Signal processing circuit for encoder

The present invention relates to an encoder signal processing circuit that processes signals from a plurality of encoder heads.

The encoder is configured to generate at least two phases of analog periodic signals (encoder signals) having different phases according to the displacement of the moving body. Generally, an encoder includes a scale attached to a fixed body and an encoder head provided on a moving body arranged so as to face the scale and outputting an encoder signal according to a change in the relative position with respect to the scale. Have. The encoder having such a configuration can measure the traveling direction, position, displacement, speed, etc. of the moving body by processing the encoder signal output from the encoder head in the encoder signal processing circuit.

In recent years, for example, Patent Document 1 has proposed an encoder signal processing circuit in which encoder signals from a plurality of encoder heads are processed by a single encoder signal processing circuit.

<p><patcit num="1"><text>Japanese Unexamined Patent Publication No. 7-139967</text></patcit></p>

<p> Here, in the encoder signal processing circuit proposed in Patent Document 1, in order to guarantee the temporal identity of the encoder signals from the respective encoder heads, the encoder signals from a plurality of encoder heads are processed into the encoder signal processing circuit. All the encoder signals from each encoder head are acquired during the same sample hold by sequentially inputting to. In this case, as the number of encoder heads increases, the time until the processing for all the encoder signals is completed also increases accordingly. Therefore, in order to process a plurality of encoder signals in a short time in the configuration of Patent Document 1, it is possible to process an IC or the like used as a signal processing circuit for an encoder at a higher speed as the number of encoder heads increases. There is a need to.</p><p> The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an encoder signal processing circuit capable of efficiently processing encoder signals output from a plurality of encoder heads by a single processing circuit. And.</p>

<p> In order to achieve the above object, the signal processing circuit for an encoder according to one aspect of the present invention responds to the amount of relative displacement with respect to the corresponding scale (the amount of relative displacement may be a change in position or a change in angle). A signal processing circuit for an encoder that processes each of the encoder signals from a plurality of encoder heads that output the encoder signals, which is either a processing unit that generates displacement information from the encoder signals or the plurality of encoder heads. During the processing of the encoder signal from the above, a processing determination unit for determining at least one of the content of processing for the plurality of encoder heads and the content of processing for the encoder signals output from the plurality of encoder heads is provided. It is characterized by doing.</p>

<p> According to the present invention, it is possible to provide an encoder signal processing circuit capable of efficiently processing encoder signals output from a plurality of encoder heads by a single processing circuit.</p>

<figref num="1">It is a figure which shows the structure of the encoder system which includes the signal processing circuit for an encoder which concerns on 1st Embodiment of this invention.</figref><figref num="2">It is a figure which shows the internal structure of one encoder head.</figref><figref num="3">It is a flowchart which shows the operation flow of the encoder system in 1st Embodiment of this invention.</figref><figref num="4">It is a figure which shows the structure of the encoder system which includes the signal processing circuit for an encoder which concerns on 2nd Embodiment of this invention.</figref><figref num="5">It is a flowchart which shows the operation flow of the encoder system in 2nd Embodiment of this invention.</figref><figref num="6">It is a figure for demonstrating the calculation method of the latest readable time.</figref><figref num="7">It is a figure which shows the deformation example when the maximum permissible displacement amount holding part is provided inside the encoder head.</figref><figref num="8">It is a figure which shows the structure of the encoder system which includes the signal processing circuit for an encoder which concerns on 1st modification of 2nd Embodiment of this invention.</figref><figref num="9">It is a figure for demonstrating the signal processing circuit for an encoder which concerns on the 2nd modification of the 2nd Embodiment of this invention.</figref><figref num="10">It is a figure which shows the structure of the encoder system which includes the signal processing circuit for an encoder which concerns on 3rd Embodiment of this invention.</figref><figref num="11">It is a flowchart which shows the operation flow of the encoder system in 3rd Embodiment of this invention.</figref><figref num="12">It is a flowchart which shows the example of the processing of the encoder signal in the 3rd Embodiment of this invention.</figref><figref num="13">It is a flowchart which shows the modification in the case of switching the encoder signal which is preferentially processed according to the change of a relative speed.</figref><figref num="14">It is a flowchart which shows another modification in the case of switching the encoder signal which is preferentially processed according to the change of a relative speed.</figref><figref num="15">It is a figure for demonstrating the modification in the case of determining the processing order of the encoder signal and the number of processings according to the priority of processing of an encoder signal.</figref><figref num="16">It is a figure which shows the modification when the user can set the combination setting of an encoder head and the setting of a signal processing content.</figref>

Hereinafter, embodiments of the present invention will be described with reference to the drawings. [First Embodiment] First, the first embodiment of the present invention will be described. FIG. 1 is a diagram showing a configuration of an encoder system including a signal processing circuit for an encoder according to the first embodiment of the present invention. The encoder system in this embodiment has a plurality of sets of scales and encoder heads, and processes encoder signals output from the respective encoder heads by using a single encoder signal processing circuit.

The encoder system shown in FIG. 1 has a plurality of fixed bodies 1a, 1b, and 1c (three in the example of FIG. 1). A scale 101a is attached to the fixed body 1a. Similarly, the scale 101b is attached to the fixed body 1b, and the scale 101c is attached to the fixed body 1c. Displacement detection patterns arranged at predetermined periods are formed on the scales 101a, 101b, and 101c, respectively.

