Abstract: The present invention relates to a method and apparatus for inspecting the quality of laser welding by monitoring the size of a metal molten pool (i.e., weld metal) during a laser welding process. The present invention provides a method and apparatus for inspecting the quality of laser welding, in which a new type laser welding quality inspection system is implemented in which one sensor signal and one filtered electrical signal of the plasma light can be used to perform a correct welding quality inspection through the development of a filtering method of an electrical signal of the plasma light, thereby facilitating a laser welding quality management and making possible its example application to a vehicle body laser welding process.

Abstract: The present invention relates to an apparatus and method for capturing an image of a welding spot during a welding task and determining an accurate position of the welding spot based on the captured image in order to perform an accurate welding task. A beam splitter splits a path of light reflected from a welding section of a spacer grid from a path of a laser beam generated from a laser generator. An image sensor receives light reflected from a welding spot of the spacer grid, and senses and stores an image of the spacer grid. Welding control means controls the image sensor to capture the image of the spacer grid, receives the image of the spacer grind from the image sensor, calculates an accurate position of the welding spot based on the received image, corrects position information of the welding spot based on the calculated position, and controls a servo motor so that the laser generator can accurately collimate the welding spot based on the corrected position value.

Abstract: A laser, aimed at a flyer plate tab, causes optical energy to be directed at the tab, specifically, at a top surface thereof. Energy impacting the tab accelerates the tab into an impact with a target sheet in a time on the order of about 10?5 seconds. The impact occurs in excess of 100 m/s, resulting in a metallurgical bond between the tab and the target sheet. The laser preferably strikes the top surface in a normal direction, based upon an initial angularity of the tab relative to the target. The laser emission may be augmented by an ablative layer on the top surface or a transparent covering on the top surface that reacts against the expanding gas from ablative activity on the top surface. The weld is formed without physical contact between the welding device and the tab.

Abstract: A laser working apparatus includes: a laser head provided with a reflector which changes the direction of any one of a laser beam and a visible light; a robot which moves the laser head; and a robot control apparatus. When laser working is performed, the robot control apparatus controls the laser head so that the laser beam can draw a predetermined working pattern on the basis of a predetermined working position on a work piece. When an operation checking work is performed, the robot control apparatus controls the laser head so that the visible light beam can be emitted only to a reference position of the working pattern.

Abstract: A laser processing head mounted on a robot arm moves from with a constant speed in a direction from a welding point to a next welding point, while a reflection mirror continuously turns in order to maintain laser beams focused on the welding point until the welding at the welding point is completed, and the reflection mirror quickly turns to shift the focus of the laser beams onto the next welding point when the welding at the welding point is completed.

Abstract: A method for fabricating a composition of Zr-rich bulk amorphous alloy includes providing a weld member and a base, both made of Zr-rich bulk amorphous alloy, and welding the weld portion of the weld member to the base by a pulsed laser in a protective gas environment. A maximum power of the pulsed laser exceeds or equals 3.5 kW, and a welding rate exceeds 2 mm/sec.

Abstract: An exemplary method for making backlight module frame includes: providing a plurality of metallic sheets cooperatively defining a frame shape, and a positioning device comprising a worktable and a plurality of positioning portions defined at corners of the worktable, wherein each metallic sheet comprises a first positioning protrusion corresponding to the positioning portions, positioning the metallic sheets on the worktable of the positioning device with the first positioning protrusions of the metallic sheets engaging with the positioning portions of the positioning device, welding the metallic sheets together to form a semi-manufactured frame, and pressing the semi-manufactured frame to form a backlight module frame.

Abstract: In a method of repairing a structural component, especially a stator-side structural component such as a housing or a guide vane ring of a gas turbine, a damaged section is separated-out along a separating line and removed from the structural component, and a new section that replaces the removed damaged section is connected with the structural component by welding along the separating line to produce a weld seam. The damaged section is separated-out from the structural component so as to minimize the length of the separating line and thus the weld seam. Depending on the material thickness distribution of the component along the separating line, material is removed from the structural component to provide the most uniform possible material thickness along the weld seam. After connecting the new section with the structural component by welding, at least the removed material is renewed by laser powder deposit welding.

Abstract: Conventional welding methods have the disadvantage of producing worse welded joints at the beginning of the process than in the later course of the method. The method in question uses an initializing plate on which the welding process is begun and then once a consistent quality can be achieved for the welded joint continues onto the points for repair.

