Research And Implementation Of In-vehicle Compaction Real-time Detector

During road construction,compaction acts as an important part in making subgrade and pavement materials compact gradually,and compaction measurement is an effective measure to guarantee quality of compaction.In-vehicle compaction detector fills the limitation of traditional detection method with fast,continuous and lossless compaction detection.In the paper,the study is centered on the implementation of software and hardware of compaction detector,accurate positioning method,compaction detection method,etc.,with in-vehicle compaction real-time detector as the object of study.Firstly,the paper elaborates the implementation of the hardware of in-vehicle compaction detector.The paper collects vibration acceleration signal of road roller with IEPE sensor,designs constant current source circuit to provide the sensor with current excitation,and designs a GPS/UWB double positioning module.What's more,a design plan of dual processor is put forward in the paper,that is,co-processor STM32F4 is responsible for A/D sampling and DSP operation and the main processor i.MX6Q is in charge of transmitting data as well as controlling each function module.In order to strength instantaneity of the system,SPI bus is applied between the dual processor for communication.Secondly,the paper designs software for compaction detector based on the framework of embedded Linux+Qt.The paper introduces design method of Linux device driver and focuses on the design of SPI driver.A graphical user interface is designed based on Qt framework,realizing the interface function between machine and human,so as to provide real-time information of compaction quality to the roller operator and assist in optimizing the established construction plan.Thirdly,the paper studies accurate positioning method based on the needs of tracking roller pass and location in compaction measurement.Taking into account the high cost of RTK-GPS,the paper selects the civil GPS and UWB to achieve the combination of positioning,designs an algorithm of path correction based on Kalman filter to improve positioning accuracy of civil GPS,elaborates positioning principle of UWB technology,and studies two-way distance measurement based on TOF and Trilateration positioning algorithm.During the research,it is found that UWB is able to achieve a higher positioning accuracy when the distance of base stations is small.Lastly,the paper studies compaction detection method based on harmonic analysis and tries to reflect the compaction of asphalt pavement with CMV index.In the paper,the vibration acceleration signal collected from field test is being processed.Based on hamming window,FIR digital filter is designed with good de-noising effect.The transformation of frequency domain is implemented with FFT operation.The paper extracts fundamental wave and secondary harmonic from vibration signal in frequency spectrum and introduces CMV compaction index into calculation.The result shows that with the increase of roller pass number,the average CMV value increases gradually,which meets the trend of compaction increase.In conclusion,the paper achieves research and implementation of in-vehicle compaction real-time detector and lays a foundation for further research on intelligent compaction technology.