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Thursday, June 28, 2012

Letting it hover...

While the building phase can be an enjoyable experience, grabbing the sticks, putting the chopper on the ground, and gently increasing the thrust until that custom build apparatus starts to appear light on its stands is where the real fun begins. Would we ignore the noise of the struggling motors, and this styrofoam-shielded quadcopter would seem like a magical object for which gravity would be opening an exception everytime we wanted to. There is no magic, just technology, but still there is a sense of victory in tricking gravity in a brute force manner. Not in a magnificent scale as Howard Hughes H-4 Hercules, or lighter than air as Bartolomeu de Gusmão's flying bird, but still admirable for mimicking birds in the size and ability to fly (in a cumbersome way however), and for hovering like few of these animals can.

Here is the inspiring video, that hopefully shall represent the first of many flight ordeals:

In spite of the 1.26 Kg of All Up Weight (AUW), at about 40 % throttle the propellers would start to support the entire weight of the quadcopter. Some rudder trimming to the left was required, as it slowly started to yaw to the right initially. Minor corrections on the elevator and aileron trims were also applied
to ensure proper stability in the neutral position of the sticks. No gyro gain adjustments were performed so far, as at least for hovering the settings seemed ok (about 50% for yaw, pitch and roll). An outdoor test may allow for a better assessment of this.

The styrofoam strucuture weights approximately 130 grams. An improvement of this will probably be attempted by cutting some styrofoam in some structurally insensitive areas. Maybe a 15-20% weight reduction is feasible.

For outdoor flying, the structure is not so important (unless flying close to people and important objects is necessary), so that it may be detached, resulting in a significant weight reduction, and consequent increase in flight time. Probably stability is improved as well, because of the decrease in angular inertia around the rotor areas, resulting in lower motor output to correct attitude errors, and faster response to increase in motor power for correcting these errors.

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