The Experts below are selected from a list of 324 Experts worldwide ranked by ideXlab platform

Allison M. Okamura - One of the best experts on this subject based on the ideXlab platform.

  • Stable Forbidden-Region virtual fixtures for bilateral telemanipulation; ; Transactions of the ASME. Ser. G, Journal of dynamic systems, measurement, and control;
    2006
    Co-Authors: Jake J. Abbott, Allison M. Okamura
    Abstract:

    There has been recent interest in novel human-machine collaborative control laws, called "virtual fixtures," which provide operator assistance for telemanipulation tasks. A Forbidden-Region virtual fixture is a constraint, implemented in software, that seeks to prevent the slave manipulator of a master/slave telemanipulation system front entering into a Forbidden Region of the workspace. In this paper we consider the problem of unstable vibrations of the slave and/or master against Forbidden-Region virtual fixtures for a general class of telemanipulator control architectures, including those with haptic feedback. To the best of the authors' knowledge, there has been no rigorous study of the stability, of Forbidden-Region virtual fixtures in previous work. The system is evaluated around the master and slave equilibrium position resulting from a constant desired humun input force, using a discrete state-space model. We present a method to analytically determine if instability is possible in the system. We thoroughly evaluate this method, experimentally, applying malicious user strategies that attempt to drive the system unstable. Our approach agrees with experimental results and can be used to design and analyze the stability and transient properties of a telemanipulator interacting with virtual fixtures. We show that the user can affect both slave- and master-side virtual fixture stability by modifying his or her impedance characteristics. However, the upper bound on stable slave-side virtual fixture stiffness does not depend on the particular user.

  • Stable Forbidden-Region Virtual Fixtures for Bilateral Telemanipulation
    Journal of Dynamic Systems Measurement and Control, 2005
    Co-Authors: Jake J. Abbott, Allison M. Okamura
    Abstract:

    There has been recent interest in novel human-machine collaborative control laws, called "virtual fixtures," which provide operator assistance for telemanipulation tasks. A Forbidden-Region virtual fixture is a constraint, implemented in software, that seeks to prevent the slave manipulator of a master/slave telemanipulation system from entering into a Forbidden Region of the workspace. In this paper, we consider the problem of unstable vibrations of the slave and/or master against Forbidden-Region virtual fixtures for a general class of telemanipulator control architectures, including those with haptic feedback. To the best of the authors' knowledge, there has been no rigorous study of the stability of Forbidden-Region virtual fixtures in previous work. The system is evaluated around the master and slave equilibrium position resulting from a constant desired human input force, using a discrete state-space model. We present a method to analytically determine if instability is possible in the system. We thoroughly evaluate this method, experimentally, applying malicious user strategies that attempt to drive the system unstable. Our approach agrees with experimental results and can be used to design and analyze the stability and transient properties of a telemanipulator interacting with virtual fixtures. We show that the user can affect both slave- and master-side virtual fixture stability by modifying his or her impedance characteristics. However, the upper bound on stable slave-side virtual fixture stiffness does not depend on the particular user.

  • HAPTICS - Effect of Hand Dynamics on Virtual Fixtures for Compliant Human-Machine Interfaces
    IEEE Virtual Reality Conference (VR'06), 1
    Co-Authors: Panadda Marayong, Gregory D. Hager, Allison M. Okamura
    Abstract:

    In human-machine interfaces with joint/link compliance, human hand dynamics can have a detrimental effect on system performance. This paper investigates the effect of human dynamics on the effectiveness of a virtual fixture implemented on an admittance-controlled robot with joint compliance. Two open-loop control methods are proposed for creating a virtual fixture that prevents the user from entering a Forbidden Region: one that compensates for hand dynamics, and one that predicts overshoot based on the user’s current velocity. The methods determine a“safe” location of the virtual fixture that prevents the user from entering the true Forbidden Region. A first experiment was conducted to determine hand dynamic parameters (mass, damping, and stiffness) and evaluate their relationship to the force applied by the user on the interface. A second experiment demonstrated that both methods for creating safe virtual fixtures prevent the user from entering the Forbidden Region, even when the interface has significant joint compliance.

