What happened to the boat and the lake ?Not really much, there seems to be a kind of stagnation in the air...
I tried the radio-control on the boat several times, but found out, that this is not the solution to the swimming recovery problem. Several reasons for that:
The first try ended up in wading through the mud and recovering the boat, that managed to get stuck in some roots on the shoreline. I tried to get the boat managed by RC, but the diameter of the turn was too big to get it right back to the point, where i have started.
Why that?
The turn diameters were OK, when running in AP-mode.
Seems, that the RC outputs servo pulses only for +- 45 degrees.
The AP can output pulses for up to +- 90 degrees.
To cope for that, i modified the rudder-horn steering to its largest extends so that there was more "angle".
With this modification, the AP still worked and the RC-control of the boat was also possible.
Second, the ESC i am using, can only drive the motor in one direction. So, when the boat gets stuck on the shoreline, there is now way to get the boat shifted into reverse.
The only way to rescue the boat is: still swimming.
Third, adding more technology onto the boat´s electronics makes it more prone to errors than before.
For that reasons (and for the thrill) i decided to dismantle all the RC stuff and turned back to the "old" configuration.
I kept the RC equipment to start some crash-flying experiments with an EASYSTAR, but this is another story...
Some days later, i went back to the lake to do some "long-leg" measurements, to see, how the control loop
behaves on a long trip. (a 400m straight line path and a 180° turn).
The first run was OK.
On the second one, the boat made some weird turns on the opposite end of the lake and crashed into the shoreline, mowing away some reed, until the propeller gets stopped by something hard.
Swimming...
Walking back on the shoreline with the boat in my arms, giving comments to the russian fisherman....
What happened?
It was a windy day and maybe the boat had trouble, moving against the wind, the speed went down and the GPS did not output valid direction data.
This must have been the reason!
I tried again some days later, when it was absolutely still air.
The first run was OK.
The second one...
see above.
This time, the propeller milled away some tupperware housing and the servo had shifted the windmill assembly into an extreme 90° position.
Post mortem analysis of the GPS and control loop outputs showed, that the AP behaved absolutely correct.
hmmm...
thinking...
Bingo!
The following picture shows, what happened:
The Rudder Horn steering was still at its extreme positions, that i had used for the RC experiments. And, in some situations (e.g. a full 180° turn) it could happen that the steering rod acted as a "piston" as we have in internal combustion engines. The assembly kept stuck in a 90°+ position.
So it was no wonder, that the boat made some weird turns.
Next, i reduced the angle of the steering and introduced a "push-pull" assembly with two steering rods.
That was it!
Absolutely perfect straight line behaviour. No stalls, no further swimming.
The world was perfect again...
Not absolutely perfect.
The mounting position of the sonar transducer was still something that should be enhanced. Too much drag, too much irritation.
So i mounted the transducer into the right hull.
I expected a faster boat after that modification, but the inrease of speed was neglegtible compared to the the "old" configuration. Anyway, the boat glides much smoother trough the water and there is no more chance for water plants to hook into the transducer.
In the next episode:
A new lake and new Dr Depth pictures....