Further, the encoder system shown in FIG. 1 has a plurality of mobile bodies 2a, 2b, and 2c arranged so as to face each of the fixed bodies 1a, 1b, and 1c. The moving bodies 2a, 2b, and 2c are configured to be displaced relative to the corresponding fixed body.

The drive unit 3a is attached to the moving body 2a. Similarly, the drive unit 3b is attached to the moving body 2b, and the driving unit 3c is attached to the moving body 2c. Each of the drive units 3a, 3b, and 3c is configured to have a drive mechanism such as a motor, and displaces the moving bodies 2a, 2b, and 2c in a predetermined displacement direction according to a drive signal from the drive control unit 300.

The encoder head 102a is attached to the moving body 2a. Similarly, the encoder head 102b is attached to the moving body 2b, and the encoder head 102c is attached to the moving body 2c. The encoder heads 102a, 102b, and 102c are displaced according to the displacement of the moving bodies 2a, 2b, and 2c, respectively, and output the encoder signal corresponding to the relative displacement with the corresponding scale to the encoder signal processing circuit 200.

Here, in the example of FIG. 1, the scales 101a, 101b, 101c are attached to the fixed bodies 1a, 1b, 1c, and the encoder heads 102a, 102b, 102c are attached to the moving bodies 2a, 2b, 2c. , 101b, 101c may be attached to the moving bodies 2a, 2b, 2c, and the encoder heads 102a, 102b, 102c may be attached to the fixed bodies 1a, 1b, 1c. Further, the displacement directions of the moving bodies 2a, 2b, and 2c may be different or the same.

FIG. 2 is a diagram showing an internal configuration of the encoder head 102 of one of the encoder heads 102a, 102b, and 102c. Here, FIG. 2 shows an example of an encoder head of a reflective optical encoder. The encoder head 102 shown in FIG. 2 has a light source 1021 and a detection unit 1022. The light source 1021 irradiates a light beam having coherence onto a scale 101 provided so as to face the light source 1021. The detection unit 1022 has four-phase photodiodes that generate four-phase analog periodic signals (encoder signals) whose phases differ by 90 degrees. The detection unit 1022 having such a configuration receives the pattern projected from the scale 101 by the light rays emitted from the light source 1021 by each of the four-phase photodiodes, and determines the amount of light of the pattern received by each photodiode. Generates a proportional encoder signal.

Let's return to Figure 1 and continue the explanation. The encoder signal processing circuit 200 has a processing unit 201 and a processing determination unit 202. The encoder heads 102a, 102b, and 102c are connected to the encoder signal processing circuit 200 by sharing wiring. In such a configuration, the encoder signals are appropriately input from the encoder heads 102a, 102b, 102c to the processing unit 201.

The processing unit 201 has a reading unit 2011 and a signal generation unit 2012. The reading unit 2011 reads the encoder signal from the encoder head of the combination according to the head selection signal from the reading combination selection unit 2021 of the processing determination unit 202 and outputs the encoder signal to the signal generation unit 2012. The signal generation unit 2012 processes the encoder signal input from the reading unit 2011, calculates the relative displacement between the scale and the encoder head, and outputs the calculated relative displacement to the drive control unit 300 as displacement information. As a method for calculating the relative displacement, various methods such as a resistance division method, a tangent method, and a ROM reference method are known. In the present embodiment, the method for calculating the relative displacement is not particularly limited, and any method may be used.

The processing determination unit 202 has a read combination selection unit 2021. The read combination selection unit 2021 generates a head selection signal according to the moving body information from the drive control unit 300 and inputs it to the read unit 2011. In the present embodiment, when the encoder system is in operation, a user of the encoder system (hereinafter, simply referred to as a user) or the like can select and determine a combination of moving bodies to be used at that time. At this time, if there is an unused moving body, it is not necessary to read the encoder signal from the encoder head corresponding to the moving body, so that fact is input to the reading unit 2011 as a head selection signal. In response to this, the reading unit 2011 prevents the encoder signal from the encoder head corresponding to the unused mobile body from being read.

The drive control unit 300 controls the operations of the drive units 3a, 3b, and 3c according to the displacement information input from the signal generation unit 2012 of the encoder signal processing circuit 200. That is, the drive control unit 300 receives displacement information (or speed information calculated as a time change of the displacement information, etc.) input from the encoder signal processing circuit 200 with the relative displacement of the moving bodies 2a, 2b, and 2c. The magnitude and polarity of the drive signal supplied to the corresponding drive unit are changed so as to reach the target value. By changing the magnitude of the drive signal, the magnitude of the displacement speed of the moving body driven by the corresponding drive unit changes. On the other hand, by changing the polarity of the drive signal, the direction of the displacement speed of the moving body driven by the corresponding drive unit changes.

The operation of the encoder system in this embodiment will be described below. FIG. 3 is a flowchart showing the operation flow of the encoder system according to the first embodiment.

