Rifat Hacioglu

Teleconferencing Acoustic Echo Cancellation Using Adaptive Hammerstein Block Structure

Acoustic echo in voice transmission systems severely degrades the speech quality and the speech intelligibility of speech signal due to it is formed through picking up sounds from the loudspeaker by speaker microphone. The dynamic structure of the acoustic echo system contains cascade connection of an electro-acoustic static nonlinear system and a dynamic linear system. Hence linear models can not be successful solution to echo problem. In this paper, acoustic echo problem is mentioned and an algorithm that adapts the parameters of nonlinear Hammerstein system (cascade connection of a static nonlinearity and a dynamic linear system) is suggested.

Simultaneous localization and mapping of mines with unmanned aerial vehicle

In this study, the position information from ultrasound sensors on UAV related to floor gallery mine passed through the filter, it is aimed to control the position of simultaneously creating the optimum environmental map. The simultaneous in galleries made mapping, mine the data of air to the designated central monitoring system with real-time location information is transmitted to the ventilation system, which is intended to more effectively work in the mines. The gallery maps which simultaneous location and mapping information obtained by UAV Extended Kalman Filter algorithms processed were obtained experimentally.

Ultrasonic location detection with waveguide

Time delay estimation has been used as a research area of significant practical important in many fields such as especially military system like localization, targeting, course acquisition also sonar, seismology, hands-free communications etc. In these applications, it is important to detect the delay and arrival times of ultrasonic echoes comprised in the medium for ultrasonic signals. Here, it is aimed to determine the time delay between the signals arrived from a signal source in order to detect the location. Hence, a system is suggested that uses a multi-surfaced waveguide with only one receiver instead of using receiver arrays. By using this structure, time delay estimation is compared for different signal-to-noise ratios with Cross-Correlation, Maximum Likelihood and Phase Transform methods.

The controller of the camera used in target tracking for unmanned vehicle with model predictive controller

In this study, unmanned vehicles used for target tracking camera RRP (revolute revolute prismatic) joint structure with a three-jointed robot arm with the position, velocity and acceleration control is made. In order to be able to follow the specified trajectory, the system used in the control of the robot arm with joint structure RRP target tracking model based on changing according to the structure proposed by the MPC is implemented. Also the PID (Proportional Integral Dervative) is provided with control comparison was made. MATLAB/Simulink simulations performed unmanned vehicles used for target tracking in robotic camera control with the system were investigated in the MPC.

Equalization of nonlinear communication channel based on Hammerstein block structure

The amplifiers that are used on communication systems in order to increase the productivity, are worked on the nonlinear region. Therefore, digital communication channel can be defined as a Wiener block structure that contains a linear dynamic system and a non-linear static block. In this study, the nonlinear channel equalization problem, a Wiener block structured communication channel is tried to equalize by using a Hammerstein block structure. In order to do that performance of the suggested approach is investigated with LMS and RLS algorithms. The convergence rates of these adaptive algorithms are compared on the real valued data transmission so that LMS algorithm is observed slower convergence but less complex, RLS algorithm is observed much faster convergence rate.

Identification of wiener systems using reduced complexity volterra models

Abstract In this paper we study the identification problem of single-input, single-output Wiener systems with polynomial nonlinearities. Wiener systems can be represented by a cascade of a dynamic linear subsystem followed by a static nonlinearity. Our approach is to use a reduced complexity Volterra model structure called fixed pole expansion technique (FPET) to estimate the products of the coefficients of the nonlinearity and the linear subsystems coefficients. We then present a method using the singular value decomposition to extract the coefficients of the non linearity and of the dynamic linear subsystem.

Modeling of three-axis gimbal system on unmanned air vehicle (UAV) under external disturbances

This study focuses on the modelling of 3 axis gimbal system with the RRR joint structure on the Unmanned Aerial Vehicle (UAV), which is autonomously moving for the target tracking, based on experimental input (motor velocities) and output (end effector position) data. The fact that UAVs move in a certain direction and that the camera on the end effector of the gimbal system on it is adhere to the correct target attracts many researchers. The transfer function of the 3 axis gimbal system is obtained by linearly structured OE-Output Error model using experimentally obtained data under different external disturbance effects. Model degree is determined and data set based verification is applied. Also, the performance is compared by examining the effect of external disturbance in the transfer function obtained.

Ultrasonic signal delay determination for distance estimation in underwater space

Reverberation and multipath propagation afîect the accuracy of time of flight (TOF) estimation in confined underwater medium. In this paper, time delay has been estimated by obtaining the transmitted signal and first echo signal from measured signal acquised by using a wideband transducer with 5 MHz central frequency. Cross-correlation (CC) and generalized cross-correlation (GCC) methods have been applied to the obtained signals and their performances have been compared. The results show that GCC method has better performance for time delay estimation in confined underwater medium where multipath propagation and reverberation are severe.

Prediction of wind speed with non-linear autoregressive (NAR) neural networks

In this study, the wind speed prediction model is created that gives a minimum error for different hidden layer neuron numbers and delay step numbers. Using the one-minute time series, the prediction of the next wind speed is performed with the NAR neural network model. The predicted values of wind speed obtained are compared with predicted values of wind speed obtained with filter methods. For different window functions and lengths, wind speed prediction is made using filters with different weight coefficients. For the number of hidden layer neurons is 14 and the number of delay steps is 10, MAE, MSE and RMSE values are calculated as 0.0315, 0.0019, 0.0445, respectively, with NAR neural network. It is seen that the proposed method for the wind speed dataset has a higher prediction performance than thefilter methods.

The effect of the ring transducer system in ultrasonic imaging

The spatially limited plane (SLP) wave can be created by exciting the ring transducer elements with different amplitudes and at different times. Although the ring transducer initially worked well, many transducer elements have become inoperative, due probably to service life and material life. The result of these bad elements is artifacts in the resulting spatially limited plane waves. In this study, the effects of bad elements of ring transducer system (RTS) which is used to obtain high quality images by using inverse scattering techniques in formation of the SLP wave are investigated. Also, the weighting of operative elements is examined in order to compensate the bad ones. Results show that loses in the generated SLP wave can be compensated with correcting the artifacts of bad elements by using elements adjacent to the inoperative ones.