Ultra-precision machining to sub-micrometer depths is shown to be a threshold area of work requiring a combination of the best of materials, sensors, positioning devices and control strategies. In ultra-precision design, it is extremely likely that there will be few design options for selection. In the case of ultra fine tool feed, the piezoelectric actuator is a potential choice. Currently, European and Japanese tool manufacturers are investigating magnetostrictive actuators for this purpose. Both piezoelectric and magnetostrictive materials suffer from hysteresis type non-linearity, so that the output of such systems depends upon the previous input, and absolute positioning is only achievable with the aid of feedback control. This work compares several modern control techniques for the positioning of a tool post for ultra- precision machining of brittle materials (in the nanometric range), e.g., lead-lag filter, PI+D, PID+feedforward, and fuzzy logic/neural network. The performance of the micropositioning device using both piezoelectric and magnetostrictive (solid-state) actuators are assessed by means of simulation techniques. The performance results are compared with results obtained by other authors.