Thrust limiter for boom-mounted rotor

1. A system, comprising:

a processor; and

a memory coupled with the processor, wherein the memory is configured to provide the processor with instructions which when executed cause the processor to:

instruct a signal generator to inject an electrical signal at a first test point associated with a first end of a boom;

receive, in response to the injected electrical signal, an electrical signal at a second test point associated with a second end of the boom, wherein a rotor is attached to the boom and the received electrical signal is received while the rotor outputs a thrust;

decide whether to decrease the thrust which is output by the rotor, including by analyzing the received electrical signal; and

in response to deciding to decrease the thrust which is output by the rotor, decrease the thrust which is output by the rotor.

2. The system recited in claim 1 , wherein:

the rotor is attached to the boom at a distal end of the boom;

a fuselage is attached to the boom at a proximal end of the boom;

a float is attached to the boom at an attachment point between the distal end and the proximal end; and

the first test point and the second test point are located between the distal end of the boom and the attachment point.

3. The system recited in claim 1 , wherein:

the rotor is an outer rotor which is attached to the boom at a distal end of the boom;

a fuselage is attached to the boom at a proximal end of the boom;

a float is attached to the boom at an attachment point between the distal end and the proximal end; and

in response to deciding to decrease the thrust which is output by the outer rotor, a second thrust which is output by an inner rotor is increased, wherein the inner rotor is located above the float.

4. The system recited in claim 1 , wherein the received electrical signal is received using an electrical connector that is wrapped around one or more threads of a screw which is inserted into the boom from the interior of the boom without piercing the exterior of the boom.

5. The system recited in claim 1 , wherein the received electrical signal is received using an electrical connector that is held in contact with an inner layer of composite in the boom using an adhesive.

6. The system recited in claim 1 , wherein:

the boom includes a plurality of composite layers;

an electrically conductive layer is an inner layer of composite in the plurality of composite layers; and

the electrically conductive layer includes an exposed portion which extends into a hollow interior of the boom.

7. The system recited in claim 1 , wherein:

the memory is configured to provide the processor with further instructions which when executed cause the processor to perform calibration, including by obtaining a plurality of data samples, wherein each data sample in the plurality of data samples includes an amount of the thrust output by the rotor and a measured amount of a property that is used in analyzing the received electrical signal in order to decide whether to decrease the thrust; and

analyzing the received electrical signal further includes using a threshold amount of the property at which it is decided to decrease the thrust which is output by the rotor, wherein the threshold amount is based at least in part on the plurality of data samples.

8. The system recited in claim 1 , wherein:

the rotor is attached to the boom at the first end of the boom;

a float is attached to the boom at the second end of the boom; and

the first test point is substantially at the first end of the boom while the second test point is substantially at the second end of the boom.

9. The system recited in claim 1 , wherein:

the rotor is attached to the boom at the first end of the boom;

a fuselage is attached to the boom at the second end of the boom; and

the first test point is closer to the first end of the boom while the second test point is closer to the second end of the boom.

10. The system recited in claim 1 , wherein the injected electrical signal is a DC signal.

11. The system recited in claim 1 , wherein the injected electrical signal is an AC signal.

12. The system recited in claim 1 , wherein analyzing the received electrical signal includes comparing a property of the received electrical signal with a baseline signal associated with a signal passing through an unbent boom.

13. A method, comprising:

instructing a signal generator to inject an electrical signal at a first test point associated with a first end of a boom;

receiving, in response to the injected electrical signal, an electrical signal at a second test point associated with a second end of the boom, wherein a rotor is attached to the boom and the received electrical signal is received while the rotor outputs a thrust;

deciding whether to decrease the thrust which is output by the rotor, including by analyzing the received electrical signal; and

in response to deciding to decrease the thrust which is output by the rotor, decreasing the thrust which is output by the rotor.

14. The method recited in claim 13 , wherein:

the rotor is attached to the boom at a distal end of the boom;

a fuselage is attached to the boom at a proximal end of the boom;

a float is attached to the boom at an attachment point between the distal end and the proximal end; and

the first test point and the second test point are located between the distal end of the boom and the attachment point.

15. The method recited in claim 13 , wherein:

the rotor is an outer rotor which is attached to the boom at a distal end of the boom;

a fuselage is attached to the boom at a proximal end of the boom;

a float is attached to the boom at an attachment point between the distal end and the proximal end; and

in response to deciding to decrease the thrust which is output by the outer rotor, a second thrust which is output by an inner rotor is increased, wherein the inner rotor is located above the float.

16. The method recited in claim 13 , wherein the received electrical signal is received using an electrical connector that is wrapped around one or more threads of a screw which is inserted into the boom from the interior of the boom without piercing the exterior of the boom.

17. The method recited in claim 13 , wherein the received electrical signal is received using an electrical connector that is held in contact with an inner layer of composite in the boom using an adhesive.

18. The method recited in claim 13 , wherein:

the boom includes a plurality of composite layers;

an electrically conductive layer is an inner layer of composite in the plurality of composite layers; and

the electrically conductive layer includes an exposed portion which extends into a hollow interior of the boom.

19. The method recited in claim 13 , wherein:

the method further includes performing calibration, including by obtaining a plurality of data samples, wherein each data sample in the plurality of data samples includes an amount of the thrust output by the rotor and a measured amount of a property that is used in analyzing the received electrical signal in order to decide whether to decrease the thrust; and

analyzing the received electrical signal further includes using a threshold amount of the property at which it is decided to decrease the thrust which is output by the rotor, wherein the threshold amount is based at least in part on the plurality of data samples.

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

instructing a signal generator to inject an electrical signal at a first test point associated with a first end of a boom;

receiving, in response to the injected electrical signal, an electrical signal at a second test point associated with a second end of the boom, wherein a rotor is attached to the boom and the received electrical signal is received while the rotor outputs a thrust;

deciding whether to decrease the thrust which is output by the rotor, including by analyzing the received electrical signal; and

in response to deciding to decrease the thrust which is output by the rotor, decreasing the thrust which is output by the rotor.