GB2461804A - Calibration Device for Starting Line Detector of Hand Held Machine Tool - Google Patents

Abstract

Device 33 and method for calibrating alignment mechanisms 50 of hand-held machine tools 2 having a calibration receptacle 49 with an adapter 36 to be inserted into a tool holder 18 on the machine tool with a marking line 35 corresponding to a starting line on a workpiece and having side guides for a base part 48 of the machine tool. Also claimed is a device made of one piece with side guides 38, the marking line 35 running centrally and lengthways and the adapter being stepped and pin shaped 37 and running lengthways and centrally and a method whereby workpiece features are simulated on a display. Replacable background patterns may be provided for the calibration plate to test automatic following of a starting line using contrast transitions (figures 4 and 5) in difficult seeing or contrast conditions e.g. graining, dirt etc. Lighting, white balance or gain may be adjusted to improve contrast between the starting line and the background. The tool may be a padsaw. The alignment mechanism may be a camera or other sensor and calibration may be automatic on connecting the device 33 to the tool 2.

Description

Description Title

Device for calibrating machine tools The invention concerns a device for calibrating machine tools, in particular hand-held machine toolS, according to the pre-characterizing clause of Claim 1.

Prior art

Machine tools of the above-mentioned kind are known in practice in the form of saws, which are provided with an auxiliary device which works without contact, to align its tool, in the form of a saw blade, onto a starting line, which is predetermined on the workpiece side, as the specified working path.

Such auxiliary devices work, for instance, with laser beam emitters, the laser line of which is aligned onto the starting line, to make guiding the machine tool along the starting line, in particular beginning to saw a workpiece on the starting line, easier for the user, since it is often difficult for the user to see the starting point for the tool on the workpiece. Auxiliary devices which are guided by sensors and work autonomously are also known.

A precondition for successful work using an auxiliary device is that the position of the latter relative to the machine tool, in particular to its tool, is aligned exactly, which in the case of modern machine tools can by no means be taken for granted despite appropriate tests during manufacture, in particular because of the numerous functions and adjustments which are integrated in them.

Also, wear and damage in working operation can cause changes, which can affect the positional precision and thus also the work result.

Disclosure of the invention

The invention is based primarily on the object of creating a device, which can be easily handled even by the amateur as user, for calibrating machine tools of the above-mentioned kind.

This is achieved with the features of Claim 1, according to which the calibration device provides a calibration receptacle for the base part of the machine tool. Using it, a workpiece, onto the starting line of which the auxiliary device must be aligned, is simulated. Because the base part of the machine tool is fixed in position relative to the calibration receptacle and the calibration receptacle has a marking line, like the starting line on the workpiece side, the alignment of the auxiliary device onto the starting line can easily be checked, and thus also the position of the tool relative to the starting line and the alignment of the base part of the machine tool onto its superstructure.

The calibration receptacle thus functionally forms a straightening plate, the edges of which preferably form side guides for the base part, so that in association with the engagement of an adapter element of the calibration receptacle into the tool holder, a connection which can hardly be affected by user error, and is secured in position and direction, is created between the calibration receptacle and the machine tool.

Since the adapter element and the marking line are also in the recessed area of the base plate, onto which the optical and/or sensory auxiliary device is aligned, for the machine tool the same relationships apply to the base plate and to the calibration receptacle, so that the calibration which takes place relative to the calibration receptacle exists in the same way relative to the base plate, and thus continues for the work process.

In the solution according to the invention, the auxiliary device for alignment onto the starting line which is predetermined on the workpiece side usefully includes a detection unit for checking the position of the starting line, and preferably also for checking the detectability of the starting line. The detection unit is usefully connected to actuators for adjusting and aligning the tool onto the starting line, so that at least in relation to the alignment of the tool onto the starting line, the calibration can be initiated automatically, if appropriate also by the user pressing a button, but does not have to be done by the user intervening in the machine.

Doing calibration of the machine tool in accordance with the invention is not associated with expensive devices, but can be achieved, without access to further devices, with a calibration receptacle which is preferably in the form of a plate with edge stops, which rise from the longitudinal sides, between which the marking line runs lengthways and centrally, and on which the adapter element, in particular in the shape of a pin, is arranged lengthways and centrally. This makes it possible to produce the calibration receptacle in one piece, from cheap materials, by simple production methods, and finally to form the calibration receptacle as a cardboard template.

