EP2089183A1

EP2089183A1 - Industrial machine provided with interferometric measuring means

Info

Publication number: EP2089183A1
Application number: EP06821769A
Authority: EP
Inventors: Costantino Florio; Francesco Mezzapesa; Basilio Vescio; Gianpiero Negri; Gianluca Guadagno
Original assignee: Sintesi ScpA
Current assignee: Sintesi ScpA
Priority date: 2006-11-08
Filing date: 2006-11-08
Publication date: 2009-08-19
Also published as: CN101583462A; WO2008056383A1

Abstract

An industrial machine (200) is described comprising: - a moving structural element (2) for adopting different positions in corresponding operating configurations of the machine (200); optoelectronic measuring means (11, 12) of a distance (d) between a first reference axis (al) and a second reference axis (a2) associated to said structural element (2); characterized in that said optoelectronic measuring means (11, 12) comprise a laser interferometer (20) and a measuring reflecting target (12) that are optically coupled to each other and each being associated with one of said reference axes, said laser interferometer including a laser source for emitting a direct electromagnetic radiation to said target (12) and interference means between a reflected electromagnetic radiation from said target and a reference electromagnetic radiation obtained from the direct electromagnetic radiation.

Description

DESCRIPTION

INDUSTRIAL MACHINE PROVIDED WITH INTERFEROMETRIC MEASURING MEANS

The present invention relates to an industrial machine, and particularly, an industrial machine provided with optoelectronic measure means.

As used herein, by "industrial machine" is meant a mechanic machine tool (such as a lathe, a grinding machine, a milling machine, or a drilling, boring machine) , and an electronic machine tool (such as a laser machining machine, electric spark machining machine), a pressure waterjet machine, a Coordinate Measuring Machine

(CMM) , a moving or manipulation machine, and an assembly machine . By "piece" is meant both a piece of machinable material that cab be worked such as, for example, wood metal or plastics, that can be fixed to an industrial machine for machining, and a wall or large portion of solid material that cannot be mounted on an industrial machine, but that can be however reached and worked by means of an industrial machine, or generally any piece that can be handled and manipulated by an industrial machine .

By "machining" is meant each of those operations that an industrial machine can carry out on a workpiece, such as, for example, removal of materials, milling, bending, polishing, and the like, and the surface treatment of the workpiece (such as, varnishing) , and other possible operations on a workpiece, such as measuring, manipulation, moving, or assembly.

More generally, by "operation" of an industrial machine is further meant any of the functions that the machine can carry out, among which, for example, moving a tool within the operating area, holding the tool in any position, machining a workpiece, as well as adjustment, measuring or monitoring operations that can be carried out not only on the workpiece, but also on other mechanical or structural parts belonging to the industrial machine. Typically, as high precision is required when machining a piece of solid material, such as a metal piece, the workpiece is required to be accurately positioned on the machine, and the tool intended for machining the piece and the other mechanical parts that may be involved in the machining are required to move the same in the most precise manner as possible.

In any case, an industrial machine of this type, upon operation, is subjected to stress or vibrations that may be caused, for example, by the interaction of the tool with the material to be worked, or by the handling, often at high speed, of a worktable on which the workpiece is fixed or still by the movement of the tool or other mechanical parts involved in the machining.

Furthermore, geometric deformations can occur in an industrial machine, both of permanent type, e.g. caused by an erroneous assembly or construction of the mechanical parts composing the same, and almost static type, e.g. caused by thermal variations or weight of the parts composing the machine. Accordingly, the need is deeply felt of having an industrial machine capable of providing an operator or control unit with the measure of displacements or dimensional variations to which the machine can be subjected upon operation in order to identify, in real time, machining errors by the industrial machine and increasing the precision of the latter by applying correcting measures. Furthermore, malfunctioning can be limited, while reducing the risk of mechanical failure.

An industrial machine typically consists of stationary mechanical parts and one or more axes, either linear or rotating, which are connected to each other.

By "axis" is meant the assembly formed by two elements, typically the one stationary and the other movable relative to the first one, which are connected to each other such as to be capable of imparting a relative motion to each other via suitable movement transmission means. More particularly, by "linear" axis is meant an assembly of two elements with a relative motion of linear type being imparted therebetween, whereas by "rotary" axis is meant the assembly of two elements with a relative motion of rotary type being imparted therebetween.

In the linear axis, the moving element is slidably moved on the fixed element. The moving element is moved, for example, by means of a rotary electric motor and a suitable mechanical transmission system (or alternatively, directly by a linear electric motor) .

The displacement of the moving element relative to the stationary element is typically indirectly measured by means of an angular measuring system, which is known in the literature with the technical name of "resolver" or angular encoder integral with the rotary motor. Alternatively, the measurement can be directly obtained by means of a linear measuring system, known with the technical name of linear encoder, which typically consists of a graduated scale, typically an optical line, integral with the stationary element and of a reading head integral with the moving element. The measure of the displacement can be further carried out using both measuring systems. More generally, industrial machines consist of one or more linear axes and/or one or more rotary axes.