Abstract: A method of repairing an aperture and adjacent defect in a part which is started by removing one or more defects adjacent an aperture in a base material. The material is removed to create a weld seam that extends past an area of high stress concentration on the aperture. An insert of material containing a profile that corresponds to the profile of the base material removed adjacent the aperture and a combination top and runoff plate that encompasses the insert of material are provided. A backing plate is inserted underneath the combination top and runoff plate and insert such that there remains an air space between the backing plate and the combination plate which prevents the combination plate from becoming fused to the backing plate during a welding process. The insert is welded to the base material, and the backing plate is removed. Excess material is removed from the insert to obtain an aperture containing a profile essentially the same as the profile of the aperture prior to initiating the repair.

Abstract: A laser cutting/welding installation including a laser head configured to deliver a laser beam and a cooling device for cooling the laser head is disclosed. The laser beam is designed to generate a hot spot on a workpiece by incidence thereon and form a solder bath from a portion of the workpiece affected by the hot spot. The cooling device includes a vortex tube with a compressed gas inlet supplied with a compressed gas, a cold gas outlet, and a hot gas outlet. The vortex tube cold gas outlet is plumbed directly to an interior volume of the laser head and configured to deliver a cold gas directly to the interior volume of the laser head for cooling thereof.

Abstract: Together with a scanner device, an air blower is provided above a workpiece, and the air blower exhausts air in the shape of a ring toward the workpiece, the air in a ring shape surrounding an optical axis of a laser beam emitted from the scanner device. A housing of the air blower is formed in a ring shape, a ring-shaped cavity is formed in the housing, an inner ring member is attached to an undersurface of the housing, an outer ring member is attached to an outer peripheral side of the inner ring member, and a ring-shaped exhaust port is formed between the inner ring member and the outer ring member. An exhaust direction of the air is defined by inclination of an outer-peripheral-side end surface of the inner ring member and inclination of an inner-peripheral-side end surface of the outer ring member (FIG. 2).

Abstract: Device for remote laser welding of metal sheet structures comprises an anthropomorphous robot onto whose wrist is mounted an accessory device carrying a focusing head for the laser beam coming from a laser source, as well as means for oscillating the pointing direction of the focused laser beam around one oscillation axis. During welding the robot shifts the accessory device along a given trajectory and at a given speed, while the pointing direction of the focused beam is oscillated to as to allow the area of structure that is lighted by the laser beam to shift at a speed and/or along a trajectory not depending directly on the shifting trajectory and speed of the accessory device carried by the robot.

Abstract: An exemplary method for making backlight module frames includes: method includes: providing a first metallic sheet and a second metallic sheet, each of the first and second metallic sheets having at least two L-shaped portions connected side by side and oriented in the same direction; welding the two metallic sheets to form a plurality of connected semi-manufactured frames corresponding to s subsequent backlight module frame; and pressing the connected semi-manufactured frames to form a plurality of backlight module frames. The method costs less welding time and it is convenient for the backlight module frames to be mass-produced.

Abstract: A monitoring device by laser shadowscopy, which comprises a light emitter (5) and receiver (6), mounted on an arm (8) oscillating at will around two joints (13, 14), in order to restore the image of the monitored profile more accurately. An important application relates to welding methods and especially in hollow beveled edges.

Abstract: A laser-arc hybrid welding head performs laser light irradiation and arc discharge of a base material to weld the base material by combined use of laser welding and arc welding. The welding head includes an optical fiber for transmitting laser light used in laser welding and an arc electrode for generating an arc between the arc electrode and the base material. The optical fiber is disposed such that an optical axis thereof crosses an axis of the arc electrode at a predetermined angle.

Abstract: The invention relates to a machining head with integrated powder supply for deposition welding using laser radiation. A machining head in accordance with the invention can in particular be used for deposition welding at a high deposition rate. In the machining head in accordance with the invention, the laser radiation is directed to supplied powder and to a material surface with a focal spot. The powder supply takes place symmetrically to the axial feed direction with a plurality of channels arranged oppositely. The channels are aligned at an obliquely inclined angle so that powder discharged from them is supplied into the focal spot of the laser radiation from two mutually oppositely disposed sides over the total width of the focal spot with respect to the axial feed direction.

