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Venkat Krovi

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21 papers
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21

ICRA Conference 2025 Conference Paper

Deep Reinforcement Learning for Coordinated Payload Transport in Biped-Wheeled Robots

  • Dhruv K. Mehta 0001
  • Ajinkya Joglekar
  • Venkat Krovi

Coordinated payload transport via a fleet of modular wheeled mobile robots offers flexibility for handling larger loads in indoor and outdoor environments. Biped-wheeled robots have recently emerged as a viable architecture for an independent/stand-alone wheeled mobile robot. In this work, we explore the use of two biped-wheeled robots that can leverage their mobility and maneuvarability for enhanced spatial pose control and stabilization for various payload transport tasks. However, coordinated control of multiple articulated wheeled robots for path tracking of a payload presents significant (and potentially competing) challenges, including kinematic redundancy, stability concerns, relative motion between the payload and robots, and precise motion control to achieve effective coordination. To address these challenges, we propose a Deep Reinforcement Learning (DRL) framework to develop the motion-plans for the system. In particular, this approach generates the ego robot's body twist and the follower robot's relative twist with respect to the ego robot. By formulating the action space of the follower robot as a relative twist, our approach facilitates pairwise interactions between robots. Furthermore, we use only relative pose information and the errors as states for the DRL controller, thereby making it agnostic to initial conditions and avoiding explicit dependency on absolute pose. We validate our approach through simulations conducted in Isaac Sim and on hardware using Diablo biped-wheeled robots with zero-shot transfer, demonstrating effective payload path tracking across varying parameters.

ICRA Conference 2025 Conference Paper

Digital Twins Meet the Koopman Operator: Data-Driven Learning for Robust Autonomy

  • Chinmay Vilas Samak
  • Tanmay Vilas Samak
  • Ajinkya Joglekar
  • Umesh Vaidya
  • Venkat Krovi

Contrary to on-road autonomous navigation, off-road autonomy is complicated by various factors ranging from sensing challenges to terrain variability. In such a milieu, data-driven approaches have been commonly employed to capture intricate vehicle-environment interactions effectively. However, the success of data-driven methods depends crucially on the quality and quantity of data, which can be compromised by large variability in off-road environments. To address these concerns, we present a novel methodology to recreate the exact vehicle and its target operating conditions digitally for domain-specific data generation. This enables us to effectively model off-road vehicle dynamics from simulation data using the Koopman operator theory, and employ the obtained models for local motion planning and optimal vehicle control. The capabilities of the proposed methodology are demonstrated through an autonomous navigation problem of a 1: 5 scale vehicle, where a terrain-informed planner is employed for global mission planning. Results indicate a substantial improvement in off-road navigation performance with the proposed algorithm (↑ 5. 84×) and underscore the efficacy of digital twinning in terms of improving the sample efficiency (↑ 3. 2×) and reducing the sim2real gap (↓ 5. 2%).

ICRA Conference 2025 Conference Paper

Online Identification of Skidding Modes with Interactive Multiple Model Estimation

  • Amey A. Salvi
  • Pardha Sai Krishna Ala
  • Jonathon M. Smereka
  • Mark J. Brudnak
  • David J. Gorsich
  • Matthias J. Schmid
  • Venkat Krovi

Skid-steered wheel mobile robots (SSWMRs) operate in a variety of outdoor environments exhibiting motion behaviors dominated by the effects of complex wheel-ground interactions. Characterizing these interactions is crucial from both the immediate robot autonomy perspective (for motion prediction and control) and a long-term predictive maintenance and diagnostics perspective. An ideal solution entails capturing precise state measurements for decisions and controls, which is considerably difficult, especially in increasingly unstructured outdoor regimes of operations for these robots. In this milieu, a framework to identify pre-determined discrete modes of operation can considerably simplify the motion model identification process. To this end, we propose an interactive multiple model (IMM) based filtering framework to probabilistically identify predefined robot operation modes that could arise due to traversal in different terrains or loss of wheel traction.

