Integrated optical position and orientation sensing for manufacturing robotics

The aim of this proposal is to undertake research into novel optical instrumentation to improve the precision of traditional robot-based manufacturing operations and to support future manufacturing aims for more agile and flexible manufacturing systems. This will be achieved by building upon our current research, in which we have developed two complimentary techniques for robotic positioning measurement; range-resolved interferometry (RRI) and laser speckle pattern correlation (LSC).

In this proposal we aim to further develop this novel instrumentation, to provide new measurement and in-process monitoring capabilities and to improve significantly the performance via this additional functionality, together with concomitant exploration of new application areas in robotics and automation, laser processing and additive manufacturing via project collaborators. This will enable improved robot performance, extend the applicability of flexible robots in high-precision manufacturing processes, and improve productivity through on-line quality control.

To achieve this we have identified a number of the most promising directions which require further research to bring the techniques to an appropriate level for exploitation: The first is to enable robot orientation measurements by the measurement of out-of-plane tilt (pitch and roll) angles, in addition to the positioning (x, y, z) currently implemented. This will enable a range of new application areas including maintaining range and normal measurements to the part during robotic non-destructive testing and orientation and movement control during machining operations. Similarly in air-frame manufacturing maintaining orthogonality in hole drilling operations is critical to the quality of rivet/fastening holes used to ensure fatigue lifetime and surface smoothness and hence aerodynamic performance.

In addition to this, the miniaturisation of the sensors will be investigated via the application of optical fibre sensor heads to allow remote positioning, to enable a range of new robotic manufacturing applications. For example applications requiring measurements to be made close to the interaction point, for ease of retro-fitting on existing machine tools and for additional robustness and flexibility in that the instrument can be located further from causes of potential damage in robotic machining or processing.

The final area to be investigated is the integration of the instrumentation with laser processing heads. This will enable the use of the sensors in new application areas in robotic laser processing, such as laser based additive manufacturing, in which there is a need for on-line process monitoring such as deposition layer height measurements and control of disturbances during deposition. Or in laser cutting, where control of the focus position relative to the work-piece is critical to ensure cut quality, and to enable rapid processing on thin sheets in the presence of out-of-plane vibrations. The integration of the instruments constructed with the processing laser will result in a novel flexible instrument capable of up to 5 degree-of-freedom positioning and/or cut/ablation depth monitoring, something currently unavailable with existing technologies.

This proposal seeks to underpin the development of new industrial, manufacturing and automation systems by providing new sensors and instrumentation to enable measurements that are currently not possible or difficult or expensive to make.

There are many applications in robotic manufacturing and automation, where the use or adoption of robots is limited by the performance of the robots either due to deflections resulting from low mechanical stiffness of the robots and process or machining forces, or inaccuracies in the robots position and orientation not captured by the kinematic models used to determine end-effector position. It is this challenge which the instruments constructed under this grant seeks to address by providing a new means of measuring the position and orientation of manufacturing robots.

The potential impacts are both academic and economic. Initially potential impacts are likely to be academic in nature, providing new knowledge about how to implement the new sensing techniques, followed by uptake of the sensors among researchers investigating robotic manufacturing and automation tasks using the insight provided by the new sensors.

Secondly, economic impact may be possible by enabling new manufacturing and automation systems for UK businesses to reduce costs, improve quality and increase productivity. For example, the ability to automate non-destructive testing using robotics will lead to less down-time and greater productivity, while applying the sensors to improve positioning performance will enable the use of lower cost robots and/or improve part quality. Finally, the further development of the instruments into products may provide economic impact both in their use, and in supporting the sensors and instrumentation industry in the UK.