Abstract: A method of operating an electrically powered rotorcraft of the type having a fuselage and a set of N rotors driven by a set of electric motors and coupled to the fuselage, N?4, under a failure condition preventing ordinary operation of the rotorcraft. The method includes entering a failsafe mode of operation wherein autorotation of at least four of the rotors is enabled. The method also includes using electrical braking associated with a selected group of the rotors to control pitch, roll and yaw of the rotorcraft.

Abstract: A method of optimizing the noise generated by a rotorcraft on the ground, said rotorcraft including a hybrid power plant, at least one rotor, and an electrical energy source. Said method makes it possible to monitor whether each engine of said power plant is on or off, and to monitor the state of each electric machine of said hybrid power plant. Said method also makes it possible to monitor whether said rotorcraft is on the ground. Then, each engine that is on is controlled to reach an idling speed, or indeed to be caused to stop by being switched off, and said electric machine Is regulated on a setpoint speed of rotation of a rotor so as to drive each rotor while also limiting the noise generated by said hybrid power plant.

Abstract: A system and a method are disclosed for a vehicle control and interface system configured to facilitate control of different vehicles through universal mechanisms. The vehicle control and interface system can be integrated with different types of vehicles (e.g., rotorcraft, fixed-wing aircraft, motor vehicles, watercraft, etc.) in order to facilitate operation of the different vehicles using universal vehicle control inputs. In particular, the vehicle control and interface system converts universal vehicle control inputs describing a requested trajectory of a vehicle received from one or more universal vehicle control interfaces into commands for specific actuators of the vehicle configured to adjust a current trajectory of the vehicle to the requested trajectory. In order to convert the universal vehicle control inputs to actuator commands the vehicle control and interface system processes the universal vehicle control inputs using a universal vehicle control router.

Abstract: Techniques are described to determine parameters and/or values for a control model that can be used to operate an autonomous vehicle, such as an autonomous semi-trailer truck. For example, a method of obtaining a data-driven model for autonomous driving may include obtaining data associated with a first set of variables that characterize movements of an autonomous vehicle over time and commands provided to the autonomous vehicle over time, determining, using at least the first set of data, non-zero values and an associated second set of variables that describe a control model used to perform an autonomous driving operation of the autonomous vehicle, and calculating values for a feedback controller that describes a transfer function used to perform the autonomous driving operation of the autonomous vehicle driven on a road.

Abstract: An aircraft is provided. The aircraft includes a body having a seat adapted for a user to sit atop, a set of propulsion units for providing lift to the aircraft, and a steering mechanism for controlling movement of the aircraft. The steering mechanism includes a set of handlebars adapted for the user to grasp while sitting atop the seat. The steering mechanism also includes a steering column that is rigidly connected to the set of handlebars, where the set of handlebars and the steering column are rotatable about a longitudinal axis of the steering column. The steering mechanism further includes one or more sensors for detecting rotation of the steering column. The steering mechanism enables the user to control a yaw of the aircraft by turning the set of handlebars about the longitudinal axis of the steering column.

Abstract: An aircraft is configured for thrust-borne lift in a vertical takeoff and landing flight mode and wing-borne lift in a forward flight mode. The aircraft includes an airframe having a first wing and a first payload station. A distributed propulsion system that is coupled to the airframe includes a plurality of propulsion assemblies configured to provide vertical thrust in the vertical takeoff and landing flight mode and forward thrust in the forward flight mode. A control system is operably associated with the distributed propulsion system and is operable to independently control each of the propulsion assemblies. A payload module is configured to be transported by the airframe from a pickup location to a delivery location. The payload module is magnetically coupled to the first payload station during transportation and, responsive to a command from the control system, is magnetically decoupled from the first payload station at the delivery location.

Abstract: A compact load cell that simultaneously measures normal and shear forces in a load plane offset from a sensor plane by a distance h. The compact load cell comprises at least three force sensing elements (preferably four) arranged in the sensor plane about a point and spaced a distance d from the point. All force sensing elements may be spaced by the same distance or the distance may be different for one or more force sensing elements. Each force sensing element comprises a pressure sensor encased in a force transmission medium. A load plate is in contact with the force transmission medium and a load beam is connected at one end to the load plate above the point of the sensor plane and extends to the load plane. Forces acting in the load plane are transmitted to the sensor plane by the load beam and load plate. The forces are resolved to determine the normal and shear forces acting at the load plane. The compact load cell may be applied to determine forces acting on, for example, an unmanned aerial vehicle.

