Abstract: This paper presents a new method of fault diagnosis i.e.the ripple model method.Firstly we establish an effective ripple parameter model with two parameters(Qs and Zs).Then we analyze the slipper lossing failures of ZB-34M bent-axis piston pump qualitatively and quanti-tatively.the results illustrate that the changes of inner structure parameters lead to the changes of ripple parameters.So after monitoring the changes of Qs and Zs,we can discover the changes of structure,then realize the fault diagnosis.

Key words: Hydraulic equipment, ripples一parameter idendification, fault-diagnosis