Candidate: José Roberto Branco Ramos Filho
Program: UFSC / POSMEC
Date: July, 2009
Advisor: Victor Juliano De Negri
Abstract: This work regards the fault detection and diagnosis in electrically modulated flow control valves. The detection and diagnosis is done through the evaluation of the valve’s internal forces. These forces are estimated by a behavioral model of a healthy valve, and then compared to the force that is actually applied on the valve by the solenoid through the comparison between the current imposed to the solenoid by the controller and estimated maximum and minimum currents that should be applied to a healthy valve under certain operation conditions. In order to so, notions about automated diagnosis and about electrically modulated control valves are presented. Spool servoproportional valves are presented in detail. Also, the most common faults and its causes are reviewed. Experiments on a test bench in accordance with ISO 10770-1 (ISO, 1998) were made to characterize the valve used in this work, and based on the results of these experiments and on the notions presented, a model of the current on the valve’s solenoid was developed. This model was evaluated against the valve used on the experiments under three conditions: healthy, contaminated and wear degraded. The objective is to validate the model and evaluate its usefulness to detect and diagnose the faults inflicted on the valve. Recommendations on how the information provided by the model should be used, along with other variables measured on the valve and on the hydraulic circuit, to detect and diagnose faults are then presented, based on the findings made on the validation experiments.
Ramos Filho, J. R B.. Análise Teórico-Experimental de Falhas em Válvulas Direcionais Servoproporcionais. 2009. Dissertação (Mestrado em Engenharia Mecânica). Universidade Federal de Santa Catarina, Florianópolis. 134 p.