Structure Design And Performance Analysis On A Novel3-RRR Spherical Parallel Manipulator

In human daily life, there are many applications where a whirling motion is needed. To meet such needs, the dissertation was concentrated on some robot can achieve that function, which is called3-RRR Spherical Parallel Manipulator (SPM). The main content of the dissertation can be summarized into6parts, including structure design, kinematics, dynamics, path planning, robust control and prototype experiments.At first, the Least Interference Design Methodology (LIDeM) was established to optimize the workspace of the robot with least mechanical interference. Based on this theory, a novel structure of3-RRR SPM, namely Triaster, was designed and built up. With its kinematics formulas, the singularity loci and interference distribution were attatined via3D spherical plots. Its inverse kinematic equation was derived, based on which Time-Interval-Proportional Extension (TIPE) strategy was raised up to insure the trajectory of Triaster’s end effector unchanged when the accelerations of input motors are adjusted to meet the system requirements. The forward kinematic problem of the robot was also solved in the dissertation. Under all the reachable configurations of Triaster, the author found the angular displacements of three input motors should be matched in a range. The phenomenum was explained by some plots of angular displacements, velocities and accelerations of input motors, and some trajectory plots of its end effector. The rubberband algorithm was applied to solve the path planning of Triaster, and was proved to be feasible by4sets of testing datum. The shortest path projections were gained, which are from Riemann spherical space into Euclidian orthogonal space. For avoiding the drawbacks of Newtown method, which are too many intermediate variables and equations produced during the process, and which leads to manually unsolvable, and thus the Hamilton-Lagrangian dynamics method was adopted. The inertia, centroid and mass of each moving component of Triaster were calculated. With these parameters, the kinetic and potential energy of the robot at any moment was attained through the formulas. The relations between input torques and end effector motions were given by their plots. Each input motor power plot which is as a function of time was also given in the dissertation. There are many uncertainties in the robotic system, like friction in each joint. Focused on this uncertainty, the robust control method for the trajectory stability of Triaster was studied. The status space formula of the system was constructed and based on which the Lyapunov stability was analyzed. Accordingly, a specific robust controller was designed. With uncertain friction and robust controller impacted, the trajectory plot of Triaster’s end effector was presented. In the end, for proving all these theorical things, an experiment prototyple of Triaster was built up. It connected Triaster robot body, circuit board for motor controlling, language programming software on PC and image caputure module all together. The control programs were written and burned into the circuit board to drive the motors to some expected positions. The images results of the trajectories were captured by the module. The entire image datum were analyzed and compared with the theoretical results, based on which some suggestions was given for future research.The achievements obtained in this desertation will be helpful for the application and further research for3-RRR Spherical Parallel Manipulator.