This book described vibration reduction for flexible structures by the command smoothing techniques. The command smoothing technique is a kind of open-loop controller. The operator's commands filter through a piecewise continuous function, called smoother, to produce smoothed commands. Smoothed commands move flexible dynamic systems toward desired positions with minimal oscillations. Five types of command smoother were reported including one-piece, two-pieces, three-pieces, and four-pieces smoothers, and the smoother for multi-mode Duffing oscillators. All smoothers are robust to changes in the system parameters and working conditions. The command smoothing technique has been successfully applied to industrial cranes, sloshing suppression, flexible manipulators, high-speed cam and follower systems, and helicopter slung loads.