JP2007228462A - Slave unit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To continuously carry out control operation of a slave unit even when communication data are omitted. <P>SOLUTION: A slave unit comprises: a timer 11 which is cleared by a communication timing signal 5, a comparison value setting means 12, a comparator 13 which outputs a matching signal 14, and an initiation signal generating means 15 for outputting a slave control initiation signal 16 when the communication timing signal 5 or the matching signal 14 is inputted. When the communication timing signal 5 is inputted, a timer value corresponding to the time adding a timing margin Tm to one communication cycle is set as a comparison value 12a and when the matching signal 14 is inputted, a value adding a timer value corresponding to one communication cycle to the present comparison value 12a is set as a new comparison value 12a. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a slave device that performs control in synchronization with a communication cycle in a control system that transmits commands from a master device to a slave device by cyclic communication.

  In recent years, communication has been widely used for information transmission between devices of a control system for the purpose of higher functionality and reduced wiring. FIG. 6 is a block diagram showing this. The master device M and the slave device S are connected by a communication line L, and a command transmitted from the master device M is transmitted to the slave device S via the communication line L. The apparatus S is configured to be controlled. Normally, a plurality of slave devices S are normally connected to one master device M. However, for ease of explanation, an example in which one slave device S is schematically shown in FIG. Show.

  In general, a communication abnormality may occur due to noise or the like in communication, but at this time, not only data may be garbled but also data in that cycle may be lost due to circumstances. Depending on the application, this missing communication data may not be a problem, but it is often a problem when performing cyclic communication for the purpose of real-time control.

  For example, in the case of performing motion control such as servo control, the operation becomes unstable if the control calculation of the slave device in the cycle in which the communication data dropout occurs is stopped. Therefore, it is important that the control calculation can be continuously executed even in a cycle in which communication data is lost. If the control calculation is executed when simply received, the control calculation of the cycle in which the communication data is lost is lost. Therefore, as a solution, for example, control as shown in Patent Document 1 has been performed. .

  FIG. 7 is a block diagram showing this control configuration, which is configured inside the slave device S. In FIG. 7, the timer 1 operates in a cycle based on the timer cycle command 2. The start signal generating means 3 generates a pulse signal synchronized with the period of the timer 1 using the output value of the timer 1 and outputs it as a slave control start signal 4.

  The control calculation is periodically started by the slave control activation signal 4, and the operation command data from the master device M is reflected in the control during the calculation process. The communication timing signal 5 is a pulse signal serving as a timing reference synchronized with the communication cycle. For example, a communication frame reception completion signal is used for this.

  The communication timing signal 5 and the slave control activation signal 4 are input to the delay time detecting means 6, and the delay time 7 of the slave control activation signal 4 with respect to the communication timing signal 5 is measured and output. The result obtained by multiplying the difference between the reference delay time 8 and the delay time 7 by the control gain 9 and adding the reference timer period 10 is the timer period command 2. Note that a value corresponding to the communication cycle is preset in the reference timer cycle 10.

  In this configuration, when the delay time 7 of the slave activation signal 4 based on the communication timing signal 5 is shorter than the reference delay time 8, the output value of the control gain 9 becomes positive, so that the timer 1 has a reference timer period 10 That is, it operates at a cycle longer than the communication cycle. As a result, the period of the slave control activation signal 4 also becomes longer than the communication period, so that the delay time 7 approaches the reference delay time 8.

  As a result, when the delay time 7 eventually coincides with the reference delay time 8, the output value of the control gain 9 becomes zero, so that the timer 1 operates in the reference timer period 10, that is, the communication period, and is stabilized here. . On the other hand, when the delay time 7 is longer than the reference delay time 8, the output value of the control gain 9 becomes negative, so that the timer 1 operates at a cycle shorter than the communication cycle. As a result, the cycle of the slave control activation signal 4 also becomes shorter than the communication cycle, so that the delay time 7 approaches the reference delay time 8, and the delay time 7 eventually coincides with the reference delay time 8.

  As described above, the operation of the closed loop control always operates so that the delay time 7 coincides with the reference delay time 8. As a result, the slave control activation signal 4 is synchronized with the communication timing signal 5. In particular, when the reference delay time 8 is set to zero, the delay time 7 is controlled to be zero, so the timing of the communication timing signal 5 and the slave control activation signal 4 coincide.

