Papers by Kimon Valavanis
IEEE Transactions on Robotics and Automation, 2004
A supervisory controller is derived for scheduling (single/multiple-part-type, reentrant) product... more A supervisory controller is derived for scheduling (single/multiple-part-type, reentrant) production networks. The supervisory controller is used to tune a set of lower level distributed fuzzy control modules that reduce work-in-process (WIP) and synchronize the production system's operation. The overall production-control system is viewed as a two-level surplus-based system with the overall control objective to keep the WIP and cycle time as low as possible, while maintaining quality of service by keeping backlog to acceptable levels. The production rate in each production stage is controlled to satisfy demand, avoid overloading, and eliminate machine starvation or blocking. The system's improvement is demonstrated using a set of performance measures. Extensive simulation results show that the supervisory controller, when compared with the single-level distributed fuzzy controllers reduces WIP and cycle time while keeping backlog to acceptable levels.
... The last set of measurements is related to the vehicle variables by the set of following equa... more ... The last set of measurements is related to the vehicle variables by the set of following equations: () () 0 xt t Rλ λ = q q (6 ... A Kalman filter (KF) is derived to estimate the true values of orientation, angular rate, linear acceleration, velocity, position and errors associated with them. ...
Journal of Intelligent and Robotic Systems, 2002
Agility metrics are difficult to define in general, mainly due to the multidimensionality and vag... more Agility metrics are difficult to define in general, mainly due to the multidimensionality and vagueness of the concept of agility itself. In this paper, a knowledge-based framework is proposed and presented as a candidate solution for the measurement and assessment of manufacturing agility. Given an enterprise, in order to calculate its overall agility, a set of quantitatively defined agility parameters is proposed and grouped into production, market, people and information infrastructures. The combined, resulting, measure incorporates the individual and grouped infrastructure agility parameters and their variations into one calculated value of the overall agility. The necessary expertise used to quantitatively determine and measure individual agility parameters is represented via fuzzy logic terminology that allows for human-like knowledge representation and reasoning. An example demonstrates the feasibility and applicability of the proposed approach.
Design modifications on the controller of the PUMA- 600 arm are required to apply modern control ... more Design modifications on the controller of the PUMA- 600 arm are required to apply modern control techniques in real-time. These modifications are performed on the computer-level and the joint control level of the PUMA controller. Real-time closed loop control of the arm is thus made possible. The paper compares the performance of various control algorithms in real-time and by simulation.
IEEE Transactions on Systems, Man, and Cybernetics, 1990
multiple types of places, multiple classes of tokens and multiple arcs is proposed. It is utilize... more multiple types of places, multiple classes of tokens and multiple arcs is proposed. It is utilized for the hierarchical modeling of flexible manufacturing systems ensuring ( I priori that the extended Petri net system model obtained is live, bounded, consistent and error-free. The proposed methodology views the operation of the flexible manufacturing system as a process that is decomposed into operations with specified precedence relations. For each operation the required resources are identified and based on them, the overall system is decomposed into a set of finite subsystems. The operation of each subsystem is modeled as an event-graph representing a single resource activity cycle. The extended Petri net system model is synthesized from these component nets based on certain synthesis rules. A software package has been developed to simulate the execution of the obtained extended Petri net model.
IEEE Transactions on Systems, Man, and Cybernetics, 2003
An evolutionary algorithm based framework, a combination of modified breeder genetic algorithms i... more An evolutionary algorithm based framework, a combination of modified breeder genetic algorithms incorporating characteristics of classic genetic algorithms, is utilized to design an offline/online path planner for unmanned aerial vehicles (UAVs) autonomous navigation. The path planner calculates a curved path line with desired characteristics in a three-dimensional (3-D) rough terrain environment, represented using B-spline curves, with the coordinates of its control points being the evolutionary algorithm artificial chromosome genes. Given a 3-D rough environment and assuming flight envelope restrictions, two problems are solved: i) UAV navigation using an offline planner in a known environment, and, ii) UAV navigation using an online planner in a completely unknown environment. The offline planner produces a single B-Spline curve that connects the starting and target points with a predefined initial direction. The online planner, based on the offline one, is given on-board radar readings which gradually produces a smooth 3-D trajectory aiming at reaching a predetermined target in an unknown environment; the produced trajectory consists of smaller B-spline curves smoothly connected with each other. Both planners have been tested under different scenarios, and they have been proven effective in guiding an UAV to its final destination, providing near-optimal curved paths quickly and efficiently.
IEEE Transactions on Systems, Man, and Cybernetics, 1999
Describes a visual monitoring system that performs scene segmentation based on color and texture ... more Describes a visual monitoring system that performs scene segmentation based on color and texture information. Color information is combined with texture, and corresponding segmentation algorithms are developed to detect and measure changes (loss/gain) in a given scene or environment over a period of time. The xyY color space is used to represent the color information. The two chromaticity coordinates (x, y) are combined into one, thus providing the chrominance (spectral) part of the image, while Y describes the luminance (intensity) information. The proposed color/texture segmentation system processes luminance and chrominance separately. Luminance is processed in three stages: filtering, smoothing and boundary detection. Chrominance is processed in two stages: histogram multi-thresholding and region growing. Two or more images may be combined at the end in order to detect scene changes, using logical pixel operators. As a case study, the methodology is used to determine wetland loss/gain. For comparison purposes, results in both the xyY and HIS (hue, intensity, saturation) color spaces are presented
As mobile robot teams become more complex, it is necessary to develop a control architecture to m... more As mobile robot teams become more complex, it is necessary to develop a control architecture to manage the resources present in the team. The Distributed Field Robot Architecture (DFRA) is a distributed, object-oriented imple- mentation of the SFX hybrid robot architecture that allows for dynamic discovery and acquisition of robot resources and the seamless integration of humans and artificial agents
IEEE Transactions on Systems, Man, and Cybernetics, 1998
This paper presents an analytical model of a flat surfaced robotic gripper designed to automate t... more This paper presents an analytical model of a flat surfaced robotic gripper designed to automate the process of reliable, rapid and distortion-free limp material handling. The designed gripper prototype is integrated with an industrial robot manipulator. The gripper geometry and its grasp stability are justified. Performance of the overall system is experimentally tested, based on a set of industry dictated operational constraints. It is found that the gripper system has high reliability, grasp stability, and that it is capable of rapid rates of manipulation
Journal of Intelligent and Robotic Systems, 2004
A fuzzy logic based general purpose modular control architecture is presented for underwater vehi... more A fuzzy logic based general purpose modular control architecture is presented for underwater vehicle autonomous navigation, control and collision avoidance. Three levels of fuzzy controllers comprising the sensor fusion module, the collision avoidance module and the motion control module are derived and implemented. No assumption is made on the specific underwater vehicle type, on the amount of a priori knowledge of the 3-D undersea environment or on static and dynamic obstacle size and velocity. The derived controllers account for vehicle position accuracy and vertical stability in the presence of ocean currents and constraints imposed by the roll motion. The main advantage of the proposed navigation control architecture is its simplicity, modularity, expandability and applicability to any type of autonomous or semi-autonomous underwater vehicles. Extensive simulation studies are performed on the NPS Phoenix vehicle whose dynamics have been modified to account for roll stability.
Page 1. Unmanned Ground Vehicle Swarm Formation Control Using Potential Fields Laura Barnes*, Mar... more Page 1. Unmanned Ground Vehicle Swarm Formation Control Using Potential Fields Laura Barnes*, MaryAnne Fields** and Kimon Valavanis* * University of South Florida/Department of Computer Science and Engineering ...
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Papers by Kimon Valavanis