Objective
Tune the PID gains manually to achieve stable and responsive behavior.
Tuning Process
Step 1: Start with zeros
- Set Ki = 0 and Kd = 0
- Start with small Kp (e.g., Kp = 0.5)
Step 2: Increase Kp
- Gradually increase Kp until the system begins to oscillate
- Note the value where oscillation starts
- Back off slightly (use about 50-70% of that value)
Step 3: Add Kd
- Introduce Kd to reduce oscillation and improve damping
- Start small (e.g., Kd = 0.1 * Kp)
- Increase until oscillations are damped
Step 4: Add Ki
- Add a small Ki to eliminate steady-state error
- Start very small (e.g., Ki = 0.01 * Kp)
- Increase slowly – too much causes overshoot
Key Rules:
- Change ONE gain at a time
- Observe system response after each change
- Record all values and observations
Tuning Table Template
| Kp | Ki | Kd | Observation |
|---|---|---|---|
| 0.5 | 0 | 0 | Slow response, no oscillation |
| 1.0 | 0 | 0 | Faster, slight oscillation |
| 2.0 | 0 | 0 | Strong oscillation |
| 1.5 | 0 | 0 | Good response, some overshoot |
| 1.5 | 0 | 0.2 | Reduced overshoot |
| 1.5 | 0 | 0.3 | Damped well, slight error |
| 1.5 | 0.05 | 0.3 | Error eliminated |
Final values: Kp = 1.5, Ki = 0.05, Kd = 0.3
Common Issues and Solutions
Problem: System oscillates continuously
- Solution: Decrease Kp, increase Kd
Problem: System is sluggish
- Solution: Increase Kp
Problem: Ball settles slightly off-center
- Solution: Increase Ki (but be careful!)
Problem: Erratic, jerky motion
- Solution: Check sensor filtering, decrease Kd
Problem: Massive overshoot
- Solution: Decrease Ki, increase Kd
Key Takeaways
- Start with Kp only (Ki=0, Kd=0)
- Increase Kp until oscillation, then back off
- Add Kd to damp oscillations
- Add small Ki to eliminate steady-state error
- Change one gain at a time
