Candidate: Yesid Ernesto Asaff Mendoza
Program: UFSC / POSMEC
Date: December, 2006
Advisor: Victor Juliano De Negri
Abstract: This paper presents the theoretical-experimental study of a servo-pneumatic system whose purpose is to control the position of turbine blades used in hydroelectric power plants. The system is composed of two double-acting cylinders, controlled trough a servo-pneumatic valve, with a position sensor and digital controller. The system is designed to meet the requirements of a 400 KW speed governor plant, comparing its performance with the normally used hydraulic systems. For this reason, a non-linear model was developed for a pneumatic servo-position, which includes non-linear relationship related to mass flow in the servo-valve, with pressure and electric voltage. The actuator is modeled considering the continuity equations in the chambers and the movement equation involves a variable viscous friction model.Based on the developed model, the controller is designed in order to overcome the dynamic limitation and system non-linearity. To validate the mathematic model proposed and the controller, a comparison was made using experimental data from a test bench that provides results with numerical simulation that reproduces experimental conditions. Based on the characteristics found through generating and testing the mathematical model, fully satisfactory results were achieved, where good agreement between the theoretical results and the actual physical measured data system demonstrates that this model is adequate to verify the performance of pneumatic systems in closed-loop control. These experimental results attest to the efficacy of the servo-pneumatic system as a viable system in the drive of speed governors of turbines in small hydroelectric power plant; a good system response is observed in reference to setting time, position errors and synchronization.
ASAFF, Y. E. M. Desenvolvimento de um Sistema Servo-Pneumático para Regulação de Velocidade de Turbinas em pequenas Centrais Hidrelétricas. 2006. Dissertação (Mestrado em Engenharia Mecânica). Universidade Federal de Santa Catarina, Florianópolis.