Pumps – Condition responsive control of pump drive motor – By control of electric or magnetic drive motor
Reexamination Certificate
1998-06-08
2001-01-09
Thorpe, Timothy S. (Department: 3746)
Pumps
Condition responsive control of pump drive motor
By control of electric or magnetic drive motor
C417S012000, C323S909000, 36, 36, 36, 36, C137S084000, C137S085000, C062S222000, C318S610000
Reexamination Certificate
active
06171066
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an automatic pneumatic pressure control apparatus for use as an electropneumatic transducer or a pneumatic pressure actuator employing such an electropneumatic transducer, and a method of controlling such an automatic pneumatic pressure control apparatus.
2. Description of the Related Art
Electropneumatic transducers constitute one category of automatic pneumatic pressure control apparatus which are actuated by an electric input signal supplied as a manipulated variable (also referred to as a “manipulated variable signal”) according to an automatic control process. In response to the electric input signal, the electropneumatic transducer generates a pneumatic pressure as an output signal known as a controlled variable or a controlled variable signal, and an electric signal corresponding to the pneumatic pressure is fed back to the electropneumatic transducer.
A flow control valve or the like is connected to an outlet port of the electropneumatic transducer, making up a pneumatic pressure actuator as an automatic pneumatic pressure control apparatus. In response to an electric input signal (manipulated variable) applied to the electropneumatic transducer, the pneumatic pressure actuator produces an output signal (controlled variable) representing the opening of the valve member of the flow control valve, and the output signal is fed back to the pneumatic pressure actuator.
One known automatic pneumatic pressure control apparatus is disclosed in Japanese laid-open patent publication No. 7-4401 entitled “Electropneumatic transducer apparatus and actuator system employing same”, filed by the present applicant.
Generally, automatic pneumatic pressure control apparatus employ the principles of the PID (Proportional plus Integral plus Derivative) control mode. According to the PID control mode, an offset-free, stable, and accurate response can be achieved when supplied with a signal that changes stepwise from a value “0” to a value “1”, such as a step signal (step input), for example, as a reference signal (also referred to as a “reference input” or an “input signal”).
Pneumatic devices suffer a longer dead time which is consumed after a manipulated variable is supplied until a controlled variable is actually generated by a controlled object, than hydraulic devices. If the controlled object has a large dead time, then the overall follow-up controllability of the pneumatic devices is poor. Specifically, if the manipulated variable (and hence the controlled variable) is smaller, then a time required until the controlled object responds is longer, i.e., the controlled object responds slowly, and if the manipulated variable (the controlled variable) is larger, an overshoot or a damped oscillation tends to occur in the controlled object.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide an automatic pneumatic pressure control apparatus which makes a response time shorter (allows a quicker response) when a manipulated variable (a controlled variable) is smaller, and which is substantially free of an overshoot or a damped oscillation when the manipulated variable (the controlled variable) is larger, and a method of controlling such an automatic pneumatic pressure control apparatus.
The above and other objects, features, and advantages of the present invention will become more apparent from the following description when taken in conjunction with the accompanying drawings in which preferred embodiments of the present invention are shown by way of illustrative example.
REFERENCES:
patent: 3611115 (1971-10-01), Friedbach
patent: 4214300 (1980-07-01), Barlow et al.
patent: 4279192 (1981-07-01), Kleinwaks
patent: 4579137 (1986-04-01), Brandt, Jr.
patent: 4637546 (1987-01-01), DeMeyer
patent: 4756669 (1988-07-01), Hata
patent: 4804009 (1989-02-01), Bergmann
patent: 4834622 (1989-05-01), Schuh
patent: 4903192 (1990-02-01), Saito et al.
patent: 5093609 (1992-03-01), Sakamoto et al.
patent: 5162987 (1992-11-01), Sambhu
patent: 5325288 (1994-06-01), Satou
patent: 5331541 (1994-07-01), Ueda et al.
patent: 5384526 (1995-01-01), Bennett
patent: 5493488 (1996-02-01), Castle et al.
patent: 5532925 (1996-07-01), Gassman
patent: 5745362 (1998-04-01), Hiroi et al.
patent: 5950443 (1999-09-01), Meyer et al.
patent: 7-4401 (1995-01-01), None
patent: 7-310843 (1995-11-01), None
patent: WO 93/18445 (1983-09-01), None
Invensys Building Systems, Basics of PID Control, http://www.siebe-env-controls.com
ews/links/pid.htm, pp. 1-5, Jan. 1996.
Control Engineering Online, Vance J. VanDoren, Self-Tuning Controllers AutoSelct P, I, D Values, http://www.controleng.com/archives/1997/ct10901.97/09bbas.htm, pp. 1-2, Sep. 1997.
Patent Abstracts of Japan, vol. 17, No. 139 (M-1385), Mar. 22, 1993, JP 04-316701, Nov. 9, 1992.
Aki Tomohiko
Irokawa Kenji
Brown Steven
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
SMC Kabushiki Kaisha
Thorpe Timothy S.
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