792 
accuracy. Also, time is in the first assumption infinitely 
determinable. In this case,  the relative position of the 
crank  is  determined  by  a  fully  deterministic 
relationship:  the  speed  multiplied  by  time  gives  the 
angle  of  rotation  of  the  shaft.  In  order  to  know  the 
position of a given throw at any time, we still need to 
know the initial conditions: the angle  (Fig. 9) at the 
t=0 moment. Let us assume, that the initial position of 
the  crankshaft  was  determined  extremely  precisely: 
0=36.001°. Such a record means that the initial angle of 
rotation  of  the  throw  has  been  determined  to  an 
accuracy of ±0.001°. The actual angular position may be 
=36.00149...°  or  =36.00050...°.  The  initial  angular 
position  of  the  shaft  can  be  written  in  a  form: 
0=36.001nnnnn...°. Where "n" stands for an unknown 
number. After ten ignitions (in each cylinder) the throw 
will  rotate  by  10x36°,  it  is  enough  to  multiply  the 
number 0 by ten. In the decimal system it is reduced 
to  moving  the  point  one  position  to  the  right.  As  a 
result  of  this  operation  we  will  obtain: 
10=360.01nnnnn...°  =  0.01nnnnn...°.  The  precise 
knowledge of  the  throw  position is still  high  (±0,01°) 
but has decreased tenfold! After a thousand ignitions 
our knowledge of the crankpin position is reduced to 
±1° because: 1000=36001.nnnnn...° = 1.nnnnn...°.   
It can be observed that after 10 thousand ignitions 
the accuracy of the crank position drops to the value of 
±100°,  i.e.  in  practice  it  is  unknown  (theoretically  a 
completely  undetermined  position  occurs  after  100 
thousand ignitions). It should be stressed that having 
ideally  deterministic  dependencies  (with  infinitely 
accurate parameters of time and rotational speed) we 
are  not  able  to  determine  the  searched  value  after  a 
sufficient  number  of cycles  of  work.  If  the  rotational 
speed of the considered engine is n=100 rpm, then for a 
10-cylinder  engine  100  thousand  ignitions  will  occur 
after  10  thousand  revolutions,  i.e.  after  100  minutes. 
After  about  an  hour  and  a  half  it  is  impossible  to 
determine  the  position  of  the  crank  despite  the 
determination  of  its  initial  conditions  with  a 
remarkable accuracy of 0.001. In practice, the situation 
of  the  researcher  is  even  more  difficult,  because  the 
engine  speed  can  be  determined  only  with  a  finite 
accuracy,  and  what  is  more,  the  assumption  of  a 
constant  speed  is  also  a  certain  (often  coarse) 
approximation.  Only the  error  of  time  determination 
can be ignored in engineering practice, because of the 
possibility  of  obtaining  a  very  high  accuracy  of  its 
determination. 
In  order  to  graphically  illustrate  the  described 
phenomenon, a simple procedure of crankshaft crank 
position  calculation  was  performed.  It  was  assumed 
that  the  starting  throw  position,  equal  to  10°,  is 
determined  with  the  accuracy  of  ±0.01°.  The  next 
position  is  obtained  by  multiplying  the  previous 
angular position by 10 (due to the ease of operation in 
the decimal system) - the subsequent cycles of work are 
a  tenfold  increase  in  the  angle  describing  the  throw 
position. Of course, the results obtained above 360° are 
reduced to the range of 0-360°. As already shown in the 
previous  paragraph,  each  new  cycle  is  a  tenfold 
reduction  in  the  accuracy  of  the  throw  position 
determination. The subsequent numerical values of the 
angular positions are calculated deterministically, but 
their final values have a random scattering equal to the 
accuracy  of  the  position  determination  for  the  given 
calculation  cycle.  For  example,  in  the  second 
calculation  cycle  we  have  the  angular  position  100° 
with the dispersion of ±0.1°; so for further calculations 
the  number  99.9°  or  e.g.  the  number  100.05°  can  be 
used. Fig. 10 shows an exemplary (due to randomness, 
each  subsequent  calculation  will  give  a  different 
course) course of changes in the position  of throw of 
the crankshaft. In order to make the drawing easier to 
read,  the  crank  position  (navy  blue  line)  is given  for 
every  tenth  calculation  cycle,  while  the  size  of  the 
position error (red line) is given for every hundredth 
calculation  cycle.  It  can  be  observed  that  after  2,000 
cycles the error rate covers the entire 0-360° range. This 
means that the throw position is undetermined. 
 
Figure 10.  Position  of  the  crank  and  its  dispersion  in 
subsequent calculation cycles 
The sensitivity of the system to initial conditions is 
shown in Fig. 11. The position of the throw of a shaft of 
the  crankshaft  for  three  starting  values  has  been 
calculated. The initial throw position was determined 
as  10.00°  (continuous  blue  line),  9.99°  (dotted  green 
line) and 10.01° (dotted brown line). It should be noted 
that all lines start from practically the same point, while 
the  course  of  throw  position  changes  is  random  and 
drastically  different  for  each  initial  condition.  For 
example, for cycle no. 1801 the throw can be deflected 
from the vertical by 56° or 286° (for 0=9,99°)) or 114° 
(for 0=10,01°). 
 
Figure 11.  Sensitivity  to  the  determination  of  the  crank 
position to initial conditions 
The determination of the throw of a shaft position 
with  any  finite  accuracy  will  not  permit  the 
determination of its angular position after a sufficiently 
long time. It should be noted that the above examples 
have been prepared for the simplest way of modeling - 
linear  models.  In  case  of  the  occurrence  of  non-
linearities  (e.g.  geometrical,  material),  describing 
physical phenomena becomes very complicated. In the 
descriptions there are bifurcations (jumping change of 
properties  of  a  mathematical  model  with  a  small 
change of its parameters), which lead to the formation 
of  completely  different  families  of  solutions  passing 
through  bifurcation  points.  The  whole  of  these 
phenomena is defined by the term deterministic chaos 
[7].  Generally,  hypersensitivity  to  initial  conditions