The edge stops are preferably in the form of edges along the longitudinal sides of the calibration receptacle, so that even if the carrying capacity of the plate is small, the necessary stiffness and form retention results. In particular, a calibration receptacle of this form also forms an accessory to be provided when a machine tool is sold. This accessory enables the user to check a product, and if appropriate, in particular in the case of automated adjustability, to carry out and check the calibration independently.

In the case of the construction according to the invention of the device for calibrating the tool, the procedure for calibration is also so easy to control that errors are almost excluded.

The invention also concerns a method of operating machine tools which are equipped with a detection unit for checking the detectability and position of a starting line on the workpiece by sensors. In association with a calibration device of the type described above, the result is also the possibility of checking the detection unit, if the calibration device, in particular on the calibration receptacle side, in the observation area of the detection unit, contains not only a marking line corresponding to the starting line, but also detection patterns, which during calibration also make it possible to check functions related to this.

In the case of the considered method according to the invention for operating the machine tool, contrast transitions which are given in the observation area, in particular in the detection area, for the detection unit, in particular abrupt contrast transitions on reference lines, are detected as contrast points. Thus the width of the starting line can be detected through its contrast transitions to the environment in contrast points, which are at a distance from each other corresponding to the width of the starting line, which makes it possible to detect, with high precision, the mean value between contrast points opposite each other over the width of the starting line as the starting point for the tool, and thus to calibrate the machine tool in the described manner using this method.

In practice, it is specially important that for the method according to the invention a simplified approach is given for masking out contrast points which are inessential to detecting the contrast line, by the distance, corresponding to the width of the starting line, between two contrast points being used as the filter criterion for masking out contrast points outside the starting line. Consequently the surface structure in the detection area which the detection unit detects outside the starting line appears to be largely free of contrast transitions, resulting in an improvement of the contrast between the starting line and the background, especially as it is also part of the invention to set the decisive parameters for contrasting for maximum contrast between the starting line and the environment.

within the method, if it is detected that despite optimisation of the decisive parameters for contrasting, the necessary sharpness of the starting line for reliable guidance of the machine tool is unachievable, this function is inactive, and if appropriate the purely autonomous work flow is interrupted, and if necessary the machine tool is switched off.

This method too can be checked within the invention when the machine tool is calibrated, if on the calibration receptacle side, in the observation field of the detection unit, in particular in the detection area, an appropriate structure pattern is provided. If the procedure functions correctly, this structure pattern is detected as practically reduced to the starting line, and the result is thus the alignment onto the marking line which is provided on the calibration receptacle as a theoretical starting point for the working tool.

The method according to the invention is specially advantageous in association with operation of machine tools, in particular padsaws, where the tool, in the case of padsaws the saw blade, is aligned onto the starting line (e.g. zero point setting by reference line) by downstream computer, control and setting means, and by rotation around its longitudinal axis, depending on setting parameters which are acquired via the detection unit about the course of the starting line, said machine tools making possible an autonomous, in particular a semi-autonomous working operation, in which the machine tool is guided to follow the starting line via the tool, and in which the user oriiy has to support the machine tool.

It is also within the invention to show a mere simulation of a detection pattern such as a starting line -in particular, for instance, using LCD or CLED technology -on a display. This opens up the possibility of showing a wide variety of shapes and geometries, and logging and/or assessing them irmnediately for their effect on the system.

In particular, such a procedure opens up the possibility, e.g. when calibrating a saw, particularly a hand-held padsaw, of holding onto the saw during calibration, since -reversing the situation in the working process -moving pictures can be shown on the display.

Further advantages and useful versions can be taken from the further claims, the description of the figures and the drawings.

Fig. 1 shows a schematic representation of a hand-guided machine tool in the form of a padsaw in its working position on a workpiece, Fig. 2 shows, in schematic plan view, that area of the base plate which is crossed by the saw blade of the padsaw according to Fig. 1 and recessed, Fig. 3 shows a simplified, schematic representation of a padsaw, with a calibration receptacle, which is associated with its base plate, of a calibration device, Fig. 4 shows a plan view of a workpiece with a structured, e.g. grained, upper side, and with a starting line running on the upper side, contrast transitions in the surface given by the surface structure and by the starting line being detected as contrast points, Fig. 5 shows a similar representation to Fig. 4, contrast points which are irrelevant to the course and width of the starting line being masked out around it, and only the contrast transitions between the starting line and

the background being detected and shown

clarified by contrast points which are shown on the edge of the starting line, and Figs. 6 and 7 show, in block diagrams, the detection method according to the invention.

