Experimental System Identification and Disturbance Observer-based Control for a Monolithic $Zθ_{x}θ_{y}$ Precision Positioning System

Abstract

A compliant parallel micromanipulator is a mechanism in which the moving platform is connected to the base through a number of flexural components. Utilizing parallelkinematics configurations and flexure joints, the monolithic micromanipulators can achieve extremely high motion resolution and accuracy. In this work, the focus was towards the experimental evaluation of a 3-DOF (Zθxθy) monolithic flexure-based piezodriven micromanipulator for precise out-of-plane micro/nano positioning applications. The monolithic structure avoids the deficiencies of non-monolithic designs such as backlash, wear, friction, and improves the performance of micromanipulator in terms of high resolution, accuracy, and repeatability. A computational study was conducted to investigate and obtain the inverse kinematics of the proposed micromanipulator. As a result of computational analysis, the developed prototype of the micromanipulator is capable of executing large motion range of ±238.5µm × ±4830.5µrad × ±5486.2µrad. Finally, a sliding mode control strategy with nonlinear disturbance observer (SMC-NDO) was designed and implemented on the proposed micromanipulator to obtain system behaviours during experiments. The obtained results from different experimental tests validated the fine micromanipulator's positioning ability and the efficiency of the control methodology for precise micro/nano manipulation applications. The proposed micromanipulator achieved very fine spatial and rotational resolutions of ±4nm, ±250nrad, and ±230nrad throughout its workspace.Note to Practitioners-Piezo-actuated precision positioning systems play an increasingly important role in the fields of micro/nano manipulation robots. They have the advantages of fine resolution, high accuracy, fast response speed, and large output displacement. However, such systems inherently exhibit vibration, hysteresis behaviors, and are affected by external disturbances that could cause oscillations and positioning errors. This study presents a robust control methodology implemented on a 3-DOF positioning system (Zθxθy), which is among the most prone system to be affected by existing disturbances. This control methodology is designed to improve the tracking performance in the presence of hysteresis nonlinearity, disturbances, and modeling errors. The effectiveness of the proposed control methodology is demonstrated by conducting a series of experiments. Due to the ease of implementation, the developed control methodology can be applied to other positioning systems as well.

Monolithic Six-DOF Parallel Positioning System for High-precision and Large-range Applications

“…Due to the large range, high resolution, and compactness of the positioner, it can be modified to be utilized in many applications including pick-and-place manipulation, tremor compensation in microsurgery and micro-assembly, and collaborative manipulators systems. In order to improve the accuracy of positioning tasks performed by the proposed positioner, a robust adaptive [33] disturbance observer-based controller can be established [34]- [36]. In addition, uncertainty analysis can be conducted to improve the accuracy of rotational measurements.…”

Design and Testing of a Compliant ZTTΘ Positional Adjustment System with Hybrid Amplification

“…Although this system has a simple structure, the accuracy of a single-branched chain directly impacts the overall performance, necessitating the sacrifice of motion stroke (only a few tens of micrometers) to achieve high-precision single-branched chains [10][11][12][13][14].…”