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Compensation of nonlinearities in a piezoelectric stack actuator with application in intra-cytoplasmic sperm injection

Abstract:

A method for compensation of non-linearities, mainly hysteresis, using augmented linear control for a piezoelectric stack actuator is presented in this paper, with its application in intra-cytoplasmic sperm injection (ICSI). The linear control, realized via a PID control, is enhanced by a regulated chatter signal with variation of duty cycle as well as direction (sign), with constant magnitude and period. The main idea is to augment the PID control signal, which does most of the feedback control, in a low hassle manner by increasing or decreasing the signal via the regulated chatter signal, which does most of the nonlinearities compensation. The variation of duty cycle and direction is updated via an iterative learning technique, taking into consideration the repetitive motion required in the ICSI application. This device is used for assisting oocyte (egg cell) penetration during ICSI process, where the actuator is required to drive a needle, containing a sperm cell, to penetrate an oocyte and then inject the sperm into the oocyte. This technique is able to satisfy the requirements of the process, where a highly-precise motion is mandatory.