Avshalom Sheffer
בס"ד
Avshalom Sheffer,
M.Sc. student,
School of Mechanical Engineering
Tel Aviv University
Works on developing of a method for finding the different singular configurations of several types of parallel mechanisms/robots using the dual 3D Kennedy method. The main topics of the dual 3D Kennedy method being used are: equimomental line/screw, Dual Kennedy theorem and circle, and various types of 3D Assur Graphs such as: triad (3/6 SP), tetrad, double triad and pentad.
I review mechanisms in terms of singularity that reported in the literature and new mechanisms that have not yet been reported. This method is consistent with other approaches that appear in the literature. It is important to note that 3/6 Stewart Platform is an Assur Graph of type 3D triad. It was proved that the singularity of AG has special properties and only AGs have the following property in the singular configuration: the system is both mobile (has an infinitesimal motion) and has a self-stress. This special singularity allows us to finding the singular configuration of the 6/6 Stewart Platform (3D Body-bar atom) through the properties of Assur Graph. For that reason, we use the self-stresses for characterizing the singularity configurations of the mechanisms. It seems that this method is applicable in finding the singularity of many other types of mechanisms and is not limited to a particular mechanism, such as: 3D Triad (3/6 SP), 3D Tetrad, 3D Double-Triad and 3D Pentad. In addition, the method is based on discrete mathematics thus can be computerized easily.
I and my supervisor, Prof. Offer Shai, believe that eqml/s is a fundamental concept in statics and have a significant potential in characterizing singularity of spatial parallel mechanisms. We continue to explore this topic and in the forthcoming paper we will present new singular conditions of complex mechanisms in three-dimensional. Future work will also include analytical techniques to complement the graphical techniques that are provided in our papers.
Contact Information:
E-mail: sheffer.am@gmail.com, sheffer@mail.tau.ac.il
M.Sc.Thesis:
A Dual 3D Kennedy Method For Characterizing Singular Configurations in Parallel Mechanisms
Publications:
Sheffer A. and Shai O., “Combinatorial Method for Characterization Singular Configurations in Parallel Mechanisms”, ASME Design Engineering Technical Conferences, August 2-5, Boston, Massachusetts, USA, 2015.
Slavutin M., Sheffer, A. and Shai, O., “A Geometric Singular Characterization Of The 6/6 Stewart Platform”, ASME Design Engineering Technical Conferences, August 21-24, Charlotte Convention Center, Charlotte, North Carolina, USA, 2016.
Slavutin, M., Shai, O., Sheffer, A., & Reich, Y., “A novel criterion for singularity analysis of parallel mechanisms”. Mechanism and Machine Theory, 137, 459-475, 2019.
Conferences:
“Combinatorial Method for Characterizing Singular Configurations in Parallel Mechanisms”, given at The 33rd Israeli Conference on Mechanical Engineering (ICME 2015).
“A geometric singular characterization of Parallel robots”, given at The Israeli Conference on Robotics (ICR 2016).