• Title, Summary, Keyword: angular stability

Search Result 194, Processing Time 0.032 seconds

Dynamic Stability Analysis of a Spinning Disk with Angular Acceleration by Using the Uncoupled Governing Equations (비연성된 지배방정식을 이용한 각가속도를 갖는 회전원판의 동적 안정성 해석)

  • Choe, Tae-Yeong;Jeong, Jin-Tae
    • Transactions of the Korean Society of Mechanical Engineers A
    • /
    • v.24 no.6
    • /
    • pp.1363-1370
    • /
    • 2000
  • Dynamic stability of a flexible spinning disk with angular acceleration is considered. To avoid the coupling between the in-plane and out-of-plane displacements, the linearized strain-displacement relations are used in the Kirchhoff plate theory. The uncoupled governing equations are derived by using Hamilton's principle with considering the angular acceleration. Numerical tests show that existence of the angular acceleration makes a spinning disk dynamically unstable.

Stability Analysis of a Rotating Cantilever Pipe Conveying Fluid (유체유동 회전 외팔 파이프의 안정성 해석)

  • Son, In-Soo;Yoon, Han-Ik;Kim, Dong-Jin
    • Transactions of the Korean Society for Noise and Vibration Engineering
    • /
    • v.17 no.8
    • /
    • pp.701-707
    • /
    • 2007
  • In this paper the vibration system is composed of a rotating cantilever pipe conveying fluid. The equation of motion is derived by using the Lagrange's equation. Generally, the system of pipe conveying fluid becomes unstable by flutter. Therefore, the influence of the rotating angular velocity, mass ratio and the velocity of fluid flow on the stability of a cantilever pipe by the numerical method are studied. The influence of mass ratio, the velocity of fluid, the angular velocity of a cantilever pipe and the coupling of these factors on the stability of a cantilever pipe are analytically clarified. The critical fluid velocity ($u_{cr}$) is proportional to the angular velocity of the cantilever pipe. In this paper Flutter(instability) is always occurred in the second mode of the system.

Clinical Significance of Radiological Stability in Reconstructed Thoracic and Lumbar Spine Following Vertebral Body Resection

  • Sung, Sang-Hyun;Chang, Ung-Kyu
    • Journal of Korean Neurosurgical Society
    • /
    • v.56 no.4
    • /
    • pp.323-329
    • /
    • 2014
  • Objective : Vertebral body replacement following corpectomy in thoracic or lumbar spine is performed with titanium mesh cage (TMC) containing any grafts. Radiological changes often occur on follow-up. This study investigated the relationship between the radiological stability and clinical symptoms. Methods : The subjects of this study were 28 patients who underwent corpectomy on the thoracic or lumbar spine. Their medical records and radiological data were retrospectively analyzed. There were 23 cases of tumor, 2 cases of trauma, and 3 cases of infection. During operation, spinal reconstruction was done with TMC and additional screw fixation. We measured TMC settlement in sagittal plane and spinal angular change in coronal and sagittal plane at postoperative one month and last follow-up. Pain score was also checked. We investigated the correlation between radiologic change and pain status. Whether factors, such as the kind of graft material, surgical approach, and fusion can affect the radiological stability or not was analyzed as well. Results : Mean follow-up was 23.6 months. During follow-up, $2.08{\pm}1.65^{\circ}$ and $6.96{\pm}2.08^{\circ}$ of angular change was observed in coronal and sagittal plane, respectively. A mean of cage settlement was $4.02{\pm}2.83mm$. Pain aggravation was observed in 4 cases. However, no significant relationship was found between spinal angular change and pain status (p=0.518, 0.458). Cage settlement was seen not to be related with pain status, either (p=0.644). No factors were found to affect the radiological stability. Conclusion : TMC settlement and spinal angular change were often observed in reconstructed spine. However, these changes did not always cause postoperative axial pain.

Permanent Magnet Synchronous Motor Control Algorithm Based on Stability Margin and Lyapunov Stability Analysis

  • Jie, Hongyu;Xu, Hongbing;Zheng, Yanbing;Xin, Xiaoshuai;Zheng, Gang
    • Journal of Power Electronics
    • /
    • v.19 no.6
    • /
    • pp.1505-1514
    • /
    • 2019
  • The permanent magnet synchronous motor (PMSM) is widely used in various fields and the proportional-integral (PI) controller is popular in PMSM control systems. However, the motor parameters are usually unknown, which can lead to a complicated PI controller design and poor performance. In order to design a PI controller with good performance when the motor parameters are unknown, a control algorithm based on stability margin is proposed in this paper. First of all, based on the mathematical model of the PMSM and the least squares (LS) method, motor parameters are estimated offline. Then based on the estimation values of the motor parameters, natural angular frequency and phase margin, a PI controller is designed. Performance indices including the natural angular frequency and the phase margin are used directly to design the PI controller in this paper. Scalar functions of the d-loop and the q-loop are selected. It can be seen that the designed controller parameters satisfy Lyapunov large scale asymptotic stability theory if the natural angular frequencies of the d-loop and the q-loop are large than 0. Experimental results show that the parameter estimation method has good accuracy and the designed PI controller proposed in this paper has good static and dynamic performances.

Dynamic Characteristics and Stability Analysis of a Rotating Cantilever Pipe Conveying Fluid (유체유동 회전 외팔 파이프의 동특성 및 안정성 해석)

  • Kim, Dong-Jin;Yoon, Han-Ik;Son, In-Soo
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
    • /
    • /
    • pp.1185-1190
    • /
    • 2007
  • In this paper the vibration system is consisted of a rotating cantilever pipe conveying fluid. The equation of motion is derived by using the Lagrange's equation. Also, the equation of motion is derived applying a modeling method that employs hybrid deformation variables. Generally, the system of pipe conveying fluid becomes unstable by flutter. So, we studied about the influences of the rotating angular velocity, mass ratio and the velocity of fluid flow on the stability of a cantilever pipe by the numerical method. The influences of mass ratio, the velocity of fluid, the angular velocity of a cantilever pipe and the coupling of these factors on the stability of a cantilever pipe are analytically clarified. The critical fluid velocity$(u_{cr})$ is proportional to the angular velocity of the cantilever pipe. In this paper Flutter(instability) always occur in the second mode of the system.

