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Fault accommodation in compliant quadruped robot through a moving appendage mechanism
Gor, M.M.,Pathak, P.M.,Samantaray, A.K.,Yang, J.-M.,Kwak, S.W. Elsevier 2018 Mechanism and machine theory Vol.121 No.-
<P><B>Abstract</B></P> <P>Quadruped robots provide better stability and speed in comparison to other legged robots. However, its joint actuator or sensor failure severely affects locomotion. Strategies for actuator and sensor fault accommodation in a compliant legged quadruped are presented here. A pair of orthogonally mounted moving appendages mechanism is proposed here to accommodate locked joint failure. These appendages as rack mounted inertias perform controlled motion during actuator failure. A strategy for sensor fault accommodation is also presented. A three-dimensional multi-body dynamics model of quadruped robot and its fault accommodation strategies are developed using bond graph modeling approach. The control performance is validated both through simulations and experiments.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Locked-joint and sensor faults of a quadruped robot are detected and isolated. </LI> <LI> Fault tolerant operation of a quadruped robot is considered for various missions. </LI> <LI> Actuator faults are accommodated with controlled moving appendages. </LI> <LI> Sensor fusion is used to reconstruct faulty sensor data. </LI> <LI> Online system reconfiguration is validated using simulations and experiments. </LI> </UL> </P>
Posture Control Strategy of a Platform using a RP Manipulator
M. M. Gor,P. M. Pathak,A. K. Samantaray,J.-M. Yang,S. W. Kwak 제어로봇시스템학회 2014 제어로봇시스템학회 국제학술대회 논문집 Vol.2014 No.10
This paper is an attempt to develop a posture control strategy for quadruped robot. Here, a concept of posture control is proposed, in which, a revolute and prismatic (RP) manipulator with payload at the end is used to control the body orientation. For the said analysis necessary model is developed in the bond graph and efficacy of the proposed strategies is validated through simulation results of the developed model.
Control of compliant legged quadruped robots in the workspace
Gor, M M,Pathak, P M,Samantaray, A K,Yang, J-M,Kwak, S W SAGE Publications 2015 Simulation Vol.91 No.2
<P>Locomotion control of a quadruped robot requires a well-defined gait pattern (i.e., a coordinated actuation of its four legs in some particular fashion with respect to time). It is of practical importance to move the leg tips in a desired trajectory in order to achieve specific objectives such as to avoid obstacles, minimize energy consumption and locomotion time. Along with body displacement, body orientation is an equally important limit parameter during each leg step of the gait pattern. There are several possible gait patterns that maintain stable and aesthetically pleasing locomotion, and most of these are biologically inspired. This article presents quadruped locomotion control in the workspace through a novel control scheme in which the leg forward motion is controlled in the workspace while the body forward motion is controlled by providing the required effort directly to the joint actuators. In this control approach, the leg tip trajectory error drives a proportional-integral controller that is then transformed through the Jacobian to generate the corrective joint torques. For the body forward motion, leg motion is arrested and the joints are provided with opposite motion, which are controlled by a proportional-integral-derivative controller. The proposed method is simple and easy to implement in the workspace. The performance of the proposed control scheme is evaluated through simulations and animations.</P>
Plastic analysis of steel arches and framed structures with various cross sections
Jéssica L.Silva,Lidiane R.R.M. Deus,Ígor J.M. Lemes,Ricardo A.M. Silveira 국제구조공학회 2021 Steel and Composite Structures, An International J Vol.38 No.3
This paper presents a displacement-based numerical methodology following the Euler-Bernoulli theory to simulate the 2 nonlinear behavior of steel structures. It is worth emphasizing the adoption of co-rotational finite element formulations considering large displacements and rotations and an inelastic material behavior. The numerical procedures proposed considers plasticity concentrated at the finite elements nodes, and the simulation of the steel nonlinear behavior is approached via the Strain Compatibility Method (SCM), where the material constitutive relation is used explicitly. The SCM is also applied in determining the sections bearing capacity. Moreover, the present numerical approach is not limited to a specific structural member cross-sectional typology, with the residual stress models introduced explicitly in subareas of steel cross-sections generated by a 2D discretization. Finally, results consistent with the literature and with low processing time are presented.
