JPS6234589A - Apparatus for guiding flexible cloth in order to form three-dimensonal stitching - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention provides at least one receiving plate, a driving wheel for pressing down a fabric guided on the receiving plate, a control device for the driving wheel, and a control device for the driving wheel. a fabric edge position detector for guiding the fabric piece, said detector comprising at least one photodetector placed in front of the edge used for guiding the fabric piece; and an electronic circuit for converting the signal provided by the photodetector into a control 13 of the drive device.
The present invention relates to a device for guiding a flexible fabric to form a three-dimensional stitch.

[Conventional technology]

Sewing, in which flexible parts are made into three-dimensional shapes, is primarily found in the garment industry. In practice, the production of garments consists in sewing pieces of fabric that can be slightly deformed in order to create a surface that is intended to have fullness. Sewing of fabric is done by stitching, no matter what type of fabric it is made of. Two cases can be envisaged depending on whether the fabric pieces can be overlapped before stitching.

The first case is a conventional seam where the sewn part is flat when the sewing is finished. In the second case, it is necessary to guide the fabric pieces separately under the needle, so that once the stitching is finished, the sewn fabric pieces can no longer lie flat, and at least one As a piece of fabric, this stitching gives it a three-dimensional surface without any creases.
Examples of this can be seen in bras and cups.

Conventional sewing machines generally include a mechanism for creating thread or strand entanglement and a fabric advance mechanism. This feeding mechanism is formed by a claw having an elliptical movement and a presser metal fitting through which the fabric passes.

The longitudinal width of the claw movement determines the length of the suture stitch and is generally adjustable.

The pieces of fabric to be sewn are guided by edges that the seamstress can overlap as accurately as possible.

Normally, a sewing machine can only perform stitches in a straight line. In order to create a curved stitch, it is necessary to combine the rotational movement of the needle with the feed performed by the sewing machine's pawl.

Such trajectory corrections must be made simultaneously for each piece of fabric to be sewn.

Automatic sewing machines are known which allow stitching to occur at a predetermined distance from the curved edge of a piece of fabric.

This sewing machine has an actuator in contact with the guided piece of fabric, imparting a movement to the piece of fabric whose force has the effect of rotating the piece of fabric around the needle.

This actuator has been developed to the point where only pawl and wheel actuators are available due to ease of operation, but there are many shapes.

Wheel actuators of the known art are divided into two groups: those with a constant direction for the free wheel and those with a constant direction for the controlled wheel.

FR 2 241 648 describes a first group of actuators, the free wheels of which impart a rotational movement to the fabric piece at an angle to the direction of feed of the fabric piece, this movement following a guide. The second piece of fabric is also guided with the same device, with the curve of the guide corresponding to the position direction required for forming the three-dimensional seam, limited by the fabric edge stop.

[Problem that the invention seeks to solve]

This method has a number of drawbacks; its use is limited to fabrics that are sufficiently rigid to effectively guide the edges of the fabric, and the guide must be tailored to the style and size of the seam. It can be said that there is.

These drawbacks are not present in the control wheel actuator described above, for example in French Patent No. 2,518,134, which wheel has its axis of rotation parallel to the feeding direction of the dough and is capable of detecting the edge position of a piece of dough. It can be rotated in one direction or the other according to the information transmitted by the device. The guiding device also has means for adjusting the pressure of the wheels on the fabric, in order to ensure a contact pressure depending on, inter alia, the fabric, thickness and weave.

The position detector includes at least one photodetector arranged in front of one of the surfaces of the plate that is to separate the two pieces of fabric to be sewn by stitching, so as to enable positioning.

The photodetector includes two sets of light emitting diodes and a phototransistor. The reference position at which the edge of the fabric is checked is the point where the edge is centered between the two diodes. Therefore, at this reference position there is light emitted by the first diode and reflected by the separator, which is blocked by the fabric and then received by the corresponding phototransistor, while emitted by the second diode and reflected by the separator. The light reflected by the plate is received by the corresponding phototransistor. The same second photodetector is attached to the other side of the separator plate to detect the edge of the second piece of fabric.

The electrical signals provided by the photodetectors are sent to an electronic processor unit which compares the signals received at each fabric piece with reference values stored in a memory device and which acts as a motor drive circuit for the device guiding the fabric pieces. It will be done.

Rotational control of the wheels by position transducers is based on an all-or-nothing response, resulting in relatively large and short-amplitude trajectory corrections, but this produces wrinkles in the fabric during the change of direction, so small radius curves cannot be sutured.

