Method of controlling an activation system, emergency control system, and aircraft equipped with such system

1. A method of controlling an overly determined actuator system, said actuator system having a first number of actuators (α i ), said first number of actuators is greater than a second number of said actuators needed to perform a predetermined physical task with said actuator system, said actuators comprise propulsion units that form part of a multi-actuator aerial vehicle, MAV, which is an electrically powered VTOL aircraft for transporting at least one of loads or passengers, the method comprising:

automatically controlling said first number of actuators (α i ) with a control unit (CU) for jointly performing said predetermined physical task;

repeatedly checking a functional state of said first number of actuators (α i ) in order to detect an actuator failure of any one of said first number of actuators (α i );

in case of any detected actuator failure, generating at least one emergency signal (EM) representative of an adapted physical task to be performed by a remaining number of said actuators (α i ), wherein said emergency signal (EM) is generated based on dynamics and kinematics of the actuator system, on known physical capacities at least of the remaining number of said actuators (α i ), and optionally on a computational performance model of the actuator system;

wherein said adapted physical task comprises activating each of said remaining actuators (α i ) below a predetermined threshold of maximum physical load on any respective one of the actuators (α i ) and activating an ensemble of said remaining actuators (α i ) in a way to prevent further damage to the actuator system; and

said emergency signal (EM) is applied to a motion planning device (MP), and said motion planning device (MP) uses the emergency signal (EM) to adapt a pre-planned flight trajectory of the MAV and to determine at least one possible adapted flight trajectory that is modified from the pre-planned flight trajectory.

2. The method of claim 1 , wherein the repeatedly checking of the functional state of the said first number of actuators is performed by a failure detection algorithm which accepts at least one of the following inputs:

an actuator health status from each said actuator (α i );

commanded actuator values computed by the control unit (CU);

output of an external disturbance observer;

computed actuator commands;

known system parameters, particular mass, moment of inertia, system geometry, which may be subject to uncertainties;

available measurements/estimates of the system state, e.g., attitude, altitude, rotational velocities; and

translational velocities;

wherein said algorithm combines at least a plurality of said inputs with a probability value between 0 and 1 for each said actuator (α i ), where 0 indicates that the individual actuator has failed with 0% probability and 1 indicates that the individual actuator has failed with 100% probability, and wherein said algorithm detects a failure for a particular one of the actuators (α i ) if said probability value for said particular one of said actuators (α i ) is higher than a heuristically set value.

3. The method of claim 2 , wherein at least one of the method steps is carried out by the algorithm (ECS/A) which is installed on and performed by at least one of said control unit (CU) or a dedicated emergency control unit.

4. The method of claim 1 , further comprising translating said emergency signal (EM) to a control signal that is adapted to be communicated to the human pilot or is communicated to an auto-pilot of the actuator system, which uses the control unit (CU) in order to control the actuator system, said control signal being adapted to activate the remaining actuators (α i ) to perform said adapted physical task.

5. The method of claim 1 , wherein the emergency signal (EM) is adapted to trigger an emergency procedure for saving the actuator system.

6. The method of claim 1 , wherein said adapted physical task comprises shutting down the actuator system.

7. The method of claim 1 , wherein said actuator functional state is repeatedly communicated by the actuators (α i ) to the control unit (CU) or to a dedicated emergency control unit.

8. A method of controlling an overly determined actuator system, said actuator system having a first number of actuators (a), said first number of actuators is greater than a second number of said actuators needed to perform a predetermined physical task with said actuator system, the method comprising:

automatically controlling said first number of actuators (α i ) with a control unit (CU) for jointly performing said predetermined physical task;

repeatedly checking a functional state of said first number of actuators (α i ) in order to detect an actuator failure of any one of said first number of actuators (α i );

in case of any detected actuator failure, generating at least one emergency signal (EM) representative of an adapted physical task to be performed by a remaining number of said actuators (α i ), wherein said emergency signal (EM) is generated based on dynamics and kinematics of the actuator system, on known physical capacities at least of the remaining number of said actuators (α i ), and optionally on a computational performance model of the actuator system; and

translating said emergency signal (EM) to a communication signal and that is adapted for communication to a human operator of the actuator system, said communication signal being indicative of an operator action required to perform said adapted physical task;

wherein said adapted physical task comprises activating each of said remaining actuators (α i ) below a predetermined threshold of maximum physical load on any respective one of the actuators (α i ) and activating an ensemble of said remaining actuators (α i ) in a way to prevent further damage to the actuator system.

