Rudder calibration not working

[seandepagnier]

Hi there,

Using the web interface on the tinypilot, I calibrated the rudder by moving it to the centre and clicking the centre button. That seemed to work to change the offset and the readout was zero when the rudder was centred.

I then tried to set the port and starboard limits. I moved the rudder 75% of the way to the starboard stop and clicked the starboard range button, then did the same thing for port.

Once you did all three set points, what did you get for offset, scale and non-linearity of the rudder?

I expected that this would prevent the rudder ever hitting the stops.

It should, but it's possible to confuse port and starboard, maybe this caused it.

To be sure while calibrating the rudder, do not engage the motor at all. Using only manual control, move to center, port and starboard (order is not important) pressing the button when the rudder is at each position.

After doing this, move the rudder manually and see if the new calibrated rudder angle is sensible.

Now, you should see the servo flags MIN_RUDDER and MAX_RUDDER appear if you move past these positions, even manually. If this is working then try engaging. If it's not working then the rudder feedback won't stop the rudder and something is miscalibrated or another problem.

When our rudders hit the limit of the hydraulic rams, things go badly wrong. Sometimes the seals in the rams have been damaged by the force. When the pump drives against the stops the hydraulic hoses stretch a bit and the oil gets pressurised. When the pump stops, the stretched hoses bounce back and the oil comes back at very high pressure up the return hose into the reservoir and can even squirt out of the vent hole, making a really horrible oily slippery mess in the saloon! We had this problem for ages with the old pilot because the controller had failed. Although I had a remote which could set the course and turn it on and off, the remote couldn't calibrate the rudder limits. It ended up damaging the seals in the hydraulic rams and got very expensive. It a major reason why I picked pypilot which I can control with any phone or tablet instead of a proprietary autopilot where you're forced to buy the controller from the manufacturer and you're in trouble if it fails after they discontinue supporting it. So anyway.... it's pretty important to me that the rudder limits work properly!

I agree completely. Some hydraulic systems are less damaged than others by this but for all hydraulic systems I recommend rudder feedback. You might even consider wiring end of travel switches using momentary switches or reed switches. This could be in backup to rudder feedback and gets triggered if the rudder feedback doesn't making it even less probably the pump will ever be stressed.

I tried running the autopilot while tied up at the dock with the course set ten degrees off the heading. As expected it kept adding a little more to the rudder angle because the heading wasn't changing. The problem was it didn't stop when it got to the angle at which I had clicked the "starboard range" button and it kept pushing when it hit the stop. Big oily mess in saloon!

Do those port/starboard range buttons actually work? If so then the pilot seems to be ignoring what you set with them.

Thanks!

You are using the web interface to calibrate? I will play with this today and verify, you might have to update tinypilot and/or try the opencpn plugin. Sorry for the trouble, it should be easier.

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I wanted to add that if the MIN_RUDDER and MAX_RUDDER correctly display while manually turning the rudder but fail to stop the controller it's possible that the motor wires are reversed or the calibration was backwards (max starboard means the rudder is to starboard and the boat is turning to starboard)