It may be ugly


#1

In an effort to get my unit neutral in water I added a wood platform with holes every .5 inch screwed to the top where the name is. I made mine on a laser cutter but it could easily be made by hand. This was so I could easily attach things to the top. I tried the ping-pong balls with netting but they are hard to attach. I then added a small tire tube. Now I can adjust the air in the tube to make the unit neutral. I also down loaded free software called "FreeScreenVideoRecorder.exe" to capture video while I drove the unit around. The software works great! Google the name and you will find it. I drove the unit around tonight in my test tank and captured video for the first time. The video doesn't look like much because my test tank is white plastic.

My main problem to really use the unit in our pond is I need to be able to drive the thurster motors slower. The OpenROV really moves quickly and the battery voltage drops, knocking the unit off line. Can we get some firmware to limit the motor power? Even with the X'Box USB controller it is hard to go slow enough. I could make it 4 or 5 min. by being careful. The vertical thruster I can run at full power with no problem, but I still have the plastic impeller on it. I have the brass props on the other 2 motors.

1836-floatplate.jpg (100 KB) 1837-openrovtsttank3.jpg (160 KB) 1838-openrovtsttank2.jpg (159 KB)

#2

We were talking about this exact issue all day. This is top priority for firmware.


#3

it seems like we can just set a limit in the arduino motor code. We can always reprogram. At least in the near term.


#4

Implement "Gain" functions that can be selected via the GUI - "Low", "Medium", and "High". That would provide some buffer to the joystick controls. Less sensitive in low. Medium being a nominal operating range, and high for a heavy current condition. Unfortunately I am full of ideas but don't have the time to work on it.


#5

I think there's a lot to be done on optimizing motor speed (seems to be way too high for a submerged propeller) as well as on the shape of the blades (I assume that John's ship propellers are more efficient than the V-15 impeller design). If I had the time, I would measure the drag as a function of motor speed and propeller shape and use the results to optimize the motor speed mapping in the Arduino code. Anyone who can do this?

Thera are a lot of cheap rc ship propellers out there that would fit... and using a plastic propeller instead of the (heavy) brass models would make it a lot easier to make the ROV neutrally bouyant...

Finally, lower motor speeds will keep the batteries from draining too fast.


#6

Maybe we could add a master throttle to set maximum speed. Then the other controls could remain as they are now, and would just be scaled by the master throttle.