design, construction and evaluation of a row crop thinning machine

equipment availability is necessary in the development of agriculture mechanization. crop thinning is one of the most important stages in row crop production which is laborious and costly. the objective of this project is design and construction of a row crop thinning machine. four main system units are plant sensors, ground sensors, control and thinning platforms. in this machine the unwanted plants on the rows are randomly removed by employing a pneumatically system. a blade on a vertical arm with pendulum motion removes the plant from the rows. the machine control system consists of an arm and a blade which is activated by a double acting cylinder and equipped with a relay and a timer. the pneumatic cylinder is controlled via a solenoid valve. laboratory tests were conducted to validate the machine performance. some other preliminary tests also were performed for optimization of parameters such as cinematic index and cutting length of blades. the laboratory tests (totally 9 tests) were performed with a constant forward speed and three levels of plant density, using artificial plants. the data were analyzed using spss software. the results show that satisfactory performance of the machine is achieved when the plant density is moderate i.e. the thinning performance reduces with higher plant distance in the row. the other effective variable on machine performance is the adjustment of sensor sensitivity, which is used to distinguish between week and strong plants. in general the machine performance is sensitive to plant shape and morphology, plant distribution pattern in the field, growing stage of the plants, time of thinning and the effectiveness of previous weeding operations