Abstract: A ganged servo flight control system for an unmanned aerial vehicle is provided. The flight control system may include a swashplate having first, second, and third connection portions; a first control assembly connected to the first connection portion of the swashplate; a second control assembly connected to the second connection portion of the swashplate; and a third control assembly connected to the third connection portion of the swashplate. The first control assembly may include two or more servo-actuators connected to operate in cooperation with each other.

Abstract: A method of operating an under-actuated actuator system including a plurality of actuators (3), preferably for operating a multiactuator aerial vehicle (1), wherein the actuators (3) are individual propulsion units of the multiactuator aerial vehicle (1), each actuator having a maximum physical capacity umax, the method including: controlling the actuators (3) by with an actual control input u?k computed from an allocation equation u=D?1up, wherein D?1 is an inverse allocation matrix and up?m is a pseudo control input defined by a system dynamics equation m(x){umlaut over (x)}+c(x,{dot over (x)})+g(x)+G(x)up=fext, wherein x?n is an n-dimensional configuration vector of the system, m(x)?n×n is a state dependent generalized moment of inertia, c(x,{dot over (x)})?n are state dependent Coriolis force, g(x)?n are gravitational forces and fext?n are external forces and torques, and G(x)?n×m is a control input matrix which contains the information of under-actuation.

Abstract: A system and method for protecting a rotorcraft from entering a vortex ring state, the method including monitoring a vertical speed of a rotorcraft, comparing the vertical speed to a vertical speed safety threshold, and performing vortex ring state (VRS) avoidance in response to the vertical speed exceeding the vertical speed safety threshold. The performing the VRS avoidance includes determining a power margin available from one or more engines of the rotorcraft, limiting the vertical speed of the rotorcraft in response to the power margin exceeding a threshold, and increasing a forward airspeed of the rotorcraft in response to the power margin not exceeding the threshold.

Abstract: A three-dimensional directional control assembly for a dual-mode aircraft, wherein the aircraft is capable of vertical and forward thrust. The assembly comprising a support structure, wherein the support structure is coupled to a dual-mode aircraft. The assembly further comprises a control stick coupled to support structure, wherein the control stick having a length and radius is configured to be manipulated along a plurality of axes, wherein the manipulation of the control stick produces an electronic signal. The assembly further comprises a first interface device disposed on the control stick configured to receive an interaction and enable a thrust element to spin as a function of the interaction. The assembly further comprises a second interface device, wherein the second interface is configured to receive an interaction and disable the thrust element as a function of the interaction.

Abstract: A method of facilitating the piloting of a hybrid rotorcraft that comprises a lift rotor and at least one propulsion rotor together with at least one engine operating in compliance with at least one rating. For at least one rating, onboard calculator determines a first power margin of the power plant that is available for the lift rotor and at least one second power margin that is available for said at least one propulsion rotor. A single indicator displays a line together with a first index pointing to said line to illustrate a current operating point of the lift rotor, and a second index pointing to said line to illustrate a current operating point of said at least one propulsion rotor. For each monitored rating, a first symbol is spaced apart from the first index by a first distance illustrating the first power margin. A second symbol is spaced apart from the second index by a second distance illustrating the second power margin.

Abstract: An aircraft of a modular type including: at least one rotor suitable for providing in full or in part propulsion and/or lift for the aircraft; at least one power plant of the combustion engine type or of the electric motor type; a main gearbox, for mechanically transmitting drive torque generated by the at least one power plant to the at least one rotor; and an avionics system for assisting in piloting the aircraft. In accordance with the invention, the avionics system is configured for automatically providing the assistance in piloting the aircraft when the aircraft has a first power plant only or when the aircraft has a first power plant and a second power plant.

Abstract: Methods and systems for longitudinal control of aircraft during flight are disclosed. One method comprises receiving a commanded normal acceleration of the aircraft and computing a target pitch rate for the aircraft based on the commanded normal acceleration. The target pitch rate is used in a control technique for controlling one or more flight control surfaces of the aircraft to achieve the target pitch rate for the aircraft. The control technique can include (e.g., incremental) nonlinear dynamics inversion.