IROS Conference 2023 Conference Paper

Data-Driven Modeling and Experimental Validation of Autonomous Vehicles Using Koopman Operator: Distribution A: Approved for Public Release; Distribution Unlimited. OPSEC # 7248

  • Ajinkya Joglekar
  • Sarang Sutavani
  • Chinmay Vilas Samak
  • Tanmay Vilas Samak
  • Krishna Chaitanya Kosaraju
  • Jonathon M. Smereka
  • David J. Gorsich
  • Umesh Vaidya

This paper presents a data-driven framework to discover underlying dynamics on a scaled F1TENTH vehicle using the Koopman operator linear predictor. Traditionally, a range of white, gray, or black-box models are used to develop controllers for vehicle path tracking. However, these models are constrained to either linearized operational domains, unable to handle significant variability or lose explainability through end-2-end operational settings. The Koopman Extended Dynamic Mode Decomposition (EDMD) linear predictor seeks to utilize data-driven model learning whilst providing benefits like explainability, model analysis and the ability to utilize linear model-based control techniques. Consider a trajectory-tracking problem for our scaled vehicle platform. We collect pose measurements of our F1TENTH car undergoing standard vehicle dynamics benchmark maneuvers with an OptiTrack indoor localization system. Utilizing these uniformly spaced temporal snapshots of the states and control inputs, a data-driven Koopman EDMD model is identified. This model serves as a linear predictor for state propagation, upon which an MPC feedback law is designed to enable trajectory tracking. The prediction and control capabilities of our framework are highlighted through real-time deployment on our scaled vehicle.

ICRA Conference 2023 Conference Paper

Reinforcement Learning Control of a Reconfigurable Planar Cable Driven Parallel Manipulator

  • Adhiti Raman
  • Amey A. Salvi
  • Matthias J. Schmid
  • Venkat Krovi

Cable driven parallel robots (CDPRs) are often challenging to model and to dynamically control due to the inherent flexibility and elasticity of the cables. The additional inclusion of online geometric reconfigurability to a CDPR results in a complex underdetermined system with highly non-linear dynamics. The necessary (numerical) redundancy resolution requires multiple layers of optimization rendering its application computationally prohibitive for real-time control. Here, deep reinforcement learning approaches can offer a model-free framework to overcome these challenges and can provide a real-time capable dynamic control. This study discusses three settings for a model-free DRL implementation in dynamic trajectory tracking: (i) for a standard non-redundant CDPR with a fixed workspace; (ii) in an end-to-end setting with redundancy resolution on a reconfigurable CDPR; and (iii) in a decoupled approach resolving kinematic and actuation redundancies individually.

ICRA Conference 2022 Conference Paper

3D Printing of Concrete with a Continuum Robot Hose Using Variable Curvature Kinematics

  • Manu Srivastava
  • Jake Ammons
  • Abdul B. Peerzada
  • Venkat Krovi
  • Prasad Rangaraju
  • Ian D. Walker

We present a novel application of continuum robots acting as concrete hoses to support 3D printing of cementitious materials. An industrial concrete hose was fitted with a cable harness and remotely actuated via tendons. The resulting continuum hose robot exhibited non constant curvature. In order to account for this, a new geometric approach to modeling variable curvature inverse kinematics using Euler curves is introduced herein. The new closed form model does not impose any additional computational cost compared to the constant curvature model and results in a marked improvement in the observed performance. Experiments involving 3D printing with cementitious mortar using a continuum hose robot were also conducted.

IROS Conference 2020 Conference Paper

Enabling Robot to Assist Human in Collaborative Assembly using Convolutional Neural Networks

  • Yi Chen
  • Weitian Wang
  • Venkat Krovi
  • Yunyi Jia

Human-robot collaborative assembly consists of humans and automated robots, who cooperate with each other to accomplish complex assembly tasks, which are difficult for either humans or robots to accomplish alone. There has been some success in statistics-based and optimization-based approaches to realize human-robot collaboration. However, they usually need a set of complex modeling and setup efforts and the robots usually need to be programmed by a well-trained expert. In this paper, we take a new approach by introducing convolutional neural networks (CNN) into the teaching- learning-collaboration (TLC) model for collaborative assembly tasks. The proposed approach can alleviate the need for complex modeling and setup compared to the existing approaches. It can collect and automatically label the data from human demonstrations and then train a CNN-based robot assistance model to make the robot assist humans in the assembly process in real-time. We have experimentally verified our proposed approach on a human-robot collaborative assembly platform and the results suggest that the robot can successfully learn from human demonstrations to automatically generate right actions to assist human in accomplishing assembly tasks.

