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Venkat N Krovi

SUNY: University at Buffalo, Department of Mechanical and Aerospace Engineering, Faculty Member

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Cagatay Basdogan

Gaurav Sukhatme

University of Southern California

Rensselaer Polytechnic Institute

Mandayam Srinivasan

Visvesvaraya Technological University

Gregory S Fischer

Worcester Polytechnic Institute

Sebastian Ullrich

RWTH Aachen University

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Papers by Venkat N Krovi

Data Driven Development of Haptic Models for Needle Biopsy Phantoms

Volume 3: Renewable Energy Systems; Robotics; Robust Control; Single Track Vehicle Dynamics and Control; Stochastic Models, Control and Algorithms in Robotics; Structure Dynamics and Smart Structures;, 2012

Needle biopsy is an important and common procedure for lesion detection or tissue extraction with... more Needle biopsy is an important and common procedure for lesion detection or tissue extraction within the human body. Physicians conducting such procedures rely primarily on the sense of "touch" (kinesthetic feedback from needle) to estimate the current needle position and organs within its vicinity. This skill takes time to acquire and mature, often by biopsies on live patients. Medical residents and fellow trainees thus have limited opportunities both in terms of real life scenarios as well as testing platforms to develop and validate their skills. This paper focuses on building a biopsy simulator for training on virtual phantoms (using both visual and force feedback) and cross validation using a real physical phantom. In order to develop a virtual-haptic model of biopsy phantom, material testing experiments were conducted to obtain motion-force profiles from an instrumented 6-DOF robot platform serving as a needle driver. The measured force-displacement data was then used to develop three types of haptic models for the phantom to calculate the force feedback for the haptic device. Neural network based models provided a more accurate force-reflection model compared to the other two methods from the literature and will form the basis of the virtual phantoms within our framework.

Radial Basis Function Network (RBFN) Approximation of Finite Element Models for Real-Time Simulation

ASME 2011 Dynamic Systems and Control Conference and Bath/ASME Symposium on Fluid Power and Motion Control, Volume 2, 2011

Nonlinearities inherent in soft-tissue interactions create roadblocks to realization of high-fide... more Nonlinearities inherent in soft-tissue interactions create roadblocks to realization of high-fidelity real-time haptics-based medical simulations. While finite element (FE) formulations offer greater accuracy over conventional spring-mass-network models, computational-complexity limits achievable simulation-update rates. Direct interaction with sensorized physical surrogates, in offline or online modes, allows a temporary sidestepping of computational issues but hinders parametric analysis and true exploitation of a simulation-based testing paradigm. Hence, in this paper, we develop Radial-Basis Neural-Network approximations, to FE-model data within a Modified Resource Allocating Network (MRAN) framework. Real-time simulation of the reduced order neural-network approximations at high temporal resolution provided the haptic-feedback. Validation studies are being conducted to evaluate the kinesthetic realism of these models with medical experts.

Robotic Minimally Invasive Surgical skill assessment based on automated video-analysis motion studies

2012 4th IEEE RAS & EMBS International Conference on Biomedical Robotics and Biomechatronics (BioRob), 2012

Abstract²Assessment of surgical skill, arising from the synthesis of the cognitive and sensorimot... more Abstract²Assessment of surgical skill, arising from the synthesis of the cognitive and sensorimotor capabilities of the surgeon, has predominantly been a subjective task. Development of quantitative metrics-of-performance with clinical relevance and other desirable characteristics (repeatability and stability) has always lagged behind. New opportunities for objective and automated assessment frameworks have arisen by virtue of technological advances in computation, video-processing, and data-acquisition, especially in the robotic Minimally Invasive Surgical (rMIS) realm.

An Engineering Approach to Utilizing Bio-Inspiration in Robotics Applications

Biologically Inspired Design, 2013

Parallel Architecture Manipulators for Use in Masticatory Studies

International Journal of Intelligent Mechatronics and Robotics, 2011

Product of tracking experts for visual tracking of surgical tools

2013 IEEE International Conference on Automation Science and Engineering (CASE), 2013

This paper proposes a novel tool detection and tracking approach using uncalibrated monocular sur... more This paper proposes a novel tool detection and tracking approach using uncalibrated monocular surgical videos for computer-aided surgical interventions. We hypothesize surgical tool end-effector to be the most distinguishable part of a tool and employ state-of-the-art object detection methods to learn the shape and localize the tool in images. For tracking, we propose a Product of Tracking Experts (PoTE) based generalized object tracking framework by probabilistically-merging tracking outputs (probabilistic/non-probabilistic) from timevarying numbers of trackers. In the current implementation of PoTE, we use three tracking experts -point-feature-based, region-based and object detection-based. A novel point featurebased tracker is also proposed in the form of a voting based bounding box geometry estimation technique building upon point-feature correspondences. Our tracker is causal which makes it suitable for real-time applications. This framework has been tested on real surgical videos and is shown to significantly improve upon the baseline results.

