The sequential coupling between electrical and mechanical finite element physics domains for coupled Electromechanical analysis can be performed by the ANSYS Multi-field solver. The ANSYS Multi-field solver allows the most general treatment of individual physics domains. However, it cannot be applied to small signal modal and harmonic analyses because a total system eigen frequency analysis requires matrix coupling. Moreover, sequential coupling generally converges slower.

Strong Electromechanical coupling can be performed by the transducer element TRANS126, Gyimesi and Ostergaard([249]), Gyimesi and Ostergaard([331]), TRANS126 - Electromechanical Transducer.

TRANS126 completely models the fully coupled system, converting electrostatic energy into mechanical energy and vise versa as well as storing electrostatic energy. Coupling between electrostatic forces and mechanical forces is obtained from virtual work principles (Gyimesi and Ostergaard([249])).

TRANS126 takes on the form of a 2-node line element with electrical voltage and mechanical displacement DOFs as across variables and electric current and mechanical force as through variables. Input for the element consists of a capacitance-stroke relationship that can be derived from electrostatic field solutions and using the CMATRIX command macro (Gyimesi et al.([289]), Gyimesi and Ostergaard([290])).

The element can characterize up to three independent translation degrees of freedom at any point to simulate 3-D coupling. Thus, the electrostatic mesh is removed from the problem domain and replaced by a set of TRANS126 elements hooked to the mechanical and electrical model providing a reduced order modeling of a coupled electromechanical system (Gyimesi and Ostergaard ([287]), Gyimesi et al.([288])).

TRANS126 allows treatment of all kinds of analysis types, including prestressed modal and harmonic analyses. However, TRANS126 is limited geometrically to problems when the capacitance can be accurately described as a function of a single degree of freedom, usually the stroke of a comb drive. In a bending electrode problem, like an optical switch, obviously, a single TRANS126 element can not be applied. When the gap is small and fringing is not significant, the capacitance between deforming electrodes can be practically modeled reasonably well by several capacitors connected parallel. The EMTGEN (electromechanical transducer generator) command macro can be applied to this case.

Convergence issues may be experienced with TRANS126 when applied to the difficult hysteretic pull-in and release analysis (Avdeev et al.([332])) because of the negative total system stiffness matrix. The issue is resolved when the augmented stiffness method is applied.