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A novel robust controller is proposed in this study to realize the precise motion control of a cell puncture mechanism (CPM) driven by piezoelectric ceramics (PEAs). The entire dynamic model of CPM is constructed based on the Bouc-Wen model, and the nonlinear part of the dynamic model is optimized locally to facilitate the construction of a robust controller. A model-based, nonlinear robust controller is constructed using time-delay estimation (TDE) and fractional-order nonsingular terminal sliding mode (FONTSM). The proposed controller does not require prior knowledge of unknown disturbances due to its real-time online estimation and compensation of unknown terms by using the TDE technology. The controller also has finite-time convergence and high-precision trajectory tracking capabilities due to FONTSM manifold and fast terminal sliding mode-type reaching law. The stability of the closed-loop system is proved by Lyapunov stability theory. Computer simulation and hardware-in-loop simulation experiments of CPM verify that the proposed controller outperforms traditional terminal sliding mode controllers, such as the integer-order or model-free controller. The proposed controller can also continuously output without chattering and has high control accuracy. Zebrafish embryo is used as a verification target to complete the cell puncture experiment. From the engineering application perspective, the proposed control strategy can be effectively applied in a PEA-driven CPM.

Background: Piezoelectric actuators are widely used in many micro/nano-manipulation applications, but their positioning accuracy are badly affected by their inherent nonlinear hysteresis and creep. To solve this problem, this paper presents a new robust motion-control method for piezoelectric actuators with fast nonsingular terminal sliding mode based on time delay estimation. Method: The proposed controller needs no detailed information about the hysteresis and other nonlinearities of the system, leading to a simple and model-free characteristic due to the time delay estimation and ensures fast convergence and high tracking accuracy thanks to the nonsingular terminal sliding-mode surface and fast terminal sliding mode -type reaching law. A robust exact differentiator is adopted to estimate the velocity and accelerationinformation online, and it overcomes the limitation of only available position measurements. The finite-time convergence and stability of the closed-loop system are proved by using a Lyapunov function. Results: Experimental results show that the proposed control strategy has faster convergence and higher tracking precision compared with a traditional time delay control. Conclusion: The proposed control strategy can be widely used as an effective control method for high-precision motion control of piezoelectric actuators.

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