The Research And Determination On Virtual Instrument Based On Vehicle Experimentation And Analysis System

The main job of this thesis is to design a high accuracy portable examination instrument of signals. Examination instrument is composed of three sections: the first part, high accuracy vibration signal's examination circuits for sampling and adjustment; the second part, USB host partition for transference and storage; the third part, the visual screen playing the vibration signals which is programmed in the Visual C++ language at the PC terminal. The usage of signal examination circuits for high accurate collection and adjustment is as the following. These sensors should be designed for military usage and there are signal modulators inside . The sensors should have the advantages of high sensitivity, small temperature excursion, stable zero output and wide frequency band, etc. For example, CA-YZ-123C(A)-100, it's a water density three stalks vibration sensor. The vibration sensitive component is a silicon quantity hunch which is supported by silicon frame with several beams. When the silicon frame is suffered by the vibrate pressure, the beams'resistor value is changed since the dint's function of inertia. And then the change is turned to voltage value and put out by the electric bridges'conversion. The sensor can quantitatively measure vibration information of oscillating objects from X stalk, Y stalk and Z stalk. Three exportations of the electric bridges are reached to 12 bits analogue/digital converter -ADS7864 each other. ADS7864 can proceed analogue/ digital conversion under the control of Microcomputer P89C51RD2. For the purpose of using the system in various conditions, we add an adjustment circuit of sampling signals between sensors and analogue/digital converters, which is controlled by simulation switch-CC4051.If we connect CC4051 with different feedback resistors, then the input voltage ranges of sampling signal can be turned from-2.5V～+2.5 V to -5 V～+5V and -10 V～+10V,this method improves the using scopes of the equipment. At the same time, there link three 8253 counters in the signal sampling part ,which can examine whether the car's output pulse is meeting with the practical requestion. In order to locate the systems's functions at the beginning of the operation, we build a keyboard with 8*8 keys ( which is under the control of a serial interface chip zlg7289)and a show screen of LCD(240*64). Host part. We adopt the USB host/equipment controller SL811HS that is produced by Cypress company to realize the data transference and then store the large quantity of real time data to the Usb disk.In this part, author has designed a lot of programs to realize the communication process by making the abstract principle to a specific procedure in C language. In the USB host, we must write programs with the following criterions:1)USB 1.1 criterion;2)Mass Storage Class criterion;3)Bulk-Only transmissionprotocol;4)FAT16 file system criterion. The first three criterions are the basement of USB HOST communication, and the last one is requested by the Usb storage device. USB storage device requests the file stored in it is stored with the pattern of FAT16 criterion. In order that the host can read and write the file correctly to the USB disk, we must make the criterion programmed. By the way the author has added the mistake examination, rectify and the mistake manifestation etc. to the communication process, to make the whole transmission process stable and dependable. Since the SL811HS host/equipment controller is just an USB host interface chip and there is no microcomputer inside. So we must add a microcomputer at the peripheral circuits as its process controlling. In the consideration of capacity of ROM and the speed of RAM, we adopt the microcomputer -P89C51RD2 of PHILIPS company to realize the data handling and controlling. The two microcomputers, one in signal sampling circuits and the other in USB host part, are connected by the FIFO-IDT7130 , which is equal to SRAM for the data transmission. The capacity of the FIFO is 1K Bytes, the transmission process is: when the ADC has finished its conversion, it transfers its data to the first microcomputer through the IO port. Then the MCU delivers the data to the FIFO with the pins A0L~A7L.After the data count to 1K Bytes (from 000H to 3FEH), the channels on the FIFO right way open and send the data to the second MCU. Since the MCU 2 is connected with both USB interface and storage device, so we can make the data transfer from the MCU's RAM to the USB disk directly. Till now, the transmission of data is completed. The majority of the whole development is the exploitation of USB host, and the center of USB host is writing programs of communication's process.