FAQ: In Exercise 2.10, what do the variables phi represent?
From FBSwiki
(Contributed by Richard Murray, 1 October 2012)
The variables 
and 
are the angles of the two masses on the shaft. The velocity of these masses are given by 
. The remaining parameter values describe the physical constants for the system:
represents moments of inertia, 
is the damping
coefficient, 
represents the shaft stiffness, 
is the torque
constant for the motor, and 
is the disturbance torque applied at
the end of the shaft.
