Novel Real-Time Seam Tracking Algorithm Based on Vector Angle and Least Square Method

Real-time seam tracking can improve welding quality and enhance welding efficiency during the welding process in automobile manufacturing.However,the teaching-playing welding process,an off-line seam tracking method,is still dominant in automobile industry,which is less flexible when welding objects or situation change.A novel real-time algorithm consisting of seam detection and generation is proposed to track seam.Using captured 3D points,space vectors were created between two adjacent points along each laser line and then a vector angle based algorithm was developed to detect target points on the seam.Least square method was used to fit target points to a welding trajectory for seam tracking.Furthermore,the real-time seam tracking process was simulated in MATLAB/Simulink.The trend of joint angles vs.time was logged and a comparison between the off-line and the proposed seam tracking algorithm was conducted.Results show that the proposed real-time seam tracking algorithm can work in a real-time scenario and have high accuracy in welding point positioning.

Designing price-contingent vegetable rotation schedules using agent-based simulation

Chinese vegetable production cooperatives supply their members, mostly smallholder farmers, with a rotation schedule for the year. Since vegetable prices are not stable throughout the year, designing a rotation schedule that maximizes expected profits, distributes farmers＇ profits more equitably, maintains the diversity of produce in the market, and reduces the risk of pests and diseases, requires adaptive, price-contingent rotation schedules（here, called ＂self-adaptive adjustment＂）. This study uses an agent-based simulation（ABS） to design self-adaptive rotation schedules that deliver these aims. The selfadaptive adjustment strategy was more profitable for farmers when faced with price volatility, and more equitable as well. This work provides a decision-support tool for managers of Chinese vegetable production cooperatives to provide farmers with more profitable and equitable rotation schedules.

Narrowband speech wideband extension algorithm research

To reduce the spectral distortion,a Hidden Markov Model-based narrowband speech bandwidth extension algorithm is presented.Firstly,the parameters which have higher mutual information with wideband envelope were extracted to constitute the feature vector,and then a posterior probability was calculated via the joint probability of the partial observation feature vector sequence and the markov states.Secondly,based on the posterior probability,the wideband envelope was estimated using Bayesian parameter estimation method and minimum mean square error criteria.For estimation of wideband excitation signal,intermediate frequency extension algorithm is proposed based on the harmonic correlation between the low frequency and high frequency.The experimental results show that,compared with the traditional bandwidth extension algorithm based on Hidden Markov Model,the average spectral distortion is reduced by 0.187 dB and the number of speech frame with spectral distortion over10dB is decreased by 34.3%.

Research on algorithms for ultrasonic reflection mode tomography

In this paper, mathematical analysis shows that the reconstruction of ultrasonic reflection mode tomography using a single transducer acting as both source and receiver far from the object can be obtained by employing filtered-backprojection algorithm which is widely used in X-ray tomography; but when the transducer is near to the object, this algorithm will result in image distortion. On the basis of mathematical analysis, we propose a new algorithm. Computer simulation demonstrates an obvious improvement in the reconstructed images employing this algorithm over the conventional filtered-backprojection method of X-ray tomography.

Research and Implementation of the Practical Texture Synthesis Algorithms

How to generate pictures real and esthetic objects is an important subject of computer graphics. The techniques of mapping textures onto the surfaces of an object in the 3D space are efficient ap- proaches for the purpose.We developed and implemented algorithms for generating objects with appear ances stone,wood grain,ice lattice,brick,doors and windows on Apollo workstations. All the algorithms have been incorporated into the 3D geometry modelling system(GEMS)developed by the CAD Center of Tsinghua University.This paper emphasizes the wood grain and the ice lattice algorithms.