In FIG. 3, the mobile body to be used is selected prior to operating the encoder system. The selection of the moving body may be manually performed by the user, or may be automatically performed by the drive control unit 300. For example, in the case of manual selection, the user operates an operation unit (not shown) to specify a combination of moving bodies to be used. When the moving body is selected, the combination information (moving body information) of the selected moving body is input to the drive control unit 300. In response to this, the drive control unit 300 supplies a drive signal to the drive unit corresponding to the moving body specified by the moving body information to start the operation of the driving unit. At this time, the drive control unit 300 also turns on the power of the corresponding encoder head (step S101).

After the operation of the drive unit and the encoder head is started, the read unit 2011 reads the encoder signal from any of the encoder heads of the combination according to the head selection signal from the read combination selection unit 2021. Then, the reading unit 2011 converts the read signal into a digital signal and outputs it to the signal generation unit 2012 (step S102). The reading order of the encoder signals in step S102 is, for example, the order of the encoder heads 102a, 102b, 102c, but is not limited to this. Further, the encoder signals from the respective encoder heads may be read out at the same time. In this case, each read encoder signal is held in the reading unit 2011.

Upon receiving the input of the encoder signal, the signal generation unit 2012 processes the input encoder signal and starts the calculation of the displacement information (step S103). In calculating the displacement information, the signal generation unit 2012 calculates the difference between the four-phase encoder signals whose phases differ by 180 degrees among the four-phase encoder signals whose phases differ by 90 degrees, and in the encoder signal detected by the detection unit 1022. Removes offset components and noise components. After such a difference calculation, the signal generation unit 2012 calculates the displacement information using the two-phase encoder signals whose phases are different by 90 degrees obtained by the difference calculation. As a method of obtaining the displacement information, various methods such as the resistance division method, the tangent method, and the ROM reference method described above can be used. For example, in the ROM reference method, the time change of the phase position (angle information) of each encoder signal specified by the amplitude (AD conversion value) of the two-phase encoder signal, that is, the angle information based on the encoder signal from a certain encoder head. The relative displacement is calculated as the difference between the angle information and the angle information based on the encoder signal previously acquired from the same encoder head as the encoder head. The previous angle information is updated for each encoder head each time the phase difference information is calculated. For example, when the phase difference information related to the encoder head 102a is obtained, only the previous angle information related to the encoder head 102a is updated, and the previous angle information related to the other encoder heads 102b and 102c is not updated.

After the start of the signal processing, the drive control unit 300 determines whether or not the signal processing is completed, that is, whether or not the displacement information has been input from the signal generation unit 2012 (step S104). The drive control unit 300 waits while performing the determination in step S104 until the signal processing is completed in step S104. In the determination in step S104, when the signal processing is completed, the drive control unit 300 determines whether or not the combination of the moving bodies to be used has been changed (step S105). For example, when a new combination of moving bodies is specified by the user during signal processing, it is determined that the combination of moving bodies to be used has been changed. In the determination of step S105, when the combination of the moving bodies to be used has not been changed, the drive control unit 300 determines the displacement amount of the corresponding moving body based on the displacement information input from the signal generation unit 2012. The magnitude or polarity of the drive signal supplied to the drive unit is controlled so as to reach the target value. After that, the process returns to step S102. In this case, the reading unit 2011 reads the next encoder signal and outputs it to the signal generation unit 2012. Further, in the determination of step S105, when the combination of the moving bodies to be used is changed, the drive control unit 300 displaces the corresponding moving body based on the displacement information input from the signal generation unit 2012. The magnitude or polarity of the drive signal supplied to the drive unit is controlled so that the amount reaches the target value. After that, the process returns to step S101. In this case, the drive control unit 300 selects the combination of the drive units again.

As described above, in the first embodiment, the encoder signal is read only from the encoder head corresponding to the selected moving body. As a result, when the encoder signals from a plurality of encoder heads are processed by a single encoder signal processing circuit 200, the encoder signals are read from all the encoder heads according to the operating conditions of the encoders. It is possible to reduce the processing load in the signal generator 2012. Further, since the number of encoder signals that need to be processed can be reduced, it is possible to shorten the read interval of the encoder signals from the individual encoder heads. As a result, it is possible to detect each short displacement, so that more accurate displacement detection becomes possible.

Further, even when the number of encoders constituting the encoder system is added or deleted, it is almost unnecessary to change the configuration of the encoder signal processing circuit 200. Therefore, it is possible to provide a highly versatile encoder signal processing circuit applicable to various encoder systems.

Here, in FIG. 1, an application example of this embodiment to a reflective optical encoder has been described, but the technique of this embodiment may be applied to a transmissive optical encoder, or magnetic. The technique of the present embodiment may be applied to a method other than the optical type such as a formula and a capacitance type. Further, the scale shown in FIG. 1 shows an example of a linear scale, and the encoder system shown in FIG. 1 uses the linear scale to detect the displacement of the length. On the other hand, the scale may be a circular scale to detect the change in angle.

Further, in the first embodiment, the encoder signal is a four-phase signal having a phase difference of 90 degrees, but the encoder signal does not necessarily have to be 90 degrees different, and has an arbitrary phase difference. Any number of signals may be output.

Further, in the first embodiment, the readout unit 2011 converts the encoder signal into a digital signal, but the encoder signal may be converted into a digital signal in the encoder head. In this case, since the encoder signal can be output as a digital signal from the encoder head, the encoder signal is less susceptible to noise in the communication path up to the encoder signal processing circuit 200. Therefore, the possibility of erroneous detection of displacement information can be further reduced.