Surgical tool attributes from monocular video

2014 IEEE International Conference on Robotics and Automation (ICRA), 2014

HD Video from the (monocular or binocular) endoscopic camera provides a rich real-time sensing ch... more HD Video from the (monocular or binocular) endoscopic camera provides a rich real-time sensing channel from surgical site to the surgeon console in various Minimally Invasive Surgery (MIS) procedures. However, a real-time framework for video understanding would be critical for tapping into the rich information-content provided by the non-invasive and well-established digital endoscopic video-streaming modality. While contemporary research focuses on enhancing aspects such as tool-tracking within the challenging visual scenes, we consider the associated problem of using that rich (but often compromised) streaming visual data to discover the underlying semantic attributes of the tools.

Virtual musculoskeletal scenario-testing case-studies

2008 Virtual Rehabilitation, 2008

Doctors, dentists, nurses, athletic trainers, occupational therapists and allied health-care prof... more Doctors, dentists, nurses, athletic trainers, occupational therapists and allied health-care professionals are expected to learn the linkage between anatomy, physiology and ultimately functional-performance of muscles i.e. how muscles affect movement or which sets of muscles carry various loads. However the extent of understanding of functionalperformance that can be imparted in a didactic-lecture or cadaver-lab setting of a "Gross Anatomy" class is limited. Hence we seek to create the architecture and algorithms for scaffolded interaction with human musculoskeletal simulation models (virtual prototypes) that can make varied "what-if" type analyses and hypothesis-testing possible. This is very pertinent in the context of the target audience of healthcare professionals who may lack prior exposure to such virtual computational scenario testing tools. Providing such access is vital to training of the next generation of health care professionals to leverage ubiquitous computing and the quantitative-paradigm.

Role of Automated Symbolic Generation of Equations of Motion in Mechanism and Robotics Education

Volume 2: 34th Annual Mechanisms and Robotics Conference, Parts A and B, 2010

In recent years there has been a significant increase in the variety and complexity of Articulate... more In recent years there has been a significant increase in the variety and complexity of Articulated-Multi-Body-Systems (AMBS) used for various applications. There is also increased interest in the model-based design-refinement and controller-development, which is critically dependent upon availability of underlying plantmodels.

Role of Automated Symbolic Generation of Plant Models in Control Education

ASME 2010 Dynamic Systems and Control Conference, Volume 2, 2010

CAD-enhanced workspace optimization for parallel manipulators: A case study

2010 IEEE International Conference on Automation Science and Engineering, 2010

The challenges of workspace determination of parallel manipulators (PMs) arise principally from t... more The challenges of workspace determination of parallel manipulators (PMs) arise principally from the lack of analytical solutions of the forward kinematics. The inverseposition kinematics based approach for determining workspace tends to be inefficient, time consuming and unsophisticated. In this paper, we present a geometry-based method for accurate and computationally effective calculation of the workspace of a constrained parallel manipulator. We illustrate how boolean geometric operations can simplify the process of finding the workspace and optimizing the designs. Comparative performance studies, in terms of accuracy and computational performance, are performed to benchmark the approach against more conventional methods. Finally, we examine ways to further automate the process using a CAD package.

Random Matrix Approach: Toward Probabilistic Formulation of the Manipulator Jacobian

Journal of Dynamic Systems, Measurement, and Control, 2014

In this paper, we formulate the manipulator Jacobian matrix in a probabilistic framework based on... more In this paper, we formulate the manipulator Jacobian matrix in a probabilistic framework based on the random matrix theory (RMT). Due to the limited available information on the system fluctuations, the parametric approaches often prove to be inadequate to appropriately characterize the uncertainty. To overcome this difficulty, we develop two RMTbased probabilistic models for the Jacobian matrix to provide systematic frameworks that facilitate the uncertainty quantification in a variety of complex robotic systems. One of the models is built upon direct implementation of the maximum entropy principle that results in a Wishart random perturbation matrix. In the other probabilistic model, the Jacobian matrix is assumed to have a matrix-variate Gaussian distribution with known mean. The covariance matrix of the Gaussian distribution is obtained at every time point by maximizing a Shannon entropy measure (subject to Jacobian norm and covariance positive semidefiniteness constraints). In contrast to random variable/vector based schemes, the benefits of the proposed approach now include: (i) incorporating the kinematic configuration and complexity in the probabilistic formulation; (ii) achieving the uncertainty model using limited available information; (iii) taking into account the working configuration of the robotic systems in characterization of the uncertainty; and (iv) realizing a faster simulation process. A case study of a 2R serial manipulator is presented to highlight the critical aspects of the process.

