Nikos A. Aspragathos

Nikos A. Aspragathos
University of Patras | UP · Department of Mechanical Engineering and Aeronautics

PhD

About

273
Publications
67,660
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3,455
Citations
Additional affiliations
January 1980 - present
University of Patras
Position
  • Professor (Full)

Publications

Publications (273)
Article
Full-text available
A method for determining the optimal position of a robotic task within a manipulator’s workspace considering the minimum singularity free paths in joint space in order to achieve a high kinematic performance is presented. The selected performance criterion was the minimization of the joint velocities during task execution under a given end effector...
Article
Full-text available
This paper introduces two type-agnostic and fabric-agnostic methods for robotic unfolding of garments. In the first method, a new path extraction procedure for unfolding the upper layer of a garment’s fold, which is located on a working table, with one robotic arm is proposed. The path is extracted using learning by demonstration methods and it is...
Article
Full-text available
This paper proposes a hierarchical visual architecture for perceiving garments’ configuration independently from their type for the robotic unfolding task. Special focus is given on the decomposition of folded configurations into low- and high-level features. The low-level features comprise junctions of edges, which act as localized indicators of t...
Article
Full-text available
The determination of the optimal position of a robotic task within a manipulator’s workspace is crucial for the manipulator to achieve high performance regarding selected aspects of its operation. In this paper, a method for determining the optimal task placement for a serial manipulator is presented, so that the required joint torques are minimize...
Article
Full-text available
In this manuscript, a recurrent neural network is proposed for variable admittance control in human-robot cooperation tasks. The virtual damping and the virtual inertia of the designed robot’s admittance controller are adjusted online and simultaneously. A Jordan recurrent neural network is designed and trained for this purpose. The network is indi...
Article
Full-text available
In this paper, an approach for the evaluation of human-robot collaboration towards high performance is introduced and implemented. The human arm and the manipulator are modelled as a closed kinematic chain and the proposed task performance criterion is used based on the manipulability index of this chain. The selected task is a straight motion in w...
Article
Full-text available
This paper proposes an approach for variable admittance control in human-robot collaboration depending on the online training of neural network. The virtual inertia is an important factor for the system stability, and its tuning is investigated in improving the human-robot cooperation. The design of the variable virtual inertia controller is analyz...
Article
Full-text available
Human–robot interaction (HRI) is one of the most rapidly growing research fields in robotics and promising for the future of robotics technology. Despite the fact that numerous significant research results in HRI have been presented during the last years, there are still challenges in several critical topics of HRI, which could be summarized as: (i...
Chapter
This paper presents the dynamic evaluation of Serial Metamorphic Manipulator structures considering inertia characteristics. The basic structural components are presented and the proposed representation is discussed. In order to investigate the ability of a metamorphic structure to reduce mass-coupling errors and achieve dynamic isotropy conditions...
Chapter
Full-text available
In this paper an approach for a human robot interface (HRI) is proposed, based on electromyographic (EMG) signals interpretation, utilizing a rule-based expert system. The developed approach uses the EMG signals during the motion of the elbow and wrist joint of a human for moving the arm on a plane. After processing, these signals are passed throug...
Article
Full-text available
In this paper, a multilayer feedforward Neural Network based approach is proposed for human-robot collision detection taking safety standards into consideration. One multi-output neural network is designed and trained using data from the coupled dynamics of the manipulator with and without external contacts to detect unwanted collisions and to iden...
Article
Full-text available
This paper proposes a classification of all non-isomorphic anatomies of an orthogonal metamorphic manipulator according to the topology of workspace considering cusps and nodes. Using symbolic algebra, a general kinematics polynomial equation is formulated, and the closed-form parametric solution of the inverse kinematics is obtained for the coming...
Chapter
In this paper, a gain scheduled PID force feedback controller of a manipulator is designed and implemented for the robotized sewing of fabrics, using a commercial sewing machine. The proposed manipulator controller should keep a constant tension of the fabric, to achieve high quality of cloths seams, as the length of the fabric is shortened along t...
Chapter
Full-text available
In this paper, a feedforward neural network is trained towards the generalisation of the inverse kinematics of a 3R metamorhic manipulator with one pseudojoint. A two hidden-layered network is trained with data produced by several anatomies of the metamorphic manipulator and tested to an unforeseen anatomy. The data are separated to aspects per ana...
