< Online open course, MIT >
There is an interesting online open course made by Massachusetts Institute of Technology (MIT), with Prof. Russel Tedrake. This course treated the nonlinear dynamics, optimal control, motion planning and so on. The underactuation is a technical term used in robotics and control theory to describe mechanical devices that have a lower number of actuators than degrees of freedom. For example, the inverted pendulum is an underactuated system. There are some examples of underactuated mechanical system. As you know, inverted pendulum consists of two degrees of freedom. One is to support the motion in the horizontal plane, and the other is to angular motion of the pendulum. Though the system has two degrees of freedom, only one of them (the cart position) is actuated and the other is only indirectly controlled. There are also some other example such as passive walking and aerospace vehicles. I think understanding of underactuated robotics is necessary for someone who is interested in humanoid walking especially. If you are interest in this blog, just click the URL: http://ocw.mit.edu/courses/electrical-engineering-and-computer-science/6-832-underactuated-robotics-spring-2009/index.htm.