JP2010039739A - Safe plc (programmable logic controller) - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To enhance safety to the operation of a control target. <P>SOLUTION: This safe PLC (programmable logic controller) is provided with a module 3 configured to operate a control target in response to control from a PLC body 1 which performs sequence control, and to operate after receiving the supply of a power source. The module 3 is provided with a detection part 3e for detecting the state of a power source; and a control part 3a for, when it is detected that the power source is abnormal by the detection part 3e, operating the control target to a safety side by its own operation independently of sequence control by the PLC body 1, and for informing the PLC body of the operating state. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention provides a safety PLC capable of ensuring the safety of the control operation of the above-mentioned devices when performing sequence control on the basis of signals input to a PLC (programmable controller) of various machines / devices and their peripheral devices. It is about.

  The PLC is generally used in factory automation (FA) or the like. For example, the PLC is input with ON / OFF signals from various input devices such as switches and sensors, and written in a ladder language from the input signals. A logical operation is executed in accordance with the ladder program, and various output devices such as a relay and a motor are controlled to be turned ON / OFF according to the operation result.

  In contrast to such a general PLC, a safety PLC can be used to stop various devices to be controlled by using input signals from safety-compatible input devices such as an emergency stop button or a signal line disconnection detector, It is a fail-safe PLC that controls various devices to the safe side, such as operating, and is specialized for safety. For example, if the CPU and other processing units are duplicated to output correctly, for example, when an emergency stop switch is pressed or a sensor such as a light curtain detects the entry of a person, fail-safe There is one in which (safety) is activated, the system is on the safe side, and the operation is stopped (see Patent Document 1).

  In such a safety PLC, as schematically shown in FIG. 4, a PLC main body 1 having a CPU for executing sequence control and a bus connection to the PLC main body 1 in response to a control command from the PLC main body 1 Some include one or more I / O modules 3 that operate or control the control target 5. In this safety PLC, the PLC main body 1 has a function of detecting a power supply abnormality and a function of supplying power to the I / O module 3. If the power supply is abnormal, the PLC main body 1 stops the sequence control to the safe side.

However, when the power supply abnormality detection function is deteriorated due to a circuit abnormality in the PLC main body 1, the sequence control is not stopped, and the power supply voltage is supplied to the I / O module 3 by lowering the normal value, for example. In some cases, the I / O module 3 malfunctions. Further, since the PLC main body 1 cannot determine the malfunction of the I / O module 3 due to a circuit abnormality or the like, the sequence control is performed with the I / O data from the I / O module 3, and its safety. May decrease.
JP 2002-358106 A

  Therefore, the problem to be solved by the present invention is that the module itself has a power supply abnormality detection function, and when a power supply abnormality is detected, the control body is controlled independently from the PLC main body, and the control by the PLC is performed. It is to increase the control safety of the object.

  The safety PLC of the present invention has a power supply abnormality detection function. When a power supply abnormality is detected by this function, the PLC main body stops sequence control, and operates a control target in response to a control command from the PLC main body. In a safety PLC comprising one or more modules that operate in response to the supply of power, a detection unit that detects a state of power supply to the module, and a detection unit that detects the state of the power supply to the module. When the power supply is abnormal, there is provided a control unit that is independent of the sequence control and operates the control target to the safe side by the operation by itself and communicates the operation state to the PLC main body. Is.

  In the above case, the module may be supplied with power from the PLC main body, or may be supplied with power from other than the PLC main body.

  The module includes various modules such as an I / O module, a communication module, a communication module, a control module, a functional module, and a motion module.

  Explaining the present invention, the PLC main body side can stop the sequence control when the power supply is abnormal, but the sequence control cannot be stopped when the power supply abnormality cannot be detected due to an internal circuit abnormality or the like. There is. In such a case, on the module side, the detection unit can detect the abnormality of the power supply to itself, so that the voltage of the power supply to the module is abnormally shaken by the PLC main body due to an internal circuit abnormality or the like. Even if the sequence control cannot be stopped in such a case, an abnormality in the power supply to itself can be detected and the control target can be operated on the safe side independently from the sequence control by the PLC main body. Control over the object can be performed safely. On the other hand, since the operation is communicated to the PLC main body, the PLC main body can safely control the sequence control after the power supply returns to normal.

  The control target is not particularly limited. For example, the present invention is not limited to various switches, sensors, motors, actuators, relays, and the like.

  According to the present invention, the I / O module itself has a power supply abnormality detection function, and when a power supply abnormality is detected, the control object can be controlled independently and controlled to the safe side. It is possible to increase the safety of control of the controlled object.

