Hi, i had a same problem with my boat, in auto mode, she swam in zigzags.
Spent quite a lot of time to adjust the parameters (about 10 hours). Not I’d say that with all were worked out, but boat now swims adequately (https://youtu.be/1IywUuRiJfs). Full list parameter’ll attach!
Accurately remember, that first got hooked for parameter STEER2SRV_IMAX, under his increase controller is beginning to more aggressively steer and try to keep course, in further reduced significance this of the parameter, that would governance was more smooth.
The next parameter NAVL1_PERIOD, a low value leads to a low level of response to a control error, a large value causes the course to return aggressively, i stopped at the value of 25 seconds.
And third this PID’s, STEER2SRV_D as me it looked not gives nor what good, only makes the boat more nervous in managing. So I set 0.
STEER2SRV_P large values lead to overshoot, small to understeer, just need to pick up. I was approached 0.4.
And the last output parameter STEER2SRV_I, it greatly affects the zigzags, I set to 0 and then gradually added. While the value is too small the boat can not keep the course as soon as it starts to stay the course, add a little more. Larger values immediately lead to overshot and zigzags.
I use APM 2.6 with firmware rover 3.4.2