Functional observers for motion control systems

This paper presents a novel functional observer for motion control systems to provide higher accuracy and less noise in comparison to existing observers. The observer uses the input current and position information along with the nominal parameters of the plant and can observe the velocity, acceleration and disturbance information of the system. The novelty of the observer is based on its functional structure that can intrinsically estimate and compensate the un-measured inputs (like disturbance acting on the system) using the measured input current. The experimental results of the proposed estimator verifies its success in estimating the velocity, acceleration and disturbance with better precision than other second order observers

Development of a control framework for hybrid renewable energy system in microgrid

Electrical energy has an essential role in society as it ensures high quality of life and steady economic development. Demand for the electric energy has been steadily growing throughout the recent history and this demand is expected to grow further in the future. Most of electrical energy nowadays is generated by burning fossil fuels and there are serious concerns about the resulting emission. Renewable energy sources appeared as a viable alternative for environmentally hazardous sources. However, sources of renewable energy have considerably unpredictable and environmental conditions dependent power output and as such can’t be directly incorporated into existing electrical grid. These sources are usually integrated to the electrical grid as part of microgrid or hybrid energy source that consists of two or more energy sources, converters and/or storage devices. In hybrid energy sources, generation and storage elements complement each other to provide high quality and more reliable power delivery. This area of research is its infant stage and requires a lot of research and development effort to be done. Main objective of this thesis is to develop a framework for analysis and control of power electronics interfaces in microgrid connected hybrid energy source. The framework offers the generalized approach in treatment of control problem for hybrid energy sources. Development of the framework is done for the generalized hybrid source comprised of energy source(s), storage element(s), power electronic interfaces and control system. The main contributions of this thesis are, generalization of control problem for power electronics interfaces in hybrid energy source, the development of switching algorithm for three phase switching converters based on the closed loop behavior of the converters and the development of a maximum power point tracking algorithm for the renewable energy sources

High precision motion control of parallel robots with imperfections and manufacturing tolerances

This work attempts to achieve precise motion control using parallel robots with manufacturing tolerances and inaccuracies by migrating the measurements from their joint space to task space in order to decrease control system’s sensitivity to any kinematical uncertainty rather than calibrating the parallel plant. The problem of dynamical model uncertainties and its effect on the derivation of the control law is also addressed in this work through disturbance estimation and compensation. Eventually, both task space measurement and disturbance estimation are combined to formulate a control framework that is unsensitive to either kinematical and dynamical system uncertainties

Design and realization of laser micromachining system

The production process of miniature devices and microsystems requires the utilization of nonconventional micromachining techniques. In the past few decades laser micromachining has became an important micromanufacturing technique for many industrial and research applications. The popularity of this technique lies mostly in its noncontact nature. Unique characteristic of the laser micromachining is the possibility of etching or ablating exceptionally small features in many different materials with minimal damage done to the non irradiated regions of the material. For the purposes of achieving of precise and high quality laser micromachining and for full exploration of laser advantages as microprocessing tool, the development of reliable and easy to use laser micromachining system is of great importance. In this thesis, the design approach to the general purpose laser micromachining system is discussed. Detailed description of implementation of each module of the system is given. The designed laser micromachining system can be used for many microprocessing applications such as micromarking, microchannels machining, thin film cutting, etc. The design of the precise positioning planar x-y stage and trajectory generation and control method for this stage are discussed. The development of software and man machine interface for laser micromachining system is also presented. In order to verify the functional and operational capabilities of the designed system, precise aluminum marking, subsurface marking of glass, brass ablation and drilling of miniature holes in brass are preformed and experimental results are presented

Force control of piezoelectric walker

This paper is concerned with the force control of a walking piezoelectric motor, a commercially available Piezo LEGS motor. The motor is capable of providing high precision positioning control on nanometer scale, but also relatively high forces up to 6 N. The proposed force control algorithm is very simple, but effective, and it is based on a recently presented coordinate transformation. The transformation allows definition of the driving waveforms for the motor according to a desired motion of the motor legs in the plane of motion. Such a possibility opens a path for creating the y-direction interaction force between the motor legs and the rod which is enough to ensure no relative motion between the legs and the rod. Once that is achieved, one can control the x-direction force imposed by the motor rod on its environment. The presented force control scheme has been successfully validated through a series of experiments