Further, in the first embodiment, the encoder signal is read only from the encoder head corresponding to the selected moving body, but all the heads may be operated to read the encoder signal.

[Second Embodiment] Next, a second embodiment of the present invention will be described. FIG. 4 is a diagram showing a configuration of an encoder system including a signal processing circuit for an encoder according to a second embodiment of the present invention.

Similar to the first embodiment, the encoder system in this embodiment has a plurality of sets of scales and encoder heads, and uses a single encoder signal processing circuit for encoder signals output from each encoder head. Is designed to be processed. In this embodiment, the encoder signal is a periodic signal. Further, in the present embodiment, the configuration in the encoder signal processing circuit 200 is different from that of the first embodiment. Further, the encoder system in the present embodiment is also different in that it has a warning unit 400.

Hereinafter, only the parts different from the first embodiment will be described. The encoder signal processing circuit 200 in this embodiment has a processing unit 201 and a processing determination unit 202, as in the first embodiment.

As shown in FIG. 4, the processing determination unit 202 includes a maximum allowable displacement amount holding unit 2022, a latest readable time calculation unit 2023, and a latest readable time comparison unit 2024. Although FIG. 4 shows an example in which the read combination selection unit 2021 is omitted, the read combination selection unit 2021 may be provided.

Here, since the encoder signal of this embodiment is a periodic signal, if the encoder signal exceeds a certain period during continuous reading times, erroneous detection of displacement information will occur. The maximum allowable displacement amount holding unit 2022 is a memory that holds the maximum allowable displacement amount for each encoder head. The maximum allowable displacement amount is relative that can maintain relative displacement detection by the encoder head during continuous reading times of the encoder signal for each encoder head (no erroneous detection of displacement information occurs due to skipping of the encoder signal). This is the limit amount of displacement. For example, the maximum permissible displacement amount becomes large when the encoder head has a memory for holding the encoder signal. The maximum allowable displacement amount also increases when the period of the displacement detection pattern formed on the scale is large. As described above, the maximum permissible displacement amount varies depending on various conditions, and the maximum permissible displacement amount may differ depending on the encoder head and scale used. Therefore, the maximum allowable displacement amount holding unit 2022 holds the maximum allowable displacement amount for each encoder head.

The latest readable time calculation unit 2023 calculates the latest readable time for each encoder head using the maximum allowable displacement amount for each encoder head held in the maximum allowable displacement amount holding unit 2022, and the calculated latest. The readable time is output to the latest readable time comparison unit 2024 and the warning signal control unit 2013. Here, the latest readable time is a time when the relative displacement amount corresponding to a certain encoder head reaches the maximum allowable displacement amount. When the relative displacement amount reaches the maximum allowable displacement amount, the correct phase position (angle information) cannot be calculated for the encoder signal output at that time, and as a result, an error occurs in the displacement information. ..

The latest readable time comparison unit 2024 compares the latest readable time for each encoder head calculated by the slow readable time calculation unit 2023, and reads the next encoder signal from the encoder heads 102a, 102b, and 102c. Select and decide.

As shown in FIG. 4, the processing unit 201 in the present embodiment includes a reading unit 2011, a signal generation unit 2012, and a warning signal control unit 2013. The reading unit 2011 reads the encoder signals in the order according to the head selection signal from the latest readable time comparison unit 2024 of the processing determination unit 202 and outputs the encoder signals to the signal generation unit 2012. Further, the reading unit 2011 in the present embodiment has a function of measuring the time, and each time the encoder signal is read, the reading time is calculated by the latest readable time calculation unit 2023 and the warning signal control unit 2013. Output to.

The signal generation unit 2012 processes the encoder signal input from the reading unit 2011, calculates the relative displacement between the scale 101 and the encoder head 102, and outputs the calculated relative displacement to the drive control unit 300 as displacement information. The method of calculating the relative displacement is the same as that of the first embodiment. Further, the signal generation unit 2012 in the present embodiment also outputs the displacement information to the latest readable time calculation unit 2023.

The warning signal control unit 2013 compares the read time of the encoder signal from the read unit 2021 with the latest readable time received from the latest readable time calculation unit 2023. When the read time is past the latest readable time, it is considered that the relative displacement amount exceeds the maximum allowable displacement amount. In this case, since there is a high possibility that an error has occurred in the calculation result of the displacement information, the warning signal control unit 2024 outputs the warning signal to the warning unit 400.

Upon receiving the warning signal from the warning signal control unit 2013, the warning unit 400 warns the user that the relative displacement amount between the scale and the encoder head may have exceeded the maximum allowable displacement amount. The warning method by the warning unit 400 is not particularly limited. For example, when the warning unit 400 is composed of a monitor, a warning lamp, or the like, a warning can be given by display. Further, when the warning unit 400 is configured by a buzzer or the like, a voice warning can be given.

The operation of the encoder system in this embodiment will be described below. FIG. 5 is a flowchart showing the operation flow of the encoder system according to the second embodiment.

