An adjustment system is disclosed for adjusting a proportional, integral,
derivative controller in a limited rotation motor system. The adjustment
system includes a first transform unit, a second transform unit, a model
identification unit, and a PID adjustment unit. The first transform unit
is for receiving a first digital signal that is representative of a motor
control signal, and is for providing a first frequency domain sequence
that is representative of a frequency domain representation of the motor
control signal. The second transform unit is for receiving a second
digital signal that is representative of a position detection signal, and
is for providing a second frequency domain sequence that is
representative of a frequency domain representation of the position
detection signal. The model identification unit is for identifying a
representation of a ratio of the first and second frequency domain
sequences. The PID adjustment unit is for identifying appropriate values
for the coefficient k.sub.p of a proportional unit of the system, for the
coefficient k.sub.i of an integral unit for the system, and for the
coefficient k.sub.d of a derivative unit for the system.