust of each of the motors so that the fuselage of the airborne vehicle is directed, with respect to the direction of flight, so that the energetic efficiency is maximized, or the aerodynamic drag of the vehicle is minimized. According to some embodiments the momentary minimal drag, as achieved in a certain flight, may be recorded and saved and may be compared in the future with more recent minimal drag figures, to identify possible evolving body distortions or curvatures, or to detect aerodynamic disorders of the airborne vehicle’s fuselage, such as a loose panel or an opened fuselage door during flight, which may cause longitudinal imbalanced fuselage aerodynamic drag.

As described in International Patent Publication No. WO2019/092708, additional thrust corrections may be received from the Yaw Restraining system to allow stable flight without the pilot intervention, making the thrust operation intuitive and simple. The yaw restraining system is adapted to restrain turbulence induced yaw or side movements of a fully electrically propelled airborne vehicle (AV) having at least two electrical motors, disposed one on the left and one on the right side of a longitudinal central axis of the AV. The system includes a controller adapted to steer the AV with fully electrically powered propelling. The control is based on based on receiving indications of ambient induced yaw and/or lateral movements of an airborne vehicle and pilot induced control signals of the airborne vehicle. One or more control signals are issued to at least one of the at least two electrical motors of the fully electrically propelled AV adapted to compensate the effect of the ambient induced yaw and/or lateral movements.

In some instances, pilots’ input, wind disturbance, etc., may momentarily tend drive the motor RPM out of any optimum for maneuverability. Once these conditions are over, the system will optimize again automatically.

System controller may additionally optimize its operation for achieving extended cooling, at normal conditions (max continuous power) and for emergency conditions (max momentary power), then the system will limit the possible operation time according to the actual conditions. Such modes of operation may be switched into, or selected by, either the operator of the vehicle or by the avionic system. Accordingly, an input for further aspect of optimization may be the motor momentary heat and available cooling power - to allow the pilot use/demand momentary boost the extra thrust, while maintaining the motor’s heat within allowable limits of temperature and duration.

It is appreciated that certain features of the invention, which are, for clarity, described in the context of separate embodiments, may also be provided in combination in a single embodiment. Conversely, various features of the invention, which are, for brevity, described in the context of a single embodiment, may also be provided separately or in any suitable subcombination or as suitable in any other described embodiment of the invention. Certain features described in the context of various embodiments are not to be considered essential features of those embodiments, unless the embodiment is inoperative without those elements.

In addition, any priority document(s) of this application is/are hereby incorporated herein by reference in its/their entirety.