Limits...
Afocal optical flow sensor for reducing vertical height sensitivity in indoor robot localization and navigation.

Yi DH, Lee TJ, Cho DI - Sensors (Basel) (2015)

Bottom Line: We propose an approach to mitigate this error by using an afocal (infinite effective focal length) system.Finally, the proposed afocal OFS module was installed on a mobile robot and tested 10 times on a carpet for distances of 1 m.The average distance estimation error and standard deviation are 0.02% and 17.6%, respectively, whereas those for a conventional OFS module are 4.09% and 25.7%, respectively.

View Article: PubMed Central - PubMed

Affiliation: Department of Electrical and Computer Engineering, Automation and Systems Research Institute (ASRI), Seoul National University, Seoul 151-742, Korea. ydh01@snu.ac.kr.

ABSTRACT
This paper introduces a novel afocal optical flow sensor (OFS) system for odometry estimation in indoor robotic navigation. The OFS used in computer optical mouse has been adopted for mobile robots because it is not affected by wheel slippage. Vertical height variance is thought to be a dominant factor in systematic error when estimating moving distances in mobile robots driving on uneven surfaces. We propose an approach to mitigate this error by using an afocal (infinite effective focal length) system. We conducted experiments in a linear guide on carpet and three other materials with varying sensor heights from 30 to 50 mm and a moving distance of 80 cm. The same experiments were repeated 10 times. For the proposed afocal OFS module, a 1 mm change in sensor height induces a 0.1% systematic error; for comparison, the error for a conventional fixed-focal-length OFS module is 14.7%. Finally, the proposed afocal OFS module was installed on a mobile robot and tested 10 times on a carpet for distances of 1 m. The average distance estimation error and standard deviation are 0.02% and 17.6%, respectively, whereas those for a conventional OFS module are 4.09% and 25.7%, respectively.

No MeSH data available.


Cross-sectional view of the a focal OFS module with a pinhole diameter of 0.5 mm and a lens with a focal length of 10 mm, which images the floor onto the light-sensitive area of the sensor.
© Copyright Policy
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC4481980&req=5

sensors-15-11208-f003: Cross-sectional view of the a focal OFS module with a pinhole diameter of 0.5 mm and a lens with a focal length of 10 mm, which images the floor onto the light-sensitive area of the sensor.

Mentions: The newly designed afocal OFS module consists of a pinhole with a diameter of 0.5 mm, a lens with a focal length of 10 mm (L1 in Figure 1), and an ADNS-3080 OFS that replaces the second lens in the afocal system (see Figure 3). As the pinhole sizes gets bigger, more less-columnated light rays enter through the pinhole, which makes the image less clear, which in turn increases the sensitivity to height variations. Note, that if the pinhole size is too small, there is insufficient light for the afocal OFS to recognize the surface pattern. We have selected a pinhole diameter of 0.5 mm with 4 LEDs in this study. The smaller pinhole size gives clear images and blocks more nonparallel light, whereas the sensor needs more light in order to obtain brighter images [33].


Afocal optical flow sensor for reducing vertical height sensitivity in indoor robot localization and navigation.

Yi DH, Lee TJ, Cho DI - Sensors (Basel) (2015)

Cross-sectional view of the a focal OFS module with a pinhole diameter of 0.5 mm and a lens with a focal length of 10 mm, which images the floor onto the light-sensitive area of the sensor.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4481980&req=5

sensors-15-11208-f003: Cross-sectional view of the a focal OFS module with a pinhole diameter of 0.5 mm and a lens with a focal length of 10 mm, which images the floor onto the light-sensitive area of the sensor.
Mentions: The newly designed afocal OFS module consists of a pinhole with a diameter of 0.5 mm, a lens with a focal length of 10 mm (L1 in Figure 1), and an ADNS-3080 OFS that replaces the second lens in the afocal system (see Figure 3). As the pinhole sizes gets bigger, more less-columnated light rays enter through the pinhole, which makes the image less clear, which in turn increases the sensitivity to height variations. Note, that if the pinhole size is too small, there is insufficient light for the afocal OFS to recognize the surface pattern. We have selected a pinhole diameter of 0.5 mm with 4 LEDs in this study. The smaller pinhole size gives clear images and blocks more nonparallel light, whereas the sensor needs more light in order to obtain brighter images [33].

Bottom Line: We propose an approach to mitigate this error by using an afocal (infinite effective focal length) system.Finally, the proposed afocal OFS module was installed on a mobile robot and tested 10 times on a carpet for distances of 1 m.The average distance estimation error and standard deviation are 0.02% and 17.6%, respectively, whereas those for a conventional OFS module are 4.09% and 25.7%, respectively.

View Article: PubMed Central - PubMed

Affiliation: Department of Electrical and Computer Engineering, Automation and Systems Research Institute (ASRI), Seoul National University, Seoul 151-742, Korea. ydh01@snu.ac.kr.

ABSTRACT
This paper introduces a novel afocal optical flow sensor (OFS) system for odometry estimation in indoor robotic navigation. The OFS used in computer optical mouse has been adopted for mobile robots because it is not affected by wheel slippage. Vertical height variance is thought to be a dominant factor in systematic error when estimating moving distances in mobile robots driving on uneven surfaces. We propose an approach to mitigate this error by using an afocal (infinite effective focal length) system. We conducted experiments in a linear guide on carpet and three other materials with varying sensor heights from 30 to 50 mm and a moving distance of 80 cm. The same experiments were repeated 10 times. For the proposed afocal OFS module, a 1 mm change in sensor height induces a 0.1% systematic error; for comparison, the error for a conventional fixed-focal-length OFS module is 14.7%. Finally, the proposed afocal OFS module was installed on a mobile robot and tested 10 times on a carpet for distances of 1 m. The average distance estimation error and standard deviation are 0.02% and 17.6%, respectively, whereas those for a conventional OFS module are 4.09% and 25.7%, respectively.

No MeSH data available.