Formation optimization for a fleet of wheeled mobile robots — A geometric approach

Robotics and Autonomous Systems, 2009

Tight formation-based operations are critical in several emerging applications for robot collecti... more Tight formation-based operations are critical in several emerging applications for robot collectives -ranging from cooperative payload transport to synchronized distributed data-collection. In this paper, we investigate the optimal relative layout for members of a team of Differentially-Driven Wheeled Mobile Robots (DD-WMRs) moving in formation for ultimate deployment in cooperative payload transport tasks.

Modular and Recursive Kinematics and Dynamics for Parallel Manipulators

Multibody System Dynamics, 2005

Constrained multibody systems typically feature multiple closed kinematic loops that constrain th... more Constrained multibody systems typically feature multiple closed kinematic loops that constrain the relative motions and forces within the system. Typically, such systems possess far more articulated degrees-of-freedom (within the chains) than overall end-effector degrees-of-freedom. Thus, actuation of a subset of the articulations creates mixture of active and passive joints within the chain. The presence of such passive joints interferes with the effective modular formulation of the dynamic equations-of-motion in terms of a minimal set of actuator coordinates as well the subsequent recursive solution for both forward and inverse dynamics applications.

Screw-theoretic analysis models for felid jaw mechanisms

Mechanism and Machine Theory, 2008

In this paper, we examine the development of quasi-static computational models for musculoskeleta... more In this paper, we examine the development of quasi-static computational models for musculoskeletal analysis, leveraging screw-theoretic techniques traditionally employed for the analysis of articulated multibody systems (MBS). The case study of analysis of bite-and muscle-forces in the articulated jaws of members of the felid (cat) family is used to highlight the critical aspects. In particular, musculoskeletal systems with multiple muscles superimposed on an underlying articulated skeleton share many features with the subclass of cable actuated parallel MBS (including redundancy in actuation and unidirectional nature of actuation forces). The screw-theoretic formulation facilitates the development of a computational model for resolving such redundancy while retaining explicit geometric meaning in terms of lines-of-action, motions and forces. The low-computational-complexity of the ensuing quasi-static models makes them well-suited both for: (a) iterative/parametric studies of the roles of geometry (muscle locations) or physiology (muscle-parameters) on skeletal loaddistributions, as well as (b) implementing online inverse-dynamics-based muscle-force planners for biomimetic physical prototypes. A MATLAB Graphical User Interface was also developed to aid lay users (non-computational scientists) in performing iterative parametric force optimization and muscle location studies.

Modular and distributed forward dynamic simulation of constrained mechanical systems – A comparative study

Mechanism and Machine Theory, 2007

In this paper, we examine the modular development of two alternate methods for distributed comput... more In this paper, we examine the modular development of two alternate methods for distributed computation of the forward dynamics simulations of constrained mechanical systems. We exploit the natural spatial parallelism of closedchain linkages, initially, for the modular development of overall dynamics, and subsequently, for the distributed numerical simulation of the dynamics. Traditionally, the numerical simulation problem of constrained mechanical systems has been treated as two separate stages: the problem of algorithm development and the subsequent numerical problem of advancing the discretized differential equations in time. However the potential numerical instabilities arising from the formulation stiffness of the algorithm development stage has the potential to hinder the subsequent numerical integration stage. These aspects are also explored during the evaluation of the two alternative approaches for the distributed forward dynamics simulation of a four-bar linkage. A series of tests were performed on a real-time synchronized distributed computational system (RT-LAB) to evaluate the performance of both methods of simulation and preliminary results to quantify the overall computational efficiency and accuracy are presented.

