Kinematic and Dynamic Analysis of a Six-Bar Aerial Gripper Mechanism

Abstract

AbstractUnmanned aerial vehicles (UAV) are being used for commercial and rescue operations. A gripper attached to the UAV would help in grasping, holding and placing the object of interest during these operations. In this work, we propose and analyze one degree of freedom gripper mechanism that has six links and seven revolute joints. The kinematic analysis is done by treating the gripper mechanism as two four-bar mechanisms that form two loops. A two-stage vector loop method is used to determine the joint angles. In order to statically balance the gripper mechanism, the coordinates of all the joints in the mechanism at various positions of the links are found out. The method of principal vectors is used for the complete balancing of the mechanism. In this method, each vector is directed along with one of the links, and the position of the center of mass of the entire mechanism is given by the addition of these vectors in series. The coefficients of these principal vectors are determined by summing the mass-weighted position vector of every center of mass of the link. Counterweights are added to the links for statico-dynamic balancing of the gripper mechanism. The dynamic analysis is done using the Newtonian solution method. There are 15 equations with 15 unknown contact forces and torque acting in the gripper mechanism. Solving these equations, we obtain the forces acting on the links, and torque required for driving the gripper mechanism. The gripper mechanism was then modeled using a CAD software. It was fabricated by 3D printing the parts and assembling them together. The gripper was finally mounted below a hexacopter and tested in the outdoor environment by carrying and dropping a spherical object.KeywordsAerial gripperGripper mechanismSix-bar mechanismUnmanned aerial vehiclesBalancingGripper kinematicsGripper dynamics