The head-neck complex (HNC) responses to the trunk horizontal (fore and aft) vibration in the seated human body were studied. It was assumed that the HNC has only rotational motion in mid-sagittal plane. An experimental method was designed to generate the trunk horizontal vibration, and to measure the input and output signals to the system. The subjects were exposed to the random vibration at a magnitude of 1.60(ms)^<-2> rms (root-mean-square) for 50 seconds. The coherence and frequency response function were then obtained on 0.5 Hz to 10 Hz. The results manifested that the HNC behavior was quasi-linear with a dominant resonance frequency nearly between 1 Hz and 1.4 Hz. Accordingly, a two-dimensional single-inverted-pendulum was considered as a model for the HNC. Frequency domain identification method was then used to estimate the unknown parameters, including the HNC viscoelastic and inertia parameters. in the low Frequency range (<3HZ). The model was examined in the time domain using both random and sinusoidal vibration. Good agreement was obtained between experimental and simulation results.

View full abstract

Force and torque induced by motions of a mobile manipulator effect dynamically to the objects being carried on it. If the induced force is bigger than the static friction force, the carrying objects start slipping motion in the mobile manipulator. As the result, the movement of one carrying object may cause a collapse of all carrying objects, since a start of slipping makes the acceleration of mobile robot increase, furthermore it interferes with accurate traveling operations and moreover it is dangerous. In this paper, we propose a model of n-link mobile manipulator including the slipping motion of plural carrying objects.

View full abstract

The Learning Vector Quantization (LVQ) neural network is applied to the defect identification problem for structures, which is important when constructing the mathematical model of structures. In this study the eigenmodes of a plate obtained from FEM and the location of a defect contained in that plate are used as the training deta for neural network and the position of the defect is identified by giving the unlearned input data to the trained network. As a result the better accuracy is obtained compared to the case when using the backpropagation neural network commonly used in the various studies

View full abstract

In this paper, new system identification methods for flexible structures described by fractional differential equations are proposed. Several high-rise buildings have been controlled to reduce the vibration due to winds and earthquakes. In order to control the vibration of such structures, viscoelastic dampers have been installed. Fractional differential equations systems are suitable to make precise dynamical model of the structures with the viscoelastic dampers. There are some difficulties to have a suitable model. Here, we propose the identification methods for the fractional differential equations systems by using FIR-type filter and ARMA-type filter.

View full abstract

We propose a damage identification algorithm for story stiffness and damping factor that can be direct damage indices. The modal properties obtained by subspace identification (4SID) are utilized to derive the damage indices. The proposed algorithm is basically applicable to shear structures. In this study, a seismic isolated structure was chosen as the monitoring target. Of a seismic isolated structure, the isolation layer and superstructure are treated as separate substructures as they are distinctly different in their dynamic properties. Based on this substructure approach, damage evaluation is separately conducted for each substructure. Effectiveness of the proposed method is verified through the simulation and the experiment.

View full abstract

A semi-active stiffness damper has been shown to be effective in reducing structural responses against earthquake forces. This system uses a MR (magnetorheological) damper as a control device connected to the bracing frame. In order to take advantage of MR damper, a model must be developed to characterize the damper's nonlinear behavior. An experimental test has been conducted to obtain the data necessary for modelling MR damper through parametric identification. Simple and modified Bouc-Wen models are considered for modelling hysteretic systems. The response analysis results show that both models are effective in predicting the response of the MR damper.

View full abstract

In this paper, the contact force between impacting bodies is modeled by using Hertz force displacement law and linear or nonlinear damping function. For the exact impact analysis, the dynamics of the sensor attached to the impacting body is considered. In order to verify the appropriateness of the proposed contact force model, the drop type impact test is carried out. Through numerical analysis and experiment, the influence of sensor dynamics and the characteristics of contact force model are investigated.

View full abstract