Angular rate sensor

Hi Guys….

I have a boat that I can steer electronically: if A is logic high, it swings to port; if B is high, it goes to starboard. I want to hold a steady heading. Can I use an angular rate sensor (gyroscope) somehow to provide the logic to hold a steady heading (a heading holder)? All servo systems work fine. If this is not the appropriate forum for this problem, please forward. Any help on this topic would be most appreciated…

Many thanks,
Bruce

The heading gyros I am familiar with (used with aircraft autopilots) output a voltage proportional to heading error (from a "bug"). Is yours like that, or does it just have a logic level output? Rate gyros are use for wing leveling (to limit the rate of turn).

Angular rate sensors measure the angular rate, not the angular difference to an absolute heading. So they'll measure the speed you're turning at and not your angular displacement from a reference. THe autopilots use integration with sensor fusion from absolute angle sensors to do that. Using the angular rate alone will stabilize your heading, but won't hold it (it makes it more like you can electronically adjust how fast your boat will swing from one side to the other, like make a bigger boat turn like a smaller or larger boat).

Best to use a compass I think.

dknguyen said:

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Best to use a compass I think.

Click to expand...

Actually, better to use NEMA from a GPS. Use a PIC to parse heading and track, and then compute an appropriate intercept angle, and then steer the boat until heading and track match.

Ah, true. Crossdrift! Almost as fun to deal with as crosswinds!

Thanks for the ideas. My first plan was to use a regular gyro but I found that they were very expensive so I thought I would go cheep and get an angular rate gyro from eBay. Thought I might be able to rig something that would hold a general direction if I play with it for awhile. A magnetic compass would be fine but I don't know how I would get a pick-off for a reference. I very much like the GPS idea. Question: What would a GPS device provide electronically and in what form?

Bruce53 said:

...What would a GPS device provide electronically and in what form?

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Search for Nema 0183..

These guys sell a coupler between GPS and autopilot. Similar products exist for boats.

MikeMl said:

Actually, better to use NEMA from a GPS. Use a PIC to parse heading and track, and then compute an appropriate intercept angle, and then steer the boat until heading and track match.

Click to expand...

Thanks Mike... I am investigating the NMEA part. Complicated but it looks like what I need most..
Will let you know the outcome...
Bruce

Many thanks Mike....