A first industrial machine Ml of a known type is schematically shown in Fig. 1, which consists of a linear axis AL and is provided with a rotary motor MR, respective mechanical transmission means MTM, a linear encoder EL₇ a rotary encoder ER and a control unit UC. This control unit is associated with the first industrial machine Ml such as to provide a respective command signal to the rotary motor MR based on the information generated by the linear encoder EL and rotary encoder ER.

The first industrial machine Ml in Fig. 1 (having only one linear axis) works, by means of a work tool (not shown in the figure) , a piece that can be fixed to the moving element of the linear axis or stationary element of the axis or a part of the machine, either stationary or moving. The work tool can be either fixed to the moving element of the linear axis, or to the stationary element of the axis, or to a part of the machine, either stationary or moving.

A portion of a second prior art industrial machine M2 consisting of more linear axes (ALl, AL2, AL3) is schematically shown in Fig. 2. In Fig. 2, for clarity purposes, motors, mechanical transmission means, measuring systems and control units are not shown. Generally, an industrial machine with more linear axes and one ore more rotary axes consists of, for example, axes that are arranged sequentially relative to each other, i.e. with the stationary element of an axis being fixed to the moving element of the adjacent axis. An industrial machine having more axes works, by means of a work tool, a piece that can be fixed to the moving element of one of the axes or to the stationary element of one of the axes or on a stationary part of the machine. Similarly, the tool can be fixed to the moving element of one of the axes or to the stationary element of one of the axes or to a part of the machine, either stationary or moving. The control units of the individual axes can be either comprised or replaced by an individual control unit of the machine.

A prior art industrial machine, as shown in Fig. 3 and 4 and designated with numeral 100, typically consists of a base 1, acting as the stationary element of a linear axis, and a worktable 2 acting as the moving element of the linear axis, sliding on said base along a moving axis X (depicted in the figures with a dotted line) with a workpiece 4 made of solid material being fixed thereto. The industrial machine 100 is also provided with a mechanical work tool 5 (shown in Fig. 3) for machining the piece 4 of material. The movement of the moving worktable 2 relative to the base 1 is ensured by a conventional electric motor (not shown in the figures) which is conveniently mounted to the worktable or base, and by suitable means for the mechanical transmission of the relative motion between the worktable and base.

In order to measure the displacements of the moving worktable 2 relative to the base 1, upon operation of the industrial machine, the industrial machine 100 is equipped with a linear encoder 6 consisting of a reading head 7, integral with the worktable 2, such as to be sliding, without mechanical contact, relative to an optical line 8 integral with the base 1. The optical line 8 is arranged in a suitable space formed on the side of the base (stationary element of the linear axis) and results parallel to the moving axis X of the industrial machine .

The linear encoder 6 allows the industrial machine 100 to provide an operator, or control unit, with a measure representing the displacement of the moving table along the axis of movement of the industrial machine.

The prior art industrial machine 100 has the drawbacks that the quality and precision of the measure as provided by the linear encoder 6 critically depend on the geometry of the base on which the optical line is mounted. As the latter is, in fact, firmly anchored to the moving axis of the machine, it is affected by the deformation to which the base 1 is subjected upon operation. Any deformation of the optical line 8 affects the reliability of the measures being provided by the linear encoder and also the proper operation of the latter.

Another disadvantage of the industrial machine 100 as described above is the {sometimes considerable) distance between the linear encoder 6, the position of which depends on the position of the optical line 8 along the base 1, and the area of greatest interest for the measuring, usually the point in the axis of movement where the workpiece is fixed. In fact, the need is felt of being aware of, upon operation of the machine (and thus while the workpiece is being machined) , any geometric deformation of the machine which change the relative position between the mechanic parts composing the industrial machine and the piece, such as the position between the base (stationary element of the linear axis) and the moving worktable (moving element of the linear axis) in order to correct any undesired displacements between tool and piece that, though minimum, may compromise the quality of piece machining, mainly when high-precision operations are contemplated. The object of the present invention is to provide an industrial machine that overcomes the drawbacks and has a more reliable operation than the prior-art industrial machine mentioned above.

The object of the present invention is achieved by means of an industrial machine such as defined and characterized in claim 1.

Preferred embodiments of said industrial machine are as defined by the annexed dependent claims 2 to 31.

