研究目的
To design and implement a two-degrees-of-freedom PI2D controller for precise nanopositioning that overcomes limitations of existing control schemes, particularly in handling hardware-induced constant time delays and achieving zero-error tracking for triangular trajectories.
研究成果
The proposed 2DOF-PI2D controller effectively compensates for hardware-induced delays and provides superior tracking performance for triangular and arbitrary trajectories compared to traditional schemes like IRC, PPF, and PVPF. It enables zero-error tracking on slopes of triangular signals, potentially doubling scanning rates in applications like AFM. Future work should focus on optimal pole placement for further enhancements.
研究不足
The controller design primarily considers the first resonant mode, neglecting higher modes which may affect performance. The delay compensation is sensitive to accurate identification of delay parameters. The method may not be directly applicable to systems with significant nonlinearities beyond the modeled range.
1:Experimental Design and Method Selection:
The study uses a control scheme based on the 2DOF-PID structure, modified to include a double integral action (2DOF-PI2D). The design involves pole placement techniques, considering both cases with and without system delay. Stability analysis is performed using Padé approximations for delay.
2:Sample Selection and Data Sources:
A flexure-based XY nanopositioner driven by piezoelectric actuators is used. Data is collected from frequency response functions (FRFs) using small-amplitude sinusoidal chirp signals.
3:List of Experimental Equipment and Materials:
PiezoDrive 200V linear amplifiers, Microsense 4810 capacitive sensor with 2805 measurement probe, National Instruments PCI-6621 data acquisition card, PC with LabVIEW Real-Time Module.
4:Experimental Procedures and Operational Workflow:
FRFs are measured to identify the system model. Controllers (IRC, PPF, PVPF, 2DOF-PI2D) are designed and implemented. Tracking performance is tested with triangular and polynomial reference trajectories, and circular trajectories in simulations.
5:Data Analysis Methods:
Root mean square error (RMSE) is calculated for tracking performance. Bode sensitivity integrals and phase responses are analyzed. Stability is assessed via root locus and pole placement.
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