In Fig. 1, a machine tool 1 in the form of a padsaw 2 is shown. The padsaw 2 has a housing 3, and is carried on a base part 48 in the form of a base plate 4. The base plate 4 is connected via a swivelling axis 14, which runs in the direction of the longitudinal axis 12 of the padsaw 2, to the housing 3 and/or the units and parts which it surrounds, and supports the padsaw 2 movably against a workpiece 5 in working operation. As the working tool 7, the padsaw 2 has a saw blade 8.

6 designates the working direction which corresponds to the sawing direction during straight sawing, and corresponds to the extent direction of the longitudinal axis 12 of the padsaw 2, and in which the plane of the saw blade 8 also extends during straight sawing.

The saw blade 8 crosses the base plate 4 in the region of a recess 27, which in the working direction 6, upstream from the work area 9 of the saw blade 8, surrounds and delimits a detection area 10.

The housing 2 has, in its upper area opposite the base plate 4, a handle part 11, and at the front relative to the working direction 6, merges into a face wall area 13, which below runs into a re-entrant step 17. In the region below the step 17 is the tool holder 18, which connects the saw blade 8 to a lifting rod (not shown), via which the saw blade 8 is driven reciprocatingly in the direction of the arrow 19, and is adjustably guided around its axis of rotation 23 in the direction of the arrow 21.

In Fig. 1, an actuating drive 20, via which the saw blade 8 is to be driven reciprocatingly in the sawing direction as indicated by the arrow 24, is also shown, with swivelling support (not shown here) of the saw blade 8 and the associated lifting rod (not shown) around a swivelling axis which is transverse to the axis of rotation 23 and above the tool holder 18.

On the housing 3, below the handle part 11, a switching arrangement 15, via which the normal switching on and off of the machine is done, is provided. Also, at 16 in the side wall area of the housing 3, a switching device, via which the various operating modes which can be implemented with the described construction of the padsaw 2 can be set, is indicated.

The padsaw 2 is also preferably provided with a lighting arrangement 22, which makes it possible to light the work area 9 and preferably also the work area in front of it and on the workpiece side, said lighting arrangement being arranged in the transition 13 from the face area 13 into the step 17. In this area, preferably an auxiliary device 50, which works without contact and is used to align the padsaw 2 and/or its saw blade 8 onto a starting line 26, is also provided. The auxiliary device 50 also includes, in particular, the sensor 30, in the form of a camera, of a detection unit 28, which is connected to a signal processing unit 29, which accesses a computer unit 31 and a control unit 32, via which the various drives and/or actuators for the working tool 7 in the form of the saw blade 8 are controlled, taking account in particular of data which are detected via the detection unit 28.

In one of the possible operating modes of the padsaw 2, normal operation, the saw blade 8 is aligned in the direction of the longitudinal axis 12 of the padsaw 2 and driven reciprocatingly in the direction of the arrow 19.

Another operating mode is oscillating operation, in which an oscillating movement in the direction of the arrow 24 is overlaid over the reciprocating movement of the saw blade 8 in the direction of the arrow 19 via the actuating drive 20. In a further operating mode, the so-called scrolling mode, the padsaw 2 is aligned onto a specified work path, e.g. onto a starting line 26, by rotating the saw blade 8 around its axis of rotation 23. This can be done manually, but in particular depending on control outputs which are detected via the detection unit 28 following the starting line 26 and determined via the signal processing unit 29, so that the result is a semi-autonomous operating mode, in which the user only has to support the padsaw 2. :il

In Fig. 2, it is indicated that via the detection unit 28 or its sensor 30, which in particular is in the form of a camera, a detection area 10, through which the starting line 26 runs, is detected, a swivelling area 25 being drawn in corresponding to the in practice specially usable angle of rotation for the rotation of the saw blade 8 around the axis of rotation 23. Permitted angles of rotation for the saw blade 8 extend to about �30°, relative to the longitudinal axis 12.

