Motion analysis and system response of fertilizer feed apparatus for paddy Variable-Rate fertilizer spreader

•Three devices that could adjust the application rate using different actuators were developed.•Mechanism motion analysis models were established based on vector equations.•Response analysis of system delay was performed according to the model of lag fertilization.•Tests were executed to calibrate lag distance, response time, and fertilizer accuracy.•Control system with correction response time alleviated the problem of lag falling fertilizing. Precision agriculture and variable-rate technology have gained increasing public interest. To improve the rapid response ability of the control system of a variable-rate fertilization and reduce the errors corresponding to the feed fertilizer system in a centrifugal variable-rate spreader, three devices that could adjust the application rate using different actuators were developed; these involved the gear and rack structure A, electric handspike structure B, and screw slider structure C. Mechanism motion analysis models were established based on vector equations, the response analysis of system delay was performed according to the model of lag fertilization, and subsequently, performance tests were executed to calibrate the lag distance of falling fertilizer, as well as the response time of actuators and the error of feed fertilization flow. The test results indicated that for actuators A, B, and C, the average lag distance of falling fertilization was in the order LA > LC > LB, with the respective values being 3.56, 2.72, and 1.85 m; the corresponding lag correction times were 1.99, 1.74, and 1.48 s, respectively. A positive proportional relation was noted between the application increment and response time of apparatus execution, and TBi > TCi > TAi (i denotes the corresponding feed fertilization flow). Furthermore, the error of fertilization flow first decreased and then increased with the increasing application rate; the extremum appeared between 250g/s and 380g/s, and γBi > γAi > γCi. The feed fertilizer with structure C was optimized and integrated field validation tests, and incorporating the corresponding correction time of lagging response Tlag = 1.74 s into the control system, the mean error of variable-rate fertilization system was determined as 9.67%, and the average lag distance of fertilization was 0.37 m. This indicated that the control system of variable-rate fertilization with correction response time alleviated the problem of lag falling fertilizing, improved the response speed of variable-rate fe