Appendix; Adjusting Pid Controller - TECO speecon 7200ma Instruction Manual

APPENDIX

A. Adjusting PID controller
Use the following procedure to activate PID control and then adjust it while
monitoring the response.
1. Enable PID control.
2. Increase the proportional gain Bn-17 as far as possible without creating oscillation.
3. Decrease the integral time Bn-18 as far as possible without creating oscillation.
4. Increase the derivative time Bn-19 as far as possible without creating oscillation.
The Proportional, Integral and Derivative control function provides closed-loop
control, or regulation, of a system process variable (pressure, temperature, etc.). This
regulation is accomplished by comparing a feedback signal with a reference signal,
which results in an error signal. The PID control algorithm then performs calculations,
based upon the PID parameter settings (Bn-16 through Bn-20 on page 38), on this error
signal. The result of the PID algorithm is then used as the new frequency reference, or is
added to the existing speed reference.
The PID target value can come from the frequency command (from operator) or a
Multi-Function Analog Input.
Select the PID control feedback signal from external terminal AIN for a current
signal (4-20mA DC) or from VIN for a voltage (0-10 VDC).
The Proportional gain is the value by which the error signal is multiplied to generate
a new PID controller output. A higher setting will result in a system with quicker
response. A lower setting will result in a more stable yet slower system.
The Integral Time is a parameter that determines how fast the PID controller will
seek to eliminate any steady-state error. The smaller the setting, the faster the error will
be eliminated. To eliminate the integral function entirely, set this parameter to 0.0
seconds. A lower setting will result in a more responsive system. A higher setting will
result in a more stable yet slower system.
The Integral Upper Limit is a parameter that will limit the effect that the integrator
can have. It works if the PID controller output is positive or negative. It can also be used
to prevent integrator "wind-up."
The Derivative Time is a parameter that can be adjusted to increase system response
to fast load or reference changes, and to reduce overshoot upon startup. To eliminate the
differential function entirely, set this parameter to 0.00 seconds.
The PID Output Limit (Cn-51, Cn-52) is parameter that can be used to set the
maximum effect the PID controller will have on the system. It also will limit the PID
output when it is either positive or negative.
NOTE : When the PID output limit is reached, the integrator will hold and not change in
value until the PID output is less than the PID output limit.
The PID bias (Bn-20) is a parameter that will add a fixed percentage to the PID
output. It can be used to tune out small system offsets.
NOTE : This parameter is set as a percentage of maximum output frequency.
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