Design and control of laser micromachining workstation

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

Optimal motion control and vibration suppression of flexible systems with inaccessible outputs

This work addresses the optimal control problem of dynamical systems with inaccessible outputs. A case in which dynamical system outputs cannot be measured or inaccessible. This contradicts with the nature of the optimal controllers which can be considered without any loss of generality as state feedback control laws for systems with linear dynamics. Therefore, this work attempts to estimate dynamical system states through a novel state observer that does not require injecting the dynamical system outputs onto the observer structure during its design. A linear quadratic optimal control law is then realized based on the estimated states which allows controlling motion along with active vibration suppression of this class of dynamical systems with inaccessible outputs. Validity of the proposed control framework is evaluated experimentally

Yürüyen piezoelektrik motorların sürülmesi

Piezoelektrik eyleyicilerin geliştirilmesi mikro ve nano ölçeklerde yapılan yüksek hassasiyete sahip konumlandırmaların yapılabilmesine olanak sağlamıştır. Fakat piezoelektrik malzemeler doğası gereği lineer olmayan bir yapıya sahiptir. Bu da piezoelektrik eyleyicilerin denetlenmesini ve sürüşünü zorlaştırmaktadır. Piezoelektrik eyleyicilerin sürülmesi ve denetlenmesi için sistemde, ilgili denetleme yöntemlerinde ve uygun sürücü elektroniği konularında titiz bir araştırma yapmak gerekmektedir. Bu makalede, yürüyen piezoelektrik motorların sürülebilmesi amaçlı, iki farklı sürücü incelenmektedir. Bu sürücüler ise ticari olarak kullanılan ve bahsi geçen yazarlar tarafından tasarlanan ses güçlendirici devre yapısına sahip sürücülerdir. Motora beslenen dalga formlarının giriş frekanslarını denetlemek için kaskat denetleyici kullanılmıştır. Yüksek hassasiyet gerektiren uygulamalarda, Motorun piezo-bacaklarının, dalga formlarının değişen faz, genlik ve frekanslarıyla ayrı ayrı denetlenmesi sonucunda, sürücülerin kullanılmasında belirli kısıtlamalar gözlenmiş ve bu durum da çok amaçlı sürücülerin ortaya çıkmasını sağlamıştı

A novel current controller scheme for doubly fed induction generators

This paper presents a novel current control methodology for grid connected doubly-fed induction generator (DFIG) based wind energy conversion systems. Controller is based on a proportional controller with additional first order low pass filter disturbance observer which estimates the parameter dependent nonlinear feed-forward terms. The results in simulations and experimental test bed obviously demonstrate that decoupled control of active and reactive power is achieved without the necessity of additional machine parameter

Modeling and control of doubly fed induction generator with a disturbance observer: a stator voltage oriented approach

The popularity of renewable energy conversion systems, and especially of wind energy, has been growing in recent years. Doubly fed induction generator (DFIG)-based wind energy systems are extensively used due to their wide range of active and reactive power controllability. Conventional DFIG control structures consist of decoupled PI rotor current controllers with stator flux orientation and machine parameter-dependent compensating terms. The accuracy of stator flux calculations is dependent on how accurately the stator resistance is known. Integration problems also exist and additional low-pass filters are implemented to accurately calculate the stator flux. In the current study, machine-dependent compensating terms are estimated with a first-order low-pass filter disturbance observer. Therefore, a single proportional (P) controller is suficient to control decoupled rotor currents. The proposed controller structure is implemented on a MATLAB/Simulink platform with the parameters of 500 kW DFIG used in the MILRES (Turkish National Wind Energy) project. The proposed controller is also experimentally validated in an experimental setup