Selecting propellers for performance and noise shaping

Abstract

Aerial vehicles may be operated with discrete sets of propellers, which may be selected for a specific purpose or on a specific basis. The discrete sets of propellers may be operated separately or in tandem with one another, and at varying power levels. For example, a set of propellers may be selected to optimize the thrust, lift, maneuverability or efficiency of an aerial vehicle based on a position or other operational characteristic of the aerial vehicle, or an environmental condition encountered by the aerial vehicle. At least one of the propellers may be statically or dynamically imbalanced, such that the propeller emits a predetermined sound during operation. A balanced propeller may be specifically modified to cause the aerial vehicle to emit the predetermined sound by changing one or more parameters of the balanced propeller and causing the balanced propeller to be statically or dynamically imbalanced.

What is claimed is: 
     
         1 . A method to deliver a payload from an origin to a destination comprising:
 identifying information regarding the payload;   identifying a transit plan comprising at least one of:
 a location of the origin; 
 a location of the destination; and 
 at least one segment having at least one course, at least one speed and at least one altitude, 
   selecting a first set of propellers based at least in part on the information regarding the payload or the at least one segment of the transit plan; and   selecting a second set of propellers based at least in part on the information regarding the payload or the at least one segment of the transit plan,   wherein each of the first set of propellers is of a first type,   wherein each of the second set of propellers is of a second type, and   wherein the first type is different from the second type.   
     
     
         2 . The method of  claim 1 , wherein the transit plan comprises a first segment from the origin to at least one intervening waypoint and a second segment from the at least one intervening waypoint to the destination, and
 wherein the method further comprises:   coupling each of the first set of propellers to one of a first set of motors;   coupling each of the second set of propellers to one of a second set of motors;   initiating, at a first time, an operation of the first set of motors at a first power level;   causing the aerial vehicle to travel with the payload according to the first segment of the transit plan during the operation of the first set of motors at the first power level;   initiating, at a second time, an operation of the second set of motors at a second power level; and   causing the aerial vehicle to travel with the payload according to the second segment of the transit plan during the operation of the second set of motors at the second power level.   
     
     
         3 . The method of  claim 1 , wherein the transit plan comprises a first segment from the origin to at least one intervening waypoint and a second segment from the at least one intervening waypoint to the destination, and
 wherein the method further comprises:   coupling each of the first set of propellers to one of a first set of motors;   coupling each of the second set of propellers to one of a second set of motors;   initiating, at a first time, a first operation of the first set of motors at a first power level;   initiating, at the first time, a second operation of the second set of motors at a second power level;   causing the aerial vehicle to travel with the payload according to the first segment of the transit plan during the first operation of the first set of motors at the first power level and the second operation of the second set of motors at the second power level;   initiating, at a second time, a third operation of the first set of motors at a third power level; and   initiating, at the second time, a fourth operation of the second set of motors at a fourth power level; and   causing the aerial vehicle to travel with the payload according to the second segment of the transit plan during the third operation of the first set of motors at the first power level and the fourth operation of the second set of motors at the second power level.   
     
     
         4 . The method of  claim 3 , wherein at least one of the first power level, the second power level, the third power level or the fourth power level is zero. 
     
     
         5 . A method for delivering a payload from a first location to a second location by an unmanned aerial vehicle in accordance with a transit plan comprising at least a first segment and a second segment,
 wherein the unmanned aerial vehicle comprises a first motor rotatably coupled to a first propeller and a second motor rotatably coupled to a second propeller,   wherein the first propeller has a first value of an attribute,   wherein the second propeller has a second value of the attribute, and   wherein the method comprises:
 initiating an operation of at least the first motor at a first rotational speed with the unmanned aerial vehicle traveling in accordance with the first segment at a first time; and 
 initiating an operation of at least the second motor at a second rotational speed with the unmanned aerial vehicle traveling in accordance with the second segment at the second time. 
   
