Browsing by Author "Salamci, Metin U."

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    A review on vibration characteristics of additively manufactured metal alloys
    (Wiley, 2024-01-19) Azher, Kashif; Shah, Mussadiq; Bakhtari, Ahmad Reshad; Castelluccio, Gustavo M.; Tüfekci, Celal Sami; Cini, Andrea; Akturk, Nizami; Salamci, Metin U.
    The advent of additive manufacturing (AM) has dramatically shifted the manufacturing sector conceptualization, design, and creation of products. AM can facilitate the production of complicated geometries and create functioning components with distinctive features for aerospace and automotive applications. However, defects such as pores, voids, interfaces, and inclusions can impair the quality and functionality of AM components. Vibration analysis (VA) has become a popular tool for the dynamic qualification and testing of products and nondestructive testing, but the literature lacks a comprehensive review of VA applied to AM. Hence, in this article, recent advances in the application of VA for identifying and characterizing flaws in metal alloys, including titanium, aluminum, and nickel-based alloys produced by AM, are summarized. In this review, studies on defects such as porosity, cracks, and inclusions and their effect on VA are also included. Herein, this article concludes with a discussion of the limitations of VA for defect characterization and future research directions. Overall, VA is a promising nondestructive testing method for quality assurance in AM and offers insights on overcoming the difficulties for further development and application of this technology.
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    Sliding surface optimization via regional pole placement for a class of nonlinear systems
    (IEEE, 2023-10-10) Arıcan, Ahmet Çağrı; Çopur, Engin Hasan; Inalhan, Gokhan; Salamci, Metin U.
    In this paper, a new approach is introduced which combines Eigenvalue Assignment, State Dependent Riccati Equation (SDRE) and Sliding Mode Control (SMC) methods for nonlinear systems. In the classical SDRE based SMC (SDRESMC) approach, a nonlinear system is frozen at each time instant to obtain a linear-like structure model that is used to design a sliding surface (SS) at each time instant. This mechanism produces a state-dependent SS to hold the states on the SS. The approach proposed here is built on this mechanism and offers a new way to design a state-dependent SS for nonlinear systems so that the pointwise eigenvalues of the closed-loop system matrix of the control-free dynamics in the regular form can be kept in a specified disk. This gives a great advantage to shape the transient response characteristics. The performance of the nonlinear controller approach proposed here is investigated in simulations.
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    State dependent regional pole assignment controller design for a 3-DOF helicopter model
    (IEEE, 2023-06-26) Arıcan, Ahmet Çağrı; Çopur, Engin Hasan; Inalhan, Gokhan; Salamci, Metin U.
    For linear systems, a state feedback control law can be easily designed to keep all closed-loop poles inside a specified disk since the locations of the poles are unique. However, its application to nonlinear systems is not so simple. Therefore, this paper introduces a new pole placement method, named as State Dependent Regional Pole Assignment, for nonlinear systems. This proposed method produces a state dependent feedback control law, enabling the eigenvalues of the closed-loop matrix to be placed in a specified disk to achieve the desired control performance characteristics. The effectiveness of the method is tested on the 3 DOF Helicopter experimental setup. To verify its effectiveness, the experimental results of the nonlinear method are compared with those of the linear method.