Parker EME
Setting up Compax3
192-120101 N11 C3I11T11 November 2007
137
4.4.3.3
Automatic controller design
In this chapter you can read about:
Dynamics of a control ......................................................................................................................137
Cascade control ...............................................................................................................................144
Stiffness ...........................................................................................................................................145
Automated controller design ............................................................................................................147
Controller coefficients ......................................................................................................................148
Dynamics of a control
In this chapter you can read about:
Structure of a control .......................................................................................................................137
Oscillating plant ...............................................................................................................................137
stability, attenuation .........................................................................................................................138
Velocity, bandwidth ..........................................................................................................................139
Setpoint and disturbance behavior of a control loop........................................................................141
response ..........................................................................................................................................143
Limitation behavior...........................................................................................................................144
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 distorsion.
