Rastreamento robusto de perfis de pressão ou de vazão em uma bancada de testes hidráulicos via controle de torque em modos deslizantes

Abstract

In this work a robust control system is developed aiming the tracking of flow or pressure pre-defined profiles, in a hydraulic test bench available in the Centro de Pesquisas Hidráulicas e Recursos Hídricos (CPH) at Universidade Federal de Minas Gerais. The hydraulic bench was previously built and only few modifications in its instrumentation were necessary. The bench is comprised by two induction motors driving centrifugal pumps at variable speed by means of commercial Frequency Inverters. The system to be controlled is inherently uncertain because it is used to test different hydraulic equipments by reconfiguring the hydraulic circuit connections. In order to couple with the uncertainties, a robust control system is proposed which is based on sliding mode control in order to guarantee a good tracking performance even for large variations on the hydraulic load, without resorting to controller tunning. The proposed control strategy is based on sensorless torque control resources for induction motors available in an commercial Frequency Inverter. To accomplish this control design, a white-box model was built and validated by means of static and dynamic tests. The developed system was tested in simulation and also implemented in practice. The obtained experimental results show that the control system is capable of tracking flow or pressure profiles, and that the technique can be used for variable speed control in water pumping systems.