Optimal Controller and Filter Realisations using Finite-precision, Floating- point Arithmetic.

The problem of reducing the fragility of digital controllers and filters implemented using finite-precision, floating-point arithmetic is considered. Floating-point arithmetic parameter uncertainty is multiplicative, unlike parameter uncertainty resulting from fixed-point arithmetic. Based on first- order eigenvalue sensitivity analysis, an upper bound on the eigenvalue perturbations is derived. Consequently, open-loop and closed-loop eigenvalue sensitivity measures are proposed. These measures are dependent upon the filter/ controller realization. Problems of obtaining the optimal realization with respect to both the open-loop and the closed-loop eigenvalue sensitivity measures are posed. The problem for the open-loop case is completely solved. Solutions for the closed-loop case are obtained using non-linear programming. The problems are illustrated with a numerical example

Determination of dynamic flexure model parameters for ship angular deformation measurement

In ship angular deformation measurement, Kalman filter used to estimate the deformation angle requires accurate dynamic flexure parameters. Traditionally, these dynamic flexure parameters are empirically set according to previous experience or determined from previously collected experimental data. Inevitably, the Kalman filter will perform poorly when the current application environment is differ with those used in the filter design. To overcome this problem, we propose an alternative on-line approach to estimate the dynamic flexure parameters based on the attitude difference measured by two laser gyro units. Specifically, the Tufts-Kumaresan (T-K) method is introduced to solve the unknown parameters of the dynamic flexure model from the computed attitude difference. Simulation results show that the proposed method can estimate the dynamic flexure parameters in real-time with a high degree of accuracy even in serious noise polluted conditions. A further advantage of the proposed approach is that it does not require a priori knowledge of the dynamic flexure characteristics

Effect of near-fault ground motions with long-period pulses on the tunnel

Investigations from recent strong earthquakes indicate most of the tunnels severely damaged are located near the causative faults. First, the dynamic response of the tunnel to the near-fault and far-field ground motions was investigated. The results show that the near-fault motions with long-period pulses especially the forward directivity pulses are more damaging than the typical far-field records, which should be reflected in the seismic design guideline for tunnels near causative faults. Furthermore, the effects of the key parameters for the simplified pulse on the dynamic response of the tunnel were also studied. Generally, the pulse with larger amplitude brings more energy and leads to larger strains in rock. Consequently, it becomes more damaging to the tunnel. The period of the pulse can remarkably influence the response of the tunnel. When the period of the pulse is less than 3.0 s, the pulse becomes less damaging to the tunnel with the increase of the period. Once the period exceeds 3.0 s, the pulse has little effect on the dynamic response of the tunnel. Thus, the earthquake with lower magnitude, which is likely to leads to lower period, may be more damaging to the tunnel. Besides, as the number of significant cycles increases, the damage potential of the ground motions increases accordingly. For the sake of security, two significant cycles in velocity-time history are recommended for the seismic design of tunnels close to ruptured faults