  • PDF

Dynamic Stability of Rotating Cantilever Pipe Conveying Fluid with Tip mass and Crack (끝단질량과 크랙을 가진 유체유동 회전 외팔 파이프의 동적 안정성)

  • Son, In-Soo;Yoon, Han-Ik;Kim, Dong-Jin
    • Transactions of the Korean Society for Noise and Vibration Engineering
    • /
    • v.18 no.1
    • /
    • pp.101-109
    • /
    • 2008
  • The stability of a rotating cantilever pipe conveying fluid with a crack and tip mass is investigated by the numerical method. That is, the effects of the rotating angular velocity, mass ratio, crack severity and tip mass on the critical flow velocity for flutter instability of system are studied. The equations of motion of rotating pipe are derived by using the Euler-Bernoulli beam theory and the extended Hamilton's principle. The crack section of pipe is represented by a local flexibility matrix connecting two undamaged pipe segments. Also, the crack is assumed to be in the first mode of fracture and always opened during the vibrations. When the tip mass and crack are constant, the critical flow velocity for flutter is proportional to the rotating angular velocity of pipe. In addition, the stability maps of the rotating pipe system as a rotating angular velocity and mass ratio ${\beta}$ are presented.

Stability Analysis of Cracked cantilever beam Subjected to Follower force (유체유동 회전 외팔파이프의 안정성에 미치는 끝단질량의 영향)

  • Yoon, Han-Ik;Son, In-Soo;Kin, Dong-Jin
    • Proceedings of the Computational Structural Engineering Institute Conference
    • /
    • /
    • pp.121-126
    • /
    • 2007
  • In this paper the vibration system is consisted of a rotating cantilever pipe conveying fluid and a tip mass. The equation of motion is derived applying a modeling method that employs hybrid deformation variables. 'TI1e influences of the rotating angular velocity, mass ratio and the velocity of fluid flow on the stability of a cantilever pipe are studied by the numerical method. The effect of tip mass on the stability of a rotating cantilever pipe are also studied. The influences of a tip mass, the velocity of fluid the angular velocity of a cantilever pipe and the coupling of these factors on the stability of a cantilever pipe are analytically clarified.

  • PDF

Stability of Rotating Cantilever Pipe Conveying Fluid with Crack (크랙을 가진 유체유동 회전 외팔 파이프의 안정성 해석)

  • Kim, Dong-Jin;Yoon, Han-Ik;Son, In-Soo
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
    • /
    • /
    • pp.356-359
    • /
    • 2007
  • In this paper, the stability of a rotating cantilever pipe conveying fluid with a crack is investigated by the numerical method. That is, the influences of the rotating angular velocity, mass ratio and crack severity on the critical flow velocity for flutter instability of system are studied. The equations of motion of rotating pipe are derived using the Euler beam theory and the Lagrange's equation. The crack section of pipe is represented by a local flexibility matrix connecting two undamaged pipe segments. The crack is assumed to be in the first mode of fracture and to be always opened during the vibrations. Generally, the critical flow velocity for flutter is proportional to the angular velocity and the depth of crack. Also, the critical flow velocity and stability maps of the rotating pipe system as a function of mass ratio for the changing each parameter are obtained.

  • PDF

A Study for Controllability, Stability by Optimal Control of Load and Angular Velocity of Flying Objects using the Spiral Predictive Model(SPM) (나선 예측 모델에서의 비행체 하중수 및 각속도 최적 제어에 의한 제어성과 안정성 성능에 관한 연구)

  • Wang, Hyun-Min
    • Journal of Institute of Control, Robotics and Systems
    • /
    • v.13 no.3
    • /
    • pp.268-272
    • /
    • 2007
  • These days many scientists make studies of feedback control system for stability on non-linear state and for the maneuver of flying objects. These feedback control systems have to satisfy trajectory condition and angular conditions, that is to say, controllability and stability simultaneously to achieve mission. In this paper, a design methods using model based control system which consists of spiral predictive model, Q-function included into generalized-work function is shown. It is made a clear that the proposed algorithm using SPM maneuvers for controllability and stability at the same time is successful in attaining our purpose. The feature of the proposed algorithm is illustrated by simulation results. As a conclusion, the proposed algorithm is useful for the control of moving objects.

Influence of Tip Mass on Stability of a Rotating Cantilever Pipe Conveying Fluid (유체유동 회전 외팔 파이프의 안정성에 미치는 끝단질량의 영향)

  • Son, In-Soo;Yoon, Han-Ik;Kim, Dong-Jin
    • Transactions of the Korean Society for Noise and Vibration Engineering
    • /
    • v.17 no.10
    • /
    • pp.976-982
    • /
    • 2007
  • In this paper the vibration system is consisted of a rotating cantilever pipe conveying fluid and tip mass. The equation of motion is derived by using the Lagrange's equation. The system of pipe conveying fluid becomes unstable by flutter. Therefore, the influence of a rotating angular velocity, mass ratio, the velocity of fluid flow and tip mass on the stability of a cantilever pipe by the numerical method are studied. The critical flow velocity for flutter is proportional to the angular velocity and tip mass of the cantilever pipe. Also, the critical flow velocity and stability maps of the pipe system are obtained by changing the mass ratios.