Health based actuator allocation

1. An aircraft comprising:

a plurality of rotor modules including a first rotor module and a second rotor module, wherein each of the plurality of rotor modules is a fixed rotor module that is attached to the aircraft at a fixed position and a fixed angle; and

a flight computer configured to:

receive a set of one or more desired forces or desired moments associated with the aircraft;

receive first and second health metrics associated with the first rotor module and the second rotor module, respectively;

determine a first command for the first rotor module and a second command for the second rotor module based at least in part on the set of desired forces or desired moments and the first and second health metrics, including by:

attempting to determine the first and second commands in a first manner that: (1) substantially achieves every one of the set of desired forces or desired moments and (2) satisfies one or more health-related considerations based at least in part on the first and second health metrics; and

in the event the first and second commands cannot be determined in the first manner, the first and second commands are determined in a second manner that prioritizes flight control associated with a roll axis and a pitch axis over flight control associated with a yaw axis, wherein the roll axis, the pitch axis, and the yaw axis are mutually orthogonal; and

instruct the plurality of rotor modules to carry out the determined first and second commands.

2. The aircraft of claim 1 , wherein the flight computer is further configured to update the first and second health metrics based on a state of the first and second rotor modules after executing the determined first and second commands.

3. The aircraft of claim 1 , wherein:

determining the first command for the first rotor module includes setting a first amount of thrust associated with the first rotor module to be a predefined value; and

determining the second command for the second rotor module includes setting a second amount of thrust associated with the second rotor module that satisfies the set of desired forces or desired moments, given that the first amount of thrust is set to the predefined value.

4. The aircraft of claim 1 , wherein:

determining the first command for the first rotor module includes setting a first weight based at least in part on the set of desired forces or desired moments, and a second weight based at least in part on the first and second health metrics; and

simultaneously determining (1) a first amount of thrust in the first command associated with the first rotor module and (2) a second amount of thrust in the second command associated with the second rotor module that (a) satisfy the set of desired forces or desired moments to a degree specified by the first weight and (b) satisfy a health consideration to a degree specified by the second weight.

5. The aircraft of claim 1 , wherein:

the plurality of rotor modules includes a plurality of batteries;

the first and second health metrics include a plurality of battery temperatures associated with the plurality of batteries; and

the first and second commands are determined based at least in part on the plurality of battery temperatures.

6. The aircraft of claim 1 , wherein:

determining the first command for the first rotor module includes, in response to determining that the first health metric does not exceed a threshold, setting a first amount of thrust in the first command to be a first predefined value, wherein the first rotor module has an unhealthier health metric compared to the second rotor module; and

determining the second command for the second rotor module includes determining a second amount of thrust in the second command that satisfies the set of desired forces or desired moments given that the first amount of thrust is set to the first predefined value; and

in response to determining that the first health metric exceeds the threshold:

setting the first amount of thrust to be a second and non-zero predefined value; and

determining the second amount of thrust that satisfies the set of desired forces or desired moments, given that the second amount of thrust is set to the first predefined value.

7. The aircraft of claim 1 , wherein determining the first command includes:

setting a first weight associated with taking the set of desired forces or desired moments into account, and setting a second weight associated with taking the first and second health metrics into account, to initial values;

simultaneously determining (1) a first amount of thrust in the first command associated with the first rotor module and (2) a second amount of thrust in a second command associated with the second rotor module that (a) satisfies the set of desired forces or desired moments to a degree specified by the initial value of the first weight and (b) satisfies a health consideration to a degree specified by the initial value of the second weight, wherein the first rotor module has an unhealthier health metric compared to the second rotor module; and

in response to a difference between the first weight and the second weight meeting a threshold, adjusting the first weight and the second weight.

8. The aircraft of claim 1 , wherein determining the first and second commands includes:

decomposing the set of desired forces or desired moments into a plurality of orthogonal components, including: (1) a first component associated with a plane defined by the roll axis and the pitch axis, (2) a second component associated with movement along the yaw axis, and (3) a third component associated with rotation about the yaw axis;

searching for the first and second commands based at least in part on satisfying the first component, the second component, and the first and second health metrics and at least partially satisfying the third component; and

in response to not finding the first and second commands, searching for the first and second commands based at least in part on satisfying the first component and the first and second health metrics and at least partially satisfying the second component and the third component.