Evaluation of robotic minimally invasive surgical skills using motion studies

Journal of Robotic Surgery, 2013

Robotic Minimally Invasive Surgery, and the engendered computer-integration, offers unique opport... more Robotic Minimally Invasive Surgery, and the engendered computer-integration, offers unique opportunities for quantitative computer-based surgical-performance evaluation. In this work, we examine extension of traditional manipulative skill assessment, having deep roots in performance evaluation in manufacturing industries, for applicability to robotic surgical skill evaluation. This method relies on: defining task-level segmentation of modular sub-tasks/micro-motions called &amp;amp;amp;amp;#39;Therbligs&amp;amp;amp;amp;#39; that can be combined to perform a given task; and analyzing intra- and inter-user performance variance by studying surgeons&amp;amp;amp;amp;#39; performance over each &amp;amp;amp;amp;#39;Therbligs&amp;amp;amp;amp;#39;. Any of the performance metrics of macro-motions-from motion-economy, tool motion measurements to handed-symmetry-can now be extended over the micro-motion temporal segments. Evaluation studies were based on video recordings of surgical tasks in two settings: first, we examined performance of two representative manipulation exercises (peg board and pick-and-place) on a da Vinci surgical SKILLS simulator. This affords a relatively-controlled and standardized test-scenarios for surgeons with varied experience-levels. Second, task-sequences from real surgical videos were analyzed with a list of predefined &amp;amp;amp;amp;#39;Therbligs&amp;amp;amp;amp;#39; in order to investigate its overall usefulness.

Kinematic and Kinetostatic Synthesis of Planar Coupled Serial Chain Mechanisms

Journal of Mechanical Design, 2002

a number of manipulation tasks. Such SDCSC mechanisms take advantage of the hardware constraints ... more a number of manipulation tasks. Such SDCSC mechanisms take advantage of the hardware constraints between the articulations of a serial-chain linkage, created using gear-trains or belt/pulley drives, to guide the end-effector motions and forces. In this paper, we examine the dimensional synthesis of such SDCSC mechanisms to perform desired planar manipulation tasks, taking into account task specifications on both end-effector motions and forces. Our solution approach combines precision point synthesis with optimization to realize optimal mechanisms, which satisfy the design specifications exactly at the selected precision points and approximate them in the least-squares sense elsewhere along a specified trajectory. The designed mechanisms can guide a rigid body through several positions while supporting arbitrarily specified external loads. Furthermore, torsional springs are added at the joints to reduce the overall actuation requirements and to enhance the task performance. Examples from the kinematic and the kinetostatic synthesis of planar SDCSC mechanisms are presented to highlight the benefits. Fig. 4 "a… Schematic of operation of the head-controlled feeding device. "b… Physical and mathematical models of a 2-link SDCSC mechanism.

Kinematic Synthesis of Spatial R-R Dyads for Path Following With Applications to Coupled Serial Chain Mechanisms

Journal of Mechanical Design, 2001

The dimensional synthesis of a spatial two revolute jointed dyad for path following tasks with ap... more The dimensional synthesis of a spatial two revolute jointed dyad for path following tasks with applications to coupled serial chain mechanisms is presented. The precision point synthesis equations obtained using the rotation matrix approach form a rank-deficient linear system in the link-vector components. The nullspace of this rank-deficient linear system is derived analytically and interpreted geometrically. The nullspace vectors lead to the specification of additional constraints via the so-called auxiliary equations and to the solution of the linear system of equations. The geometry also allows the derivation of a closed form solution for the three design position problem. Finally, optimal path following by coupled R-R dyads is achieved by optimization over the free choice variables.

Fourier Methods for Kinematic Synthesis of Coupled Serial Chain Mechanisms

Journal of Mechanical Design, 2005

Single degree-of-freedom coupled serial chain (SDCSC) mechanisms are a class of mechanisms that c... more Single degree-of-freedom coupled serial chain (SDCSC) mechanisms are a class of mechanisms that can be realized by coupling successive joint rotations of a serial chain linkage, by way of gears or cable-pulley drives. Such mechanisms combine the benefits of single degree-of-freedom design and control with the anthropomorphic workspace of serial chains. Our interest is in creating articulated manipulation-assistive aids based on the SDCSC configuration to work passively in cooperation with the human operator or to serve as a low-cost automation solution. However, as single-degree-of-freedom systems, such SDCSC-configuration manipulators need to be designed specific to a given task. In this paper, we investigate the development of a synthesis scheme, leveraging tools from Fourier analysis and optimization, to permit the end-effectors of such manipulators to closely approximate desired closed planar paths. In particular, we note that the forward kinematics equations take the form of a finite trigonometric series in terms of the input crank rotations. The proposed Fourier-based synthesis method exploits this special structure to achieve the combined number and dimensional synthesis of SDCSC-configuration manipulators for closed-loop planar path-following tasks. Representative examples illustrate the application of this method for tracing candidate square and rectangular paths. Emphasis is also placed on conversion of computational results into physically realizable mechanism designs.

