Flywheel Rotor System Research Articles

Intelligent Early Fault Diagnosis of Space Flywheel Rotor System.

Three frequently encountered problems-a variety of fault types, data with insufficient labels, and missing fault types-are the common challenges in the early fault diagnosis of space flywheel rotor systems. Focusing on the above issues, this paper proposes an intelligent early fault diagnosis method based on the multi-channel convolutional neural network with hierarchical branch and similarity clustering (HB-SC-MCCNN). First, a similarity clustering (SC) method is integrated into the parameter-shared dual MCCNN architecture to set up as the basic structural block. The hierarchical branch model and additional loss are then added to SC-MCCNN to form a hierarchical branch network, which simplifies the problem of fault multi-classification into binary classification with multi-steps. Based on the self-learning characteristics of the proposed model, the unlabeled data and the missing fault types in the training set are re-labeled to realize the re-training of the network. The results of the experiments for comparing the abilities between the proposed method and several advanced deep learning models confirm that on the established early fault dataset of the space flywheel rotor system, the proposed method successfully achieves the hierarchical diagnosis and presents stronger competitiveness in the case of insufficient labeled data and missing fault types at the same time.

Study on nonlinear force transmissibility of flywheel rotor system considering periodic base motions

This paper reports on the study of the dynamic force transmissibility (DFT) of flywheel rotor system (FRS), considering periodic base motions and nonlinear support stiffness of angular contact ball bearings (ACBBs). The energy method and Lagrange equation are adopted to deduce the base induced additional excitations, including the internal (gyroscopic and stiffness) and external excitations. The influence of combined loads and contact angle variation is introduced into the Jones formula to accurately solve for the internal load distribution and nonlinear stiffness of the ACBBs. The lateral vibration model of FRS considering base motions and ACBB nonlinear support stiffness is then established. The DFT of the system is obtained by combining the harmonic balance method and alternate frequency/time domain method. The arc length continuation method is employed to track the multi-solution region owing to bifurcation. In addition, the stability of harmonic balance solutions is determined through eigenvalue analysis in the frequency domain. Both numerical integration and comparison with literature results are used to verify the accuracy of the proposed DFT model and solution method. On the basis of these results, the effects of base motion amplitude, ACBB axial preload, and rotor damping on the DFT of the system are discussed. With the increase of radial deformation, the support stiffness of ACBB under axial preload shows “soft” and “stiff” characteristics in turn. The additional excitation caused by the base motions is the key factor determining the nonlinear characteristics of FRS. These results support designing a reasonable vibration isolation system and reducing the transmission of FRS dynamic response to the spacecraft platform.

Stability analysis and control of a flywheel energy storage rotor with rotational damping and nonsynchronous damping

Based on the principle of Lagrange mechanics, especially considering the effects of rotation damping and nonsynchronous damping, a radial 4-dimensional dynamic model of the flywheel bearing rotor system is proposed. Applying the Laplace eigenvalue method, the stability effects of rotational damping, nonsynchronous damping, and their coupling effects are investigated by means of root locus method. Under the control of the linear quadratic regulator, dynamical characteristics of the flywheel bearing rotor system with varied rotational damping and nonsynchronous damping are also studied. The results show that the rotation damping, nonsynchronous damping, and their coupling effects have vast and complex instability effects on high-speed flywheel bearing rotor system. However, there are three exceptions. The tiny proportional rotational damping, remaining below 12%, and the minuscule proportional co-nonsynchronous damping; the product of the nonsynchronous damping and the speed ratio below 5% both can enhance the stability of the system. Furthermore, in the situation that the counter-nonsynchronous damping is coupled with the large proportion of rotational damping, the stability of the system can also be boosted distinctly. On the other hand, the numerical experimental results show that the rotational damping and nonsynchronous damping have a beneficial effect on the flywheel system controlled by linear quadratic regulator. In addition, under the control of linear quadratic regulator, the transient dynamical behavior of the flywheel rotor system with rotational damping or co-nonsynchronous damping performed better than the flywheel rotor system with the coupled damping. The numerical simulations of the transient response of the flywheel rotor system under active control are consistent with some of the derived stability analysis results. The results about the stability analysis and the performance in vibration control give the suggestions for the instability control and fault detection of the system.

Nonlinear dynamic force transmissibility of a flywheel rotor supported by angular contact ball bearings

The dynamic force transmissibility (DFT) of aerospace flywheel rotor system (FRS) supported by angular contact ball bearings (ACBBs) is examined in this paper. The influence of combined loads and contact angle variation is considered in the Sjovall formula to accurately solve the load distribution and nonlinear stiffness of ACBB. Subsequently, the lateral vibration model of FRS is established by considering the nonlinear stiffness characteristics of ACBB. The DFT of the system is solved via harmonic balance method and arc length continuation, and the stability of the results is determined. Numerical integration and dynamic tests are utilized to verify the accuracy of harmonic balance results. Based on the proposed model, the effects of rotor unbalance excitation, axial preload, and rotor damping on the DFT of the system are discussed. The soft-stiff transition phenomenon is observed in terms of the varying supporting stiffness of ACBB wherein deformation is measured under axial preload. The value of rotor unbalanced mass determines the nonlinear characteristics of FRS. The results provide an important reference for dynamic performance evaluation and vibration isolation device design of aerospace FRS.

