“…OGxGzG is the plane of symmetry of the aircraft. If one single engine is mounted on an aircraft, it is typically located at the CG of aircraft's fuselage 30 ; while if the aircraft has two or more engines, they are generally mounted symmetrically on horizontal or vertical wings 26 with a spatial distance from the CG. The former hypothesis can be regarded as a special case of the latter, hence the latter is adopted herein.Figure 2.Aircraft body frames of reference with different orientations: (a) conventional orientation and (b) particular orientation in accordance with the rotor shaft and base.…”
Section: Coordinate Systems and Motionsmentioning
confidence: 99%
“…Based on analytical method combined with numerical calculation, Hou et al. 28–30 simulated dynamic characteristics of a Jeffcott rotor with a centralized or offset disk in different flight environments (hovering, 28 climbing–diving, 29 and sinusoidal flight in the vertical plane 30 ). Several supports (rigid support, flexible support with cubic nonlinearity, and rolling bearings 31 ) were discussed.…”
During aircraft maneuvering flights, engine's rotor-bearing systems are subjected to parametric excitations and additional inertial forces, which may cause severe vibration and abnormal operation. Based on Lagrange's principle combined with finite element modeling, the differential equations of motion for a squeeze film damped rotor-bearing system mounted on an aircraft in maneuvering flight are derived. Using Newmark–Hilber–Hughes–Taylor integration method, dynamic characteristics of the nonlinear rotor system under maneuvering flight are investigated. The factors are considered, involving mass unbalance, oil–film force, gravity, parametric excitations and additional inertial forces, and instantaneous static eccentricity of journal induced by maneuvering loads. The effects of forward velocity, radius of curvature, rotating speed, mass unbalance, oil–film clearance, and elastic support stiffness on transient responses of rotor system are discussed during diving–climbing maneuver. The results indicate that when the aircraft performs a diving–climbing maneuver in the vertical plane, the journal deviates from the center of oil–film outer ring, and the excursion direction of whirl orbit is determined by centrifugal acceleration and additional gyroscopic moment. The journal whirls asynchronously around the instantaneous static eccentricity and its magnitude is related to the maneuvering loads and the supporting stiffness. Increasing forward velocity or decreasing pitching radius, the rotor vibration will enter earlier into or withdraw later from the relatively large eccentricity. Rotating near critical speeds or excessive mass unbalances should be prevented during maneuvering flights. For large maneuver, the oil–film radial clearance needs to be enlarged properly to avoid hard contact between journal and outer ring. In addition, the stiffness of elastic support needs to be appropriately determined for damping performance. Overall, it provides a flexible approach with good expandability to predict dynamic characteristics of on-board squeeze-film damped rotor system during maneuvering flights in the design process.
“…OGxGzG is the plane of symmetry of the aircraft. If one single engine is mounted on an aircraft, it is typically located at the CG of aircraft's fuselage 30 ; while if the aircraft has two or more engines, they are generally mounted symmetrically on horizontal or vertical wings 26 with a spatial distance from the CG. The former hypothesis can be regarded as a special case of the latter, hence the latter is adopted herein.Figure 2.Aircraft body frames of reference with different orientations: (a) conventional orientation and (b) particular orientation in accordance with the rotor shaft and base.…”
Section: Coordinate Systems and Motionsmentioning
confidence: 99%
“…Based on analytical method combined with numerical calculation, Hou et al. 28–30 simulated dynamic characteristics of a Jeffcott rotor with a centralized or offset disk in different flight environments (hovering, 28 climbing–diving, 29 and sinusoidal flight in the vertical plane 30 ). Several supports (rigid support, flexible support with cubic nonlinearity, and rolling bearings 31 ) were discussed.…”
During aircraft maneuvering flights, engine's rotor-bearing systems are subjected to parametric excitations and additional inertial forces, which may cause severe vibration and abnormal operation. Based on Lagrange's principle combined with finite element modeling, the differential equations of motion for a squeeze film damped rotor-bearing system mounted on an aircraft in maneuvering flight are derived. Using Newmark–Hilber–Hughes–Taylor integration method, dynamic characteristics of the nonlinear rotor system under maneuvering flight are investigated. The factors are considered, involving mass unbalance, oil–film force, gravity, parametric excitations and additional inertial forces, and instantaneous static eccentricity of journal induced by maneuvering loads. The effects of forward velocity, radius of curvature, rotating speed, mass unbalance, oil–film clearance, and elastic support stiffness on transient responses of rotor system are discussed during diving–climbing maneuver. The results indicate that when the aircraft performs a diving–climbing maneuver in the vertical plane, the journal deviates from the center of oil–film outer ring, and the excursion direction of whirl orbit is determined by centrifugal acceleration and additional gyroscopic moment. The journal whirls asynchronously around the instantaneous static eccentricity and its magnitude is related to the maneuvering loads and the supporting stiffness. Increasing forward velocity or decreasing pitching radius, the rotor vibration will enter earlier into or withdraw later from the relatively large eccentricity. Rotating near critical speeds or excessive mass unbalances should be prevented during maneuvering flights. For large maneuver, the oil–film radial clearance needs to be enlarged properly to avoid hard contact between journal and outer ring. In addition, the stiffness of elastic support needs to be appropriately determined for damping performance. Overall, it provides a flexible approach with good expandability to predict dynamic characteristics of on-board squeeze-film damped rotor system during maneuvering flights in the design process.
