*Northwest A&F Univ., College of Mechan. & Electron. Eng., Yangling, 712100 Shaanxi, China.*

*Northwest A&F Univ., College of Mechan. & Electron. Eng., Yangling, 712100 Shaanxi, China.*

*S. Seifullin Kazakh Agro Tech. Univ., Techn. Fac., Astana 010000, Kazakhstan.*

*SouthWest Univ., College of Eng. & Technol., Beibei, 400715 Chongqing, China.*

*Northwest A&F Univ., College of Mechan. & Electron. Eng., Yangling, 712100 Shaanxi, China.*

*Northwest A&F Univ., College of Mechan. & Electron. Eng., Yangling, 712100 Shaanxi, China.*

*Northwest A&F Univ., College of Mechan. & Electron. Eng., Yangling, 712100 Shaanxi, China.*

*Northwest A&F Univ., College of Mechan. & Electron. Eng., Yangling, 712100 Shaanxi, China.*

To accurately and efficiently remove unripe fruit, flowers, leaves, and other impurities in machine-harvested

Winnowing equipment for machine-harvested

Winnowing equipment for machine-harvested

As shown in _{B}
. Because the buoyancy has a slight influence on the movement of ripe fruit in the horizontal airflow compared with the gravity and horizontal airflow force, it can be ignored (

where
^{3}
;
^{2}
;
_{a}
is the velocity of horizontal airflow, m/s; and
_{x}
is the initial velocity of ripe fruit entering the horizontal airflow, m/s.

The tangent of angle

Because machine-harvested

where
_{1}
is the tight-side tensile force of the input conveyor, N;
_{2}
is the slack-side tensile force of the input conveyor, N;
_{2}
is the input conveyor speed, m/s.

The relation equation between the tight-side tensile force of the input conveyor and the slack-side tensile force of the input conveyor can be obtained as follows:

where

Because the input conveyor speed was<10 m/s, the centrifugal force can be ignored (
_{c}
can be obtained as follows:

where
_{c}
is the calculated transmission power of the input conveyor, kW; and
_{A}
is the working condition coefficient.

Therefore, the equations of the diameter of the driving wheel of the input conveyor
_{1}
, diameter of the driven wheel of the input conveyor
_{2}
, and center distance of the input conveyor

where
_{1}
is the diameter of the driving wheel of the input conveyor, mm;
_{1}
is the revolving speed of the driving wheel of the input conveyor, r/min;
_{2}
is the diameter of the driven wheel of the input conveyor, mm;

The design of the output conveyor was as outlined above. After calculation, the design parameters of conveyors are listed in

According to the nominal transmission power, the electric motors adopted alternating current electric motors (type: 5GN30KB; rated power: 60W; reduction ratio: 1:30; manufactured by Guangdong Shengkai Motor Manufacturing Co., Ltd., China). The input conveyor and output conveyor can be driven to rotate by the toothed chain. The toothed chain was designed according to the calculated transmission power as follows:

where
_{z}
is the tooth number coefficient.

A brushless motor (type: Sunnysky; KV value: 1400; manufactured by Zhongshan Langyu Model Co., Ltd., China) was used as the fan, powered by the lithium battery (type: Geshi ACE 5C; capacity: 3300 mAh; manufactured by Shenzhen Grepow Battery Co., Ltd., China). The controller generated pulse width modulation waves to control the run and stop of the fan by controlling the electronic speed regulator (type: Skywalker 40A; manufactured by Shenzhen Hobbywing Technology Co., Ltd., China) and to adjust the airflow speed.

The circuit diagram of winnowing equipment is shown in

The horizontal airflow model was established based on C++ in Microsoft Visual Studio. Because the size of ripe fruit was approximately consistent and the horizontal airflow parameters (
_{B}
and the free flow resistance force
_{d}
are as follows:

where
_{B}
is the buoyancy, N;
_{d}
is the free flow resistance force, N;
^{2}
;
^{3}
;
^{2}
;
_{D}
is the resistance coefficient which is calculated as follows:

Therefore,
_{D}
depends on the Reynolds number

where

The movement of ripe fruit in the horizontal airflow was simulated based on DEM using EDEM software. In this study, the Moving Plane model was selected; the parameters of materials are listed in

Based on previous research and references review (

According to the simulation, the airflow speed, input conveyor speed, and input-output conveyor distance greatly affected the rate of impurity change and the clearance rate of ripe fruit. Simulation results showed that winnowing equipment met these conditions, with most of ripe fruit falling on the output conveyor and most of unripe fruit, flowers, and leaves removed at an airflow speed of 5-6 m/s, input conveyor speed of 0.4-0.6 m/s, and input-output conveyor distance of 260- 270 mm.

