39 research outputs found
Artificial Neural Network-based error compensation procedure for low-cost encoders
An Artificial Neural Network-based error compensation method is proposed for
improving the accuracy of resolver-based 16-bit encoders by compensating for
their respective systematic error profiles. The error compensation procedure,
for a particular encoder, involves obtaining its error profile by calibrating
it on a precision rotary table, training the neural network by using a part of
this data and then determining the corrected encoder angle by subtracting the
ANN-predicted error from the measured value of the encoder angle. Since it is
not guaranteed that all the resolvers will have exactly similar error profiles
because of the inherent differences in their construction on a micro scale, the
ANN has been trained on one error profile at a time and the corresponding
weight file is then used only for compensating the systematic error of this
particular encoder. The systematic nature of the error profile for each of the
encoders has also been validated by repeated calibration of the encoders over a
period of time and it was found that the error profiles of a particular encoder
recorded at different epochs show near reproducible behavior. The ANN-based
error compensation procedure has been implemented for 4 encoders by training
the ANN with their respective error profiles and the results indicate that the
accuracy of encoders can be improved by nearly an order of magnitude from
quoted values of ~6 arc-min to ~0.65 arc-min when their corresponding
ANN-generated weight files are used for determining the corrected encoder
angle.Comment: 16 pages, 4 figures. Accepted for Publication in Measurement Science
and Technology (MST
Where would we be without counterfactuals?
Huw Price gives his inaugural lecture as Bertrand Russell Professor of Philosophy. Bertrand Russellâs celebrated essay âOn the Notion of Causeâ was first delivered to the Aristotelian Society on 4 November 1912, as Russellâs Presidential Address. The piece is best known for a passage in which its author deftly positions himself between the traditional metaphysics of causation and the British crown, firing broadsides in both directions: âThe law of causalityâ, Russell declares, âLike much that passes muster in philosophy, is a relic of a bygone age, surviving, like the monarchy, only because it is erroneously supposed to do no harm.â To mark the lectureâs centenary, we offer a contemporary view of the issues Russell here puts on the table, and of the health or otherwise, at the end of the essayâs first century, of his notorious conclusion
From Mendelâs discovery on pea to todayâs plant genetics and breeding
In 2015, we celebrated the 150th anniversary of the presentation of the seminal work of Gregor Johann Mendel. While Darwinâs theory of evolution was based on differential survival and differential reproductive success, Mendelâs theory of heredity relies on equality and stability throughout all stages of the life cycle. Darwinâs concepts were continuous variation and âsoftâ heredity; Mendel espoused discontinuous variation and âhardâ heredity. Thus, the combination of Mendelian genetics with Darwinâs theory of natural selection was the process that resulted in the modern synthesis of evolutionary biology. Although biology, genetics, and genomics have been revolutionized in recent years, modern genetics will forever rely on simple principles founded on pea breeding using seven single gene characters. Purposeful use of mutants to study gene function is one of the essential tools of modern genetics. Today, over 100 plant species genomes have been sequenced. Mapping populations and their use in segregation of molecular markers and markerâtrait association to map and isolate genes, were developed on the basis of Mendel's work. Genome-wide or genomic selection is a recent approach for the development of improved breeding lines. The analysis of complex traits has been enhanced by high-throughput phenotyping and developments in statistical and modeling methods for the analysis of phenotypic data. Introgression of novel alleles from landraces and wild relatives widens genetic diversity and improves traits; transgenic methodologies allow for the introduction of novel genes from diverse sources, and gene editing approaches offer possibilities to manipulate gene in a precise manner
In what sense does 'nothing make sense except in the light of evolution'?
Dobzhansky argued that biology only makes sense if life on earth has a shared history. But his dictum is often reinterpreted to mean that biology only makes sense in the light of adaptation. Some philosophers of science have argued in this spirit that all work in âproximalâ biosciences such as anatomy, physiology and molecular biology must be framed, at least implicitly, by the selection histories of the organisms under study. Others have denied this and have proposed non-evolutionary ways in which biologists can frame these investigations. This paper argues that an evolutionary perspective is indeed necessary, but that it must be a forward-looking perspective informed by a general understanding of the evolutionary process, not a backward-looking perspective informed by the specific evolutionary history of the species being studied. Interestingly, it turns out that there are aspects of proximal biology that even a creationist cannot study except in the light of a theory of their effect on future evolutio
Epigenesis/Preformation(ism)
At the end of the nineteenth century, epigenesis and preformationism were presented in An Illustrated Dictionary of Medicine, Biology and allied Sciences as: âepigenesis is in biology, the theory that holds the embryo to be the result of the union of the male and female elements, and the fully formed organism the result of a gradual process of differentiation, in distinction to the theory of encasement, preformation, or evolution, which held the embryo to pre-exist in a minute form within the germâ