DEVICE FOR ADJUSTING AN OPTICAL ENCODER WITH PHOTODETECTORS AND CORRESPONDING ADJUSTMENT PROCEDURE

Description

[0001] The present invention relates to a device for adjusting an optical encoder with photodetectors and to an adjustment method.

[0002] An optical encoder is a device for determining the angular position of a moving object relative to another object. To do this, a disk with opaque and transparent areas is rotated by the encoder shaft. An optical beam emitted by infrared diodes passes through the transparent areas of the rotating disk and strikes photodetectors, creating an analog signal that is amplified and converted into a digital signal, which is then transmitted to a data processing means that provides the angular position. A photodetector is an electronic component that reacts to light. It generates a current depending on the amount of light received. Due to the optical dispersion of optoelectronic components, it is necessary to adjust the photodetectors so that the received and emitted signals have a similar amplitude.In addition, the operating conditions of such encoders are often at so-called extreme temperatures, either positive or negative, which affects the amplitude of the encoder signal. Similarly, the process itself of using the encoder is likely to affect its stability. In other words, it is a question of correcting the amplitude differences between the photodetectors.

[0003] For this, we know a so-called manual method where decade substitution boxes are used. These are test instruments that use, in this case, a series of resistors, capacitors or inductors to replicate different electrical values. The use of such boxes requires physical wiring with the photodetectors, therefore a long operation and difficult to modify by an unskilled operator. US-A-2020292360 discloses a method for calibrating a rotary encoder of an angular position of a machine shaft. The method uses a starting point of a measurement then, after a given time with a timer, an intermediate measurement point and a final measurement point. By calculating the difference between the actual measured rotation angle position and that calculated according to the measurement time, the encoder can be corrected and calibrated.Such a method is suitable for a type of sensor, means for adjusting an optical encoder are also known from US-A-5773820, US-A-4423958 and US-A-2008 / 054169, using a setpoint value and making corrections to the output resistance value in the circuit of the photodiodes of the encoders. None of the known solutions describes an automated means for adjusting an optical encoder.

[0004] The invention provides a device and a method for adjusting an optical sensor which is quick, reliable and easy to set up and use.

[0005] To this end, the invention relates to a device for adjusting an optical encoder with photodetectors, characterized in that it comprises an optical encoder to be adjusted, a member for rotating the optical encoder, said member being adapted to receive and rotate the optical encoder, an adjustment member provided with a means of connection with a printed circuit of the optical encoder and adapted to removably cover the optical encoder in position on the rotation member, said adjustment member being adapted to send a signal with a set amplitude of the amplitude of the signal for each photodetector of each optical track of the rotating encoder, to collect a response signal emitted by the encoder when it has received the signal with the set amplitude and to modify the rotation of the encoder,the device also comprising a control member for controlling the adjustment member on the one hand and the rotation of the optical encoder on the other hand and a control member also connected to an interface.,

[0006] This results in a device where, thanks to the adjustment member, it is not only possible to collect information concerning the rotation of the encoder but also, through the interface between the control member and the control module, to modify and adjust the amplitude of the signals from the photodetector so that this amplitude of the signals is in accordance with the set value. It should be noted that the value of the amplitude is defined by the supplier of the optical encoder, knowing that several values ​​of the amplitude can be assigned to the same encoder.

[0007] According to advantageous but not mandatory aspects of the invention, such an adjustment device may comprise one or more of the following characteristics: The means for connecting the adjustment member to the printed circuit comprise telescopic connecting pads distributed over one face of the adjustment member. The means for connecting the adjustment member to the printed circuit comprise specific connectors distributed over one face of the adjustment member. The adjustment member comprises an adjustable matrix of at least four resistors. The adjustment member comprises an adjustable matrix of sixty-four resistors. The resistors cover a range from 1 kΩ to 47 kΩ. The control member comprises at least one data acquisition member such as an analyzer or an oscilloscope.