IROS Conference 2015 Conference Paper

Modeling and control of a novel home-based cable-driven parallel platform robot: PACER

  • Aliakbar Alamdari
  • Venkat Krovi

This paper focuses on various control strategies for a modular cable-articulated parallel robotic manipulator called PACER (Parallel Articulated-Cable Exercise Robot). The proposed robotic device is comprised of multiple cables and a single antagonistically actuated prismatic joint which connects a six degrees-of-freedom moving platform to a fixed base. This novel design provides an attractive architecture for implementation of a home-based rehabilitation device as an alternative to expensive serial robots. In this paper, after deriving the dynamic equations via Newton-Euler formulation, the development of different control strategies in the context of upper limb rehabilitation in three-dimensional space will be examined. The various control modes include: (i) passive mode through feedback linearization for recovering functionalities of the joints at the first step of post-stroke rehabilitation, (ii) active mode via admittance controller for assisting patient to do tasks better, and finally (iii) resistive mode via stiffness controller for increasing the muscle strength. This is now evaluated via a simulation case-study and development of a physical testbed is underway. Since the human arm consists of seven degrees-of-freedom, and daily activities of upper limbs are combination of motions of these simple joints, this proposed design with various control strategies has enormous potential for neurological remapping and brain plasticity in post-stroke patients with upper limb injuries.

ICRA Conference 2015 Conference Paper

Surgical tool pose estimation from monocular endoscopic videos

  • Suren Kumar
  • Javad Sovizi
  • Madusudanan Sathia Narayanan
  • Venkat Krovi

Surgical tool pose estimation has been proven to be useful for high- and low- level feedback tasks including safety-enhancement, semantic feedback and surgical skill assessment. Tool pose estimation using monocular camera input is a well-studied research problem as the monocular camera is one of the ubiquitous sensor across the spectrum of robotic devices. Current state-of-the art methods for visual tool pose estimation are computationally expensive and require elaborate geometric and appearance models of surgical tools. We propose a visual tool pose estimation method that maps the visual bounding box to the 3D tool pose without any explicit knowledge of tool geometry using Gaussian process regression. The proposed approach can be generalized to any surgical tool and provides tool pose estimates with a variance estimate in real-time. We demonstrate rigorous evaluation of the method under various conditions that might effect the estimation process. In order to evaluate the algorithm, we have instrumented a standard box trainer kit with two laparoscopic tools to get simultaneous ground truth pose and a video feed.

IROS Conference 2014 Conference Paper

Kinetostatic optimization for an adjustable four-bar based articulated leg-wheel subsystem

  • Aliakbar Alamdari
  • Javad Sovizi
  • Seung-kook Jun
  • Venkat Krovi

High mobility, maneuverability and obstacle surmounting capabilities are highly desirable features for rough-terrain locomotion systems. In past work, we examined kinetostatic optimization of candidate articulated leg-wheel subsystem designs (based on the four-bar mechanism) for enhancing locomotion capabilities of land-based vehicles. Our goal was to: (i) achieve the greatest motion-ranges between wheel axle and chassis while (ii) reducing the overall actuation requirements by spring assist. In the current work, we examine the possibility of enhancing this terrain-accommodation by: (i) proposing an “adjustable four-bar” articulated-leg-wheel subsystem; (ii) with active-structural control to actively change subsystem parameters during the terrain traversal. Multiple leg-wheel design- parameters can affect the peak-static torque requirements as well as dynamic-bandwidth requirements for the leg-wheel actuation. The presented results compare and contrast online-structural reconfiguration planning (with multiple alternate active-adjustments) to reduce actuation requirements for a predetermined/sensed terrain traversal profile.

ICRA Conference 2014 Conference Paper

Random matrix based uncertainty model for complex robotic systems

  • Javad Sovizi
  • Aliakbar Alamdari
  • Sonjoy Das
  • Venkat Krovi

In this paper, we generalize our random matrix based (RM-based) uncertainty model for manipulator Jacobian matrix to the dynamic model of the robotic systems. Conventional random variable based (RV-based) schemes require a detailed knowledge of the system parameters variation and may be not able to fully characterize the uncertainties of the complex dynamic systems. However, the proposed RM-based approach provides a probabilistic framework for systematic characterization of the uncertainties in the complex systems with limited available information. Moreover, RM-based uncertainty model is an efficient mathematical tool that ensures the kinematic and dynamic consistency and takes into account the system complexity, configuration, structural inter-dependencies, etc. The application of the RM-based uncertainty model is investigated using an example of kinematically redundant planar parallel manipulator (3-(P)RRR). The simulation results are compared with those obtained through conventional RV-based approach and the effectiveness of the proposed method is discussed.

