Ahmet Bugra Koku

Real-time hardware-in-the-loop simulation of electrical machine systems using FPGAs

This study focuses on the development an integrated software and hardware platform that is capable of performing real-time simulation of dynamic systems, including electrical machinery, for the purpose of hardware-in-the-loop simulation (HILS). The system to be controlled is first defined using a block diagram editor. The defined model is then compiled and downloaded onto an FPGA (“Field Programmable Gate Array”) based hardware platform, which is to interface with the controller under test and carry out the simulation in real-time. The full paper will elaborate the characteristics of this novel HILS platform.

Evaluation of egocentric navigation methods

In describing routes humans make use of egocentric references to landmarks. In this paper two different egocentric navigation algorithms are introduced and possible variations of these algorithms are compared. These algorithms make use of solely angular distribution information of landmarks around the robot. Possible improvements and uses of these algorithms are discussed. In the evaluation of these algorithms computer simulations are used. The result of this work is expected to provide pointers for the ongoing research which aims to address navigation of robots based on qualitative interaction between humans and robots.

Evaluation of haptic feedback cues on vehicle teleoperation performance in an obstacle avoidance scenario

Teleoperation of an unmanned vehicle is a challenging task for human operators especially when the vehicle is not within line of sight. Lack of situational awareness and increased workload due to limited perception channels result in degraded task performance. If these teleoperation missions are human-critical then it becomes more important to improve the operator performance by decreasing workload and improving situational awareness. In this paper, a new teleoperation interface which provides force feedback based on the path generated by an obstacle avoidance algorithm is presented. The purpose of this interface is to overcome the difficulties imposed by limited field of view and lack of situational awareness. Teleoperation tests are performed to verify that haptic feedback generated from the dynamic obstacle information of the environment improves teleoperation performance by supporting the operator and decreasing the workload.

Direct command generation methods for servo-motor drives

This study focuses on advanced direct command generation paradigms that can be easily incorporated to modern servo-motor drive systems. As an alternative to conventional methods, two new command generation techniques are proposed in this paper. In the first method, higher-order differences of a given trajectory (i.e. position) are computed and the resulting data are compressed via lossless data compression techniques. Besides conventional approaches, a novel compression algorithm is also introduced in the paper. With respect to the second method, the command trajectory is first divided into segments according to the inflection points. The segments are then approximated using various polynomial techniques. The sequence originating from modeling error is included to the generated series. These two command generation techniques are then implemented using Field Programmable Gate Arrays (FPGAs) and their performances are evaluated according to the resources used in FPGAs and the speed of computation.

Performance evaluation of different real-time motion controller topologies implemented on a FPGA

This paper presents a comprehensive comparison of several real-time motion controller topologies implemented on a field programmable gate array (FPGA). Controller topologies are selected as proportional-integral-derivative controller with command feedforward, sliding mode controller, fuzzy controller, and a hysteresis controller. Controllers and other necessary modules are developed using Verilog HDL and they are implemented on a ML505 development board with a Xilinx Virtex-5 FPGA chip. In order to take full advantage of FPGA and to provide a more accurate comparison, an (soft-core) embedded processor is not employed in the design. The developed modules, which include PWM generator, quadrature encoder decoder, velocity estimator, reference profile generator etc, are fully tailored for the application. To perform the necessary calculations for certain controller topologies, an open-core floating point unit (FPU) is also adopted to the design. The performances of the aforementioned controllers are rigorously evaluated via a hardware-in-the-loop simulation of a field-oriented induction motor system.

i-RoK: A human like robotic head

In order to explore issues of human-robot interaction in a social context, we have constructed a humanoid robotic head called i-RoK. This paper focuses on the study and design of the anthropomorphic head robot developed at the Mechanical Engineering Department of Middle East Technical University. The robot has a total of 8 mechanical degrees of freedom. This allows the robot to mimic the same movements performed by human head. We discuss major design issues of the developmental head and the design characteristics of the robot, i-RoK, in this paper.

Novel solutions for Global Urban Localization

In this study, novel solutions to Global Urban Localization problem is proposed and examined rigorously. Classical approaches including Particle Filter, mixture of Gaussians, as well as novel solutions like Viterbi Algorithm and differential evolution are evaluated. The contribution of this paper is twofold: The Viterbi algorithm is extended by exploiting the structure of the problem at hand that is the states are partially connected temporally. Differential evolution is modified by taking into account the covariance matrix of states. Thus states encoded in genes are only allowed to interact locally within the region described by covariance matrix. This prevents the differential evolution from getting trapped into false maxima in the early stages of optimization. Finally, it is demonstrated with extensive experiments that solution of Global Urban Localization problem is possible.

Knowledge-sharing techniques for Egocentric Navigation

Teams of humans and robots working together can provide effective solutions to problems. In such applications, effective human-robot teaming relies on being able to communicate information about the current perception or understanding of the environment. In this paper, human-robot teaming on navigational tasks is discussed. The role of the human user will be to specify the goal point(s) for the robot, and also to interact with the robot in the event of perceptual errors. A novel navigation method, Egocentric Navigation (ENav), has been developed based on egocentric representations. In this paper, two knowledge sharing methods are described which exploit the characteristics of ENav. In the first method, robots share Landmark EgoSpheres, and in the second method the robot shares it Sensory EgoSphere with the human user for visual perception correction.

A novel approach for robot homing

Although metric navigation techniques have been widely adapted in robot navigation, some powerful qualitative navigation methods have been proposed to achieve navigation. These methods do not require strict metric measures or presence of metric maps. This paper briefly introduces such qualitative navigation techniques and introduces a novel approach for qualitative robot navigation. Comparison of this method to some existing ones is given and performance analysis is presented. This technique requires less amount of information and its performance is comparable to other similar methods.

A new hardware-in-the-loop simulator for CNC machine applications

This study focuses on an integrated software and hardware platform that is capable of performing (real-time/non-real-time) hardware-in-the-loop simulation of dynamic systems, including electrical machinery, CNC machine tools. In this approach, once the dynamics of the plant to be controlled is defined via C++ language, the resulting code is cross-compiled automatically on a PC. Executable files along with the necessary drivers are downloaded onto the composite hardware platform that consists of a Field Programmable Gate Array (FPGA) along with a powerful DSP board. The paper elaborates the overall performance of this novel hybrid HILS platform on a CNC machine tool application.