Impact of Mechanical Reliability and Production Cost on the Thumb’s Four Crossed Bar Mechanisms

Nestor Tsamo, Denis Tcheukam Toko, Pierre Kisito Talla

design criteria, mechanical reliability, multiobjective optimization, thumb mechanism

The thumb mechanism of a cybernetic human hand prosthesis is modeled with a one degree of freedom four crossed bar mechanism .The optimization process is carried out with respect to five design criteria which are: structural error due to the bending angle of the second phalanx , mechanical error due to the dimensional tolerances and the clearances at the articulations, Maximum driving torque to counter balance the forces applied at the tip of the thumb’s mechanism, strength mechanical reliability of the whole mechanism and production cost of the mechanism. The individual optimization process, gives at each stage, a singular design variable from one design criterion to another. Meanwhile, the introduction of the global production cost to the multiobjective optimization of four criteria and of the five criteria respectively generate the same optimum variables obtained when minimizing simultaneously the four first criteria. Therefore, the mechanical reliability and the production cost of the whole mechanism has a significant effect on the whole process of the mechanism optimization due to the stochastic nature of the trajectory of the cutting tools during the entire manufacturing process.

https://dx.doi.org/10.31873/IJEAS.7.05.19