Hi Folks:
I'm looking for a solution to a speed limit control tuning problem when my CAV3 is in street-legal mode (750 watts, 20mph).
When I initially set up my CAV3 I found the speed gain parameters that resulted in good behavior as speed approached the limit, then was pegged at the limit. Rapid increase to the limit, followed by minimal overshoot with minimal pumping or oscillation while staying within 0.1 mph of the limit (flat road, no wind).
SLim->MaxSpeed = 20.0 mph
SLim->IntSGain = 200
SLim->PSGain = 0.85 v/mph
SLim->DSGain = 200
ThrO->UpRate = 3.5 V/s
ThrO->DownRate = 40.0 V/s
ThrO->FastRate = 5.0 V/s
ThrO->FastThrsh = 0.0 Amps
PLim->MaxCurrent = 45 Amps
PLim->AGain = 50
PLim-> MaxPower = 750 Watts
PLim->WGain = 50
The system is a crank-drive limited by the CAV3 to 750 watts input (but capable of about 1300 watts input). Speed is limited by the CAV3 to 20 mph. Cruising at 20mph on my bike draws from the battery something in the neighborhood of 200-250 watts.
The remaining problem occurs when my speed exceeds the limit while the motor system is active but idle due to speed limit being exceeded, either from pedaling or from coasting down a hill. As my speed crosses the limit from above to below the speed limit, the overshoot can be as much as 4mph or more (e.g. downhill followed by uphill), the bike slowing to 16mph or less before the motor spools up and attempts to regain 20mph.
I have tried many combinations of increasing or decreasing the gain parameters, and while some combinations tighten this "overshoot from above", in particular increasing IntSGain, I could not find a setting that did not compromise performance when approaching the limit from below or while cruising in steady state.
In general I found that I could change IntSGain and DSGain together, e.g. both to 400 or both to 100 and get similar performance but with slightly more oscillation or over-damped response when approaching the limit from below, but 200 seemed to be the best compromise. Changing IntSGain and DSGain in opposition, i.e. increasing only one parameter or increasing one while decreasing the other resulted in poorer performance. Increasing PSGain had the throttle pumping more while cruising at the limit, and decreasing PSGain introduced low-frequency oscillation about the limit speed while cruising.
Anyone have any suggestions how I might tighten the limit overshoot from above while maintaining my current damping when approaching the limit from below? Thanks.