A photodetector with a broad beam can be used to measure hidden surface gradients, subject to two conditions: the fabric has uniform transparency and the beam is perpendicular to the edge of the fabric. An analog signal corresponding to the edge position is provided, provided that it is uniformly distributed along the longitudinal section.

Analog equipment, which is just a logical system (all or nothing), is a race that varies greatly in density.

Unable to handle fabrics with irregular transparency such as net or printed fabrics.

The perforated fabric after cutting has no jagged edges,
In extreme cases, the threads of the net fray at intervals greater than its diameter. In the field of photodetectors, gaps inside the fabric make it impossible to measure hidden surface gradients using simple analog sensors. As the edge of the perforated fabric passes in front of the sensor, the exact position of the actual edge can be detected and an analog signal is provided which reproduces the variations of this actual edge when uncut. This variation is due to the displacement of the cutting line in front of the sensor and the presence of gaps in the fabric along this line. Therefore,
It is necessary to know how to distinguish between these two causes in order to reconstruct the cut line that must be sutured.

A feature of the invention is that the drive comprises a drive wheel oriented in a particular direction according to the required curvature, the speed of rotation is mechanically controlled by its position direction, and the edge position detector The object of the present invention is to provide a guide device that is capable of reconstructing cutting lines that must be sewn in parallel by detecting the actual edges of the material.

[Means and effects for solving the problem] FIGS. 1 and 3 show a sewing machine equipped with a guide device including a drive device M and an edge detector N.

The drive device is shown enlarged in FIG. 2, and is mounted on the sewing machine head and includes an actuation mechanism for the needle receiver shaft 2 that fixes the needle 3 at the end thereof, and a vertical movement mechanism for the presser foot 4. has been done.

The head also includes a mechanism (not shown) for transporting and guiding the thread to the needle.

In the known method, a table 5 (FIG. 3) carries a needle plate 6, which is provided with an opening for passing the feeding device formed by a pawl 7 and a hole for passing the needle 8. are doing. The pawls 7 move alternately, projecting teeth from the throat plate at the same time as they move forward towards the rear of the sewing machine (as viewed from the position of the sewing machine according to Figure 1), and the return of the pawls causes the teeth to protrude below the throat plate. Matches the teeth. The table also has a mechanism for making stitches by intertwining needle thread and bobbin thread.

Once the piece of fabric to be sewn by stitching is positioned, it is placed on a needle which is held down by the force of a presser metal fitting that allows the piece of fabric to rise.

The various movements of the mechanical parts of the sewing machine are designed to be synchronized so that the piece of fabric remains stationary as the needle moves through the piece of fabric to intertwine the thread.

When this operation is finished and the needle rises and leaves the fabric, the claw protrudes from the throat plate and presses the fabric against the presser foot, and the length of fabric corresponding to the length of one stitch is created between the presser foot and the throat plate. Push the dough backwards.

If a piece of fabric has to be guided to form a non-linear stitch, it is necessary to displace the piece of fabric around the needle with the needle as the center of rotation.

This guidance can only take place when the needle is in the low position while the upper and lower threads are intertwined.

〔Example〕

According to the illustrated embodiment, the drive device according to the invention comprises a spherical wheel 9 which is located in front of the throat plate and is in contact with one of the pieces of fabric to be guided. This wheel moves freely around a main axis IO which is parallel to the surface of the fabric and is fixed at one end to one arm 11 of a right-angle member 12, while the other arm 13 of the right-angle member is attached to a fixed frame 17. It is fixed to a shaft 14 that can rotate about the axis of fixed bearings 15 and 16. According to this embodiment, the shaft 14 and the wheel
It is perpendicular to the main shaft 10 of □, and the axis ' of the shaft 14 passes through the center of the spherical wheel.

The shaft 14 is equipped at its free end with an angular position measuring device 18, for example formed by a circular potentiometer, and with a rotational control device formed by a servomotor 19, which is controlled by an electronic edge detection device, which will be described below. It is carried out in The potentiometer and the stator of the servo motor are fixed to the fixed frame 17 by crossbars.

The wheel 9 is rotationally driven around its main axis 10 by a roller 21, the main axis 22 of the roller being in a plane containing the main axis 10 of the wheel, preferably in a horizontal plane perpendicular to the axis 14.

