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You searched for subject:(Stiffness Map). Showing records 1 – 2 of 2 total matches.

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Queens University

1. Moradi, Amir. Stiffness Analysis of Cable-Driven Parallel Robots .

Degree: Mechanical and Materials Engineering, 2013, Queens University

The aim of this thesis is the stiffness analysis of cable-driven parallel robots. Cable-driven parallel robots have drawn considerable attention because of their unique abilities and advantages such as the large workspace, light weight of cable actuators, easy disassembly and transportation of the robot. The mobile platform of a cable-driven parallel robot is attached to the base with multiple cables. One of the parameters that should be studied to make sure a robot is able to execute a task accurately is stiffness of the robot. In order to investigate the stiffness behaviour of a robot, the stiffness matrix can be calculated as the first step. Because cables act in tension, keeping the positive tension in cables becomes a challenge. In order to have a fully controllable robot, an actuation redundancy is needed. These complexities are addressed in the thesis and simulations. In this thesis, the complete form of the stiffness matrix is considered without neglecting any terms in calculation of the stiffness. Some stiffness indices such as single-dimensional stiffness based on stiffness ellipse, directional stiffness and condition number of the stiffness matrix are introduced and calculated and stiffness maps of the robot are developed. In addition, the issue of unit inconsistency in calculating the stiffness index is addressed. One of the areas which is also addressed in this thesis is failure analysis based on the stiffness of robot. The effect of the failure in one or more cables or motors is modelled and stiffness maps are developed for the failure situation. It is shown that by changing the anchor position and mobile platform orientation, the lost stiffness after failure of a cable or motor can be retrieved partially. Optimum anchor position and mobile platform orientation are identified to maximize the area of the stiffness map. Condition number of the stiffness matrix while robot is following a trajectory is optimized. In addition, when one cable fails during the path planning, the recovery of the robot is studied. Finally, these analyses on stiffness and failure provide the designer with the necessary and valuable information about the anchor positions and actuator toques.

Subjects/Keywords: Cable-driven parallel robot; Failure analysis; Stiffness map; Stiffness analysis

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6th Edition):

Moradi, A. (2013). Stiffness Analysis of Cable-Driven Parallel Robots . (Thesis). Queens University. Retrieved from http://hdl.handle.net/1974/7965

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Chicago Manual of Style (16th Edition):

Moradi, Amir. “Stiffness Analysis of Cable-Driven Parallel Robots .” 2013. Thesis, Queens University. Accessed October 22, 2019. http://hdl.handle.net/1974/7965.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

MLA Handbook (7th Edition):

Moradi, Amir. “Stiffness Analysis of Cable-Driven Parallel Robots .” 2013. Web. 22 Oct 2019.

Vancouver:

Moradi A. Stiffness Analysis of Cable-Driven Parallel Robots . [Internet] [Thesis]. Queens University; 2013. [cited 2019 Oct 22]. Available from: http://hdl.handle.net/1974/7965.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Council of Science Editors:

Moradi A. Stiffness Analysis of Cable-Driven Parallel Robots . [Thesis]. Queens University; 2013. Available from: http://hdl.handle.net/1974/7965

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation


University of Illinois – Chicago

2. Yasar, Temel K. Optimal Pulse Sequences for Magnetic Resonance Elastography.

Degree: 2014, University of Illinois – Chicago

Magnetic Resonance Elastography (MRE) is a non-invasive phase contrast MR imaging method that captures the three-dimensional harmonic wave propagation introduced into subject by external actuators. This wave propagation vector field is processed into stiffness maps of various kinds that are used to assess the pathological changes that cannot be detected otherwise with non-invasive imaging methods. As in all other MR imaging methods, long acquisition duration is one of the important limiting factors for MRE. There are different approaches to reduce the scan time, such as as reduced motion encoding MRE or fractional multi-frequency MRE; however, these methods are all at the cost of the reduced signal to noise ratio (SNR) or reduced phase to noise ratio (PNR). Recently we have introduced two accelerated MRE methods, which do not compromise SNR or PNR while reducing the acquisition time by a factor of three compared to the conventional MRE methods. The first one is Selective Spectral Displacement Projection (SDP) MRE method that can encode a mechanical motion of multiple frequency components at once. The second one is SampLe Interval Modulation (SLIM) MRE which can encode the mono-frequency motion in multiple directions concurrently. In this dissertation, I propose a final optimal method that integrates the technique developed in SLIM MRE into SDP MRE, namely Unified sampLing Time Interval ModulATion (ULTIMATe) MRE. This method is the optimal MRE method in the sense that it can reach the limit of time efficiency without sacrificing SNR and PNR. A new mathematical framework was introduced to accommodate all three methods while preventing any ambiguity which might otherwise can occur with the existing MRE notation. Advisors/Committee Members: Royston, Thomas J (advisor).

Subjects/Keywords: Magnetic Resonance Elastography; Shear Modulus Estimation; MRE; Optimal Pulse Sequence; SDP; SLIM; Multi-Frequency MRE; Multi-Direction MRE; Stiffness Map; Wave Image; three-dimensional acoustic wave acquisition

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6th Edition):

Yasar, T. K. (2014). Optimal Pulse Sequences for Magnetic Resonance Elastography. (Thesis). University of Illinois – Chicago. Retrieved from http://hdl.handle.net/10027/18967

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Chicago Manual of Style (16th Edition):

Yasar, Temel K. “Optimal Pulse Sequences for Magnetic Resonance Elastography.” 2014. Thesis, University of Illinois – Chicago. Accessed October 22, 2019. http://hdl.handle.net/10027/18967.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

MLA Handbook (7th Edition):

Yasar, Temel K. “Optimal Pulse Sequences for Magnetic Resonance Elastography.” 2014. Web. 22 Oct 2019.

Vancouver:

Yasar TK. Optimal Pulse Sequences for Magnetic Resonance Elastography. [Internet] [Thesis]. University of Illinois – Chicago; 2014. [cited 2019 Oct 22]. Available from: http://hdl.handle.net/10027/18967.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Council of Science Editors:

Yasar TK. Optimal Pulse Sequences for Magnetic Resonance Elastography. [Thesis]. University of Illinois – Chicago; 2014. Available from: http://hdl.handle.net/10027/18967

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

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