Numerical and experimental investigation of a semi-active vibration control system by means of vibration energy conversion. - In: Energies : open-access journal of related scientific research, technology development and studies in policy and management.. - Basel : MDPI, ISSN 1996-1073, Bd. 14 (2021), 16, S. 1-19
A vibration control concept based on vibration energy conversion and storage with respect to a serial-stiffness-switch system (4S) has previously been proposed. Here, we first present a rotational electromagnetic serial-stiffness-switch system as a novel practical vibration control system for experimental validation of the concept and, furthermore, an improved control strategy for higher vibration suppression performance is also proposed. The system consists of two spring-switch elements in series, where a parallel switch can block a spring. As an alternating mechanical switch, the experimental system uses two electromagnets with a shared armature. By connecting the armature to the rotating load or the base, the electromagnets decide which of the two spiral springs is blocked, while the other is active. A switching law based on the rotation velocity of the payload is used. Modelling and building of the experimental system were carried out. The corresponding experiment and simulation were executed and they matched well. These results prove that our serial-stiffness-switch system is capable of converting vibration energy and realizing vibration reduction under a forced harmonic disturbance. The effects of disturbance frequency, disturbance amplitude and sampling frequency on the system performance are shown as well. A position feedback control-based switching law is further put forward and experimentally verified to improve the repositioning accuracy of the disturbed system.
Steady state response analysis for a switched stiffness vibration control system based on vibration energy conversion. - In: Nonlinear dynamics : an international journal of nonlinear dynamics and chaos in engineering systems.. - Dordrecht [u.a.] : Springer Science + Business Media B.V, ISSN 1573-269X, Bd. 103 (2021), 1, S. 239-254
A novel semi-active vibration control concept with a serial-switch-stiffness-system was previously presented in our work. Differing from conventional vibration control systems, this system does not dissipate but converts vibration energy as potential energy stored in springs and then reacts against external disturbance. As a piecewise linear system, whether or not energy conversion limit happens is an interesting nonlinear dynamic issue related to the systems steady state response. This paper formulates this issue in depth using the approach called equivalence in control. The systems control force represented by the converted vibration energy is approximately decomposed into two portions. One is responsible for low-frequency free response and the other for high-frequency switching response. An equivalent linear system suffering from a decomposed high-frequency switching force is obtained instead of the original switched system. The steady state response of the disturbed system can be delivered through linear superposition as executed in a linear system. Energy conversion limit occurring in the system under a harmonic disturbance is numerically shown by means of fast Fourier transformation. Analytical formulation and numerical simulation for open- and closed-loop control of the system are further carried out, respectively. The results give that the proposed approach is capable of solving the stead state response of the switched system accurately, and meanwhile, energy conversion limit occurs in the vibration control system indeed. Experimental discussion is also executed.
Suppression of complex hysteretic resonances in varying compliance vibration of a ball bearing. - In: Shock and vibration. - Amsterdam : IOS Press, ISSN 1875-9203, (2020), insges. 11 S.
It is traditionally considered that, due to the Hertzian contact force-deformation relationship, the stiffness of rolling bearings has stiffening characteristics, and gradually researchers find that the supporting characteristics of the system may stiffen, soften, and even coexist from them. The resonant hysteresis affects the stability and safety of the system, and its jumping effect can make an impact on the system. However, the ball bearing contains many nonlinearities such as the Hertzian contact between the rolling elements and raceways, bearing clearance, and time-varying compliances (VC), leading great difficulties to clarify the dynamical mechanism of resonant hysteresis of the system. With the aid of the harmonic balance and alternating frequency/time domain (HB-AFT) method and Floquet theory, this paper will investigate the hysteretic characteristics of the Hertzian contact resonances of a ball bearing system under VC excitations. Moreover, the linearized dynamic bearing stiffness of the system will be presented for assessing the locations of VC resonances, and the nonlinear characteristics of bearing stiffness will also be discussed in depth. Our analysis indicates that the system possesses many types of VC resonances such as the primary, internal, superharmonic, and even combination resonances, and the evolutions of these resonances are presented. Finally, the suppression of resonances and hysteresis of the system will be proposed by adjusting the bearing clearance.