In FIG. 5, the drive control unit 300 supplies drive signals to each of the drive units 3a, 3b, and 3c to start the operation of the drive unit. At this time, the drive control unit 300 also turns on the power of the encoder head (step S201). After the operation of the drive unit and the encoder head is started, the read unit 2011 uses one of the encoder heads 102a, 102b, in the order according to the head selection signal from the latest readable time comparison unit 2024. The encoder signal is read from any of 102c and output to the signal generator 2012 (step S202).

At the first time, since the read order is not determined by the latest readable time comparison unit 2024, the read order of the encoder signal is set to a fixed order. Further, as described above, the reading unit 2011 outputs the reading time of the encoder signal to the latest readable time calculation unit 2023 and the warning signal control unit 2013 in accordance with the reading of the encoder signal. The read time input to the latest readable time calculation unit 2023 is sequentially held by the latest readable time calculation unit 2023.

The signal generation unit 2012 determines whether or not the latest readable time is calculated by the latest readable time calculation unit 2023 (step S203). In the determination in step S203, if the latest readable time is not calculated as in the first time after the encoder operation starts, the process proceeds to step S206. Further, when the latest readable time is calculated in the determination in step S203, the warning signal control unit 2013 is calculated by the read time input from the read unit 2011 and the latest readable time calculation unit 2023. It is compared with the latest readable time, and it is determined whether or not the read time exceeds the latest readable time (step S204). In the determination in step S204, if the read time exceeds the latest readable time, it is considered that an error has occurred in the displacement information calculated based on the encoder signal from the corresponding encoder head. Therefore, the warning signal control unit 2013 inputs a warning signal to the warning unit 400 to give a warning by the warning unit 400 (step S205). After that, the drive control unit 300 stops the supply of the drive signal to the drive units 3a, 3b, and 3c. As a result, the process of FIG. 5 is completed. In the example of FIG. 5, when the read time exceeds the latest readable time, the subsequent operations of the drive units 3a, 3b, and 3c are stopped. On the other hand, it is possible to give only a warning so as not to stop the operation of the drive units 3a, 3b, and 3c.

Further, in the determination in step S204, when the warning signal control unit 2013 determines that the read time does not exceed the latest readable time, the signal generation unit 2012 processes the input encoder signal to display the displacement information. The calculation is started (step S206). Since the method of calculating the displacement information is the same as that of the first embodiment described above, the description thereof will be omitted. After the start of the signal processing, the signal generation unit 2012 determines whether or not the signal processing is completed (step S207). Until the signal processing is completed in step S207, the signal generation unit 2012 waits while performing the determination in step S207. In the determination in step S207, when the signal processing is completed, the latest readable time calculation unit 2023 calculates the latest readable time for each encoder head (step S208). Then, the latest readable time comparison unit 2024 determines the read order of the encoder signal by comparing the latest readable time for each encoder head (step S209).

Here, the method of calculating the latest readable time and the method of determining the read order of the encoder signals will be described with reference to FIG. When calculating the latest readable time, the latest readable time calculation unit 2023 reads the maximum allowable displacement amount for each encoder head from the maximum allowable displacement amount holding unit 2022, and the read maximum allowable displacement amount and the read unit. The latest readable time is calculated using the read time input from 2011 and the displacement information input from the signal generator 2012. First, the reading time of the previous encoder signal is t₁, P the relative displacement calculated last time₁, The read time of the encoder signal this time is t₂, P the relative displacement calculated this time₂From, the relative velocity v (corresponding to the slope of the line segment shown in FIG. 6) is calculated according to the following (Equation 1). v = (p₂-p₁) / (T₂-t₁) (Equation 1) At this time, t₁From t₂Is the elapsed time of t₂-t₁If you know, read time t₁And t₂You don't have to know each of them. Further, the time may be the number of electric clocks or the like.

Where p₂The displacement amount obtained by adding the maximum allowable displacement amount from p₃And. At this time, for example, assuming that the relative velocity between the scale and the encoder head does not change, the displacement amount is p.₃Time to reach t₃When asked, t₃Is expressed by the following (Equation 2). t₃= t₂+ (p₃-p₂) / V (Equation 2) Furthermore, the reading unit 2011 reads the encoder signal from the encoder head._RAssuming that it takes time, the latest readable time t4 is expressed by the following (Equation 3). t₄= t₃-t_R (Equation 3) The latest readable time t represented by (Equation 2) and (Equation 3)₄If the reading of the encoder signal is started by this time, the angle information can be correctly obtained without skipping the encoder signal output from the encoder head, so that no error occurs in the displacement information. Therefore, if the encoder signals are read from the encoder head in ascending order of the latest readable time, the possibility that an error occurs in the displacement information can be reduced. Based on this idea, the latest readable time comparison unit 2024 compares the latest readable time calculated for each encoder head, and determines the encoder signal read order in ascending order of the latest readable time. To do.

In the above calculation method of the latest readable time, it is assumed that the relative speed between the scale and the encoder head does not change.₃In addition to the above, the limit value v of the drive speed of the drive unit is shown._mFrom t₃= t₂+ (p₃-p₂) / v_mAs t₃Other methods may be used, such as obtaining.

After calculating the latest readable time, the latest readable time comparison unit 2024 outputs a head selection signal to the read unit 2011 in order to change the read order of the encoder signals (step S209). After that, the process returns to step S202. In this case, the reading unit 2011 reads the next encoder signal and outputs it to the signal generation unit 2012.