Abstract: The present invention relates to a laser welding system comprising a source (1) for a laser beam, a collimator (2) which is adapted to collimate the laser beam, and a focusing means (3) which is adapted to focus the collimated laser beam onto a concentrated point on a workpiece (4) to be welded. In order to allow for a homogeneous welding region, an optical element (5) is arranged between the collimator (2) and the focusing means (3), the optical element being adapted to spread a power distribution of the laser beam along a first direction running at an angle to an axis of the collimated laser beam. According to an alternative solution, the optical element (5) is arranged between the source (1) for the laser beam and the collimator (2).

Abstract: The present invention relates to hard coating of ferrous metal substrates using a laser beam with diamond particles in a metal matrix produced from precursor powders of metals which bond to the diamond particles and to the ferrous substrate. The hard coating is particularly useful for white iron castings for pumps (200) used in piping tar sand and water mixtures.

Abstract: A method of retouching metal parts joined by brazing at high temperatures is disclosed. The brazed zones are retouched by a retouching laser. The peak power of the retouching laser is between 1500 and 3000 W. The retouching laser is used in pulsed mode.

Abstract: A method for producing a stainless steel three-ply clad sheet for a fuel cell separator comprises heating a source blank and then performing rough rolling, hot rolling and cold rolling thereto, whereby the clad steel sheet for the fuel cell separator or a solid polymer type fuel cell separator thereby is obtained. The source blank for the clad steel sheet is composed of a stainless steel utilizing 0 to 0.3% B as a core component and a stainless steel containing 0.3 to 2.5% B as face component. The source blank is made using face components, a core component, tabs and protectors and performing steps including bonding of the tabs and protectors to the face components, removing portions of the tabs and protectors, piling of the face components to the core component, and further bonding of the face and core components together to form the source blank.

Abstract: A welding method and apparatus for welding workpieces together by conducting a forward hybrid welding process on a joint region that includes a weld seam defined by and between faying surfaces of the workpieces, and then conducting an aft hybrid welding process on the joint region. The forward hybrid welding process simultaneously causes a forward laser beam and a forward electric arc to travel along the joint region, which in combination penetrates the weld seam and forms a weld pool that solidifies to form a weldment. The aft hybrid welding process utilizes an aft electric arc and an aft laser beam to produce a second weld pool that remelts and mixes with the weldment. On cooling, a weld joint is formed that is capable of deeply penetrating the weld seam of the joint region.

Abstract: A welding method and apparatus for welding workpieces together by conducting a laser beam welding process on a joint region that includes a weld seam defined by and between faying surfaces of the workpieces, and then conducting a hybrid laser arc welding process on the joint region. The laser beam welding process entails causing a first laser beam to travel along the joint region, penetrate the weld seam and form a weldment. The hybrid laser arc welding process remelts the weldment by simultaneously causing an electric arc and a second laser beam to overlap and travel along the joint region and form a weld pool in the weldment. On cooling, a weld joint is formed within the joint region and its weld seam.

Abstract: The invention concerns a laser device for joining work pieces made of plastic by means of beam welding technology, with a processing head that has focusing devices for the laser beam. Here, the focusing device that is closest to the work pieces has a rotatably supported cylinder lens in the shape of a roller that focuses the laser beam along a single axis and presses the work pieces together in the form of a line in an area around the impact point of the laser beam. In order to enable the cylinder lens to always contact the surface of the work piece facing the processing head in a precisely tangential manner, the processing head has a pendulum-type suspension for the rotatable cylinder lens. This also makes it possible for the contact pressure exerted by the processing head to always act perpendicularly on the work pieces so that they are pressed together in all welding places in the same way in a defined manner during the welding process.

Abstract: A laser heating apparatus for metal eutectic bonding is disclosed in the present invention. The laser heating apparatus has a table for supporting a substrate having a first metal; a holding unit, located above the table and moving with respect to the table, for holding an object having a second metal above the table; and a laser generator, installed below the table and moving with respect to the table, for providing a laser beam which passes through the table and the substrate to melt the first metal, to facilitate the first metal to adhered to the second metal, thereby bonding the substrate with the object. The apparatus provides good heat conduction and stability. Furthermore, the holding unit used is not only for positioning, but also exerting a pressure on the bonding metals. It makes eutectic bonding process easier and more efficient.

