The performance monitoring system of a portable seed-metering device was developed, which took a programmable logic controller (PLC) and a touchable screen as the core, to improve the convenience, flexibility and high precision of seed-metering monitoring. The monitoring system applied programming software, named Delta WPLSoft V2.37, to customize the PLC ladder diagram program and configuration software, named DOPSoft 2.00.04, to achieve the development of human computer interaction interface. The performance monitoring system of seed-metering device was mainly composed of detection system, control system and monitoring system. Detection system used two rectangular fiber area sensors, which were installed on the top and bottom of monitored area to detect qualified number, replay number, leakage number and seeding rate. The interval between seeds was detected by sensor to determine seed spacing. Closed loop control system was composed of PLC, servo driver, servo motor and pulse encoder, servo motor and seed-metering shaft was directly connected, the working speed of planter was simulated through controlling the speed of servo motor. It was used to control the seed-metering device of rotating shaft work speed, realize precision stepless regulation and ensure the seed-metering device of rotating shaft according to the set speed stable operation. Monitoring system was mainly controlled by the touch screen, which can display sowing device performance with various technique indexes and the running situation of the control system. It can set seed-metering relevant parameters on the human computer interaction interface to real-timely monitor the performance indicators of seed-metering device, including qualification rate, seed-missing rate, seed-repeating rate, coefficient of variation and breaking rate. The test results on monitoring system accuracy showed that the test accuracy of sensor 1 was above 95.42% and 1.77%~4.58% of test error was caused by the situation that two seeds may fall into the same monitoring zone at the same time during seed-metering process. The error was decided by metering performance of the device and the re-seeding caused by situation that two seeds fell into the same monitoring zone can be tested by sensor 2 which was under the seed sprout. The test error rate was between 1.77% and 4.58%, while the combination of sensor 1 and sensor 2 can get the accuracy rate range from 97.90% to 99.22%. Two tests of quadratic orthogonal regression on the rotation speed of planting plate and the interval of two seeds' falling time demonstrated that the performance of the chosen spoon-typed seed metering device was the best with rotation speed of 32.29 r/min, seed spacing of 28.44 cm and machine moving speed of 4.25 km/h. The parameter information from the test, including row spacing, qualification rate, seed-missing rate and seed-repeating rate, etc., can provide scientific basis for seed-metering device to achieve its best performance at appropriate speed. It can solve the bulkiness and intricacies shortage of seed-metering test-bed which was used indoors to imitate field working environment in China. Meanwhile, the results can provide technical reference for precisely seeding of corn no-tillage planter. © 2016, Chinese Society of Agricultural Machinery. All right reserved.