The invention will be better understood from the following detailed description of an embodiment thereof, which is given by way of non-limiting example with reference to the annexed figures, in which:

Fig. 1 schematically shows a perspective view of a first prior-art industrial machine; Fig. 2 schematically shows a perspective view of a portion of a second prior-art industrial machine;

Fig. 3 schematically shows a perspective view of a third prior-art industrial machine;

Fig. 4 shows a side view of the third prior-art industrial machine in Fig. 3 ;

Fig. 5 schematically shows a perspective view of an industrial machine according to an example of the invention;

Fig. 6 schematically shows an optoelectronic measuring device to be used with the industrial machine in Fig. 5;

Fig. 7 schematically shows a side view of the industrial machine in Fig. 3 in which a protection shield against electromagnetic radiation that can be generated by the optoelectronic measuring means in Fig. 6; and

Fig. 8 schematically shows a variant embodiment of the protection shield as shown in Fig. 7.

It should be noted that, throughout the figures, equal or similar elements will be designated with the same numerals.

An example of industrial machine generally designated with numeral 200 is now described with reference to Fig. 5 and 6.

As used herein, it is understood that by "operation" of an industrial machine is further meant any function that the machine can carry out, among which, for example, moving a tool within the operating area, holding the tool in any position, machining a workpiece and also adjustment, measuring or monitoring operations that can be carried out not only on the workpiece, but also on other mechanical or structural parts belonging to the industrial machine. By "machining" is further meant each of those operations that an industrial machine can carry out on a piece, such as removal of materials, bending, polishing and the like, as well as surface treatment on the piece, such as varnishing.

The industrial machine 200, for example a milling machine comprises a base 1 or fixed element of a linear axis (only referred to the "base") and a moving structural element 2 on which a workpiece 4 is mechanically connectable using suitable fixing means such as adjustable jaws (not shown in the figure) .

It should be noted that, in other embodiments of the industrial machine 200, the piece 4 can be either mechanically directly connectable to the base 1 or be physically placed outside the industrial machine 200.

The industrial machine 200 further comprises a mechanical tool 50 for machining the piece 4, for example a mill mounted to a chuck, the latter being preferably connected to the base 1 in a mechanical manner. In other embodiments of the industrial machine 200, the mechanical tool 50 can be integral with the moving structural element 2; in other cases, it can be external to industrial machine 200 though however coordinated to and cooperating with the latter for machining the piece. Other types of tools to be used as machining means alternative to that described above are, for example a grinder, a borer, a welding gun, or a laser head, or a varnishing head and however depend, more generally, on the type of industrial machine being used. It should be further observed that the type of workpiece 4 also depends on the type of industrial machine and machining desired. In the case of a stock removing machine tool, the piece is reasonably made of solid material, typically metal, wood or plastics.

Referring back to the description of the industrial machine 200 in Fig. 5, the structural element 2 results to be slidingly coupled to the base 1 according to an axis of movement X (in the example, longitudinal to the base 1) of the industrial machine. To this purpose, the moving structural element 2 is preferably provided with suitable grooves 9 facing the base 1 to be snugly engaged within respective ribs 10 that are formed on the base. The sliding coupling described above allows the moving structural element 2 to be capable of adopting, relative to base 1, different positions representing corresponding operating configurations of the industrial machine 200.

It should be further considered that, in the case where the mechanical machining tool 50 results to be operatively coupled to the base 1, the sliding coupling described above allows a plurality of mutual positions between the machining mechanical tool 50 (or generally other machining means) and the workpiece 4.

Typically, the movement of the moving element 2 relative to the stationary element 1 is ensured by a conventional rotary electric motor fixed to the moving structural element 2 (not shown in the figures) and respective mechanical transmission elements (also not shown in the figures) of the relative motion between the moving structural element 2 and base 1. Alternatively, the rotary electric motor can be fixed to the base 1. Furthermore, in place of said rotary electric motor other moving means can be provided for the moving structural element 2, among which, for example, a linear electric motor, a pneumatic actuation system or a piezoelectric actuation system.

The industrial machine 200 further comprises an optoelectronic measuring device 11 that is arranged, for example, on the base 1 proximate to one of the two ribs 10 and a measuring reflecting target 12, referred to simply as the "target" herein below, which is mounted for example to the moving structural element 2 such as to be capable of being optically coupled to the optoelectronic device 11. It should be noted that by "reflecting target" is meant more generally, as will be described below, a target either reflecting or diffusing a respective electromagnetic radiation.

Preferably, the target 12 of the optoelectronic measuring device can be fixed to the moving structural element 2 by means of a suitable anchoring system, such as of magnetic type, which comprises one or more magnets. In greater detail, and with particular reference to Fig. 6, the optoelectronic device 11 comprises a laser self-mixing interferometer 20, for example a single-mode semiconductor diode laser Hitachi model HL8325G, known per se, which is suitable for emitting from a respective input/output port (not shown in the figure) a direct electromagnetic radiation to the target 12 and suitable for receiving, again on said port, a suitable fraction of the electromagnetic radiation reflected by the target . The laser self-mixing interferometer 20 further defines an interference cavity between the direct electromagnetic radiation and the reflected electromagnetic radiation. The direct electromagnetic radiation and reflected electromagnetic radiation preferably have a propagation direction parallel to the axis of movement X of the moving structural element 2 relative to base 1.