Abstract: An object of the present invention is to provide a method for producing a hermetically sealed container, which method comprises conducting hermetic sealing of a container for beverage or food using a laser welding method, whereby the process speed of the sealing process can be made fast, strict control of the scanning position of laser spots is unnecessary, partial oversupply of energy does not occur easily, and there is no reduction in the welding area or welding strength per area due to the gathering of water drops.

Abstract: Equipment (1) with which to fuse to each other at least two superposed laminar bands (2) and comprising two compressing members (3, 4) subtending between themselves a compression gap (5) through which said laminar bands (2) are guided. Additionally the equipment (1) comprises a laser (7) configured in a manner to transmit laser radiation (8) passing through the first compression member (3) and the compression gap (5) in the direction of the second compression member (4). According to the invention, the second compression member (4) is constituted by a resiliently borne sheetmetal-like support (9) which mechanically resiliently loads the laminar bands (2) in the compression gap (5) in the direction of the first compression member (3).

Abstract: A method for joining dissimilar materials of sensor button for measuring torque is illustrated. The dissimilar materials can be welded together by laser welding. The parts can be cleaned and held together firmly by a fixture and welded with established machine parameters. The method of micro-crack free weld joint can give a robust joint for the life time of the automotive which mandate for the function of torque sensor to facilitate the positive strain transfer from the parent material.

Abstract: A welding system has: a welding mechanism, a reception laser light source, a reception optical mechanism, an interferometer, a data recording/analysis mechanism and a data recording/analysis mechanism. The reception laser light source generates reception laser light so as to irradiate the object to be welded with the reception laser light for the purpose of detecting a reflected ultrasonic wave obtained as a result of reflection of a transmission ultrasonic wave. The reception optical mechanism transmits, during or after welding operation, the reception laser light generated from the reception laser light source to the surface of the object to be welded for irradiation while moving, together with the welding mechanism, relative to the object to be welded and collects laser light scattered/reflected at the surface of the object to be welded.

Abstract: A welding tool is configured with a housing enclosing a fiber laser system which is operative to produce a weld seam for connecting two workpieces. The fiber laser system includes a focusing optic configured to focus the output beam of the system so that it propagates through an elongated slit formed in the bottom of the housing. The fiber laser system is capable to move along a predetermined path extending parallel to the longitudinal direction of the slit and limited by the perimeter thereof. The output beam is generated only when the slit sits upon at least one of the workpieces.

Abstract: A method for connecting pipe members for an endoscope includes the steps of arranging two pipe members each made of a corrosion-resistant alloy material by fitting one in another so that a passage is defined through the two pipe members, jetting inert gas toward an exterior of an area at which the two pipe members are to be connected, injecting inert gas through the passage defined through the two pipe members, and connecting the two pipes by laser welding such that a laser beam is irradiated toward the exterior of the area at which the two pipe members are to be connected with jetting the inert gas toward the exterior of the area at which the two pipe members are to be connected and injecting the inert gas through the passage defined by through the two pipe members.

Abstract: An apparatus for comprises a base, a wall, and an opening in the wall. The base has a first end, a second end, and a channel system. The channel system is located closer to the first end than the second end of the base. The wall extends from a side of the base to partially enclose the channel system. The opening in the wall is located closer to the second end than the first end. The shape of the wall is capable of retaining a gas introduced through the channel system in a welding location and causing the gas to move away from the channel system and through the opening in the wall.

Abstract: A method of repairing a turbomachine blisk having at least one damaged zone by build-up of metal in the damaged zone using a laser build-up welding machine is disclosed. The method includes preparing the damaged zone by machining the damaged zone to obtain a zone of defined profile to be repaired, build-up welding of a start-of-run test piece that includes the defined profile using the laser build-up welding machine, checking geometric and metallurgical quality of the test piece, and build-up welding the zone to be repaired of the blisk using the laser build-up welding machine.

Abstract: An apparatus and method are provided for the laser deposition welding of powdery welding material having increased flexibility and reduced costs, in particular for systems engineering. The powdery welding material is conveyed via a nozzle coaxial with respect to a laser beam directed in a focused manner with a constant focal length onto a processing region of a workpiece through the nozzle onto the processing region. A plurality of optical elements are statically arranged in a laser optical unit for the shaping and beam guidance of the laser beam. The laser optical unit it attached to a processing head and can be moved with the processing head parallel to the optical axis of the laser beam by a first drive. The plane of the focal point can thereby be changed with respect to the workpiece surface and to the size of the surface of the focal point in the processing region. The nozzle can be moved independently of the laser optical unit parallel to the optical axis of the laser beam by a second drive.

