Design Of Portable External System Equivalent Device

In this paper,an external system equivalent device is designed for the rocket borne test and measurement system.The onboard measurement system can monitor the various states and parameters of the aircraft,and the external system equivalent device can provide the required analog signal,digital signal and serial bus signal under the command of the computer.Assisting to complete the closed-loop test in the research and development stage,and improve its reliability,which has practical engineering significance.External system equivalent device is a kind of automatic test equipment.Based on the analysis of design requirements,this paper proposes a portable external system equivalent based on CPCI standard bus.On the basis of meeting the requirements of the rocket borne test and measurement system,the software and hardware structure of the whole system is designed by using the design principles of standardization,modularization and generalization.Writing the logic writing of the modules,and the test software is designed in the main controller to carry out simulation and verification experiments.The hardware platform adopts the CPCI bus system structure.The equipment cabinet,computer case,embedded controller and RS485 serial port communication function module are selected from standard shelf products.Complete the hardware design of digital switch excitation module,1553 B bus special signal source module,RS422 bus signal analog module,28 V special signal source module,LVDS bus signal module and DAC analog voltage output module.FPGA is selected as the control chip on the peripheral board of CPCI.Because the external system equivalent needs to output a variety of signals,when designing the board circuit,it needs to meet the transmission requirements of differential signal,high-speed signal and electrical isolation.According to the portability requirements of the external system device,a special design is carried out to reduce the hardware volume.Ensuring that the peripheral module of the external system device directly outputs the required signals,and integrate the conditioning circuit to the maximum extent.On the Lab Windows/CVI platform,a driver and a soft panel interface are developed for the hardware board,which can assist in troubleshooting the external system equivalent device.Developing the instrument driver function based on the open source NI-VISA function library,for the second development consideration,the friendly human-computer interface is designed,which is convenient to send parameters and instructions to the CPCI peripheral board card.Then,a soft panel ofthe top-level application is developed,all debugging functions can be realized on the single test interface.The results of simulation and part of the functional tests show that the portable external system equivalent device can realize the function of signal excitation,and the design content meets the requirements.