Gökhan Alcan
Assistant Professor
Tampere University
Conference Papers
Robust Hovering Control of a Quadrotor using Acceleration Feedback
Abstract
This paper presents a novel acceleration feedback control method for robust hovering of a quadrotor subject to aerodynamic disturbances. An acceleration based disturbance observer (ABDOB) is designed to reject disturbances acting on the positional dynamics of the quadrotor. In order to provide high stiffness against disturbances acting on the attitude dynamics, a nested position, velocity and inner acceleration feedback control structure that utilizes PID and PI type controllers is developed. To obtain reliable angular acceleration information, a cascaded estimation technique based on an extended Kalman filter (EKF) and a classical Kalman filter (KF) is proposed. EKF estimates the Euler angles and gyro biases by fusing the data from gyroscope, accelerometer and magnetometer. Compensated gyro data are then fed into a Kalman filter whose process model is derived from Taylor series expansion of angular velocities and accelerations where angular jerks are considered as stochastic inputs. The well-known kinematic relation between Euler angular rates and angular velocities is employed to estimate reliable Euler accelerations. Estimated Euler angles, rates and accelerations are then used as feedback signals in the nested attitude control structure. Performance of the proposed method is assessed by a high fidelity simulation model where uncertainties in the sensor measurements, e.g. sensor bias and noise, are also considered. Developed controllers that utilize estimated acceleration feedback provide extremely robust hovering results when the quadrotor is subject to wind gusts generated by Dryden wind model. Simulation results show that utilization of acceleration feedback in hovering control significantly reduces the deviations in the x-y position of the quadrotor.
BibTeX
@inproceedings{alcan2017robust,
title={Robust hovering control of a quadrotor using acceleration feedback},
author={Alcan, Gokhan and Unel, Mustafa},
booktitle={2017 International Conference on Unmanned Aircraft Systems (ICUAS)},
pages={1455--1462},
year={2017},
organization={IEEE}
}
Design, Prototyping and Control of a Flexible Cystoscope for Biomedical Applications
Abstract
Kidney stone and prostate hyperplasia are very common urogenital diseases all over the world. To treat these diseases, one of the ESWL (Extracorporeal Shock Wave Lithotripsy), PCNL (Percutaneous Nephrolithotomy), cystoscopes or open surgery techniques can be used. Cystoscopes named devices are used for in-vivo intervention. A flexible or rigid cystoscope device is inserted into human body and operates on interested area. In this study, a flexible cystoscope prototype has been developed. The prototype is able to bend up to ±40°in X and Y axes, has a hydrodynamic cavitation probe for rounding sharp edges of kidney stone or resection of the filled prostate with hydrodynamic cavitation method and contains a waterproof medical camera to give visual feedback to the operator. The operator steers the flexible end-effector via joystick toward target region. This paper presents design, manufacturing, control and experimental setup of the tendon driven flexible cystoscope prototype. The prototype is 10 mm in outer diameter, 70 mm in flexible part only and 120 mm in total length with flexible part and rigid tube. The experimental results show that the prototype bending mechanism, control system, manufactured prototype parts and experimental setup function properly. A small piece of real kidney stone was broken in targeted area.
BibTeX
@inproceedings{sozer2017design,
title={Design, prototyping and control of a flexible cystoscope for biomedical applications},
author={Sozer, Canberk and Ghorbani, Morteza and Alcan, Gokhan and Uvet, Huseyin and Unel, Mustafa and Kosar, Ali},
booktitle={IOP Conference Series: Materials Science and Engineering},
volume={224},
number={1},
pages={012050},
year={2017},
organization={IOP Publishing}
}
Single Droplet Tracking in Jet Flow
Lecture Notes in Computer Science, Volume 9730, Pages 415-422
Abstract
Fluid systems such as the multiphase flow and the jet flow usually involve droplets and/or bubbles whose morphological properties can provide important clues about the underlying phenomena. In this paper, we develop a new visual tracking method to track the evolution of single droplets in the jet flow. Shape and motion features of the detected droplets are fused and Bhattacharyya distance is employed to find the closest droplet among possible candidates in consecutive frames. Shapes of the droplets are not assumed to be circles or ellipses during segmentation process, which utilizes morphological operations and thresholding. The evolution of single droplets in the jet flow were monitored via Particle Shadow Sizing (PSS) technique where they were tracked with 86 % average accuracy and 15 fps real-time performance.
