Abstract. Planetary reducers have a wide and significant
application in modern machine industry. They are extremely compact and reliable,
and they can achieve a wide range of gear ratios as well as high efficiency.
Since they often operate in extremely changeable working conditions, such as
often starting and stoping, it is both interesting and desirable to study
their dynamic behaviour. This paper presents a dynamic model of a planetary
reducer with double planet gears created by applying Lagrange's equations of the second
kind. After a planetary gear reducer has been designed and a CAD model
created, the dynamic model was made. Most of characteristic values needed
for solution of the equations are taken from the CAD model. Due to their
complexity, the equations are solved in math simulation software. A lot
of interesting results concerning the dynamic behaviour of the model are
obtained, which can be helpful in understanding the dynamic occurrences
in the inside of a planetary gearbox. At the end of the paper, conclusions are
drawn, and further research directions in this area are given.