| 1. |
- Fredriksson, Håkan, et al.
(författare)
-
snowBOTS: a mobile robot on snow covered ice
- 2007
-
Ingår i: Proceedings of the 13th IASTED International Conference on Robotics and Applications. - Anaheim, Calif. : ACTA Press. - 9780889866850 ; , s. 222-228
-
Konferensbidrag (refereegranskat)abstract
- We introduce snowBOTs as a generic name for robots working in snow. This paper is a study on using scan ning range measuring lasers towards an autonomous snow cleaning robot, working in an environment consisting al most entirely of snow and ice. The problem addressed here is using lasers for detecting the edges generated by "the snow meeting the road". First the laser data were filtered using his togram/median to discriminate against falling snowflakes and small objects. Then the road surface was extracted us ing the range weighted Hough/Radon transform. Finally the left and right edges of the road was detected by thresh olding. Tests have been made with a laser on top of a car driven in an automobile test range just south of the Arctic Circle. Moreover, in the campus area, the algorithms were tested in closed loop with the laser on board a robotized wheelchair.
|
|
| 2. |
- Rutsdottir, Gudrun, et al.
(författare)
-
Structural model of dodecameric heat-shock protein Hsp21 : Flexible N-terminal arms interact with client proteins while C-terminal tails maintain the dodecamer and chaperone activity
- 2017
-
Ingår i: Journal of Biological Chemistry. - : American Society for Biochemistry and Molecular Biology. - 0021-9258 .- 1083-351X. ; 292:19, s. 8103-8121
-
Tidskriftsartikel (refereegranskat)abstract
- Small heat-shock proteins (sHsps) prevent aggregation of thermosensitive client proteins in a first line of defense against cellular stress. The mechanisms by which they perform this function have been hard to define due to limited structural information; currently, there is only one high-resolution structure of a plant sHsp published, that of the cytosolic Hsp16.9. We took interest in Hsp21, a chloroplast-localized sHsp crucial for plant stress resistance, which has even longer N-terminal arms than Hsp16.9, with a functionally important and conserved methionine-rich motif. To provide a framework for investigating structure-function relationships of Hsp21 and understanding these sequence variations, we developed a structural model of Hsp21 based on homology modeling, cryo-EM, cross-linking mass spectrometry, NMR, and small-angle X-ray scattering. Our data suggest a dodecameric arrangement of two trimer-of-dimer discs stabilized by the C-terminal tails, possibly through tail-to-tail interactions between the discs, mediated through extended IXVXI motifs. Our model further suggests that six N-terminal arms are located on the outside of the dodecamer, accessible for interaction with client proteins, and distinct from previous undefined or inwardly facing arms. To test the importance of the IXVXI motif, we created the point mutant V181A, which, as expected, disrupts the Hsp21 dodecamer and decreases chaperone activity. Finally, our data emphasize that sHsp chaperone efficiency depends on oligomerization and that client interactions can occur both with and without oligomer dissociation. These results provide a generalizable workflow to explore sHsps, expand our understanding of sHsp structural motifs, and provide a testable Hsp21 structure model to inform future investigations.
|
|
| 3. |
|
|
| 4. |
- Rönnbäck, Sven, et al.
(författare)
-
An autonomous vehicle for a RobotDay
- 2007
-
Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- This paper describes the autonomous car that is being built for the RobotDay competition, arranged by SICK GmbH. The basic rule is to let an autonomous vehicle drive a track as fast as possible, based on any sensor technology. For this race SICK donated one S300 professional proximity sensor to each team. Our vehicle will use the circle sector expansion (CSE) method to avoid obstacles and to find its way along the track. We show initial results where the CSE method was used to guide the vehicle through a test track defined by cones and other objects.
|
|
| 5. |
|
|
| 6. |
|
|
| 7. |
- Rönnbäck, Sven, et al.
(författare)
-
On filtering of laser range data in snowfall
- 2008
-
Ingår i: 2008 4th International IEEE Conference Intelligent Systems. - Piscataway, NJ : IEEE Communications Society. - 9781424417391 ; , s. 33-39
-
Konferensbidrag (refereegranskat)abstract
- This paper is towards reducing the clutter from snowflakes for outdoor robots. There are three basic cases: 1. Normal operation of the laser with objects within range for detection. 2. Close range with objects close to the laser i.e. shorter than the pulse length. 3. Free space as background i.e. all detects are false. The findings are summarized as: The two lasers used were a pulsed wide beam laser and a modulated narrow beam laser. The narrow beam laser has much better penetration between the snowflakes. We did not use snow and rain threshold setting for the wide beam laser. Median filtering shows a substantial reduction in snowflake detects. The gamma distribution describes fairly well the distribution of detected snowflakes.
|
|
| 8. |
|
|
| 9. |
- Rönnbäck, Sven, et al.
(författare)
-
On passing a doorway with an autonomous Internet connected wheelchair using MATLAB
- 2005
-
Ingår i: 2005 IEEE/RSJ International Conference on Intelligent Robots and Systems. - Piscataway, NJ : IEEE Communications Society. - 0780389123 ; , s. 1532-1537
-
Konferensbidrag (refereegranskat)abstract
- If a wheelchair for disabled is used for semi-autonomous navigation indoors it must be able to navigate through doors. A door and doorway can be parameterized with five parameters. A divide and conquer implementation of the Hough transform is used to segment outlines from range scans. The client software remote controls the wheelchair from the MATLAB environment. The software consists of several Java threads that run concurrently. Sensor data are polled by threads and put into databases to reduce the network lag. The databases are used by a controller and a Kalman filter. Since most of the implementation is coded in Java it is possible to run it as a stand alone program on a computer that has Java installed. From 10 runs the trajectory offset was calculated to 0.9 cm with a standard deviation of 1.4 cm. The standard deviation of the heading was 2.2 degrees. This performance is essentially independent of the initial starting pose
|
|
| 10. |
- Rönnbäck, Sven, 1970-, et al.
(författare)
-
Range statistics and suppressing snowflakes detects for laser range finders in snowfall
- 2010
-
Ingår i: Intelligent systems. - Berlin Heidelberg : Springer. - 9783642134272 ; , s. 261-277
-
Bokkapitel (refereegranskat)abstract
- This paper presents statistics on registrations from laser range finders in snowfall. The sensors are standard laser range finders in robotics, the LMS200 and the URG-04LX. Three different working cases were identified for the pulsed laser range finder. 1) Normal operation with background objects present within the range of the sensor. 2) Close range objects where ranges to objects are shorter than the pulse length. 3) Free-space in the background. The findings are summarized as: • Two laser range finders have been used, one that sends out a pulsed wide beam and one with a modulated narrow laser beam. The narrow beam laser has better penetration between the snowflakes. • Median filtering shows a substantial reduction in snowflake detects. • The gamma distribution describes fairly well the range distribution of detected snowflakes. • In an intense snowfall where about 24% of the ranges detected snowflakes. • A time-polar median filter showed good results in suppressing snowflakes in range data.
|
|