Chapter
The purpose of this paper is to present a mission design approach for a service mobile manipulator which is moving and manipulating objects in partly known indoor environments. The mobile manipulator is requested to pick up and place objects on predefined places (stations). The proposed approach is based on the Bump-Surface concept to represent rob...
Article
In this paper, an approach is proposed for the simultaneous manipulation of multiple hexagonal and square plastic-glass type microparts that are positioned randomly on a smart platform (SP) using electrostatic forces applied by the suitable activation of circular conductive electrodes. First, the statics analysis of a micropart on the SP is present...
Chapter
Full-text available
The importance of forest environment in the perspective of the biodiversity as well as from the economic resources which forests enclose, is more than evident. Any threat posed to this critical component of the environment should be identified and attacked through the use of the most efficient available technological means. Early warning and immedi...
Article
Full-text available
In this paper, a multilayer feedforward neural network is designed and trained, for human-robot collisions detection, using only the intrinsic joint position sensors of a manipulator. The topology of one neural network is designed considering the coupled dynamics of the robot and trained, with and without external contacts, by Levenberg-Marquardt a...
Preprint
Full-text available
In this paper methods are developed for the manipulation of hexagonal microparts made of plexiglass on a programmable platform with embedded circular conductive electrodes. With the activation of the platform electrodes attractive forces are applied to the micropart's electrodes in order to be dragged to a new equilibrium position. Two different la...
Chapter
Full-text available
In this paper a 3R orthogonal metamorphic manipulator with two pseudo-joints is investigated concerning its cuspidal anatomies. The classification of the anatomies derived by the metamorphic serial structure is achieved by solving the system of polynomials with an eliminating technique based on Groebner Basis. The metamorphic parameters space is di...
Chapter
In this paper, a multilayer neural network based approach is proposed for the human-robot collisions detection during the motions of a 2-DoF robot. One neural network is designed and trained by Levenberg-Marquardt algorithm to the coupled dynamics of the manipulator joints with and without external contacts to detect unwanted collisions of the huma...
Chapter
A programmable platform and plastic hexagonal microparts, both with embedded circular conductive electrodes are studied. Two layouts for the allocation of the electrodes on the hexagons are proposed, according to which, activation algorithms are introduced for the horizontal and vertical displacement of the hexagonal microparts on the platform. The...
Chapter
Full-text available
This paper presents a mechatronic evaluation of forest fire monitoring systems based on UAV. To begin with, a mapping of the requirements to the mechatronic abilities, which should be embodied by these systems, is presented. The enabling technologies that support these abilities are briefly reported. The evaluation of these systems’ architectural s...
Chapter
A layer extraction method aiming at robotic garment unfolding is presented in this paper. Utilizing depth sensor input, the layer detection is achieved through a depth first algorithm and a simple perceptron. An action space based on the edges detected on the garment and their features restricts the complexity of the algorithm and accelerates the d...
Article
Full-text available
Wind aware path planning is essential towards the development of autonomous quadcopters (UAVs) which will be able to fly efficiently in outdoor environments. In this paper, the wind formation and quadcopter kinematics are presented so as to provide cost functions for A* based on distance and wind information. Furthermore, a collision checking metho...
Article
Full-text available
In this article, a method for microparts parallel manipulation with electrostatic forces, applied by conductive electrodes embedded on a Programmable “Smart Platform”, is introduced. The design of the platform and the layout of the electrodes underneath the rectangular microparts with respect to the platform’s geometry are presented. The electrosta...
Conference Paper
Full-text available
In this paper, a method for variable admittance control in human-robot cooperation is proposed. A multilayer feedforward neural network is designed using the Cartesian velocity of the robot and the applied force by the operator as its inputs to modify online the virtual damping of the admittance controller. The neural network is trained online usin...
Data
In this video, a proposed trained neural network for adjusting the virtual damping of the admittance controller is compared with three different constant virtual damping coefficients in terms of three criteria; the required effort to move the robot from point to point, the overall completion time and the accuracy achieved in reaching the target poi...