9. A method comprising:

receiving a set of one or more desired forces or desired moments associated with an aircraft having a plurality of rotor modules that includes a first rotor module and a second rotor module, wherein each of the plurality of rotor modules is a fixed rotor module that is attached to the aircraft at a fixed position and a fixed angle;

receiving first and second health metrics associated with the first rotor module and the second rotor module, respectively;

determining a first command for the first rotor module and a second command for the second rotor module based at least in part on the set of desired forces or desired moments and the first and second health metrics, including by:

attempting to determine the first and second commands in a first manner that: (1) substantially achieves every one of the set of desired forces or desired moments and (2) satisfies one or more health-related considerations based at least in part on the first and second health metrics; and

in the event the first and second commands cannot be determined in the first manner, the first and second commands are determined in a second manner that prioritizes flight control associated with a roll axis and a pitch axis over flight control associated with a yaw axis, wherein the roll axis, the pitch axis, and the yaw axis are mutually orthogonal; and

instructing the first and second rotor modules to carry out the determined first and second commands.

10. The method of claim 9 , further comprising updating the first and second health metrics based on a state of the first and second rotor modules after executing the determined first and second commands.

11. The method of claim 9 , wherein:

determining the first command for the first rotor module includes setting a first amount of thrust associated with the first rotor module to be a predefined value; and

determining the second command for the second rotor module includes setting a second amount of thrust associated with the second rotor module that satisfies the set of desired forces or desired moments, given that the first amount of thrust is set to the predefined value.

12. The method of claim 9 , wherein:

determining the first command for the first rotor module includes setting a first weight based at least in part on the set of desired forces or desired moments, and a second weight based at least in part on the first and second health metrics; and

simultaneously determining (1) a first amount of thrust in the first command associated with the first rotor module and (2) a second amount of thrust in the second command associated with the second rotor module that (a) satisfy the set of desired forces or desired moments to a degree specified by the first weight and (b) satisfy a health consideration to a degree specified by the second weight.

13. The method of claim 9 , wherein:

the first and second rotor modules includes a plurality of batteries;

the first and second health metrics include a plurality of battery temperatures associated with the plurality of batteries; and

the first and second commands are determined based at least in part on the plurality of battery temperatures.

14. The method of claim 9 , wherein determining the first command includes:

in response to a determination that the first health metric does not exceed a threshold, setting a first amount of thrust in the first command associated with the first rotor module to be a first predefined value; and

in response to determining that the first health metric exceeds the threshold, setting the first amount of thrust to be a second predefined value smaller than the first predefined value.

15. A computer program product, the computer program product being embodied in a non-transitory computer readable storage medium and comprising computer instructions for:

receiving a set of one or more desired forces or desired moments associated with an aircraft having a plurality of rotor modules that includes a first rotor module and a second rotor module, wherein each of the plurality of rotor modules is a fixed rotor module that is attached to the aircraft at a fixed position and a fixed angle;

receiving first and second health metrics associated with the first rotor module and the second rotor module, respectively;

determining a first command for the first rotor module and a second command for the second rotor module based at least in part on the set of desired forces or desired moments and the first and second health metrics, including by:

attempting to determine the first and second commands in a first manner that: (1) substantially achieves every one of the set of desired forces or desired moments and (2) satisfies one or more health-related considerations based at least in part on the first and second health metrics; and

in the event the first and second commands cannot be determined in the first manner, the first and second commands are determined in a second manner that prioritizes flight control associated with a roll axis and a pitch axis over flight control associated with a yaw axis, wherein the roll axis, the pitch axis, and the yaw axis are mutually orthogonal; and

instructing the first and second rotor modules to carry out the determined first and second commands.

16. The computer program product of claim 15 , wherein the computer instructions further include updating the first and second health metrics based on a state of the first and second rotor modules after executing the determined first and second commands.

17. The computer program product of claim 15 , wherein the computer instructions further include:

determining the first command for the first rotor module includes setting a first amount of thrust associated with the first rotor module to be a predefined value; and

determining the second command for the second rotor module includes setting a second amount of thrust associated with the second rotor module that satisfies the set of desired forces or desired moments, given that the first amount of thrust is set to the predefined value.

18. The computer program product of claim 15 , wherein the computer instructions further include:

determining the first command for the first rotor module includes setting a first weight based at least in part on the set of desired forces or desired moments, and a second weight based at least in part on the first and second health metrics; and

simultaneously determining (1) a first amount of thrust in the first command associated with the first rotor module and (2) a second amount of thrust in the second command associated with the second rotor module that (a) satisfy the set of desired forces or desired moments to a degree specified by the first weight and (b) satisfy a health consideration to a degree specified by the second weight.

19. The computer program product of claim 15 , wherein:

the aircraft's first and second rotor modules further include a plurality of batteries;

the first and second health metrics include a plurality of battery temperatures associated with the plurality of batteries; and

the first and second commands are determined based at least in part on the plurality of battery temperatures.

20. The computer program product of claim 15 , wherein the computer instructions further include:

in response to a determination that the first health metric does not exceed a threshold, setting a first amount of thrust in the first command associated with the first rotor module to be a first predefined value; and

in response to determining that the first health metric exceeds the threshold, setting the first amount of thrust to be a second predefined value smaller than the first predefined value.