Experimental Research Of Capacitance-type Sensor For Seeding Performance Detection

In order to improve the adaptability of metering performance testing system, ourresearch group put forward a new idea using capacitance sensors to seeding detection.Previous work designed three kinds of capacitive sensors and metering performance testingof hardware and software systems, in a simple test bed completed a single seed flow testing,verified the feasibility of a capacitive seeding performance detection system. This paperwill use capacitive sensor in the detection of finger clip corn precision seeder performancetesting, in order to arrive at a reasonable assembly programs and seed speed adaptation,optimization of sensor structure parameters to improve the detection performance of thesensor. The main research contents of this paper are as follows.(1) Simulation analysis of capacitive seeding performance detection system. UsingANSYS software for three kinds of sensors static simulation of maize seed testing, analyzethe impact of the structure to the sensor test results. According to the structure of seed tube,establishment an analog space of length60mm,width24mm,height40mm. Referenceparameters of the actual seed build a side length of4mm seed simplified model in the centerof the sensor. Set excitation voltage1.5V, corn seed and air permittivity dielectric constant3and1, through simulating there are seeds pass or not get the change of capacitance valuesare：The Crossed E-shaped plate type sensor is0.232pF; The Paralleled plate type sensor is0.014pF; The Differential tri-plates type sensor is0.235pF. Compared the simulation resultswith the single grain of corn seed flow test results，they are the same. The Crossed E-shapedplate type sensor and The Differential tri-plates type sensor can achieve seed testing, TheDifferential tri-plates type sensor can`t.(2) Experimental research of capacitance-type sensor for seeding Performance detection.To investigate the impact of capacitance sensors structural parameters on corn seedingperformance test results, will be equipped with E-type capacitive sensor to the finger clipseeder for indoor bench testing. Analysis the impact on the sensor output of plate spacing,plate mounting location, locomotives operating speed, determine the plate spacing0.4~2mm,plate mounting location20~30mm, locomotive operating speed5~9km/h, even select5level, pilot study using uniform design. The results indicate that there are seed through thecapacitance value becomes large. In the condition of plate spacing is1.6mm, plate mountingposition is25cm, the operating speed is5km/h, when seed through the capacitance averageamount is2.427pF, no seeds through is2.421pF. Although the capacitance values havechanged, but the interfering signals strong, detection effect is not ideal.(3) Experimental study of seed motion state in seed tube. In order to investigate the reasons for the strong signal interference of capacitance sensor output, we make a test oftrajectory of seed in the seed tube. Analysis of seeds from the sensor, seeds rolling andsliding state influence on detection performance.To examine the trajectory of the seeds in the seed tube, use high-speed camera law in thecondition of seeding rate is1~8km/h, use self-made organic glass seed tube in seeding teststand have an experimental study. Test show that: When seeding rate is less than2km/h, theseed went into the seed tube of the horizontal velocity0.1256m/s, between the seed and thebottom wall of the seed tube has no obvious gap, planting uniform and stable, Seed slidingdown along the bottom wall of seed tube. When planting speed is3km/h to6.5km/h, in thesensor`s install range during the seed movement the transversely average gap between seedand seed tube bottom wall is3.775~6.175mm, and the seeds has a rolling phenomenon.When planting faster than7km/h, seeds are discharged the lateral displacement is greaterthan7.3mm. In the sensor`s install range, seeds and seed tube bottom wall averagespacing is greater than8.208mm, and the seeds have a significant phenomenon in the courseof the campaign rebuffed and rolling phenomenon.In order to investigate the influence to detection performance of distance between seedand sensor, using homemade cardboard seed tube and simple test bench to test in the seedmovement speed is0.664~1.192m/s. Test show that: When there is no distance betweenseed and sensor, the capacitance variation amount of the average is0.068~0.098pF, canachieve seed testing. When the distance is1mm the average variation of capacitance is0.006~0.014pF, the distance is2mm for the average change in capacitance is0.004~0.01pF,can`t detect the movement of seeds.To investigate the impact of seed sliding and rolling on the sensor output, we have a teststudy in simple test rig, using10seed to test then requirements capacitance mean method.Test show that: When Seed sliding outdated the sensor surface there is an obvious largercapacitance value change than scrolling through. Under the same condition, when the seedslipping through the capacitive sensor, the average change in capacitance is0.109pF, canachieve seed testing, scrolling through the capacitive sensor the average change ofcapacitance value is0.02pF, can`t achieve seed testing.When seeding faster than3km/h, seed trajectory far from the capacitive sensor, affect thetest results, then need to improvement the seed tube structural, make the seeds lose speciesalong the bottom of the tube wall fell, which to improve the detection results.