Abstract
Both speed and accuracy are key issues in nano-positioning. However, hysteresis existing in piezoelectric actuators severely reduces the positioning speed and accuracy. In order to address the hysteresis, a U-model based active disturbance rejection control is proposed. Based on the linear active disturbance rejection control, a controlled plant is dynamically transformed to be pure integrators. Then, according to the U-model control, a common inversion is obtained and the controlled plant is converted to be “1.” By integrating advantages of both linear active disturbance rejection control and U-model control, the U-model based active disturbance rejection control does promote the reference tracking speed and accuracy. Stability and steady-state error of the close-loop system have been analyzed. Phase lag between the system output and the control input has been effectively eliminated, and the phase-leading advantage of the U-model based active disturbance rejection control has been confirmed. Experimental results show that the U-model based active disturbance rejection control is capable of achieving faster and more accurate positioning. Remarkable improvements and practical realization make the U-model based active disturbance rejection control more promising in nano-positioning.
Highlights
Nanotechnology is the science of understanding and controlling the matter at dimensions of 100 nm or less.1 Piezoelectric actuators are widely used in nanopositioning due to their various advantages.2 hysteresis, an inherent property in piezoceramic materials,3 becomes a key factor that hinders positioning speed and precision
Based on a modified Bouc-Wen model, a feedforward compensation approach is proposed,8 an iterative learning control and a direct inverse hysteresis compensation have been designed to achieve high-precision reference tracking,9 and an adaptive inverse control is proposed to address the hysteresis.10. Those approaches are based on accurate hysteresis models
Instead of modeling the hysteresis, the hysteresismodel-free robust control regards the hysteresis as a disturbance
Summary
Nanotechnology is the science of understanding and controlling the matter at dimensions of 100 nm or less. Piezoelectric actuators are widely used in nanopositioning due to their various advantages. hysteresis, an inherent property in piezoceramic materials, becomes a key factor that hinders positioning speed and precision. Hysteresis models, such as Preisach model, Prandtl-Ishlinskii model, and modified Bouc-Wen model, have been established Based on those hysteresis models, inverse models have been built, and numerous hysteresis-model-based feedforward control techniques have been proposed. Based on a modified Bouc-Wen model, a feedforward compensation approach is proposed, an iterative learning control and a direct inverse hysteresis compensation have been designed to achieve high-precision reference tracking, and an adaptive inverse control is proposed to address the hysteresis.. Based on a modified Bouc-Wen model, a feedforward compensation approach is proposed, an iterative learning control and a direct inverse hysteresis compensation have been designed to achieve high-precision reference tracking, and an adaptive inverse control is proposed to address the hysteresis.10 Those approaches are based on accurate hysteresis (inverse) models.. A sliding mode control (SMC) and an improved SMC are proposed to make the closed-loop system more robust.
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