مشخصات پژوهش

Precision guidance of agricultural implements is one of the goals that followed by precision agriculture systems. Despite of using low volume spraying techniques, mechanical control of weed using row crop hoes is still utilized by a significant number of farmers. In this paper, an electro-hydraulic control system was designed to control the lateral movements of a row crop cultivator in the presence of the tractor directional motion and the measurement noise. A sinusoid path assumed for the tractor by amplitude of 15 cm and period of 50 m with a constant forward speed of 2 m s-1. It is also assumed that the instantaneous coordinates of the tractor and implement are obtained from a DGPS receiver with standard deviation of 8.594e-3 m and 1.104e-2 m at the X and Y directions, respectively. Hydraulic actuator consists of a servo valve and servo cylinder. The design has been performed for MOOG series 72 servo valves with the nominal flow rate of 96.75 l min-1. The hydraulic cylinder was adopted from Shore- Western manufacture products 91series. The actuator dynamics was modeled by a five order system consisting of a two order transfer function for the servo valve and a three order transfer function for the servo cylinder. Different parameters of the servo valve and servo cylinder adopted from the commercial series. At first, an internal controller was designed for the precision control of the actuator and then, the actuator was used to control the lateral motions of the implement. The standard deviation of the implement lateral position was 4.6e-3 m when the PI-controller had settled. The .validity of the proposed control system was verified by computer simulation