The rollers are in a fixed position relative to the frame 17 in which they are held by bearings.

According to the illustrated embodiment, this roller is a pulley 23
．． 24 and at least part of the belt 25 arrangement is rotationally driven by a mechanical transmission device. ko0) Ml solid is
Transmission device 2 connected to the drive point 27 of the main shaft of the sewing machine
6 directly or indirectly drives the assembly itself. The rotational speed imparted to the rollers is therefore coupled to the rotational speed of the sewing machine and is therefore determined by the speed at which the piece of fabric is fed by the stitching mechanism.

The roller 21 drives the spherical wheel 9 in a circle whose diameter depends on the direction of its position. Since propelling the piece of dough always takes place at the same point located on the outer circle of the wheel, the speed at this point varies inversely with the diameter of the circle over which the roller drives the wheel.

FIG. 4 makes it possible to understand the principle that the drive speed varies as a function of the position of the wheel in front of the roller, where the speed is considered constant.

A spherical wheel 9 is shown (in solid lines) in position WI, oriented such that its plane of symmetry coincides with that of the roller 21. Roller vector.

is applied to the wheel along an outer circle of radius R in order to yield a tangential velocity expressed as - times a factor of the constant velocity Vg of the roller (i.e. kVg=V0).

In the second position ■ (indicated by a dashed line), the vertical plane of symmetry of the wheel is rotated to the right, for example by an angle α.

The main axis of the wheel, which is perpendicular to the plane of symmetry, is also rotated at the same angle by drawing a circle with a radius R1 shorter than R (equal to Rcosα) in front of the roller 21. As a result, at the point of contact between the outer circle and the piece of dough, The tangential velocity will increase to V+=V./cosα.

■. can be regarded as a component force of velocity v1, and is selected to be equal to and in the same direction as the forward velocity of the claw for reasons explained later.

According to one variant of the embodiment, the synchronous mechanical drive for moving the spindle of the sewing machine is replaced by a servomotor 230 (indicated by a dashed line in FIG. 2), which generates a force component parallel to the direction of the movement of the pawl. is constant and the roller arrangement allows the wheels to provide a tangential velocity which propels the piece of fabric guided at a speed equal to the feed rate of the piece of fabric to be sewn.

To facilitate the position direction of each fabric piece before sewing,
The guide device includes a dividing device 28 formed by receiving plates 29, which are positioned above and below each other to determine the thickness of the fabric pieces 32, 33 to be sewn! 'It is contained between two supporting plates 30, 31 which are correspondingly remote from the receiving plate.

The support plate has an opening 34 through which the wheels of the device for propelling the piece of dough can pass, the wheels holding it down.

According to one embodiment in which the drive device is applied to a guide device of a sewing machine, each piece of fabric is guided and then sewn. Support plate 31
The piece of fabric 33 passing between the holder and the receiver 29 is guided in every respect by the device in the same way as the original piece of fabric, and this is illustrated by the cross-section of the wheel 35 drawn in dotted lines in FIG. and can be placed on the opposite side of the backing plate from the original piece of fabric.

The piece of fabric is guided in a known manner by its edges, at least one of which is cut along the desired sewing curve, which projects into the fabric and serves as a reference.

The guide device also includes an edge detector B formed from a proportional photodetector 36, described below, and having means for detecting edges.

The signal provided by the photodetector 36 is sent to an electronic device that detects this signal source and generates a signal that is sent to a comparator, one of the inputs of which is the wheel provided by the angular position measuring bag Y118. receives a reference signal that takes into account the position direction of the The resulting signal controls an automatic control system including a servo motor 19 which controls the position direction of the wheel 9 in front of the roller 21.

FIG. 5 shows the geometrical structure so that the operation of the guide device can be understood.

Straight lines "IsD and E respectively correspond to straight seams obtained by keeping constant the distance !!1. from the straight edge E of the fabric piece to the needle A.

This piece of fabric is propelled by a pawl in front of the needle with a velocity v0 whose magnitude and direction are represented by the vector v0 given at beam point A, as will be explained below.

Following the curve, the movement of rotating the fabric due to the feed provided by the claws overlaps. The fabric is regarded as a solid plane, with instantaneous centers of rotation o1, 0□, Ox1. There exists a velocity distribution that can be expressed by rotation around... This instantaneous center is located at the intersection of all perpendicular lines to the velocity vector at each point on the fabric. In particular, the perpendicular XX' to the velocity vector V0 imparted by the claw does not change whatever the curvature of the seam, since this velocity is strictly tangential to the seam. Therefore, the instantaneous center of rotation is always on this perpendicular line. This perpendicular line definitely seems to pass through the needle.

