Abstract: A Kalman filter algorithm is used for estimation in a feedback control system for a moving web. Matrices of the Kalman filter algorithm are solved with reduced computational complexity. One of the matrices is solved as a diagonal matrix for both state prediction and covariance and another matrix for gain is solved merely as a vector.

Abstract: A scanner for moving sheet material such as a paper-making machine provides the gauging heads which measure parameters such as basis weight and moisture entirely inside an enclosed tubular beam. Each gauging head is driven by a single belt which both drives the gauging head in a cross direction perpendicular to the moving sheet direction and provides for dust and dirt protection by covering a slot in the beam, except where the gauging head is located.

Abstract: A decoupling controller for use with a process such as paper-making having two input variables such as stock flow and steam pressure and two output variables such as moisture and basis weight. Decoupling is accomplished by the use of linked internal model controllers where for each individual unit of the linked pairs, a P.I.D. (proportional, integral, derivative) unit includes all of the feedback loop gains and then the process itself is modeled by a first order transfer function and deadtime units with two cross-linked error signals fed back. A specific technique of cross-linking the internal model controllers eliminates cross-coupling between the input and output variables.

Abstract: A cross-direction dryer for typically drying a continuous web of paper or paper to which coating has just been applied provides both for baseline drying and a linear moisture profile by the use of respectively gas and electric heating portions of the heater units. Profile control is normally provided by control of the voltage to electric heating lamps. Such heating lamps are suspended over a large area gas burner to provide a combined increased infrared heat output. Encapsulation of the heating lamps with quartz provides for reradiation of the medium wavelength radiation produced by the gas burner. Thyristor switching for the quartz halogen heat lamps may be located adjacent to each heater unit and cooled by the combustion air for the gas burners.

Abstract: A caliper gauge for moving sheet material such as paper which measures the thickness of the paper accommodates bumps or holes in the paper by providing at least one side of the caliper gauge with a long continuous smooth arm which because of its mounting in close proximity to the moving sheet, which is partially made possible by the use of air bearings for the upper and lower portions of the gauge, provides a gradual wedge-shaped opening which thus allows the transfer of the momentum of the bump or hole in the paper to gradually overcome the inertia of the measuring arm which is pushed away from the paper. The arm itself is made of a single piece of sapphire and is universally pivoted by the use of a polyimide material adhered to the top of the arm which gives the arm at least 2.degree. of dimensional freedom while still maintaining it aligned in the moving direction of the paper.

Abstract: For measuring basis weight of a moving web in the cross direction scanner of a paper-making machine, an encapsulated nuclear source of Promethium 147 is used because of its wide area of emission. To conserve space it is mounted on a vertical axis. The source in a horizontal plane parallel to the moving web from a stowed position where the source is shielded to an active position where the source emits through an aperture, through the moving web, and to a detector. The x-y array planar type detector uses four detector segments symmetrically arranged around a center and compensates for belt direction misalignment (the belt driving the cross direction scanners) by mathematically manipulating the electrical signals from each detector to eliminate the error term.

Abstract: An air heating and control system, which in one application controls the diameter of a calender roll in the paper making process, includes a row of heater packs proximate to the various zones of the calender roll. Each heater pack has a plurality of electrical heating coils which are at least partially connected in parallel so that failure of one coil does not interrupt power to the remaining coils. Air flowing through the heating coils is heated to a desired temperature and impinges upon the calender roll to expand it as desired. A control system senses a defective coil, which effectively reduces current in a heater pack, and increases the voltage imposed upon that heater pack to again produce the desired power level or heating effect. Thus failure of a heating coil is immediately compensated for.

Abstract: A gloss sensor for determining the gloss of a surface, for example, of moving paper being produced by a paper making machine. The gloss sensor normally is installed in a scanner which scans the moving paper in a crosswise direction. It includes a standard TAPPI light source which impinges upon the paper at a specified angle and the intensity of the detected reflected light is related to gloss. Calibration is provided by an oscillating angle light source which with the same lamp has a direct reference path to the detector. Compensation for tilting or shifting paper is provided by the same oscillating light source which when the paper tilts or shifts still allows a reflected light beam to reach the detector. Change of angle from the standard TAPPI angle due to parallel paper shifts is compensated.

Abstract: A gloss control system especially for use on a super calender roll system uses controllable jets of heated air arranged along the segment of a calender roll not in contact with a paper web to both control the overall gloss level and equalize the expansion and contraction of the roll which would otherwise be affected by the heat sink effect of the paper on the contacted portion of the roll causing an hour-glass effect. The air jet units utilize electrical heating elements and are actually arranged along, for example, 11/2 inch zones of the paper to provide for a differential profile control with relatively cold air on the uncovered ends of the calender roll to compensate for contraction of the center portion of the roll.

Abstract: A caliper gauge for relatively thin moving sheet material is provided by the use of a pair of outer ring air bearings flexibly supported which tend to flatten the sheet. An inner central portion of each ring respectively carries active and passive magnetic circuit means with the passive means being supported by an elongated strap of Kevlar which is elongated in the machine direction of the sheet material. This provides for very low unsprung weight.