Here, when communication data is lost, the communication timing signal 5 of that cycle is also lost, but the slave control activation signal 4 is generated based on the timer 1 instead of this communication timing signal 5, so in this case However, the control calculation can be executed continuously. If the communication data is lost in the control calculation that is continuously executed without stopping, the operation of the timer 1 can be performed by stopping the closed-loop control process and holding the timer cycle command 2. There is no instability.
JP 2003-189654 A

  However, since such a conventional slave device performs closed loop control, appropriate adjustment of the control gain 9 is indispensable, and there is a problem that the work of performing this gain adjustment is troublesome.

  To determine the stability of closed-loop control during gain adjustment, it is common to observe a time-axis convergent waveform such as a step response, but slave device control is often configured by software. Therefore, it is necessary to devise in order to observe the signal waveform of each part.

  For example, a D / A converter is mounted and observed with an oscilloscope, or data of each part is stored in a memory in time series and later read out and displayed on a personal computer. The method is also troublesome.

  The present invention solves such a conventional problem, and an object of the present invention is to provide a slave device capable of continuously executing a control operation even when communication data is lost without using closed loop control.

  In order to solve the above problems, the present invention provides a timer that is cleared by a communication timing signal, a comparison value setting means for setting a comparison value, and a match signal when the timer value and the comparison value are compared and the values match. And a start signal generating means for outputting a slave control start signal when a communication timing signal or a coincidence signal is input, and the comparison value setting means is configured to communicate 1 when a communication timing signal is input. A timer value corresponding to the time obtained by adding the timing margin to the period is set as a comparison value. When a coincidence signal is input, a value obtained by adding the timer value corresponding to one communication period to the current comparison value is newly set. Further, the timing margin is configured as a value larger than the maximum fluctuation width of the communication cycle.

According to the slave device of the present invention, since it is not a closed loop control configuration as in the conventional example, troublesome adjustment of the control gain is unnecessary. Basically, the slave device control calculation is started by the communication timing signal, but if the communication timing signal is not obtained, the slave device control calculation is started by the coincidence signal, so communication data loss occurs. In this case, the slave device can continue to be controlled.

  In addition, when the comparison value exceeds the preset upper limit value, the timeout abnormality process is executed, so that it is not necessary to provide a separate timeout detection process that is indispensable in the communication device, and the slave The configuration of the apparatus can be simplified.

  The present invention includes a timer that is cleared by a communication timing signal, a comparison value setting means that sets a comparison value, a comparator that compares the timer value and the comparison value and outputs a match signal when both values match, And a start signal generating means for outputting a slave control start signal when a communication timing signal or a coincidence signal is input, and the comparison value setting means adds a timing margin to one communication cycle when the communication timing signal is input. Set a timer value corresponding to the specified time as a comparison value, and when a coincidence signal is input, set a value obtained by adding a timer value corresponding to one communication cycle to the current comparison value as a new comparison value, Further, the timing margin is set to a value larger than the maximum fluctuation range of the communication cycle.

  Further, when the comparison value is equal to or greater than a preset upper limit value, a timeout abnormality process is executed.

  Embodiments of the present invention will be described below with reference to the drawings.

  FIG. 1 is a block diagram illustrating a control configuration of the first embodiment. The communication timing signal 5 is connected so as to clear the timer 11, and is further connected to the comparison value setting means 12 in order to set the comparison value 12a at this timing.

  The communication timing signal 5 is the same as that used in the description of the conventional example shown in FIG.

  The timer value 11a and the comparison value 12a are compared by the comparator 13, and a coincidence signal 14 is output when the two values coincide. The coincidence signal 14 and the communication timing signal 5 are input to the activation signal generation means 15, and the logical sum of both signals is output as the slave control activation signal 16. And it is comprised so that the control calculation of a slave apparatus may be started with this signal.

  Further, the coincidence signal 14 is also input to the comparison value setting means 12, and therefore the comparison value setting means 12 outputs the comparison value 12a at two kinds of timings, that is, when the communication timing signal 5 is inputted and when the coincidence signal 14 is inputted. Set.

