Kostas J Kyriakopoulos | National Technical University of Athens (original) (raw)
Papers by Kostas J Kyriakopoulos
Computers and Electronics in Agriculture, 2001
The equations of motion for a system of multiple mobile manipulators that handle a deformable obj... more The equations of motion for a system of multiple mobile manipulators that handle a deformable object during an agricultural task are developed. The model is based on Kane's approach. The imposed kinematic constraints are included and incorporated into the dynamics. Sufficient conditions for avoiding tipping over of the mechanisms are also provided. The deformable nature of the object can easily accommodate a variety of agricultural products and the analysis allows for the inclusion of specific handling limitations in order for the objects not to be damaged during manipulation.
International Journal of Systems Science, 1994
The equations of motion for a system of multiple mobile manipulators that handle a deformable obj... more The equations of motion for a system of multiple mobile manipulators that handle a deformable object during an agricultural task are developed. The model is based on Kane's approach. The imposed kinematic constraints are included and incorporated into the dynamics. Sufficient conditions for avoiding tipping over of the mechanisms are also provided. The deformable nature of the object can easily
53Rd Ieee Conference on Decision and Control, Dec 1, 2014
Proceedings Ieee International Conference on Robotics and Automation, 2013
This work proposes a motion planning method based on the construction of a roadmap connecting the... more This work proposes a motion planning method based on the construction of a roadmap connecting the critical points of a potential field or a distance function. It aims to overcome the limitation of potential field methods due to local minima caused by concave obstacles. The roadmap is incrementally constructed by a two-step procedure. Starting from a minimum, adjacent saddle-points are found using a local saddlepoint search method. Then, the new saddle-points are connected to the minima by gradient descent. A numerical continuation algorithm from the computational chemistry literature is used to find saddle-points. It traces the valleys of the potential field, which are gradient extremal paths, defined as the points where the gradient is an eigenvector of the Hessian matrix. The definition of gradient bisectors is also discussed. The presentation conclude simulations in cluttered environments.
2013 Ieee 13th International Conference on Rehabilitation Robotics, Jun 1, 2013
A learning scheme based on Random Forests is used to discriminate the task to be executed using o... more A learning scheme based on Random Forests is used to discriminate the task to be executed using only myoelectric activity from the upper limb. Three different task features can be discriminated: subspace to move towards, object to be grasped and task to be executed (with the object). The discrimination between the different reach to grasp movements is accomplished with a random forests classifier, which is able to perform efficient features selection, helping us to reduce the number of EMG channels required for task discrimination. The proposed scheme can take advantage of both a classifier and a regressor that cooperate advantageously to split the task space, providing better estimation accuracy with task-specific EMG-based motion decoding models, as reported in [1] and . The whole learning scheme can be used by a series of EMG-based interfaces, that can be found in rehabilitation cases and neural prostheses.
Human-robot control interfaces have received increased attention during the past decades. With th... more Human-robot control interfaces have received increased attention during the past decades. With the introduction of robots in everyday life, especially in providing services to people with special needs (i.e., elderly, people with impairments, or people with disabilities), there is a strong necessity for simple and natural control interfaces. In this paper, electromyographic (EMG) signals from muscles of the human upper limb are used as the control interface between the user and a robot arm. EMG signals are recorded using surface EMG electrodes placed on the user's skin, making the user's upper limb free of bulky interface sensors or machinery usually found in conventional human-controlled systems. The proposed interface allows the user to control in real time an anthropomorphic robot arm in 3-D space, using upper limb motion estimates based only on EMG recordings. Moreover, the proposed interface is robust to EMG changes with respect to time, mainly caused by muscle fatigue or adjustments of contraction level. The efficiency of the method is assessed through real-time experiments, including random arm motions in the 3-D space with variable hand speed profiles.
Advanced Manufacturing, 2000
2008 Ieee Rsj International Conference on Intelligent Robots and Systems, 2008
There is a great effort during the last decades towards building robotic devices that are worn by... more There is a great effort during the last decades towards building robotic devices that are worn by humans. These devices, called exoskeletons, are used mainly for support and rehabilitation, as well as for augmentation of human capabilities. Providing a control interface for exoskeletons, that would guarantee comfort and safety, as well as efficiency and robustness, is still an issue. This paper presents a methodology for estimating human arm motion and force exerted, using electromyographic (EMG) signals from muscles of the upper limb. The proposed method is able to estimate motion of the human arm as well as force exerted from the upper limb to the environment, when the motion is constrained. Moreover, the method can distinguish the cases in which the motion is constrained or not (i.e. exertion of force versus free motion) which is of great importance for the control of exoskeletons. Furthermore, the method provides a continuous profile of estimated motion and force, in contrast to other methods used in the literature that can only detect initiation of movement or intention of force. The system is tested in an orthosis-like scenario, during planar movements, through various experiments. The experimental results prove the system efficiency, making the proposed methodology a strong candidate for an EMG-based control scheme applied in robotic exoskeletons.
