The current study developed and tested machine vision and automatic control systems to improve performance and reduce rice loss from paddy husker. This system was optimally adjusted for paddy type, moisture content of paddy, roller spacing and rotational speed of the motor. The percentage of breakage of rice kernels was determined using a machine vision system and a singulation device. If rice breakage was greater than a set point, the husker device was adjusted as necessary. The variables of paddy moisture content, roller spacing, and motor rotational speed were used to determine the working conditions of the husker for two paddy varieties. The dependent variables were husking index and rice kernel breakage percentage. An image processing algorithm was coded and evaluated in MATLAB software to determine the percentage of rice kernel breakage. The results showed that selection of proper treatment for the medium-sized kernel paddy, the average husking index was 82.65% and the average rice breakage was 3.88%. For the long kernel paddy, the average husking index and rice breakage were 51.4% and 27.46%, respectively. Without use of the system and with improper selection of motor rotational speed and roller spacing in the medium-sized kernel paddy produced a husking index of 61.58% and rice breakage of 7.51%. For the long kernel paddy, the husking index was 19.14% and rice breakage was 35.03%. Results from the algorithm showed that its accuracy ​​was 91.81%. Evaluation of the singulation device showed that a suction of -45 to -50 mmHg yielded an appropriate 81.3% separation efficiency. The best combination of the machine parameter levels were programmed into the system, which operated to make the proper adjustments automatically. This resulted in the most appropriate working conditions for husking in accordance with paddy variety, paddy moisture content, roller spacing, and motor rotational speed.

Grain motion on the blade was observed at the rated impeller speed of 2362 min−1using a high-speed camera. The grain exit velocity resulted in an impact force above the yield force of the husk but below the yield force of the grain. However, the maximum friction force experienced on the blade was far below the yield shear force of the husk for all three varieties of rice. Husking tests were performed at different impeller speeds using a hard urethane liner, a soft polystyrene liner and without a liner. Type of liner significantly affected the husking performance. Short-grain rice had high husking energy capacity and cracked grain ratio, but a low broken grain ratio compared with long-grain rice. Performance curves for the three varieties of rice were well expressed by the Weibull's distribution function.

Much of the paddy rice is run through more efficient continuous rubber rollers. The rubber does not scratch or "scarify" the seed coat the way the friction hullers do. As a result, the grain, with its harder, unscarred surface, takes considerably longer to cook than hand-picked rice; also it does not cook as uniformly and, most important, its yield is less. One cup of hand-harvested wild rice will produce nearly four cups of cooked grain, while a cup of paddy rice, after simmering twice as long as the hand-harvested grain, increases to only about three cups. Thus hand-harvested rice is considerably more economical than paddy rice.

The conventional way to husk rice is to pass it between two rubber rollers that are rotating with a surface speed differential. The resulting normal pressure and shear stress causes the husk to be peeled away from the kernel. The process is suited to high-rice flow rates, but is energy intensive and can result in considerable wear to the surfaces of the rollers. The operating parameters for machines of this design are usually determined and set empirically. In this article, some experiments and calculations had been carried out in order to explore the mechanisms involved in husking rice grains using this method. A simple sliding friction rig with load cell and high-speed camera was used to observe the mechanisms that occur during husking. The husking performance of different rubbers was compared for changes in the applied normal load. It was found that grains rotate between the rubber counterfaces on initial motion before being husked. In addition, harder rubbers were found to husk a higher proportion of entrained grains at lower applied normal load. By measuring the coefficient of friction between rice and rubber samples, the shear force required to husk a given percentage of grains could be calculated and was shown to be constant regardless of rubber type. Based on the mechanism seen in the high-speed video, it was evident that there was a limiting shear stress that was the governing factor over the husked ratio.

Friction and impact are two factors affecting paddy hulling performance of impeller type husker. It was hypothesized that reducing the impact as much as possible while increasing the frictional energy will increase the paddy hulling performance. Based on mathematical calculations, the amount of frictional energy almost only depends on the center angle of arch of the blade. Increasing the center angle of arch of the blade will improve the paddy hulling performance. Then, an improved impeller was made and comparative experiments were conducted using the new impeller and the commercial one mounted to both vertical and horizontal axis type husker. The test results showed that under the same hulling ratio, the broken rice ratio of the new impeller is lower than the commercial one by about 6% and 8% in the vertical and horizontal axis type husker, respectively.

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