Development of a semi autonomous robotic platform for intercultural operations in row crops

Abstract

A semi-autonomous robotic platform was conceptualized for performing the intercultural operations in row crops. It was expected to be capable of navigating within the field and performing the intended intercultural operation according to the user command. The dimensions of the chassis (track width and ground clearance) were determined on the basis of agronomic characteristics of the crop. Wheel mounted geared motors were used for self-propulsion. The wheel variables were decided based on the rolling resistance and terramechanics relationships. A six-wheel independent drive skidsteering drive mechanism was provided to the robotic platform. Arduino Mega was the microcontroller used which was interfaced with the drive motors via L298N motor driver for speed and direction control. The microcontroller was programmed in Arduino IDE software using C++ language. The wireless communication system was based on Radio Frequency (RF) protocol using Flysky FS i6 2.4GHz Six-channel Transmitter Remote Controller with FS-iA6 Receiver unit. The monitoring guidance of the prototype was accomplished on the basis of real-time video streaming using Wi-Fi enabled wireless IP camera. The operational unit was controlled by relay driver circuits. Geared DC motor operated cable drive slider mechanisms actuated the position control of the sprayer unit. The developed prototype was evaluated in both lab and field conditions. The speed of travel obtained was less than the rated speed. The total power consumed by the prototype increased with increase in the load. The deviation of the prototype from a straight path could be corrected by the use of steering controls by the operator. The control unit functioned satisfactorily for every command by the user. During the basic field trial, a non-uniform distribution of load on each ground-contact point occurred due to the undulated terrain. Therefore, wheels were subjected to sinkage which resulted in lack of proper traction and wheel slip. The tractive forces were then insufficient to overcome the soil resistance. The test resulted in the requirement for a modified drive mechanism for the prototype. The modified design of the drive mechanism comprised of high torque motors (24 V, 8Nm, 300 RPM DC motor) with reducer unit, high power motor drivers (BTS7960) and larger diameter pneumatic wheels (30.48 cm diameter). A suspension could also be provided to maintain uniform load distribution on each groundcontact points. As the torque exerted by these motors would be greater than the required torque, the design was safe. The cost for modified prototype was estimated to be Rs.65000/-.