  FIG. 2 is a flowchart showing the operation of the comparison value setting means 12. When the input signal is the communication timing signal 5, the comparison value 12a is set to C1, and when the input signal is the coincidence signal 14, the current comparison value 12a plus KTc is used as the new comparison value 12a. Set as.

  Here, C1 and KTc are based on the following formula, where Tc is a communication period, Tm is a timing margin, and K is a coefficient for converting time into a timer value. Therefore, C1 represents a timer value corresponding to the time obtained by adding the timing margin Tm to the communication cycle Tc, and KTc represents a timer value corresponding to the communication cycle Tc.

  Therefore, the operation of setting a value obtained by adding KTc to the current comparison value 12a as a new comparison value 12a is sequentially increased to C2 if the current comparison value 12a is C1, and to C3 if the current comparison value 12a is C2. It is equivalent to going. Although only C4 is shown as an example in Equation 1, the same calculation is performed when the number is further increased.

  FIG. 3 is a time chart showing the overall operation. Since the communication frame 17 is normally received from the timing t1 to the timing t3, the communication timing signal 5 is output, and the control calculation of the slave device is started by this signal. At the same time, since the timer value 11a is cleared by this signal, the timer value 11a does not become the comparison value 12a or more during the period from t1 to t3. Next, at the timing of t4, since the communication frame 17 has been lost, the communication timing signal 5 is not output.

  Therefore, the timer value 11a increases without being cleared, and coincides with the comparison value 12a when the timing margin Tm elapses, and the coincidence signal 14 is output. Since the control operation of the slave device is activated by this signal, control can be continued even if communication data is lost.

  At this time, the comparison value 12a changes from C1 to C2 (part a) to prepare for the next comparison. Since the communication frame is normally received again at the next timing t5, the communication timing signal 5 is output.

  As a result, the comparison value 12a changes from C2 to C1 (part b) and returns to the initial state. Although not specifically shown, the timer 11 is in a stopped state when the power is turned on, and the timer 11 starts operating from the time when the first communication frame 17 is received after that, that is, from the time when the first communication timing signal 5 is output. It is configured to do.

  In this way, an unintended coincidence signal 14 is prevented from being output during a period in which the communication frame 17 after power-on is not received.

  The period for receiving the communication frame 17 is not always constant, and actually varies slightly, so it is necessary to set the timing margin Tm so as not to cause a problem due to this.

  Note that the fluctuation referred to here is not an error in the communication cycle Tc itself, but means fluctuation during operation, that is, jitter, which is particularly large when a relay device is arranged in the communication path. is there.

  FIG. 4 shows the fluctuation of the cycle of the communication timing signal 5, where the upper side is when the communication cycle is the reference value Tc, and the lower side is when the maximum value Tcmax is reached.

  The timing margin Tm is set to be larger than the maximum fluctuation range Tdmax that is the result of subtracting Tc from Tcmax. Thereby, when reception of the communication frame 17 is delayed due to fluctuation, it is possible to avoid a problem that the coincidence signal 14 is erroneously output.

  When the control operation of the slave device is activated by the coincidence signal 14, the activation of the control operation is delayed by the time of the timing margin Tm as compared with the case of activation by the communication timing signal 5, but generally the timing margin Tm Since this is a sufficiently short time with respect to the communication cycle Tc, this delay hardly affects the control.

  As described above, according to the configuration of the first embodiment, the communication timing signal 5 is output when the communication frame 17 is normally received, and the coincidence signal 14 is output when communication data is lost. Thus, the control calculation of the slave device can be continuously started without interruption using these signals.

  In addition, since the component does not have the control gain existing in the conventional example, troublesome gain adjustment is unnecessary. In addition, since the timer 11 and the comparator 13 of this component are often built in a general control CPU, no special hardware is required.

  In order to start the control operation of the slave device by the communication timing signal 5 or the coincidence signal 14, it is only necessary to individually interrupt and execute the control operation in each interrupt processing, and then the start signal generating means 15 Even no special hardware is required.

  Furthermore, since the comparator setting means 12 can be configured by software, after all, the necessary components are only the CPU, which can be realized at low cost.

