Tactile print has been used since the beginning of 1800, at first not
for visually impaired but as an invention (called Sonography) for the
artillery to read and write in darkness and for making several copies of a
document at once, though it was never used as intended because of it's
complexity with characters representing sound and not letters. Sonography
characters were also to big to be covered by a single finger tip wich made
reading slow.
Later on Sonography was presented at a school for blind students. It was
first rejected by the teachers but the students pushed on. One of the first
students to encounter the Sonography was Louis Braille. He reworked the 12-
dot Sonography to a six dot literal system. Over the years the Braille
system has been improved and is now used for science, mathematics and also
music purpose. With the possibility to connect Braille printers to personal
computers even graphics can be made, making abstract tables of figures
visualized by diagrams and charts.
This master thesis is about optimizing hammers in Braille printers. There
has been some problems with dot quality in Braille printers. The
first problem is that some dots are not embossed to the same height. The
problem is somewhat coupled to increased temperature in the printing head
depending on low efficiency. An other problem is how to measure striking
force. Dynamic laser measurement turned out to be the best method to measure
the striking force. By knowing speed and mass of movement, energy can be
calculated with ease. Optimization of the hammers striking force was made by
static measurement and modelling using Femlab and Matlab. The Femlab static
modell was verified by measurement with a force sensor at different
displacement. Modifications modelled in Femlab and verified in static force
measurement were then dynamically tested and measured with laser to make
sure that they worked in realit...