  • IROS - Analysis of virtual fixture contact stability for telemanipulation
    Proceedings 2003 IEEE RSJ International Conference on Intelligent Robots and Systems (IROS 2003) (Cat. No.03CH37453), 1
    Co-Authors: Jake J. Abbott, Allison M. Okamura
    Abstract:

    A Forbidden-Region virtual fixture (FRVF) is a constraint, implemented in software, that keeps the slave manipulator of a master/slave telemanipulation system from entering into a Forbidden Region of the workspace. In this paper, we consider the problem of unstable vibrations of the slave against the FRVF for a general class of telemanipulator control architectures. The master and slave equilibrium positions resulting from a constant human input force are found, and the system is evaluated around this equilibrium. We consider two methods of analyzing the stability of the system around this equilibrium point. The first method uses tools developed for analysis of two-port networks. The second method converts the system to its discrete state-space form, and then uses the position of the eigenvalues to analyze system stability. We find that the discrete state-space method agrees with simulations, and can be easily used to design and analyze the stability and transient behavior of the telemanipulator.

  • ICRA - Virtual fixture architectures for telemanipulation
    2003 IEEE International Conference on Robotics and Automation (Cat. No.03CH37422), 1
    Co-Authors: Jake J. Abbott, Allison M. Okamura
    Abstract:

    A Forbidden-Region virtual fixture (FRVF) is a computer-generated constraint that displays position or force limitations to a robot manipulator or operator, in order to prevent motion into Forbidden Regions of the workspace. We compare nine FRVFs on each of four common telemanipulator control architectures: position forward, position exchange, position forward/force feedback, and position exchange/force feedback. A one-degree-of-freedom telemanipulation system was used in an experiment designed to simulate users working near a known Forbidden Region. The metrics of tracking, safety, and submittance were used to analyze the performance of the system with six different users. The results indicate that different FRVF architectures perform best for each of the three metrics. No single FRVF scheme is the best over all metrics, so selection of an FRVF architecture should be an application-dependent weighting of the three metrics. Across all control architectures, the results indicate that a very strong FRVF at the slave device in combination with no FRVF at the master device leads to poor telepresence.

Howard J. Chizeck - One of the best experts on this subject based on the ideXlab platform.

  • Forbidden Region virtual fixtures from streaming point clouds
    Advanced Robotics, 2014
    Co-Authors: Sina Nia Kosari, Fredrik Ryden, Thomas S. Lendvay, Blake Hannaford, Howard J. Chizeck
    Abstract:

    Forbidden Region virtual fixtures protect objects from unwanted contact with a robot. In this paper, we propose a method for creating Forbidden Region haptic virtual fixtures for teleoperation from streaming point clouds obtained by an RGB-D camera. Upon violating the protected area, the operator receives force feedback that opposes motion inside the Forbidden Region. Three architectures for creating virtual fixtures are presented and their advantages and disadvantages are described. The proposed methods have the ability to implement constraints and can handle dynamic environments in real-time. The effectiveness of the methods is demonstrated in experiments with a surgical robot.

  • Forbidden Region virtual fixtures from streaming point clouds remotely touching and protecting a beating heart
    Intelligent Robots and Systems, 2012
    Co-Authors: Fredrik Ryden, Howard J. Chizeck
    Abstract:

    Several established methods for remote touching using non-contact sensors exist. Applications for these methods are primarily within the field of robotic teleoperation. In surgical robotics it would be useful to not only touch, but also be able to maintain a distance from a certain organ. The latter can be done using non-contact sensors such as cameras. The novelty in this paper is the idea of combining Forbidden-Region virtual fixtures with haptic rendering from streaming point clouds. This is then used to protect as well as remotely touch a beating heart without any a priori knowledge of the heart geometry (such as from CT/MR scans).

  • IROS - Forbidden-Region virtual fixtures from streaming point clouds: Remotely touching and protecting a beating heart
    2012 IEEE RSJ International Conference on Intelligent Robots and Systems, 2012
    Co-Authors: Fredrik Ryden, Howard J. Chizeck
    Abstract:

    Several established methods for remote touching using non-contact sensors exist. Applications for these methods are primarily within the field of robotic teleoperation. In surgical robotics it would be useful to not only touch, but also be able to maintain a distance from a certain organ. The latter can be done using non-contact sensors such as cameras. The novelty in this paper is the idea of combining Forbidden-Region virtual fixtures with haptic rendering from streaming point clouds. This is then used to protect as well as remotely touch a beating heart without any a priori knowledge of the heart geometry (such as from CT/MR scans).

Jake J. Abbott - One of the best experts on this subject based on the ideXlab platform.

