I used the code from Sirnoname in the end due to the ease of tuning with the gui (viewtopic.php?f=39&t=1547
). I want to take this opportunity to thank you for your thread though Mat, I learned a great deal from it. I had to lower the max pwm to 80% and remove all power offset . I also ended up with P=2, I and D at 0.
The graph shows good response with little overshoot and no jitter.
I'm at a loss to understand why I needed to go so far from default values. I have geared carefully so I have full travel on my pots. The only reasons I can come up with are perhaps:
- Belt driven pot causes slightly different response versus gears,
- I am only driving the motor over an arc of about 90 - 100 degrees,
- interference (I don't rate this too highly though).
The motors are from VW Caddy vans (Bosch 9390332376). I have isolated the internal brushes from the housing. As you say under load the tuning may be very different so I may find default values are less of an issue. Based on Chris Bergisons experience I don't think the motors will have any issue with the load.
I've added heat sinks to the moto monster boards today and also picked up some 15amp fuses for the motors. I just wish I had more free time to get it finished. I haven't got my head around the math setup yet. I think it will require some hands on tinkering. I have completed a second actuator so will spend some time running them in unison before inserting them in the seat.