Abstract: A laser welding pressure unit comprises a housing, a rotating element, and a foot. The housing may attach to a laser head. The rotating element may include an outer ring rotatably coupled to an inner ring, wherein the outer ring is coupled to the housing. The foot may couple to the inner ring such that the foot rotates with respect to the housing. The foot may also be configured to contact an upper surface of a metal sheet and may be oriented such that while the metal sheet is being welded, the foot rotates about a central vertical axis and the laser welding pressure unit is able to move in any direction without the foot breaking contact with the surface.

Abstract: A weld zone of T-piping and its neighborhood are efficiently laser-heated to remove residual stress. For this purpose, the weld zone of a T-piping (50) is irradiated and heated with a laser beam emitted from a laser head (10) to remove residual stress. At this time, a rotating travel cart (3) travels along a ring rail (2) to adjust the position of the laser head (10) in a ?-direction, a vertical slide (4) slides to adjust the position of the laser head (10) in a Z-direction, a radial slide (5) slides to adjust the position of the laser head (10) in an L-direction, an arcuate piece slide (7) slides along an arcuate piece to adjust the ?-direction of the laser head (10), a laser head support portion (9) turns to adjust the ?-direction of the laser head (10), and oscillation adjusts the position of the laser head (10) in a ?-direction.

Abstract: The invention relates to a compressed air tank for utility vehicles, comprising a tubular or cylindrical jacket sealed at both ends by way of welded outer bases. At least one outer base and/or the jacket is provided with a hole. A sleeve is welded onto the hole. At least the inside of the compressed air tank is provided with an inner coating. The contact surfaces between the jacket and the outer bases are adapted such that the contact surfaces abut one another and such that the contact surfaces can be welded together without using any weld material through laser welding. The sleeve is welded onto the hole by way of laser welding or CD welding. The inner coating of the tank is manufactured by powder coating.

Abstract: A laser welding tool comprises a first and a second tool part for fixing a first welding article to a second welding article. The two welding articles are arranged at least partially between the two tool parts. The second tool part comprises at least two partial elements which are displaceable independently of one another toward the first tool part for pressing the second welding article against the first welding article.

Abstract: A method and an apparatus for repairing gas-turbine blisks uses an endoscope 15 provided with processing optics featuring a flexible light guide arrangement 16. A laser source 9 is connected to a flexible optical fiber arrangement 10, with a filler material feeder 7 for supplying welding flux via a flexible line 8, with a water supply 11 connected to a flexible line 12, and with an inert gas supply 13 connected to a flexible line 16 for supplying inert gas, with the flexible lines 8, 12, 14, the flexible light guide arrangement 16 and the flexible optical fiber arrangement 10 being combined to form a flexible long repair implement 17 at least at its distal end areas.

Abstract: In a deposition method of forming a buildup on a single crystal or directionally solidified crystal parent material, metal deposition is performed from an extension in a preferential growth orientation of parent material crystals while forcedly cooling a portion of the parent material somewhat below a processed surface and beforehand giving a temperature gradient to the parent material so that a maximum temperature gradient is oriented along the preferential growth orientation of parent material crystals.

Abstract: A welding apparatus includes a table on which first, second and third blanks are to be fixed, a first positioning station where the first and second blanks are fixed on the table, a first welding station where the first and second blanks are welded together at their abutting surfaces, a cutting station where the abutting surface of the first or second blank or both is cut into a predetermined shape, a second positioning station where the third blank is fixed on the table, and a second welding station where the third blank and the first or second blank or the first and second blanks are welded together at their abutting surfaces.

Abstract: A laser welding apparatus and method for easily adjusting a laser focusing position according to a distance from a laser irradiating device to a laser irradiating point on a work piece, or a welding point. A post-collimation laser diameter is measured when the laser emitting end has an optimal laser diameter on the work piece with respect to the distance from the laser processing head to the work piece. Corresponding data is stored with the above distance and the post-collimation laser diameter corresponding to each other. During welding, a diameter of the laser beam passing through a collimate lens is measured by a laser diameter measuring device. The post-collimation laser diameter is adjusted to be an optimal value according to the corresponding data.

