Taro Shimogo

Application of the impulse index in rolling-element bearing fault diagnosis

Abstract An application of the Haar transform to mechanical vibration signature analysis has been presented previously. The average power intensity compressed in each equivalent sequency group of the Haar transformed data is extracted as the characteristic parameter named the impulse index which enables high-speed real-time processing and fast on-line fault detection. In this paper, experimental data of both good and damaged bearings are processed to show that effectiveness of the fault diagnosis using this type of parameter. Our results show that the impulse index compares favorably with the Fourier power spectrum in extracting useful fault information from vibration signals.

New indices in the sequency domain and their application to condition monitoring of mechanical systems

Abstract In this paper, some new indices in the sequency domain are defined describing the vibroacoustical process of machinery based on the fast Walsh transform. The Rice frequency is a useful index for detecting the change of power spectral components but it cannot be obtained easily and quickly. Here we define four indices in the sequency domain. Two of them are dimensional in nature and express the central sequency number and the rms sequency number and two are, dimensionless factors showing the dispersion and kurotsis of the spectral distribution. Computer simulation results for non-linear systems with different parameters are presented and shown to be effective in detecting changes in power spectral components.

Active Control of Shock

In this paper we deal with active control of shock in a collision problem between two objects. In order to make it clear how the deformation of the shock-receiving object can be maximized while minimizing the deformation of the shock-giving object and how energy can be transmitted unilaterally, the relationships among contact stiffness, deformation time, deformation ratio and energy balance are discussed. The final-state control is applied to obtain a feedforward input to deform the shock-receiving object by a desired amount in a predetermined time. Thus, the energy balance and the energy efficiency are verified. Furthermore we examine the conditions necessary to realize a ‘dynamical diode’ that can transmit energy unilaterally from the shock-giving object to the shock-receiving object. It is demonstrated experimentally that the appropriate feedforward input can be obtained by final-state control under specified conditions of contact stiffness and deformation time.Copyright

Research on Reduced-Order Active Vibration Control for High-Rise Buildings.

This parer considers the robustness against spillover in the reduced-order control system of an active dynamic vibration absorber for high-rise buildings by computational and experimental research. Three methods are investigated: a LQ control using a reduced-order model, a spillover-considered suboptimal control and a spillover-considered suboptimal control using a low-pass filter. In the numerical calculations, it is shown that the control obtained from the displacement criterion possesses the stability limit in the control performance due to the spillover, and the highest performance is achieved by the spillover-considered suboptimal control using a low-pass filter. The optimal threshold frequency of the filter is also discussed. On the other hand, there is little spillover in the suboptimal control from the velocity criterion.

State Discrimination of Vibration Systems Using Pattern Recognition Technique

In this paper, the application of pattern recognition to the state discrimination of vibration systems is presented. Here, two kinds of nonlinear models are used for the recognition of nonlinearity. Procedures for the form of pattern vectors, and measurements of the distances between various patterns are illustrated. The feature parameter which is decisive for the discrimination is extracted based on the principal component analysis. Finally, the effectiveness of the discrimination is evaluated.

Electromagnetic levitation control of a traveling steel belt.

A method of magnetic levitation control of a traveling steel belt is presented. A traveling steel belt is supported in contactless manner by attractive forces of electromagnetic actuators which are controlled by feedback signals from gap sensors to stabilize the levitation behavior. A sub-optimal control theory is applied to minimize effects of spillover of residual vibration modes of the belt. To verify the usefulness of the method, an experiment of digital control was performed using a SUS430 steel belt.

Experimental modal analysis of a multi-degree-of-freedom system with random parametric excitation and non-linear damping

Abstract Though there are many non-linear systems in use, the experimental modal analysis techniques are based on the linear system. In this paper, an experimental modal analysis technique for a multi-degree-of-freedom system with random parametric excitation and non-linear damping being proportional to the squared velocity is proposed. This technique is developed from examining a stability condition for the covariance of response given by applying the perturbation technique to a stochastic differential equation, which is derived by the mode decoupling, the statistical linearization and other assumptions. Additionally, experiments were carried out to identify the modal parameters with the aid of the proposed technique, the technique was confirmed with analytical solutions.

A power collector with a control mechanism of contact force.

A power collector is presented, which has a control mechanism of contact force between a contactor of the power collector and a contact wire. By applying the optimal control theory, the optimal control laws with a feedforward link of wire unevenness are derived for two cases of sliding on a rigid contact wire and an elastic contact wire which is simply modeled as an infinite beam in this study. The feasibility of the power collector is considered by performing numerical calculations and an experiment. As a result, it was made clear that the optimal state feedback control of the power collector is useful for the case of a rigid wire, but not useful for the case of an elastic wire. In other words, in the case of the elastic wire, the feedforward control of disturbance is indispensable and the detection or the estimation of wire unevenness is an important technical subject.

OPTIMAL CONTROL OF RANDOM VIBRATION BY THE USE OF AN ACTIVE DYNAMIC VIBRATION ABSORBER (EXPERIMENTAL CONSIDERATIONS ON THE EFFECT OF THE CONTROL WITH FEEDFORWARD LINK).

For the vibration control of a main structure subjected to a random input with a dominant frequency, an active dynamic vibration absorber is manufactured, which is equipped with a linear motor as an actuator and is digitally controlled by means of optimal feedback and feedforward links. First, by performing impulse excitation, the usefulness of the optimal feedback control is verified. Second, in the frequency responses obtained from a stationary random excitation, the effectiveness of the optimal feedforward link is demonstrated in comparison with a feedback link only. Further, in a nonstationary random excitation in which the same nonstationary random wave can be realized every time, it is confirmed that the active dynamic vibration absorber is useful also for nonstationary random input.

Tube sinking behaviors caused by natural water filling.

本論文では,海洋において長大なライザー管を自然注水により設置する場合の管の沈下挙動について解析し,模型実験により理論の妥当性を確認した.その結果,取水口,排気口の径,管の長さ,管径,および,管内断面積が,管の沈下に要する時間,および,最大曲げモーメントに与える影響が明らかにされた.さらに,最大曲げモーメントを小さく抑える方法を考察した.