Abstract of Thesis presented at COPPE/UFRJ as a partial fulfillment of the requirements for the degree of Master of Science (M.Sc.)

Modeling, Identification, Simulation and Control of Hydraulic Actuated Fatigue Testing Machines

Diego Pereira Dias

June/2014

Advisors:

Ramon Romankevicius Costa Alessandro Jacoud Peixoto

Department:

Eletrical Engineering

      This thesis addresses the modeling, identification and control of hydraulic actuated fatigue testing machines. A literature review on hydraulic actuation for fatigue testing machines is provided and a prototype for fatigue test is implemented in the Nondestructive Testing, Corrosion and Welding Laboratory (LNDC)/COPPE of Federal University of Rio de Janeiro. A simulator is developed with parameters obtained during the identification process and experimental tests are conducted to validate the fatigue testing behavior. An appropriate least square based methodology for force friction identification is proposed by considering the Stribeck force friction model. It is verified via numerical simulations that the specimen equivalent spring constant variation must be compensated via force feedback. A conventional proportional control with fixed gain can solve satisfactorily only the position tracking problem. It is verified that a more elaborate control scheme is needed to solve the force tracking problem while the crack grows with time. The crack growth results in a equivalent spring with a time varying stiffness. Simulations and experimental results are provided to show the effectiveness of the proposed friction force identification and control schemes.