User guide

Control Loops CME 2 User Guide
122 Copley Controls
11.5: Notes on the Velocity Mode and Velocity Loop
11.5.1: Velocity Loop Diagram
As shown below, the velocity loop limiting stage accepts a velocity command, applies
limits, and passes a limited velocity command to the input filter. The filter then passes a
velocity command to the summing junction. The summing junction subtracts the actual
velocity, represented by the feedback signal, and produces an error signal. (The velocity
loop feedback signal is always from the motor feedback device even when an additional
encoder is attached to the load.) The error signal is then processed using the integral and
proportional gains to produce a current command. Programmable digital filters are
provided on both the input and output command signals.
Velocity
Command
Current
Command
Velocity Limiter
Velocity Loop
Feedback (Derived Velocity)
Limits:
Velocity
Acceleration*
Deceleration*
Emergency Stop Deceleration*
*Not used w hen velocity loop is controlled by position loop. See "Velocity Loop Limits" for details.
Velocity Integral Gain (Vi)
Velocity Proportional Gain (Vp)
Limited
Velocity
+
-
+
+
Filter
Filter
11.5.2: Inputs
In velocity mode, the velocity command comes from one of the following:
 The amplifier’s analog or PWM inputs.
 A CANopen network via the amplifier’s CAN interface.
 A Copley Virtual Motion (CVM) control program.
 The amplifier’s internal function generator.
In position mode, the velocity command is generated by the position loop.
11.5.3: Velocity Loop Limits
The velocity command is limited based on the following set of parameters designed to
protect the motor and/or the mechanical system.
Limiter
Description
Velocity Limit
Sets the maximum velocity command input to the velocity loop.
Acceleration
Limit
Limits the maximum acceleration rate of the commanded velocity input to the velocity loop.
This limit is used in velocity mode only. In position mode, the trajectory generator handles
acceleration limiting.
Deceleration
Limit
Limits the maximum deceleration rate of the commanded velocity input to the velocity loop.
This limit is used in velocity mode only. In position mode, the trajectory generator handles
deceleration limiting.
Fast Stop
Ramp
Specifies the deceleration rate used by the velocity loop when the amplifier is hardware
disabled. (Fast stop ramp is not used when amplifier is software disabled.) If the brake
output is active, the fast stop ramp is used to decelerate the motor before applying the
brake.
Note that Fast Stop Ramp is used only in velocity mode. In position mode, the trajectory
generator handles controlled stopping of the motor. There is one exception: if a non-latched
following error occurs in position mode, then the amplifier drops into velocity mode and the
Fast Stop Ramp is used.
For more information, see Following Error Fault Details (p. 91).