Mechanism and characteristics of global varying compliance parametric resonances in a ball bearing. - In: Applied Sciences : open access journal.. - Basel : MDPI, ISSN 2076-3417, Volume 10 (2020), issue 21, 7849, Seite 1-28
Varying compliance (VC) is an unavoidable form of parametric excitation in rolling bearings and can affect the stability and safety of the bearing and its supporting rotor system. To date, we have investigated VC primary resonance in ball bearings, and in this paper other parametric VC resonance types are addressed. For a classical ball bearing model with Hertzian contact and clearance nonlinearities between the rolling elements and raceway, the harmonic balance and alternating frequency/time domain (HB-AFT) method and Floquet theory are adopted to analyze the VC parametric resonances and their stabilities. It is found that the 1/2-order subharmonic resonances, 2-order superharmonic resonances, and various VC combination resonances, such as the 1-order and 2-order summed types, can be excited, thus resulting in period-1, period-2, period-4, period-8, period-35, quasi-period, and even chaotic VC motions in the system. Furthermore, the bifurcation and hysteresis characteristics of complex VC resonant responses are discussed, in which cyclic fold, period doubling, and the second Hopf bifurcation can occur. Finally, the global involution of VC resonances around bearing clearance-free operations (i.e., adjusting the bearing clearance to zero or one with low interference) are provided. The overall results extend the investigation of VC parametric resonance cases in rolling bearings.
Design of a novel magnetorheological damper adaptable to low and high stroke velocity of vehicle suspension system. - In: Applied Sciences : open access journal.. - Basel : MDPI, ISSN 2076-3417, Volume 10 (2020), issue 16, 5586, 17 Seiten
In this study, a new class of magnetorheological (MR) damper, which can realize desired damping force at both low and high speeds of vehicle suspension systems, is proposed and its salient characteristics are shown through computer simulations. Unlike conventional MR dampers, the proposed MR damper has a specific pole shape function and therefore the damping coefficient is changed by varying the effective area of the main orifice. In addition, by controlling the opening or closing the bypass orifice, the drastic change of the damping coefficient is realizable. After briefly describing the operating principle, a mathematical modeling is performed considering the pole shape function which is a key feature of the proposed MR damper. Then, the field-dependent damping force and piston velocity-dependent characteristics are presented followed by an example on how to achieve desired damping force characteristics by changing the damping coefficient and slope breaking point which represents the bilinear damping property.
Towards optimal control of concentric tube robots in stereotactic neurosurgery. - In: Mathematical and computer modelling of dynamical systems : MCMDS.. - London [u.a.] : Taylor & Francis, ISSN 1744-5051, Bd. 25 (2019), 6, S. 560-574
Design and implementation of an new 6-DoF magnetic levitation positioning system. - In: IEEE transactions on magnetics : a publication of the IEEE Magnetics Society.. - New York, NY : IEEE, ISSN 1941-0069, Bd. 55 (2019), 12, S. 8107407, insges. 7 S.
Comparative study between dry friction and electrorheological fluid switches for Tuned Vibration Absorbers. - In: Journal of sound and vibration. - London : Academic Press, ISSN 0022-460X, Bd. 460 (2019), 114874
Semi-analytical 3D force calculation of an ironless cylindrical permanent magnet actuator for magnetic levitation systems. - In: Applied Computational Electromagnetics Society journal. - Monterey, Calif., ISSN 1054-4887, Bd. 34 (2019), 4, S. 520-527
Damping adjustment utilizing digital electrorheological valves with parallely segmented electrodes. - In: Smart materials and structures. - Bristol : IOP Publ., ISSN 1361-665X, Volume 28 (2019), number 7, 075013, Seite 1-16