As described above, in the second embodiment, after the start of reading the encoder signal, the latest readable time for each encoder head is calculated, and the read order of the encoder signal is determined according to the latest readable time. There is. As a result, the possibility that an error will occur in the calculated displacement information can be reduced depending on the operating situation of the encoder. Also, the latest readable time is the time required to read the encoder signal t._RSince it is calculated including the time, it is possible to calculate the accurate latest readable time. Further, since the reading order of the encoder signals can be determined during the signal processing in the signal generation unit 2012, the optimum processing according to the situation becomes possible.

Here, in step S204 of FIG. 5, the reading order of the encoder signals is determined for all the encoder heads. On the other hand, only the encoder head that reads the encoder signal next may be determined. In this case, the encoder head having the earliest latest readable time is used as the encoder head that reads the encoder signal next.

Further, in the above-mentioned example of FIG. 4, the maximum allowable displacement amount holding unit 2022 is provided in the encoder signal processing circuit 200. As described above, the maximum permissible displacement amount may differ depending on the encoder head used. Therefore, as shown in FIG. 7, the maximum permissible displacement amount holding portion 1023 may be provided inside the encoder head 102. .. In this way, the configuration of the encoder signal processing circuit 200 can be simplified.

Next, a modified example of the second embodiment will be described. FIG. 8 is a diagram showing a configuration of an encoder system including a signal processing circuit for an encoder according to a first modification of the second embodiment of the present invention. The first modification of this second embodiment is different from the second embodiment in that the processing determination unit 202 further includes the latest displacement information acquisition time holding unit 2025.

The latest displacement information acquisition time holding unit 2025 is a memory for holding the latest displacement information acquisition time for each encoder head. Here, the latest displacement information acquisition time is the latest allowable displacement information acquisition time for the drive control unit 300 to control the drive units 3a, 3b, and 3c, respectively. That is, if the encoder signal reading interval (that is, the displacement information calculation interval) exceeds the latest displacement information acquisition time, there is a risk that the control of the corresponding moving body will be hindered.

The operation of the encoder system in this modified example conforms to that described in FIG. However, in step S204 of FIG. 5, the latest readable time comparison unit 2024 compares the latest readable time for each encoder head with the latest displacement information acquisition time for each encoder head, and the time is earlier in this. The reading order of the encoder signals is determined in order. Of course, only the earliest time may be determined.

In the first modification of the second embodiment described above, the encoder signal reading order is determined in consideration of the latest displacement information acquisition time in addition to the latest readable time. As a result, not only the possibility that the displacement information is erroneous can be reduced, but also the possibility that the control of the drive control unit 300 is hindered can be reduced.

Here, in the example of FIG. 8, the maximum displacement information acquisition time holding unit 2025 is provided in the encoder signal processing circuit 200, but is provided in other than the encoder signal processing circuit 200, for example, in the drive control unit 300. You may do so.

Next, a second modification of the second embodiment will be described with reference to FIG. As for the configuration of the encoder system, the one shown in FIG. 4 can be applied. In the second embodiment described above, the reading order of the encoder signals is determined. On the other hand, in this modification, the reading interval is changed in addition to the reading order. Assuming that the speed of each moving body does not change, the encoder head that is first determined to have the earliest latest readable time is likely to be determined to have the earliest latest readable time thereafter. In consideration of this, in this modification, the read interval of the encoder signal from the encoder head having the earliest readable time is shortened, and the read interval of the encoder signal from the encoder head having the slowest readable time is lengthened. ..

For example, FIG. 9A is a timing chart when the latest readable time corresponding to the encoder heads 102a, 102b, 102c is the same and the encoder signals are read in the order of the encoder heads 102a, 102b, 102c. In this case, the read intervals of the encoder signals of the encoder heads 102a, 102b, and 102c are made equal. On the other hand, FIG. 9B is a timing chart when the latest readable time of the encoder head 102a is the earliest. In this case, the read interval of the encoder signal of the encoder head 102a is shortened as compared with the read interval of the encoder signals of the encoder heads 102b and 102c, respectively.

In the second modification of the second embodiment described above, the read interval of the encoder signal is changed according to the latest readable time. As a result, the latest readable time is calculated only once to determine the read interval, and thereafter, unless the speed of the moving body becomes faster than the speed at the time when the read interval is determined, the displacement information is incorrect. Can be reduced.

[Third Embodiment] Next, a third embodiment of the present invention will be described. FIG. 10 is a diagram showing a configuration of an encoder system including a signal processing circuit for an encoder according to a third embodiment of the present invention. The first and second embodiments described above change the content of the process relating to the reading of the encoder signal from the encoder head. On the other hand, in the third embodiment, the content of processing for the encoder signal read by the reading unit 2011 is changed. Therefore, in the third embodiment, as shown in FIG. 10, a processing content selection unit 2026 is provided. In addition, in FIG. 10, the read combination selection unit 2021 shown in the first embodiment, the maximum allowable displacement amount holding unit 2022 shown in the second embodiment, the latest readable time calculation unit 2023, and the latest readable time comparison. A part 2024 may be provided.