  • Stable Forbidden-Region virtual fixtures for bilateral telemanipulation; ; Transactions of the ASME. Ser. G, Journal of dynamic systems, measurement, and control;
    2006
    Co-Authors: Jake J. Abbott, Allison M. Okamura
    Abstract:

    There has been recent interest in novel human-machine collaborative control laws, called "virtual fixtures," which provide operator assistance for telemanipulation tasks. A Forbidden-Region virtual fixture is a constraint, implemented in software, that seeks to prevent the slave manipulator of a master/slave telemanipulation system front entering into a Forbidden Region of the workspace. In this paper we consider the problem of unstable vibrations of the slave and/or master against Forbidden-Region virtual fixtures for a general class of telemanipulator control architectures, including those with haptic feedback. To the best of the authors' knowledge, there has been no rigorous study of the stability, of Forbidden-Region virtual fixtures in previous work. The system is evaluated around the master and slave equilibrium position resulting from a constant desired humun input force, using a discrete state-space model. We present a method to analytically determine if instability is possible in the system. We thoroughly evaluate this method, experimentally, applying malicious user strategies that attempt to drive the system unstable. Our approach agrees with experimental results and can be used to design and analyze the stability and transient properties of a telemanipulator interacting with virtual fixtures. We show that the user can affect both slave- and master-side virtual fixture stability by modifying his or her impedance characteristics. However, the upper bound on stable slave-side virtual fixture stiffness does not depend on the particular user.

  • Stable Forbidden-Region Virtual Fixtures for Bilateral Telemanipulation
    Journal of Dynamic Systems Measurement and Control, 2005
    Co-Authors: Jake J. Abbott, Allison M. Okamura
    Abstract:

    There has been recent interest in novel human-machine collaborative control laws, called "virtual fixtures," which provide operator assistance for telemanipulation tasks. A Forbidden-Region virtual fixture is a constraint, implemented in software, that seeks to prevent the slave manipulator of a master/slave telemanipulation system from entering into a Forbidden Region of the workspace. In this paper, we consider the problem of unstable vibrations of the slave and/or master against Forbidden-Region virtual fixtures for a general class of telemanipulator control architectures, including those with haptic feedback. To the best of the authors' knowledge, there has been no rigorous study of the stability of Forbidden-Region virtual fixtures in previous work. The system is evaluated around the master and slave equilibrium position resulting from a constant desired human input force, using a discrete state-space model. We present a method to analytically determine if instability is possible in the system. We thoroughly evaluate this method, experimentally, applying malicious user strategies that attempt to drive the system unstable. Our approach agrees with experimental results and can be used to design and analyze the stability and transient properties of a telemanipulator interacting with virtual fixtures. We show that the user can affect both slave- and master-side virtual fixture stability by modifying his or her impedance characteristics. However, the upper bound on stable slave-side virtual fixture stiffness does not depend on the particular user.

  • IROS - Analysis of virtual fixture contact stability for telemanipulation
    Proceedings 2003 IEEE RSJ International Conference on Intelligent Robots and Systems (IROS 2003) (Cat. No.03CH37453), 1
    Co-Authors: Jake J. Abbott, Allison M. Okamura
    Abstract:

    A Forbidden-Region virtual fixture (FRVF) is a constraint, implemented in software, that keeps the slave manipulator of a master/slave telemanipulation system from entering into a Forbidden Region of the workspace. In this paper, we consider the problem of unstable vibrations of the slave against the FRVF for a general class of telemanipulator control architectures. The master and slave equilibrium positions resulting from a constant human input force are found, and the system is evaluated around this equilibrium. We consider two methods of analyzing the stability of the system around this equilibrium point. The first method uses tools developed for analysis of two-port networks. The second method converts the system to its discrete state-space form, and then uses the position of the eigenvalues to analyze system stability. We find that the discrete state-space method agrees with simulations, and can be easily used to design and analyze the stability and transient behavior of the telemanipulator.

  • ICRA - Virtual fixture architectures for telemanipulation
    2003 IEEE International Conference on Robotics and Automation (Cat. No.03CH37422), 1
    Co-Authors: Jake J. Abbott, Allison M. Okamura
    Abstract:

    A Forbidden-Region virtual fixture (FRVF) is a computer-generated constraint that displays position or force limitations to a robot manipulator or operator, in order to prevent motion into Forbidden Regions of the workspace. We compare nine FRVFs on each of four common telemanipulator control architectures: position forward, position exchange, position forward/force feedback, and position exchange/force feedback. A one-degree-of-freedom telemanipulation system was used in an experiment designed to simulate users working near a known Forbidden Region. The metrics of tracking, safety, and submittance were used to analyze the performance of the system with six different users. The results indicate that different FRVF architectures perform best for each of the three metrics. No single FRVF scheme is the best over all metrics, so selection of an FRVF architecture should be an application-dependent weighting of the three metrics. Across all control architectures, the results indicate that a very strong FRVF at the slave device in combination with no FRVF at the master device leads to poor telepresence.

