Alireza Ramezani

306 Talbot Lab.,
104 S Wright St.,
Urbana, IL 61801-2957
tel 734-604-1214


My research examines underactuated and highly dynamic robotic systems with non-trivial morphologies, which in general are unstable and depend on fast-loop controllers. Examples of these systems include fast and completely flat micro flying wings that has no vertical control surface, a soft robot such as a bat-inspired micro aerial vehicle that can dance in the air with great composure, a multi-agent flying machine with a decentralized control policy, an omnidirectional robot that is dynamically balanced on a spherical wheel, and a fast walking or running multi-link bipedal robot with human morphology. All these examples demand complex controllers. These examples embody nonlinear dynamics with affine-in-control and nonaffince-in-control representations. For instance, a flying bat-inspired robot with elastic control surfaces, such as armwing and tail membranes, evolves in its configuration space through the action of aerodynamic forces, nonaffine-in-control, whereas the hybrid nonlinear dynamics of a walking bipedal robot evolves through the direct action of the torque commands at the joints, affine-in-control.

I employ advanced theories of nonlinear control and geometric mathematics to design controllers for these sys- tems. My works exist at the intersection of theory of non- linear control and robotics, intersection of theory and experiment. Despite the common belief that demonstrating the effectiveness of nonlinear control theory is impossible because it is too complex, I believe the development of robotic platforms that utilizes these tool is not beyond our reach. And, in my works it is tried to highlight this belief. Significant achievements have been made in recent years in developing small and economically affordable electronics such as high power density actuators, robust sensors and fast processing chips. At the same time, the emergence of new manufacturing approaches, such as 3D printing technology (metal and plastic), has made available easyto- develop prototypes. I use this chance to develop robots that help us understand intricate concepts of nonlinear dynamics. For instance, perhaps, a physical platform such as an omnidirectional balancing robot that reflects the sophistication of the nonholonomic dynamic constraints and forces, is the missing entity in the works that are trying to understand such mechanisms by solely relying on mathematical models. Previously, developing such a robotic system was challenging not only because of hardware development burdens but also because of the lack of controllers to steer these systems. Developing these controllers has been challenging because of the pace of technological advancements. Therefore, the three aspects of theoretical developments, hardware developments, and applying theory to hardware has restricted the presence of these powerful mathematical tools, nonlinear controllers, in real life applications. My research attempts to address such restriction by designing and developing robots with nontrivial morphologies, all while apply theories of nonlinear control to steer these systems.

B2: photo courtesy of Soon-Jo Chung, University of Illinois

B2: photo courtesy of Seth Hutchinson & Soon-Jo Chung, University of Illinois.

Current Research

(1, 2, 4, 7, 8, 10, 11, 16)

My post-doctoral work involves dynamic modeling, controller designing, developing the hardware and electronic of a flying robot with bat morphology. Bats have the most sophisticated morphology of flying mammals; they have several types of joints that interlock bones and muscles to one another and create a metamorphic musculoskeletal system with over 40 Degrees of Freedom (DoF). I believe that the current methods of studying bat flight are limited to conventional off- board motion capture systems, which cannot explain the numerous flight control strategies that bats employ. My recent research adds to efforts in studying bats’ array of physiological and flight specializations by designing a bat-inspired robot called Bat Bot, or B2 for short. B2 can reveal information about the biological aerial locomotion of bats with nontrivial morphologies. I employed the platform to answer scientific questions about how bats use their forelimbs and hindlimbs to control flight. Based on my observations about B2’s performance, I found that: 1) hindlimbs might be actively employed by biological bats to modulate the pitch angle of each wing and help stabilize longitudinal dynamics; 2) Flexion-extension at the elbow, abduction-adduction of the fingers, and rotation of the arm all in unison could enhance flight capabilities by compensating for roll perturbations through the regulation of wing loading. In developing the morphing skeleton of B2, I considered two major properties of biological bat wings: articulation and elasticity. First, the dominant DoFs in bat flight mechanism were selected. These DoFs were incorporated in the design of B2 by means of a series of mechanical constraints. Then, I deployed an ultra-thin (56 micron), extremely stretchable, silicone-based membrane, which was designed to resemble the continuous surface and elastic properties of the bat skin under wing morphing, onto the skeleton of the morphing wing. Finally, I designed and enforced a series of virtual constraints to synthesize the morphing behavior of the robot. Stable aerial locomotion was achieved by employing an event-based flight control scheme that interpreted the virtual constraints of the dynamic system as control inputs to the morphing soft robot.