[0008] The invention also relates to an adjustment method using an adjustment device conforming to any one of the preceding characteristics, characterized in that it comprises at least the following steps: a) positioning the adjustment member on the printed circuit of the encoder by positioning the connection means of the adjustment member on the contact reception pads or the interconnection vias of the printed circuit of the encoder, b) defining, from the control member, at least one setpoint value of the amplitude of the signal for each photodetector of each optical track of the encoder, c) collecting, when the encoder is rotating, at least one signal emitted by each photodetector constituting an optical track, in response to the received setpoint signal, d) comparing the amplitude of the received signal with the amplitude of the setpoint signal defined in step b), e) varying in steps, constant or not, the difference between the value of the amplitude of the setpoint signal and the value of the amplitude of the signal emitted by the photodetector, f) validating the adjustment by taking the smallest difference between the value collected in step c) and the setpoint value of the amplitude of the signal.

[0009] According to advantageous but not obligatory aspects, such a method may comprise the following steps: In step c), a maximum of sixteen signals are collected per track. In step c), a maximum of forty signals are collected, distributed over several tracks. In step e), the amplitude of the received signal and its inverse are adjusted.

[0010] The invention will be better understood and other advantages thereof will appear more clearly on reading the description which follows, given solely by way of non-limiting example and made with reference to the appended drawings in which: [ Fig. 1 ] is a diagram illustrating the operating principle of an adjustment device for an optical encoder according to an embodiment of the invention, .[ Fig. 2 ] is a simplified perspective view of an adjustment device for an optical encoder according to an embodiment of the invention, [ Fig. 3 ] is a partial view, on a larger scale, of part of the device of the figure 2 , in operating configuration with a means of adjusting the rotation of the encoder, [ Fig. 4 ] is a partial and simplified view, on another scale, of the adjustment organ in position on the encoder, [ Fig. 5 ] is a partial view at another scale of the adjustment organ of the figure 4 , [ Fig. 6 ] is a view similar to the figure 5 of the encoder of the figure 4 And [ Fig. 7 ] is a perspective view, on a larger scale, of an embodiment of a connection means equipping the adjustment member of the figures 4 et 5 .

[0011] There figure 1 is a diagram showing an adjustment device 1 for an optical encoder. Alternatively, the device is adapted to adjust several encoders, either successively or simultaneously. The device 1 comprises a chassis 2. The chassis 2 is visible, according to one embodiment of the invention, at figure 2 . It is formed of a support plate 20, here rectangular, forming the bottom of the chassis and parallel to a plate 21, of similar shape forming the top of the chassis 2. The plates 20, 21 are kept parallel to each other by rods 22, here four rods 22 distributed at the corners of the plates 20, 21. The plate 21 is adapted to support at least one optical encoder 3. The latter is connected to a shaft 4 for rotating the encoder 3.

[0012] The shaft is driven by a drive system comprising an inertial mass 5. The mass 5 and the major part of the shaft 4 are located between the plates 20, 21 of the chassis 2. As is apparent from the figure 2 , a means for varying the rotational speed of the mass 5, known per se by an inertia flywheel, is present in the chassis 2. It comprises a set 50 of pulleys of different diameters, driving the mass 5 by a belt 51. An electric motor, known per se and not referenced, is positioned under the set 50 of pulleys in order to drive the rotation shaft of the pulleys. As a variant, other means for varying the rotational speed of a rotational drive system, known per se, are used.

[0013] The encoder 3 itself is located above the chassis 2, on the plate 21 directly above an opening made in the plate 21 and allowing the connection with the shaft 4 of the mass 5. Guiding and orientation means are provided in order to precisely position the encoder 3 on the plate 21. A coupling member 40 is mounted at the end of the shaft 4 and ensures the coupling and centering of the shaft 4 in the housing adapted on the encoder 3. The encoder 3 is held in position on the plate 21 by a removable support 30. The encoder 3 comprises in the upper part a printed circuit 6. As an example, a printed circuit is illustrated in FIG. figure 6 , it being understood that other printed circuits can equip the encoder 3. On the printed circuit 6, accessible from the upper face of the plate 21, an adjustment member 7 is positioned.