It should be further noted that, in order to improve the conveyance of the direct electromagnetic radiation to the target 12 and reflected electromagnetic radiation from the target 12 to the interferometer 20, thus accordingly improving the quality of the measuring by means of laser self-mixing interferometry, the optoelectronic measuring device 11 can advantageously provide one or more optoelectronic components, such as for example optical lenses, attenuators or amplifiers (not shown in the figures) to be interposed, for example, between the input/output port of the interferometer and the target. From an operating point of view, a laser self-mixing interferometer is based on a laser self-mixing effect, known per se, which occurs when the reflected electromagnetic radiation from a moving target, when it represents a fraction of the direct electromagnetic radiation, when it coherently re-enters the interference cavity and interacting therein with the direct electromagnetic radiation, causes the modification of several parameters of the direct electromagnetic radiation, such as, by way of example, laser-emission threshold, laser emission power, wavelength, spectral width. Advantageously, the laser emission power can be monitored in order to extrapolate an information representing the distance between the interferometer and moving target. After a phenomenon of interference similar to that described above, the laser self-mixing interferometer 20 is suitable to output an optical interference signal SO. By processing the latter, as will be described below, it is possible to trace back the measure of a distance d between a first reference axis al and a second reference axis a2 that can be defined in the industrial machine 200.

In greater detail, and according to the example described herein, the first reference axis al results to be stationary and associated with the laser self-mixing interferometer 20, while the second reference axis a2 is associated with the target 12 and thus, generally, to the moving structural element 2.

As illustrated in Fig. 5, the first al and second a2 reference axes (drawn with dotted lines) are parallel to each other and both orthogonal to the axis of movement X. Considering that the defined (direct and reflected) electromagnetic radiations have, as stated above, propagation direction parallel to the axis of movement X, the distance d is also measured in the same direction.

In an embodiment alternative to that described herein, the interferometer 20 can be mounted to the moving structural element 2, and vice versa, the target 12 can be fixed to the base 1. In this case, the first reference axis al results to be stationary and associable with the target 12 whereas the second reference axis a2 corresponds to the laser interferometer 20.

As shown in Fig. 6, the optoelectronic device 11 further comprises a photodetector 21, of a known type, such as a photodiode, suitable for receiving the input optical interference signal SO supplied by the interferometer 20 to convert the same to a corresponding output first electric signal SEl. It should be noted that the photodiode may also be integrated in the envelope of the interferometer 20 (laser diode) .

The optoelectronic device 11 further comprises a processing unit UP suitable for receiving in input and processing the first electric signal SEl supplied by the photodetector 21 and outputting a second electric signal SE2 representing said measured distance d. It should be noted that the processing unit UP is provided with at least one microprocessor and a respective memory for loading software and hardware modules (for example, a printed electric circuit on a circuit board) that can be associated with the microprocessor, for processing the first electric signal SEl.

The optoelectronic device 11 is suitable to supply a second electric signal SE2 to a control unit UC (schematically shown in Fig. 3) , which is operatively associated with the industrial machine 200, which is, after the second electric signal SE2 has been processed and a corresponding numeric data has been generated, suitable for commanding, as a function of said numeric data, the electric motor of the industrial machine 200 in order to move the moving structural element 2 relative to base 1.

Alternatively, the optoelectronic device 11 can be suitable for directly providing an operator with the second electric signal SE2 proportional to the displacement d being measured.

The control unit UC is also provided with hardware (typically a microprocessor and a respective memory) and software of its own for controlling and managing the industrial machine 200 based on the distance d being measured.

By way of example, the control unit UC, by means of the microprocessor thereof can carry out, while the piece 4 is being machined by the industrial machine, a comparison operation of the value of the measured distance d and a preset value that has been previously stored within said memory. When the measured distance d differs from the preset value (except for tolerances that may be admitted) , the control unit UC is capable of controlling the electric motor to move the moving structural element 2 thus restoring the distance between interferometer 20 and target 12 equal to the preset value .

The type of control as described above results to be very advantageous, in that, with reference to the exemplary industrial machine in Fig. 5 for machining the piece 4, the accidental displacement of the structural element 2 along the ribs 10 relative to the base 1, with consequent variation in the distance between the target 12 and interferometer 20, can affect both the quality of machining on the piece 4, and the performance of the industrial machine 200 and/or tool 50 being used. Advantageously, the control unit UC performs, upon machining the piece 4, a monitoring of the distance between interferometer 20 and target 12 such that it matches a preset value corresponding to a proper use and operation of the industrial machine 200.

