  This paper proposes an event-triggered sliding mode control (SMC) scheme
combined with a backstepping algorithm for control of 2-DOF humanoid's
lower-limb powered by Series elastic actuator (SEA). First, the modelling
process for the lower-limb system is implemented by using the Euler-Lagrange
theory. With the obtained dynamical equations of lower-limb, the model of the
SEA is achieved in both mechanical and electrical perspectives. Then, the
event-triggered SMC approach is utilized to ensure the system's stability and
eliminate the effect of bounded external disturbance. Next, some assumptions
and designed thresholds for the tracking error are given, together with the
proof for the convergence of the inter-event time. The backstepping algorithm
is applied in the end to determine the needed input control voltage signal.
Finally, the results of this research are demonstrated through some simulations
in order to prove the effi-ciency and appropriation of this method.