Abstract: A method for displaying laser irradiation state and a system of displaying laser irradiation state, enabling to monitor laser irradiation state correctly and rapidly even when a laser irradiation direction varies, and a scanner head and a work are relatively apart, characterized that laser light is irradiated at the surface of a work, in a specified pattern shape different from a process pattern from a scanner head, in advance of process by irradiation of laser light at a work by a scanner head mounted at a robot hand.

Abstract: A method and device are provided for welding structural parts, preferably of a gas turbine, especially of an aircraft engine. A structural component is laser-welded by means of at least one laser source, the one or more laser sources being operated in a pulsed mode. Pulse duration and/or pulse shape and/or output of the one or more laser sources are adjusted in a variable manner. The wire advance of the welding wire is controlled subject to the pulses of the one or more laser sources.

Abstract: A laser welding system includes a free-spacing beam delivery laser head having a linear array of at least two laser diodes. Each of the diodes generates a laser beam of a predetermined wavelength and spectral width, the laser beams adapted to weld a workpiece having a first component and at least one other component to be welded to the first component, the first component being substantially transmissive to the wavelength, the other component being substantially absorptive of the wavelength. A lens is spaced a predetermined distance from each of the laser diodes, each of the lenses adapted to focus the respective laser beam into a focused laser beam segment, thereby forming a continuous line of laser energy from a substantially serial combination of each focused laser beam segment. The continuous line of laser energy is in a plane containing the workpiece, and is substantially orthogonal to the workpiece translation direction.

Abstract: A system for identifying a laser machining nozzle on insertion of the laser machining nozzle into a laser machining head is provided. On its region insertable into the laser machining head, the laser machining nozzle has a shaping. Means for detecting or sensing the shaping are provided in the receiving region of the laser machining head provided for the laser machining nozzle.

Abstract: A first laser beam is radiated to a first radiation position of a welding object while intersecting a wire, and a second laser beam is radiated to a second radiation position that is spaced a predetermined distance from a target position of the wire. Arc welding is performed between the wire and the welding object while radiating the first laser beam and the second laser beam such that the first radiation position, the second radiation position, and the target position are disposed on a welding line of the welding object. In this way, it is possible to prevent the generation of spatter and perform welding at a high rate, without increasing the size of a molten pool.

Abstract: A butt welding system and a butt welding method of steel plate by which the quality of a product can be ensured. Butting portions of blank members (1,2) to be joined together are butted and a predetermined butting load is applied to the butting portion, wherein the blank members (1,2) are moved relatively in the direction of the welding line thus matching the butting portions. Protrusions and recesses formed on each butting portion of each blank member (1,2) are flattened, whereby linear precision at each butting portion of each blank member (1,2) is enhanced as compared with a case where the butting portions are not matched. Since the gap is reduced extremely at the butting portion, welding is facilitated at the butting portion. Good welding beads are thereby obtained at the butting portion and the quality of a product is ensured.

Abstract: An electrically conductive substrate is provided with a predetermined electrical pattern. A solder paste is deposited onto the electrically conductive substrate at pre-defined interconnection locations. A first encapsulant layer provided with a pattern of openings is placed onto the electrically conductive substrate. Back-contact solar cells are placed on the first encapsulant layer so as to have a match of the electrical pattern of the back-contact solar cells with the electrical pattern of the electrically conductive substrate. A second encapsulant layer is placed on the back-contact solar cells with a glass layer placed on the second encapsulant layer. Heat and pressure are applied to the components to cause the encapsulant materials to flow and form a monolithic photovoltaic module. A laser is applied to the solar cell from the side of the glass layer to cause the solder paste to reflow between each interconnection location and its matching connection location on the back-contact solar cell.

Abstract: A method for monitoring the quality of laser-machining processes (500), in particular laser-cutting or laser-welding processes, including the operations of: acquiring via sensor means (540), in particular optical sensors, a machining-process signal (Xp) and calculating from said signal representing the process (Xp) parameters (E1, E2, DC) that represent the machining quality during the laser-machining process; and making available (130) corresponding reference parameters (E1r, E2r, DCr) representing a given machining quality, which are calculated from a process reference signal (Xr) acquired via said sensor means (540).