School of Mechanical Engineering, Sharif University of Technology Azadi Ave, Tehran, Iran
Center of Excellence in Design, Robotics and Automation (CEDRA), Sharif University of Technology Azadi Ave, Tehran, Iran
A parallel mechanism was designed and developed to perform tasks with micro meter accuracy within millimeter-range workspace. The system employs two Stewart platforms; while squiggle motors were used in one of the platforms to provide larger workspace, the second platform which uses piezoelectric actuators accurately positions the tool tip in the desired point. Error model for tool tip was developed for the first platform. Considering worst case scenario and using Particle Swarm Optimization algorithm, positioning error of the first platform was evaluated numerically throughout the respective workspace, upon which the design of the fine tuning piezo driven second stage was carried out. Positioning error and workspace of the whole system was evaluated. Using a single-deck platform with squiggle motors caused 40 micrometers positioning error while application of the fine-tuning piezo-driven Stewart platform reduced the total positioning error to 10 micrometers.