7Bauer F, Murrenhoff H. Piezo actuators-the future for high dynamically driven servo-valves. In: Fluid Power Transmission and Control, ICFP 2005, 2005 April 5--8. Hangzhou: International Academic Publisher, 2005. 62-68.
8Lindler J E, Andersone H. Piezoelectric direct drive servovalve. In: Proceeding of SPIE 2002 on Industrial and Commercial Applications of Smart Structures Technologies. San Diego: SPIE Press, 2002. 488--496.
9Reichert M, Murrenhoff H. New concepts and design of high response hydraulic valves using Piezo-technology. Power transmission and motion control. Bath: University of Bath, 2006. 401--414.
10Wong A P, Bullough W A, Chin S B, et al. Performance of the piezo-poppet valve, Part 1. In: Proceedings of the Institution of Mecha.nical Engineers, Part Ⅰ. J S yst Con Eng, .2006, 220:439-451.