[0014] The adjustment member 7 is advantageously of a shape complementary to the support 30. Alternatively, it is of another shape. In all cases, the adjustment member 7 comprises specific connectors. Here, advantageously, it is a plurality of studs 8, advantageously of variable length, for example telescopic. A stud 8 is illustrated in the figure 7 . It is formed, in the example, of a cylindrical segment 80 with a circular base in which a segment 81 of complementary shape slides freely, without friction. A spring internal to the pad 8 keeps the segments 80, 81 in a distant position. The free end 82 of the segment 81 is configured as a rounded sphere, so as not to damage the receiving areas or the interconnection vias of the printed circuit 6 during contact of the member 7 with the circuit 6. Similarly, the return force of the internal spring of each pad 8 is adapted so that the end 82 of each pad 8 is in contact with the receiving areas of the printed circuit 6 but without strong pressure risking damaging the printed circuit.

[0015] The pads 8 are distributed over a face 9 of the adjustment member 7. The number and distribution of the pads 8 are adapted to the number and position of the receiving areas on the printed circuit 6 of the optical encoder. In order for each pad 8 to be correctly positioned on a receiving area of ​​the printed circuit, a guide means, not illustrated, is provided. These are, for example, feet, notches and reliefs of complementary shape made on the support 30 and on the member 7 associated with a locking in position of the member 7 on the circuit 6 for example by screwing in quarter turns. Alternatively, other guide means known per se are used. Such a guide means also acts as a key, thus avoiding any erroneous positioning of the member 7 relative to the circuit 6. In other words, each printed circuit 6 is associated with an adjustment member 7.

[0016] The connection between the pads 8 and the printed circuit 6 is made by simply pressing the end 82 of each pad 8 on the receiving area of ​​a metal contact of the printed circuit 6. Such a connection between the adjustment member 7 and the printed circuit 6 is therefore easy to establish and remove and it does not affect the optical encoder and / or its other connections. In addition, to establish such a connection, it is not necessary to modify the circuit 6 and / or to carry out welding between the circuit 6 and the member 7, the connection is completely removable and it is not necessary to have special tools and / or knowledge to put it in place or undo it.

[0017] The adjustment member 7 is connected to an interface 10 ensuring communication between the various components of the device 1. The interface 10 can also act, directly or via the member 7, on the printed circuit 6. The interface 10 is connected to a control member 11 and to a command member 12. These various connections are wired or, alternatively, wireless. Between the interface 10 and the adjustment member 7, at least two connections, 13, 14 are established. The connection referenced 13 ensures the acquisition and collection of the values ​​and data relating to the signal emitted by the encoder 3, more particularly by a photodetector when the latter is excited by a light ray. The interface 10 relays this signal to the control member 12 by a double connection, here wired, 15 and to the control member 11 by a double connection, here wired, 16.The control member 12 generates orders and instructions, on the one hand to the adjustment member 7 via the interface 10 and on the other hand to the rotation drive system, via a dedicated wired link 17 here. For the transmission of instructions from the control member, the interface 10 uses the wired link 14 dedicated to it. As is apparent from the . figure 4 , the links 13 and 14 are combined, each pad 8 being provided with an individual connection to the interface 10 which allows the sending and receiving of data between each pad 8 and the interface 10.

[0018] According to an advantageous embodiment, the control member 11 comprises at least one data acquisition member such as an analyzer, or as illustrated an oscilloscope, while the control member 12 comprises at least one computer, portable or not. The member 12 makes it possible, via the interface 10, to store the setpoint data, the received data and to send the commands to the printed circuit to adjust the amplitudes between the setpoint data and those received. Alternatively, the control members 11 and command members 12 are different and / or formed of several devices or combined into a single device.

[0019] The adjustment process is now described, with reference to the figure 1 The first step, hereinafter referred to as step a), consists of positioning the adjustment member on the printed circuit 6 of an optical encoder 3. The latter has previously been placed on the chassis 2, as illustrated in figure 1, namely that a part of the rotation shaft 4 is positioned in the internal volume of the chassis and connected to the ground 5 via the coupling driving the shaft 4 in rotation. Furthermore, the chassis 2 can be configured to receive several encoders, for successive or simultaneous adjustments, using adjustment devices operating in parallel or a device adapted to carry out the adjustment of several encoders at the same time.

