عنوان مقاله [English]
Introduction :Robots are suitable for doing things that are tedious, difficult or dangerous to humans. One of the recent applications of robots is to perform various operations in the agricultural sector. The limitations in human resources and the demand for higher efficiency per unit area has made it necessary to use robots in agriculture. In the study, a robot spraying manipulator based on the Stewart mechanism was designed and constructed to perform spraying operations inside the greenhouse with the help of a manual end effector (mechanical robotic arm). In general, manually applied spraying does not spread evenly on all plants, resulting in increased toxic waste, there are also spraying labor costs in this method, so it is not economically viable. Hand spraying is a problem caused by direct contact with the toxin, which puts people in direct contact with chemicals at greater risk for a variety of diseases. Therefore, most of the toxic chemicals used to overcome weeds are a threat to humans and the environment. By poisoning the skin, mouth or breathing can be highly toxic.
Materials and Methods: The end effector sprayer is based on Stewart's mechanism and by using six degrees of freedom, allowing nozzles to spray at different angles on plants. For this purpose, six step motors were used to provide the rotational force of the operator's end effectors, which was launched with the Arduino system. In order to supply electrical energy, operator's end effectors and Arduino devices utilized a 500-watt computer power supply, calculating the dynamics and reverse kinematics of the Stewart platform, we specified unique codes for its rotation. In this study, inverse kinematics was used to obtain the position of the joints by knowing the position of the center the moving platform and connecting the connectors to the moving platform by the hinge joints, and to the actuators arm by the spherical joint. The dynamics of the actuator, the movement of the moving platform by the actuators was calculated. In this method, the direction of the moving platform the step motors are driven a time by the microcontroller in pairwise manner. Using arms and linkers, stepper motors could move the platform in three different angles. Due to the angle and radius of the arm's, the moving platform has an angle of 18 degrees to the horizon, which makes it able to spray directly into the target plant and make a same coating. Also the velocity and acceleration of the moving platform movement were calculated according to the rotational speed of the stepper motors the maximum velocity and linear acceleration of the moving platform are calculated 141 mm / s and 244mm/s2 respectively.
Results and Discussion: In order to accurately evaluate the performance of the sprayer, laboratory experiments were carried out to verify the performance of the control system and determine the height of spraying at different intervals. The end effector nozzle height was 117 cm above the ground, and the moving platform end effector with zero degree angle, and 18 degree spraying. It was determined that at a distance of 0.5 m 1 m and 1.5 m from the nozzle, the spraying heights were 100 cm, 57.7 cm and 12 cm accordingly. Based on this evaluation, spraying operation which was carried out at a distance of 0.5 m from the nozzle could reach highest level of spraying height. Finally, after modeling the end effector with solidworks software, it was simulated in the Adams software environment and by transferring the model to Adams, the force applied to the moving platform by the actuators, the velocity and acceleration of the moving platform were investigated. In the simulation, the applied force was evaluated by a pair of actuators on the moving platform, with the software output predicting the applied force correctly. In examining the linear velocity of the moving platform, the software output was about 5 cm/s more than the actual value and also in the simulation of linear platform moving acceleration, the software output was equal to the calculated value.
Conclusion: According to studies, this is the first time that the platform has been used in robotic sprinklers, and could be a reference for further research in the field due to its innovation. This end effector had no singularity at an angle of 0 to 18 degrees and in both directions, spraying had a 10% difference in spraying. According to the simulation results performed with Adams software, the amount of force applied by the propellers was linear on the moving platform. Moreover, according to the simulation results with the aforementioned software, the acceleration changes of the moving platform were also linear.