Glory Regained wrote:
The body is soldered with steel frame and aluminium foils and it is
3Kg
together
with controller board, motor & hydrofoils, battery etc. My objective
is
using four
mini-hydrofoils to raise the boat out of water and achieve a speed of
32kmh.
I
have accurate & independent control over each bydrofoils. The
dimension of
my
ship is L30cm-W10cm-H10cm. My hydrofoil assemblies and turbine extend
15cm
below the body.
During the testing, it flipped frequently whenever it reached 10kmh.
I think
I need
a sensor to tell my microprocessor that the angle the body forms with
flat
water
surface, probably with an accuracy of up to 1 degree and a response
time of
1ms.
Anybody can give a clue? The big contest is 4 weeks away.
That won't help, even as a cut-off, unless you use the signal in a
stable control loop. It sounds that 10km/hr excites an unstable pitch
mode. Surface foils tend to generate several such unstable modes. A
partical quick fix is to compensate for that pitch by having the boat
on a 10-25 deg angle when the foils are on the surface. Not more,
because you can flip the other way depending on air dynamics. Try
distributing some weights in the boat. This is a nasty non-linear
dynamics problem. Submerged foils resolve the flipping issue but need
complicated controls. Surface foils are passively controlled up to
certain speeds and wave amplitude. After that you either flip or become
a sitting duck.
Also, I would recommend avoiding alignment of front and back foils in
each side. Make you front foils extend further than the back foils.
That will assure all foils have the same dynamics.
Good luck.
Mike
.
