Modeling, control design and mechatronic implementation of constrained robots for surface finishing applications

摘要

Scope and method of study. This dissertation focuses on modeling, control design, and mechatronic implementation of constrained robots. This research can find applications in robotic tasks that involve transition motion. Focused application includes robotic surface finishing operations such as deburring, grinding, chamfering and polishing. A dynamic model that describes the dynamic behavior of a robot performing complete tasks is developed. A complete robot task is divided into three phases (unconstrained motion phase, transition phase, and constrained motion phase) depending on the location of the robot end-effector with respect to the constraint surface. A discontinuous control scheme is proposed for a complete task where emphasis is given to control design in the transition phase and constrained motion phase. A transition control algorithm robust to impact force and constraint uncertainties has been developed. Position/force control scheme that is capable of tracking the desired trajectory tangential to the constraint surface and regulating the force normal to the constraint surface is investigated. A tangential force feed-forward term is used to compensate for friction and/or cutting force. An on-line adaptation law is developed to estimate the coefficient relating the normal force and the tangential force. Findings and conclusions. An open architecture experimental platform has been developed for surface finishing applications with optimal integration of system components via a mechatronic approach. The system consists of a two-link direct drive manipulator, three-processor real-time controller, force/torque sensor, robotic deburring tool, and work piece fixture. Different controller implementation modes are compared with emphasis on data communication between processors and data filtering. Extensive experiments have been conducted on the developed experimental platform to test the proposed discontinuous control scheme and compare different controller implementation modes. Experimental results confirm the effectiveness of the proposed control strategy and mechatronic design approach.