Hereinafter, only the parts different from the first embodiment will be described. The reading unit 2011 in the present embodiment reads the encoder signal from the encoder head in a predetermined order and outputs the encoder signal to the signal generation unit 2012 and the processing content selection unit 2026. The processing content selection unit 2026 generates a processing selection signal according to the encoder signal from the reading unit 2011 and inputs it to the signal generation unit 2012. The details of the processing content selection unit 2026 will be described later.

The operation of the encoder system in this embodiment will be described below. FIG. 11 is a flowchart showing the operation flow of the encoder system according to the third embodiment.

In FIG. 11, the drive control unit 300 supplies drive signals to each of the drive units 3a, 3b, and 3c to start the operation of the drive unit. At this time, the drive control unit 300 also turns on the power of the encoder head (step S301). After the operation of the drive unit and the encoder head is started, the read unit 2011 reads the encoder signal from any of the encoder heads 102a, 102b, and 102c in a predetermined order, converts the encoder signal into a digital signal, and digitally converts the encoder signal into a digital signal. The encoder signal converted into a signal is output to the signal generation unit 2012 and the processing content selection unit 2026 (step S302). The reading order of the encoder signals in step S302 is, for example, the order of the encoder heads 102a, 102b, 102c. The encoder signals from the respective encoder heads may be read out at the same time. In this case, each read encoder signal is held in the reading unit 2011.

Upon receiving the input of the encoder signal, the signal generation unit 2012 processes the input encoder signal and starts the calculation of the displacement information (step S303). At this time, the signal generation unit 2012 performs processing according to the processing selection signal from the processing content selection unit 2026. After step S303, processing proceeds to step S302.

FIG. 12 is a flowchart showing an example of processing of the encoder signal in the third embodiment. FIG. 12 shows an example in which signal processing is performed by giving priority to the encoder signal whose value has changed in the encoder signal read by the reading unit 2011. In FIG. 12, the processing content selection unit 2026 temporarily holds the encoder signal input from the reading unit 2011. After holding the encoder signal, the processing content selection unit 2026 previously holds the encoder signal value (actually, the AD conversion value corresponding to the amplitude) from the same encoder head as the encoder head that read the encoder signal. It is determined whether or not the value of the encoder signal read and held has changed by a predetermined value or more (step S401). In the determination in step S401, if the value of the encoder signal this time has changed by a predetermined value or more with respect to the value of the encoder signal of the previous time, the signal processing for the encoder signal is continued. In this case, the processing content selection unit 2026 inputs the processing selection signal for instructing the reading unit 2011 to perform signal processing (calculation of displacement information) on the encoder signal held this time to the signal generation unit 2012 ( Step S402).

After the start of the signal processing, the drive control unit 300 determines whether or not the signal processing is completed, that is, whether or not the displacement information has been input from the signal generation unit 2012 (step S403). The drive control unit 300 waits while performing the determination in step S403 until the signal processing is completed in the determination in step S403. Further, when the value of the encoder signal of this time does not change more than a predetermined value with respect to the value of the encoder signal of the previous time in the determination of step S401, or when the signal processing is completed in the determination of step S403, the processing of FIG. 12 And return to the process of FIG.

As described above, according to the present embodiment, the encoder signal whose value has changed is preferentially processed, so that the encoder signals from the plurality of encoder heads can be processed according to the operating situation of the encoder. It becomes possible to process efficiently.

Here, in the example of FIG. 12, among the encoder signals from the plurality of encoder heads, the encoder signal having a change in amplitude is preferentially processed. On the other hand, the encoder signal to be preferentially processed may be switched according to the fluctuation range of the amplitude of the encoder signal read from each encoder head from the previous time, that is, the change in the relative speed.

Further, even when the value of the encoder signal does not change more than a predetermined value, various signal processing may be performed at any time.

In the present embodiment, it is possible to change the detection accuracy by grasping the characteristics of each of the plurality of encoder heads from inside and outside. FIG. 13 is a flowchart showing a modification in the case of processing the encoder signal which is preferentially processed according to the change in the relative speed. The process of FIG. 13 is performed in place of the process of FIG. In FIG. 13, the processing content selection unit 2026 temporarily holds the encoder signal input from the reading unit 2011. After holding the encoder signal, the processing content selection unit 2026 calculates the time change of the amplitude (AD conversion value) of the encoder signal as the relative speed of the moving body (encoder head) (step S501). Subsequently, the processing content selection unit 2026 determines whether or not the calculated relative speed is faster than the predetermined speed (step S502). In the determination of step S502, for example, when the relative speed is faster than the predetermined speed and high accuracy (high resolution processing) is not required, the processing content selection unit 2026 moves faster than the predetermined speed. A processing selection signal is input to the signal generation unit 2012 so as to perform low-precision (low-resolution processing) signal processing on the encoder signal corresponding to the body (encoder head) (step S503). The low-precision signal processing here means, for example, the number of times of signal processing of the encoder signal from the encoder head determined to have a high relative displacement is compared with the number of times of signal processing of the encoder signal from another encoder head. And reduce it. On the other hand, in the determination of step S502, if high accuracy is required when the relative speed is not faster than the predetermined speed, the processing content selection unit 2026 performs high-precision signal processing on the encoder signal. The processing selection signal is input to the signal generator 2012 (step S504). In the high-precision signal processing here, for example, the number of times of signal processing of the encoder signal from the encoder head determined to have a low relative displacement is compared with the number of times of signal processing of the encoder signal from another encoder head. And increase it. In addition, here

After the start of the signal processing, the drive control unit 300 determines whether or not the signal processing is completed, that is, whether or not the displacement information has been input from the signal generation unit 2012 (step S505). The drive control unit 300 waits while performing the determination in step S505 until the signal processing is completed in the determination in step S505. When the signal processing is completed in the determination in step S505, the process of FIG. 13 is exited and the process returns to the process of FIG.

