Research and design of automatic detection system of rice kernels
|Course||Mechanical Manufacturing and Automation|
|Keywords||paddy and wheat grain dynamic continuous measurement automatic measurementcontrol sensors and control system|
China is a major agricultural country with paddy and wheat as its main food crops. Increasing the yields of these two crops is of great significance to the sustained development of China’s economy. In academic research on paddy and wheat, it is often necessary to measure the weight of each grain and the number of grains contained in one panicle. For a long time this has been customarily done by picking up the grain manually and then weighing it on a balance, a practice that is both time consuming and exhausting. This project is therefore aimed at designing and developing an automatic measurement system capable of accurately counting the number of grains contained in one panicle of paddy or wheat and measuring the weight of each grain, so that measurement efficiency can be improved and workload can be reduced. Specific research work involved in this project is as follows:1. The overall design of the automatic countering and measuring system is completed. Through the actual design process and analysis of specific functional requirements, it is found that the key to improving measurement efficiency lies in achieving dynamic continuous measurement of a whole package of paddy or wheat grains. In addition, basic control mode for dynamic weighing process is determined, and the general layout planning of the whole system is completed.2. A mechanic mechanism capable of achieving automatic weighing process is designed. The designed mechanism incorporates feeding, weighing and discharging functions. The feeding device adopts an optimized vibration alignment mode for the purpose of increasing its adaptability. In designing the discharging device, systematic comparison was made between traditional robot arm and pneumatic driving methods. Modeling and assimilation were done on the stress of the robot arm with three-dimensional modeling software. For the purpose of reducing friction and ensuring accuracy, pneumatic valve rather than robot arm is adopted as driving device for the discharging assembly. In addition, a grading/separation chutes are designed which is capable of achieving three-level grading of paddy and wheat grains.3. An effective weighing system suitable for continuous measurement is developed. Based upon systematic comparison and analysis of various types of sensors manufactured by companies from different countries, WMC24-SH weighing module manufactured by Mettler-Toledo, a China-Swiss joint venture, is chosen for this project. As this weighing module has two remarkable features, namely high accuracy and long stabilizing time, different control modes were studied and tested in order to shorten its responding time. Through MATLAB-based modeling and analysis, two feasible solutions are designed. The first one is to incorporate an additional control system which is reciprocal to the original control system. The second is to construct with root locus technique a special control mechanism similar to an observer.4. An effective control system based on Siemens S7-200PLC is designed for the purpose of controlling the mechanic mechanism and realizing communication among sensors, PLC and the computer. Programming and comprehensive testing is completed.