Data Driven Development of Haptic Models for Needle Biopsy Phantoms

Volume 3: Renewable Energy Systems; Robotics; Robust Control; Single Track Vehicle Dynamics and Control; Stochastic Models, Control and Algorithms in Robotics; Structure Dynamics and Smart Structures;, 2012

Needle biopsy is an important and common procedure for lesion detection or tissue extraction with... more Needle biopsy is an important and common procedure for lesion detection or tissue extraction within the human body. Physicians conducting such procedures rely primarily on the sense of "touch" (kinesthetic feedback from needle) to estimate the current needle position and organs within its vicinity. This skill takes time to acquire and mature, often by biopsies on live patients. Medical residents and fellow trainees thus have limited opportunities both in terms of real life scenarios as well as testing platforms to develop and validate their skills. This paper focuses on building a biopsy simulator for training on virtual phantoms (using both visual and force feedback) and cross validation using a real physical phantom. In order to develop a virtual-haptic model of biopsy phantom, material testing experiments were conducted to obtain motion-force profiles from an instrumented 6-DOF robot platform serving as a needle driver. The measured force-displacement data was then used to develop three types of haptic models for the phantom to calculate the force feedback for the haptic device. Neural network based models provided a more accurate force-reflection model compared to the other two methods from the literature and will form the basis of the virtual phantoms within our framework.

Radial Basis Function Network (RBFN) Approximation of Finite Element Models for Real-Time Simulation

ASME 2011 Dynamic Systems and Control Conference and Bath/ASME Symposium on Fluid Power and Motion Control, Volume 2, 2011

Nonlinearities inherent in soft-tissue interactions create roadblocks to realization of high-fide... more Nonlinearities inherent in soft-tissue interactions create roadblocks to realization of high-fidelity real-time haptics-based medical simulations. While finite element (FE) formulations offer greater accuracy over conventional spring-mass-network models, computational-complexity limits achievable simulation-update rates. Direct interaction with sensorized physical surrogates, in offline or online modes, allows a temporary sidestepping of computational issues but hinders parametric analysis and true exploitation of a simulation-based testing paradigm. Hence, in this paper, we develop Radial-Basis Neural-Network approximations, to FE-model data within a Modified Resource Allocating Network (MRAN) framework. Real-time simulation of the reduced order neural-network approximations at high temporal resolution provided the haptic-feedback. Validation studies are being conducted to evaluate the kinesthetic realism of these models with medical experts.

Robotic Minimally Invasive Surgical skill assessment based on automated video-analysis motion studies

2012 4th IEEE RAS & EMBS International Conference on Biomedical Robotics and Biomechatronics (BioRob), 2012

Abstract²Assessment of surgical skill, arising from the synthesis of the cognitive and sensorimot... more Abstract²Assessment of surgical skill, arising from the synthesis of the cognitive and sensorimotor capabilities of the surgeon, has predominantly been a subjective task. Development of quantitative metrics-of-performance with clinical relevance and other desirable characteristics (repeatability and stability) has always lagged behind. New opportunities for objective and automated assessment frameworks have arisen by virtue of technological advances in computation, video-processing, and data-acquisition, especially in the robotic Minimally Invasive Surgical (rMIS) realm.

An Engineering Approach to Utilizing Bio-Inspiration in Robotics Applications

Biologically Inspired Design, 2013

Parallel Architecture Manipulators for Use in Masticatory Studies

International Journal of Intelligent Mechatronics and Robotics, 2011

Product of tracking experts for visual tracking of surgical tools

2013 IEEE International Conference on Automation Science and Engineering (CASE), 2013

This paper proposes a novel tool detection and tracking approach using uncalibrated monocular sur... more This paper proposes a novel tool detection and tracking approach using uncalibrated monocular surgical videos for computer-aided surgical interventions. We hypothesize surgical tool end-effector to be the most distinguishable part of a tool and employ state-of-the-art object detection methods to learn the shape and localize the tool in images. For tracking, we propose a Product of Tracking Experts (PoTE) based generalized object tracking framework by probabilistically-merging tracking outputs (probabilistic/non-probabilistic) from timevarying numbers of trackers. In the current implementation of PoTE, we use three tracking experts -point-feature-based, region-based and object detection-based. A novel point featurebased tracker is also proposed in the form of a voting based bounding box geometry estimation technique building upon point-feature correspondences. Our tracker is causal which makes it suitable for real-time applications. This framework has been tested on real surgical videos and is shown to significantly improve upon the baseline results.