ICRA Conference 2014 Conference Paper

Stiffness modulation exploiting configuration redundancy in mobile cable robots

  • Xiaobo Zhou
  • Seung-kook Jun
  • Venkat Krovi

In this paper, we investigate the modulation of task space stiffness of mobile cable robots with elastic cables. The elasticity is introduced via springs connected in series with non-extensible cables. The benefit of such series elastic cables include tension control without using force sensors and tension redistribution. However, elasticity also reduces positioning accuracy and makes the system more prone to disturbances. Therefore, careful stiffness modulation is needed for better performance. We exploit the configuration redundancy in mobile cable robots to optimize certain desired task space stiffness criterion. Both simulation and experimental results are presented for validation.

ICRA Conference 2014 Conference Paper

Surgical tool attributes from monocular video

  • Suren Kumar
  • Madusudanan Sathia Narayanan
  • Pankaj Singhal
  • Jason J. Corso
  • Venkat Krovi

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. Directly analyzing the surgical videos to extract more realistic attributes online can aid in the decision-making and feedback aspects. We propose a novel probabilistic attribute labelling framework with Bayesian filtering to identify associated semantics (open/closed, stained with blood etc.) to ultimately give semantic feedback to the surgeon. Our robust video-understanding framework overcomes many of the challenges (tissue deformations, image specularities, clutter, tool-occlusion due to blood and/or organs) under realistic in-vivo surgical conditions. Specifically, this manuscript performs rigorous experimental analysis of the resulting method with varying parameters and different visual features on a data-corpus consisting of real surgical procedures performed on patients with da Vinci Surgical System [9].

ICRA Conference 2012 Conference Paper

Analysis framework for cooperating mobile cable robots

  • Xiaobo Zhou
  • Chin Pei Tang
  • Venkat Krovi

Cable robots form a class of parallel architecture robots with significant benefits including simplicity of construction, large workspace, significant payload capacity and end effector stiffness. While conventional cable robots have fixed bases, we seek to explore inclusion of mobility into the bases (in the form of gantries, and/or vehicle bases) which can significantly further enhance the capabilities of cable robots. However, this also introduces redundancy and complexity into the system which needs to be carefully analyzed and resolved. To this end, we propose a generalized modeling framework for systematic design and analysis of cooperative mobile cable robots, building upon knowledge base of multi-fingered grasping, and illustrate it with a case study of four cooperating gantry mounted cable robots transporting a planar payload.

ICRA Conference 2010 Conference Paper

Enhanced trajectory tracking control with active lower bounded stiffness control for cable robot

  • Kun Yu
  • Leng-Feng Lee
  • Chin Pei Tang
  • Venkat Krovi

Cable robots have seen considerable recent interest ensuing from their ability to combine a large workspace with significant payload capacity. However, the cables can apply forces to the end-effector only when they are in tension, and thus form a subclass of control problems requiring unilateral control inputs. Furthermore, actuation redundancy occurs when surplus cables are introduced within the system. On one hand, such redundancy needs to be carefully resolved for accurate tracking of the task. On the other hand, it allows the redistribution of the actuation forces to satisfy some secondary criteria. In this paper, we apply such redundancy for enhanced trajectory tracking by actively controlling the task stiffness of the end-effector. The scheme allow us to specify a lower bound of the task stiffness, which is intended to provide improved trajectory tracking and disturbance rejection performance. Finally, we illustrate the improved control performance within a virtual prototype cosimulation framework.

ICRA Conference 2005 Conference Paper

Comparison of Alternate Methods for Distributed Motion Planning of Robot Collectives within a Potential Field Framework

  • Leng-Feng Lee
  • Rajankumar Bhatt
  • Venkat Krovi

In this paper, we evaluate the performance of two candidate formulations for distributed motion planning of robot collectives within an Artificial Potential Field (APF) framework. We exploit the parallel between the formulation of motion planning for group of robots coupled by constraints and the forward dynamics simulation of constrained multibody systems to develop the candidate approaches. We compare and contrast these approaches on the basis of ease of formulation, distribution of computation and overall computational accuracy. Traditionally penalty formulations have enjoyed a prominent position in motion planning of robot collectives due to their ease of formulation, decentralization and scalability. However, the instabilities introduced in the form of “formulation stiffness” at the algorithm development stage have the potential to hinder the subsequent control. Representative results from the distributed motion planning for a group of 3 point-mass robots moving in formation to a desired target location are used to highlight the differences.