[0020] In all cases, during this step a), the connection pads 8 of the adjustment member 7 are positioned on the contact areas of the printed circuit. The member 7 is simply placed in support so as to make electrical contact with the printed circuit.

[0021] At the end of step a), the encoder 3 is in place on the chassis 2 and is ready to be rotated, the mass 5 being connected by a wired connection 17 with the control member 12. Similarly, the adjustment member 7 is ready to exchange information, via the wired connections 13 to 16 between the interface 10, the control member 11 and the control member 12.

[0022] The next step or step b) consists of defining a setpoint value for the signal amplitude for each photodetector of each track of the optical encoder 3. It is understood that this step can be carried out upstream or definitively, provided that these setpoint values ​​are adapted to the photodetectors to be adjusted. In practice, this involves defining a value of the resistance associated with the photodetector in response to a light beam and to the optical alignment. In other words, it involves defining an expected value of the resistance that a given photodetector must provide in response to the light beam striking it, taking into account environmental constraints and the use of the encoder, for example the temperature, the rotation speed but also taking into account the electronic processing capabilities of the encoder, these parameters are used to obtain a balance to define a setpoint amplitude.It should be noted that the encoders are provided with digital resistors. This setpoint value is stored in the control unit 12. In the case where the adjustment is carried out on the same encoder, it is possible to define several setpoint signals per photodetector, according to variables such as environmental conditions, the type of light beam or other. Advantageously, a configuration file for the encoder(s), with the setpoint values ​​for each encoder, is integrated into the control unit 12.

[0023] The next step or step c) is a step of collecting data emitted by the optical encoder 3 in response to the received light. For this, the encoder 3 is rotated, under known and controlled conditions, from the control member 12 which starts the rotation drive system, via the wired link 17. In this configuration, each photodetector has a variable signal amplitude depending on whether or not it is illuminated. This value of the signal amplitude is sent, by the link 13 to the interface 10 which will retransmit it, by the link 15 to the control member 12 and by the link 16 to the control member 11. During this step, the device can collect several signals simultaneously, with a maximum of sixteen signals per track and a maximum of forty signals when these are distributed over several tracks of an encoder. Alternatively, the signals are collected in a staggered manner, which increases the number of signals collected.

[0024] The next step, referenced d) is a step of comparison between the value of the amplitude of the setpoint signal and the value(s) of the amplitude of the signal(s) received from the optical encoder 3. The signal(s) emitted by the encoder 3 are directly collected by the adjustment member 7 and transmitted by the wired link to the interface 10 which relays them to the control member 11 and to the control member 12 by the wired links 16, respectively 15. The received signals are represented, on the control member 11, therefore here on an oscilloscope, in the form of curves. The control member displays, in certain cases, a double curve: that corresponding to the received signal and that corresponding to the inverse of the received signal.The shape of these curves is sinusoidal, trapezoidal, square depending on whether the signal comes from a photodetector placed on a so-called low-weight or high-weight optical track depending on the quantity of light arriving on the photodetector, therefore depending on the number of transparent zones arranged in the disc at this level. By displaying, in certain cases, the signal and its inverse, we check that the variation between the set value and the received value is indeed the same on the two curves. In this case, it is possible to cancel the difference between the set value and the received value, by phase opposition between the curves, which allows optimal adjustment.

[0025] The next step, namely step e) is an adjustment step carried out by the control member 12 via the link 15 with the interface 10 and the link 14 making it possible to manage and modify the characteristics of the optical encoder 3, by means of the adjustment member 7 acting on the printed circuit 6. The control member 12, depending on the difference observed between the set value of the amplitude of the signal and the value of the amplitude of the emitted signal, initiates a step-by-step type adjustment. The step is not constant. Alternatively, the step is constant. In the example, the step is not constant and decreases as the difference between the two values ​​reduces and as one tends towards the set value. The adjustment consists of varying, in one direction or the other, by increasing or decreasing, the resistance of the photodetector, resistance generally varying between 1 kΩ and 47 kΩ. It is understood that the adjustment range is adapted to the resistances and therefore can go beyond 47 kΩ.The adjustment member comprises an adjustable matrix of at least four resistors, in the example sixty-four resistors. The control member acts on the interface 10 which varies the resistance of the photodetector. The result is displayed and therefore controlled on the oscilloscope 11.