Surgical tool attributes from monocular video

2014 IEEE International Conference on Robotics and Automation (ICRA), 2014

HD Video from the (monocular or binocular) endoscopic camera provides a rich real-time sensing ch... more HD Video from the (monocular or binocular) endoscopic camera provides a rich real-time sensing channel from surgical site to the surgeon console in various Minimally Invasive Surgery (MIS) procedures. However, a real-time framework for video understanding would be critical for tapping into the rich information-content provided by the non-invasive and well-established digital endoscopic video-streaming modality. While contemporary research focuses on enhancing aspects such as tool-tracking within the challenging visual scenes, we consider the associated problem of using that rich (but often compromised) streaming visual data to discover the underlying semantic attributes of the tools.

Virtual musculoskeletal scenario-testing case-studies

2008 Virtual Rehabilitation, 2008

Doctors, dentists, nurses, athletic trainers, occupational therapists and allied health-care prof... more Doctors, dentists, nurses, athletic trainers, occupational therapists and allied health-care professionals are expected to learn the linkage between anatomy, physiology and ultimately functional-performance of muscles i.e. how muscles affect movement or which sets of muscles carry various loads. However the extent of understanding of functionalperformance that can be imparted in a didactic-lecture or cadaver-lab setting of a "Gross Anatomy" class is limited. Hence we seek to create the architecture and algorithms for scaffolded interaction with human musculoskeletal simulation models (virtual prototypes) that can make varied "what-if" type analyses and hypothesis-testing possible. This is very pertinent in the context of the target audience of healthcare professionals who may lack prior exposure to such virtual computational scenario testing tools. Providing such access is vital to training of the next generation of health care professionals to leverage ubiquitous computing and the quantitative-paradigm.

Role of Automated Symbolic Generation of Equations of Motion in Mechanism and Robotics Education

Volume 2: 34th Annual Mechanisms and Robotics Conference, Parts A and B, 2010

In recent years there has been a significant increase in the variety and complexity of Articulate... more In recent years there has been a significant increase in the variety and complexity of Articulated-Multi-Body-Systems (AMBS) used for various applications. There is also increased interest in the model-based design-refinement and controller-development, which is critically dependent upon availability of underlying plantmodels.

Role of Automated Symbolic Generation of Plant Models in Control Education

ASME 2010 Dynamic Systems and Control Conference, Volume 2, 2010

CAD-enhanced workspace optimization for parallel manipulators: A case study

2010 IEEE International Conference on Automation Science and Engineering, 2010

The challenges of workspace determination of parallel manipulators (PMs) arise principally from t... more The challenges of workspace determination of parallel manipulators (PMs) arise principally from the lack of analytical solutions of the forward kinematics. The inverseposition kinematics based approach for determining workspace tends to be inefficient, time consuming and unsophisticated. In this paper, we present a geometry-based method for accurate and computationally effective calculation of the workspace of a constrained parallel manipulator. We illustrate how boolean geometric operations can simplify the process of finding the workspace and optimizing the designs. Comparative performance studies, in terms of accuracy and computational performance, are performed to benchmark the approach against more conventional methods. Finally, we examine ways to further automate the process using a CAD package.

Random Matrix Approach: Toward Probabilistic Formulation of the Manipulator Jacobian

Journal of Dynamic Systems, Measurement, and Control, 2014

In this paper, we formulate the manipulator Jacobian matrix in a probabilistic framework based on... more In this paper, we formulate the manipulator Jacobian matrix in a probabilistic framework based on the random matrix theory (RMT). Due to the limited available information on the system fluctuations, the parametric approaches often prove to be inadequate to appropriately characterize the uncertainty. To overcome this difficulty, we develop two RMTbased probabilistic models for the Jacobian matrix to provide systematic frameworks that facilitate the uncertainty quantification in a variety of complex robotic systems. One of the models is built upon direct implementation of the maximum entropy principle that results in a Wishart random perturbation matrix. In the other probabilistic model, the Jacobian matrix is assumed to have a matrix-variate Gaussian distribution with known mean. The covariance matrix of the Gaussian distribution is obtained at every time point by maximizing a Shannon entropy measure (subject to Jacobian norm and covariance positive semidefiniteness constraints). In contrast to random variable/vector based schemes, the benefits of the proposed approach now include: (i) incorporating the kinematic configuration and complexity in the probabilistic formulation; (ii) achieving the uncertainty model using limited available information; (iii) taking into account the working configuration of the robotic systems in characterization of the uncertainty; and (iv) realizing a faster simulation process. A case study of a 2R serial manipulator is presented to highlight the critical aspects of the process.

