Coarse-to-Fine Tracking of Articulated Objects Using a Hierarchical Spring System

AbstractForty years ago the notion of configuration space (C-space) revolutionised robot motion planning for rigid and articulated objects. Despite great progress, handling deformable materials has remained elusive because of their infinite-dimensional shape-state space. Finding low-complexity representations has become a pressing research goal. This work tries to make a tiny step in this direction by proposing a state representation for textiles relying on the C-space of some distinctive points. A stratification of the configuration space for n points in the cloth is derived from that of the flag manifold, and topological techniques to determine adjacencies in manipulation-centred state graphs are developed. Their algorithmic implementation permits obtaining cloth state–space representations of different granularities and tailored to particular purposes. An example of their usage to distinguish between cloth states having different manipulation affordances is provided. Suggestions on how the proposed state graphs can serve as a common ground to link the perception, planning and manipulation of textiles are also made.

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A novel tuned mass-conical spring system for passive vibration control of a variable mass structure

Journal of Vibration and Control ◽

10.1177/10775463211000497 ◽

2021 ◽

pp. 107754632110004

Author(s):

Sanjukta Chakraborty ◽

Aparna (Dey) Ghosh ◽

Samit Ray-Chaudhuri

Keyword(s):

Variable Mass ◽

Design Procedure ◽

Time History ◽

Tuned Mass Damper ◽

Water Tank ◽

Mass System ◽

Mass Damper ◽

Linear Spring ◽

Spring System ◽

Elevated Water

This article presents the design of a tuned mass damper with a conical spring to enable tuning to the natural frequency of the system at multiple values, as may be convenient in case of a system with fluctuations in the mass. The principle and design procedure of the conical spring in the context of a varying mass system are presented. A passive feedback control mechanism based on a simple pulley-mass system is devised to cater to the multi-tuning requirements. A design example of an elevated water tank with fluctuating water content, subjected to ground excitation, is considered to numerically illustrate the efficiency of such a tuned mass damper associated with the conical spring. The conical spring is designed based on the tuning requirements at different mass conditions of the elevated water tank by satisfying the allowable load bearing capacity of the spring. Comparisons are made with the conventional passive tuned mass damper with a linear spring tuned to the full tank condition. Results from time history analysis reveal that the conical spring-tuned mass damper can be successfully designed to remain tuned and thereby achieve significant response reductions under stiffening conditions of the primary structure, whereas the linear spring-tuned mass damper suffers performance degradation because of detuning, whenever there is any fluctuation in the system mass.

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Annotation scaffolds for manipulating articulated objects

Autonomous Robots ◽

10.1007/s10514-021-09983-8 ◽

2021 ◽

Author(s):

Pablo Frank-Bolton ◽

Roxana Leontie ◽

Evan Drumwright ◽

Rahul Simha

Keyword(s):

Articulated Objects

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A Two-Step Ship Target Detection Method in High-Resolution Sar Image Based on Coarse-to-Fine Mechanism

IGARSS 2020 - 2020 IEEE International Geoscience and Remote Sensing Symposium ◽

10.1109/igarss39084.2020.9323895 ◽

2020 ◽

Author(s):

Kun Sun ◽

Yuanyuan Li ◽

Cong Li ◽

Yi Liang ◽

Mengdao Xing

Keyword(s):

High Resolution ◽

Target Detection ◽

Detection Method ◽

Sar Image ◽

Coarse To Fine

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Study on dynamic characteristics of leaf spring system in vibration screen

Journal of Low Frequency Noise Vibration and Active Control ◽

10.1177/14613484211022974 ◽

2021 ◽

pp. 146134842110229

Author(s):

Jiacheng Zhou ◽

Chao Hu ◽

Ziqiu Wang ◽

Zhengfa Ren ◽

Xiaoyu Wang ◽

...

Keyword(s):

Dynamic Characteristics ◽

Vertical Direction ◽

Maximum Amplitude ◽

Exciting Force ◽

Mode Shapes ◽

Leaf Spring ◽

Amplification Factors ◽

Simulation And Experiment ◽

Exciting Forces ◽

Spring System

By studying dynamic characteristics of the leaf spring system, a new elastic component is designed to reduce the working load and to a certain extent to ensure the linearity as well as increase the amplitude in the vertical and horizontal directions in vibration screen. The modal parameters, amplitudes, and amplification factors of the leaf spring system are studied by simulation and experiment. The modal results show that the leaf spring system vibrates in horizontal and vertical directions in first and second mode shapes, respectively. It is conducive to loosening and moving the particles on the vibration screen. In addition, it is found that the maximum amplitude and amplification factor in the horizontal direction appear at 300 r/min (5 Hz) while those in the vertical direction appear at 480 r/min (8 Hz), which are higher than those in the disc spring system. Moreover, the amplitude of the leaf spring system increases proportionally with the increase of exciting force while the amplification factors are basically the same under different exciting forces, indicating the good linearity of the leaf spring system. Furthermore, the minimum exciting force occurs in the leaf spring system under the same amplitude by comparing the exciting force among different elastic components. The above works can provide guidance for the industrial production in vibration screen.

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