Edit - This is for the A320
Guys thanks for your replies. I've been working on PID values in the AI.CFG for a while and I've had success on the last few iterations. On my first try, i attempted to get someone from the forums to test these values to be sure i wasn't seeing things lol.
There are several things that can be adjusted to clear some of the handling problems with the AP. I stopped a week or so back because of the updates, I would need to start over each time. That's ok with me if they fix stuff
Heading Control and Roll Control can pretty easily be tuned. The complicating factor for Vertical Control is there are several things that play into it including Auto Throttle, Pitch Control, Vertical Speed Control for Maintaining Airspeed Speed and G-Limiting.
Through testing I've found that the G-Limiting Control appears to have some issues. There must be a PID that is specific to Fly By Wire systems, however there doesn't appear to be a gain adjustment we can get at.
My Current understandings :
Regarding Heading and Roll Control - The Heading PID controller creates a Roll Command Reference and is sent to the Roll PID controller. Reference for the Roll control is in the range of +- 0 to Max Bank Angle. Both the Heading PID and the Roll PID have integral and derivative terms used. Commonly, when you have two PID controllers working in series, having both PID's using Integral terms is not recommended as it can cause instability (Fighting each other) like wagging left and right which in this case is one of the problems the A320 and other planes exhibit. There are times where this has been used but the inner most PID must have a faster integration gain and also likely to have a faster loop rate where in this case all these loops run at the same rate. Additionally, the Derivative term is only used when there is good reason and only complicates control problems. It is indeed a good method to contain overshoot, but unless its implemented properly it can hurt things.
What i have done with this particular set of PID's is to remove the Integral Term and the Derivative Term from the Heading Controller. The PID only responds to Heading Error and Multiplying it by Gain. I have made Gain only adjustments to this PID. The Gain will do two things, It will certainly make it more responsive and potentially nervous depending on magnitude of gain, but it will also determine how long the bank angle will stay at Max Bank Angle during a turn. It will also cause the heading to be achieved sooner as a higher bank angle will be commanded for a given amount of heading error.
I've been asked how i would ever expect the heading to be achieved if there is no Integral Term in the Heading PID. The reasoning is there is integral in the Roll control which is the prime mover for heading control. If i only have 1 deg of error in heading, it will still multiply that by gain and send it to the Roll control as a Bank angle and it will do what it needs to do to remove any error in its loop with Gain+Integral+Derivative until the Heading PID is satisfied and ends up with a 0 deg Reference command to the Roll PID.
Regarding Vertical Control - I'm still messing with this, however there are multiple interactions here. There is defiantly a issue in this section that cant be properly tuned until it is fixed. I'll keep playing.
In the end now that the new patch is here I'll mess around with gains and do testing on the PID's. I'll post here with what i think may be satisfactory gains.