A Novel Principle for Transparent Applications of Force Impulses in Cable-Driven Rehabilitation Systems
Dr. Teja Krishna Mamidi, Andrej Olenšek, Matjaž Zadravec, Matej Tomc, Teja Krishna Mamidi, Vineet Vashista, Zlatko Matjačić,
Quartile: Q2, DOI Link
View abstract ⏷
A critical requirement for rehabilitation robots is achieving high transparency in user interaction to minimize interference when assistance is unnecessary. Cable-driven systems are a compelling alternative to rigid-link robots due to their lighter weight and reduced inertia, enhancing transparency. However, controlling cable tension forces remains a significant challenge, as these forces directly affect the interaction between the user and the robot. Effective strategies must maintain low tension during non-assistive phases while preventing slackness. This paper introduces PACE-R (Passive Active CablE Robot), a novel lightweight actuation system for cable-driven rehabilitation devices. The PACE-R module utilizes remote actuation and an open-loop, discrete state control, where the cable is coupled to the motor only during active intervention. When not assisting, the cable is passively decoupled from the motor, and a low-stiffness spring maintains minimal tension, enabling high transparency. Benchtop tests showed that the module consistently produced force impulses proportional to motor input with delays not exceeding 15 ms. In the treadmill push-off assistance demonstration, PACE-R contributed about 20% to total ankle moment and power. Transparency analysis revealed negligible interference, with only 1% and 0.5% contributions to peak total ankle moment and power, respectively.
Hybrid Actuation Paradigm in Back-Assist Exoskeleton for Symmetric Loading Conditions – A Feasibility Study
Dr. Teja Krishna Mamidi, Arpeet Dhal, Teja Krishna Mamidi, Vineet Vashista
DOI Link
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The mandates of safety standards in manual material handling tasks have spurred the development and commercialization of many back-assist exoskeletons. These devices prevent back pain injuries by redistributing the applied loads, reducing the effort and fatigue in heavy and repetitive loading tasks. The majority of them employ passive and active actuation paradigms. The passive ones are known for better transparency and energy efficiency, while the active ones provide a higher degree of assistance and quickly adapt to task severities. The present work investigates the feasibility of a hybrid actuation paradigm for load-carriage under symmetric loading conditions. The preliminary results suggest that the proposed modifications to an existing passive exoskeleton effectively economize energy expenditure and improve adaptability.
A modular computational framework for the dynamic analyses of cable-driven parallel robots with different types of actuation including the effects of inertia, elasticity and damping of cables
Quartile: Q2, DOI Link
View abstract ⏷
Dynamic simulations of the cable-driven parallel robots (CDPRs) with cable models closer to reality can predict the motions of moving platforms more accurately than those with idealisations. Hence, the present work proposes an efficient and modular computational framework for this purpose. The primary focus is on the developments required in the context of CDPRs actuated by moving the exit points of cables while the lengths are held constant. Subsequently, the framework is extended to those cases where simultaneous changes in the lengths of cables are employed. Also, the effects due to the inertia, stiffness and damping properties of the cables undergoing 3D motions are included in their dynamic models. The efficient recursive forward dynamics algorithms from the prior works are utilised to minimise the computational effort. Finally, the efficacy of the proposed framework and the need for such an inclusive dynamic model are illustrated by applying it to different application scenarios using the spatial
Geometric Calibration of Cobots using Circle-Point Analysis for Surgical Applications
Dr. Teja Krishna Mamidi, Rakesh Kumar Kathiresan, Teja Krishna Mamidi, Shyam Ayyasamy, Manojkumar Lakshmanan, Mohanasankar Sivaprakasam
DOI Link
View abstract ⏷
The accuracy of the cobot and its frequent monitoring are paramount in robot-assisted surgeries (RAS). Further, on-site assurance without additional infrastructure is preferred. Hence, an in-house method that uses a thermographic camera (commonly used for navigation in RAS) for cobot calibration has been developed. Also, it is hypothesized that the overall system accuracy would be improved as the current work focuses on a good agreement between the camera and the cobot rather than just enhancing the accuracy of the cobot or camera, as in the prior works. With the well-known circle point analysis as the basis, a novel geometric calibration approach with improved identification algorithms was devised. The additional transformations required to accommodate the measurements and validations using ground truths, namely, the cobot's built-in controller and camera, were established. The efficacy of the developed approach was verified on both physical and virtual cobots. The errors in estimating the tool's position and orientation for specified joint displacements were shown to be significantly less with the calibrated parametric values than the nominal ones when using a camera. They were also shown to be on par with studies based on the cobot's built-in controller. Therefore, the proposed approach is promising and can be readily employed for cobot calibration in a surgical environment.