Formation optimization for a fleet of wheeled mobile robots — A geometric approach

Robotics and Autonomous Systems, 2009

Tight formation-based operations are critical in several emerging applications for robot collecti... more Tight formation-based operations are critical in several emerging applications for robot collectives -ranging from cooperative payload transport to synchronized distributed data-collection. In this paper, we investigate the optimal relative layout for members of a team of Differentially-Driven Wheeled Mobile Robots (DD-WMRs) moving in formation for ultimate deployment in cooperative payload transport tasks.

Modular and Recursive Kinematics and Dynamics for Parallel Manipulators

Multibody System Dynamics, 2005

Constrained multibody systems typically feature multiple closed kinematic loops that constrain th... more Constrained multibody systems typically feature multiple closed kinematic loops that constrain the relative motions and forces within the system. Typically, such systems possess far more articulated degrees-of-freedom (within the chains) than overall end-effector degrees-of-freedom. Thus, actuation of a subset of the articulations creates mixture of active and passive joints within the chain. The presence of such passive joints interferes with the effective modular formulation of the dynamic equations-of-motion in terms of a minimal set of actuator coordinates as well the subsequent recursive solution for both forward and inverse dynamics applications.

Screw-theoretic analysis models for felid jaw mechanisms

Mechanism and Machine Theory, 2008

In this paper, we examine the development of quasi-static computational models for musculoskeleta... more In this paper, we examine the development of quasi-static computational models for musculoskeletal analysis, leveraging screw-theoretic techniques traditionally employed for the analysis of articulated multibody systems (MBS). The case study of analysis of bite-and muscle-forces in the articulated jaws of members of the felid (cat) family is used to highlight the critical aspects. In particular, musculoskeletal systems with multiple muscles superimposed on an underlying articulated skeleton share many features with the subclass of cable actuated parallel MBS (including redundancy in actuation and unidirectional nature of actuation forces). The screw-theoretic formulation facilitates the development of a computational model for resolving such redundancy while retaining explicit geometric meaning in terms of lines-of-action, motions and forces. The low-computational-complexity of the ensuing quasi-static models makes them well-suited both for: (a) iterative/parametric studies of the roles of geometry (muscle locations) or physiology (muscle-parameters) on skeletal loaddistributions, as well as (b) implementing online inverse-dynamics-based muscle-force planners for biomimetic physical prototypes. A MATLAB Graphical User Interface was also developed to aid lay users (non-computational scientists) in performing iterative parametric force optimization and muscle location studies.

Modular and distributed forward dynamic simulation of constrained mechanical systems – A comparative study

Mechanism and Machine Theory, 2007

In this paper, we examine the modular development of two alternate methods for distributed comput... more In this paper, we examine the modular development of two alternate methods for distributed computation of the forward dynamics simulations of constrained mechanical systems. We exploit the natural spatial parallelism of closedchain linkages, initially, for the modular development of overall dynamics, and subsequently, for the distributed numerical simulation of the dynamics. Traditionally, the numerical simulation problem of constrained mechanical systems has been treated as two separate stages: the problem of algorithm development and the subsequent numerical problem of advancing the discretized differential equations in time. However the potential numerical instabilities arising from the formulation stiffness of the algorithm development stage has the potential to hinder the subsequent numerical integration stage. These aspects are also explored during the evaluation of the two alternative approaches for the distributed forward dynamics simulation of a four-bar linkage. A series of tests were performed on a real-time synchronized distributed computational system (RT-LAB) to evaluate the performance of both methods of simulation and preliminary results to quantify the overall computational efficiency and accuracy are presented.

