AOG without wheel angle sensor

I notice the Phidgets motor now comes with a rear motor shaft and $25 encoder option. With this and a BNO085 I would say you could replicate or even outperform a WAS with minimal additional setup.

wasn’t aware that it was without formerly… :joy: But that does not help people with hydraulic actors…

It’s maybe had it for ages! I’ve not used a Phidgets motor but was reading their literature and it mentioned this update. Could have happened years ago I suppose!

Well, if there is a gap in the steering wheel, does not this affect the operation of the encoder?

Sorry, not sure I understand?

I could not explain, I apologize for using google translate. Maybe I can shoot a video and explain it.

I think he is talking about the possible slack in the steering shaft on the older tractors.

1 Like

Ah right. Well yes there could be but that is a repairable situation and slack in any part if the system, like a wheel angle sensor or linkage after the sensor for example, causes havoc in any auto steer.

1 Like

Yes thanks.

Isn’t that called cheating :rofl:

You could do something similar with hydraulics using the estimated flow from the valve?

1 Like

There is a possibility of buying an encoder of a car steering angle sensor.
Something like this:
image

Mounting it to the steering shaft of the tractor…

1 Like

Well yes absolutely! :rofl:. I’m determined to keep playing with this thing, definitely with no encoder to see how good I can get it. Maize drilling, which I’m doing very soon, is a really good test for auto steer as any deviations are instantly visible in the drill roller lines.

It’s a strange system to play with and interesting to see what affects it and what it’s good at. Steer is not quite as smooth unless you filter but this adds lag, which is REALLY bad, but response to field conditions seems faster as it picks up and deals with unwanted rotations really quickly.

Speed related variable parameters may well be the way to go. Slow speed, add more filtering to soften things, higher speed drop the filtering for response time.

The WAS is working again now in the 716 so I can write a small Arduino sketch to directly compare the two systems. That will be useful for testing.

CAT 6 cable doesn’t like oil, I have learned! :joy: :grimacing:

2 Likes

Do you mean Freeplay? Like the distance you have to turn before you get a reaction?

Yes, that is what he means.

Basically what it does at the moment is use angular velocity over speed, attempt to reject rogue values and applies a tiny amount of Kalman filtering (almost none), just to soften it very slightly.

I don’t think WAS less steering has to be any different to WAS steer really. There is no delay in the system. If your steering wheels are rotated to the right you are immediately rotating to the right. Whether you measure the steer wheel angle or actual vehicle rotation, you are indirectly effectively measuring the same thing. The only difference is one is speed dependant, whilst the other isn’t.

I’ve been out maize drilling today and after using the standard setup for most of the day I gave the WAS less a try in the real world. The resulting job was indistinguishable. My code is still simple, crude and not really up to much but the BNO085 is absolutely up to the job as far as I can see.

…and to be clear, I haven’t modified AOG at all. Only the Arduino code.

I did have a video of a U turn but cocked it up because I’d got the U turn parameters wrong for the job I was doing so had to abort filming and rescue my drilling!!

12 Likes

So would this code work for a tracked tractor that does not have wheels to put a WAS on?

1 Like

I can’t see why not really. It just monitors your rotation. Tracked or wheeled the steering has the same effect. Rotation. The speed relationship may or may not be different depending on how the steering system is set up, but that is not a critical parameter given AOG is altering steer indirectly anyway. Via a motor or some sort of steer valve.

The one scenario I do think the WAS less code would need to be more closely coded is direct angle sending CAN BUS steer. But these systems, by their very nature already have a WAS and reading it is not even particularly necessary.

What frequency are you reading the gyro?

25Hz at the moment. I still don’t fully understand the interactions between BNO085 modes. Running the gyro faster than GameRotationVector causes me issues with IMU data availability. So both running at 25Hz, and so is the timed loop.

Where do you put your f9p antennA?

1 Like