FIG. 14 is a flowchart showing the operation of another modified example when signal processing is performed according to a change in relative speed. The process of FIG. 14 is performed in place of the process of FIG. In FIG. 14, the drive control unit 300 supplies drive signals to each of the drive units 3a, 3b, and 3c to start the operation of the drive unit. At this time, the drive control unit 300 also turns on the power of the encoder head (step S601).

After the operation of the drive unit and the encoder head is started, the read unit 2011 reads the encoder signal from any of the encoder heads 102a, 102b, and 102c in a predetermined order, converts the encoder signal into a digital signal, and digitally converts the encoder signal into a digital signal. The encoder signal converted into a signal is output to the signal generation unit 2012 and the processing content selection unit 2026 (step S602). The processing content selection unit 2026 temporarily holds the encoder signal input from the reading unit 2011. After holding the encoder signal, the processing content selection unit 2026 calculates the relative speed of the moving body (encoder head) (step S603). Subsequently, the processing content selection unit 2026 determines the signal processing order by comparing the calculated relative speed with the calculated relative speed based on the encoder signals from the other encoder heads (step S604). In this processing, the signal processing is ranked in descending order of relative speed. After determining the signal processing order, the processing content selection unit 2026 inputs a processing selection signal to the signal generation unit 2012 so as to perform signal processing according to the signal processing order. The signal generation unit 2012 performs signal processing (calculation of displacement information) on the encoder signal according to the input signal processing order (step S605).

By preferentially processing the encoder signal from the encoder head having a large relative displacement as shown in the above-described modification, the efficiency of signal processing by the single encoder signal signal processing circuit 200 is improved. At the same time, it is possible to improve the accuracy of the displacement information.

Here, if the processing priority of the encoder signal is set in advance, the processing order and the number of processings of the encoder signal may be determined according to the priority. FIG. 15 is a diagram showing such a modified example. The example of FIG. 15 shows an example in which two encoder signals A and B are simultaneously processed and the encoder signal A has a higher priority than the encoder signal B. In the example of FIG. 15, the priority and the number of times the encoder signal is processed are associated with each other, and the signal processing of each encoder signal is performed by the number of times of processing associated with the priority. For example, the example of FIG. 15 shows an example in which the ratio of the number of times the encoder signal A and the encoder signal B are processed is 2: 1.

Here, when the priority is determined in advance and an encoder signal having a higher priority than the encoder signal is input during processing of a certain encoder signal, the processing of the current encoder signal is temporarily interrupted. It is desirable to perform processing on the high-priority encoder signal. In this case, after the processing for the high-priority encoder signal is completed, the processing of the encoder signal whose processing has been interrupted is restarted.

Although the present invention has been described above based on the embodiments, the present invention is not limited to the above-described embodiments, and it goes without saying that various modifications and applications are possible within the scope of the gist of the present invention. For example, the user may be able to manually set the combination of the encoder heads and the setting of the signal processing content shown in the first to third embodiments described above. A modified example in this case is shown in FIG. In FIG. 16, a processing determination signal input unit 500 is provided. By operating the processing determination signal input unit 500, the user can instruct the processing determination unit 202 of the setting contents of the combination of the encoder heads and the setting contents of the signal processing contents.

Further, for example, if the processing determination unit 202 is provided with a processing content information holding unit that holds information on the encoder head to be used, information on the priority of signal processing, and the like, the power of the encoder signal processing circuit 200 is turned on. It is also possible to set the combination of encoder heads and the signal processing contents at the time of initial setting immediately after.

Further, the above-described embodiments include inventions at various stages, and various inventions can be extracted by an appropriate combination of a plurality of disclosed constituent requirements. For example, even if some constituent requirements are deleted from all the constituent requirements shown in the embodiment, if the above-mentioned problems can be solved and the above-mentioned effects can be obtained, this constituent requirement is deleted. The configuration can also be extracted as an invention.

1a, 1b, 1c ... Fixed part, 2a, 2b, 2c ... Moving part, 3a, 3b, 3c ... Drive part, 101a, 101b, 101c ... Scale, 102a, 102b, 102c .. .Encoder head, 200 ... encoder signal processing circuit, 201 ... processing unit, 202 ... processing decision unit, 2011 ... reading unit, 2012 ... signal generation unit, 2013 ... warning signal Control unit, 2021 ... Read combination selection unit, 2022 ... Maximum allowable displacement amount holding unit, 2023 ... Late readable time calculation unit, 2024 ... Latest readable time comparison unit, 2025 .. .Latest displacement information acquisition time holding unit, 2026 ... processing content selection unit, 300 ... drive control unit, 400 ... warning unit, 500 ... processing decision signal input unit