Courtesy of ARCL, Univeristy of Illinois

Courtesy of Verge

Ph. D. Work

(5, 6, 12, 13, 14)

ATRIAS: photo courtesy of Jessy Grizzle, University of Michigan.

ATRIAS: photo courtesy of Jessy Grizzle, University of Michigan.

Ph.D Research: my doctoral work contributed to the walking control design for bipedal robots with nontrivial morphologies. I developed nonlinear feedback controllers for walking robots in 3D on level ground with energy efficiency as the performance objective. Assume The Robot Is A Sphere (ATRIAS) is a new robot that has been designed for the study of 3D bipedal locomotion, with the aim of combining energy efficiency, speed, and robustness with respect to natural terrain variations in a single platform. The robot is highly underactuated. Its sagittal plane dynamics are designed to embody the spring loaded inverted pendulum (SLIP), which has been shown to provide a dynamic model of the body center of mass during steady running gaits of a wide diversity of terrestrial animals. I developed a detailed nonlinear dynamic model and used it to optimize walking gaits with respect to the cost of mechanical transport, a dimensionless measure of energetic efficiency. A nonlinear feedback controller was designed that stabilizes the 3D walking gaits, despite the high degree of underactuation of the robot.

Prior Works


My first experience at the Nanogram micro-robotic competition at the Swiss Federal Institute of Technology (ETH Zurich) included fabricating and designing controllers for wireless resonant magnetic propelled mobile micro robotic agents, which were called MagMite. Later, my ETH-Diploma work at the Institute for Dynamic Systems and Control at ETH Zurich examined distributed embedded systems in order to design a decentralized flight control policy for a multi-agent flying robot, which was called Distributed Flight Array.

DFA: photo courtesy of Raffaelo D'Andrea, ETH Zurich.

DFA: photo courtesy of Raffaelo D’Andrea, ETH Zurich.

This platform is a state-of-the-art flying robot which consists of modules, each of which is equipped with a set of wheels that enable it to drive on the ground, and a fixed-pitch propeller that can generate enough thrust to lift itself into the air but is

unstable in flight. Not until these modules are joined do these relatively simple devices evolve into a sophisticated multi-rotor system capable of coordinated flight. During my Diploma work, I demonstrated the first autonomous flight of the Distributed Flight Array utilizing a decentralized embedded flight policy.

Courtesy of Rafaello D’Andrea


  • Soft Articulated Micro Aerial Vehicles: although the demand for fast and cheap package delivery increases in our modern cities, conventional drone technology has remained limited in that it cannot be employed in environments where safety matters, such as in crowds. I believe the journey that I have started in designing and developing articulated soft flying robots will eventually fulfill these restrictions. Morphing wing flight can yield extreme agile flight maneuvers, which are the most prized features when crowded environments are involved during the process of delivery.
  • Legged Robotics: Existing bipedal robots are made out of hard metals and powered by actuating mechanisms that are not safe for operation in proximity to humans. This is a major setback and the solution to this exists in utilizing new soft materials, e.g., soft 3D-printer resins. It is my long term goal to bring the luxury of legged locomotion to our society in the form of autonomous machines that possess human morphology and can operate safely around humans.
  • Multiagent Robotic Performance: We all know that success lies in collaboration with others. What if the collaborators are several autonomous robotic agents? These agents can do very simple tasks. Once they are docked, they can form a nontrivial morphology and demonstrate very sophisticated behavior, e.g., an articulated manipulator to pick and place items.


[1] Alireza Ramezani, Xichen Shi, Soon-Jo Chung, Seth Hutchinson, Bat Bot (B2), A Biologically Inspired Flying Machine, IEEE Transactions on Robotics, in preparation.

[2] Alireza Ramezani, Xichen Shi, Jonathan Edward Hoff, Soon-Jo Chung, Seth Hutchinson, Robot Assisted Study of Bat Flight, Science, submitted.