9. A method of controlling an overly determined actuator system, said actuator system having a first number of actuators (α i ), said first number of actuators is greater than a second number of said actuators needed to perform a predetermined physical task with said actuator system, the method comprising:

automatically controlling said first number of actuators (α i ) with a control unit (CU) for jointly performing said predetermined physical task;

repeatedly checking a functional state of said first number of actuators (α i ) in order to detect an actuator failure of any one of said first number of actuators (α i );

in case of any detected actuator failure, generating at least one emergency signal (EM) representative of an adapted physical task to be performed by a remaining number of said actuators (α i ), wherein said emergency signal (EM) is generated based on dynamics and kinematics of the actuator system, on known physical capacities at least of the remaining number of said actuators (α i ), and optionally on a computational performance model of the actuator system;

wherein said adapted physical task comprises activating each of said remaining actuators (α i ) below a predetermined threshold of maximum physical load on any respective one of the actuators (α i ) and activating an ensemble of said remaining actuators (α i ) in a way to prevent further damage to the actuator system;

wherein said emergency signal (EM) is applied to a motion planning device (MP), and said motion planning device (MP) uses the emergency signal (EM) to adapt a pre-planned flight trajectory of a multi-actuator aerial vehicle (MAV) and to determine an adapted flight trajectory that is modified from the pre-planned flight trajectory; and

the motion planning device (MP) automatically suggests an overrule command and provides said overrule command to a trajectory tracking unit (TT), which enables the MAV to at least locally deviate from said pre-planned flight trajectory.

10. The method of claim 9 , wherein locally deviating from a pre-planned flight trajectory comprises:

implementing a potential field covering at least a respective local area; and

using at least one of the motion planning device (MP) or the trajectory tracking unit (TT) to at least locally recalculate the pre-planned flight trajectory based on said potential field.

11. The method of claim 10 , wherein the motion planning device (MP) sets a geometrical or geographical extent of said potential field; and

the trajectory tracking unit (TT) decides whether or not local deviation is permitted.

12. An emergency control system for controlling an overly determined actuator system, said system having a first number of actuators (α i ) and said first number of actuators is greater than a second number of the actuators needed to perform a predetermined physical task with said actuator system, the emergency control system comprising:

a control unit (CU) that automatically controls said first number of actuators (α i ) for jointly performing said predetermined physical task;

a function for repeatedly checking a functional state of said first number of actuators (α i ) in order to detect an actuator failure of any one of said first number of actuators (α i );

a emergency signal device or unit (ECS/A) that, in case of any detected actuator failure, is configured to generate at least one emergency signal (EM) representative of an adapted physical task to be performed by a remaining number of said actuators (α i ), said emergency signal (EM) is generated based on kinematics of the overall actuator system, on known physical capacities at least of the remaining actuators (α i ), and optionally on a computational performance model of the overall actuator system;

wherein said adapted physical task comprises activating each of said remaining actuators (α i ) below a predetermined threshold of maximum physical load on a respective one of the actuators (α i ) and activating an ensemble of the remaining actuators (α i ) in a way to prevent further damage to the actuator system;

wherein the system is configured for use with a multi-actuator aerial vehicle, MAV, comprising an electrically powered VTOL aircraft for transporting at least one of loads or passengers, said actuators (α i ) comprise propulsion units which form part of said MAV, and the control unit comprises a flight control unit; and

the control unit is configured to apply said emergency signal (EM) to a motion planning device (MP), and said motion planning device (MP) uses the emergency signal (EM) to adapt a pre-planned flight trajectory of the MAV and to determine at least one possible adapted flight trajectory that is modified from the pre-planned flight trajectory.

13. An aircraft comprising a multi-actuator aerial vehicle, MAV, formed as an electrically powered VTOL aircraft for transporting at least one of loads or passengers, said aircraft comprising:

an overly determined actuator system having a first number of actuators (α i ) and said first number of actuators is greater than a second number of said actuators needed to perform a predetermined physical task with said actuator system, said actuators (α i ) comprising propulsion units; and

the emergency control system according to claim 12 .

14. The aircraft of claim 13 , wherein the propulsion units comprise rotors/propellers (R) or motor-propeller units.