Precise EWOD top plate positioning using inverse Preisach model based hysteresis compensation

The displacement of an intelligent PZT (piezoelectric materials based on modified lead zirconate titanate) controlled EWOD (electrowetting on dielectric) top plate is modeled by inverse Preisach hysteresis algorithm. First, the PZT deflection model is created from an experimental displacement dataset. The real time output is predicted based on the previously stored weighting functions. Upon the desired output and the current input, the input voltage is compensated by a feedforward voltage which is derived from the model using a closest match method. The feedforward process and the model are stored in a PC. A portable high voltage DAC (digital-to-analog converter) is used to drive the PZT cantilever structure. The worst-case DNL of the high voltage DAC is 0.8125 mV. The tracking errors of a 0.067 Hz triangle wave input are less than 5 μm. Results show the inverse Preisach model is a good candidate for precise EWOD top plate displacement hysteresis compensation.