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Position overshoot on a servo press can damage tooling and trigger safety faults.
## Why Overshoot Happens
Overshoot occurs when the drive commands deceleration too late or when position loop gain is too high relative to velocity loop bandwidth. Variable load and mechanical compliance in the drive train make this worse on a press.
## Tuning Sequence
### 1. Velocity Loop First
Set KVP to 50% of default, KVI to 20ms. Command a 10% speed step and observe response. Increase KVP until slight oscillation then back off 20%. Target bandwidth: 80-150 Hz for a 200-ton press.
### 2. Position Loop Gain
Start at KPP = 30 rad/s, increase in steps of 5. Target: position error under 0.05mm during forming. Acceptable overshoot at TDC: under 0.1mm.
### 3. Enable Feed-Forward
Velocity feed-forward KFF: start at 80%, increase until following error during acceleration is minimized. With proper feed-forward you can reduce KPP by 30% while achieving better tracking.
### 4. Adjust the Motion Profile
Increase deceleration ramp length approaching BDC. Add a creep phase of 5-10mm at 10% speed before forming contact. Use S-curve profiles instead of trapezoidal.
## Validation
Empty stroke at max SPM: position error under 0.1mm. Full load at 50% SPM: check for increased following error. Run 30 minutes at production speed for thermal test. 100-stroke repeatability test: BDC variation target under 0.02mm.