Abstract: Payload engagement systems and related methods. A payload engagement system includes a vehicle with at least one engagement latch and a payload with at least one engagement receptor. Each engagement latch is configured to be selectively transitioned between an engaged configuration and a disengaged configuration. The payload engagement system includes an alignment guide configured to guide the payload to a predetermined coupling position prior to each engagement latch transitioning to the engaged configuration. A method of utilizing a payload engagement system includes positioning a vehicle on a first side of a docking platform, guiding a payload toward the vehicle, and coupling the payload to the vehicle via engagement between at least one engagement latch and at least one engagement receptor. Specifically, the coupling the payload to the vehicle includes transitioning each engagement latch from a disengaged configuration to an engaged configuration.

Abstract: A system for airspeed estimation utilizing propulsor data in electric vertical takeoff and landing (eVTOL) aircraft is provided. The system generally comprises at least a propulsor, at least one sensor and a flight controller. The at least a propulsor is mechanically coupled to a body of an eVTOL aircraft, wherein the at least a propulsor is configured to propel the eVTOL aircraft. The at least one sensor is configured to detect a torque of the at least a propulsor, and transmit the torque of the at least a propulsor. The flight controller is configured to receive the torque of the at least a propulsor and determine an airspeed of the eVTOL aircraft as a function of the torque of the at least a propulsor. A method for airspeed estimation utilizing propulsor data in electric vertical takeoff and landing (eVTOL) aircraft is also provided.

Abstract: An operation method includes sensing, by a movable device, whether the movable device is thrown out by a thrower; in response to a sensing of being thrown out, controlling the movable device to hover in air; and after controlling to hover, performing, by the movable device, an aerial operation of the movable device, such as capturing images.

Abstract: A system for flight control for managing actuators for an electric aircraft is provided. The system includes a controller, wherein the controller is designed and configured to receive a sensor datum from at least a sensor, generate an actuator performance model as a function of the sensor datum, identify a defunct actuator of the electric aircraft as a function of the sensor datum and the actuator performance model, generate an actuator allocation command datum as a function of at least the actuator performance model and at least the identification of the defunct actuator, and perform a torque allocation as a function of the actuator allocation command datum.

Abstract: A content-driven and content delivery UAV system. The UAV system includes a content source to provided pressurized content to the UAVs via a content transmission media. The pressurized content is utilized to drive a mechanical propulsion and steering system to keep the UAV aloft and direct it to a particular location. The pressurized content received by the UAVs can be directed back to the content source, to another UAV and or discharged from the UAV to a desired target. Thus, the UAVs may include a nozzle or valve for discharging the content and thus delivering the content to a desire location.

Abstract: An unmanned aerial vehicle (UAV) can deliver a package to a delivery destination. Packages delivered by a UAV may be lowered towards the ground while the UAV continues to fly rather than the UAV landing on the ground and releasing the package. Packages may sway during lowering as a result of wind or movement of the UAV. A package sway may be monitored and mitigated by rapidly paying out a tether, when using a winch mechanism, to dissipate the energy of the sway as downward energy. Further, the UAV may navigate in the direction of the sway or reduce the altitude of the UAV to dissipate the energy of the sway. Open-loop and/or closed loop drop techniques may be utilized to lower a package from the UAV, and the package may be released in the air or on the ground.

Abstract: A system and method of controlling a position of a structure. A position command indicating a desired position for the structure and a position feedback signal indicating the position of the structure are received. A position control signal is generated based on a difference between the desired position and the position indicated by the position feedback signal. A stop feedback signal relative to the position of the structure is received. A stop control signal is generated based on the stop feedback signal and a stop condition for the structure. One of the position control signal and the stop control signal is selected. The selected one of the position control signal and the stop control signal is provided to an actuator for controlling the position of the structure.

Abstract: A rotary wing aircraft and a rotor assembly of a rotary wind aircraft is disclosed. The rotary wing aircraft includes at least one engine, and the rotor assembly is coupled to the at least one engine. The rotor assembly includes a first rotor hub, a second rotor hub, and a shaft fairing between the first rotor hub to the second rotor hub, the shaft fairing defined by a chord that varies between the first rotor hub and the second rotor hub.

