The EU’s co-funded COMET project, which seeks to improve the efficiency of European industrial manufacturing, is creating a revolutionary solution that enables robots to perform high-end machining. Robots of any brand fitted with the COMET plug-and-produce controller unit successfully respond to manufacturing needs for cost-effective, flexible, and reliable manufacturing solutions.
Nikon Metrology is a main contractor working to develop a tracking system to detect deviations from the programmed robot path. These are used to initiate real-time tool path corrections to maintain the targeted accuracy throughout the entire machining sequence. The proposed COMET solution will be, on average, 30-percent more cost-effective than dedicated machine tools, while delivering absolute positional accuracy at better than 50 microns.
To remain competitive, high-end manufacturing companies in Europe are looking for accurate, reliable, and maintenance-free machine tools that offer fast changeover, programming, and setup. Industrial robot technology could provide an excellent base for machining because it is flexible and affordable. The COMET plug-and-produce controller is a modular system that fits most robot brands, including ABB, Fanuc, and KUKA.
Combined with enabling metrology solutions, industrial robots offer distinct advantages over expensive specialty equipment designed for specific machining tasks. As part of the COMET project, Nikon Metrology is responsible for developing an adaptive tracking system that helps adjust real-time robot arm positioning in relation to where it should be according to the initial programmed robot path.
The adaptive tracking system tracks the location of the robot head in real time and feeds back the metrology data using a closed feedback loop via the controller. This metrology-adjusted process increases robot accuracy because it nearly eliminates the influence of robot warm-up, drift, and backlash. It underlines the importance of the adaptive tracking system in transforming industrial robots into precision tools for milling, deburring, and other machining applications. There is high demand for such robots in aerospace and automotive markets as well as for manufacturers involved with mold and die and high-precision parts.
The COMET robot-control system also allows modules other than the adaptive tracking system to be plugged in. The other modules focus on kinematic and dynamic models to set up a unique robot fingerprint, holistic programming and simulation environment, and a high-dynamics compensation mechanism to eliminate remaining positional errors.
The adaptive tracking system module consists of two components: the tracking system and the comparison and path adaptation module. Most of the available tracking systems are not suitable for use in the COMET project, considering both technical and economic system aspects. Based on specific project needs, the tracking system research will start from the K-Series Optical CMM (coordinate measuring machine) from Nikon Metrology.
K-Series’ pre-calibrated, solid state camera system consists of three linear, built-in CCD cameras. With cylindrical lenses on all cameras and the middle camera tilted 90°, the optical CMM measures the locations of infrared light LEDs mounted on the robot head. Because an LED is located where the three CCD observatory planes intersect at the instance of capture, the system is able to determine the point coordinates based on the plane inclination angles. The K-Series system offers the means to track multiple LEDs simultaneously with six degrees of freedom at a sample rate up to 1,000 Hz to allow for dynamic measurements.
The module for the corrective adaptation continuously compares the measured position, speed, and acceleration with the corresponding data in the part program. A model-based algorithm will then decide when and how to adjust robot operation to meet the accuracy required by the machining process. Development efforts from Nikon Metrology engineers concentrate on measuring accuracy, system latency, and module interfacing to obtain precise and prompt robot-motion adaptations.
Industrial robots’ flexibility and cost-efficiency is utilized by adding absolute position accuracy as well as a plug-and-produce software environment to design, program, simulate, and execute high-end machining processes. New innovative tracking components and modular information communication technology (ICT) methods are being developed to open new application areas for industrial robots. These components and methods can be plugged in the modular COMET plug-and-produce platform, ready for use with any industrial robot cell.
The 30-month COMET project began in September 2010, and currently progresses as planned. After completing the COMET plug-and-produce robot controller, Nikon Metrology will act as a partner in exploiting the project results. Nikon’s Metrology Integrated Robotics Center of Excellence will play a pivotal role for customers and robot cell-integration companies.
The Comet project involves 14 technical partners from eight countries across Europe, coordinated by UK-based manufacturing software specialists Delcam. For more news and regular updates, check out www.cometproject.eu or follow the project’s developments live on the project’s Twitter account (@Comet_project).