Underactuated Robots
(module 2 for Elective in Robotics in 2016/17)

Prof. Seth Hutchinson

Department of Electrical and Computer Engineering

University of Illinois


IMPORTANT: If you plan to attend this module please inform me at lanari@diag.uniroma1.it. This is essential for organization purposes.


Information                          temporary webpage (during the course this will be the webpage updated by Prof. Seth Hutchinson)

schedule 28 Nov - 21 Dec 2016

Mon
15:45-17:15 (in A7)
Wed
15:45-17:15 (in A7)
Fri   14:00-15:30 (in A7)

office hours
e-mail seth [at] illinois [dot] edu

Audience

This is one of the 4 modules of Elective in Robotics in 2016/2017, offered to students of the Master in Artificial Intelligence and Robotics (MARR) at Sapienza University of Rome.


Objective

The course presents the basic methods for analyzing and controlling underactuated mechanical systems.


Syllabus (preliminary)

In this class, we will consider the problems of motion planning and control of underactuated systems. Underactuated robots are those for which the number of actuators is strictly less than the number of degrees of freedom. Classical examples with a small number of degrees of freedom include robot arms that contain unactuated joints (e.g., the Acrobot or Pendubot), robot arms with flexible joints, the cart-pole system, and the Furuta pendulum. In addition to these basic systems, most all robots that are capable of locomotion are underactuated. This includes legged robots, flying robots, swimming robots, snake-like robots. For such robots, there is no actuator that can directly control the position and velocity of the center of mass. In the case of bipedal locomotion, the state of a humanoid's center of mass can only be controlled indirectly, using impact forces that occur at footfalls. For aerial vehicles such as quadrotors or fixed wing aircraft, the position of the center of mass is again indirectly controlled, in this case through the use of aerodynamic forces. This latter class of systems is typically far more complex than the classical examples.

The first part of the course will consider methods that decompose the system dynamics into actuated and unactuated components, and then apply methods from nonlinear and geometric control. Such methods include partial feedback linearization, energy-based methods (which often exploit passivity properties), backstepping, and geometric control techniques that exploit differential flatness.

The second part of the course will consider optimization-based methods. At their core, these algorithms rely on numerical optimization algorithms, and they are viable for systems with many degrees of freedom. These methods often exploit classical results from optimal control, including the Hamilton-Jacobi-Bellman equation and Pontryagin's maximum principle, along with methods from linear quadratic regulator theory for cases in which local linearization is feasible.

It is assumed that students taking this course will be familiar with classical algorithms for path planning (e.g., notions of configuration space, and sampling-based planning algorithms such as PRM and RRT), concepts of stability for nonlinear systems (mainly Lyapunov theory), and robot dynamics and control (including state-space control, feedback linearization).

Material



Grading       

After attending the course, students should either give a presentation on a certain topic (based on technical papers) or develop a small project (typically involving simulations). For more details, see the main page for
Elective in Robotics.


Master Theses at the Robotics Laboratory

Master Theses on the topics studied in this course are available at the Robotics Laboratory. More information can be found here.
Questions/comments: lanari [at] diag [dot] uniroma1 [dot] it