Design, Construction and Evaluation of a Measuring Device for Rice Picker Combine Losses Based on Piezoelectric Sensor at Lab Scale

Introdution
Nowadays, supplying the needed food for people is one of the main global issues. Among foods, rice as the second vital crop has an important role in the world. The amount of global rice losses is about 21 percent and in Iran is reported between 16 to 30 percent that the most amount of it belongs to harvest (mowers and crushers) part. The measuring device for rice picker combine losses at lab scale is a tool which could report the losses of separating and cleaning units. One of the advantages of this device is choosing maximum speed by the operator with considering the acceptable amount of seed losses. Therefore, research about detecting and decreasing this type of losses is important. In this research, only the losses of the harvesting step, especially at the end of a combine harvester machine was addressed. Different methods included piezoelectric and acoustic sensors, load cell, and FIS controller were used as the measuring device of rice picker combine seed losses. In this research, on the contrary with other studies, the slope of meshed plate and humidity of product was measured using a piezoelectric sensor at lab scale under different conditions of the rotational speed of meshed plate. Therefore, the general purpose of this research was design, construction, and evaluation of the measuring device for rice picker combine losses based on the piezoelectric sensor at lab scale to measure the seed losses in the straws at the end of the machine at rice picking.

A meshed plate with the 100 × 60 cm2 dimension was one of the main parts of the measuring device of seed losses. The diameter of its meshes was 7 mm based on the rice seed size. It separates the rice seeds from straws. Separated seeds from this part were fallen on the other plate which is mounted under the meshed plate. The seeds through four separated routes were fallen on the sensors and output pulses from sensors were sent to the operator plus shown at a monitor. The used seeds at tests were selected from Fajr rice cultivar with a high yield and short height. The used piezoelectric sensor had the ability to convert imposed force and pressure to voltage and vice versa. After the seed falling on the sensor and its vibration, the piezoelectric sensor worked as a beam fixed at one end. The used  Integrated Circuit (IC) was ATMEGA328, which receives the needed data through the sensor as a processing and action system. An electric motor was used to create the rotational speed of meshed plate. The LCD indicator was used for monitoring the obtained data from the test. The amount of seed losses at the end of rice picker combine machine was studied using the piezoelectric sensor with high sensitivity for detecting seeds to separate the seeds from straws. The tested sample in this research was 1 kg straw plus 52 g seed which was equal to 3 percent loss at the end of the harvest combine machine. The experimental design was a simple randomized complete design with three replications. The used treatments included the rotational speed of meshed plate at 3 levels (50, 75, and 100 rpm), the slope of meshed plate at 3 levels (25, 37, and 45 deg) plus humidity at 3 levels (12, 18, and 24 percent). Then the data analysis was done using the conducted test design. The GenStat software was used for data analysis.

The analysis of variance table showed that all treatments have a significant difference in the number of rice lost seeds at 1% probability level. The interaction between the rotational speed of meshed plate and seed humidity had a significant difference at the 1% level. On this base, the best separation of seed from straw recorded at 100 rpm and 12% humidity. The reason was the higher vibration of the meshed plate at high rotational speed and better separation of seeds at low humidity. Increasing the slope of meshed plate and humidity of seeds caused decreasing in the device efficiency. Because the motion speed of the sample on the meshed plate increased with increasing the slope of the meshed plate, a lower period was needed for separating the seeds from straws, and this separation at higher humidity was done hardly. The highest efficiency at this condition was obtained with 12% humidity and 25º slope. Increment of the rotational speed of meshed plate and decrement of meshed plate slope caused the best separation by the device. Its reason was high vibration at the high rotational speed and having enough time for separating the seeds from straws at a low slope of the meshed plate. The best angle for separating was 37º. Increment of the rotational speed of meshed plate, decrement of meshed plate slope, and sample humidity caused increasing the device efficiency. The reasons were high vibration at high rotational speed, having enough time for separating seeds from straws, and decreasing the compression at low humidity amounts. The results showed that the best device efficiency with 95.51% was obtained at 100 rpm rotational speed, humidity of 12%, and 25º slope of the meshed plate.

In this research, a measuring device for detecting the amount of seed losses combined by straws at the end of a rice picker combine machine was designed and constructed, and then was assessed. The results of lab tests showed that increment of the rotational speed of meshed plate plus decrement of meshed plate slope and sample humidity causes an increment of device efficiency. With installation and evaluation of this device on the rice picker combine machine, the needed correction at the farm will be done and the amount of losses will be decreased.