Investigation on clamping and climbing mechanisms for the design of semi autonomous areca palm climber

Abstract

Palms are un-branched evergreen trees cultivated mainly for its nuts and one has to climb up the tree for harvesting and other operations like spraying. Considering the difficulty and drudgery involved in this operation different types climbers were developed by researchers and innovators. These climbers essentially consist of two functional mechanisms; the clamping mechanism for gripping the unit to the trunk and climbing mechanism for vertical movement of unit. These developed palm climbers can be categorized based on the type of motion of the unit as continuous, discrete or serpentine and based on the power utilized for actuating the functional components as mechanical or robotic. Further categorization can be done based on the mechanism deployed for the actuating functional components. The biometric properties of areca palm are important for the design optimization and performance of climber. Among the quantifiable biometric properties diameter, variation of diameter along height, height and tilt angle were identified as the critical properties which has direct influence on design and operations. The diameter of areca palm determines the size of gripping unit, shape and dimensions of gripping arms or structures, their spacing and the distance through which the gripping arms are to be moved for locking and unlocking. Tilt angle is critical in optimizing the height of the climbing unit and the maximum relative movement of functional sets of components. The height of palm does not directly influence the design of the climber; it is a major parameter which affects the operation of the robotic climbers. The time required for completing the climbing is directly influenced by the height and when height increases, it will be difficult to see and operate the climber from the ground. By analyzing all these data and the past works related to mechanical and robotic climbers, their suitability and merits and demerits, a preliminary model of semi-autonomous areca palm climber was fabricated. The principle of linear actuators was adapted for the design of the climber by incorporating power screw rods and DC motors. The designed climber has two components, one was gripping unit which will provide to and fro motion to the gripping arms hence the arms grabs the tree. Another component was climbing unit which will provide up and down movement hence the climbing happens. At the beginning, the power was supplied to the lower gripping unit; by the movement of both the arms it grabs/holds the tree. Then the power was supplied to the upper gripping unit. By that both the gripping units grabs the tree trunk tightly. After that, the lower arm releases the contact and moves up by the rotation of main motor. Then lower arm holds the tree trunk, upper arm releases and moves up. This process continues until the desirable height was reached. The arms hold the entire body during climbing. During climbing part of robot was always fixed to the tree trunk. The operation of robot was controlled by wired remote controller. The prototype can be simply installed and controlled on the palm by an inexperienced operator. The device has been tested for its performance and found safe, reliable, and efficient and also reduces the problems in climbing of arecanut tree to a good extend.