Proceedings 2006 Ieee International Conference on Robotics and Automation 2006 Icra 2006, May 15, 2006
A distributed feedback control architecture that guarantees collision avoidance and destination c... more A distributed feedback control architecture that guarantees collision avoidance and destination convergence for multiple sphere world holonomic agents is presented. The well established tool of Decentralized Navigation Functions is redefined to cope with the communication restrictions of the system. Each agent plans its actions without knowing the destinations of the others and the positions of those agents lying outside its sensing neighborhood. The stability properties of the closed loop system are checked via Lyapunov stability techniques for hybrid systems. The collision avoidance and goal convergence properties are verified through simulations. The key advantage of the proposed algorithm with respect to the previous ones is the significant decrease of computational load and its applicability to large scale groups.
Http Dx Doi Org 10 1163 156855302317413745, Apr 2, 2012
... independently of the motion of the other joints, where j = 1,...,m. Detailed modeling and acc... more ... independently of the motion of the other joints, where j = 1,...,m. Detailed modeling and accurate ... 1). This system becomes uniformly asymptotically stable to zero ae1, under the control input ... have used for the implementation of the simulations, is the model of Mitsubishi PA10-7C ...
Proceedings of the 48h Ieee Conference on Decision and Control Held Jointly With 2009 28th Chinese Control Conference, 2009
This paper presents a methodology for the decentralised control of multiple 3-dimensional nonholo... more This paper presents a methodology for the decentralised control of multiple 3-dimensional nonholonomic agents. The proposed control scheme is based on Navigation Functions and offers improvements compared to previous work of the authors in this field. The problem formulation is chosen to resemble Air-Traffic Management, where the safety guarantees provided by Navigation Functions based control strategies are very important. The linear velocity of each agent is maintained constant and equal to a desired value in most cases, while the azimuth and elevation control laws are engineered to reduce the required control effort. These qualitative improvements do not affect the collision avoidance characteristics of the control strategy. The performance and efficiency of our approach is supported by computer simulations presented in the paper.
2007 European Control Conference, 2007
We present a methodology to steer the end effector of a robotic manipulator, which is constrained... more We present a methodology to steer the end effector of a robotic manipulator, which is constrained in terms of joint rates, on the surface within the workspace. We develop controllers for stabilizing the end effector to a point, and for tracking a trajectory on this surface, while respecting the input constraints. We show that the resulting closed loop system is uniformly asymptotically stable and we verify our analytical development with computer simulations.
2008 Ieee Rsj International Conference on Intelligent Robots and Systems, 2008
Page 1. Visual Servo Control of an Underwater Vehicle Using a Laser Vision System George C. Karra... more Page 1. Visual Servo Control of an Underwater Vehicle Using a Laser Vision System George C. Karras and Kostas J. Kyriakopoulos Abstract This paper describes a position-based visual servo control scheme designed for an underwater vehicle. ...
2007 European Control Conference, Jul 1, 2007
... feedback scheme. A closed loop approach for single robot navigation was proposed by Koditsche... more ... feedback scheme. A closed loop approach for single robot navigation was proposed by Koditschek and Rimon [12], [27] in their seminal work. This navigation functions' framework handled single, point-sized, robot navigation. In ...
Proceedings Ieee International Conference on Robotics and Automation, May 19, 2008
We propose an inverse agreement control strategy for multiple nonholonomic agents that forces the... more We propose an inverse agreement control strategy for multiple nonholonomic agents that forces the team members to disperse in the workspace in a distributed manner. Both the cases of an unbounded and a circular bounded workspace are considered. In the first case, we show that the closed loop system reaches a configuration in which the minimum distance between any pair of agents is larger than a specific lower bound. It is proved that this lower bound coincides with the agents' sensing radius. In the case of a bounded workspace, the control law is modified to force the agents to remain within the workspace boundary throughout the closed loop system evolution. Moreover the proposed control guarantees collision avoidance between the team members. The results are supported through relevant computer simulations.
Proceedings of the Ieee Conference on Decision and Control, 2008
We present a novel control scheme for multiple non-holonomic vehicles under uncertainty, which ca... more We present a novel control scheme for multiple non-holonomic vehicles under uncertainty, which can guarantee collision avoidance while complying with constraints imposed on the vehicles. Dipolar Navigation Functions are used for decentralized conflict-free control, while Model Predictive Control is used in a centralized manner in order to ensure that the resulting trajectories remain feasible with respect to the constraints present and to optimize the performance objectives. The model used is chosen to resemble air traffic control problems, with some uncertainty introduced in the system. The efficiency of the control strategy is demonstrated by realistic simulations.
