Setting
up Compax3
C3I20T11 / C3I32T11
188
192-120103 N13 C3I20T11 / C3I32T11 December 2010
4.4.3.3
Automatic controller design
In this chapter you can read about:
Dynamics of a control .................................................................................................... 188
Cascade control ............................................................................................................ 195
Rigidity .......................................................................................................................... 196
Automated controller design .......................................................................................... 198
Controller coefficients .................................................................................................... 200
Dynamics of a control
In this chapter you can read about:
Structure of a control ..................................................................................................... 188
Oscillating plant ............................................................................................................. 188
Stability, attenuation ...................................................................................................... 188
Velocity, bandwidth ........................................................................................................ 189
Setpoint and disturbance behavior of a control loop ....................................................... 193
Response ...................................................................................................................... 194
Limitation behavior ........................................................................................................ 195
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: ............................................................... 189
Stability problem in the low-frequency range: ................................................................. 189
In general, two stability problems may occur in a servo drive control:
