Monitoring method of rice seeds mass in vibrating tray for vacuum-panel precision seeder
According to the physical properties of rice seeds, triaxial ellipsoidal particle models were established based on the multi-sphere approach, and simulations of seeds motion in a vibrating tray were performed using the discrete element method (DEM). It was shown that the normal impact force Fn of seeds action on the tray was mainly composed of transient impact and accumulation force sections. The value of transient impact force was not stable because it was influenced comprehensively by shape of seed, vibration parameter and seeds-mass-per-unit-area (SMA). The variation of accumulation force determined by impulse change of seeds was relatively stable. Simulation results indicated that its value was almost linearly varied with SMA under a certain vibration parameter, and a real-time monitoring method of seeds mass in a vibrating tray is presented in this paper.
Two cantilever force sensors were back-to-back fixed at the bottom of seed tray. Due to a phasic difference ψ existed between the vibration inertia force and the seeds normal impact force Fn, a differential operation was performed between the output signals of two sensors to eliminate the influence of inertia force and extract Fn effectively. Then, a signal processing circuit mainly composed of differential amplifier, active low-pass filter, bias voltage circuit, envelope detector, and passive low-pass filter in series was designed to detect seeds mass. Calibration tests were carried out in laboratory with vibration frequency f and amplitude A of tray in the ranges of 9–13 Hz and 3–5 mm, the results showed that the comprehensive measurement errors were <3.5% with SMA κ in the range of 0.2–1.8 g/cm2.
Keywords: Seeds mass, Monitoring method, Vibrating tray, Impact force, Discrete element method