The result of the multiplicity of adjustment possibilities both on the driving side and in the connection between the base plate 4 and the housing superstructure (of the padsaw 2) which is supported over it is that deviations from the setting positions which are predetermined by setpoint values occur, whether in production, because of wear in operation, or wrong handling of the padsaw with corresponding damage to it.

Here, to disclose a simple possibility for checking and also calibration, according to the invention -as shown in Fig. 3 -a calibration device 33 with a calibration receptacle 49 in the form of a calibration plate 34, relative to which the base plate 4 must be arranged in a fixed and oriented position, and aligned onto a marking, in particular a marking line 35, which is provided on the calibration plate 34, is provided. The marking line 35 corresponds, in relation to practical working operation, to a starting line, onto which the tool, in the case of a padsaw 2 its saw blade 8, is aligned, on the workpiece side. Corresponding to this alignment, the calibration plate 34 is provided with a rising adapter element 36 which is aligned with the marking line 35, is preferably in the form of a pin 37, in particular a stepped pin 37, and when the base plate 4 is placed on the calibration plate 34 engages into the tool holder 18, so that the result, in practical operation of the engagement position of the saw blade 8 relative to the workpiece 5, is corresponding positioning of the padsaw 2 against the calibration plate 34, that is, in the case of a calibrated padsaw, an equalised null position.

Thus, in association with the guidance on the longitudinal sides of the base plate 4 by the side guides 38, which are provided on the edges of the calibration plate 34 and in particular can be in the form of bent-up edge areas or box-shaped profiled edge areas, a rigid, simple calibration device 33 is created. With it, the machine tool 1, here the padsaw 2, in its most essential mechanical elements, namely the base plate 4 and the unit which is carried by the base plate 4 and surrounded by the housing 3, with the tool holder 18, can easily be checked for mutual positionally correct alignment and assignment, in particular even outside production, on the premises of the customer as user.

If the machine tool 1, in the embodiment the padsaw 2 according to Fig. 1, is additionally equipped with a detection unit 28, which is indicated schematically in Fig. 2 by the position of its sensor 30 among other things, when the padsaw 2 is positioned on the calibration plate 34 a position of the marking line 35 in the detection area 10 is given. If the median line of the detection area 10, which is covered by the longitudinal axis 12 of the padsaw 2 according to Fig. 2, coincides with the marking line 35, in the context of calibration the positionally correct alignment of the sensors, in particular the camera which is used as a sensor 30 for instance, is confirmed. A corresponding marking of the tool holder 18, showing symbolically the position of a tool which is placed in the holder, also makes it possible to check the signal chain from the receiving sensor 30, i.e. the camera, via the signal processing unit 29 to the corresponding actuator, so that the padsaw 2 can also be checked and adjusted, if necessary readjusted, with respect to the alignment of the working tool 7, i.e. the saw blade 8, the calibration being checked and carried out in principle, within the invention, purely by sensors, i.e. via software parameters, and mechanical intervention beyond this comes into question in practice only if there are corresponding mechanical faults.

Such continuous calibration is essential, in particular, in association with machine tools 1, above all padsaws 2, with which exact following of a starting line 26 is to be achieved even in difficult working and seeing conditions, and which therefore require not only that the working tool 7 should be exactly aligned onto its specified null position, but also that the starting line 26 should be followed on its median. This means that even in difficult seeing conditions, the contour of the starting line must be appropriately detected, to make alignment of the working tool 7 onto the thus determined median of the starting line 26 possible under signal processing by the detection unit 28.

To make this possible among other things, the invention concerns a method of operating machine tools, and a detection method, in which the edge boundaries of the starting line 26 are detected irrespective of difficult seeing and contrast conditions, so that the precondition of predetermining the line median by computer is created, as is explained on the basis of Figs. 4 and 5 and the block diagrams according to Figs. 6 and 7, which show a basic procedure in block diagrams.

Figs. 4 and 5 show the course of various sections of a starting line 39 on a background 40 and 41 respectively.

The background 40 according to Fig. 4 corresponds to an environment which interferes with the starting line 39, with graining, dirt, blurred contours and similar.

The result is a multiplicity of contrast transitions, which in the case of the recording technique assumed here, e.g. using a line sensor, are shown as contrast points 44 along a line 43. If there is sufficient contrast, the edges between the starting line 39 and the background are mapped onto the appropriate picture line 43 as contrast points, which are designated by 45 and 46.

