Jing-Chung Shen

Sliding-Mode Tracking Control With DNLRX Model-Based Friction Compensation for the Precision Stage

This paper concerns the development of a sliding-mode tracking controller with friction compensation for a precision positioning stage with cross-roller guides. Experiments including prerolling and rolling friction regimes are conducted, and then a two-stage parameter estimation algorithm is used to identify the parameters of a friction dynamic model (Dynamic NonLinear Regression with direct application of eXcitation, DNLRX, model). This model allows the estimation of the friction force in combination with the system dynamics against displacement, and can be used as a feed-forward controller to compensate for the friction effect. To compensate for model error and uncertain disturbances, an integral sliding-mode controller with a disturbance estimation scheme is designed and combined with the DNLRX feed-forward controller to control the motion of a precision stage. Experimental results show that with the proposed controller, tracking performance can be improved.

Novel control scheme for a high-speed metrological scanning probe microscope

Some time ago, an interferometer-based metrological scanning probe microscope (SPM) was developed at the Institute of Process Measurement and Sensor Technology of the Ilmenau University of Technology, Germany. The specialty of this SPM is the combined deflection detection system that comprises an interferometer and a beam deflection. Due to this system it is possible to simultaneously measure the displacement, bending and torsion of the probe (cantilever). The SPM is integrated into a nanopositioning and nanomeasuring machine (NPM machine) and allows measurements with a resolution of 0.1 nm over a range of 25 mm ? 25 mm ? 5 mm. Excellent results were achieved for measurements of calibrated step height and lateral standards and these results are comparable to the calibration values from the Physikalisch-Technische Bundesanstalt (PTB) (Dorozhovets N et al 2007 Proc. SPIE 6616 661624?1?7). The disadvantage was a low attainable scanning speed and accordingly large expenditure of time. Control dynamics and scanning speed are limited because of the high masses of the stage and corner mirror of the machine. For the vertical axis an additional high-speed piezoelectric drive is integrated in the SPM in order to increase the measuring dynamics. The movement of the piezoelectric drive is controlled and traceable measured by the interferometer. Hence, nonlinearity and hysteresis in the actuator do not affect the measurement. The outcome of this is an improvement of the bending control of the cantilever and much higher scan speeds of up to 200 ?m?s?1.

Control of a high precision positioning stage

Control of a two dimensional high precision positioning stage is presented in this work 1. This stage is composed by two kinds of stages, a two degrees-of-freedom (DOF) (X and Y) linear cross roller guideway supported stage and a 4-DOF (Z, θx, θy and θz) piezo-stage. Two linear shaft voice coil motor are used to actuate the roller guided X-Y stage and five piezoelectric actuators are used in the piezo-stage. The positioning range of the X-Y stage is 25 mm × 25 mm and the piezo-stage is designed to compensate the vertical position, row, pitch and yow errors throughout the whole working range. A 6-DOF optical measurement system that consists of three laser interferometers and two quadrant photo-diodes is used to measure the attitude of the stage. The resolution of this measurement system is about 9.8 nm and 0.1 arc second. Integral sliding-mode controllers are used to control the linear motor driven stage while PID controllers are used to control the piezo-stage. Experimental results show that the positioning uncertainty is about ±20 nm.

Development of a novel multi-axis nano-positioning and the spiral tracking control

This paper presents the design of a sliding-mode controller for a piezoelectric-driven nanometer resolution stage. The nanometer resolution stage is developed using the features of a flexible structure, and is driven by piezoelectric actuators and also uses capacitance sensors for position feedback. The hysteresis characteristic of the piezoelectric actuators is one of the major deficiencies in a wide variety of precise tracking positioning controls. In order to design the control system, the open-loop characteristics of this nanometer resolution stage are investigated. According to the open-loop characteristics, each pair of piezoelectric actuator and capacitance sensor is treated as an independent system and modeled as a first order linear model coupled with hysteresis. When the model is identified, the hysteresis nonlinearity is linearized then the linear system model with uncertainty is used to design the controller. When designing the controller, the sliding-mode disturbance estimation and compensation scheme is used. The structure of the proposed controller is similar to the PID controller. Thus, it can be easily implemented.

