Method and apparatus for controlling an extended process

A control system for controlling an extended process including a process beginning end and a process finishing end, said control system comprising:

• a finishing end parallel inferential control loop associated with a sensor positioned at said process finishing end for taking a finished process measurement of said extended process, said finishing end parallel inferential control loop generating a finished process control signal in response to said finished process measurement, an expected finished process measurement signal, a reset output signal and a setpoint signal;
• a first intermediate parallel inferential control loop associated with a sensor positioned at a first intermediate location between said process beginning end and said process finishing end for taking a first intermediate measurement of said extended process, said first intermediate parallel inferential control loop generating a first intermediate loop control signal in response to said first intermediate measurement and an expected first intermediate measurement signal, and combining said first intermediate loop control signal with said finished process control signal from said finishing end parallel inferential control loop to generate a total control signal for controlling said extended process at said beginning end thereof;
• said first intermediate parallel inferential control loop comprising a first intermediate process model for the portion of said extended process preceding said first intermediate location, said total control signal being an input to said first intermediate process model for generating said first intermediate expected measurement signal for said first intermediate parallel inferential control loop;
• and
• said finishing end parallel inferential control loop comprising:
• a finishing end process model for that portion of said extended process adjacent and preceding said finishing end of said extended process, said first intermediate expected measurement signal being cascaded to said finishing end process model for generating said finishing end expected measurement signal for said finishing end parallel inferential control loop;
• and
• a reset model for that portion of said extended process adjacent and preceding said finishing end of said extended process, said reset model receiving the difference between said first intermediate measurement and an expected first intermediate measurement signal of said first intermediate parallel inferential control loop as a reset input signal for generating said reset output signal.

A control system for controlling an extended process including a process beginning end and a process finishing end, said control system comprising:

• a plurality of parallel inferential control loops positioned at spaced locations ranging from said beginning end of said extended process to said finishing end of said extended process, each of said parallel inferential control loops comprising:
• a process model corresponding to a portion of said extended process associated with said parallel inferential control loop for receiving a signal representative of control or a process model output preceding said portion of said extended process and for generating an expected measurement signal;
• a first summer for receiving said expected measurement signal and a measurement signal from a sensor associated with said parallel inferential control loop and sensing said extended process at the location for said parallel inferential control loop, said summer generating a difference signal;
• a reset model corresponding to said portion of said extended process for receiving a reset input signal from a parallel inferential control loop for controlling a preceding portion of said extended process and generating a reset output signal for decoupling control of said portion of said extended process from said preceding portion of said extended process;
• a second summer for combining said difference signal and said reset output signal to generate a deviation signal;
• a controller for receiving said deviation signal and a setpoint signal for said portion of said extended process to generate a loop control signal for said portion of said extended process;
• and
• a third summer for summing said loop control signal and a control signal representative of control of all parallel inferential control loops controlling succeeding portions of said extended process.

A method for controlling an extended process including a process beginning end and a process finishing end by means of a plurality of parallel inferential control loops, said method comprising the steps of:

• generating actual measurement signals for spaced locations ranging from said beginning end of said extended process to said finishing end of said extended process, said spaced locations each corresponding to one of said plurality of parallel inferential control loops;
• generating expected measurement signals for said spaced locations of said extended process;
• combining said actual measurement signals and said expected measurement signals to generate difference signals;
• generating reset output signals representative of deviations compensated by preceding parallel inferential control loops;
• combining said difference signals and said reset output signals to generate deviation signals;
• combining said deviation signals with setpoint signals to generate control signals for each of said parallel inferential control loops;
• and
• combining said control signals to generate a total control signal for control of said extended process at said beginning end of said extended process.