Abstract
The nozzle-flapper type servovalve has good characteristics (high response, compact design, low consumption), so it is used in many fields, e.g. aeroplanes, test machines, etc.
However, this type of servovalve needs first stage flow which causes leakage, and the user should take care to keep contamination levels low. For these reasons, the need for direct drive servovalves (DDV) is increasing. The DDV does not have first stage flow and is not influenced by contamination.
In this paper, a new DDV using a giant magnetostrictive material is presented. By using this material, a high performance DDV can be developed, i.e. with high output power, high response, high resistance to environmental factors (e.g. humidity, oil etc.).
