High-speed cam mechanism is widely used in vehicles, textile machinery, printing machinery etc. The research of dynamic analysis is the basis and key point to improve the mechanical properties. Discretization of the flexible elements of cam mechanism is carried out by means of finite-element method. Furthermore, the dynamic model of the rigid-flexible coupled cam mechanism is proposed based on modal synthesis technique and Kane’s equations. The dynamic equation obtained is more general for flexible beam type, and very convenient for solving by computer because it is a modal-coordinates dynamic equation. The system dynamic performance is studied by analyzing the system modal and solving the dynamic equation. The simulation of dynamics model which has different orders is carried on, which can not only ensure accuracy of calculation but also save computational resources. Research results have important guiding significance for determining whether the dynamic analysis of high-speed cam systems in practical application is required, and furthermore, research results can provide strong guide for dynamic modeling and modal characteristics research of similar mechanism.

Acoustical guided waves modal analysis in rail is the basis of long distance guided wave inspection and rail vibration and noises control. In particular the various propagating guided waves in the rail are identified in terms of their propagation wavenumber coefficients and their corresponding deformed shapes. The semi-analytical finite element method is used to formulate the governing equation for guided waves propagating in elastic waveguides of arbitrary cross-section on the basis of the virtual work principle, wavenumber dispersion curves and deformed shapes are extracted by solving governing equation, which provide the basis for selecting mode and frequency during application. The propagating guided waves wavenumber dispersion curves and deformed shaped under 0-8 kHz frequency range for CHN60 type free rail are obtained using semi-analytical finite element method, and the characteristics of the eight based guided waves mode in rail are discussed. Instrumented hammer experimental study and modal analysis using sever vibration accelerometers mounted on rail are carried out to verify the vertically vibrating mode and horizontally vibrating mode guided waves wavenumber dispersion coefficient. Modeling and experimental investigations of lateral and vertical excitation in railhead shows that good agreement between numerical calculation and experiment.

Robotics in medical have made giant strides in past several decades with its widely use in various aspects. According to it’s function and usage, medical robots are classified into 7 types: neurosurgery robot, orthopedics robot, laparoscopic robot, vascular interventional robot, prosthetics and exoskeleton robot, assistive and rehabilitation robot and capsule robot. The functions, specifications, advantages and disadvantages of present typical commercially available medical robotics are surveyed. The current research foci, key technology and future trends of medical robotics are also discussed.

Drill pipe is a critical and vulnerable component in oil & gas industry. A novel feed-through alternating current field measurement (ACFM) is proposed to achieve in-service detection for axial cracks on the surface of drill pipe. The finite element model is built by ANSYS software for analyzing the induced electromagnetic field distribution and disturbance caused by the axial crack on the external surface of drill pipe. Signal features of the crack are extracted through quantitatively analyzing the relationship between the size of crack and disturbance field. On the basis of theory and FEM simulation, the feed-through ACFM system is set up and proved by the axial crack of drill pipe detection experiments. The results show that, the signal features of Bx and Bz from the feed-through ACFM system show the depth and length information of the axial crack respectively on pipe string, and the lift-off effect can meet the demands of in-service detection for drill pipe. Furthermore, the feed-through ACFM system with sensors array can detect all the axial cracks in-service with a single pass scanning.

Since the concept of compliant mechanisms (CMs) is firstly proposed in late 1980s, it develops rapidly and has become an important branch of modern mechanism community. In the past less than 30 years, dozens of design methodologies and theories for CMs have emerged, which lays a solid foundation on their successful use. With the increasing insight for flexures and CMs, more and more applications of CMs can be found in various fields. After summarizing and comparing the current design methods for flexure-based compliant mechanisms five years ago, the state-of-arts of CMs have been overviewed from the point of application in this paper. Most existing CMs are resorted to three categories, i.e. precision engineering, bionic robotics, and smart structures if considering the difference of their functions and application background. The successful uses, study focuses and even application prospects in each category of CMs are introduced case by case. Afterward, four new types of CMs with great potential applications, i.e. cellular CMs, contact aid CMs, lamina emergent mechanisms, and static balance CMs are illustrated in brief. We hope more scholars all over the world start to study these amazing CMs and industrial personnel pay more attention on the usage of CMs as well after getting the overview of CMs.

In order to extract machinery fault characteristics that are submerged in strong background noise, a general singular value decomposition (SVD) based subspace noise reduction algorithm is applied to signal processing, i.e., μ-SVD based denoising method. It can be proved that the traditional SVD based denoising method is a special case of the μ-SVD based one where μ=0. μ-SVD based denoising method contains a filter factor that plays a role in restraining information contributions of the noise-domain singular values to the denoised signal. μ-SVD based denoising method involves five parameters, including delay time, embedding dimension, noise reduction order, noise power and Lagrange multiplier. The selection methods for these parameters are discussed. In particular, the effects of noise reduction order and Lagrange multiplier on denoising performance are also studied. The experimental results of simulation signal with local fault and vibration signal with early crack fault in gear demonstrate that the μ-SVD based denoising method is superior to the traditional one in denoising performance, and can more effectively extract the gear fault characteristics at the presence of strong background noise.

The major parameter estimation error source for discrete Fourier transform are spectrum leakage and picket fence effect. A weighted two points vector interpolation algorithm based on Rife-Vincent window for improving the estimation accuracy of parameters for the multi-frequency damped signals is presented, where the signals are weighted by M-order cosine window family before the discrete Fourier transform and the equations with nuknown of frequency deviation and decay factor is established by the ration of two adjacent spectral lines near the real frequency position. The frequencies, amplitudes and phases are calculated by the frequency deviation solved from the above equation. The cosine window family with the characteristic of maximum sidelobe decay can essentially remove the spectral leakage and two point vector interpolation will cope with the problem of the picket fence. To combine the merits of the above two method can effectively increase the accuracy. The simulation and test results show that the proposed algorithm has a higher estimate accuracy and steady estimates. The higher computational efficiency and lower memory demand are suggested especially for poor computing resource situations. It also can be used as an optional method for the features extraction of the multi-frequency damped signals.