Abstract: A method for limiting torque on a rotorcraft. The rotorcraft comprises an installation having a rotor, the installation including at least three motors driving a power transmission gearbox, the MGB including a rotor mast for moving the rotor. The method comprises a step of determining a engine torque limit for each of at least the three motors, each engine torque limit being established by a control computer of the aircraft by taking into consideration the distribution among the at least three motors of the total power (Ptot) delivered by the at least three motors for enabling the rotorcraft to operate.

Abstract: A ground proximity warning system for an aircraft includes a plurality of alarm generators, each able to generate an alarm by verifying evolution conditions of the aircraft specific to each alarm generator, the verification using data obtained from at least one measuring sensor of the aircraft. The ground proximity warning system includes a unit for selective deactivation of at least some of the alarm generators, able to be implemented during a search and rescue mission carried out by the aircraft, and an auxiliary alarm generator, capable of emitting a ground proximity alarm based on the safety height chosen for the search and rescue mission, when the selective deactivation unit is implemented.

Abstract: A monitoring system including pieces of measuring equipment and an LPWAN reception terminal. Each piece of measuring equipment has a sensor arranged to measure a parameter of the aircraft, an LPWAN antenna and an LPWAN transmitter, an independent power source that powers the piece of measuring equipment, a main cut-off member connected between the independent power source and the LPWAN transmitter, and a main control component arranged to monitor operating parameters of the LPWAN transmitter and to open and close the main cut-off member selectively as a function of the operating parameters.

Abstract: In order to eliminate control problems caused by a manipulated variable limitation in the oscillation control of an oscillatable technical system, a restriction ( d n ? u dt n ? m ? ? i ? ? n , d n ? u dt n ? m ? ? ax ) of at least one time derivative of the manipulated variable (u) in a control law for calculating the manipulated variable (u) is taken into account.

Abstract: An exemplary method for controlling low speed flight of an aircraft having a controller receiving pilot input includes transitioning from a translational rate command (TRC) to a linear acceleration command (LAC) when the controller is displaced above a control transition displacement (CTD), and while in LAC holding speed when the controller is relaxed to CTD.

Abstract: An electric power tethering system for an aircraft having a vertical takeoff and landing flight mode including a takeoff phase and/or a hover phase includes a surface power source and a power tether having a surface end configured to couple to the surface power source and an aircraft end configured to couple to the aircraft. The power tether is configured to transmit power from the surface power source to the aircraft in the takeoff phase and/or the hover phase. The power tether is detachable to decouple the surface power source from the aircraft in response to a power tether release event during flight.

Abstract: A vehicle capable of multiple varieties of locomotion having a main body; a plurality of motors and blades providing flying capability; each motor being associated with and powering a blade assembly; two legs extending from opposing sides of the main body creating a ground propulsion system. The ground propulsion system having two legs; each leg connected to a track body at the opposing leg end; each track body comprised of a plurality of drive gears; each track body connected to and retaining a track providing ground propulsion. The vehicle can either drive or fly based on its base structure, in additional to carrying a payload. The payload is carried below the main body of the vehicle and between the tracks or running gear. When the vehicle is in flight, the tracks are able to rotate up into a fly/flight mode to protect the blades during flight.

Abstract: An aircraft flight control system includes a first actuator attached to a wing main body, a horn arm configured to transmit an output of the first actuator to a control surface, and a second actuator that is a rotary actuator and attached to the control surface. At least one of the first actuator and the second actuator is an electromechanical actuator (EMA). A first end of the horn arm is coupled to an output terminal of the first actuator, and a second end of the horn arm is fixed to an output terminal of the second actuator. The second actuator is attached to the control surface such that a turning axis of the output terminal is parallel to or coincides with a fulcrum axis (hinge line) of the control surface.

Abstract: An unmanned aerial vehicle system includes a ground station, a tether assembly coupled to the ground station, and an unmanned aerial vehicle. The unmanned aerial vehicle having a quick release mechanism selectively coupled to the tether assembly to restrain movement of the unmanned aerial vehicle. The quick release mechanism is electrically actuatable to decouple the tether assembly from the unmanned aerial vehicle for enabling the unmanned aerial vehicle to fly freely.

