Background
Industrial robotic manipulators are highly precise and adaptable but have limited reach. For decades, coordinated motion between manipulators and external axes—fixed-location rails or gantries—has been the most common solution to expand reach. While coordinated motion between industrial manipulators and mobile platforms would be more flexible and less expensive, the infrastructure needed to support robust integration has not been available. When systems include both a manipulator and a mobile base, they either operate in a stop-and-go fashion, use complex and expensive hardware, or require external monitoring infrastructure. Several recently developed technologies may, together, enable a navigation and manipulator planning framework where true coordinated motion is possible. This project aims to explore the viability of a coordinated motion platform, free of external infrastructure, and assess its performance against process constraints in applications where continuous processing is necessary, such as sealing or structural welding.
Approach
This project investigates methods for continuous-process tasks where the complete kinematic solution of a coupled mobile base and manipulator is highly valuable. We aim to achieve high-frequency control and command of both the robot and mobile base. Full coordinated motion requires the mobile base to not only correct errors in its movement but also to consider the manipulator’s workspace and move such that the target will always remain within reach of the end-effector. We implemented the coupled kinematic solution to integrate with the Tesseract framework and supplemented it with several techniques to mitigate hypothesized deficiencies. We also integrated motion planning libraries developed in previous internal research and development (IR&D) projects, including a recent targeted IR&D (10-R6208) that investigated real-time optimization-based path planning. This planner will be run in real-time to replan motion planning during execution to account for remaining errors in the mobile base. Process accuracy will be measured using a high-resolution motion capture system.
Accomplishments
We designed and implemented a coordinated motion planning software library that is responsive to changes in simulation and is undergoing testing with hardware. We have successfully integrated a commercially available industrial manipulator and mobile base that can be controlled as a single motion planning unit. As a result of this project’s success, we filed an invention disclosure for this software framework and gained substantial knowledge about these systems and the limitations of their open-source drivers. We successfully executed planned motions simultaneously on both systems, including feedback and dynamic re-planning. This initially resulted in considerable instability, but further testing and fine-tuning during a project extension allowed us to execute stable motions with less than 5 mm of error.