Holistic methods for visual navigation of mobile robots in outdoor environments

Differt D. Holistic methods for visual navigation of mobile robots in outdoor environments. Bielefeld: Universität Bielefeld; 2017

Lokalisation ultrakurzer Laserpulse in randomisierten Nanostrukturen

Differt D. Lokalisation ultrakurzer Laserpulse in randomisierten Nanostrukturen. Bielefeld: Universität Bielefeld; 2016

Spectral skyline separation: Extended landmark databases and panoramic imaging

Differt D, Möller R. Spectral skyline separation: Extended landmark databases and panoramic imaging. Sensors. 2016;16(10): 1614

The problem of home choice in skyline-based homing

Müller M, Bertrand O, Differt D, Egelhaaf M. The problem of home choice in skyline-based homing. PLOS One. 2018;13(3): e0194070.Navigation in cluttered environments is an important challenge for animals and robots alike and has been the subject of many studies trying to explain and mimic animal navigational abilities. However, the question of selecting an appropriate home location has, so far, received only little attention. This is surprising, since the choice of a home location might greatly influence an animal’s navigation performance. To address the question of home choice in cluttered environments, a systematic analysis of homing trajectories was per- formed by computer simulations using a skyline-based local homing method. Our analysis reveals that homing performance strongly depends on the location of the home in the envi- ronment. Furthermore, it appears that by assessing homing success in the immediate vicin- ity of the home, an animal might be able to predict its overall success in returning to it from within a much larger area

Skyline-based localisation for aggressively manoeuvring robots using UV sensors and spherical harmonics

Place recognition is a key capability for navigating robots. While significant advances have been achieved on large, stable platforms such as robot cars, achieving robust performance on rapidly manoeuvring platforms in outdoor natural conditions remains a challenge, with few systems able to deal with both variable conditions and large tilt variations caused by rough terrain. Taking inspiration from biology, we propose a novel combination of sensory modality and image processing to obtain a significant improvement in the robustness of sequence-based image matching for place recognition. We use a UV-sensitive fisheye lens camera to segment sky from ground, providing illumination invariance, and encode the resulting binary images using spherical harmonics to enable rotation-invariant image matching. In combination, these methods also produce substantial pitch and roll invariance, as the spherical harmonics for the sky shape are minimally affected, providing the sky remains visible. We evaluate the performance of our method against a leading appearance-invariant technique (SeqSLAM) and a leading viewpoint-invariant technique (FAB-MAP 2.0) on three new outdoor datasets encompassing variable robot heading, tilt, and lighting conditions in both forested and urban environments. The system demonstrates improved condition- and tilt-invariance, enabling robust place recognition during aggressive zigzag manoeuvring along bumpy trails and at tilt angles of up to 60 degrees

Crucial role of ultraviolet light for desert ants in determining direction from the terrestrial panorama

Ants use the panoramic skyline in part to determine a direction of travel. A theoretically elegant way to define where terrestrial objects meet the sky is to use an opponent-process channel contrasting green wavelengths of light with ultraviolet (UV) wavelengths. Compared with the sky, terrestrial objects reflect relatively more green wavelengths. Using such an opponent-process channel gains constancy in the face of changes in overall illumination level. We tested the use of UV wavelengths in desert ants by using a plastic that filtered out most of the energy below 400 nm. Ants, Melophorus bagoti, were trained to home with an artificial skyline provided by an arena (experiment 1) or with the natural panorama (experiment 2). On a test, a homing ant was captured just before she entered her nest, and then brought back to a replicate arena (experiment 1) or the starting point (the feeder, experiment 2) and released. Blocking UV light led to deteriorations in orientation in both experiments. When the artificial skyline was changed from opaque to transparent UV-blocking plastic (experiment 3) on the other hand, the ants were still oriented. We conclude that UV wavelengths play a crucial role in determining direction based on the terrestrial surround.10 page(s

Snapshot navigation in the wavelet domain

Many animals rely on robust visual navigation which can be explained by snapshot models, where an agent is assumed to store egocentric panoramic images and subsequently use them to recover a heading by comparing current views to the stored snapshots. Long-range route navigation can also be explained by such models, by storing multiple snapshots along a training route and comparing the current image to these. For such models, memory capacity and comparison time increase dramatically with route length, rendering them unfeasible for small-brained insects and low-power robots where computation and storage are limited. One way to reduce the requirements is to use a compressed image representation. Inspired by the filter bank-like arrangement of the visual system, we here investigate how a frequency-based image representation influences the performance of a typical snapshot model. By decomposing views into wavelet coefficients at different levels and orientations, we achieve a compressed visual representation that remains robust when used for navigation. Our results indicate that route following based on wavelet coefficients is not only possible but gives increased performance over a range of other models