Abstract: A regulator device for regulating a control setpoint for a speed of rotation, written NR, for at least one main rotor of a rotorcraft, the rotorcraft including at least one measurement member for taking measurements representative of a current vertical elevation of the rotorcraft relative to a reference level Ref; and measurement means serving to measure at least one vertical component of a travel speed of the rotorcraft relative to the air surrounding the rotorcraft, the regulator device for regulating the control setpoint of the speed including management means for automatically controlling the control setpoint for the speed in accordance with at least two predetermined control relationships that are distinct from each other.

Abstract: A rotorcraft having an antivibration system, the antivibration system being arranged at the interface between a fuselage of the rotorcraft and a casing of a main power transmission gearbox, or “MGB”, in order to transmit rotary motion generated by an engine of the rotorcraft to a main rotor providing the rotorcraft at least with lift, and possibly also propulsion, the antivibration system including calculation means for analyzing as a function of time the dynamic excitation and the resulting vibration transmitted to the fuselage of the rotorcraft.

Abstract: A method for predicting vibrations in an aircraft comprising an active vibration reduction system includes estimating a first vibration amplitude or frequency resulting from adjustments by the active vibration reduction system and the respective sensitivities of the aircraft depending on the flying state using a statistical mathematical process, recording a second vibration amplitude or frequency by a sensor, generating a pseudo-vibration profile by combining the first and second vibration amplitudes or frequencies, comparing the pseudo-vibration profile with a predefined target vibration profile, and outputting a signal when a specific threshold value has been exceeded.

Abstract: The present invention includes a system and method for slowing the rotation of a rotor using, for example, rotor brake system for a rotorcraft comprising: one or more generators connected to a main rotor gearbox; an electric distributed anti-torque system mounted on a tail boom of the rotorcraft comprising two or more electric motors connected to the one or more generators, wherein the two or more electric motors are connected to one or more blades; and wherein a rotation of the rotor is slowed by placing a drive load on the main rotor gearbox with the one or more generators to bleed the mechanical power from rotor into electrical power via the two or more electric motors, wherein the electric distributed anti-torque system generates thrust in opposing directions.

Abstract: Various embodiments include devices and methods for controlling a robotic vehicle. Each electronic speed controller (ESC) of the robotic vehicle may receive open loop flight control information from a flight controller or another processing device of the robotic vehicle. In some embodiments, each ESC may store the provided open loop flight control information in a memory. In response to detecting a loss of control signals from the flight controller, each ESC may access the stored open loop flight control information and perform control of a motor associated with each ESC based on the open loop flight control information. The open loop flight control information may be a sequence of motor control instructions to be performed over a period of time, or parameterized information or vehicle state information that enables each ESC to generate a sequence of motor control instructions.

Abstract: An embodiment of the invention may include a processor-implemented method and computer program product for temperature control. The embodiment may include performing, by at least one unmanned aerial vehicle, at least one local climate control action at a location based on data received from a wearable computing device of at least one individual.

Abstract: The present invention provides a drone comprising: a drone body; main rotors generating a driving force; sub-rotors generating a driving force instead of the main rotor above and below the main rotor, respectively; connection frames connecting the sub-rotors to the drone body above and below the main rotor, respectively; a detector detecting failure of the main rotors; and a controller controlling the sub-rotors to generate a driving force when detecting failure of the main rotor, wherein the connection frame is rotatably connected to the drone body, rotates, and moves the sub-rotor; wherein each connection frame comprises a rotation frame protruded upward or downward from the drone body and rotatably connected to the drone body; a horizontal frame horizontally connecting the sub-rotor to the rotation frame, and a balance weight protruded from the rotation frame in an opposite direction to the horizontal frame.

Abstract: A method for providing a driver of a vehicle towing a trailer with reversing information, comprising the steps of: capturing image data of a region behind the trailer; measuring an angle between the vehicle and the trailer; generating auxiliary data 5 comprising reversing aid information at least in part in accordance with the angle; generating display data in accordance with the image data and the auxiliary data; and presenting the display data on a display.

Abstract: An rotorcraft including a pilot control, a pilot control position sensor connected to the pilot control and operable to generate a position signal indicating a position of the pilot control, a flight control computer (FCC) in signal communication with the pilot control position sensor and operable to provide a tactile cue in the pilot control in response to the position signal indicating the position of the pilot control exceeds a threshold associated with an operating limit, and further operable to determine a tactile cueing value for the tactile cue according to a relationship between the position of the pilot control and the threshold, and generate a cue control signal according to the tactile cueing value, and a tactile cue element connected to the pilot control and in signal communication with the FCC and operable to control action of the pilot control in response to the cue control signal.