With reference now to a further preferred embodiment as shown in Fig. 7, the industrial machine 200 can be provided with a structure having a variable length 60 to protect the input/output port of the laser interferometer 20 and target 12.

Particularly, it should be noted that the protection structure 60 is such as to be extended from the input/output port of the interferometer to the target such as to define an inner region within which the direct electromagnetic radiation and the reflected electromagnetic radiation can be propagated.

Furthermore, the protection structure 60 includes, for example, a plurality of tubular elements that are telescopically coupled to each other such as to be extended and contracted along the axis of movement X as the position of the moving structural element 2 changes relative to the base 1. To the purpose, it should be observed that the protection structure 60 advantageously has a first end connected to the optoelectronic measuring device 11, at the input/output port, and a second end connected to the moving structural element 2 , flush with target 12. It should be noted that the section of the plurality of tubular elements can be of any shape, being preferably circular.

It should be further observed that both connections cited above are preferably obtained by interposing suitable gaskets or other sealing means, between the first end and the optoelectronic device 11 and between the second end and the moving structural element 2, respectively.

The protecting structure 60 described above has the advantage of protecting the electromagnetic radiation, input/output port of the interferometer 20 and target 12 against impurities that may be found in the work environment, such as dirt, process waste (for example, dust, chips, splits) , industrial fluids (for example, oils, varnishes) or the like, which can cause undesired alterations and/or interruptions to the electromagnetic radiation thus affecting the operation of the optoelectronic measuring device 11. Advantageously, the industrial machine 200 in Fig. 7 accordingly allows the optoelectronic measuring device to operate free from errors that can be generated by the environmental conditions in which the industrial machine 200 is operated.

With reference now to Fig. 8, the industrial machine 200 can comprise, alternatively to the plurality of tubular elements, a protection structure with a variable length, also designated with numeral 60, of a bellow type, which is suitable for carrying out the same protective function and suitable for extending and contracting along the axis of movement X of the industrial machine following the variation in the relative position between the moving structural element 2 and the base 1. Furthermore, it should be noted that the bellow structure in Fig. 8 results to be connected to the optoelectronic device 11 and moving structural element 2 in an entirely analogous manner to the protection structure 60 in Fig. 7.

Advantageously, a plurality of sensors can be arranged within the protection structure 60 in Fig. 7 and 8, which are arranged chained to each other, and that are suitable for detecting, for example, physical parameters that can be found within the electromagnetic radiation propagation region, such as temperature, pressure, humidity. Monitoring these parameters is particularly advantageous as it allows keeping under observance, either continuously and/or discretely, the environmental conditions in which the (both direct and reflected) electromagnetic radiation is propagated, such as to be capable of correcting the measure of fluctuations induced by gradients, if required.

Generally, the industrial machine 200 can comprise, alternatively to the structure with tubular elements (Fig. 7) and bellow structure (Fig. 8) , any structure similar to those described above, and suitable to carry out the same protective function by extending and contracting as the position of the moving structural element is changed relative to the base, and vice versa.

It should be further considered that the protection structure 60 may not be provided in the alternative case where the industrial machine 200 integrates the optoelectronic measuring device 11 along with the target 12 directly within the base 1, for example by conveniently using hollow parts of the latter, which are arranged along the axis of movement X of the machine. In this case, the electromagnetic radiation, input/output port of the interferometer 20 and target 12 are advantageously protected by the inner space of the industrial machine 200, and the aid of a suitable protection structure is reasonably unnecessary.

Furthermore, in this configuration, the optoelectronic measuring device Il and target 12, while they are positioned along the base 1 (stationary element on the linear axis) similarly to the optical line on prior art industrial machines, has the economical advantage of maintaining a low cost regardless of the displacement measurement range d, unlike the optical line or any other graduated scale, which has an increasing cost as the value d increases.

In a further embodiment not shown in the figures, the industrial machine 200 can comprise further optical measuring devices that are entirely analogous to the optical measuring device 11, which are also arranged optically coupled with the target 12, suitable for measuring any angular displacement of the moving structural element 2 relative to base 1. Each of the measurable angular displacements is indicative of the rotation of target 12 about a first and second axes of rotation that are orthogonal to each other and both perpendicular to the electromagnetic radiation propagation direction emitted from the optical measuring devices and reflected/diffused by the target. In a further embodiment not shown in the figures, after the target 12 results to be firmly fixed to the moving structural element 2 (the wall of the moving structural element 2 may also act as a reflecting/diffusing target, if suitably treated) , the self-mixing laser interferometer 20 can be advantageously aligned with a so-called fine adjustment system to be then definitely locked by means of a fixing device for adjusting screws. This solution, besides being very compact, also ensures an advantage in terms of rapidity and precision during the calibration of the industrial machine 200, setup flexibility, protection and resistance to mechanical stress during the machining of the piece 4, and essentially, long-term reliability.