[0026] When the difference is considered minimal or at least acceptable by the control member 12, the device initiates, during a step referenced f), a validation of the setting which will be stored in a non-volatile memory in the electronics of the printed circuit 6. The smallest difference is taken into account to validate the final value.

[0027] It is possible, in an additional step, to carry out a validation test of the set value by carrying out steps a) to d) again.

[0028] When an optical track includes a defect, the latter, in general, appears regularly and repetitively on the curves generated by the control member 11. It is then possible, via the control member 12 and the interface 10, to indicate to the operator, by visual and / or audible information, that there is a defect on an optical track of the encoder and to identify the track concerned. This allows early detection of the track engraving problem and therefore intervention very early on in the production line.

Claims

1. A device (1) for adjusting a photodetector optical encoder (3), characterized in that same comprises an optical encoder (3) to adjust, a member (2, 5, 50, 4, 51) for rotating the optical encoder (3), said member being suitable for receiving and driving the optical encoder in rotation, an adjustment member (7) having a means of connection (8, 20) with a printed circuit (6) of the optical encoder (3) and suitable (9) for movably capping the optical encoder (3) in position on the member for rotating, said adjustment member (7) being suitable for sending a signal with amplitude information on the amplitude of the signal for each photodetector of each optical track of the rotating encoder (3), for collecting a response signal emitted by the encoder (3) when same has received a signal with the setpoint amplitude and for modifying the rotation of the encoder (3), the device also including a control member (12) on the one hand of the adjustment member (7) and on the other of the rotation of the optical encoder (3) and a monitoring member (11) also connected to the interface (10).

2. The device according to claim 1 characterized in that the means of connection (8) of the adjustment member (7) with the printed circuit (6) include studs (8) for telescopic connection (80, 81) distributed on one face of the adjustment member (7).

3. The device according to claim 1 characterized in that the means of connection of the adjustment member (7) with the printed circuit (6) include specific connectors distributed over a face of the adjustment member (7).

4. The device according to claim 1 characterized in that the adjustment member (7) comprises an adjustable matrix of at least four resistors.

5. The device according to claim 4 characterized in that the adjustment member (7) comprises an adjustable matrix of sixty-four resistors.

6. The device according to claims 4 or 5 characterized in that the resistors cover a range going from 1 kΩ to 47 kΩ.

7. The device according to claim 1 characterized in that the monitoring member (11) comprises at least a data acquisition member, such as an analyzer or an oscilloscope (11).

8. An adjustment method using an adjustment device according to any of the preceding claims, characterized in that said method includes at least the following steps: - a) positioning the adjustment member (7) on the printed circuit (6) of the encoder (3), by positioning the means of connection (8) of the adjustment member (7) on the receiving ranges of the contacts or interconnection vias of the printed circuit (6) of the encoder (3), - b) defining, from the control member (12), at least one amplitude instruction value of the signal for each photodetector of each track of the optical encoder (3), - c) collecting, when the encoder (3) is rotating, at least one signal emitted by each constituent photodetector from an optical track in response to the instruction signal received, - d) comparing the amplitude of the received signal with the amplitude of the instruction signal defined in step b), - e) varying in steps, whether constant or not, the difference between the amplitude value of the instruction signal and the amplitude value of the signal emitted by the photodetector, - f) validating the adjustment by taking the smallest difference between the value collected at step c) and the setpoint value of the amplitude of the signal.

9. The method according to claim 8 characterized in that during step c), a maximum of sixteen signals are collected per track.

10. The method according to claim 8 characterized in that during step c), a maximum of forty-eight signals distributed over a plurality of tracks are collected.

11. The method according to claim 8 characterized in that during step e), the amplitude of the received signal and the inverse thereof are adjusted.