[3] Jonathan Edward Hoff,Alireza Ramezani, Soon-Jo Chung, Seth Hutchinson, Synergistic Design of a Bio-Inspired Micro Aerial Vehicle with Articulated Wings, Robotics Science and Systems Conference (RSS), Ann Arbor, Michigan, USA., June 20-22, 2016.

[4] Alireza Ramezani, Xichen Shi, Soon-Jo Chung, Seth Hutchinson, Bat Bot (B2), A Biologically Inspired Flying Machine, IEEE International Conference on Robotics and Automation (ICRA), Stockholm, Sweeden, May 16-21, 2016.

[5] Alireza Ramezani, Jonathan Hurst, Kaveh Akbari Hamed and J.W. Grizzle, Performance Analysis and Feedback Control of ATRIAS, A 3D Bipedal Robot, ASME Journal of Dynamic Systems Measurement and Control,Volume 136, Issue 2, Start Page 21012, March 2014.

[6] Hae-Won Park, Alireza Ramezani, and JessyW. Grizzle, A Finite-state Machine for Accommodating Unexpected Large Ground Height Variations in Bipedal RobotWalking, IEEE Transactions on Robotics, Volume 29, Issue 2, Pages 331-345, April 2013.

[7] Alireza Ramezani, Soon-Jo Chung, Seth Hutchinson, Lagrangian Modeling and Flight Control of Articulated-Winged Bat Robot, Proc. 2015 IEEE/RSJ International Conference on Intelligent Robots and Systems (IROS), Hamburg, Germany, September 28 – October 02, 2015.

[8] Alireza Ramezani, Xichen Shi, Soon-Jo Chung, Seth Hutchinson, Nonlinear Flight Controller Synthesis of a Bat-Inspired Micro Aerial Vehicle, AIAA Guidance, Navigation, and Control Conference, San Diego, CA, 4-8 Jan 2016, AIAA 2016-1376.

[9] Brian G. Buss, Alireza Ramezani, Kaveh Akbari Hamed, Brent A. Griffin, Kevin S. Galloway, Jessy W. Grizzle, Preliminary Walking Experiments with Underactuated 3D Bipedal Robot MARLO, IEEE/RSJ International Conference on Intelligent Robots and Systems (IROS), Chicago, IL, September 2014.

[10] Sayed Usman Ahmed,Alireza Ramezani, Soon-Jo Chung, Seth Hutchinson, Biologically Inspired Attitude Control of A Micro Aerial Vehicle, IEEE International Conference on Robotics and Automation (ICRA), Marina Bay Sands, Singapore, May 29, 2017, in preparation.

[11] Jonathan Edward Hoff,Alireza Ramezani, Soon-Jo Chung, Seth Hutchinson, Synergistic Design of a Bio-Inspired Micro Aerial Vehicle with Articulated Wings, IEEE Transactions on Robotics, in preparation.

[12] J.W. Grizzle, Alireza Ramezani, B. Buss, B.Griffin, K. Akbari Hamed, and K. S.Galloway, Progress on Controlling MARLO, an ATRIAS-series 3D Underactuated Bipedal Robot, Dynamic Walking Conference, Robotic Institute Carnegie Mellon University, Pittsburgh, June 2013.

[13] Alireza Ramezani, J.W. Grizzle, A Feedback Control of ATRIAS, A 3D Bipedal Robot, 15th International Conference on Climbing and Walking Robots and the Support Technologies for Mobile Machines, Volume 23, Pages 26, July 2012.

[14] Hae-Won Park, Koushil Sreenath, Alireza Ramezani, and J. W. Grizzle, Switching Control Design for Accommodating Large Step-down Disturbances in Bipedal Robot Walking, International Conference on Robotics and Automation (ICRA), Pages 45-50, May 2012.

[15] Raymond Oung, Alireza Ramezani, Raffaello D Andrea, Feasibility of a Distributed Flight Array, In Proceedings of the 48th IEEE Conference on Decision and Control (CDC) held jointly with the 28th Chinese Control Conference (CCC), Shanghai, China, Pages 3038-3044, December 2009.

[16] Alireza Ramezani, Xichen Shi, Soon-Jo Chung, Seth Hutchinson, Bat Bot (B2), an Articulated Winged Bat Robot, International Conference on Robotics and Automation (ICRA), Late Breaking Results Poster Session, Seattle, USA, May, 2015.