Novel optical instrumentation for robotic manufacturing

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The aim of this proposal is to undertake research into novel optical instrumentation to support future manufacturing aims for more agile and flexible manufacturing systems as well as to improve precision of traditional robot-based manufacturing operations. New optical instrumentation will be developed combining two complimentary optical measurements techniques, range-resolved interferometry and laser speckle pattern correlation. These will be capable of remote, high quality and high-bandwidth measurements of the relative motion and orientation between a robotic end-effector mounted sensor and the workpiece, cumulating in a combined multi-parameter sensor.The applications of these sensors are common to many areas of manufacturing and can be grouped into three main areas:i) The stabilisation and control of the end-effector relative to the workpiece.ii) Motion tracking to lock the robot to a moving assembly line.iii) Relative positioning operations. In these application areas there is a need for new effective, low cost instrumentation to provide real-time feedback about their relative motion and orientations, which this proposal will attempt to address.In the first application area, the stabilisation and control of a tool's motion, positioning and orientation is required in the presence of end-effector and/or workpiece vibrations. For example contact tasks such as polishing, drilling, and riveting are often challenging tasks due to the comparatively low mechanical stiffness of typical industrial robots. This can result in excessive tool-tip deflection, vibration, and resulting poor quality of the finished part. Other methods of monitoring the motion suffer from limitations; vision systems can have limited update rates, whilst laser scanning/tracking systems are expensive and inflexible in that the scanning system needs to be mounted externally to the robot and maintain a line-of-sight.The motion tracking of robotic manipulators to follow moving assembly lines is an important application in many manufacturing operations. Currently vision-systems can provide a flexible sensor capable of determining the relative position and orientation of objects to good precision, but their slow update rate and latency make them unsuitable for many feedback loops for real-time motion control. In addition, these visual systems sometimes require visual markers or beacons for operation and unless the cameras are mounted directly on the end-effector, the field-of-view can sometimes be obscured towards the end of the manoeuvring operation, at the point where control is most critical.Finally, in the area of relative positioning many applications require high accuracy relative to a reference and this makes the adoption of standard robots difficult. For example, in airframe manufacturing the high accuracies of between 0.2 mm and 0.02 mm relative to a local reference a few meters away are required for drilling, fettling and component location operations and in remote laser cutting there is a requirement for high precision in the positioning of the cutting beam between scans, with any misalignment leading to multiple grooves and failure to cut the workpiece. Here laser speckle correlation may offer a solution with the proposed sensors capable of precise relative positioning between the end-effector and workpiece (potentially down to <1 micron in mm's and <50 micron in m's) while relying on other means, such as the robot encoders or vision systems, to reference to an absolute position.