In order to define the required velocity distribution, a velocity is provided by the wheel 9 at a point B other than the needle A, which is defined in position direction and magnitude, for example, by the vector vI.

In order to eliminate wrinkles on the fabric surface between propulsion points A and 8,
It is necessary that the vector V, has a component force ve of the same magnitude as the vector V, given at point A. This component force ■o has the value 'J, c, osα=Vo. The angle α is the angle made by the diametrical plane of the wheel passing through the given point B, which is the angle between the horizontal axis of the wheel and the straight V
Ax
It is also an angle made by 1. Point O1 is the center of a curve C3 of radius equal to OFF, and F is the intersection of the fabric edge and straight line xx'.

The radius of curvature of the seam can be changed by changing the position direction and magnitude of the velocity vector (1). For example, a new velocity vector that replaces the instantaneous rotation center with 02■
If 2 is given, curve C! will be obtained.

According to the embodiment shown in FIG. 5, the orientation of the wheel is limited to an angle of no more than 45° on either side of the direction BH due to the size of the horizontal main axis around which the wheel rotates. should be kept in mind.

When the position direction of the velocity vector is aligned with the right side of the drawing limited by the straight line BH, the resulting curve becomes convex. When fitted to the left part, the resulting curve is concave.

An example of this latter case corresponds to the vector ■.

When the instantaneous center of rotation is Ox, a concave curve C3 is obtained. It is clear that this latter case is given by way of example only and is applicable only to plane stitching and non-three-dimensional stitching. FIG. 6 shows curved seams obtained with various instantaneous centers of rotation.

The edge detector P must be positioned such that the photodetector cell is on either side of the theoretical path of the edge of the piece of fabric being guided, depending on the location of the cell, the seam and edge of the fabric. The distance "e" to the part is determined. If the seam continues a different curve, the theoretical path of the edge relative to the desired curve must be modified theoretically as a function of advancing the seam to maintain a constant cell position. A comparable result can be obtained using a row of cells in which only the two surrounding cells are active. In reality, there is no need to perform this correction due to the accuracy.

The selection of the propulsion point B is dictated by the seam being made at the time and is determined by the distance from the edge closest to this point. Depending on the curvature of the suture being made at that time, the needle will pass through the straight line "m"
It may also be positioned on the other side of D.

The 171st place W is simply determined by experts in this field.

The angular position of the drive wheel 9 is determined by the edge position of the fabric according to the illustrated embodiment by an edge detector B comprising a photodetector 36, which is arranged in an enclosure 37 fixed to the arm of the sewing machine. While shown, the zero division device 22 is indicated by the potentiometer 18.
B guides the light beam to a shiny receiving plate 29 and reflects it.

The reflected light beam hits a photoelectric sensor formed by a strip of diodes mounted on an integrated circuit aligned to 0.1 mm. The strip used in this device contains 64 diodes, making this fully possible within the given range of 6.4 mm. The size of the diode (0.1 mm) is selected such that its width is smaller than the diameter of the threads forming the fabric, in particular the threads forming the overlay of a net or lace. Therefore, the position of the thread can be detected to about 0.1 mm, which is sufficient to obtain a stitch accuracy of ±0.5 mm.

The light rays striking the fabric are diffused with low intensity while the rays striking the sides or inner surfaces of the gap are reflected and focused by the diode strip optics. This will set up a set of signals that are weak on the opposite side of the fabric and strong away from the fabric.

These signals are processed to find and cut the edges, and the profile shape due to the gap is determined by the radius of curvature ( This is done in consideration of the fact that the gap is several millimeters, whereas in the case of cutting, the gap is a minimum of 30 mm), so that the shape can be distinguished from the shape created by cutting.

The states of the various diodes 3G (FIG. 7) are observed by cycle scanning, timed by a clock signal 40 and formed by a synchronization signal 41 from a multiplexer 42 to form a video signal. 8th
The signal timing diagram shown in the figure corresponds to a strip of 10 photodiodes for simplicity of illustration, but the example uses a strip of 64 photodiodes.

For the video signal, each level represents the illumination of the photodiode. This figure shows three consecutive scans +, n, m triggered by three synchronization signals A, B and C.
This corresponds to a one-time fabric replacement, and explains that the signal is modified at each synchronization.