Ningqi 7 was selected as the experiment variety. The following instruments were used: 1) an electronic vernier caliper (type: AIRAJ second-generation product; range: 0-300 mm; precision: 0.01 mm; manufactured by Qingdao Yigou Hardware Tools Co., Ltd., China); 2) a digital illuminometer (type: PM6612L; manufactured by Shenzhen New Huayi Instrument Co., Ltd., China); 3) a tachometer (type: DT2236B; manufactured by Shenzhen Sanpo Instrument Co., Ltd., China); 4) a digital anemometer (type: PM6252B; manufactured by Shenzhen New Huayi Instrument Co., Ltd., China).

The winnowing equipment was used to remove as many impurities as possible (
_{1}
and the clearance rate of ripe fruit
_{2}
were selected as performance indices in the experiment. Corresponding equations to calculate these indices are as follows:

where
_{1}
is the amount of unripe fruit, flowers, and leaves before winnowing;
_{2}
is the amount of ripe fruit, unripe fruit, flowers, and leaves before winnowing;
_{3}
is the amount of unripe fruit, flowers, and leaves after winnowing;
_{4}
is the amount of ripe fruit, unripe fruit, flowers, and leaves after winnowing;
_{5}
is the amount of removed ripe fruit after winnowing; and
_{6}
is the amount of ripe fruit before winnowing.

The experiment was conducted in Zhongning in the Ningxia Hui Autonomous Region (37°22'56"N, 105°37'21"E) on June 26, 2018; the temperature was 27.2°C, the humidity was 30.1%, and the illuminance was 520.6 Lux. Based on the theoretical analysis, the main factors affecting the performance of the winnowing equipment were determined to be the airflow speed, input conveyor speed, and input-output conveyor distance. The previous tests and simulation analysis indicated the following suitable value range for the factors: the airflow speed
_{1}
was 5-6 m/s; the input conveyor speed
_{2}
was 0.4-0.6 m/s; and the input-output conveyor distance
_{3}
was 260-270 mm. The airflow speed was adjusted by the electronic speed regulator and measured with the digital anemometer. The input conveyor speed was adjusted by the electronic speed governor and measured with the tachometer. The input-output conveyor distance was adjusted by lifting the input conveyor and measured with the electronic vernier caliper.

Three factors and three levels were used in a quadratic orthogonal rotation design; the codes of factors are listed in

The regression model of the rate of impurity change (response) using codes of all factors as variables was as follows:

ANOVA results of the rate of impurity change are shown in _{1}
,
_{2}
,
_{3}
,
_{1}
_{2}
,
_{1}
^{2}
,
_{2}
^{2}
, and
_{3}
^{2}
each had a significant effect on the rate of impurity change (

The regression model of the clearance rate of ripe fruit (response) using codes of all factors as variables was as follows:

ANOVA results of the clearance rate of ripe fruit are shown in _{1}
,
_{2}
,
_{3}
,
_{1}
_{2}
,
_{1}
^{2}
,
_{2}
^{2}
, and
_{3}
^{2}
each had a significant effect on the clearance rate of ripe fruit (

The response surface methodology was used to analyze the effects of all factors on the rate of impurity change; the response surface results of the regression equation (

The response surface methodology was used to analyze the effects of all factors on the clearance rate of ripe fruit; the response surface results of the regression equation (

After prediction, the optimal parameter combination was determined to be an airflow speed of 5.52 m/s, input conveyor speed of 0.5 m/s, and input-output conveyor distance of 265.04 mm.

The field experiment was completed on June 28, 2018 and 15 groups were conducted in this experiment to eliminate random errors. The chosen experiment parameter combination was an airflow speed of 5.52 m/s, input conveyor speed of 0.5 m/s, and input-output conveyor distance of 265.04 mm. As depicted in

The machine-harvested