Determining and controlling propeller speeds using imaging devices

A method comprising:

• capturing a first image by a first imaging device provided aboard an aerial vehicle at a first time, wherein a first field of view of the first imaging device includes at least a portion of a first propeller coupled to a first propulsion motor;
• capturing a second image by the first imaging device at a second time;
• determining a first angle of a first blade of the first propeller based at least in part on the first image;
• determining a second angle of the first blade of the first propeller based at least in part on the second image;
• determining a difference between the second angle and the first angle;
• determine an elapsed time between the second time and the first time;
• and
• determining a first rotational speed of the first propeller at the second time,
• wherein the first rotational speed of the first propeller at the second time is determined based at least in part on the difference between the second angle and the first angle and the elapsed time between the second time and the first time.

A method comprising:

• capturing a buffer of images by an imaging device aboard an aerial vehicle, wherein each of the images of the buffer is captured at a frame rate, and wherein a field of view of the imaging device includes at least one blade of a rotating propeller;
• executing an algorithm on each of the images of the buffer;
• extracting information regarding an angle of the at least one blade from each of the images of the buffer;
• determining a first rotational speed of the rotating propeller based at least in part on the information regarding the angles of the at least one blade extracted from each of the images of the buffer and the frame rate;
• capturing a first image by the imaging device at a first time;
• updating the buffer of images, wherein updating the buffer of images comprises:
• identifying a second image captured at a second time, wherein the second time precedes the first time;
• removing the second image from the buffer;
• and
• adding the first image to the buffer;
• executing the algorithm on each of the images of the updated buffer;
• extracting information regarding an angle of the at least one blade from each of the images of the updated buffer;
• and
• determining a second rotational speed of the rotating propeller based at least in part on the information regarding the angles of the at least one blade extracted from each of the images of the updated buffer and the frame rate.