Flexible manufacturing for photonics device assembly

The assembly of photonics devices such as laser diodes, optical modulators, and opto-electronics multi-chip modules (OEMCM), usually requires the placement of micron size devices such as laser diodes, and sub-micron precision attachment between optical fibers and diodes or waveguide modulators (usually referred to as pigtailing). This is a very labor intensive process. Studies done by the opto-electronics (OE) industry have shown that 95 percent of the cost of a pigtailed photonic device is due to the use of manual alignment and bonding techniques, which is the current practice in industry. At Lawrence Livermore National Laboratory, we are working to reduce the cost of packaging OE devices through the use of automation. Our efforts are concentrated on several areas that are directly related to an automated process. This paper will focus on our progress in two of those areas, in particular, an automated fiber pigtailing machine and silicon micro-technology compatible with an automated process

Innovative mechanism to identify robot alignment in an automation system

Robotic applications are commonly used in industrial automation systems. Such systems are often comprised of a series of equipment, including robotic arms, conveyors, a workspace, and fixtures. While each piece of equipment may be calibrated with the highest precision, their alignment in relation to each other is an important issue in defining the accuracy of the system. Currently, a variety of complex automated and manual methods are used to align a robotic arm to a workspace. These methods often use either expensive equipment or are slow and skill-dependent. This paper presents a novel low-cost method for aligning an industrial robot to its workcell at 6 degrees of freedom (DoF). The solution is new, simple and easy to use and intended for the SMEs dealing with low volume, high complexity automated systems. The proposed method uses three dial indicators mounted to a robot end effector and a fixed measurement cube, positioned on a workcell. The robot is pre-programmed for a procedure around the cube. The changes on the dial indicators are used to calculate the misalignment between the robot and the workcell. Despite simplicity of the design, the solution is supported with complex real-time mathematical calculations and proven to identify and eliminate misalignment up to 3mm and 5 degrees to an accuracy of 0.003mm and 0.002 degrees: much higher than the precision required for a conventional industrial robot. In this article, the authors describe a proposed solution, validate the computation both theoretically and through a laboratory test rig and simulation

Simplified theodolite calibration for robot metrology

Theodolites represent a well-established three-dimensional-point-measuring technology. However, when used for robot applications they have to be properly calibrated to fulfil the necessary accuracy requirements. The theodolite calibration methods reported in the literature involve the use of costly sophisticated equipment not easily available to most users. Therefore, a new simplified calibration technique is presented based on the use of a graduated precision bar suspended freely to align with the vertical direction. To develop efficient mathematical models, the theodolites will be regarded as 2R open-ended mechanisms with the end-effector axis directed along the line of sight. The proposed models are then coded in a computer program designed to verify the validity of the technique presented. The simulation results will be presented at the end of the paper

A technique for the independent-axis calibration of robot manipulators with experimental verification

Accurate use of robots in an off-line programming mode is only possible through a proper calibration procedure. In this procedure, the end-effector is made to move along a set of known spatial poses where the positional errors are to be measured and employed in mathematical models. The models are subsequently solved for the manipulator dimensions (geometric parameters) using suitable regression techniques. Calibration is usually performed using either aggregate or independent-axis models. While the aggregate models result in all the system parameters being worked out simultaneously, the independent-axis models are meant to work out the geometric particulars of each joint-axis individually. In the present work, the independent-axis technique is used for the analysis with new mathematical models proposed to overcome the drawbacks of the existing methods. Moreover, the techniques employed here result in the prediction of transmission error functions and the modelling of the joint motion dependencies. This is a new concept in the field of robot calibration. Finally, the models proposed have been used to calibrate an ASEA IRB/L6 robot and the results are reported at the end of the paper

Development of a Robotic Positioning and Tracking System for a Research Laboratory

Measurement of residual stress using neutron or synchrotron diffraction relies on the accurate alignment of the sample in relation to the gauge volume of the instrument. Automatic sample alignment can be achieved using kinematic models of the positioning system provided the relevant kinematic parameters are known, or can be determined, to a suitable accuracy. The main problem addressed in this thesis is improving the repeatability and accuracy of the sample positioning for the strain scanning, through the use of techniques from robotic calibration theory to generate kinematic models of both off-the-shelf and custom-built positioning systems. The approach is illustrated using a positioning system in use on the ENGIN-X instrument at the UK’s ISIS pulsed neutron source comprising a traditional XYZΩ table augmented with a triple axis manipulator. Accuracies better than 100microns were achieved for this compound system. Although discussed here in terms of sample positioning systems these methods are entirely applicable to other moving instrument components such as beam shaping jaws and detectors. Several factors could lead to inaccurate positioning on a neutron or synchrotron diffractometer. It is therefore essential to validate the accuracy of positioning especially during experiments which require a high level of accuracy. In this thesis, a stereo camera system is developed to monitor the sample and other moving parts of the diffractometer. The camera metrology system is designed to measure the positions of retroreflective markers attached to any object that is being monitored. A fully automated camera calibration procedure is developed with an emphasis on accuracy. The potential accuracy of this system is demonstrated and problems that limit accuracy are discussed. It is anticipated that the camera system would be used to correct the positioning system when the error is minimal or notify the user of the error when it is significant