User guide

CME 2 User Guide Control Loops
Copley Controls 131
11.7: Notes on the Position Mode and Position Loop
11.7.1: Position Loop Diagram
The amplifier receives position commands from the digital or analog command inputs,
over the CAN interface or serial bus, or from the CVM Control Program. When using
digital or analog inputs, the amplifier's internal trajectory generator calculates a
trapezoidal motion profile based on trajectory limit parameters. When using the CAN bus,
serial bus, or CVM Control Program, a trapezoidal or S-curve profile can be programmed.
The trajectory generator updates the calculated profile in real time as position commands
are received.
The output of the generator is an instantaneous position command (limited position). In
addition, values for the instantaneous profile velocity and acceleration are generated.
These signals, along with the actual position feedback, are processed by the position loop
to generate a velocity command.
To bypass the trajectory generator while in digital or analog position modes, set the
maximum acceleration to zero. The only limits in effect will now be the velocity loop
velocity limit and the current limits. (Note that leaving the maximum acceleration set to
zero will prevent other position modes from operating correctly.)
The following diagram summarizes the position loop.
Target
Position
Velocity
Command
Trajectory
Generator
Position Loop
Feedback
Limits:
Max velocity
Max accel
Max decel
Abort decel
Position Proportional Gain (Pp)
Velocity Feed Forw ard (Vff)
Acceleration Feed Forw ard (Aff)
Profile Acceleration
Profile Velocity
Limited Position
+
+
-
+
+
Gain
Multiplier
from motor encoder or resolver
from optional position encoder (on load)
11.7.2: Trajectory Limits
In position mode, the trajectory generator applies these limits to generate the profile.
Limiter
Description
Maximum Velocity
Limits the maximum speed of the profile.
Maximum Acceleration
Limits the maximum acceleration rate of the profile.
Maximum Deceleration
Limits the maximum deceleration rate of the profile.
Abort Deceleration
Specifies the deceleration rate used by the trajectory generator when motion is
aborted.
11.7.3: Position Loop Inputs From the Trajectory Generator
The position loop receives the following inputs from the trajectory generator.
Input
Description
Profile Velocity
The instantaneous velocity value of the profile. Used to calculate the velocity
feed forward value.
Profile Acceleration
The instantaneous acceleration/deceleration value of the profile. Used to
calculate the acceleration feed forward value.
Limited Position
The instantaneous commanded position of the profile. Used with the actual
position feedback to generate a position error.