     
     
         6 . The method of  claim 5 , wherein the first segment extends between the first location and a third location, and
 wherein the second segment extends between one of the third location or a fourth location and the second location.   
     
     
         7 . The method of  claim 5 , further comprising:
 receiving a request to deliver the payload from the first location to the second location over a network; and   in response to receiving the request, defining the transit plan, wherein defining the transit plan comprises:
 selecting at least one of a first course, a first air speed or a first altitude of the first segment based at least in part on the first value of the attribute; and 
 selecting at least one of a second course, a second air speed or a second altitude of the second segment based at least in part on the second value of the attribute. 
   
     
     
         8 . The method of  claim 5 , further comprising:
 prior to operating at least the first motor and operating at least the second motor, selecting at least one of the first value or the second value based at least in part on at least one of:
 the first location; 
 the second location; 
 a dimension of the payload; 
 a mass of the payload; 
 a first course of the first segment; 
 a first air speed of the first segment; 
 a first altitude of the first segment; 
 a second course of the second segment; 
 a second air speed of the second segment; and 
 a second altitude of the second segment; 
   determining that the first propeller has the first value of the attribute;   determining that the second propeller has the second value of the attribute;   coupling the first propeller to the first motor; and   coupling the second propeller to the second motor.   
     
     
         9 . The method of  claim 5 , wherein initiating the operation of at least the first motor at the first rotational speed with the unmanned aerial vehicle traveling in accordance with the first segment at the first time comprises:
 initiating an operation of at least the second motor at a third rotational speed with the unmanned aerial vehicle traveling in accordance with the first segment,   wherein initiating the operation of at least the second motor at the second rotational speed with the unmanned aerial vehicle traveling in accordance with the second segment at the second time comprises:
 initiating an operation of at least the first motor at a fourth rotational speed with the unmanned aerial vehicle traveling in accordance with the second segment. 
   
     
     
         10 . The method of  claim 9 , wherein at least one of the third rotational speed or the fourth rotational speed is zero. 
     
     
         11 . The method of  claim 5 , further comprising:
 determining an environmental condition in a vicinity of the unmanned aerial vehicle at a third time using at least one sensor, wherein the third time is after the first time and prior to the second time; and   in response to determining the environmental condition in the vicinity of the unmanned aerial vehicle at the third time,
 initiating the operation of at least the second motor at the second rotational speed with the unmanned aerial vehicle traveling in accordance with the second segment at the second time, 
   wherein the environmental condition in the vicinity of the unmanned aerial vehicle at the third time comprises at least one of:   a temperature;   a pressure;   a humidity;   a wind speed;   a wind direction;   a weather event;   a level of cloud coverage;   a level of sunshine; or   a surface condition.   
     
     
         12 . The method of  claim 5 , further comprising:
 determining an operational characteristic of the unmanned aerial vehicle at a third time using at least one sensor, wherein the third time is after the first time and prior to the second time; and   in response to determining the operational characteristic of the unmanned aerial vehicle at the third time,
 initiating the operation of at least the second motor at the second rotational speed with the unmanned aerial vehicle traveling in accordance with the second segment at the second time, 
   wherein the operational characteristic of the unmanned aerial vehicle at the third time comprises at least one of:   an altitude;   a course;   a speed;   a climb rate;   a descent rate;   a turn rate; or   an acceleration.   
     
     
         13 . The method of  claim 5 , further comprising:
 determining information regarding at least one sound emitted by the unmanned aerial vehicle at a third time using at least one sensor, wherein the information regarding the at least one sound comprises at least one of a sound pressure level of the at least one sound or a frequency spectrum of the at least one sound; and   in response to determining information regarding the at least one sound emitted by the unmanned aerial vehicle at the third time,
 initiating the operation of at least the second motor at the second rotational speed with the unmanned aerial vehicle traveling in accordance with the second segment at the second time. 
   
