Parker EME
Setting up Compax3
192-120113 N08 C3I12T11 - December 2010
193
4.4.3.3
Automatic controller design
In this chapter you can read about:
Dynamics of a control .................................................................................................... 193
Cascade control ............................................................................................................ 200
Rigidity .......................................................................................................................... 200
Automated controller design .......................................................................................... 202
Controller coefficients .................................................................................................... 204
Dynamics of a control
In this chapter you can read about:
Structure of a control ..................................................................................................... 193
Oscillating plant ............................................................................................................. 193
Stability, attenuation ...................................................................................................... 193
Velocity, bandwidth ........................................................................................................ 194
Setpoint and disturbance behavior of a control loop ....................................................... 197
Response ...................................................................................................................... 199
Limitation behavior ........................................................................................................ 199
A change in the input value of a dynamic transmission element causes a change of
its output value. The change of the output value is however not immediately
effective, but takes a certain time, the transient response. The course of the
transient response is characteristic for certain kinds of transmission behavior.
For this reason, a complete description of the transmission properties of a control
comprises the stationary behavior (all setpoint, actual and disturbance values in
settled state), as well as the dynamic behavior.
Structure of a control
Regler
Controller
Regelstrecke
Control Process
Z
X
-
W
-
X
Regler / Control
Parameter
The basic task of a control is the generation and maintaining of a desired state or
sequence in spite of interfering disturbances. It is essential that the effects of the
disturbances are balanced with the correct force and at the correct time. In the
above figure, the setpoint value W represents the desired state and the disturbance
value Z represents the interfering disturbance. The actual value X represents the
generated and maintained state.
Oscillating plant
Oscillating control paths are control paths that respond with attenuated or
unattenuated oscillation to an abrupt change in the setpoint value. Part of this class
are for instance:
Linear actuators with toothed belts, as a toothed belt represents an elasticity.
A mechanic shaft with an external mass moment of inertia, as the shaft
represents an elasticity due to its torsional properties.
In general this kind of elasticity is due to a high ratio between J
Load
/J
Motor
, as the
shaft is normally not designed for this high external load and which may lead to a
considerable distortion.
Stability, attenuation
In this chapter you can read about:
Stability problem in the high-frequency range: ............................................................... 194
Stability problem in the low-frequency range: ................................................................. 194
In general, two stability problems may occur in a servo drive control:
