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Test vehicle road speed is an important parameter , which the wheel force , the pedal force , the combination of the wheel speed and other parameters , the dynamic performance of the vehicle of the vehicle , the braking system and match the performance of the ABS system development and operation the accuracy of such stability testing has important significance and application value. For a long time , the lack of effective speed means the speed of cars do curvilinear motion is difficult to accurately measure taken , car centroid determination of the dynamic trajectory can not be precise , so that the automotive vehicle braking direction secure stability and high-speed handling and stability test conditions difficult to control , test results are not a comprehensive response vehicle dynamic performance. Aiming at the high-cost low-precision speed sensor status , developed a single-chip microcomputer -based controller, using GPS speed technology to achieve all-weather , high-precision , low cost , high speed , easy to operate GPS speed sensors to instantaneous velocity of moving vehicles to achieve real-time collection . Firstly, through market research and analysis of the overall system function is proposed to PIC16F877A microcontroller as the core design. According to the principle of the system design and analysis of the system configuration , for a selection of the various components . Schematic design of the system , namely the design of the chip PIC16F877A, GPS receiving module and a D / A converter chip MAX518 other peripheral circuits of the various devices developed interface circuit , a communication interface circuit and power circuit. According to the design of a system circuit diagram for printed circuit board design and debug , error correction , and then optimize the design, manufacture GPS speed sensor hardware entity . Then the software system design, the MPLAB Integrated Development Environment , the application of the main assembly language design , serial asynchronous receiver subroutine design, serial data processing subroutine design, numerical conversion subroutine design , digital to analog (D / A conversion ) routine design and display subroutine designs. Finally made ??a GPS speed sensor applications in the automotive and all-terrain vehicle (ATV) on a speed test trials , obtain test data to verify the performance of the GPS speed sensor . Sensors are small , light weight , reliable, easy to operate, cost-effective, through multiple loading test, the system is stable and reliable.
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