Kinematics and statics analysis of a novle 4-dof parallel mechanism for laser weeding robot

To eliminate the serious threat of weeds to farmland crops, this study proposes a laser weeding robot based on a novel 3UPS-RPU parallel mechanism (PM). The robot uses laser thermal effects to eliminate weeds in crop rows. The novel 3UPS-RPU PM is composed of three UPS-type active legs and one RPU-type active leg. Approaches for solving the inverse kinematics, inverse/forward velocities, inverse/forward accelerations, active forces, and constrained forces of this PM are derived and unified for other PMs with linear active legs. The kinematic curves demonstrate that the input of active legs 1 and 3 are consistent, while the moving platform moves according to a line-type translational movement which is the unique characteristic of the proposed PM. The active legs move according to a non-linear motion law, while the moving platform of the PM moves according to a line-type patterns, which is a common characteristic. The kinematic curves show that this PM has steady movement with no sudden changes or breakpoints which satisfies the stability requirements for the laser in the robot. Theoretical formulas and results provide a basis for the optimization of the structure design, control, dynamic performance analysis, manufacturing, and applications of the 3UPS-RPU PM.