Also, the industrial machine 200 can be provided with further measuring means, also of optoelectronic type, such as, for example, one or more linear, angular or resolver encoders, which are entirely analogous to those described above with reference to the prior art . These means are suitable for measuring distances between further reference axes, which can be associated with respective structural parts of the industrial machine, in which the measured values can be integrated with the distance d being measured via the laser self-mixing interferometer . In an alternative embodiment to those described above, the industrial machine 200 has the optoelectronic measuring device 11 being placed on the side of base 1 and the target 12 being integral with the moving structural element 2 such as to result optically coupled with the measuring device 11 for measuring the relative displacement between the moving element 12 and base 1 along the axis of movement X (linear axis) . This particular configuration, which is structurally very similar to prior art linear encoders, is cost-effective and results to be quite simple to assemble by an operator; it also allows measuring any deformation between the base 1 and moving structural element 2 that a linear encoder cannot detect.

In addition, it should be noted that in a further embodiment (not shown in the figures) , the industrial machine 200 can be provided, for example, with measuring means, alternatively or in combination with the machining tool 50, such as a measuring probe, known per se.

It is understood that only some exemplary embodiments of the industrial machine according to the invention have been described so far. Furthermore, it should be considered that the industrial machine as described above can also be considered as being only a part of a more complex industrial machine. An example of operation of the industrial machine 200 during the machining of piece 4 is now described with further reference to Fig. 5.

Particularly, the case will be considered in which the machining provides that a hole is made in the piece 4, which preferably has orthogonal direction to the axis of movement X, using the mechanical tool 50, for example a drill being mechanically connected to the industrial machine 200.

During a preliminary machining step, the piece 4 is fixed to, by means of the suitable claws, the moving structural element 2. While the machine is being switched on, the optoelectronic measuring device 11 is operated. Next, an operator of the machine operates the electric motor to move, relative to base 1, the moving structural element 2 in order to cause the industrial machine to adopt a first operating configuration for carrying out said hole within the piece 4 in a determined location selected during the design step. If required, in order to facilitate achieving the first operating configuration of the machine, the operator can also adjust the mechanical tool 50 such as to align or approach the latter to the piece 4.

When the first operating configuration described above has been achieved, the optoelectronic measuring device 11 provides a first preset value of distance d between the laser interferometer 20 and target 12 corresponding to said first operating configuration. This first preset value is then stored within the memory of control unit UC or, alternatively, can be selected from a series of values that have been previously stored within the same memory of the unit UC.

From an operating point of view, the industrial machine 200 starts, upon command by the operator, machining the piece 4 and, simultaneously, the optoelectronic device 11 and control unit UC become activated for monitoring that the distance d between the 20 and target 12 is maintained equal to the first preset value. In the example as described herein, in fact, it appears important that, during the machining, in order to facilitate making the hole in an orthogonal direction relative to the axis of movement X, the distance d is left unchanged as much as possible.

In greater detail, in order to carry out said monitoring, the laser self-mixing interferometer 20, during the machining of the piece 4, emits from the input/output port, a direct electromagnetic radiation to target 12. When the target 12 receives the direct electromagnetic radiation, it reflects/diffuses, in turn, this electromagnetic radiation to the input/output port of the interferometer 20. The latter, by entering coherently the laser cavity of the interferometer 20, due to the interferometer effect described above, allows the latter to generate an optical signal SO that is representative of the distance d between the target 12 and interferometer 20.

Subsequently, a photodetector 21 detects the optical signal SO and converts it to a corresponding first electric signal SEl that is, in turn, sent to the input of a processing unit UP. The latter provides to process the first electric signal SEl to generate a second electric signal SE2 also indicative of the distance d measured between the laser interferometer 20 and target 12.

Thereafter, the control unit UC with which the industrial machine is provided receives said second electric signal SE2 and converts it, via the microprocessor thereof, to a corresponding numeric data. The control unit UC then compares said numeric data with the first preset value stored within the respective memory.

When the numeric data results to be different from the first preset value, the control unit UC automatically provides to operate the electric motor in order to move, relative to the base 1, the moving structural element 2, and thus also the piece 4, such that the industrial machine 200 goes back, from a second operating configuration adopted during the machining, to the first operating configuration as designed and set by the operator for the proper execution of the hole in the piece 4.

On the contrary, when the numerical data coincides with the first preset value, the control unit UC does not send any command to the electric motor as the measured distance d is still equal to the first preset value and thus the machining is proceeding in a proper manner since the industrial machine 200 is maintaining the first operating configuration.

The structural and functional description discussed above, with reference to the industrial machine 200, allows those skilled in the art to apply the teachings of the invention to any other type of industrial machines on the basis of simple knowledge of the field.

