This paper describes the development of a nano-assembly system, built up using linear piezo motors. The so-called nano-robotic cell is based on an X/Y manipulator, supported by three serving tables, movable within a Z axis, and a position controlled using two different types of a bang-bang control methods. The presented application has been developed as a stand-alone application with the LabVIEW Real Time software package, a PCI-7356 servo controller card and a TMCM-090 stepper driver. Our experiments focused on two major problems present during the construction of nano-robotic assembly cells. The first one is a nonlinear characteristic of a linear piezo motor, which makes the use of classical control methods very limited. The second problem appears when a nano-robotic cell needs a bigger working space and at the same time, production demands that the manipulator moves more often over longer distances. In order to position in nano-resolution, the motors have to run at higher resolutions with smaller speeds. Therefore, long distance moves slow down the entire production process. Experiments on this system have shown that positioning within the nano-scale is possible, using a simple control method such as the bang-bang control method. Although positioning using this method is possible, certain limitations and weaknesses exists, making this simple method useless in nano-scale if higher speeds and longer move distances are needed. Certain changes in the basic control algorithm are proposed, which will ensure that the bangbang control method becomes useful within higher speeds and over longer distances. All recommendations are supported and backed- up by practical experimental results.

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Position Control with Parameter Adaptation for a Nano-Robotic Cell

Macro- and micro-dynamic mechanical non-linearities limiting the precision of con- ventional DC motor-driven positioning systems based on sliding and rolling elements have been characterized experimentally via a laser interferometric system. The obtained results confirm recent tribological models. In particular, the parameters describing the non-linear elastic and plastic phenomena related to pre-sliding displacement have been identified and used to develop an integrated system model. It was therefore possible to prove that, in the range of displace- ments corresponding to the pre-sliding phase, there is a quadratic dependence between the duration of an actuating impulsive force and the resulting displacement. According to a pulse width scheme, a control law has been implemented whose adaptive structure compensates for the position and time variability of the observed non-linear effects. The application of the proposed approach to both short and long travel ranges and the reached nanometric accuracies confirm the applicability of the proposed control scheme to compensate concurrently the macro- and the micro-dynamic effects.

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Nano-positioning using an adaptive pulse width approach:

This paper describes an experimental approach to the adaptive positioning of a MEMS production system with nano - scale resolution. It is known that accurate positioning within nano - scale requires higher move resolutions which cause drastic speed reductions. Production processes which are running within such production systems are therefore very time consuming or very limited due to their working spaces. We are proposing an adaptive approach to the positioning within nano -scale, which will help us extend the size of the system's working space in such a way that it will not be time consuming. The basic idea of our approach is that the move resolution and the move speed are adapted according to the size of positioning error. Large positioning error sets the system to low resolution and high speed. As a separate axis approaches the target point, positioning error decreases, move resolution increases, and move speed decreases. The so called adaptive approach was tested on the positioning system wi...

/pdf/adaptive-positioning-of-mems-production-system-with-nano-4qyyd0i5p5.pdf

Adaptive Positioning Of Mems Production System With Nano – Resolution

For the tracking stage path planning, we design a two-axis cross-coupling control system which uses the PI controller to compensate the contour error between axes. In this paper, the stage adoptive is designed by our laboratory (Precision Machine Center of National Formosa University). The cross-coupling controller calculates the actuating signal of each axis by combining multi-axes position error. Hence, the cross-coupling controller improves the stage tracking ability and decreases the contour error. The experiments show excellent stage motion. This finding confirms that the proposed method is a powerful and efficient tool for improving stage tracking ability. Also found were the stages tracking to minimize contour error of two types circular to approximately 25nm.

Study of Improving Nano-Contouring Performance by Employing Cross-Coupling Controller

Study of improving nano-contouring performance by employing cross-coupling controller

To achieve fast nano-positioning control in a large traveling distance with a single motion stage and without a waiting time, this paper presents a micro-dynamic model together with a simple switching rule and two controllers, one for macro-dynamics and the other for micro-dynamics, such that the moving stage can smoothly travel from macro-dynamic range into micro-dynamic range. First, a micro-dynamic model is proposed to capture the complicated hysteresis behavior of the nonlinear micro-dynamics. Next, two controllers of simple structures are designed for the micro-dynamic traveling range and the macro-dynamic traveling range, respectively, based on the previous model. Finally, a simple switching law is proposed to complete a design. Experiments show that the resultant control system has a fast response speed without a sluggish response in the conjunction of the macro-dynamic range and the micro-dynamic range. Furthermore, it can sustain large disturbances while holding the motion stage at the set point.

S.H. Wu

Papers

A fast control law for nano-positioning