Ursviken Pullmax Optima 130 press brake retrofit with 4 axis backgage

Finally, got to test drive the pullmax_optima component with closed loop PID, only p set to 5. Left and right side sync nicely, but with loud groaning noise. This machine runs smooth and quiet when I run it open loop. I think what I'm seeing in halscope is a combination of untuned PID and non-linear hydraulics.

chan. 1 pwmgen.04.value = controls left ram servo valve (driven by j3.vel_pid.output)
chan. 2 pwmgen.05.value = controls right ram servo valve (driven by j4.vel_pid.output)
chan. 3 pwmgen.06.value = controls tonnage proportional valve; ultimately comes from a slider on my test gui.
chan. 4,5,6,9 are the discrete spool valve coil power outputs (cr-200 to cr-203)
chan. 7 j3-motor-pos-cmd ultimately comes from a slider on my test gui. This is the input to the pos_pid.command
chan. 8 j3-motor-vel-cmd is signal connecting pos_pid.output => vel_pid.command

I was hoping velocity PID will allow me to skip the low frequency dither these valves like; but now I'm thinking my lack of that dither is what is fighting my PID. I will try lowering the p value first in case 5 is actually too high, next step is adding that low frequency dither, probably via siggen or a custom component.

Finally got back to this project last week. So it seems the big difficulty is the unique hydraulic configuration. The left and right side (axis Y1 and Y2) are servo valves tee'd from the pump. The flow divider is fully emulated electronically. In this case directly in LinuxCNC hal. I seem to have improved control at this point. More testing...