For the problems of noise and clutter interference in the measurement of grounding resistance, the article designs a grounding resistance measurement method based on an improved FFT algorithm. We deduce the harmonic amplitude correction formula which can more accurately measure the frequency of the interference signals and the amplitude of the effective signals, and thus improve the measurement accuracy of grounding resistance. This paper also devises a grounding resistance measurement scheme combining the algorithm and the variation-frequency method. The simulation results and the validation of experimental data show that, the algorithm evidently reduces the noise and improves the measurement precision. The algorithm is of high practical value to the grounding resistance measurement.

Aimed at the problem of speed identification for the asynthetic motor speed-less sensor vector control system, based on basic equations of vector control and centered by the current model and voltage model of rotor flux linkage, after the establishment of the rotor speed identification module by module reference self-adaptation theory (MRAS), this paper builds the MRAS speed-less sensor vector control system and establishes the system simulation model in Simulink software environment. Simulation results show that: the system has good dynamic and static characteristics and stability. Key words: speed-less sensor; vector control; MRAS; simulation CLC: TM343.2 Document Code:A

The vehicle terminal is part of the vehicle monitoring system, this article introduces ARM 9 and Bei Dou navigation and communication system which consisting of vehicle terminal system, which offers a method not only could combines Bei Dou communication, GPRS communication, Ethernet communication but also provides the multi-channel data acquisition, this method could ensure that the information transmission in the abnormal situations, and also could give full play to a variety of channels, use of resources, improve efficiency, reduce communication costs, and has great application prospects.