- Supression of the elastodynamic vibrations of a slider-crank mechanism with a very flexible connecting rod is addressed in this paper. A model for the mechanism is derived using Euler-Lagrange equations and the assumed modes method. The control action uses two feedback signals: the crank angle and the connecting rod coupler midpoint deflection. The actuator is located at the crank ground joint. This arrangement of actuators and sensors has been proven to be very effective. Two control schemes are proposed for the control of the flexible slider-crank mechanism. One scheme is a simple PD control scheme with feedback linearization. The second scheme is based on the -synthesis control technique. Both the -synthesis control scheme and the PD control scheme yielded good results. However, in terms of robustness, the results achieved via the -synthesis control design are better than those achieved with the PD control scheme.