2012 American Control Conference (ACC), 2012
ABSTRACT
2013 Oceans San Diego, 2013
Computers and Electronics in Agriculture, 2001
The equations of motion for a system of multiple mobile manipulators that handle a deformable obj... more The equations of motion for a system of multiple mobile manipulators that handle a deformable object during an agricultural task are developed. The model is based on Kane's approach. The imposed kinematic constraints are included and incorporated into the dynamics. Sufficient conditions for avoiding tipping over of the mechanisms are also provided. The deformable nature of the object can easily accommodate a variety of agricultural products and the analysis allows for the inclusion of specific handling limitations in order for the objects not to be damaged during manipulation.
International Journal of Systems Science, 1994
The equations of motion for a system of multiple mobile manipulators that handle a deformable obj... more The equations of motion for a system of multiple mobile manipulators that handle a deformable object during an agricultural task are developed. The model is based on Kane's approach. The imposed kinematic constraints are included and incorporated into the dynamics. Sufficient conditions for avoiding tipping over of the mechanisms are also provided. The deformable nature of the object can easily
53Rd Ieee Conference on Decision and Control, Dec 1, 2014
Proceedings Ieee International Conference on Robotics and Automation, 2013
This work proposes a motion planning method based on the construction of a roadmap connecting the... more This work proposes a motion planning method based on the construction of a roadmap connecting the critical points of a potential field or a distance function. It aims to overcome the limitation of potential field methods due to local minima caused by concave obstacles. The roadmap is incrementally constructed by a two-step procedure. Starting from a minimum, adjacent saddle-points are found using a local saddlepoint search method. Then, the new saddle-points are connected to the minima by gradient descent. A numerical continuation algorithm from the computational chemistry literature is used to find saddle-points. It traces the valleys of the potential field, which are gradient extremal paths, defined as the points where the gradient is an eigenvector of the Hessian matrix. The definition of gradient bisectors is also discussed. The presentation conclude simulations in cluttered environments.
2013 Ieee 13th International Conference on Rehabilitation Robotics, Jun 1, 2013
A learning scheme based on Random Forests is used to discriminate the task to be executed using o... more A learning scheme based on Random Forests is used to discriminate the task to be executed using only myoelectric activity from the upper limb. Three different task features can be discriminated: subspace to move towards, object to be grasped and task to be executed (with the object). The discrimination between the different reach to grasp movements is accomplished with a random forests classifier, which is able to perform efficient features selection, helping us to reduce the number of EMG channels required for task discrimination. The proposed scheme can take advantage of both a classifier and a regressor that cooperate advantageously to split the task space, providing better estimation accuracy with task-specific EMG-based motion decoding models, as reported in [1] and . The whole learning scheme can be used by a series of EMG-based interfaces, that can be found in rehabilitation cases and neural prostheses.
Human-robot control interfaces have received increased attention during the past decades. With th... more Human-robot control interfaces have received increased attention during the past decades. With the introduction of robots in everyday life, especially in providing services to people with special needs (i.e., elderly, people with impairments, or people with disabilities), there is a strong necessity for simple and natural control interfaces. In this paper, electromyographic (EMG) signals from muscles of the human upper limb are used as the control interface between the user and a robot arm. EMG signals are recorded using surface EMG electrodes placed on the user's skin, making the user's upper limb free of bulky interface sensors or machinery usually found in conventional human-controlled systems. The proposed interface allows the user to control in real time an anthropomorphic robot arm in 3-D space, using upper limb motion estimates based only on EMG recordings. Moreover, the proposed interface is robust to EMG changes with respect to time, mainly caused by muscle fatigue or adjustments of contraction level. The efficiency of the method is assessed through real-time experiments, including random arm motions in the 3-D space with variable hand speed profiles.
Advanced Manufacturing, 2000
2008 Ieee Rsj International Conference on Intelligent Robots and Systems, 2008
There is a great effort during the last decades towards building robotic devices that are worn by... more There is a great effort during the last decades towards building robotic devices that are worn by humans. These devices, called exoskeletons, are used mainly for support and rehabilitation, as well as for augmentation of human capabilities. Providing a control interface for exoskeletons, that would guarantee comfort and safety, as well as efficiency and robustness, is still an issue. This paper presents a methodology for estimating human arm motion and force exerted, using electromyographic (EMG) signals from muscles of the upper limb. The proposed method is able to estimate motion of the human arm as well as force exerted from the upper limb to the environment, when the motion is constrained. Moreover, the method can distinguish the cases in which the motion is constrained or not (i.e. exertion of force versus free motion) which is of great importance for the control of exoskeletons. Furthermore, the method provides a continuous profile of estimated motion and force, in contrast to other methods used in the literature that can only detect initiation of movement or intention of force. The system is tested in an orthosis-like scenario, during planar movements, through various experiments. The experimental results prove the system efficiency, making the proposed methodology a strong candidate for an EMG-based control scheme applied in robotic exoskeletons.