Fredrik Ryden - One of the best experts on this subject based on the ideXlab platform.

  • Forbidden Region virtual fixtures from streaming point clouds
    Advanced Robotics, 2014
    Co-Authors: Sina Nia Kosari, Fredrik Ryden, Thomas S. Lendvay, Blake Hannaford, Howard J. Chizeck
    Abstract:

    Forbidden Region virtual fixtures protect objects from unwanted contact with a robot. In this paper, we propose a method for creating Forbidden Region haptic virtual fixtures for teleoperation from streaming point clouds obtained by an RGB-D camera. Upon violating the protected area, the operator receives force feedback that opposes motion inside the Forbidden Region. Three architectures for creating virtual fixtures are presented and their advantages and disadvantages are described. The proposed methods have the ability to implement constraints and can handle dynamic environments in real-time. The effectiveness of the methods is demonstrated in experiments with a surgical robot.

  • Forbidden Region virtual fixtures from streaming point clouds remotely touching and protecting a beating heart
    Intelligent Robots and Systems, 2012
    Co-Authors: Fredrik Ryden, Howard J. Chizeck
    Abstract:

    Several established methods for remote touching using non-contact sensors exist. Applications for these methods are primarily within the field of robotic teleoperation. In surgical robotics it would be useful to not only touch, but also be able to maintain a distance from a certain organ. The latter can be done using non-contact sensors such as cameras. The novelty in this paper is the idea of combining Forbidden-Region virtual fixtures with haptic rendering from streaming point clouds. This is then used to protect as well as remotely touch a beating heart without any a priori knowledge of the heart geometry (such as from CT/MR scans).

  • IROS - Forbidden-Region virtual fixtures from streaming point clouds: Remotely touching and protecting a beating heart
    2012 IEEE RSJ International Conference on Intelligent Robots and Systems, 2012
    Co-Authors: Fredrik Ryden, Howard J. Chizeck
    Abstract:

    Several established methods for remote touching using non-contact sensors exist. Applications for these methods are primarily within the field of robotic teleoperation. In surgical robotics it would be useful to not only touch, but also be able to maintain a distance from a certain organ. The latter can be done using non-contact sensors such as cameras. The novelty in this paper is the idea of combining Forbidden-Region virtual fixtures with haptic rendering from streaming point clouds. This is then used to protect as well as remotely touch a beating heart without any a priori knowledge of the heart geometry (such as from CT/MR scans).

Michael F. Herman - One of the best experts on this subject based on the ideXlab platform.

  • Analysis of a surface hopping expansion that includes hops in classically Forbidden Regions
    Chemical Physics, 2014
    Co-Authors: Michael F. Herman
    Abstract:

    A surface hopping expansion of the nonadiabatic wave function is generalized to account for hops from the Forbidden Region on one adiabatic energy surface to a different adiabatic surface in multidimensional problems. This analysis is motivated by previous surface hopping calculations on one dimensional models that provide very accurate transition probabilities, even at low energies, if classically Forbidden hops are included in the calculations. It is shown that hops from the classically Forbidden Region in the previous form of the surface hopping expansion cannot, in general, lead to classically allowed final state trajectories in multidimensional problems. The surface hopping wave function is generalized to allow for two or more hops at each point along the trajectory. These hops correspond to different directions for the energy conserving momentum change, which gives different post-hop trajectories. This generalization allows for the final state trajectory to be classically allowed if the post-hop adiabatic energy surface has sufficiently low energy.

  • The calculation of multidimensional semiclassical wave functions in the Forbidden Region using real valued coordinates
    The Journal of chemical physics, 2010
    Co-Authors: Michael F. Herman
    Abstract:

    A method that uses only real valued coordinates is presented for integrating the many dimensional semiclassical wave function into the Forbidden Region. The procedure first determines a surface of caustic points by running the set of trajectories that define the wave function in the allowed Region. In the Forbidden Region, the momentum and the action integral are both complex functions of position, and their imaginary parts vanish on the caustic surface. The direction of the imaginary part of the momentum pI can be chosen to the perpendicular to the caustic surface at all points on that surface. Equations are derived for integrating the values of the real and imaginary parts of the momentum along the curves that follow the direction of pI. The equations for the change in the action integral and the prefactor for the semiclassical wave function along these curves are also obtained, allowing for the determination of the semiclassical wave function in the Forbidden Region. Calculations are performed for a tw...