Alexander Leonessa

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Many aerospace engineers with an expertise in flight control system design, if tasked with designing a guidance system for an underwater vehicle, would dismiss the problem as easily solvable. To aerospace engineers, underwater vehicles are thought to be nothing more than powered blimps, which have been flying since 1852, when Henri Giffard built the first(More)
In this paper we develop a globally stabilizing stability-based switching controller for a three-state lumped parameter centrifugal compressor surge model. The proposed model involves pressure and mass flow compression system dynamics as well as spool dynamics to account for the influence of speed transients on the compression surge dynamics. The proposed(More)
A direct adaptive nonlinear tracking control framework for multivariable nonlinear uncertain systems with actuator amplitude and rate saturation constraints is developed. To guarantee asymptotic stability of the closed-loop tracking error dynamics in the face of amplitude and rate saturation constraints, the adaptive control signal to a given reference(More)
In this paper we develop globally stabilizing robust/disturbance rejection controllers for rotating stall and surge in axial flow compressors with uncertain system dynamics and exogenous disturbances. Specifically, using the nonlinearnonquadratic disturbance rejection optimal control framework for systems with bounded energy (square-integrable) L2(More)
In this paper, a nonlinear control-system design framework predicated on a hierarchical switching controller architecture parameterized over a set of moving system equilibria is developed. Specifically, using equilibria-dependent Lyapunov functions, a hierarchical nonlinear control strategy is developed that stabilizes a given nonlinear system by(More)
This paper presents a framework for dynamic humanoid locomotion on uneven terrain using a novel timevarying extension to the Divergent Component of Motion (DCM). By varying the natural frequency of the DCM, we are able to achieve generic CoM height trajectories during stepping. The proposed planning algorithm computes admissible DCM reference trajectories(More)
This paper presents a compliant locomotion framework for torque-controlled humanoids using model-based whole-body control. In order to stabilize the centroidal dynamics during locomotion, we compute linear momentum rate of change objectives using a novel time-varying controller for the Divergent Component of Motion (DCM). Task-space objectives, including(More)
This paper provides an overview of the embedded joint-space control approach developed for THOR, a new series elastic humanoid. The 60 kg robot features electromechanical linear series elastic actuators (SEAs), enabling low-impedance control of each joint in the lower body via linear to rotary and parallel mechanisms. We present a distributed joint(More)
In this paper we develop globally robustly stabilizing controllers for rotating stall and surge in multimode axial flow compressor models with uncertain pressure-flow compressor performance characteristic maps. Specifically, using Lyapunov stability theory, a novel switching nonlinear globally robustly stabilizing control law based on equilibria-dependent(More)
This paper presents an extension of previous model predictive control (MPC) schemes to the stabilization of the time-varying divergent component of motion (DCM). To address the control authority limitations caused by fixed footholds, the step positions and rotations are treated as control inputs, allowing the generation and execution of stable walking(More)