Proceedings 2006 Ieee International Conference on Robotics and Automation 2006 Icra 2006, May 15, 2006
A distributed feedback control architecture that guarantees collision avoidance and destination c... more A distributed feedback control architecture that guarantees collision avoidance and destination convergence for multiple sphere world holonomic agents is presented. The well established tool of Decentralized Navigation Functions is redefined to cope with the communication restrictions of the system. Each agent plans its actions without knowing the destinations of the others and the positions of those agents lying outside its sensing neighborhood. The stability properties of the closed loop system are checked via Lyapunov stability techniques for hybrid systems. The collision avoidance and goal convergence properties are verified through simulations. The key advantage of the proposed algorithm with respect to the previous ones is the significant decrease of computational load and its applicability to large scale groups.
Http Dx Doi Org 10 1163 156855302317413745, Apr 2, 2012
... independently of the motion of the other joints, where j = 1,...,m. Detailed modeling and acc... more ... independently of the motion of the other joints, where j = 1,...,m. Detailed modeling and accurate ... 1). This system becomes uniformly asymptotically stable to zero ae1, under the control input ... have used for the implementation of the simulations, is the model of Mitsubishi PA10-7C ...
Proceedings of the 48h Ieee Conference on Decision and Control Held Jointly With 2009 28th Chinese Control Conference, 2009
This paper presents a methodology for the decentralised control of multiple 3-dimensional nonholo... more This paper presents a methodology for the decentralised control of multiple 3-dimensional nonholonomic agents. The proposed control scheme is based on Navigation Functions and offers improvements compared to previous work of the authors in this field. The problem formulation is chosen to resemble Air-Traffic Management, where the safety guarantees provided by Navigation Functions based control strategies are very important. The linear velocity of each agent is maintained constant and equal to a desired value in most cases, while the azimuth and elevation control laws are engineered to reduce the required control effort. These qualitative improvements do not affect the collision avoidance characteristics of the control strategy. The performance and efficiency of our approach is supported by computer simulations presented in the paper.
2007 European Control Conference, 2007
We present a methodology to steer the end effector of a robotic manipulator, which is constrained... more We present a methodology to steer the end effector of a robotic manipulator, which is constrained in terms of joint rates, on the surface within the workspace. We develop controllers for stabilizing the end effector to a point, and for tracking a trajectory on this surface, while respecting the input constraints. We show that the resulting closed loop system is uniformly asymptotically stable and we verify our analytical development with computer simulations.
2008 Ieee Rsj International Conference on Intelligent Robots and Systems, 2008
Page 1. Visual Servo Control of an Underwater Vehicle Using a Laser Vision System George C. Karra... more Page 1. Visual Servo Control of an Underwater Vehicle Using a Laser Vision System George C. Karras and Kostas J. Kyriakopoulos Abstract This paper describes a position-based visual servo control scheme designed for an underwater vehicle. ...
2007 European Control Conference, Jul 1, 2007
... feedback scheme. A closed loop approach for single robot navigation was proposed by Koditsche... more ... feedback scheme. A closed loop approach for single robot navigation was proposed by Koditschek and Rimon [12], [27] in their seminal work. This navigation functions' framework handled single, point-sized, robot navigation. In ...
Proceedings Ieee International Conference on Robotics and Automation, May 19, 2008
We propose an inverse agreement control strategy for multiple nonholonomic agents that forces the... more We propose an inverse agreement control strategy for multiple nonholonomic agents that forces the team members to disperse in the workspace in a distributed manner. Both the cases of an unbounded and a circular bounded workspace are considered. In the first case, we show that the closed loop system reaches a configuration in which the minimum distance between any pair of agents is larger than a specific lower bound. It is proved that this lower bound coincides with the agents' sensing radius. In the case of a bounded workspace, the control law is modified to force the agents to remain within the workspace boundary throughout the closed loop system evolution. Moreover the proposed control guarantees collision avoidance between the team members. The results are supported through relevant computer simulations.
Proceedings of the Ieee Conference on Decision and Control, 2008
We present a novel control scheme for multiple non-holonomic vehicles under uncertainty, which ca... more We present a novel control scheme for multiple non-holonomic vehicles under uncertainty, which can guarantee collision avoidance while complying with constraints imposed on the vehicles. Dipolar Navigation Functions are used for decentralized conflict-free control, while Model Predictive Control is used in a centralized manner in order to ensure that the resulting trajectories remain feasible with respect to the constraints present and to optimize the performance objectives. The model used is chosen to resemble air traffic control problems, with some uncertainty introduced in the system. The efficiency of the control strategy is demonstrated by realistic simulations.
2012 American Control Conference (ACC), 2012
ABSTRACT
2013 Oceans San Diego, 2013