  Purcell's planar three-link microswimmer is a classic model of swimming in
low-Reynolds-number fluid, inspired by motion of flagellated microorganisms.
Many works analyzed this model, assuming that the two joint angles are directly
prescribed in phase-shifted periodic inputs. In this work, we study a more
realistic scenario by considering an extension of this model which accounts for
joints' elasticity and mechanical actuation of periodic torques, so that the
joint angles are dynamically evolving. Numerical analysis of the swimmer's
dynamics reveals multiplicity of periodic solutions, depending on parameters of
the inputs - frequency and amplitude of excitation, joints' stiffness ratio, as
well as joint's activation. We numerically study swimming direction reversal,
as well as bifurcations, stability transitions, and symmetry breaking of the
periodic solutions, which represent the effect of buckling instability observed
in swimming microorganisms. The results demonstrate that this variant of
Purcell's simple model displays rich nonlinear dynamic behavior with
actuated-elastic joints. Similar results are also obtained when studying an
extended model of a six-link microswimmer.