Conference Paper
Full-text available
Metamorphic manipulators are gaining increasing research interest, due the capability of altering their anatomy in order to improve their performance in the execution of a given task. In this paper, an optimization method is presented for the determination of the best anatomy of a metamorphic manipulator for the execution of a robotic task. The pro...
Conference Paper
Full-text available
A programmable platform and plastic hexagonal microparts, both with embedded circular conductive electrodes are studied. Two layouts for the allocation of the electrodes on the hexagons are proposed, according to which, activation algorithms are introduced for the horizontal and vertical displacement of the hexagonal microparts on the platform. The...
Chapter
Full-text available
In this paper, a multilayer neural network based approach is proposed for the human-robot collisions detection during the motions of a 2-DoF robot. One neural network is designed and trained by Levenberg-Marquardt algorithm to the coupled dynamics of the manipulator joints with and without external contacts to detect unwanted collisions of the huma...
Presentation
Full-text available
A multi-layer neural network based approach is proposed for the human-robot collisions detection during the motions of a 2-DoF robot. One neural network is designed and trained by Levenberg-Marquardt algorithm to the coupled dynamics of the manipulator joints with and without external contacts to detect unwanted collisions of the human operator wit...
Conference Paper
Full-text available
In this paper, a 3-finger gripper is developed for grasping fabrics that are folded or unfolded. Its design is based on the investigation of human fingers’ movements in grasping a piece of fabric that is laid on a table and it is conceptualized using the theory of cam-follower design. The concept, the design and the prototype of the gripper are pre...
Article
Full-text available
In this paper, an approach based on multilayer neural network is proposed for human-robot collisions detection. The neural network is trained by Levenberg-Marquardt algorithm to the dynamics of the robot with and without external contacts to detect unwanted collisions of the human operator with the robot using only the proprietary position and join...
Article
Full-text available
In this paper, a new mechatronics index is proposed for the evaluation of the alternatives in the conceptual design phase. The criteria aggregated to the index are acquired mostly by the collective knowledge presented in the Multi Annual Roadmap for robotics in Europe and adapted by considering the recent advancements in mechatronics. The mathemati...
Article
Full-text available
This paper addresses the problem of distinguishing unexpected collisions from voluntary contacts during human-robot collaboration. The objective of this work is to improve the safety of the operator during the interaction with the robot. Based on the observation that cooperation forces present different frequency characteristics from collisions, a...
Conference Paper
Full-text available
The selection of the Jacobian matrix and the performance measure affects the results in optimization problems such as the placement of a task in the workspace of the robot. In this paper, a comparative study of three performance measures that are produced by alternative determinations of the Jacobian matrix is presented. As it is shown in the illus...
Article
In this paper a method is proposed for finding the complete number of the inverse kinematic solutions by using of Artificial Neural Networks (ANN). The training data, which are generated using the Halton quasi-random sequence, are clustered into aspects by using the proposed new metric function for the joint configuration space. Application of the...
Conference Paper
Full-text available
Line following robots are becoming increasingly popular both in industrial and in domestic applications. In these real world environments, noisy or inaccurate measurements lead to ambiguous conclusions about the robot's state relative to the path. In this paper, a Finite State Machine is introduced that detects irregularities in the measurements fr...
Article
Full-text available
The vibration control problem of flexible objects manipulated by industrial robots under normal production conditions is investigated. This is an important problem as the quick and precise manipulation of such objects may reduce the production's lead time and thus its cost. The problem is in the present study tackled for flexible beams via a novel...
Conference Paper
In this paper a two-stage approach is introduced for optimum path planning of a team of autonomous vehicles in an environment cluttered with obstacles. The vehicles are requested to move in formation from an initial point to a final point. The Bump-Surface concept is used for the representation of the environment while the formation of the vehicles...
Conference Paper
Full-text available
This study addresses the problem of vibration control of a flexible metallic beam which is transferred by an industrial robot. The control is designed in a special Matlab/Simulink synthetic environment that is founded on AutoRegressive with eXogenous (ARX) stochastic modelling of the robot-beam system through exclusively experimental data. Based on...
