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Setpoint channel and closed-loop control
7.4 Vector speed/torque control with/without an encoder
If vibrations occur with these settings, the speed controller gain (Kp) will need to be reduced
manually. Actual-speed-value smoothing can also be increased (standard procedure for
gearless or high-frequency torsion vibrations) and the controller calculation performed again
because this value is also used to calculate Kp and Tn.
The following relationships apply for optimization:
● If Kp is increased, the controller becomes faster, although overshoot is increased.
However, signal ripples and vibrations in the speed control loop will increase.
● Although reducing Tn will also speed up the controller, it will increase overshoot.
When setting speed control manually, you are advised to define the dynamic response via
Kp (and actual-speed-value smoothing) first, so that the integral time can subsequently be
reduced as much as possible. Please remember that closed-loop control must also remain
stable in the field-weakening range.
To suppress any vibrations that occur in the speed controller, it is usually only necessary to
increase the smoothing time in p1452 for operation without an encoder or p1442 for
operation with an encoder, or reduce the controller gain.
The integral output of the speed controller can be monitored via r1482 and the limited
controller output via r1508 (torque setpoint).
Note
Reduced dynamic response for encoderless operation
In comparison with speed control with an encoder, the dynamic response of drives without
an encoder is significantly reduced. The actual speed is derived by means of a model
calculation based on the converter output variables for current and voltage that have a
corresponding interference level. To this end, the actual speed must be adjusted by means
of filter algorithms in the software.
Speed controller response when a brake is opened
After a motor has been a magnetized, "Open brake" is controlled. The value that the BICO
input delivers defines the speed controller response:
● BICO input p1475 (torque setting value for the motor holding brake) supplies a value of 0:
– The speed controller I component is immediately enabled; this means that the system
– Depending on the parameter assignment, the speed setpoint remains inhibited until
● BICO input p1475 (torque setting value for the motor holding brake) supplies a value ≠ 0:
– The speed controller I component is held at the specified setting value until the "Brake
– Only then are the speed controller I component and the speed setpoint enabled.
468
can respond to a slipping load and establish a holding torque.
the brake opening time has elapsed (p1275.6 = 0) - or until the brake feedback signal
is received (p1275.6 = 1).
open" feedback signal is received.
Operating Instructions, 12/2018, A5E36652151A
Enclosed Drives
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