Structure Optimization and Path Planning of Tomato Picking Manipulator

In order to improve adaptability of manipulator to automatic harvesting under the unstructured environment, a new tomato planting pattern and a picking manipulator structure form were designed based on biological characteristics, cultivation modes and engraftment features of tomato. After simplified fruits growth space of tomato from cuboid to rectangle equivalently, structure optimization mathematical models of manipulator were established by taking the area of workspace as objective function and the periphery of workspace as constrains function. Based on the models and the optimization toolbox of MATLAB, structure parameters of tomato picking manipulator were optimized and its simulation of workspace by Monte-Carlo method was conducted. The results showed that 4 degree of freedom (DOF) manipulator was able to meet the requirements of tomato harvesting and rationality of optimization parameters was verified. According to the optimized parameters, 4 basic working postures of tomato picking manipulator were designed. Based on cycloid trajectory algorithm, a collision-free and efficient path was planned as fallow: picking preparation posture move to picking posture combining two cycloid trajectories, and picking posture move to fruit releasing posture using two separate movements which were firstly rotating shoulder, elbow and wrist joints and then rotating waist joint. Simulation of the path based on MATLAB was realized, results showed that the planned path was able to avoid collision between tomato picking manipulator and obstacles (e.g. stems, leaves or other fruits) efficiently.