not Quite

esky · 03-09-2006, 03:06 AM

Trying to make a device to carry out line in a certain direction being controlled via direction ie NW or NNW compas style, was thinking go to the beach take reading of where you wanted the device head then enter direction into gps and let it go, trouble is in New Zealand this is on the WEST Coast and if you have seen Zena or Hercules the west coast can be wild!
i figured that if the device was remote control steering then the average operater would be to slow or over compensate for the rip/swell/wave break so was thinking/asking has anyone set a gps to actually control the direction of a "vechile" and how would you go about it.
setups have been tried before but have failed they usually entailed a direction ruder to be fixed in place before heading out but this cannt take in sideway's or any rip for that matter

any sugeestions / comments would be good

cheers esky

wi77iam · 03-09-2006, 11:57 AM

Could you re-state that in English? Or try again when your morning double espresso has worn off.

esky · 03-12-2006, 02:16 AM

" Device" = battery powered float that is used to carry out fishing line from the beach instead of using a kite or surfcasting
just trying to get it's direction controlled via gps

pshadwick · 03-13-2006, 10:02 AM

Wow... I'm a Kiwi and I couldnt understand a word of that post.

esky · 03-14-2006, 03:25 AM

OK back to basic's
its kinda like an auto pilot, the gps controlls the direction of a moving vechile and here's a picture

MatrixPC · 03-14-2006, 11:28 AM

So you want to know how to control a torpedo by using GPS?

esky · 03-14-2006, 03:18 PM

Quote: Originally Posted by MatrixPC

So you want to know how to control a torpedo by using GPS?

Now that i remember my first language being english

YES

b8bboi · 03-14-2006, 03:22 PM

Quote: Originally Posted by esky

Trying to make a device to carry out line in a certain direction being controlled via direction ie NW or NNW compas style, was thinking go to the beach take reading of where you wanted the device head then enter direction into gps and let it go, trouble is in New Zealand this is on the WEST Coast and if you have seen Zena or Hercules the west coast can be wild!
i figured that if the device was remote control steering then the average operater would be to slow or over compensate for the rip/swell/wave break so was thinking/asking has anyone set a gps to actually control the direction of a "vechile" and how would you go about it.
setups have been tried before but have failed they usually entailed a direction ruder to be fixed in place before heading out but this cannt take in sideway's or any rip for that matter

any sugeestions / comments would be good

cheers esky

Did this post come straight out of Babel Fish?

Scouse Monkey · 03-14-2006, 03:45 PM

tis ok, i can understand you! damn yanks who cant understnad real english!

GPs is not quick enough for what you want. You need an inertial system using solid state accerlometers and you are gonna need a full 6 D.O.F (degrees of freedom) - ie X,Y,Z translation and rotation about the X,Y,Z axes.

Lets take X as the forward direction, Y as up and down and Z as sideways. Then X rotation (X_theta) is roll, Y_theta is yaw and Z_theta is pitch.

You would set the direction using GPS and then have the accelerometers zero on this heading. Then when any deviation is detected there is a negative feedback loop that makes the control surface react. OYu need this to be rate controlled so large/quick deflection are met with a large returning force and small deviations are not over corrected.

You need to take into consideration some damping both in the control system (think of lag etc) and as you are in water and you dont want the system to repsond too quick or you will overcorrect or be forever trying to overcorrect - also need to look at the repsonse time for this - mayeb add a delay.

Then you need to look at actuator saturation..ie how fast can your servos move under load. it is no good if the control system tells the servo go one way wehn it is still trying to go the other and simply cant keep up with hwhat you want.

It is not an easy task as what i have explained is just a taster and you may have more luck with training a hamster to drive the thing!

One other option is build in natural stability. Ie use hydrofoils that when the flow direction changes off the straigh ahead then they cause a moment. this is how aircraft horizontal tails work. ie if the plane pitches up then the tail sees a change in incidence and loses downwards lift and this the planes tail raises up. of the plane goes nose down the tail has more incidence and creates more downwards lift and this brings the nose back up (yes a plane actually has +ve lift on the main wing and -ve lift on the tail).

you can build this type of system into anything and this woudl then allow you to get away with a simple GPS direction corection system that can operate much slower and just be used for general course correction.