Acrobot and Reaction Wheel Pendulum
The acrobot is also a double pendulum, but the motor actuates now the second link and moves if the pendulum moves. When linear control theory is considered, similar methods as for the usual double pendulum can be applied. This type of pendulum has been intensively used to study methods of nonlinear control with the goal to swing the pendulum up (see the papers of M. Spong and others).
The reaction wheel pendulum
A special case of the acrobot appears if the center of gravity of link 2 coincides with the revolution point of link two. This kind of pendulum is slightly easier to control and known as reaction wheel pendulum. PendCon offers this experiment also in the Basic series, but there only linear controllers are possible. With the PendCon Advanced set-up it is no problem to implement a nonlinear controller.