Active-Passive Exoskeletons for Assistive and Resistive Interventions in Human Walking
Dr. Teja Krishna Mamidi, Teja Krishna Mamidi, Yogesh Singh, Matej Tomc, Andrej Olenšek, Matjaž Zadravec, Zlatko Matjačić, Vineet Vashista
DOI Link
View abstract ⏷
Exoskeletons are developed to assist or resist human movements for augmentation and rehabilitation. In the former application, the devices share and redistribute the applied loads to reduce the natural biomechanical efforts, while in the latter, they intervene with the pathological gaits to restore normalcy. Enhancing the wearer’s experience for device acceptance and favorable functional outcomes is paramount in both cases. Hence, the primary focus of this chapter is to provide a perspective on the challenges pertinent to improving human–robot interactions when the device is operated actively or passively. The critical factors considered are the device’s transparency, i.e., its proficiency in not hindering the natural course of movements, and its efficacy in delivering the desired intervention at relevant gait phases. It is then followed by elucidating the possibility of overcoming some of these challenges with a hybrid (active-passive) paradigm and the associated limitations. These recommendations are finally supported by two case studies for resistive and assistive interventions in human walking, respectively, performed using an active portable device, “Wearable Adaptive Rehabilitation Suit (WeARS),” and a hybrid stationary device, “Ankle Exoskeleton with Treadmill Actuation for Push-Off Assistance (AN-EXTRA-PUSH).” In retrospect, this chapter also provides a comprehensive understanding of the preferred features of an ideal exoskeleton, choosing an appropriate rationale for effective intervention and design guidelines for the future.
A computational framework for the dynamic analyses of cable-driven parallel robots with feed and retrieval of cables
Quartile: Q1, DOI Link
View abstract ⏷
Accurate simulations of the motion of cable-driven parallel robots (CDPRs) are helpful in its <a class="topic-link" title="Learn more about modal analysis from ScienceDirect's AI-generated Topic Pages" href="https://www.sciencedirect.com/topics/engineering/modal-analysis">modal analysis</a>, testing robust control strategies, validating designs and estimating workspaces. On that account, a modular and computationally efficient framework to analyse the dynamics of CDPRs is developed in the present work. In contrast to the prior studies, the inertia, stiffness and <a class="topic-link" title="Learn more about damping properties from ScienceDirect's AI-generated Topic Pages" href="https://www.sciencedirect.com/topics/engineering/damping-property">damping properties</a> of the cables, along with their temporal variations caused by feeding and retrieving, are included in the dynamic model. Further, the forward dynamics algorithm designed for this purpose is recursive in nature and has linear time complexity. Finally, the efficacy of the proposed framework is established with the help of the FAST manipulator, the largest existing CDPR. Also, its extensive application potential is established via the study of the CDPR CoGiRo, which, apart from being actuated redundantly, differs drastically from the former in terms of its mass and footprint.
Forward dynamic analyses of cable-driven parallel robots with constant input with applications to their kinetostatic problems
Quartile: Q1, DOI Link
View abstract ⏷
Forward dynamic analyses of <em>cable-driven parallel robots</em> (CDPRs) are performed accounting for the spatial motions of the cables while considering their mass, sag, elastic and <a class="topic-link" title="Learn more about damping properties from ScienceDirect's AI-generated Topic Pages" href="https://www.sciencedirect.com/topics/engineering/damping-property">damping properties</a>. The winches feeding the cables are considered stationary. An efficient recursive forward dynamic algorithm is developed to perform the extremely demanding computations. As a part of this work, a solution to the kinetostatic problem of CDPRs is proposed, wherein starting with a non-equilibrium pose, the CDPR is allowed to evolve dynamically until attaining an equilibrium. This idea is demonstrated on a spatial 6-3 CDPR, the feed-support system of the <em>Five-hundred-meter aperture spherical radio telescope</em> (FAST), as well as the 8-8 CDPR, CoGiRo. Dynamic simulation of this nature using a full-scale model of the FAST manipulator is reported for the first time. The results are validated numerically, as well as against existing models, wherever feasible. Challenges involved in the modelling and computations at such a scale and the corresponding remedies are elaborated.
A comparative study of the configuration-space and actuator-space formulations of the Lagrangian dynamics of parallel manipulators and the effects of kinematic singularities on these
Quartile: Q1, DOI Link
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This paper studies the configuration-space and the actuator-space variants of the <a class="topic-link" title="Learn more about Lagrangian formulation from ScienceDirect's AI-generated Topic Pages" href="https://www.sciencedirect.com/topics/engineering/lagrangian-formulation">Lagrangian formulation</a> of dynamics of <a class="topic-link" title="Learn more about parallel manipulators from ScienceDirect's AI-generated Topic Pages" href="https://www.sciencedirect.com/topics/engineering/parallel-manipulator">parallel manipulators</a>. In particular, the effects of the gain-type <a class="topic-link" title="Learn more about singularity from ScienceDirect's AI-generated Topic Pages" href="https://www.sciencedirect.com/topics/engineering/singularities">singularity</a> and the configuration-space <a class="topic-link" title="Learn more about singularity from ScienceDirect's AI-generated Topic Pages" href="https://www.sciencedirect.com/topics/engineering/singularities">singularity</a> on the forward and inverse dynamic analyses using these formulations are studied in detail. A condition for kinematic consistency at a gain-type singularity is established. The formulations are implemented on a planar five-bar manipulator and a bi-planar Stewart platform manipulator. Extensive numerical simulations augment the analytical developments in the understanding of the dynamic behaviour of the manipulators, in both the singular and the non-singular cases.
A novel geometric analysis of the kinematics of the 3-RPS manipulator
Dr. Teja Krishna Mamidi, Teja Krishna Mamidi, Aravind Baskar, Sandipan Bandyopadhyay
DOI Link
Kinematic analysis of the 3-RPS manipulator using the geometry of plane curves
Dr. Teja Krishna Mamidi, Teja Krishna Mamidi, Aravind Baskar, Sandipan Bandyopadhyay