Parallel mode notch filters for vibration control of magnetically suspended flywheel in the full speed range

Undesired vibration force caused by harmonic currents is a common problem in a magnetically suspended flywheel (MSFW) rotor system. It poses a potential threat to system stability and performance degradation. In this work, multiple different phase-shift notch filters are connected in parallel mode to suppress the vibration harmonics. First, the multi-frequency vibrations in the MSFW is modelled and analysed. Then multiple different notch filters in parallel mode are proposed to plug into the baseline magnetically suspension system. The performance comparison with the conventional multiple notch filters is investigated. The parameters design and calculation for the proposed method are analysed in details. Moreover, the closed-loop stability of the overall system is given in the full speed range. Finally, simulation and experimental results for the MSFW demonstrate the superiority of the proposed method on both harmonics suppression and stability preservation.

Radial position control for magnetically suspended high‐speed flywheel energy storage system with inverse system method and extended 2‐DOF PID controller

To achieve high-precision position control for the active magnetic bearing high-speed flywheel rotor system (AMB-HFRS), a novel control strategy based on inverse system method and extended two-degree-of-freedom (2-DOF) proportional–integral–derivative (PID) controller is proposed in this study. First, the inverse system method is employed to decouple the AMB flywheel rotor system with strong non-linear and coupling, into four independent subsystems. Subsequently, extended 2-DOF PID controllers are used to regulate the decoupled subsystems, to obtain good performances of disturbance rejection and tracking simultaneously. In the extended 2-DOF PID controller, a differential signal is produced by a velocity observer to improve the ability of against noise. Finally, the characteristics of stability, tracking, disturbance rejection and robustness of the control strategy proposed are analysed in theory, and its ability and effectiveness to control the radial position of the AMB-HFRS are further studied by simulations and experiments. It is shown that the control strategy proposed can keep the AMB-HFRS suspending stably from static state to the speed of 24,000 rpm, has the advantages of good tracking, high disturbance rejection, strong robustness and good ability of against noise.

Internal model control for the AMB high‐speed flywheel rotor system based on modal separation and inverse system method

To eliminate the influence of gyroscopic effect on system stability and to improve the control performances for the active magnetic bearing (AMB) high-speed flywheel rotor system, a novel control strategy based on the modal separation and inverse system method is proposed. The translational motions and rotational motions of the AMB flywheel rotor system are firstly decoupled by the modal separation, then the rotational motions are decoupled by the inverse system method, so that the AMB flywheel rotor system, which is a multivariable and strong coupled system, is decoupled into four subsystems. Finally, the subsystems are regulated by four two-degrees-of-freedom (2-DOF) internal model controllers, respectively. Furthermore, the stability, tracking and robustness of the novel control strategy are analysed theoretically, and its effectiveness on vibration control of the AMB high-speed flywheel rotor system is further investigated by simulations and experiments. The results show that the novel control strategy can achieve stable suspension and effectively suppress the vibration of the AMB high-speed flywheel rotor system from static state to 24,000 rpm, with the advantages of high stability, strong robustness, and good performances of tracking and disturbance rejection simultaneously.

Flywheel energy storage system with a permanent magnet bearing and a pair of hybrid ceramic ball bearings

A flywheel energy storage system (FESS) with a permanent magnet bearing (PMB) and a pair of hybrid ceramic ball bearings is developed. A flexibility design is established for the flywheel rotor system. The PMB is located at the top of the flywheel to apply axial attraction force on the flywheel rotor, reduce the load on the bottom rolling bearing, and decrease the friction power loss. The magnetic force of the PMB is analyzed through finite element method, and the force with the air gap of the PMB is verified experimentally. A squeeze film damper (SFD) is introduced to support the bottom rolling bearing, suppress lateral vibration, and enhance the stability of the flywheel rotor system. A dynamic model of FESS is established through transfer matrix method, Jones-Harris rolling bearing theory, and a finite length bearing dynamic model for SFD, which is verified by measuring the amplitude-frequency response. The effect of SFD radial clearance and unbalanced mass distribution on the dynamics of FESS is discussed. A spin-down test for the FESS prototype is conducted in a moderate vacuum. Results show that the hybrid bearing and flexibility design for the rotor system allow for the use of a small rolling bearing to reduce the power loss of FESS caused by friction. The developed FESS is simple in structure, stable without active control, low in cost, and convenient in maintenance.

The Dynamic Analysis of High-Speed Energy Storage Flywheel Rotor System

This article aims at large-scale energy storage flywheel rotor system, obtaining the dynamic characteristics. Through theoretical analysis, and after doing a simulation analysis for a given flywheel rotor on the 0-20000 RPM, getting the flywheel rotor critical speed, the transient analysis and imbalance response. The system is in steady state at runtime according to the analysis results. Providing also certain theory basis for study of flywheel rotor system according to the analysis method .

