The flexible wearable chair is like a light weight mobile exoskeleton that allows people to sit anywhere in any working position. The traditional chair is difficult to move to different working locations due to its large size, heavy weight (~5 -7 kg) and rigid structure and thus, they are inappropriate for workplaces where enough space is not available. Flexible wearable chair has a gross weight of 3 kg as it utilizes light-weight aluminium alloy members. Unlike the traditional chair, it consists of kinematic pairs which enable taking halts between continuous movements at any working position and thus, it is capable of reducing the risk of the physical musculoskeletal disorder substantially among workers. The objective of this paper is to focus on the mechanical design and finite element analysis (FEA) of the mechanism using ANSYS ® software. In the present work, all the parts of the mechanism are designed under static load condition. The results of the analysis indicate that flexible wearable chair satisfies equilibrium and stability criterion and is capable of reducing fatigue during working in an assembly line/factory.
Volumetric locking is exhibited by nearly incompressible solids such as rubber, resulting in over-stiffening response of the finite element mesh. In this work, we developed the displacement-based computationally efficient volumetric locking-free 3D finite element using smoothening of determinant of deformation gradient (J-Bar method) within the framework of isotropic hyperelasticity. The developed methodology is employed to analyse a rubber block undergoing finite stretch and bending deformations. The convergence study for finite stretch and bending of rubber block is presented. Results of the analysis show that J-Bar method efficiently removes the volumetric locking.
Optimal control theory allows finding the optimal input of a mechanical system modelled as a initial value problem. The resulting minimisation problem may be solved with known direct and indirect methods. We here propose time discretisations for both methods, direct midpoint (DMP) and indirect midpoint (IMP) algorithms, which despite their similarities result in different convergence orders for the adjoint (or co-state) variables. We additionally propose a third time-integration scheme, Indirect Hamiltonian Preserving (IHP) algorithm, which preserves the control Hamiltonian, an integral of the analytical Euler-Lagrange equations of the optimal control problem.We test the resulting algorithms to linear and non-linear problems with and without dissipative forces: a propelled falling mass subjected to gravity and a drag force, an elastic inverted pendulum, and the locomotion of a worm-like organism on a frictional substrate. In order to improve the convergence of the solution process of the discretised equations in non-linear problems, we also propose a computational simple suboptimal initial guess, and apply a forwardbackward sweep method, which computes each set of variables (state, adjoint and control) in a staggered manner. We demonstrate in our examples their practical advantage for computing optimal solutions.
Volumetric locking is exhibited by nearly incompressible solids such as rubber, resulting in over-stiffening response of the finite element mesh. In this work, we developed the displacement-based computationally efficient volumetric locking-free 3D finite element using smoothening of determinant of deformation gradient (J-Bar method) within the framework of isotropic hyperelasticity. The developed methodology is employed to analyse a rubber block undergoing finite stretch and bending deformations. The convergence study for finite stretch and bending of rubber block is presented. Results of the analysis show that J-Bar method efficiently removes the volumetric locking.
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