Rotorcraft-assisted system and method for launching and retrieving a fixed-wing aircraft

Abstract

A rotorcraft-assisted launch and retrieval system, and a method for controlling an airborne rotorcraft which includes controlling by a controller a first feedback loop about a longitudinal roll axis of the airborne rotorcraft and controlling by the controller a second feedback loop about a horizontal pitch axis of the airborne rotorcraft, without controlling a vertical yaw axis of the airborne rotorcraft.

What is claimed is: 
     
         1 . A method for detecting a stall of a rotor motor of an unmanned rotorcraft before launch of the rotorcraft, the method comprising:
 (a) for a designated period after sending a signal commanding a rotor motor to operate, receiving, by a controller and from a rotational speed sensor, a measured rotational speed of the rotor motor; and   (b) responsive to the measured rotational speed of the rotor motor being below a threshold rotational speed upon expiration of the designated period, causing the rotor motor to shut down.   
     
     
         2 . The method of  claim 1 , wherein responsive to the measured rotational speed of the rotor motor being below the threshold rotational speed upon expiration of the designated period, causing, by the controller, the rotor motor to shut down. 
     
     
         3 . The method of  claim 1 , wherein responsive to the measured rotational speed of the rotor motor being below the threshold rotational speed upon expiration of the designated period, automatically causing, by the controller, the rotor motor to shut down. 
     
     
         4 . The method of  claim 1 , wherein responsive to the measured rotational speed of the rotor motor being below the threshold rotational speed upon expiration of the designated period, transmitting a signal to the R/C controller. 
     
     
         5 . The method of  claim 4 , wherein the signal transmitted to the R/C controller relates to the measured rotational speed of the rotor motor being below the threshold rotational speed. 
     
     
         6 . The method of  claim 4 , wherein the signal transmitted to the R/C controller relates to shut down of the rotor motor. 
     
     
         7 . The method of  claim 1 , wherein the rotorcraft includes multiple rotor motors, and which includes performing (a) and (b) for each of the rotor motors. 
     
     
         8 . The method of  claim 7 , which includes, responsive to the measured rotational speed of any one of the rotor motors being below the threshold rotational speed upon expiration of the designated period, causing any quantity of the multiple rotor motors to shut down completely or operate at reduced power. 
     
     
         9 . The method of  claim 1 , which includes periodically receiving, by the controller and from the rotational speed sensor, the measured rotational speed of the rotor motor. 
     
     
         10 . The method of  claim 1 , wherein the designated period includes a period of time. 
     
     
         11 . A method for detecting a stall of a rotor motor of an unmanned rotorcraft before launch of the rotorcraft, the method comprising:
 (a) for a designated period after sending a signal commanding a rotor motor to operate, monitoring, by a controller, a back electromotive force generated by the rotor motor; and   (b) responsive to the back electromotive force generated by the rotor motor being below a threshold back electromotive force upon expiration of the designated period, causing the rotor motor to shut down.   
     
     
         12 . The method of  claim 11 , wherein responsive to the back electromotive force generated by the rotor motor being below a threshold back electromotive force rotational speed upon expiration of the designated period, causing, by the controller, the rotor motor to shut down. 
     
     
         13 . The method of  claim 11 , wherein responsive to the back electromotive force generated by the rotor motor being below a threshold back electromotive force rotational speed upon expiration of the designated period, automatically causing, by the controller, the rotor motor to shut down. 
     
     
         14 . The method of  claim 11 , wherein responsive to the back electromotive force generated by the rotor motor being below a threshold back electromotive force rotational speed upon expiration of the designated period, transmitting a signal to the R/C controller. 
     
     
         15 . The method of  claim 14 , wherein the signal transmitted to the R/C controller relates to the measured rotational speed of the rotor motor being below the threshold rotational speed. 
     
     
         16 . The method of  claim 14 , wherein the signal transmitted to the R/C controller relates to shut down of the rotor motor. 
     
     
         17 . The method of  claim 11 , wherein the rotorcraft includes multiple rotor motors, and which includes performing (a) and (b) for each of the rotor motors. 
     
     
         18 . The method of  claim 17 , which includes, responsive to the zero-crossing frequency of back electromotive force generated by any one of the rotor motors being below a threshold back electromotive force rotational speed upon expiration of the designated period, causing any quantity of the multiple rotor motors to shut down or operate at reduced power. 
     
     
         19 . The method of  claim 11 , wherein the designated period includes a period of time. 
     
     
         20 . A method for detecting a stall of a rotor motor of an unmanned rotorcraft before launch of the rotorcraft, the method comprising:
 (a) for a designated period after sending a signal commanding a rotor motor to operate, receiving, by a controller signals indicating rotational speed of the rotor motor; and   (b) responsive to the signals indicating that the rotational speed of the rotor motor is below a threshold rotational speed upon expiration of the designated period, causing the rotor motor to shut down.   
     
     
         21 . The method of  claim 20 , wherein responsive to the signals indicating that the rotational speed of the rotor motor is below the threshold rotational speed upon expiration of the designated period, causing, by the controller, the rotor motor to shut down. 
     
     
         22 . The method of  claim 20 , wherein responsive to the signals indicating that the rotational speed of the rotor motor is below the threshold rotational speed upon expiration of the designated period, automatically causing, by the controller, the rotor motor to shut down. 
     
     
         23 . The method of  claim 20 , wherein responsive to the signals indicating that the rotational speed of the rotor motor is below the threshold rotational speed upon expiration of the designated period, transmitting a signal to the R/C controller. 
     
     
         24 . The method of  claim 23 , wherein the signal transmitted to the R/C controller relates to the rotational speed of the rotor motor being below the threshold rotational speed. 
     
     
         25 . The method of  claim 23 , wherein the signal transmitted to the R/C controller relates to shut down of the rotor motor. 
     
     
         26 . The method of  claim 20 , wherein the rotorcraft includes multiple rotor motors, and which includes performing (a) and (b) for each of the rotor motors. 
     
     
         27 . The method of  claim 26 , which includes, responsive to the signals indicating that the rotational speed of any one of the rotor motors is below the threshold rotational speed upon expiration of the designated period, causing the rotor motors to shut down. 
     
     
         28 . The method of  claim 20 , wherein the designated period includes a period of time.