طراحي، ساخت و ارزيابي يك حسگر تركيبي صوتي- نيرويي به منظور اندازه گيري بلادرنگ مقاومت مكانيكي خاك

چكيده انگليسي :

Design Development and Evaluation of a Combined Acoustic Force Sensor for On the go Measuring Soil Mechanical Resistance Tayebeh Rahnama tayebeh rahnama@gmail com Feb 2012 Department of Agricultural Machinery Isfahan University of Technology Isfahan 84156 83111 IranDegree M Sc Language FarsiSupervisors ahemmat@cc iut ac irAbstractSoil compaction is one of the most important factors responsible for soil physical degradation It alters thestructure of cultivated soil and thus changes a number of key soil properties for crop production and theenvironment Soil mechanical resistance can be used as indicator of soil compaction For on the gomapping of spatial variability in soil compaction single and multiple tip horizontal sensors have beendeveloped and used to measure the soil mechanical resistance However it has been reported that themeasured soil resistance in different soil layers depends on failure mode induced by the shank of thesensor It was hypothesized that the differences in acoustic signals detected by microphones inserted inthe tips of a multiple tip horizontal penetrometer could be used to differentiate the failure modes In thisresearch an acoustic multiple tip horizontal penetrometer was developed with three 30 prismatic tipsworking at depths of 10 20 and 30 cm The prismatic tips were attached horizontally to S shape load cellshoused inside a box behind the sensor vertical shank The tips working at 10 and 30 cm deep were alsofitted with the microphones With this arrangement as the combined sensor is being pulled through thesoil it measures soil mechanical resistance at three depths and it senses sound emitted by the soil failureat two depths The sensor was tested in a field with silty clay loam soil at four water contents WCs of0 5PL plastic limit 0 7PL 0 9PL and 1 1PL Cone index CI values were obtained with 2 cm depthincrements and 1 m horizontal intervals along each transect for comparison using a standard conepenetrometer Results showed that the soil WC had a significant effect on average horizontal resistanceindex HRI at both depths of 20 and 30 cm With an decrease in mc both HRI and CI values weresignificantly increased The critical depth of the shank in which the soil failure transition from brittle tocompressive occurs significantly increased while the soil WC decreased When the prismatic tips wereoperated below the critical depth of the sensor tips at depths of 20 and 30 WC there was a significantrelationship between HRI and CI whereas for shallower depth the relation was not significant This wasdue to change in failure mode from brittle to compressive mode below the critical depth Therefore thecorrelation between measurements obtained with both vertically and horizontally operated penetrometerswould be significant as long as both produced the same soil failure mode Result of recorded sounds atdepths of 10 and 30 cm showed that power spectral density acoustic signals at both depth of 10cm brittle failure mode and 30cm depth compressive failure mode soil were significantly different Acapacitance sensor was designed and developed soil water content The measurement principle dependson the electrice field of fringe capacitance The sensor was tested in 3 soil textures sandy sandy loamand clay loam The estatic calibration results indicated that there was a quadratic relationship with highcoefficient determination between the soil water content and sensor s output Soil s texture affected thesensor s output There was the measured WC were texture specific The result showed the developedsensor can detect soil failure mode in addition to measure the soil horizontal resistance index Precision farming soil compaction brittle failure plastic failure CapacitanceKeywords sensor measuring soil water content

رهنما، طيبه

طراحي، ساخت و ارزيابي يك حسگر تركيبي صوتي- نيرويي به منظور اندازه گيري بلادرنگ مقاومت مكانيكي خاك

كشاورزي دقيق , تراكم خاك , گسيختگي تردد , گسيختگي خميري , حسگرخازني , محتواي رطوبتي خاك