Electricity: measuring and testing – Magnetic – Displacement
Reexamination Certificate
1999-01-20
2001-10-16
Oda, Christine (Department: 2862)
Electricity: measuring and testing
Magnetic
Displacement
C318S594000
Reexamination Certificate
active
06304077
ABSTRACT:
The invention relates to a method for defining the position of an actuator of a paper or board machine, the position of the actuator being measured in the method by means of a measuring signal proportional to the rotation of a shaft of the actuator, the measuring signal comprising successive pulses.
The invention further relates to an apparatus for defining the position of an actuator of a paper or board machine, the apparatus comprising measuring means for measuring the position of the actuator, the measuring means being arranged to generate a measuring signal comprising successive pulses and being proportional to the rotation of a shaft of the actuator.
Actuators are used, for example, to control the flow of different media, such as water and steam, in different processes. The actuators control a valve, nozzle or the like supplying the medium. The actuator can be a motor, cylinder or the like, which can be controlled in many different ways, for example mechanically, electrically, hydraulically or pneumatically.
It is previously known to use measuring devices in conjunction with the actuators of a paper machine to define the position of the actuator of the paper machine, the measuring devices generating binary pulses, whereby the position of the actuator is proportional to the number of pulses. As the shaft of the actuator rotates, the measuring device detects the rotating movement and sends a measuring pulse as a certain point of the shaft of the actuator revolves past the sensor of the measuring device. Such a solution is disclosed in GB 2 225 415, which discloses a fluid flow valve controlled by a stepping motor. The position of the valve can be measured by an optical shaft encoder. A problem in the use of the measuring device generating binary pulses is that the actuator cannot always be positioned sufficiently accurately. Problems are also posed by delays in the control of the positioning.
The object of the present invention is to provide a method and an apparatus in which the above drawbacks are avoided.
The method of the invention is characterized in that the intervals between the pulses are divided into parts, and the parts of the divided pulse intervals are utilized in defining the position of the actuator between the pulses.
The apparatus of the invention is further characterized in that the apparatus comprises means for dividing the intervals between the pulses into parts and for defining the position of the actuator between the pulses utilizing the parts of the divided pulse intervals.
The essential idea of the invention is that the position of the actuator of a paper machine is measured by a measuring signal proportional to the rotation of the shaft of the actuator, the measuring signal comprising successive pulses, and that the intervals between the measuring pulses are divided into parts, and that the parts of the divided pulse intervals are utilized in defining the position of the actuator. In a preferred embodiment of the invention, each measuring pulse calibrates the accuracy of the parts of the divided pulse intervals. In a second preferred embodiment, the division of the pulse intervals into parts makes i possible to estimate the position of the actuator at an instant between the pulses. In a third preferred embodiment the measuring pulses are generated by arranging a detection point, such as a magnet, in conjunction with the shaft of the actuator, and by arranging a Hall sensor in the apparatus, the Hall sensor outputting a pulse as the shaft rotates and the detection point passes the Hall sensor.
The advantage of the invention is that the division of the interval between the measuring pulses into parts makes it possible to define the accurate position of the actuator even between the pulses. When the parts of the divided intervals between the pulses are calibrated by the input pulse measured, good accuracy is maintained. As the position of the actuator can be estimated even between the pulses, it is possible to eliminate delays of the feedback positioning from the control. The use of magnets and Hall sensors to generate pulses provides a simple actuator that endures even difficult process conditions.
REFERENCES:
patent: 3981767 (1976-09-01), Al-Shaikh
patent: 4081995 (1978-04-01), Griffith et al.
patent: 4571530 (1986-02-01), Sweeney, Jr.
patent: 4814704 (1989-03-01), Zerrien, Jr. et al.
patent: 5297048 (1994-03-01), Gauer
patent: 5317614 (1994-05-01), Davis et al.
patent: 2225415 (1988-11-01), None
patent: 60-262010 (1985-12-01), None
patent: 9320346 (1993-10-01), None
Patent Abstract of Japan of JP 60262010 of Dec. 1985.
Sanaksenaho Juha
Saunisto Kimmo
Sorsa Jukka
Ladas & Parry
Metso Paper Automation Inc.
Oda Christine
Zaveri Subhash
LandOfFree
Method and apparatus for defining the position of an... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method and apparatus for defining the position of an..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method and apparatus for defining the position of an... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2575664