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Optimal controller applied to robotic systems using covariant control equations
Published in International Journal of Control, 2022
Juan Antonio Rojas-Quintero, Juan Antonio Rojas-Estrada, Jorge Villalobos-Chin, Victor Santibañez, Eusebio Bugarin
As noticed by Gregorio Ricci-Curbastro, the formulae (3) and (4), allowing the calculations of the Christoffel symbols of the first and second kind, can be geometrised by vanishing the covariant derivative of the mass tensor (Bianchi, 1902; Grinfeld, 2013; Levi-Cività & Persico, 1925; Lovelock & Rund, 1975; Ricci-Curbastro & Levi-Cività, 1900). Therefore
The same property holds for the inverse mass tensor, and
Formulation of 3D finite elements using curvilinear coordinates
Published in Mechanics of Advanced Materials and Structures, 2022
Maria Cinefra
This quantity represents the Christoffel three-index symbol of the second kind. The Christoffel symbols are a measure of the curvature of the curvilinear coordinate axes, and play an important role in tensor calculus. From Eqs. (6) and (8), we obtain the derivative of the contravariant base vector with respect to as follows: