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The 1245SF props arrived and replacement HK922 servo, both were fitted.

The tricopter is very hard to fly with 1245SF despite lots of time tuning pitch and roll, and level PID parameters. It appears that the propellers are just too much and that control loop stability is hard to achieve at lower motor speed.

So, the 1145 propellers were refitted and fine tuning of the saved PID parameters commenced.

The replacement servo works fine, stable stand alone with and without load, and mechanically smooth through its entire range (no sign of any stiff spots in the gears as in the previous one).

The project is coming to an end, the tail mechanism is an obvious vulnerability in this implementation though it seems to work quite well… more in the final report.

SimonK commit 8873df24: (20140119) with COMP_PWM was loaded on the F-30A ESCs on this F330 quad with Multiwii 2.3 FC, 3S, Hobbyking D2830-11 motors and 8×4.5 SF propellers.

Performed rapid acceleration under WOT, motor idle, recovery, maneuvers and no issues, no hint of sync problems, works fine.

SimonK commit 8873df24: (20140119) with COMP_PWM was loaded on the F-30A ESCs on this X450 quad with APM FC, 3S, Hobbyking D3530-14 motors and 11×4.5 SF propellers.

Performed rapid acceleration under WOT, motor idle, recovery, maneuvers and no issues, no hint of sync problems, works fine.

Tests on the tricopter using a data logger to capture motor speed, current and pack voltage gives an insight into platform operation.

Above, data capture from the tricopter on 3S. The datalogger adds 50g mass.

The plot shows the device hovering at about 5000rpm and 10.8A at 11V. Two WOT ascents were made to check acceleration and motor recovery during closed throttle descents. From idle, it takes about 500ms to accelerate to hover rpm. This test was repeated and the motor reliably restarted every time and the tumbling craft stabilised quickly. A set of 12×4.7SF props has been ordered to try at 3S to more fully load the motors.

Similar tests were conducted also on 4S, and peak current on WOT was 80A on 15.5V for 8500rpm. Operation on 4S would provide sufficient lift to carry a camera payload, but WOT operation exceeds the motor’s continuous current rating.

The tricopter project lumbers on, delayed by faulty parts.

The recommended tail servo, a Hobbyking HK 922 Metal Gear Digital Servo, failed. It had a rough spot at about 70% of its range from new and which became worse quite quickly until the motor had insufficient torque to overcome it.

Continue reading Tricopter build – 20140131