Evaluation of robotic minimally invasive surgical skills using motion studies

Journal of Robotic Surgery, 2013

Robotic Minimally Invasive Surgery, and the engendered computer-integration, offers unique opport... more Robotic Minimally Invasive Surgery, and the engendered computer-integration, offers unique opportunities for quantitative computer-based surgical-performance evaluation. In this work, we examine extension of traditional manipulative skill assessment, having deep roots in performance evaluation in manufacturing industries, for applicability to robotic surgical skill evaluation. This method relies on: defining task-level segmentation of modular sub-tasks/micro-motions called &amp;amp;amp;amp;#39;Therbligs&amp;amp;amp;amp;#39; that can be combined to perform a given task; and analyzing intra- and inter-user performance variance by studying surgeons&amp;amp;amp;amp;#39; performance over each &amp;amp;amp;amp;#39;Therbligs&amp;amp;amp;amp;#39;. Any of the performance metrics of macro-motions-from motion-economy, tool motion measurements to handed-symmetry-can now be extended over the micro-motion temporal segments. Evaluation studies were based on video recordings of surgical tasks in two settings: first, we examined performance of two representative manipulation exercises (peg board and pick-and-place) on a da Vinci surgical SKILLS simulator. This affords a relatively-controlled and standardized test-scenarios for surgeons with varied experience-levels. Second, task-sequences from real surgical videos were analyzed with a list of predefined &amp;amp;amp;amp;#39;Therbligs&amp;amp;amp;amp;#39; in order to investigate its overall usefulness.

Kinematic and Kinetostatic Synthesis of Planar Coupled Serial Chain Mechanisms

Journal of Mechanical Design, 2002

a number of manipulation tasks. Such SDCSC mechanisms take advantage of the hardware constraints ... more a number of manipulation tasks. Such SDCSC mechanisms take advantage of the hardware constraints between the articulations of a serial-chain linkage, created using gear-trains or belt/pulley drives, to guide the end-effector motions and forces. In this paper, we examine the dimensional synthesis of such SDCSC mechanisms to perform desired planar manipulation tasks, taking into account task specifications on both end-effector motions and forces. Our solution approach combines precision point synthesis with optimization to realize optimal mechanisms, which satisfy the design specifications exactly at the selected precision points and approximate them in the least-squares sense elsewhere along a specified trajectory. The designed mechanisms can guide a rigid body through several positions while supporting arbitrarily specified external loads. Furthermore, torsional springs are added at the joints to reduce the overall actuation requirements and to enhance the task performance. Examples from the kinematic and the kinetostatic synthesis of planar SDCSC mechanisms are presented to highlight the benefits. Fig. 4 "a… Schematic of operation of the head-controlled feeding device. "b… Physical and mathematical models of a 2-link SDCSC mechanism.

Kinematic Synthesis of Spatial R-R Dyads for Path Following With Applications to Coupled Serial Chain Mechanisms

Journal of Mechanical Design, 2001

The dimensional synthesis of a spatial two revolute jointed dyad for path following tasks with ap... more The dimensional synthesis of a spatial two revolute jointed dyad for path following tasks with applications to coupled serial chain mechanisms is presented. The precision point synthesis equations obtained using the rotation matrix approach form a rank-deficient linear system in the link-vector components. The nullspace of this rank-deficient linear system is derived analytically and interpreted geometrically. The nullspace vectors lead to the specification of additional constraints via the so-called auxiliary equations and to the solution of the linear system of equations. The geometry also allows the derivation of a closed form solution for the three design position problem. Finally, optimal path following by coupled R-R dyads is achieved by optimization over the free choice variables.

Fourier Methods for Kinematic Synthesis of Coupled Serial Chain Mechanisms

Journal of Mechanical Design, 2005

Single degree-of-freedom coupled serial chain (SDCSC) mechanisms are a class of mechanisms that c... more Single degree-of-freedom coupled serial chain (SDCSC) mechanisms are a class of mechanisms that can be realized by coupling successive joint rotations of a serial chain linkage, by way of gears or cable-pulley drives. Such mechanisms combine the benefits of single degree-of-freedom design and control with the anthropomorphic workspace of serial chains. Our interest is in creating articulated manipulation-assistive aids based on the SDCSC configuration to work passively in cooperation with the human operator or to serve as a low-cost automation solution. However, as single-degree-of-freedom systems, such SDCSC-configuration manipulators need to be designed specific to a given task. In this paper, we investigate the development of a synthesis scheme, leveraging tools from Fourier analysis and optimization, to permit the end-effectors of such manipulators to closely approximate desired closed planar paths. In particular, we note that the forward kinematics equations take the form of a finite trigonometric series in terms of the input crank rotations. The proposed Fourier-based synthesis method exploits this special structure to achieve the combined number and dimensional synthesis of SDCSC-configuration manipulators for closed-loop planar path-following tasks. Representative examples illustrate the application of this method for tracing candidate square and rectangular paths. Emphasis is also placed on conversion of computational results into physically realizable mechanism designs.