Active rotor vibration control

Author(s)

Matheus Freire Wu

• Document type: Doctoral Thesis
• Press: Campinas, SP.
• Institution: Universidade Estadual de Campinas (UNICAMP). Faculdade de Engenharia Mecânica
• Defense date: 2020-04-30

Examining board members

Katia Lucchesi Cavalca Dedini; Alberto Luiz Serpa; André Ricardo Fioravanti; Marcelo Becker; Aldemir Aparecido Cavalini Júnior

• Advisor: Katia Lucchesi Cavalca Dedini

Abstract

This thesisf objective is to study the possible applications of feedback and feedforward active control methods through magnetic actuator to stabilize and attenuate the lateral vibration of rotors supported by cylindrical hydrodynamic bearings. Rotors supported by cylindrical hydrodynamic bearings commonly have their operational speed threshold limited at approximately twice their first critical speed due to the auto excitation phenomenon known as oil whip (or fluid induced instability). Such behavior can be linearly described by a loss in the equivalent direct damping coefficients and the rise of bearing cross-coupled stiffness coefficients depending on the shaft rotational velocity. Besides the speed variation, the possibility of uncertainties due to bearing abrasion wear is also considered. Therefore, output feedback MIMO controllers are designed to be robust to such parametrical variations are designed. Specifically, it is demonstrated the application of static H¿ controllers linearly dependent on the rotational speed. Static controllers are relatively easy to design and implement, but they have low damping capability, and, thus, achieving limited attenuation range. Therefore, a feedforward force compensation control is proposed in order to improve the general control system performance. The method is based on model and explores the periodicity, which response is mostly composed of operational frequency harmonics even under fault and wear condition. The feedforward force is calculated to minimize the response modal components by least squared minimization. The proposed methods are tested and validated in two distinct test rigs. The first one is composed by a single journal bearing and an active magnetic bearing, beside other auxiliary components, which allowed to test the controllers in a simpler condition. The second test rig is composed by two journal bearings and a magnetic actuator, which is a more challenging configuration to control. Key Word: Rotating machinery, varying H¿ control, feedforward control, journal bearing, magnetic actuator (AU)

• FAPESP's process: 16/13059-1 - Linear parameter varying control applied to rotating machinery
• Grantee: Matheus Freire Wu
• Support Opportunities: Scholarships in Brazil - Doctorate (Direct)