ed/Indexed in Science Citation Index Expanded, SCOPUS, EBSCO and INSPEC (Institution of Electrical Engineers)

A 3-PRR flexure based mechanism which is used as a redundant mechanism providing only x-y micro positioning is designed and controlled in this paper. The aim of this work is to eliminate the unpredictable motions due to manufacturing and assembling errors by implementing sliding mode control (SMC) with disturbance observer (DOB) using piezoelectric actuator models. The system is designed to be redundant to enhance the position control. In order to see the effects of the redundant system firstly the closed loop control is implemented for 2 piezoelectric actuators and the remainder piezoelectric actuator is treated as a fixture. Then the position control is implemented for 3 piezoelectric actuators. As a result, our redundant mechanism tracks the desired trajectory accurately and its workspace is bigger. Finally we have compared the proposed position control with the conventional PID control. It is seen that SMC with DOB gives better results. We have achieved to make the position control of our mechanism, which has unpredictable position errors due to rough manufacturing, assembly, piezoelectric actuator hysteresis etc. The designed 3-PRR flexure mechanism can be used as a micro positioner with the available measurement in the laboratory.

This paper discusses the trajectory generation algorithm, contour error construction method and finally the contour controller design. In the trajectory generation algorithm combination of elliptical Fourier descriptors (EFD) and time based spline approximation (TBSA) is used to generate position, velocity and acceleration references. Contour error is constructed using transformation of trajectory tracking errors. Transformation is computationally efficient and requires only reference velocity information. Contour controller is designed using sliding mode control. Experiments are performed on planar linear motion stage and significant contour error reduction is observed.

This paper introduces a codec scheme for compressing control and feedback signals especially for bilateral control systems. The method uses a low pass filter and Wavelet Packet Transform (WPT) for coding and Inverse Wavelet Packet Transform (IWPT) for decoding. Data compression is handled in low pass filter output by reducing sampling rate; and in high pass filter output by reducing wavelet outputs. Codec works on both data paths, which flows between a master system and a slave system over a networked control architecture. With the proposed scheme, a greater percent of the compressed data can be recovered using the same compression rate. It is confirmed that the controller using compressors and decompressors performs similarly as the uncompressed one while enabling transmission of much less data over network. The viability of the proposed scheme is proven by experiments on a single-DOF motion control system controlled over network. Proposed method is also compared with a benchmark method which uses DFT for compression.

In the past decade wind energy systems were developed for efficient energy conversion. Most of the variable speed wind turbine systems include doubly fed induction generator (DFIG). DFIGs are used in electrical grid connected and standalone systems. This paper presents a novel, robust, rotor current controller structure for both grid connected and stand-alone DFIG applications. Controller is designed for the robustness against change in machine parameters, generator speed changes and load changes in stand alone systems. In the heart of controller design lays low pass filter based disturbance observer. Experimental results are provided that verify controller performance in grid connected scenario and stand alone generator scenario (local grid). Experiments are done using 1.1KW DFIG experimental test bed and custom developed switching inverter.

This paper analyzes two recently proposed compression decompression algorithms used in networked motion control systems. The algorithms contain discrete cosine transform (DCT) based and discrete fourier transform (DFT) based codecs for the realization of signal transmission over network. The backgrounds of the algorithms are presented along with a discussion on the advantages and disadvantages. Comparison of the performances of both algorithms are presented based on three different evaluation criteria including compression ratio, buffer size and power error. The differences between the algorithms are validated with results obtained from a series of experiments. Theoretical details regarding the differences between the results obtained from experiments are provided to present a complete analysis between two approaches.

This work presents an energy-based state estimation formalism for a class of dynamical systems with inaccessible/unknown outputs, and systems at which sensor utilization is impractical, or when measurements can not be taken. The power-conserving physical interconnections among most of the dynamical subsystems allow for power exchange through their power ports. Power exchange is conceptually considered as information exchange among the dynamical subsystems and further utilized to develop a natural feedback-like information from a class of dynamical systems with inaccessible/unknown outputs. This information is used in the design of an energy-based state observer. Convergence stability of the estimation error for the proposed state observer is proved for systems with linear dynamics. Furthermore, robustness of the convergence stability is analyzed over a range of parameter deviation and model uncertainties. Experiments are conducted on a dynamical system with a single input and multiple inaccessible outputs (Fig. 1) to demonstrate the validity of the proposed energy-based state estimation formalism.

This paper presents the realization of a modular software architecture that is capable of handling the complex supervision structure of a multi degree of freedom open architecture and reconfigurable micro assembly workstation. This software architecture initially developed for a micro assembly workstation is later structured to form a framework and design guidelines for precise motion control and system supervision tasks explained subsequently through an application on a micro assembly workstation. The software is separated by design into two different layers, one for real-time and the other for non-realtime. These two layers are composed of functional modules that form the building blocks for the precise motion control and the system supervision of complex mechatronics systems.

The production process of miniature devices and microsystems requires the utilization of non-conventional micromachining techniques. In the past few decades laser micromachining has became micro-manufacturing technique of choice for many industrial and research applications. This paper discusses the design of motion control system for a laser micromachining workstation with particulars about automatic focusing and control of work platform used in the workstation. The automatic focusing is solved in a sliding mode optimization framework and preview controller is used to control the motion platform. Experimental results of both motion control and actual laser micromachining are presented.

In this paper, design and control issues for the development of miniaturized manipulators which are aimed to be used in high precision assembly and manipulation tasks are presented. The developed manipulators are size adapted devices, miniaturized versions of conventional robots based on well-known kinematic structures. 3 degrees of freedom (DOF) delta robot and a 2 DOF pantograph mechanism enhanced with a rotational axis at the tip and a Z axis actuating the whole mechanism are given as examples of study. These parallel mechanisms are designed and developed to be used in modular assembly systems for the realization of high precision assembly and manipulation tasks. In that sense, modularity is addressed as an important design consideration. The design procedures are given in details in order to provide solutions for miniaturization and experimental results are given to show the achieved performances.

This paper presents an analytical approach for the prediction of future motion to be used in input delay compensation of time-delayed motion control systems. The method makes use of the current and previous input values given to a nominally behaving system in order to realize the prediction of the future motion of that system. The generation of the future input is made through an integration which is realized in discrete time setting. Once the future input signal is created, it is used as the reference input of the remote system to enforce an input time delayed system, conduct a delay-free motion. Following the theoretical formulation, the proposed method is tested in experiments and the validity of the approach is verified.