Keywords
- Jet flow
- Droplet
- Bubble
- Morphology
- Segmentation
- Tracking
- Bhattacharyya distance
BibTeX
@inproceedings{alcan2016single,
title={Single droplet tracking in jet flow},
author={Alcan, Gokhan and Ghorbani, Morteza and Kosar, A and Unel, M},
booktitle={Lecture Notes in Computer Science},
volume={9730},
pages={415--422},
year={2016},
publisher={Springer}
}
Visualization and Image Processing of Spray Structure Under the Effect of Cavitation Phenomenon
Journal of Physics: Conference Series, Volume 656, Article Number: 012115
Abstract
This paper presents visualization and image processing of spray structure affected by cavitation bubbles and cavitating flow patterns. Experiments were conducted for a better understanding of cavitation and resulting flow regimes. Cavitation is generated with sudden pressure drop across a 4.5 mm long short micro-channel with an inner diameter of 152 μm connected to the setup using proper fittings. Generated cavitation bubbles and fluid flow patterns were observed by using a high speed camera. The spray structure was observed in four different segments and mainly the droplet evaluation in the lower segments for low upstream pressures was analyzed using several image processing techniques including contrast adjustments and morphological operators. Moreover, fluid flow regimes for different upstream pressures were investigated, and the flow patterns were analyzed in the separated regions of the spray.
BibTeX
@inproceedings{ghorbani2015visualization,
title={Visualization and image processing of spray structure under the effect of cavitation phenomenon},
author={Ghorbani, Morteza and Alcan, Gokhan and Yilmaz, D and Unel, M and Kosar, A},
booktitle={Journal of Physics: Conference Series},
volume={656},
number={1},
pages={012115},
year={2015},
organization={IOP Publishing}
}
Vision Based Cone Angle Estimation of Bubbly Cavitating Flow and Analysis of Scattered Bubbles Using Micro Imaging Techniques
Abstract
Hydrodynamic cavitation is an effective and alternative treatment method in various biomedical applications such as kidney stone erosion, ablation of benign prostatic hyperplasia tissues and annihilation of detrimental cells. In order to effectively position the orifice of bubbly cavitating flow generator towards the target and control the destructive cavitation effect, cone angle of multi-phase bubbly flow and distributions of scattered bubble swarms around main flow must be determined. This paper presents two vision based solutions to determine these quantities. 3D Gaussian modeling of multi-phase flow and edge slopes of cross-section are used to estimate the cone angle in a Kalman filter framework. Scattered bubble swarm distributions around main flow were assumed as a normal distribution and analyzed with the help of covariance matrix of the bubble position data. Hydrodynamical cavitating bubbles were generated from 0.45 cm long micro probe with 152μm inner diameter under 10 to 120 bars pressures and monitored via Particle Shadow Sizing technique. Proposed methods enabled to quantize the increasing inlet pressure effect on bubbly cavitating multi-phase flow.
BibTeX
@inproceedings{alcan2015vision,
title={Vision based cone angle estimation of bubbly cavitating flow and analysis of scattered bubbles using micro imaging techniques},
author={Alcan, Gokhan and Ghorbani, Morteza and Kosar, Ali and Unel, Mustafa},
booktitle={IECON 2015-41st Annual Conference of the IEEE Industrial Electronics Society},
pages={003473--003474},
year={2015},
organization={IEEE}
}