Setting
up Compax3
C3I20T11 / C3I32T11
198
192-120103 N13 C3I20T11 / C3I32T11 December 2010
Correlation between the terms introduced
The introduced terms:
Stability
Damping
Velocity
Bandwidth
Setpoint and disturbance behavior
Control variable limitation
Replacement time constant
Rigidity
are related as follows:
A well-attenuated control features a stable control behavior.
The velocity of a control loop is a measure for the reaction rate of the controller to
the disturbance variable (disturbance behavior) as well as to the setpoint variable
(setpoint behavior).
The faster the control, the higher its bandwidth.
The term replacement time constant is an approximation and is only valid in a
defined scope1. In this scope, the control is always stable and well-attenuated.
If the controller does not work in the linear range, but the control variable of the
controller is within the limitation, the control slows down and the control difference
rises.
The stiffness represents the bandwidth of the velocity control. The higher the
stiffness value of the velocity control, the higher the bandwidth of the velocity
controller and the stiffer the drive.
Automated controller design
In this chapter you can read about:
Step response of the velocity loop depending on the optimization parameter "attenuation" and "stiffness"
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D-term ........................................................................................................................... 199
Position loop .................................................................................................................. 199
The controller design takes place after the configuration immediately before the
configuration download into the device. The controller coefficients are preassigned
according to the design method of cross-ratios so that a stable control is achieved.
The automatic, robust controller design calculates the P and I terms of the
individual controllers (current, velocity, position) on the basis of the configured
motor and application parameters.
Faulty motor and application parameters may lead under certain circumstances to
instable controllers.
The controller parameters are not directly available for the optimization. Instead,
they can be changed with the aid of the following optimization parameters:
Optimization of the current controller
dynamics:
Current loop bandwidth in %
"Attenuation of current loop" in %
Optimization of the velocity loop
dynamics:
"Stiffness" in %
"Attenuation" in %
Velocity loop - "D" term in %
The bandwidth parameter states the actually effective % of the calculated default
velocity. The default bandwidth of the current controller is fixed to approx.
fGR=531Hz. In reverse this signifies that each motor delivers the same step
response. The prerequisite is, of course, that you keep out of the control signal
limitation (voltage limitation). The attenuation characterizes the controller's
tendency to oscillate with respect to an excitation signal (see below). The stiffness
(of the velocity loop, corresponds to the bandwidth of the current loop) describes
the velocity of the velocity loop (see below).
Please observe:
