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Alexander Leonessa

15 accepted papers

2026

Safety-Critical and Distributed Nonlinear Predictive Controllers for Teams of Quadrupedal Robots

Basit Muhammad Imran, Jeeseop Kim, Taizoon Aliasgar Chunawala, Alexander Leonessa, Kaveh Akbari Hamed
ICRA 2026poster

This paper presents a novel hierarchical, safety-critical control framework that integrates distributed nonlinear model predictive controllers (DNMPCs) with control barrier functions (CBFs) to enable cooperative locomotion of multi-agent quadrupedal robots in complex environments. While NMPC-based m…

Cited by 0Source ↗PDF ↗Scholar ↗
2025

A Novel Telelocomotion Framework with CoM Estimation for Scalable Locomotion on Humanoid Robots

An-Chi He, Junheng Li, Jungsoo Park, Omar Kolt, Benjamin Beiter, Alexander Leonessa +2
ICRA 2025

Teleoperated humanoid robot systems have made substantial advancements in recent years, offering a physical avatar that harnesses human skills and decision-making while safeguarding users from hazardous environments. However, current telelocomotion interfaces often fail to accurately represent the r

Cited by 2Source ↗Scholar ↗
2025

Angular Divergent Component of Motion: A Step Towards Planning Spatial DCM Objectives for Legged Robots

Connor W. Herron, Robert Schuller, Benjamin C. Beiter, Robert J. Griffin, Alexander Leonessa, Johannes Englsberger
ICRA 2025

In this work, the Divergent Component of Motion (DCM) method is expanded to include angular coordinates for the first time. This work introduces the idea of spatial DCM, which adds an angular objective to the existing linear DCM theory. To incorporate the angular component into the framework, a disc

Cited by 1Source ↗Scholar ↗
2025

Safety-Critical and Distributed Nonlinear Predictive Controllers for Teams of Quadrupedal Robots

Basit Muhammad Imran, Jeeseop Kim, Taizoon Chunawala, Alexander Leonessa, Kaveh Akbari Hamed
RA-L 2025

This paper presents a novel hierarchical, safety-critical control framework that integrates distributed nonlinear model predictive controllers (DNMPCs) with control barrier functions (CBFs) to enable cooperative locomotion of multi-agent quadrupedal robots in complex environments. While NMPC-based m

Cited by 4Source ↗Scholar ↗
2024

Predictive Control With Indirect Adaptive Laws for Payload Transportation by Quadrupedal Robots

Leila Amanzadeh, Taizoon Chunawala, Randall T. Fawcett, Alexander Leonessa, Kaveh Akbari Hamed
RA-L 2024

This letter formally develops a novel hierarchical planning and control framework for robust payload transportation by quadrupedal robots, integrating a model predictive control (MPC) algorithm with a gradient-descent-based adaptive updating law. At the framework's high level, an indirect adaptive l

Cited by 13Source ↗Scholar ↗
2023

Real-Time Model-Free Deep Reinforcement Learning for Force Control of a Series Elastic Actuator

Ruturaj Sambhus, Aydin Gokce, Stephen Welch, Connor W. Herron, Alexander Leonessa
IROS 2023poster

Many state-of-the-art robotic applications utilize series elastic actuators (SEAs) with closed-loop force control to achieve complex tasks such as walking, lifting, and manipulation. Model-free PID control methods are more prone to instability due to nonlinearities in the SEA where cascaded model-ba…

Cited by 2Source ↗Scholar ↗
2020

Guaranteed Parameter Estimation of Hunt-Crossley Model with Chebyshev Polynomial Approximation for Teleoperation

Daniel Budolak, Alexander Leonessa
IROS 2020poster

In haptic time delayed teleoperation as the time delay from the communication channel increases, teleoperation system stability and performance degrade. To increase performance and provide better stability margins, various estimation methods and observers have been implemented in literature to more…

Cited by 3Source ↗Scholar ↗
2020

Hierarchical and Safe Motion Control for Cooperative Locomotion of Robotic Guide Dogs and Humans: A Hybrid Systems Approach

Kaveh Akbari Hamed, Vinay R. Kamidi, Wen-Loong Ma, Alexander Leonessa, Aaron D. Ames
RA-L 2020

This letter presents a hierarchical control strategy based on hybrid systems theory, nonlinear control, and safety-critical systems to enable cooperative locomotion of robotic guide dogs and visually impaired people. We address high-dimensional and complex hybrid dynamical models that represent coll

Cited by 35Source ↗Scholar ↗
2018

Straight-Leg Walking Through Underconstrained Whole-Body Control

Robert J. Griffin, Georg Wiedebach, Sylvain Bertrand, Alexander Leonessa, Jerry Pratt
ICRA 2018poster

We present an approach for achieving a natural, efficient gait on bipedal robots using straightened legs and toe-off. Our algorithm avoids complex height planning by allowing a whole-body controller to determine the straightest possible leg configuration at run-time. The controller solutions are bia…

Cited by 52Source ↗Scholar ↗
2017

Walking stabilization using step timing and location adjustment on the humanoid robot, Atlas

Robert J. Griffin, Georg Wiedebach, Sylvain Bertrand, Alexander Leonessa, Jerry Pratt
IROS 2017poster

While humans are highly capable of recovering from external disturbances and uncertainties that result in large tracking errors, humanoid robots have yet to reliably mimic this level of robustness. Essential to this is the ability to combine traditional “ankle strategy” balancing with step timing an…

Cited by 127Source ↗Scholar ↗
2016

Model predictive control for dynamic footstep adjustment using the divergent component of motion

Robert J. Griffin, Alexander Leonessa
ICRA 2016

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, al

Cited by 40Source ↗Scholar ↗
2015

Compliant locomotion using whole-body control and Divergent Component of Motion tracking

Michael A. Hopkins, Dennis W. Hong, Alexander Leonessa
ICRA 2015poster

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 Com…

Cited by 98Source ↗Scholar ↗
2015

Embedded joint-space control of a series elastic humanoid

Michael A. Hopkins, Stephen A. Ressler, Derek F. Lahr, Alexander Leonessa, Dennis W. Hong
IROS 2015poster

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 p…

Cited by 53Source ↗Scholar ↗
2015

Gait design and gain-scheduled balance controller of an under-actuated robotic platform

Jacob Webb, Alexander Leonessa, Dennis Hong
IROS 2015poster

This work presents a method for deriving a gain scheduled balance controller to stabilize the gate of a three legged under-actuated robotic platform called THALeR (Tri-Pedal Hyper Altitudinal Legged Robot). The scheduler adapts the controller gains in real time based upon the system's instantaneous…

Cited by 3Source ↗Scholar ↗