In the first scan I, two low levels are seen between the high levels, which correspond to the holes in the lace.

If there is no fabric, the level should be zero, but in reality the level does not reach zero. In order to clearly separate the signals corresponding to the presence or absence of fabric, a threshold (a
43 are limited. Limitations ゛The comparator 44 that accepts the signal and the video signal separates the levels,
Either all or none of the signals 45 are available.

The output of comparator 44 is a bistable flip.

The signal is sent to the flop circuit 45. During the scanning of the strip, when the fabric is first encountered, a signal is generated which puts the bistable flip-flop circuit into the state shown in FIG. When A arrives, it is only reset to LiO. Therefore, the gating circuit 46 controlled by the bistable output signal, in which only the edges of the fabric and not the seam holes are taken into account,
A number of clock signal pulses 40 are passed, which correspond to the position of the first photodiode indicated by the edge of the fabric.

A counting circuit 47 triggered by the synchronization signal 4I measures the number of pulses contained in each bistable output signal passing through the gating circuit 46 between the two synchronization signals 41. The counting result is controlled by the synchronization signal after the time change,
Transferred to transfer register 48 by transfer control circuit 49, which can also reset counter 47 to zero.

The count value obtained in advance is converted into a voltage by a digital-to-analog converter 50. One signal is thus obtained which corresponds to the distance between the edge of the fabric and the edge of the strip.

This edge signal precisely follows the shape obtained after cutting, including the contour of the gap cut by the cutting line of the perforated fabric.

A second processing of the signal is required to reconstruct the cutting line, which consists in following the edge signal from peak to peak in order to jump the gap.

It has been stated that the apparent curvature of the fabric within the area of the sensor causes signal fluctuations that are very slow compared to the signal fluctuations caused by gaps.

It is therefore possible to limit the fluctuations of the signal in the direction of the gap depression due to the slope value which corresponds to the signal mentioned in the case of a maximum apparent curvature of 30 mm at zero in the exemplary embodiment.

The analog signal obtained in the first process is sent to a correction circuit 51 that converts this signal into a peak signal.

This correction is obtained from two time constants: a short time constant that reaches its maximum value rather early, and a long time constant that can lead to a minimum curve due to the guidance followed by the fabric.

The signal obtained at the output of the correction circuit 51 is sent to the central circuit 52, where it is calibrated into the form of signal e2.

The signal from the angular position measuring device 18 is also sent to the central circuit 53, where it is calibrated in the form of signal e1.

The signals e and e2 are exemplified by at least three comparator circuits 55, 56 and 57, whose outputs are connected to three relays 58, 59 and 60 (e.g. Siemens TCA). 965)
(FIG. 9) is sent to a comparison and control circuit 54 formed from (FIG. 9). The circuit 58 allows the speed of the servo motor 19 to be limited by inserting a series of resistors R, and the circuits 59 and 60 determine the direction of rotation ROT+ and ROT- and the stopping of the motor by having the same polarity at the terminals. Limited.

Comparator 55 receives signal e1 for comparison with two stop values, maximum and minimum. These two values are sent to a comparator 57 which accepts the values of el and e2. One of the relays 59 of the motor circuit is activated by the signal e, >el + ε1, with ε1 as the trigger value, and the other relay is activated by the signal e, <e2-ε1.

If both relays are in the same state, the motor has the same polarity at its terminals and is stationary, otherwise it is rotating in one direction or the other.

Comparator 56 provides a signal e to connect or disconnect the speed limit register to the motor circuit.
, and e2 are compared with the trigger value ε2.

In the illustration of this embodiment, it is assumed that the tangential speed of the drive wheel automatically changes its position direction, i.e. that the drive comprises a spherical wheel driven by rollers 21 at a constant speed as described above. I've been doing it.

Clearly, a device without this feature would require a circuit capable of powering the drive wheel servo motor 230 to provide a variable power supply voltage depending on the wheel position direction α.

〔Effect of the invention〕

As described above, according to the present invention, by detecting the edges of the fabric, the spherical wheels can be controlled to freely fold the fabric, making it possible to efficiently stitch curves according to the required curvature. can. Further, since the use of flexible fabric is taken into consideration, there is an advantage that wrinkles do not occur when changing the direction of the fabric to be sewn.

