Wobbly driving

Hi!
I have been now using AOG for couple of days and it would be working good enough for spraying etc., but for potato planting it could be better. It can go straight for 50m and then take 5-20cm curve. Below specs of steering. All-in-one 4 board and fz-g1. Antenna is on top of front axel. RTK fix is always there and I have tested neibours rtk-base. RTK fix age is 0.4-2.0. Always driving just straught AB-lines.

The difference from ab-line is most of the time 0-2cm, sometimes it can be 5cm, according to the numbers in the top of screen. So if you are just looking at the screen, the steering seems to be nice and keeping on the line, but in real life there can be 20cm error. One weird thing is that i think many times the wobbly line appears at the same points. So if you are driving down the field and its wobblying, and then drive up the field, there can appear similar errors in the line at same point of line. Fields are very flat.

CPD 144
Ackerman 116
Max steer angle 30
Proportial gain 15
Max limit 160
Min to move 70
Look ahead 2.0
Speed gain 1.5
Integral 0

Any ideas what could be the reasons? For my self I’m thinking that the steering settings are maybe okay, as the calculated difference from the ab-line is just 0-2cm. But then signal somehow jumps and it makes a curce, sometimes randomly and sometimes there can be a same looking wobble in 6 passes next to each other.

Thank you very much for the help in advance!

I forgot to mention that the steering is done by the phidgets motor. Base is having the ANN-MB antenna and the tractor budget survey. Base is runnign the rtk 2.5.0 with raspi 3b+.

A photo of the antenna location might be worth while posting. Hard to picture but I’m thinking it could be higher up and might be getting blocked by the cab?

Okay, lets try that. Its just over the front axel at the moment, so yeah, tha cab is blocking something. I did read something about antenna position and that it would be good to be in the front when the speed is low, in this case 4-5 kmh.

Maybe your Roll is is wrong and have to be inverted, I have tried that before :smiling_face:

Land is flat?
It could be roll related

If it’s flat you can try 0 as antenna height.

That is not slow. Mine run fine at 2 kmh. I believe slow is below 1 kmh. My antenna is at front edge of cabin on a metal plate. I use ANN MB, both at base and tractor.
I had problem with snaking 10 to 15 cm off line, it helped to add more weight at front wheels, so when AOG demanded steering, it actually happens

I have been thinking about the same, and checked it and it was correct. Thanks for the reply anyway!

Yeah, thats a good idea! But what could be wrong with the roll? Settings are correct and it seems to work when i’m tilting the tractor.

Yeah, you are correct, it’s not that slow. My antenna is straight on the hood of the tractor. And so it’s a bit tilted forward. Is that a problem? Should it be completly in level? I did read somewhere that it shouldn’t be a problem, but i’m not 100% sure.

How does the logic work with demanding steering? As the distance from the ab-line is keeping most of the time under 2cm, I was thinking that aog is thinking it’s driving correctely. So if there wouldn’t be a steering response, the error should raise quite often to 10cm or more?

Hardest part to understand for me is that the errors happens often next to each other. I don’t know what could be the reason. There is not a hill on those points or any trees or anything visible. The ground is quite soft, so maybe the hard ground under the soft layer could be tilted, but maybe not so much that it should be efecting anything.

Antenna on the hood is OK, the antenna itself doesn’t need to be level.

Be sure the inclination shows positive if leaning to the right and you have the right axis (it’s not moving if you go up or down a hill)

Only 2 degree can make 10cm I think.

Next to each other, as in also different direction, then I would guess on roll is not correct ( unless your field is totally flat as a pancake)

Antenna position : Direct on hood and also tilted forward, WILL give you RTK issues, as cabin might cover some of the satellites, and tilting antenna make satellites in low horizon visible, but those low satellites might not be included in base station visible satellites. And you need at least 8 of SAME visible satellites from both Base and Rover , to achieve RTK.
I remember my first year with rtk and antenna on hood (even mounted on level plate) RTK became float on some days, when going down hill because cabin covered more satellites.

I had issues with oscillating steering and dropping the CPD right down cured this.

Okay! The inclination is set the correct way, everything triple checked. I almost wished to find a mistake and to find an easy solution but nope.

Tested and checked everything, all the settings connected to the roll are correct and all the values it gives are correct.

The antenna position could be the problem. I will change it in the next weeks, I will have something else to do for a while and get back to this then.

Does the system check that the base and rover see 8 same satelites? Probably not, or does it? The system have been atleast always saying rtk, not float.

Okay, I would say that my tractor is not oscilating, its appering pretty randomly. Or as I said earlier, randomly, but many times in the same way next to each other. But I could check the steering parameters anyway again, even it’s not probably it.