Artificial Intelligence in Foreign Object Classification in Fenceless Robotic Work Cells Using 2-D Safety Cameras

Production systems using robotic manipulators have become common in the last few decades, and the trend is towards fenceless cells that save from space. Thus, the safety and flexibility of these systems have become more critical. The safety systems are based on either sensor data or camera images. Although the flexibility of the camera-based systems is better, conventional image processing methods are sensitive to the working environment. Artificial intelligence may be a powerful tool for them to adapt to change requirements quickly and improve accuracy and stability. In this study, a low-cost 2-D camera-based safety system was designed and installed in an experimental fenceless robotic work cell. The system controller was coupled with three alternative deep learning (ResNet-152, AlexNet, SqueezeNet) and three machine learning modules (support vector machine, random forest and decision tree). These modules were trained using photo images of ten distinct foreign objects penetrating the alarm zone. To include the ever-changing conditions of the industrial environment, disruptive effects including camera vibrations, shadows, reflections, illuminance variations etc. are included by using multiple images up to 550 for each class. Using the restricted data used for training and testing the six systems, the SqueezeNet deep learning model gave the best accuracy of 95% without any over-fitting. Despite this, machine learning-based models have been found to have 100 times faster prediction time than deep learning-based ones. Thus, the safety system can be adapted quickly to any possible changes and noise that may arise from working conditions is prevented, and time losses that may occur in industrial production may be prevented

Effects of process parameters and tool wear on the fatigue life of machined threaded parts

Talaş kaldırılarak tornada açılmış vidalı parçaların yorulma dayanımına imal faktörleri ve koşullarının etkileri, vida diş formundaki çentikli numunelerin yorulma dayanımları ile karşılaştırılarak araştırılmıştır. Vida açmada kesme hızının, radyal ilerlemenin, takım aşınmasının ve iki farklı kesme şemasının vidalı numunenin yorulma dayanımına etkileri bulunmuştur. Deneylerde vidalı numunelerin yorulma dayanımları aynı formdaki çentikli numuneye göre imal faktörlerine bağlı olarak geniş bir dağılım göstermiştir. Vidalı numunenin yorulma dayanımının imal faktörlerine önemli derecede bağlı olduğu ve çentikli numunenin vidayı temsil etmediği görülmüştür. Vidalı numunenin yorulma dayanımında en fazla takım aşınmasının ve kesme hızının daha düşük oranlarda ise kesme şemasının ve radyal ilerlemenin etkili olduğu görülmüştür.  Anahtar Kelimeler: Vida kesme, yorulma, takım aşınması. The effect of the machining parameters on the fatigue life of the threaded parts manufactured by machining were investigated comparing with the endurance limits of same size fine machined notched specimens. To machine precise specimens, rigidity of a universal lathe was improved by an additional slide system, and the final rigidity was measured to make sure of the tight dimensional tolerances. An R. R. Moore four point rotary bending fatigue test machine was designed, manufactured and calibrated. All the specimens were machined from AISI 4340 steel. In both thread and notch machining, uncoated %78 WC, %14 TiC and %8 Co API special tapered pipe thread tools were used. The effects of the cutting force, radial feed, tool wear and two thread cutting feeding methods on the fatigue life of the threaded specimens were determined. Experimental results show that fatigue lives of threaded specimens lie on a large range depending on machining conditions as compared to notched specimens, and thus, notched specimens do not represent fatigue behavior of threaded specimens. According to the experimental results, the most important factors effecting fatigue life of threaded specimens were found to be tool wear and cutting velocity and the effects of the different feeding methods and radial feed were found less significant. Keywords: Thread machining, fatigue, tool wear.

Design and Validation of a Camera-Based Safety System for Fenceless Robotic Work Cells

A two-dimensional (2-D) camera system with a real-time image processing-based safety technology is a cost-effective alternative that needs optimization of the cell layout, the number of cameras, and the camera’s locations and orientations. A design optimization study was performed using the multi-criteria linear fractional programming method and considering the number of cameras, the resolution, as well as camera positions and orientations. A table-top experimental setup was designed and built to test the effectiveness of the optimized design using two cameras. The designs at optimal and nonoptimal parameters were compared using a deep learning algorithm, ResNet-152. To eliminate blind spots, a simple but novel 2-D image merging technique was proposed as an alternative to commonly employed stereo imaging methods. Verification experiments were conducted by using two camera resolutions with two graphic processors under varying illuminance. It was validated that high-speed entrances to the safety system were detected reliably and with a 0.1 s response time. Moreover, the system was proven to work effectively at a minimum illuminance of 120 lux, while commercial systems cannot be operated under 400 lux. After determining the most appropriate 2-D camera type, positions, and angles within the international standards, the most cost-effective solution set with a performance-to-price ratio up to 15 times higher than high-cost 3-D camera systems was proposed and validated

Effects of sheet thickness and anisotropy on forming limit curves of AA2024-T4

WOS: 000322326300060In this study, the effects of sheet thickness and anisotropy of AA2024-T4 on forming limit curve (FLC) are experimentally investigated according to ISO 12004-2 standard. A new limit strain measurement method is proposed by using the grid analysis method so as to determine limit strains conveniently and reliably. In addition to the regular test specimens, various widths are added to enhance the FLC's accuracy at the plane strain condition (PSC). The accuracy and reliability of the proposed method are verified for different materials. Results illustrate that an increase in the sheet thickness increases the FLC level. The additional experiments for additional widths improve the accuracy of the FLC at the PSC, and the position of the lowest major strain value differs from the literature. However, the effect of anisotropy on the FLC is found to be insignificant. Finally, experimental and numerical case studies are carried out for conventional deep drawing, stretch drawing, and hydraulic bulge processes. Results reveal that different FLCs are necessary for different thicknesses for accurate predictions.Scientific and Technological Research Council of Turkey (TUBITAK) [108M516]; Research Project Office (BAP) of Necmettin Erbakan University; Research Project Office (BAP) of Selcuk UniversityThis work was supported by The Scientific and Technological Research Council of Turkey (TUBITAK; Grant number 108M516). It was also supported by the Research Project Offices (BAP) of Necmettin Erbakan and Selcuk Universities. TUBITAK, The Research Project Offices, Metal Forming Laboratory at the Nigde University, and Metal Forming Center of Excellence at the Atilim University are profoundly acknowledged. This work has been extracted from Murat Dilmec's PhD thesis