PingvCurr.spt is used to measure the autofocus characteristics for various actuator currents.

The actuator lens tube is mounted on a spring. When the actuator current is changed, the lens tube will move and oscillate about its final rest position. These oscillations will decay until the lens tube comes to rest. This movement is shown in Example Graph 1.

The actuator movement can be described with three parameters:

• Resonant frequency: This is the frequency (how many cycles per second) of the oscillations
• Damping ratio: This is a measure of how quickly the oscillations decay. The higher the damping ratio, the sooner the oscillations will decay.
• DC Gain: This ratio of the change in position over the change in current. Due to the use of the autofocus LUT, the currents will not be in true Amps

Ideally, the PingvCurr graph file will look like Example Graph 2. The resonant frequency should start around 190-230Hz, depending on the dpi of the head, and will drop to around 120-160Hz around 1A, and then have another minor bump. The DC gain should be between 0.9 and 1.1. The damping ratio should be less than 0.08 for all currents. The damping ratio at lower currents will tend to be lower than at higher currents.

Organization of PingvCurr_data.txt:

The PingvCurr_data.txt file contains twelve columns:

• The start current of the step
• The final current of the step
• The resonant frequency
• The DC gain
• The damping ratio
• The controller gain K1 for a 100Hz closed loop bandwidth at this position
• The controller gain K2 for a 100Hz closed loop bandwidth at this position
• The controller gain Ki for a 100Hz closed loop bandwidth at this position
• The estimator gain A1 for a 100Hz closed loop bandwidth at this position
• The estimator gain A2 for a 100Hz closed loop bandwidth at this position
• The estimator gain A3 for a 100Hz closed loop bandwidth at this position
• The estimator gain A4 for a 100Hz closed loop bandwidth at this position