| Linear variable differential transformer (LVDT) is one of electromechanical sensorwhich has high stability and accuracy. Owes to its superior performances, LVDT has alreadybeen widely used in aeronautic and aerospace field. It must be offered sine wave excitationsignal by external devices in LVDT s production testing and working time. However, thetraditional signal generators have the shortcomings about low output voltage, week loadcapacity. Not only that, they can t steady voltage and frequency. These drawbacks havegreatly reduced LVDT s working performance. In this topic, a realization scheme for highstability and accuracy sine wave excitation signal generator, which outputs voltage RMS at40V and load current at2A was presented, and offers sine wave excitation signal to LVDT.The main contributions of this paper are:(1) According to the characteristics of a linear system, we combine a principle of leastsquares fitting to fit open loop curve and closed loop curve. These open loop curves andclosed loop curves are used for open loop control and closed loop control.(2) Using ALTERA FPGA and ARM Cortex-M3as the cores for cortrolling the systemsignals is proposed. The design of DDS with FPGA is adopt, and we use this DDS to outputsine wave excitation signal combine to a12bit DAC named AD5445. Using Cortex-M3toachieve the controlling of power amplifier, closed feedback circuit, and man-computerinteraction. It shows that the scheme is feasible.(3) We had use two different cores in the system, the same as their development tools aredissimilar. In FPGA system, we choose to use hardware description language Verilog HDL,but we use embedded C language in Cortex-M3. we use the development tools which calledQuartus II and Modelsim to realize the communication with Cortex-M3and the design ofDDS in FPGA project. What s more, we use the development tool which called Keil uVision4 to achieve the controlling of system signals and the software realization of algorithm. |
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