Design of natural frequency adjustable electromagnetic actuator and active vibration control test

Measurement Science Review

Ren

et al. 2018

It is important to improve the natural frequency of test device to improve measurement accuracy. First-order frequency is basic frequency of dynamic model, which generally is the highest vibration energy of natural frequency. Taking vector force test device (VFTD) as example, a novel dynamic design method for improving first-order natural frequency by increasing structure stiffness is proposed. In terms of six degree-of-freedom (DOF) of VFTD, dynamic model of VFTD is built through the Lagrange dynamic equation to obtain theoretical natural frequency and mode shapes. Experimental natural frequency obtained by the hammering method is compared with theoretical results to prove rationality of the Lagrange method. In order to improve the stiffness of VFTD, increase natural frequency and meet the requirement of high frequency test, by using the trial and error method combined with curve fitting (TECF), stiffness interval of meeting natural frequency requirement is obtained. Stiffness of VFTD is improved by adopting multiple supports based on the stiffness interval. Improved experimental natural frequency is obtained with the hammering method to show rationality of the dynamic design method. This method can be used in improvement of first-order natural frequency in test structure.

Section: First-order Natural Frequency Improvement Of Vftdmentioning

confidence: 95%

“…i φ is ith-order mode vector. Therefore, natural frequencies and modes of each order can be obtained by (8).…”

Section: A Dynamic Equations Of Vftd Based On the Lagrange Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

A Novel Dynamic Method to Improve First-order Natural Frequency for Test Device

Measurement Science Review

Ren

et al. 2018

“…For the case of collocated actuator and sensor pairs with C ¼ B T , letting Thus, it is obvious that B ¼ U 1 , C ¼ U T 1 and G ¼ S. Moreover, the following parameterized solutions can be proposed through rewriting equation (10) as…”

Section: Applications Of the Formulamentioning

confidence: 99%

An explicit formula of perturbating stiffness matrix for partial natural frequency assignment using static output feedback

Journal of Low Frequency Noise, Vibration and Active Control

Ouyang

et al. 2018

The partial eigenvalue (or natural frequency) assignment or placement, only by the stiffness matrix perturbation, of an undamped vibrating system is addressed in this paper. A novel and explicit formula of determining the perturbating stiffness matrix is deduced from the eigenvalues perturbation theorem for a low-rank perturbed matrix. This formula is then utilized to solve the partial eigenvalue (or natural frequency) assignment via the static output feedback. The control matrix, output matrix and feedback gain matrix can be explicitly expressed and easily constructed.

“…Active control refers to the use of the sensor to collect signals and feedback for the controller to drive the damper to reduce vibration. Passive control refers to vibration control that can be performed without additional controllers and input energy [7].Active control of the unbalanced single-side cantilevered rotor system includes: (1) using active control to change the natural frequency of the system to avoid the resonance region to achieve vibration control [8] such as installing the mass on the shaft end of the system and changing the position of the mass by PD control. However, when the mass block is applied, the unbalanced excitation of the rotor system will increase, causing the shaft to bend [9]; and (2) using active control to apply external force that moves in the opposite direction to the exciting force, thereby achieving good vibration control such as applying external force at the impeller of the system through proportional gain feedback control.…”

mentioning

confidence: 99%

Vibration Control of an Unbalanced Single-Side Cantilevered Rotor System with a Novel Integral Squeeze Film Bearing Damper

Yang

et al. 2019

Applied Sciences

Featured Application: The proposed integral squeeze film bearing damper can effectively decrease the vibration of an unbalanced single-side cantilevered rotor system such as a flue gas turbine and pump. Abstract: In this paper, vibration control of an unbalanced single-side cantilevered rotor system using a novel integral squeeze film bearing damper in terms of stability, energy distribution, and vibration control is analyzed. A finite element model of such a system with an integral squeeze film bearing damper (ISFBD) is developed. The stability, energy distribution, and vibration control of the unbalanced single-side cantilevered rotor system are calculated and analyzed based on the finite element model. The stiffness of the integral squeeze film bearing damper is designed using theoretical calculation and finite element model (FEM) simulation. The influence of installation position and quantity of integral squeeze film bearing dampers on the vibration control of the unbalanced cantilevered rotor system is discussed. An experimental platform is developed to validate the vibration control effect. The results show that the installation position and quantity of the integral squeeze film bearing dampers have different effects on the stability, energy distribution, and vibration control of the unbalanced cantilevered rotor system. When ISFBDs are installed at both bearing housings, the vibration control is best, and the vibration components of the time and frequency domains have good vibration control effects in four working conditions. External excitations are mainly caused by the impact load and pulsation excitation of the fluid. When the excitation frequencies are close to the natural frequencies of the system, the resonance occurs in the system, causing unpredictable losses.With the rapid development of the single-side cantilevered rotor system, the vibration problems have become increasingly prominent. These problems pose a huge threat to safety production and economic benefits. In actual civil and military equipment, rotor systems often vibrate due to unbalance, resulting in impeller fracture, seal failure, bearing damage, valve failure, pipeline leakage, and loose foundation [6]. These faults cause equipment damage or even major safety accidents, along with unpredictable personal injury to users. So, it is necessary to control the vibration of the unbalanced single-side cantilevered rotor.The vibration mechanism of the unbalanced single-side cantilevered rotor system has already been researched by many scholars. According to the obtained theory, the vibration control of the system is divided into four types: structural modification, vibration absorption, vibration isolation, and vibration damping. At the same time, the vibration control method is divided into two types: active and passive control. Active control refers to the use of the sensor to collect signals and feedback for the controller to drive the damper to reduce vibration. Passive control refers to vibration control that can be performed without add...