System and method for automatically tuning a process controller

A method of tuning a control system including a process controlled by a process controller having tunable control parameters, said process having a process output which is sensed by said process controller and having a control input connected to said process controller, comprising:

• disconnecting said process controller from said control input;
• applying a signal having a first portion and a second portion to said control input of said process to cause said process to undergo controlled self-oscillation;
• monitoring said process output during said controlled self-oscillation;
• determining at least one process characteristic from said process output during application of said first portion of said signal;
• determining at least one additional process characteristic from said process output during application of said second portion of said signal;
• and
• tuning said control system by calculating values for said tunable control parameters as functions of said process characteristics.

A tunable control system comprising:

• a process controller having a process variable input and a controlled variable output, said input and output being adapted for connection to a process to be controlled;
• a signal generator producing a controllable generator signal adapted for connection to said process to be controlled;
• and
• a tuner, connected to said process controller and signal generator, and adapted for connection to said process to be controlled, said tuner including:
• means for disconnecting said controlled variable output from said process and for connecting said controllable generator signal to said process;
• means for controlling said signal generator to apply a signal to said process to cause said process to undergo controlled self-oscillation;
• means for monitoring said process variable during said controlled self-oscillation;
• means for determining, from a first portion of said controlled self-oscillation, a time delay of said process, and for determining from a second portion of said controlled self-oscillation, an ultimate gain and an ultimate period of said process;
• and
• means for calculating control parameters for said process controller, based upon on said time delay, ultimate period and ultimate gain of said process.