INTEGRAL SLIDING-MODE CONTROL OF A PIEZOELECTRIC-ACTUATED MOTION STAGE

Abstract This paper presents the design of an integral sliding-mode controller for a piezoelectric-actuated system. The sliding-mode disturbance (uncertainty) estimation and compensation scheme is used. The nonlinear piezoelectric-actuated system is modeled as a first order linear model coupled with a hysteresis. When the model is identified, the hysteresis nonlinearity is linearized then the linear system model with uncertainty is used to design the sliding-mode controller. The structure of the proposed controller is as simple as the PID controller. Thus, it can be implemented easily. This design method is applied to the motion control of a nano-stage and experimental results are presented.

Active Probe Control of a Metrological Atomic Force Microscopy

Abstract This article considers the force control of an active probe for Atomic Force Microscopy (AFM). Firstly, the structure of this active probe is described. For designing the force controller, the model of this active probe was identified. Based on the measured frequency response, two notch filters were used to remove the resonant peak in open-loop frequency response. Then, a PI controller was designed to regulate the force of the probe. This controller was then implemented in a Digital Signal Processor (DSP). Experimental results were given to compare the actual performance of this controller with the conventional PI controller. It is shown that the controller with notch filters reduces the control error considerably and enables faster scan speed at weaker tip-sample interaction forces.

Control of a Five-Degrees-of-Freedom Nanopositioner

Abstract This paper presents the tracking control of a five-degrees-of-freedom nanopositioner. This nanopositioner is actuated by piezoelectric actuators. Capacitive gap sensors are used for position feedback. Firstly, the modified Prandtl-Ishlinskii (MPI) model is used to model the hysteresis nonlinearity of piezoelectric actuator, and then its inverse is used to cancel out the hysteresis nonlinearity. In order to design the feedback controller, the linearized open-loop characteristics of this nanopositioner are investigated. Based on the results of investigation, each pair of piezoelectric actuator and corresponding gap sensor are treated as independent systems and modeled as a uncertain first order linear model. When the model is identified, the linear system model with uncertainty is used to design the controller. The sliding-mode disturbance (uncertainty) estimation and compensation scheme is used in this study. Experimental results are given to show the effectiveness of the proposed method.

Control of a long-stroke precision scanning stage

This study presents the control of a long-stroke precision scanning stage. The stage considered is combined by a linear motor-driven long-stroke stage (X, Y) and a piezoelectric-driven two degrees of freedom (2-DOF) nano-stage (Y, θZ). Therefore, it can provide long-stroke and high-precision positioning. The feedback signal for this stage is obtained using a 3-DOF laser interferometer measurement system. Integral sliding-mode controllers are used to control the linear motor-driven stage and PID controllers are used to control the piezo-stage for precision positioning. This paper presents the design of the controllers and the control results. Experimental results show that when X-axis scanned at speed 100mm/s, the averaged error and root mean square (RMS) error for y positioning are 10.6 nm and 13.1 nm and the averaged error and RMS error of θZ are 0.17 and 0.22 respectively.

Development of a Laser Based Dual-Axial Five-Degrees-of-Freedom Measurement System for an X-Y Stage

This paper presents a new precision multi-DOF measurement system which has been developed and implemented for the simultaneous measurement of 5DOF motion errors (two linear positions, as well as pitch, roll and yaw) of an X-Y stage. In this paper, the 3DOF laser interferometer was produced by designing the optical path from the one-degrees-of-freedom laser interferometer. The system employs two three-degree-of-freedom interferometers to detect two position errors and three angular errors of the X-Y stage. The experimental setups and measuring procedure and a systematic calculated method for the error verification are presented in the paper. The resolution of measuring the angular errors component is about 0.055 arcsec.Copyright