Abstract
Nanopositioning systems are very popular and playing an increasingly vital role in micro and nano-scale positioning industry due to their unique ability to achieve high-precision and high-speed operation. However, hysteresis, commonly existing in piezoelectric actuators, degrades the precision seriously. Uncertain dynamics and sensor noises also greatly affect the accuracy. To address those challenges, a variable bandwidth active disturbance rejection control (VBADRC) is proposed and realized on a nanopositioning stage. All undesired issues are estimated by a time-varying extended state observer (TESO), and cancelled out by a variable bandwidth controller. Convergence of the TESO, advantages of a TESO over a linear extended state observer (LESO), and the closed-loop stability of the VBADRC are proven theoretically. Improvements of the VBADRC versus the linear active disturbance rejection control (LADRC) are validated by simulations and experiments. Both numerical and experimental results demonstrate that the VBADRC is not only able to provide the same disturbance estimation ability as the LADRC, but also more powerful in noise attenuation and reference tracking.
Highlights
Nanopositioning is a key technology in modern precision and ultrahigh-precision manufacturing, such as atomic force microscope (AFM), biological micromanipulation, and precision mirror alignment [1]–[3]
linear active disturbance rejection control (LADRC) is commonly used for its satisfied performance and practical design, measurement noises are not considered in its design
SIMULATION RESULTS the variable bandwidth active disturbance rejection control (VBADRC) is verified by numerical simulations
Summary
Nanopositioning is a key technology in modern precision and ultrahigh-precision manufacturing, such as atomic force microscope (AFM), biological micromanipulation, and precision mirror alignment [1]–[3]. Active disturbance rejection control (ADRC) has been exploited to estimate and suppress the uncertainties arising from hysteresis, creep, and other unknown disturbances [17] Those ways do not take sensor noises into consideration. In order to verify the VBADRC, a linear ADRC (LADRC) has been presented for comparisons Both numerical and experimental results have been given to confirm the proposed approach. TIME VARYING ACTIVE DISTURBANCE REJECTION CONTROL linear active disturbance rejection control (LADRC) is introduced first Considering both disturbance rejection and sensor noises suppressing, a variable bandwidth active disturbance rejection control (VBADRC) is proposed. States, u is the control input, n sensor noise, y is the output, b0 is the tunable coefficient of a control input, d is the disturbance, t is the time variable, and f (x1, x2, u, d, t) represents the uncertain dynamics, it is known as a generalized disturbance.
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