High-Accuracy Digital-to-Analog Actuators Using Load Springs Compensating Fabrication Errors

We present a high-accuracy digital-to-analog (DA) actuator using a linear load spring capable of compensating the output displacement errors caused by fabrication errors. The load spring is designed to modify the modulation line slope in the presence of fabrication errors, thus reducing the output displacement errors. We compare three prototypes including the uncompensated design, the compensated design at the fabrication error of delta=0, and the compensated design in the fabrication error range of -0.3 mum<delta< 0, respectively. The two different compensated linear DA actuators generate the output displacement errors of -0.20plusmn0.23 mum and -0.13plusmn0.18 mum, respectively, thus reducing their output errors by 64.3% and 76.8% of the errors, i.e., 0.56plusmn0.20 mum, produced by the conventional uncompensated linear DA actuator. The dynamic characteristics of the compensated linear DA actuators show the response time below 1.5 ms, the resonant frequency of 3.7 kHz, and the lifetime of 107 cycles. Consequently, we experimentally verify the fabrication error compensation function of the compensated linear DA actuators for applications to high-accuracy actuators insensitive to fabrication errors.