     
     
         14 . The method of  claim 5 , further comprising:
 determining a position of the aerial vehicle at a third time using a position sensor, wherein the third time follows the first time and precedes the second time, and   in response to determining the position of the aerial vehicle at the third time,
 initiating the operation of at least the second motor at the second rotational speed with the unmanned aerial vehicle traveling in accordance with the second segment at the second time. 
   
     
     
         15 . The method of  claim 5 , further comprising:
 prior to the first time,
 determining at least one of a desired course, a desired air speed or a desired altitude of the unmanned aerial vehicle along each of the first segment and the second segment; and 
 selecting a rotational speed to maintain the unmanned aerial vehicle on the at least one of the desired course, the desired air speed or the desired altitude along the first segment, wherein the first rotational speed is the selected rotational speed, and prior to the second time, 
 selecting a rotational speed to maintain the unmanned aerial vehicle on the at least one of the desired course, the desired air speed or the desired altitude along the second segment, wherein the second rotational speed is the selected rotational speed. 
   
     
     
         16 . The method of  claim 5 , wherein the attribute is at least one of:
 a diameter;   a mass;   a number of blades;   a critical speed;   a sound pressure level of a sound emitted at the critical speed;   a frequency spectrum of the sound emitted at the critical speed;   a rake angle of at least one of the blades;   a pitch angle of the at least one of the blades;   a thrust rating;   a lift rating;   a speed rating;   a maneuverability rating; or   a sound rating.   
     
     
         17 . An aerial vehicle comprising:
 a first motor rotatably coupled to a first propeller, wherein the first propeller has a first value of an attribute, and wherein the attribute is at least one of a diameter, a mass, a number of blades, a critical speed, a rake angle of at least one of the blades, a pitch angle of the at least one of the blades, a thrust rating, a lift rating, a speed rating, a maneuverability rating, or a sound rating;   a second motor rotatably coupled to a second propeller, wherein the second propeller has a second value of the attribute; and   at least one computer system in communication with at least the first motor and the second motor,   wherein the at least one computer system is programmed with instructions that, when executed, cause the at least one computer system to at least:
 cause the first motor to rotate the first propeller at a first rotational speed in accordance with a first segment of a transit plan at a first time, wherein the first segment has a first course, a first air speed and a first altitude; and 
 cause the second motor to rotate the second propeller at a second rotational speed in accordance with a second segment of the transit plan at a second time, wherein the second segment has a second course, a second air speed and a second altitude. 
   
     
     
         18 . The aerial vehicle of  claim 17 , wherein the transit plan comprises a plurality of segments extending between an origin and a destination by way of at least one intervening waypoint, and
 wherein the plurality of segments includes the first segment and the second segment.   
     
     
         19 . The aerial vehicle of  claim 17 , further comprising at least one position sensor,
 wherein the instructions, when executed, further cause the at least one computer device to at least:
 determine a position of the aerial vehicle at a third time, wherein the third time is after the first time and prior to the second time; and 
 determine that the position of the aerial vehicle is within a vicinity of the at least one intervening waypoint at the third time, 
   wherein the second motor is caused to rotate the second propeller at the second rotational speed in accordance with the second segment of the transit plan at the second time in response to determining that the position of the aerial vehicle is within the vicinity of the at least one intervening waypoint.   
     
     
         20 . The aerial vehicle of  claim 17 , further comprising at least one acoustic sensor,
 wherein the instructions, when executed, further cause the at least one computer device to at least:
 determine at least one of a sound pressure level or a frequency spectrum of acoustic energy radiated by the aerial vehicle at a third time, wherein the third time is after the first time and prior to the second time; and 
 determine that the at least one of the sound pressure level or the frequency spectrum exceeds a predetermined threshold at the third time, 
   wherein the second motor is caused to rotate the second propeller at the second rotational speed in accordance with the second segment of the transit plan at the second time in response to determining that the at least one of the sound pressure level or the frequency spectrum exceeds the predetermined threshold.