Asiakastyytyväisyystutkimus : case: Jalkine Differt Ky

Tämä opinnäytetyö käsittelee Nurmijärvellä sijaitsevan kenkäkaupan, Jalkine Differtin, asiakastyytyväisyyttä tehdyn tutkimuksen pohjalta. Tutkimus haluttiin tehdä, sillä aikaisempaa vertailupohjaa ei ole ja liikkeen yrittäjä sekä nimi ovat vaihtuneet kolme vuotta sitten. Nurmijärven kirkonkylässä on ollut kenkäkauppa viidenkymmen vuoden ajan, joten se on monelle tuttu. Asiakaskunta on viime vuosina muuttunut, joten nykytilannetta haluttiin kartoittaa esimerkiksi tiedustelemalla tyytyväisyyttä valikoimaan. Kyselyn tärkeimmät selvitettävät asiat olivat asiakastyytyväisyys henkilökuntaan, valikoimaan ja liikkeeseen. Lisäksi haluttiin selvittää liikkeen näkyvyyttä eri kanavissa ja mitä kautta asiakkaat haluavat saada tietoa. Tämä sen takia, koska liikkeen markkinointikanavat ovat muuttuneet edellisen kauppiaan ajalta. Avoimien kysymyksien kautta selvitettiin muun muassa, mitä vastaajat mahdollisesti kehittäisivät liikkeen toiminnassa tai millaisia tuotteita he haluavat valikoimaan. Käytännön osuuden taustalla ennen kyselyn tekemistä ja tiedon keräämistä oli teoreettista pohjaa. Se käsitteli monipuolisesti vähittäiskauppaa, myyntityötä sekä asiakaspalvelua, kaupan markkinointiviestintää sekä tutkimusmenetelmiä painottuen kvantitatiiviseen tutkimuk-seen ja kyselylomakkeen suunnitteluun, toteutukseen ja vastausten analysointiin. Tutkimus tehtiin kvantitatiivista tutkimusmetodia käyttäen, sillä se soveltui parhaiten tähän tarkoitukseen ja vastaukset haluttiin kerätä nimenomaan paikan päällä liikkeessä, jotta vastausprosentti olisi mahdollisimman suuri. Kyselyä tehtiin liikkeessä noin kahden viikon ajan ja vastauksia saatiin 67 kappaletta, joka ylitti viidenkymmenen vastauksen tavoitteen. Tuloksina saatiin hyödyllistä tietoa liittyen esimerkiksi siihen, mitä markkinointikanavia liikkeen kannattaisi suosia asiakkailleen ja miten tyytyväisiä asiakkaat ovat muun muassa henkilökuntaan ja liikkeen valikoimaan. Tutkimuksen avulla saatiin selville, että henkilökunnan palveluasenne ja ammattitaito sai eniten kiitosta ja yrityksen mainontaan ja markkinointiin kannattaa panostaa enemmän hyödyntäen lehti-ilmoituksia, Facebookia ja näyteikkunan esillepanoa. Kysely oli onnistunut, sillä sen avulla saatiin vastauksia haluttuihin kysymyksiin ja hyvä pohja tulevaisuuden asiakastyytyväisyyskyselyille. Lomakkeessa oli muutama pieniä epäkohtia, mutta ne eivät vaikuttaneet tuloksiin merkittävästi. Vastaajista ylivoimainen enemmistö koostui naisista, mutta naisia on enemmistö koko liikkeen asiakaskunnasta. Tutkimustulokset antoivat tärkeää tietoa esimerkiksi liikkeen markkinointiviestinnän kehittämiseen ja valikoiman parantamiseen.Customer satisfaction research : case: Jalkine Differt Ky This thesis is about customer satisfaction in a shoe shop in Nurmijärvi, called Jalkine Differt Ky, and it’s based on customer satisfaction research. Research was needed to be implemented because there is no previous research about customer satisfaction and both the entrepreneur and the name of the shop have changed three years ago. There has been a shoe shop in Nurmijärvi for 50 years so it’s well known among the citizens. The clientele has changed, so it was a good time to survey the status of the shop by asking for example about satisfaction relating to product assortment. The most important things to find out were customer satisfaction in connection with the personnel, product assortment and aspects of the shop itself. Visibility of the shop through different channels and where customers want the information were important things. This was because marketing channels of the shop have changed since the previous entrepreneur was in charge of the business. The open questions used helped to find out what customers would change in the operation and what kind of products they would like to add to the assortment. Before executing the survey and collecting data there was theoretical base which was written supporting the practical part. It consisted of retailing, selling and customer service, marketing communications relating to the shop and research methods which were mostly emphasized as quantitative research and planning the form, execution and analyzing answers. Research was done by using a quantitative method because it was the best option for this purpose and the answers were to be collected in the shop so the response rate would be as high as possible. Customer satisfaction research was executed during two weeks and there were 67 answers which was higher than the original goal (50 answers). The results of the research gave useful knowledge about which marketing channels the shop should use and how satisfied the customers were in relation to the personnel and product assortment. With the help of the research it was found that the service approach and professional ability of the personnel received the most attention and comments. Advertising and marketing the shop were things that the shop should invest more in using ads such as Facebook and increasing decoration of the shop window. The research was successful because it gave answers to what the questions wanted and it is a good base for other customer satisfaction research in the future. There were some faults in the form which was used but they didn’t have a huge effect on results. The majority of the respondents were women but women are also the majority of the clientele. The results of the research gave important information about developing marketing communication and improving the available assortment of products at the shop