“…For conventional rotor bearing system, the system dynamics under base motion condition has already trigged attention from both academia and industry [10][11][12][13][14][15]. However, to date, the research work regarding AMB controller design are mainly based on static base conditions and only a few has focused on controller design linked to base motion conditions.…”
Active magnetic bearing (AMB) has been increasingly applied in high-speed rotating machinery applications because of the inherent merit of providing contactless magnetic force to levitate rotor. Generally, rotor AMB systems are applied in the static base situation whereas the recent work has also demonstrated their applicability in moving base conditions. Compared with traditional static base condition, the base motion condition is more complicated for rotor AMB system. For a better controller design and dynamic analysis, the dynamic modeling of AMB system operating in base motion condition is critical. However, the dynamics modeling of AMB system working in base motion condition has been rarely reported. Particularly, the rotational base motions are always neglected. Herein, in this work, based on a double-gimbal system model, we propose and develop a dynamic modeling method for AMB system considering both translational and rotational base motions. The derivation reveals that the translational base motion is equivalent to the external force applied to the rotor and the rotational base motion is equivalent to the external torque applied to the rotor. Furthermore, making use of the proposed dynamic model, we also analyze the dynamics of rotor displacement in the impact base motion condition from the aspects of excitation amplitude, pulse width and supporting parameters.
“…Consequently, this also led scholars to research different types of load. For example, Hou et al studied the nonlinear response and bifurcation analysis of a doffing type rotor model under sine load [ 1 ]. Bessam detected broken rotor bar faults in induction motor at low loads by using a neural network [ 2 ].…”
Section: Introductionmentioning
confidence: 99%
“…Modern load identification methods have rarely been applied to a rotor system in rotating machinery, and identification of rotor systems for various load types is uncommon. In this study, based on these typical load conditions in a rotor system, five typical types of loads have been refined for study, namely impact load, steady load, linear load, sinusoidal load, and transient load [ 1 , 2 , 3 , 4 ]. Specifically, an identification method for load categories is proposed here based on vibration signals of the rotor system.…”
Rotating machinery is often subjected to variable loads during operation. Thus, monitoring and identifying different load types is important. Here, five typical load types have been qualitatively studied for a rotor system. A novel load category identification method for rotor system based on vibration signals is proposed. This method is a combination of ensemble empirical mode decomposition (EEMD), energy feature extraction, and back propagation (BP) neural network. A dedicated load identification test bench for rotor system was developed. According to loads characteristics and test conditions, an experimental plan was formulated, and loading tests for five loads were conducted. Corresponding vibration signals of the rotor system were collected for each load condition via eddy current displacement sensor. Signals were reconstructed using EEMD, and then features were extracted followed by energy calculations. Finally, characteristics were input to the BP neural network, to identify different load types. Comparison and analysis of identifying data and test data revealed a general identification rate of 94.54%, achieving high identification accuracy and good robustness. This shows that the proposed method is feasible. Due to reliable and experimentally validated theoretical results, this method can be applied to load identification and fault diagnosis for rotor equipment used in engineering applications.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