[Brief explanation of the drawing]

FIG. 1 is a front view of a sewing machine equipped with a drive device and a guide device including an edge detector according to the present invention, FIG. 2 is an enlarged view of the drive device, and FIG. Figure 4 shows the variation of wheel speed as a function of the wheel position direction; Figure 5 is a basic geometric diagram explaining the operation of the guide device; Figure 6 is a curved diagram. An example of a curve to be sewn along, Figure 7, processes the signal from the edge detector that follows the contour of the cut and, in the case of perforated fabric, corrects the signal from the detector that shows the contour of the gap. FIG. 8 is a block diagram of the electronics used to control the device which then uses this signal to propel the piece of dough, at the output end of the circuit shown in block form in FIG. A timing diagram of various signals obtained, and FIG. 9 is a diagram of the control circuit of the drive device. 3...needle, 4...presser metal fitting, 7...claw, 9
... Spherical wheel, 18 ... Angular position measuring device, 1
9.230...Servo motor, 21...Roller, 29...Temporary receiver, 32.33...Dough piece, 36...Photodetector.

Claims (7)

[Claims] (1) at least one receiving plate, a driving wheel that presses down the fabric guided on the receiving plate, and a control device for the driving wheel;
a fabric edge position detector, said detector comprising at least one photodetector placed in front of the edge used for guiding the fabric; and an electronic circuit for converting signals provided by the device into control signals for the drive device. The main shaft 10 is parallel to the main shaft 10 and moves around the shaft center, and one end of the main shaft 10 is fixed to one end of a shaft 14 whose extension line passes through the center and is substantially perpendicular to the receiving plate. A spherical drive wheel 9 that moves in the same direction, a wheel whose axis is parallel to the receiving plate and supported by the same frames 17 and 20, and an axis 1
4 and a drive roller 21 that controls the rotation of the roller 21.
, an angular position measuring device 18 , and a rotation control device 19 provided at the other end of the shaft 14 , a device for guiding a flexible fabric cloth to form a three-dimensional stitch. (2) At the point of contact with the fabric, the tangential speed V_1 of the drive wheel 9 changes according to a cosine angle α whose plane of symmetry perpendicular to its axis coincides with the plane of symmetry of the drive roller 21 at a constant speed Vg.
A device according to claim (1) having: (3) Speed vector of drive wheel 9 @ V @ 1 minute force @
Device according to claim (2), in which V@_0 is parallel and equal to the velocity vector @V@_0 of the feed device 7. (4) The fabric edge position detector comprises a sensor formed by a strip of photodiodes and a light source emitting a light beam that is reflected on a backing plate 29 through which the edge of the fabric passes, and a square diode. a multiplexer 42 for forming a video signal from the signal of the strip; a comparator 44 for dividing the level of the video signal to either all signals or no signal; a bistable flip-flop circuit 45 for setting up to state 0; a gate circuit 46 for passing a number of clock pulses and corresponding to the position of the first diode marked by the edge of the fabric; a counting circuit 47; a resistor 48, a digital-to-analog converter 50 whose output voltage corresponds exactly to the observed edge contour, and a hole which converts the output signal produced by the perforated fabric into a peak-to-peak jump signal. Correction circuit 51
and a comparison and control circuit 54 for comparing the processed signal from the correction circuit and the position signal from the position sensor 18 to control the position direction and speed of the drive device. Equipment according to. (5) The photodiodes forming the strip are
Device according to claim (4), having a maximum diameter that is smaller than the diameter of the thread forming the perforated fabric stitch. (6) The motor comparison and control circuit 54 includes three lumped comparator circuits 55, 56, 57, the first comparator circuit 55 receiving the processed signal e_2 from the diode strip and converting it into the maximum and minimum s_1 ,s
The second comparator circuit 57 accepts the two stop values and the signals e_1 and e_2 from the diode strip 36 and the position sensor 18, and the outputs of the comparator circuits 55 and 57 are compared with the two stop values of _2. Applying two signals greater or less than the reference value e_2, which is increased or decreased by the trigger value ε_1, actuates the relay controlling the servo motor 19 to orient the drive, and the third comparator circuit 56 directs the position sensor 18. Signal e_1 from diode strip 36
_2 with a reference value ε_2 and including a resistor in the power supply circuit of the servo motor 19 to limit its speed. (7) The driving wheel 9 is rotationally driven by a servo motor 230, and the edge detector includes a circuit for powering the servo motor 230 to provide a variable power supply voltage depending on the wheel position direction α. A device according to either claim (3) or (4).