Tap Changing Transformer based Dual Active Bridge Bi-Directional DC-DC Converter
Shiva S.M,Naga Brahmendra Yadav Gor,Pritam Das,Sanjib Kumar Panda 전력전자학회 2015 ICPE(ISPE)논문집 Vol.2015 No.6
Voltage fed Dual Active Bridge (VF-DAB) is the simplest isolated bidirectional DC-DC converter topology with least number of high frequency tank elements. This paper addresses the issue of Phase Shift operated VFDAB when used for energy storage applications due to their variable nature in terminal voltage based on the state of charge. Circulation currents and limitations in the soft-switching range are the main drawbacks of VF-DAB when operated with phase shift control within the two active bridges and widely varying voltage at one port. This affect their overall efficiencies at low and mid loads. In this paper, a modification in VF-DAB is proposed which reduces the drawbacks of the conventional phase shift controlled DAB by having variable transformer turns ratio, thereby improving the efficiency of the overall converter at medium and light loads. The analysis and design guidelines for the proposed converter are briefly explained and validated with experimental results.
Pedro H. A. Lima,Ígor J. M. Lemes,Rafael C. Barros,Ricardo A.M. Silveira 한국강구조학회 2023 International Journal of Steel Structures Vol.23 No.5
In the computational efficiency context, combining response precision and low execution time, methods that consider concentrated non-linear effects are interesting. The refined plastic hinge method (RPHM) considers the plasticity effects exclusively at the nodal points of the finite element mesh, however, it was developed for steel structures, with elastic-perfectly plastic behavior. In this methodology, rotational pseudo-springs in the finite elements ends are responsible to introduce the flexural stiffness degradation due to material non-linearity while the one-dimensional elements remain in the elastic state. The present work aims to study the inclusion of the flexural stiffness degradation of steel–concrete composite structural elements under monotonic loads, considering the cracking effects through the Branson equation, coupled to RPHM. For this, it is necessary to delimit the uncracked and cracked behavior of the cross-section. Thus, the strain compatibility method was used, in which, through the study of the cross-sectional behavior, interaction curves are obtained for the determination of elastic/elasto-plastic/plastic and uncracked/cracked states. Furthermore, this proposition is applied in a displacement-based formulation for the evaluation of the global behavior of steel–concrete composite elements. Comparisons are made between the results obtained here and those available in the literature, in the experimental and numerical contexts. These comparisons indicated for the validation of the numerical procedure proposed and implemented here, highlighting the precision of the formulation in both the pre- and post-critical structures behavior.
The Somatic Genomic Landscape of Chromophobe Renal Cell Carcinoma
The Cancer Genome Atlas Research Network,Davis, Caleb F.,Ricketts, C.J.,Wang, M.,Yang, L.,Cherniack, Andrew D.,Shen, H.,Buhay, C.,Kang, H.,Kim, S.,Fahey, Catherine C.,Hacker, Kathryn E.,Bhanot, G.,Gor Cell Press 2014 Cancer Cell Vol.26 No.3
We describe the landscape of somatic genomic alterations of 66 chromophobe renal cell carcinomas (ChRCCs) on the basis of multidimensional and comprehensive characterization, including mtDNA and whole-genome sequencing. The result is consistent that ChRCC originates from the distal nephron compared with other kidney cancers with more proximal origins. Combined mtDNA and gene expression analysis implicates changes in mitochondrial function as a component of the disease biology, while suggesting alternative roles for mtDNA mutations in cancers relying on oxidative phosphorylation. Genomic rearrangements lead to recurrent structural breakpoints within TERT promoter region, which correlates with highly elevated TERT expression and manifestation of kataegis, representing a mechanism of TERT upregulation in cancer distinct from previously observed amplifications and point mutations.