Abstract: The rotary wing drone comprises at least one rotor carried by a drone structure, wherein the drone structure comprises a drone body and at least one group of arms comprising a plurality of arms rotatably mounted on the drone body about the same axis of rotation, between a deployed position for flight and a folded position for transport.

Abstract: An exemplary tail rotor includes a first blade assembly configured to rotate in a first direction about an axis of rotation and a second blade assembly configured to rotate in a second direction about the axis of rotation.

Abstract: An unmanned aircraft includes a forward propulsion system comprising one or more forward thrust engines and one or more corresponding rotors coupled to the forward thrust engines; a vertical propulsion system comprising one or more vertical thrust engines and one or more corresponding rotors coupled to the vertical thrust engines; a plurality of sensors; and a yaw control system, that includes a processor configured to monitor one or more aircraft parameters received from at least one of the plurality of sensors and to enter a free yaw control mode based on the received aircraft parameters.

Abstract: A method of controlling a tail rotor system includes pivoting a swashplate of the tail rotor system about an axis passing through a diameter of the swashplate. Pivoting the swashplate causes a first linkage of a first pair of linkages coupled between the swashplate and a collective crosshead to move in a first direction and a second linkage of the first pair of linkages coupled between the swashplate and the collective crosshead to move in a second direction that is opposite the first direction. The movement of the first and second linkages causes a plane of rotation of a pair of rotors of the tail rotor system to cant relative to a centerline of a mast of the tail rotor system. A tail rotor system is also disclosed.

Abstract: A method of operating a mobile platform includes determining a threshold angle relative to the mobile platform of an imaging device mounted to the mobile platform that avoids obstruction of a field-of-view of the imaging device by one or more components of the mobile platform, and controlling the mobile platform according to the threshold angle.

Abstract: A distributed control system having at least a distributed control module is disclosed. The distributed control module may be configured to determine a fault state associated with a control loop using a built-in test module. The built-in test module may be incorporated into the distributed control module. The fault state may include no faults, a communication fault, a sensor operation fault, or a controllable component fault. The distributed control module may be configured to transmit a closed-loop control command from the distributed control module to a controllable component when the fault state comprises no faults, or transmit an augmented control command from the distributed control module to the controllable component when the fault state comprises a communication fault or a sensor operation fault, or transmit a disconnect control command from the distributed control module to a controllable component when the fault state comprises a controllable component fault.

Abstract: An active flow control system for generating yaw control moments for an aircraft during forward flight. The system includes right and left yaw effectors disposed proximate the right and left wingtips of the wing. A pressurized air system includes a pressurized air source and a plurality of injectors operably associated with the right and left yaw effectors that influence the path of airflow above and below the yaw effectors. Based upon which of the injectors is injecting pressurized air, the right and left yaw effectors generate no yaw control moment, generate a yaw right control moment or generate a yaw left control moment.

Abstract: A land analysis system uses drone-captured images to detect plant health and/or soil moisture levels at a site. For example, the system instructs a drone to fly along a flight path, capture images of the land below, and measure altitude data. The system processes the images using, for example, artificial intelligence, to identify locations at which plant material may be present. The system then further processes the images to identify the plant health of the plant material at the identified locations. The system further uses the altitude data to determine the strata of plants at the identified locations. Optionally, the system can further process the images to identify the soil moisture levels at the identified locations.

Abstract: The invention relates to a method for generating a control variable trajectory for an actuator so as to influence an input variable of a system, wherein a set point is supplied to the output variable of the system of a trajectory planning procedure, which from the set point generates a trajectory of constrained input values for a filter integrator chain and a trajectory of flat desired states, wherein the trajectory of constrained input values and the trajectory of flat desired states are supplied to a flatness-based feedforward control procedure that generates therefrom the control variable trajectory for the actuator, wherein in the trajectory planning procedure so as to generate the trajectory of constrained input values at least one constraint is applied in dependence upon the trajectory of flat desired states.

Abstract: A turbofan gas turbine engine includes low pressure (LP) motor-generator operable in either a generation mode or a drive mode, an high pressure (HP) motor-generator operable in a either a generation mode or a drive mode, and a power control module for selectively operating the LP and HP motor-generators according to operational conditions of the engine.