Contrast points 45 and 46, which are assigned to a picture line 43 and opposite each other on the edge of the starting line 29, thus form a value pair, and for corresponding value pairs the contrast points 44, 45 along a starting line 39 are at an approximately equal distance from each other. Thus while retaining the course of the starting line 39, a mean distance for the contrast points 44, 45 along a starting line 39 can be determined, and thus also the picture median of the starting line 39, onto which the tool, i.e. the saw blade 8, is to be placed in its null position or in its required angular position.

To be able to detect the starting line 39 appropriately irrespective of the interfering structure of the background, it is advantageous to mask out those contrast points 44 which are not based on a corresponding contrast between the starting line 39 and the background, but are based on other kinds of irregularity. This can be achieved within the method according to the invention by using a line width, which is specified as required and in some cases also determined by the value pairs -contrast points 45, 46 -as a filter criterion. The representation of the measurements of the contrast points 44 in the environment of the starting line 39 is thus omitted, so that the result is a fictional background against which the starting line 39 stands out clearly. Additionally, other parameters which affect contrasting can be influenced, e.g. lighting, gain and white balance. For instance, if white balance is deactivated, bright graining can be cross-faded by very bright lighting, and thus made practically invisible for the camera as sensor 30.

If, despite the method, no starting line can be reliably worked out, so path detection does not achieve the aim, control functions based on path detection are usefully switched off, e.g., in the case of a semi-autonomously working system, the automatic, machine-side alignment of the tool 7 on a specified but not detected starting line 39.

Within the calibration according to the invention, the method according to the invention can also be checked, e.g. on the basis of at least one background pattern which is specified for the marking line 35 on the calibration plate 34, which finally permits sufficiently clear detection of the specified marking line 35 only if the marking line 35 has been worked out according to the method and thus made detectable for the system. Such a check can also be done separately, if appropriate on the basis of different patterns, which must be arranged replaceably on a calibration plate 34.

In a block diagram, Fig. 6 shows the method of working of the padsaw 2, which according to the invention is to be operated semi-autonomously, the following explanation with reference to this referring back to the explanations about Figs. 1 to 5, and 50 again designating an auxiliary device, which here comprises sensors 51 to detect data on the workpiece side, and data preparation 52. As explained for Fig. 1, as sensors 51 for instance a sensor 30 in the form of a camera can be provided, or a line sensor, as explained for Figs. 4 and 5. Data which the sensors 51 capture are processed in data preparation 52, in the form of a computer unit 31 with reference to Fig. 1, and then fed to a selection unit 53, in which, if useful or required, these data are subjected in a query and assessment part 54 to a plausibility check for their suitability for statements about the current purpose.

Here, in particular, this is the suitability for detecting the starting line 39 on the basis of specified query criteria, which are symbolised in Fig. 7 by question fields of a question section 56. Such query criteria are, in particular, for instance the distance between contrast points 45, 46 belonging to a value pair, and/or the position of contrast points 45, 46, corresponding to each other, of different value pairs, relative to each other, in such a way that they form a linear stroke on the edge side of the starting line 39. Taking account of these and other query criteria, in the assessment section 57, e.g. by means of fuzzy logic, from all the detected contrast points 44 a selection is made with respect to their suitability for defining the starting line 39. On the basis of a starting line 39 which is defined in this way, when other contrast points 44 are masked out, the contrast points 45, 46 which determine the starting line 39 form values which are fed via an output part 58, shown in Fig. 7, to a control and setting unit 59 with actuators 60 and a user-side operating unit 61. Via the actuators 60, the saw blade 8, which belongs to the padsaw 2 as a working tool 7, is set to the working direction corresponding to the starting line 39.

Via the operating unit 61, in a display 62, the operating instructions resulting from the work data are displayed for the user.

Additionally, in the operating unit 61 a switch arrangement 63 is provided, for input of the user's requirements, e.g. to switch the padsaw 2 on and off. Its signals require no assessment. The same applies, if appropriate, in relation to safety-relevant facts such as can be detected via the sensors 51 and for instance result from an intervention by the user into the working area 9. In such cases, the selection unit 53 merely forms a connecting link in a signal chain via which other parts and/or units of the padsaw 2, e.g. its drive motor, are to be addressed. In such cases, the query and assessment part 54 does not have to be passed through, and can be skipped, as shown in Fig. 7 by the bracket 64.