CANopen Programmer's Manual - Maccon.de

CANopen Programmer’s Manual 4: Control Loop Configuration
The Current Loop
Overview of the Current Loop
As shown below, the current limiter accepts a current command from the velocity loop, applies
limits, and passes a limited current value to the summing junction. The summing junction takes
the commanded current, subtracts the actual current (represented by the feedback signal), and
produces an error signal. This error signal is then processed using the integral and proportional
gains to produce a command. This command is then applied to the amplifier’s power stage.
Current Command
Current Offset
Current Limiter
Limits:
Peak Current
Continuous Current
Peak Current Limit Time
Limited Current
+
-
Current Loop
Current Integral Gain (Ci)
Current Proportional Gain (Cp)
Feedback (Actual Current)
PWM
Command
Current Loop Limits
The commanded current value is first reduced based on a set of current limit parameters designed
to protect the motor. These current limits are accessed through the following objects:
Output Object Name/ID Description Page #
User Peak Current Limit / Maximum current that can be generated by the amplifier for a short 151
0x2110
duration of time. This value cannot exceed the peak current rating of
the amplifier.
User Continuous Current Limit
/ 0x2111
User Peak Current Limit Time /
0x2112
Maximum current that can be constantly generated by the amplifier. 151
Maximum amount of time that the peak current can be applied to the
motor before it must be reduced to the continuous limit.
Current Loop Input
The output of the current limiting block is the input to the current loop. It is accessed through the
object Limited Current object (index 0x221E, p. 152).
Current Loop Gains
The current loop uses these gains:
Gain Description
Cp - Current loop proportional The current error (the difference between the actual and the limited commanded
current) is multiplied by this value. The primary effect of this gain is to increase
bandwidth (or decrease the step-response time) as the gain is increased.
Ci - Current loop integral The integral of the current error is multiplied by this value. Integral gain reduces the
current error to zero over time. It controls the DC accuracy of the loop, or the
flatness of the top of a square wave signal. The error integral is the accumulated
sum of the current error value over time.
These gains are represented by Error! Reference source not found. (index 0x2380, p.153) and
its sub-index objects.
Current Loop Output
The output of the current loop is a command that sets the duty cycle of the PWM output stage of
the amplifier.
Copley Controls 135
+
+
151
Motor