Design And Experimental Study On Weighing System Of Intelligent Fertilizer Equipment

In integrated application of CAD, PLC control technology and sensor signal acquisition and processing, a weighing system for intelligent fertilizer equipment is designed in this study, which accomplish in weighing apart and fertilizer together for at most four different fertilizers at the same time. Combined with fuzzy PID control theory, the fuzzy PID controller of the weighing system that aims to control weigh is developed. A simulation platform that achieves simulation comparison of fuzzy PID controller and PID controller, is built by Matlab SIMULINK toolbox. Through weighing sensor calibration tests and the overall errors tests, the errors are reduced and the accuracy of the weighing system is improved. Main details are as follows:1. Owing to low efficiency and great errors that exist in fertilizer machines in our country, a weighing system that based on indirect weighing is designed and a weighing control system which based on PLC is proposed. In this system, four different fertilizers could be feeding independently, weighed separately, fertilizer together and controlled individually. In this case, fertilizer machines will be efficiency and accurate.2.Designing a fuzzy PID controller of the weighing system.The selection and definition of the controller are accomplished. In application of Matlab fuzzy logic toolbox and SIMULINK toolbox, a fuzzy PID controller of the weighing system is designed and developed. A simulation platform that achieves simulation comparison of fuzzy PID controller and PID controller, is built by Matlab SIMULINK toolbox. It’s turn out that, fuzzy PID controller has the faster response, higher precision and smaller overshoot.3.Carrying out error calibration tests for each weighing sensor and the prototype machine. In the weighing sensor error test, the error between measuring signal value of weighing sensor and the value of standard weight are determined in the operating of loading/unloading standard weight. The machine uses a total of 12 weighing sensors, 12 different weighing sensor signals. Different range and accuracy of weighing sensor are tested separately, and each group of tests are repeated three times. Through these tests, calibration coefficient and maximum error value of the weighing sensors can be obtained. Measured by the tests, the maximum error is about 0.47%, and the calibration coefficient of around 0.998. In the prototype machine error test, the error of machine with total mass and different types of fertilizer as variables are determined. A comparison of traditional PLC controller and PLC controller that contains fuzzy PID controller are operated. As a result, the latter controller would improve the precision of fertilizer machine, and the overall precision remains at around 1.85%.