Modal Analysis on 600 Wh Energy Storage Flywheel Rotor System

The three-dimensional finite element model of 600 Wh energy storage flywheel rotor system supported by active magnetic bearing (AMB) was built with the commercial software ANSYS to carry out the modal analysis. The modeling method of the AMB and their effect on the rotor system are explored. Modal analysis was performed, and the modal shapes of the rotor system were obtained. The Campbell diagram calculated by ANSYS was gained to be compared with the one calculated by the theoretical dynamics model. This research provides a theoretical basis for the rotor system design. The ideas and methods can be used as a reference for the study of dynamic characteristics of the rotor system and direct the flywheel prototype future design.

Theoretical Vibration Analysis on 600 Wh Energy Storage Flywheel Rotor—Active Magnetic Bearing System

This paper shows a theoretical vibration analysis regarding the controller’s parameters and the gyroscopic effect, based on a simplified rotordynamic model. Combined with 600 Wh energy storage flywheel rotor system mathematical model, the Campbell diagram of the rotor system was obtained by the calculation of the whirl frequency under different parameters of the controller in MATLAB to analyze the effect of the controller parameter on the whirl frequency and to limit the operating speed and acceleration or deceleration of the rotor. The result of the analysis can be used to set the support position of the rotor system, limit the ratio of transverse moment of inertia and the polar moment of inertia, and direct the flywheel prototype future design. The presented simplified rotordynamic model can also be applied to rotating machines.

Study of the LQR Controller for Magnetic Flywheel Rotor System

Gyroscopic effects in the flywheel rotor greatly influence rotor stability especially at high speed. When the pole-zero position moves to right of s-plane, the damping of the pole is getting smaller, and the stability of system is getting worse with the increasing of rotor speed when the decentralized PD control law is used only. The LQR (linear quadratic regulator) control method is used to reduce gyroscopic effect and forced vibration. The simulation results show that LQR controller have a good performance on the reduction of gyroscopic effect and vibration of magnetic flywheel rotor system.

Flywheel rotor manufacture for rural energy storage in sub-Saharan Africa

This paper presents the design of flywheel rotor prototypes developed to enhance rural energisation in sub-Saharan Africa. The flywheel rotors are made from locally available fibre and epoxy resin. The profiles were designed using novel shape profiles based on Berger, Porat and Stodola’s designs and manufactured using locally available materials. One of the flywheel rotor profiles was tested on a rig with an Axial Flux Permanent Magnet Machine and it was able to store 227 kJ of energy. A life cycle cost analysis was performed to compare the energy costs between a lead acid battery system and a flywheel rotor system. It was realized that by integrating the flywheel system into Solar Home Systems, a cost saving of 37% per kWh for rural system installations would be achieved.

Modeling and Consideration of AMB-Flywheel Supported by Two-axis Gimbals

A flywheel energy storage system using an active magnetic bearing (AMB) is an effective method for storing electric power and reducing energy consumption. The stabilization of a flywheel rotor system supported by magnetic bearings fixed on the ground has been done. Currently, an electrical vehicle with a flywheel energy storage system using a magnetic bearing and a two-degree-of freedom gimbal which means two-axis gimbal have been carrying out. In this paper, the mathematical model for both the flywheel and the gimbals has been derived. Also, a discussion of the gimbal design is presented. It was verified through experiments that the proposed model in this paper is very effective.

Study on electromechanical coupling nonlinear vibration of flywheel energy storage system

The electromechanical coupling dynamics of the flywheel energy storage system (FESS) with a hybrid permanent magnetic-dynamic spiral groove bearing has been studied. The functions of the kinetic energy, the potential energys, the magnetic field energy in air gap of the flywheel motor and the energy dissipation of the whole system were obtained, and the differential equations set with electromagnetic parameters of FESS was established by applying the extended Lagrange-Maxwell equation. The four-order implicit Runge-Kutta formula to the equations was derived, and the nonlinear algebraic equations were solved by using the Gauss-Newton method. The analytical solution of an example shows that the upper damping coefficient, the lower damping coefficient and the residual magnetic induction of the rare earth permanent magnet play an important role in electromechanical resonance of the flywheel rotor system. There is a small change for the electromechanical coupling resonance frequency with the upper damping coefficient increasing, but the resonance amplitude decreases with the upper damping coefficient increasing. With the lower damping coefficient increasing, the resonance frequency increases, and the resonance amplitude decreases. With the residual magnetic induction of the permanent magnet increasing, the resonance frequency decreases, and the resonance amplitude increases.

Active permanent magnet support for a superconducting magnetic-bearing flywheel rotor

This paper proposes a novel active permanent magnet support approach to improve the lateral stiffness of a superconducting magnetic-bearing flywheel rotor system. An actual flywheel rotor system levitated with high-temperature superconducting magnetic bearings is modeled and then analyzed with a moving permanent magnet support placed at the top of the rotor. The active support principle defined in this study is based on moving the permanent magnet support 180/spl deg/ out of the phase with the rotor displacement. A complete dynamical equation of the flywheel rotor is derived including gyroscopic effects. Analysis showed the active support of the flywheel rotor with additional permanent magnet movements decreased the amplitude of flywheel rotor vibration considerably.