| As an important active safety regulation of auto, it's degree wide or narrow impact to finding the roadway situation information, reaction,judgement time for drivers directly, especially for scorching M1 vehicles, whose significance is therefore right away even more outstanding. It is ruled in the Motor vehicles-Forward visibility for drivers-Requirement and measurement methods (GB 11562-94), the requirement and measurement methods of the direct visibility within 180 angles located ahead of the drivers for the M1 motor. This standard is one of the compelling certification project of country motor vehicles (automobile products).By now, there is no special measuring instrument for checking forward visibility. At the same time, in this standard, the requirement of the forward visibility for drivers is stated by angle. Usually, we use three Coordinate Measuring Instrument to get the coordinate value of the space points, then calculate the angle.It does not give the clear calculating method in the Motor vehicles-Forward visibility for drivers-Requirement and measurement methods (GB 11562-94). Most way of testing the forward visibility of automobile is recording the coordinate value gotten from three Coordinate Measuring Instrument, computing it with calculator (partially use Excel work out the result), then types the test report and record manually. So we need to develop the measurement system for the motor vehicles—Forward visibility for drivers, perfectly. That can get the value of the three Coordinate Measuring Instrument automatically, compute with them. In order to convenient for pick-up, analyze the data later, the system should store the data into database, at the same time, finish the test report and record automatically, reduce the amount of physical labor of the testing person, raise the accuracy of the test and work efficiency.The software programs the calculate procedure of test project in the standard, gotten the data from data interface automatically, compute them, saves the measurement data into database, processes the test report and record automatically. This must raise the accuracy of the test and work efficiency.Due to VB has the strong development function and is easily put into use, it also can communicate with the software of Microsoft (word, excel, access), using VBA. We select VB to develop the software under Windows XP & Microsoft Office platform.Main contents of the system:Communication between PC and three Coordinate Measuring Instrument It uses HXY-2500 typed three Coordinate Measuring Instrument as measurement tools, which produced by NIMTT. This machine supplies RS232 interface to communicate with PC. Developing the serial communication program with VB, there are two ways: first using the communication API function, second using standard control Mscomm in VB.The serial communication API function in Windows XP adopts hardware and file general function. This typed function more has generality, and can realize the bottom hardware operations. But it is more complicated, need to know a large amount of the communicating knowledge, is more suitable for designing lower layer communication program.The control of Mscomm in VB supplies sending and receiving serial interface data function fully. The developer only know the usage of attributes and events of Mscomm, he can operate the serial interface easily.The system adopts the requirement mode of Mscomm to get the data from three Coordinate Measuring Instrument by serial interface.In order to suit the interface, data format of other type three Coordinate Measuring Instrument, the system prepares one data interface file (excel). So the system can get the value in the file written by repeated developed program, then compute them.The calculating method of the requirements of forward visibility According to the standard, building the coordinates system, first measure the adjustment space and back angle of the chair, the coordinates value of point R, calculate the coordinates value of points V, P. Second, we compute the space angle of the basic point on the glass frame and steering wheel, then we confirm the 2o lay, 2o point upon, the 5o lay, 5o point down, so we can compute the both eyes hinders angle via the mathematic model.Store the test data into databaseIn order to convenient for pick-up, analyze the data later, the system has the function, storing the data into database (Access). As an way to access all kinds of data, ADO is designed easy, it is a technique upon OLE-DB. It gives a uniform way to access the database via its inner attributes and methods. Most parts of VB programs use this way to link database.This system give the program, using ADO to store the test data into the prepared access file. That convenient for pick-up, analyze the data later.Finish the test report and record automaticallyIn order to reduce the amount of the physical labor of the testing person, and the error, this system can process the test data and the test result, finish the test report and record automatically.As far as word 2003 has strong function on the side of edit and makeup, using easily, especially, inline-applets VBA, so that VB can operate word easily. We save the test report and record with word format.This system does not adopt OLE and mail merger mode, located by bookmark directly used VB, fill the contents into word. The user do not need to input the information repeatedly, raise the veracity and efficiency of output. After a large amount of software testing work, the test department do a trial on it. We have achieved the target of this system, it can run rightly.In the designment processes, we work out the difficult question, such as the computing method of both eyes hinder angle, the control of the test project schedule, the storage of records, the pretreatment of the error. Finally, the system can get the data from three Coordinate Instrument, calculate the project via program, save the test data into database, process the test report and record automatically, improve the veracity and efficiency of the test greatly.
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