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Journal : METAL : Jurnal Sistem Mekanik dan Termal

pyScrew4Mobility: Modul Python untuk Penentuan Mobilitas Manipulator Paralel Berbasis Teori Screw Adriyan Adriyan
METAL: Jurnal Sistem Mekanik dan Termal Vol 4, No 1 (2020): Jurnal Sistem Mekanik dan Termal (METAL)
Publisher : Department of Mechanical Engineering, Universitas Andalas

Show Abstract | Download Original | Original Source | Check in Google Scholar | Full PDF (2481.711 KB) | DOI: 10.25077/metal.4.1.13-27.2020

Abstract

This paper addresses the mobility determination of parallel manipulators (PMs) using screw theory with algebra methods on an open-source computer algebra package: Sympy (symbolic python). The screw theory can specify the number and the type of motions owned by PMs with over-constrained or non-over constrained kinematic structures. The algebra methods are applied to obtain reciprocal of a screw or a screw system and basis of a screw system using null-spaces and the row/column-spaces technique, respectively. Hence, an object-oriented python module, called a pyScrew4Mobility module, is designed to realize such implementation. The module consists of three classes namely a Screw, a ScrewSystem and a ManipulatorMobility. A screw is constructed by the class of Screw, including its algebraic calculation such as negation, addition, multiplication, and product of two screws. Then, the ScrewSystem is used to construct a system of screws. It can be used to find reciprocal screws, unique screws within the system of screws, and calculate the products of two systems of screws. The last class or ManipulatorMobility has a direct implementation to determine the mobility of PMs. It uses information from the list of unit screw direction, position, and pitch. Finally, the designed screw module is tested to demonstrate its capability to determine the mobility of four well-known PMs, i.e. 3-PRRR; 3-PR(Pa)R; 4-PRRU; and 6-UPS, including the respective time spent for calculation.
Sintesis Dimensi Manipulator Paralel Bidang Dua Derajat Kebebasan Dengan Rantai Kinematik Paralelogram Simetris Adriyan Adriyan
METAL: Jurnal Sistem Mekanik dan Termal Vol 5, No 2 (2021): Jurnal Sistem Mekanik dan Termal (METAL)
Publisher : Department of Mechanical Engineering, Universitas Andalas

Show Abstract | Download Original | Original Source | Check in Google Scholar | Full PDF (8250.373 KB) | DOI: 10.25077/metal.5.2.72-85.2021

Abstract

The paper discussed the process to find the optimum dimension for the kinematic constants of a two-degree of freedom planar parallel manipulator. This manipulator itself was constructed by symmetric three parallelogram chains. An optimization process using non-sorted dominated genetic algorithm II (NSGA-II) was carried out for maximization of (i) rMIC (the radius of the maximum inscribed circle) and GCI (global conditioning index), and (ii) rMIC and GTI (global transmission index). Here, GCI and GTI were evaluated on the useful workspace. Instead of using atlases of performance indices, a grid search evaluation was applied to obtain a region in PDS near the optimum values for both maximization cases. This region gave a small bound for NSGA-II to start searching the optimum values of the kinematic constants. For simplification, a python framework for the multi-objective optimization called pymoo was applied to solve the optimization problem. Henceforth, the maximization for two cases yielded an insignificant difference of results in terms of optimum kinematic constants, rMIC, GCI, GTI, area of useful workspace, area of good condition workspace (GCW), area of good transmission workspace (GTW), and the area ratio of GCW and GTW to the useful workspace.