ICRA Conference 2004 Conference Paper

Decentralized Kinematic Control of Payload by a System of Mobile Manipulators

  • Chin Pei Tang
  • Rajankumar Bhatt
  • Venkat Krovi

In this paper, we examine creation of a decentralized kinematic control scheme for a composite system of two (or more) wheeled mobile manipulators that can team up to cooperatively transport a common payload. Each mobile manipulator module consists of a differentially driven wheeled mobile robot (WMR) with a mounted planar two-degree-of-freedom (d. o. f) manipulator. A composite multi-degree-of-freedom system is formed when a payload is placed at the end effectors of multiple such modules with significant advantages. However, the nonholonomic/holonomic constraints and active/passive components within the composite vehicle need careful treatment for realizing the payload transport task. Hence, we first verify that arbitrary desired end-effector motions can be accommodated, within the feasible motion distributions of the articulations and the wheeled base. Then, we develop motion-plans by which this desired end-effector motion could be actively realized, using only the limited active motion-distribution of the differentially driven wheels. Finally, we deploy this in the form of a two-level hierarchical control framework, with an upper-level planning of the steerable active vector-fields and a lower-level posture stabilization control of the individual WMRs. Preliminary experimental results from the decentralized-control implementation for a two-module composite vehicle are also presented.

ICRA Conference 2004 Conference Paper

Geometric Motion Planning and Formation Optimization for a Fleet of Nonholonomic Wheeled Mobile Robots

  • Rajankumar Bhatt
  • Chin Pei Tang
  • Venkat Krovi

In this paper, we present a geometric method for motion planning for a fleet of differentially-driven wheeled mobile robots moving in formation, which explicitly takes into account their nonholonomic constraints. The relative position within the formation induces different motion plans for each individual wheeled mobile robot (WMR). We can quantitatively evaluate the performance of such induced motion plans using suitable metrics defined for the motions of each WMR. These performance metrics in cumulative form or individual form are used to optimize the overall formation (i. e. , their relative positions) for performing a given task. The approach is well suited for online implementation and is demonstrated using case studies.

IROS Conference 2003 Conference Paper

Development and testing of a low-cost diagnostic tool for upper limb dysfunction

  • Pravin Nair
  • Chetan Jadhav
  • Venkat Krovi

The overall goal of our research is to create a low-cost, home-based diagnostic and rehabilitation tool to assist the rapid functional recovery of people with upper limb (UL) dysfunction (due to muscular dystrophy and stroke)-the diagnostic aspect of which is discussed in this paper. Viewed in the broader context of robot-assisted neurorehabilitation, the proposed framework takes advantage of manipulation of an instrumented manipulandum along prescribed movement patterns to create a sensitive, quantitative, computer-based assessment/diagnostic tool. Specifically, in this paper, we discuss various aspects of an implementation using a COTS force-feedback driving wheel, interfaced to a PC to create a virtual driving environment (VDE). Coupled with the exercise/movement protocols (structured as driving exercises along paths of varying complexity), this results in creation of a low-cost, user-friendly and immersive personal-movement trainer that is well suited for deployment in patients' homes. Our initial analysis of data collected from 5 healthy subjects indicates that the tool has adequate sensitivity/resolution to distinguish even between healthy subjects and shows considerable promise for diagnosis in diseased population (which is currently underway).

IROS Conference 2001 Conference Paper

Passive reconfigurable manipulation assistive aids

  • Xichun Nie
  • Venkat Krovi

Articulated mechanical systems with multiple joints possess multiple degrees-of-freedom which are often not required for performing typical low-dimensional manipulation tasks. These excessive degrees of freedom then need to be reduced by application of constraints, either actively by suitable control or passively in hardware, prior to performance of the task. Our interest is in creating articulated manipulation assistive aids, which combine the motion flexibility due to the multiple articulations with the simplicity of reduced degree-of-freedom control due to the presence of hardware constraints. Specifically we investigate the process of design and prototyping of such reduced-degree-of-freedom manipulators whose end-effector is required to closely approximate a desired planar path. We also examine design enhancements that permit easy reconfiguration of our prototype manipulator for multiple sets of tasks, by a controlled variation of the principal structural parameters.

ICRA Conference 1994 Conference Paper

An Adaptive Mobility System for the Disabled

  • Parris S. Wellman
  • Venkat Krovi
  • Vijay Kumar 0001

A proof-of-concept prototype walking chair for the disabled is proposed with the objective of demonstrating the feasibility of a completely new approach to mobility. Our prototype system consists of a chair equipped with wheels and legs and is capable of walking on uneven terrain and circumventing obstacles. The important design considerations, the system design and an experimental prototype of a chair, are discussed. Redundancy in actuation enables the online optimization of tractive forces which enhances the adaptability of the system. >

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