While reference has been made to the laser self- mixing interferometer, the teachings of the present invention are also valid when another type of interferometer is used in place of the laser self-mixing interferometer, such as Michelson laser interferometer, known per se, which is suitable for optically cooperating with target 12. Michelson laser interferometer comprises a laser source, such as a Helium-Neon frequency-stabilized source, for generating a direct electromagnetic radiation to a moving target. Furthermore, Michelson interferometers comprise, for example, a stationary retroreflector and a beam splitter such as division e recombination (interference) means of direct electromagnetic radiation and corresponding electromagnetic radiation reflected and/or diffused by the moving target in order to assess the displacement, if any, of the target relative to the source. Michelson laser interferometer is operatively associated with the photodetector and qontrol unit of which the operation has been described above with reference to the laser self-mixing interferometer 20. Alternatively to the laser self-mixing interferometer 20 or Michelson laser interferometer, a Doppler laser interferometer can be also used, which is suitable for optically co-operating with target 12.

For example, this interferometer comprises a helium- neon laser for emitting the direct electromagnetic radiation, a beam modulator/splitter and a combiner in which the interference occurs between the reflected electromagnetic radiation from the target and a reference electromagnetic radiation that is obtained, by the modulator/splitter, from the direct electromagnetic radiation. An example of Doppler laser interferometer is described in US-A-4715706.

As may be observed, the object of the invention is fully achieved in that the industrial machine described herein comprises a laser interferometer suitable for ensuring a measuring that is not affected by the geometric deformations of the axis with which it is associated, unlike what occurs, for example, in those industrial machines that are provided with a linear encoder and optical line.

It should be noted that, advantageously, the measure of the distance between laser interferometer and target is not sensitive to local structural deformations and, at the same time, ensures monitoring the displacement dynamic of only the target, rigidly integral with the moving axis, which is, in turn, given by the composition of the displacement being set and that being induced by the geometric alterations.

Furthermore, the configuration of the industrial machine which provides the optoelectronic measuring system to be integrally fixed to the base 1, by means of a suitable anchoring system of magnetic type is different from the prior art industrial machine which integrates the linear encoder due to its great measuring flexibility at low costs, regardless of the distance between interferometer and target.

The solution comprising the use of a laser self- mixing interferometer is particularly advantageous as it is cost-effective and easy to install, which ensures a good effectiveness and measuring precision due to the small number of optical components with which it is provided .

Another advantage deriving from the use of a laser interferometer as compared with, for example, a prior art linear encoder as mentioned above is the versatility in selecting the configuration thereof that can be suitably adapted to the geometry of an industrial machine.

The optoelectronic device using a laser interferometer further offers a greater freedom on selecting the positioning of the target according to which the measuring is carried out. For this reason, the

(either reflecting or diffusing) target can be thought to be positioned as close as possible to the workpiece.

This possibility entails major advantages, as it minimizes the measuring error induced by the geometric deformations occurring between the point of interest

(workpiece) and the point of measure (reflecting target) .

It should be noted that, still advantageously, the laser interferometer can be used not only during the machining of the workpiece, but also, as stated above, during the general operation of the machine, and also for calibrating the industrial machine to which the interferometer results to be fixed, or more generally, associated. Furthermore, advantageously, and still more particularly, the laser self-mixing interferometer allows the module and displacement direction of a target to be immediately acknowledged via an individual interferometry channel . Another advantage is that the optoelectronic components required for laser self-mixing interferometry currently on the market, such as the semiconductor diode, are available off the shelf at a very low cost and exhibit a proved operative reliability and duration over time. Particularly, besides having a low cost, these devices have such compactness and robustness that the self-mixing interferometer results to be ideal in a typically industrial work environment.

Furthermore, it should be considered that Michelson and Doppler laser interferometers are also available on the market and can offer good performance and proved reliability even in those applications for which they can be intended within the scope of the present invention.

Claims

1. An industrial machine (200) comprising: a moving structural element (2) for adopting different positions in corresponding operating configurations of the machine (200) ; optoelectronic measuring means (11, 12) of a distance (d) between a first reference axis (al) and a second reference axis (a2) associated to said structural element (2) ; characterized in that said optoelectronic measuring means (11, 12) comprise a laser interferometer (20) and a measuring reflecting target (12) that are optically coupled to each other and each being associated with one of said reference axes, said laser interferometer including a laser source for emitting a direct electromagnetic radiation to said target (12) and interference means between a reflected electromagnetic radiation from said target and a reference electromagnetic radiation obtained from the direct electromagnetic radiation.

2. The industrial machine (200) according to claim 1, further comprising a control unit (UC) for generating command signals for said moving structural element (2) as a function of said measured distance (d) and based on which the machine (200) can adopt the operating configurations .

3. The industrial machine (200) according to claim

2, further comprising means (50) for machining and/or measuring a piece (4) ; said moving structural element (2) allowing a plurality of mutual positions between said machining and/or measuring means (50) and said piece (4) .

