Magtrol DSP6000 User Manual - 2 - About The Pid L
8
2 - About the PID L
2 - About the PID L
2 - About the PID L
2 - About the PID L
2 - About the PID Loop
oop
oop
oop
oop
The DSP6000 has PID adjustment capability for both
the speed and torque modes to provide you with the
best system response. The PID Loop comprises the
following three variables:
P
=
Proportional Gain
I
=
Integral
D =
Derivative
The setpoint is the desired load or speed. Error is the
difference between the setpoint and the actual
measurement.
P (PROPORTIONAL GAIN)
With proportional gain, the controller output is
proportional to the error or to a change in measurement.
Deviation from the setpoint is usually present.
Increasing proportional gain will make the PID loop
unstable. Increasing integral value eliminates this
instability. For best loop control, set the proportional
gain as high as possible without causing the loop to
become unstable.
I (INTEGRAL)
With integral, the controller output is proportional to
the amount of time the error is present. Increasing the
integral value eliminates the offset from the setpoint. If
the response becomes oscillatory, increase the derivative
value.
D (DERIVATIVE)
With derivative, the controller output is proportional to
the rate of change of the measurement or error.
Derivative can compensate for a changing measurement.
Derivative takes action to inhibit more rapid changes
of the measurement than proportional gain.
When a setpoint change occurs, the derivative causes
the controller gain to go the "wrong" way when the
measurement gets close to the setpoint. Derivative can
be used to control overshoot. If derivative is used, higher
gain and integral values are usually necessary.
Magtrol offers a comprehensive motor-test program
which would satisfy most of your needs. Call Magtrol
Sales at 1-800-828-7844 or 1-716-668-5555 to request
your custom software.
NOTE:
To set PID values, see Chapter 3
- Installation.
Figure 6.
PID Loop
SETTING THE CORRECT PID'S FOR
YOUR MOTOR
NOTE:
Each type of motor may have it's
own optimum PID setting.
NOTE:
The PID settings are scaled to the
maximum speed setting;
therefore the maximum speed
setting should be adjusted to just
higher than the free-run speed of
the motor being tested.
When testing a new motor where the optimal PID's are
unknown:
1. Begin with the Proportional Gain (P) and the
Integral (I) both set to a low value and the Derivative
(D) set to zero. This will allow the best opportunity
for finding the optimum in the lowest amount of
steps.
2. Using the DSP6000 in the speed mode: Set the
speed target at approximately 90% of the free-run
speed.