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A fault pattern recognition method was developed on the basis of information entropy and bispectrum theory. The bispectrum features of vibration signal were analyzed. And a bispectrum entropy algorithm based on energy distribution was derived under the condition of subspace distribution probability. Then, the vibration signals of a gearbox under four conditions were extracted experimentally. And a BP neural network for the fault pattern recognition was established by using the bispeetrum entropy feature as input. Finally, this method was verified by successfully recognizing four fault patterns of the gearbox. [ABSTRACT FROM AUTHOR]

In order to improve the calibration precision of 6DOF parallel mechanism, a calibration method based on external coordinate measurement is presented. The position and attitude informations of the parallel mechanism are acquired using common measuring devices and the residual equations with uniform measure are constructed. These equations can ensure the identifiability of each geometry parameter's, so no special auxiliary calibration equipments or redundant sensors are required. From the residual equations, the estimated values of geometry parameters are obtained by optimization method, and the ideal parameters are replaced by them for the parallel mechanism inverse kinematics calculation of to realize the error compensation. The simulation results show that this method can decrease the effect of measure noise, and the kinematics accuracy after calibration can reach the same order of magnitude as measurement noise since the errors of parallel mechanism's are not usually cumulated. The calibration accuracy is improved more than 5 times after error compensation by using the method. [ABSTRACT FROM AUTHOR]

Rotary jitter compensation is a difficulty in video image stabilization. The feature point matching and inaccurate point filtering were studied. An affine model with 6 parameters was established for moving images, and an over-determined equation to estimate motion parameters was derived. The least squares iterative algorithm was used to remove error feature points judged by sum of absolute difference (SAD) matching algorithm. A pyramid-style Lucas-Kanade (LK) algorithm based on optical flow was adopted for feature point matching of rotary video. All algorithms were programmed. After detecting feature points by using the gradient matrix of the feature window (KLT) method, SAD and LK algorithms were used to match feature points respectively, and the rotation matrix parameter errors were obtained and compared. The reasons of matching error were analyzed. Kalman filter was used to smooth rotation parameters. All algorithms were implemented on an autonomous robot. The experiment results show that LK can get less matching errors than SAD for rotation jitter, and Kalman filter makes the maximum 8. 37° rotation jitter less than 3.68°, thus it can compensate the rotary video effectively. [ABSTRACT FROM AUTHOR]

Aiming at load simulating problem of the thrust vector control (TVC) system in launch vehicles, a new load simulator structure and its mathematical model are presented. The influence of main parameters on system's dynamic performance is analyzed by simulation. Building a prototype experiment system, multiple DOF load property is showed in a sweep frequency test. Simulation and experiment verify the feasibility of this load simulator structure, which lay a foundation for optimizing design parameters of the thrust vector servo mechanism and developing load simulators of heavy launch vehicles' servo systems. [ABSTRACT FROM AUTHOR]