Article
Full-text available
Physical human-robot cooperation is a rapidly emerging field that aims to support humans in industrial and everyday environments. In order to facilitate effective cooperation, the kinematic and dynamic capabilities of the robot must be taken into account, such as the ability of the end-effector to move and apply forces to all directions. An online...
Article
In this paper, methodologies are presented for the development of intelligent robot systems for the manipulation of linear and sheet like objects with low and/or very low bending rigidity. In the introduction the non-rigid objects are defined and classified considering their shape, bending rigidity and extensibility. The industrial and service appl...
Article
Full-text available
In this paper, a method for evaluating robots as parts of a CPPS based on their abilities is presented. The relationship between the CPPS characteristics and robot abilities is determined. The minimum level of robot abilities is determined in order to have a positive influence on CPPS. The proposed mapping is used to evaluate the anatomy of three t...
Conference Paper
Full-text available
In this paper, a comparative study of two methods are presented to determine the forward kinematics and Jacobian matrix for any serial manipulator, based on product of exponentials formula and unit dual quaternion algebra. This comparison is qualitative and particularly quantitative taken into account computational costs and memory requirements tha...
Article
Full-text available
Purpose: This paper presents the development of a knowledge based system for the detection of gait phases based on EMGs from muscles of the lower limb. Methods: An empirical analysis of the EMG characteristics for the most representative muscle of every muscle group concerning their suitability for the gait phase detection is presented. The same ap...
Chapter
Full-text available
This chapter presents a software system based on smart cards technology for recording, monitoring and studying patients of any surgery specialty (General Surgery, Orthopedics, Neurosurgery, etc.). The system is also suitable for the computerization of any surgery specialty clinic and the respective surgical material repositories. Dynamic customizat...
Chapter
In this paper a method for approximating the inverse kinematics solutions (IKS) of a six (6) DoF manipulator using neural networks is proposed. First, the partitioning of the configuration space, based on the singularity locus is presented in order to define the training data set for each IKS. Then, a constructive technique for determining the mini...
Chapter
Full-text available
This paper presents a method for the task based determination of the suboptimal anatomy of a metamorphic manipulator considering tasks with varying orientation of the end-effector. A performance index representing the orientation dexterity along the rotational motion of the end-effector based on max–min of the rotational manipulability is formulate...
Conference Paper
Full-text available
In this paper, the co-activation level of the arm muscles is used as an indication of the end-point stiffness for improving human-robot cooperation. A variable admittance controller is proposed to adjust the virtual damping in real time by measuring the operator's muscle activation by means of surface EMG. An experimental user study is conducted th...
Conference Paper
Full-text available
The emerging field of physical human-robot interaction raises the need to distinguish collisions over intended contacts in order to guarantee safe and seamless interaction. In this paper, a novel contact distinction method is proposed that monitors the externally applied forces/torques and is able to distinguish unexpected collisions from intended...
Conference Paper
Full-text available
A programmable platform with conductive electrodes, for the manipulation of microparts, is studied. A new design for a flexible platform is proposed expanding our previous work. For the new platform design the horizontal electrostatic force applied by an activated platform electrode to the corresponding micropart electrode is determined, using capa...
Chapter
In this paper, a method for dividing the training data as well as training MLP systems to obtain the multiple solutions of IKP of regular manipulators is presented. The sets of training data for each system are strictly defined using the concept of uniqueness domains. The training data are obtained by the forward kinematics and the sign of the dete...
Article
A method for the fast approximation of dexterity indices for given underwater vehicle-manipulator systems (UVMS) configurations is presented. Common underwater tasks are associated with two well-known dexterity indices and two types of neural networks are designed and trained to approximate each one of them. The method avoids the lengthy calculatio...
Conference Paper
In this paper a two-stage approach is introduced for optimum path planning of a team of autonomous vehicles in an environment cluttered with obstacles. The vehicles are requested to move in formation from an initial point to a final point. The Bump-Surface concept is used for the representation of the environment while the formation of the vehicles...
Conference Paper
Full-text available
This study addresses the problem of vibration control of a flexible metallic beam which is transferred by an industrial robot. The control is designed in a special Matlab/Simulink synthetic environment that is founded on AutoRegres-sive with eXogenous (ARX) stochastic modelling of the robot-beam system through exclusively experimental data. Based o...