  In order to simplify the explanation, the control operation of the slave device is activated at the same timing as the communication timing signal 5, but a delay means is provided at the subsequent stage of the communication timing signal 5 or the slave control activation signal 16 that is the output. It may be interposed. By so doing, an arbitrary delay time can be provided between the output of the communication timing signal 5 and the slave control activation as in the conventional example, and the degree of freedom of application is increased.

  In addition, when the control calculation is activated by the coincidence signal 14 by an interrupt, the timer 11 is operated immediately after the power is turned on if the interrupt is permitted when the first communication timing signal 5 is output after the power is turned on. There is no problem even if you let it. This method is effective when the timer 11 cannot be started and stopped freely.

  Furthermore, it is needless to say that the comparator 13 may detect that the timer value 11a is not equal but the timer value 11a is equal to or greater than the comparison value 12a, and this change timing may be used in place of the coincidence signal 14. .

  In a control system using communication, when a disconnection or the like occurs, it is necessary to reliably detect this and stop the slave device safely. This is generally performed by detecting a timeout. In the second embodiment, this time-out detection function is added.

FIG. 5 is a flowchart showing the operation of the comparison value setting means 12 in the second embodiment. In FIG. 5, a portion surrounded by a dotted line is a portion added from FIG. 2 used in the description of the first embodiment.
When the input signal is the coincidence signal 14, it is determined whether or not the current comparison value 12a is greater than or equal to a preset upper limit value. Execute the process. Otherwise, the process shown in the first embodiment is performed.

  In FIG. 3 used for the description of the first embodiment, the operation of the present embodiment is shown at timings after t7. Here, the upper limit value of the comparison value 12a is set in advance to C4. Since the communication frame 17 is not received after the timing t7, the coincidence signal 14 is output so as to supplement the communication timing signal 5 as described above, and the comparison value 12a is C1 to C2 (part c), and C2 to C3. (D part) and increase in order from C3 to C4 (e part).

  Since the communication frame 17 is not received at the timing t10, the coincidence signal 14 is output as before. However, since the comparison value 12a is the upper limit C4, the comparison value is increased further. First, the timer 11 is stopped (part f) and timeout abnormality processing is executed. This figure shows an example in which the timeout detection signal 18 is changed from L to H as part of timeout abnormality processing.

  With the above operation, the timeout detection time becomes a time corresponding to the preset upper limit value C4.

  According to this configuration, the timer 11 that generates the output timing of the coincidence signal 14 is used not only for realizing the time-out detection function but also for time-out detection. Therefore, an independent timer dedicated to time-out detection is used. There is an advantage that it is not necessary to provide.

  Further, since the portion added to the first embodiment, that is, the portion surrounded by the dotted line in FIG. 5 can be configured by software, it can be realized at the same cost as the first embodiment.

  Note that when the control calculation is activated by the coincidence signal 14 by an interrupt, the interrupt may be prohibited instead of the process of stopping the timer 11 when a timeout is detected.

Control block diagram in Embodiment 1 of the present invention The flowchart of the comparison value setting means 12 in Example 1 of this invention. The time chart which shows the operation | movement in Example 1 and Example 2 of this invention Explanatory drawing of timing margin Tm in Example 1 of this invention The flowchart of the comparison value setting means 12 in Example 2 of this invention. Schematic diagram of a control system using communication Control block diagram in the conventional example

Explanation of symbols

5 Communication timing signal 11 Timer 12 Comparison value setting means 13 Comparator 14 Match signal 15 Start signal generation means 16 Slave control start signal

Claims (2)

A timer that is cleared by a communication timing signal, a comparison value setting means for setting a comparison value, a comparator that compares the timer value and the comparison value and outputs a coincidence signal, and a communication timing signal or An activation signal generating means for outputting a slave control activation signal when a coincidence signal is input, and the comparison value setting means corresponds to a time obtained by adding a timing margin to one communication period when a communication timing signal is input The timer value to be set is set as a comparison value, and when a coincidence signal is input, a value obtained by adding the timer value corresponding to one communication cycle to the current comparison value is set as a new comparison value. A slave device characterized in that the margin is a value larger than the maximum fluctuation range of the communication cycle. 2. The slave device according to claim 1, wherein timeout abnormality processing is executed when the comparison value is equal to or greater than a preset upper limit value.

Images