Ultrasonically Assisted Machining (UAM) is an emerging technology that has proven to be very efficient in improving the surface finishing in material machining such as turning, milling, and drilling. Smart material actuators are used in such applications to vibrate the cutting tip while machining, hence, improving the manipulated surface. In order to achieve that, it is required to vibrate the cutting tip at certain frequency with certain amplitude. In fact, controlling the amplitude of these smart actuators is a tedious and difficult task due to the inherent nonlinearities associated with smart materials. In this paper, two control algorithms are proposed; sliding mode controller with high frequency (SMHF) and proportional-integral controller with RMS (PIRMS). Numerical simulations are presented to demonstrate the effectiveness of using the proposed controller. The PIRMS algorithm demonstrates a better performance when compared with the SMHF algorithm.