Abstract: An arrangement for a process plant which provides heat treatment of strip-shaped products, such as a paper web, the arrangement including a plurality of lamps operating with infrared radiation. Channel means are provided for conducting a supply of air or some other heat treatment medium and directed against the strip undergoing the processing by means of a heat treatment ramp positioned adjacent the strip. The air or some other suitable heat treatment medium is directed and supplied to flow essentially parallel to the strip of the product. The apparatus for supplying the air directs the air parallel to the product being dried, in order to avoid blowing through the product.

Abstract: A measuring gauge for error compensation of a measured characteristic of a moving sheet measures X, Y lateral displacement of the upper and lower transducer heads of a moving scanner in a cross direction across the paper. This is accomplished by the use of two pairs of eddy current sensors centered on a target on the opposed transducer head. Such eddy current transducers sense the pairs of edges of an aperture in the opposed transducer. Alternatively, slope portions of the lower transducer head are sensed. Other correction inputs are provided by measuring the distance from each transducer head to the moving sheet to provide a "Z" correction. All of the foregoing are then utilized along with caliper measurements, if necessary, to provide a corrected characteristic.

Abstract: Exhaust apparatus for a continuous metal strip heat treating plant having means for influencing the continuous strip with air or heat-treatment medium, which is supplied to the continuous strip so as to flow essentially parallel along the strip, and an opening which permits the heat-treatment medium to pass outward from one surface of the continuous strip.

Abstract: In a process for controlling on-line a parameter of a moving sheet, scan data from a cross direction scanning sensor (for example, for moisture) is retrieved from a memory while the sensor reverses direction at a turnaround point. This is accomplished by utilizing the direct memory access (DMA) capability of the existing computer system and plugging into the existing address, data and DMA bus of that system a printed circuit board which halts normal computer operation for minimum periods so as not to interfere with its operation.

Abstract: An arrangement for a process plant which provides heat treatment of strip-shaped products, such as a paper web, the arrangement including a plurality of lamps operating with infra-red radiation. Channel means are provided for conducting a supply of air or some other heat treatment medium and directed against the strip undergoing the processing by means of a heat treatment ramp positioned adjacent the strip. The air or some other suitable heat treatment medium is directed and supplied to flow essentially parallel to the strip of the product. The apparatus for supplying the air directs the air parallel to the product being dried, in order to avoid blowing through the product.

Abstract: A caliper gauge for relatively thin moving sheet material is provided by the use of an outer ring type air bearing, flexibly supported, which is flexibly connected again to an inner air bearing carrying the magnetic measuring components. The outer air bearing (with its juxtaposed mate) tends to flatten the sheet so that minimum movement is required of the independently actuated inner air bearing. Thus, great accuracy is achieved and tearing or marking of the sheet material, such as super calendered or coated grades of paper, is avoided.

Abstract: A power control system for the heat lamps for typically drying a continuous web of paper in order to provide a linear moisture profile locates the actuating thyristor type switch at each zone where the heater lamps themselves are located. Thus, computer control can be centralized and wiring minimized. The parameters of minimum flicker for unity power factor and high resolution power control are achieved by utilizing the timing signals provided by the zero crossings of the three-phase AC line voltage input and controlling either half cycles or partial half cycles for each zone. Computing time is reduced by providing for scratch pad memory tables which can rapidly be scanned or sequenced through by a zone pointer.

Abstract: A controller for a load such as the heater elements of an actuator for drying the various zones or slices of a moving sheet of a papermaking machine includes silicon controlled rectifiers for each zone or slice of the moving sheet whose firing angle is controlled by an external power command signal. This power command signal is processed by a digital signal processor which strobes at a high rate the line voltage and load current to provide a closed loop feedback control technique for power being applied to the load and in addition, the processor, at the same time, has an open loop firing angle control routine which has a fast response time to protect against abnormal conditions within one-half cycle of load voltage.

Abstract: A combination caliper/moisture sensor in the form of a scanner in the cross-direction of sheet material being manufactured by a papermaking machine includes a pair of capacitive plates on opposite sides of the moving sheet material and in substantial contact with it which are utilized for measuring capacitance between the juxtaposed plates which are spaced in accordance with the caliper of the paper. Then a magnetic circuit which provides a flux path through the paper is utilized for measuring caliper which is the independent variable of the capacitance equation which, when solved, yields the dielectric constant. Since there is a known relationship between percent moisture and the dielectric constant, the percent moisture of the sheet material can be determined.

Abstract: A contacting thickness gauge for measuring the caliper of paper includes a U-shaped pole piece on one side of the paper with a return path being provided by a simple ferrite slab on the other side where the magnetic reluctance of the gaps provides a measure of the caliper. The pole piece has one leg of relatively small diameter contacting the paper; the other larger leg of the U-shaped pole piece being spaced from the paper by either jewel or air bearings to minimize the contact with the sensitive surface of the moving sheet material. The area ratio provides for an insensitivity of the gap of the large leg. In addition, the stray self inductance of the windings is eliminated due to the use only of a mutual inductance measurement to determine the final resonant frequency which is a measurement of the caliper.