4. The industrial machine (200) according to claim

3, wherein the piece (4) is mechanically connected to said moving structural element (2) such as to be moved while it is being machined.

5. The industrial machine (200) according to claim 3, wherein said machining and/or measuring means (50) are mechanically connected to the moving structural element

(2) .

6. The industrial machine (200) according to claim

1, wherein said measuring target (12) is mounted to said moving structural element (2) and said interferometer

(20) results to be stationary and associated with said first reference axis (al) .

7. The industrial machine (200) according to claim

1, wherein said interferometer (20) is mounted to said moving structural element (2) and said measuring target

(12) results to be stationary and associated with said first reference axis (al) .

8. The industrial machine (200) according to claim 1, further comprising a support base (1) for the moving structural element (2) , said moving structural element (2) resulting slidingly coupled to said base (1) according to an axis of movement (X) of the industrial machine (200) .

9. The industrial machine (200) according to claim 8, wherein said laser interferometer (20) is fixed to said base (1) .

10. The industrial machine (200) according to claim 1, wherein the optoelectronic measuring means (11, 12) further comprise a photodetector (21) suitable for receiving an interference optical signal (SO) supplied by- said laser interferometer (20) and suitable for converting it into a corresponding first electric signal (SEl) .

11. The industrial machine (200) according to claim 10, wherein the optoelectronic measuring means (11, 12) further comprise a processing unit (UP) suitable to receive and process said first electric signal (SEl) to provide a second electric signal (SE2) representing said measured distance (d) .

12. The industrial machine (200) according to claim 11, wherein said control unit (UC) is suitable for receiving said second electric signal (SE2) to control moving means for said moving structural element (2) .

13. The industrial machine (200) according to claim 12 , wherein said moving means comprise a motor that is mechanically connected to said moving structural element (2) .

14. The industrial machine (200) according to claim

2 and 11, wherein said control unit (UC) is suitable for receiving said second electric signal (SE2) to control said machining and/or measuring means (50) for said piece

(4) .

15. The industrial machine (200) according to claim 1, further comprising a structure having a variable length (60) for protecting an output port of said interferometer (20) and said measuring target (12) , said structure (60) having an end connected to the moving structural element (2) and extending from said output port to said measuring target (12) defining an inner region within which the electromagnetic radiation can be propagated.

16. The industrial machine (200) according to claim 15, wherein said protecting structure (60) comprises a plurality of tubular elements that are telescopically coupled to each other.

17. The industrial machine (200) according to claim 15, wherein said protecting structure (60) is of a bellow type .

18. The industrial machine (200) according to claim 3, wherein said machining and/or measuring means (50) comprise a mechanical tool for machining said piece (4) .

19. The industrial machine (200) according to claim 3, wherein the machining and/or measuring means (50) comprise a measuring probe.

20. The industrial machine (200) according to claim 18 and 19, wherein the machining and/or measuring means (50) comprise said machining tool and said a measuring probe.

21. The industrial machine (200) according to claim 10, wherein said photodetector (21) is a photodiode.

22. The industrial machine (200) according to at least one of the preceding claims, wherein said laser interferometer (20) comprises a semiconductor laser diode or a Helium-Neon laser.

23. The industrial machine (200) according to at least any of the preceding claims, wherein said laser interferometer (20) is a laser self-mixing interferometer.

24. The industrial machine (200) according to claim 23, wherein said source of the laser self-mixing interferometer (20) is such as to define an interference cavity between said direct electromagnetic radiation and the reflected electromagnetic radiation from the target ( 12 ) .

25. The industrial machine (200) according to claims 8 and 24, wherein said direct electromagnetic radiation has a propagation direction parallel to said axis of movement (X) .

26. The industrial machine (200) according to at least one of the preceding claims 1 to 22, wherein said laser interferometer (20) is a Michelson laser interferometer or Doppler laser interferometer.

27. The industrial machine (200) according to claim 1, wherein said optoelectronic measuring means (11, 12) further comprise at least one second laser interferometer, said at least one second laser interferometer being optically coupled to said measuring target .

28. The industrial machine (200) according to at least one of the preceding claims, further comprising further means for measuring distances between further reference axes that can be associated with respective structural parts of the industrial machine, wherein said measured distances can be integrated with the distance (d) measured by means of the laser interferometer.

29. The industrial machine (200) according to claim 28, wherein said further measuring means are in the group comprising: angular encoder, resolver, linear encoder.

30. The industrial machine (200) according to claim 1, wherein the laser interferometer (20) can be used for calibrating the industrial machine (200) .

31. The industrial machine (200) according to at least any of the preceding claims, wherein said industrial machine is in the group comprising: machine tool, laser cutting machine, coordinate measuring machine, pressure waterjet machine, moving or manipulating machine, assembly machine.