  In this paper, we will report our efforts in designing closed-loop feedback
for the thruster-assisted walking of bipedal robots. We will assume for
well-tuned supervisory controllers and will focus on fine-tuning the joints
desired trajectories to satisfy the performance being sought. In doing this, we
will devise an intermediary filter based on reference governors that guarantees
the satisfaction of performance-related constraints. Since these modifications
and impact events lead to deviations from the desired periodic orbits, we will
guarantee hybrid invariance in a robust way by applying predictive schemes
withing a very short time envelope during the gait cycle. To achieve the hybrid
invariance, we will leverage the unique features in our model, that is, the
thrusters. The merit of our approach is that unlike existing optimization-based
nonlinear control methods, satisfying performance-related constraints during
the single support phase does not rely on expensive numeric approaches. In
addition, the overall structure of the proposed thruster-assisted gait control
allows for exploiting performance and robustness enhancing capabilities during
specific parts of the gait cycle, which is unusual and not reported before.
