Design, development, and evaluation of an automatic guidance system for tractor tracking along the contour line on inclined surfaces

Abstract

Introduction: Automatic guidance of tractors in the mechanized farming practice has taken the attention of agricultural engineers in the last two decades. For this to be truly practical on the farm, it should be economical, simple to operate and entirely contained on the vehicle. Different types of steering systems such as leader- cable, laser- controlled, radio- operated and contactor- type have been developed for automatic guidance. The automatic leveling system is used on hillside machines to keep the separator level when operating on hillsides. This system has three parts: fluid level system, electrical system and hydraulic system. The fluid level system consists of fluid reservoir and a leveling control switch box. The fluid level system actuates the electrical system of the leveling unit. The electrical system which actuated by the fluid system consist of four micro switches in the leveling control switch box, two micro switches in the limit control box, a solenoid in the hydraulic control level, manual leveling control switch, and a leveling limit warning light. The hydraulic system maintains the level of the separator when the machine is operating on a hillside. The present study was aimed to develop a reliable, versatile and easy to maintain system to fit our economy and low technology level of farmers for hillside- range development or fallow farming. The automatic guidance system has been implemented successfully on agricultural vehicles on the basis of three components, i.e. sensors, processors and actuator elements. The study site (N, latitude; E, longitude; and 1810 m above sea level) was located at the Agricultural Research Center, Shiraz University, 15 km northwest of Shiraz, Fars Province, Iran. MF-399 agricultural tractor manufactured by ITMCO, Tabriz, Iran was used for doing the experiments. Materials and Methods:The Level Sensing System: The biaxial tilt industrial sensor (ZCT245AL- China) with digital output can be connected to the computer and received angular position in x and y coordinates. An assumed degree could be considered as basis degree and the measured frequency was adjustable. The tilt sensor located along the axial length of tractor and leads the angles which are created by longitudinal axle transverse axle of the tractor in related to horizontal level. It was used for contour lines detecting. The potentiometer located on the steering wheel of the tractor and pressure sensor which used with goniometer sensor used keeping uniformly of leveling points in tractor motion. The pressure sensor (SN-SCP1000- South Korea) which is used in leveling system can detect the elevation changes. In this way, by defining a limitation of altitude for system, it would be able to stop steering turning motor which was coupled to tractor steering rod automatically. By resetting, the tractor could be able to live in a new level position. To avoid excessive left and right steering wheels deviation and interfering with other lines of travel, potentiometer was used. The deviation degree for steering rod from center to left or right was selected 120 degrees. Accordingly, the wheels would not be able to move more than 10 degrees to each direction. The Processing System: The electrical circuit graphically designed and simulated by software (Altium Designer, 2009) and installed on the tractor. The components of this circuit are as follows: Electrical board, two relays which control the electrical pathway in both directions, a battery with 12 volts of electric potential as electrical power supply, ATmeGA32 microcontroller which was made by Atmel company as main core for information processing, RS232 protocol was used for making correlation between serial port (COM) and the microcontroller and two capacitors for reducing noises. The Actuator System: The output signals from the a processing system, were lead in the actuator system would order and indicative of left- turn or right- turn command, were introduced to actuator- units include an electric- gearbox motor that stimulate the steering wheel shaft of the tractor by chain and sprocket and conduct the tractor in leveling traces at the desired speed. Before hitching any implements such as row planter behind the tractor, the system was successfully tested on average slopes of 14.5% using a tracing powder. Results and Discussion: A plot of the average elevation of each 12 lines traced for a length of about 50 meters, H0, versus the actual elevation of 12 to 16 equally spaced points of each trace, H, produced the following relationship: H0= 0.142+ 0.990 H Indicating a reasonably acceptable performance with standard error and R2 0.048 and 99.3% respectively. Conclusions:The row planting in various slopes coincided with the contour lines of ground (Duncan’s Multiple Range Test p ≤ 0.05). Also, no significant difference was observed among the slopes and index of length and dry weight of root and shoot. The percentage of the emergence index in the high slopes (18-21%) showed significant differences. Hence by increasing slopes, the percentage of seed emergence was decreased.

Keywords

• contour lines
• contour planting
• self-leveling system