  Hereinafter, a safety PLC according to an embodiment of the present invention will be described with reference to the accompanying drawings. 1 shows a schematic configuration of the safety PLC according to the embodiment, FIG. 2 shows a block configuration of the PLC main body, and FIG. 3 shows a block configuration of each module. Referring to these drawings, 1 indicates a PLC main body, 3 indicates an I / O module, and 5 indicates a control target.

  The PLC main body 1 includes a CPU 1 a that executes a sequence program, various memories 1 b that are necessary for the execution of the sequence program, and an interface 1 c with the module bus 7, and a power source that supplies power to each part in the PLC main body 1. Unit 1d and a power supply abnormality detection unit 1e that detects abnormality of the supplied power. The interface 1c can be configured with an FPGA. As an example of a programmable logic device, an FPGA is an abbreviation of a field programmable gate array that allows a user to arbitrarily design logic. For example, the XC series of XILINX, Inc., USA, for example, a circuit configuration stored in a configuration data memory Are read and configured in a desired circuit configuration. Although illustration of the specific structure of the power supply abnormality detection part 1e is abbreviate | omitted, it can be normally comprised with a well-known thing. For example, the power supply abnormality detection unit 1e applies a reference voltage to one of two input units of a comparator as a voltage comparison unit and a power supply voltage to the other, and outputs a power supply abnormality detection output when the power supply voltage is equal to or lower than the reference voltage. It may operate as follows.

  When the power supply abnormality detection unit 1e detects that the power supplied to the PLC main body 1 is abnormal, the PLC main body 1 stops the sequence control. For this stop, for example, a program command is issued so that the controlled object 5 controlled by the I / O module 3 is controlled to the safe side, or necessary data is stored, and then the sequence control is stopped. Is preferred.

  On the other hand, the PLC main body 1 cannot detect that the power supply voltage of the power supply unit 1d is abnormally low when the internal circuit is abnormal, for example, when the power supply abnormality detection unit 1e has an abnormality in the detection operation. The sequence control may continue.

  Therefore, in the present embodiment, when the I / O module 3 has a power supply abnormality, the control object 5 can be controlled to the safe side by itself independently from the sequence control of the PLC body 1.

  In the following, the I / O module 3 includes a CPU 3a that executes a control command from the PLC main body 1, a memory 3b that is used to store state data of the control target 5 that accompanies the execution of the control command, and a module bus 7 Interface 3c and a power supply unit 3d for supplying power to the internal components, and a power supply abnormality detection unit 3e for detecting an abnormality of the supplied power supply. The power supply unit 3d may not be provided, and power may be supplied from the PLC main body 1 or another module. This interface 3c can also be constituted by FPGA. This embodiment is characterized in that a power supply abnormality detection unit 3e is provided and that, in addition to the PLC main body 1, a CPU 3a is incorporated as a control unit that responds to the detection output of the power supply abnormality detection unit 3e.

  In the I / O module 3, the power supply abnormality detection unit 3e monitors whether or not the power supply to the I / O module 3 is abnormal. If there is, the detection output is input to the CPU 3a. When there is an abnormality such as a voltage drop in the power supply, the CPU 3a controls the controlled object 5 to the safe side independently from the sequence control by the PLC main body 1 and gives priority to the PLC main body 1 during the sequence control. To be able to contact you. The PLC main body 1 stops the sequence control by knowing that there is an abnormality in the power supply of the I / O module 3 and that the control target 5 is controlled to the safe side by the above communication from the I / O module 3. Or other necessary program control. Since each of the I / O modules 3 includes the CPU 3a and the power supply abnormality detection unit 3e, each I / O module 3 individually copes with the power supply abnormality and has the configuration shown in FIG. As indicated by the broken line arrow, the above operation due to power failure is notified.

  As described above, in the present embodiment, when there is a power failure in the I / O module 3, the I / O module 3 itself operates the control target 5 to the safe side independently from the sequence control by the PLC body 1. can do.

FIG. 1 is a diagram showing a schematic configuration of a safety PLC according to an embodiment of the present invention. FIG. 2 is a diagram showing an internal block configuration of the PLC main body. FIG. 3 is a diagram showing an internal block configuration of the I / O module. FIG. 4 is a diagram showing a schematic configuration of a safety PLC according to a conventional example.

Explanation of symbols

1 PLC body 3 I / O module 3a CPU (control unit)
3e Power failure detection unit

Claims (2)

A PLC main body that has a power supply abnormality detection function and stops the sequence control when a power supply abnormality is detected by this function;
One or a plurality of modules that operate in response to a control command from the PLC main body and operate by receiving power supply;
In the safety PLC with
A detection unit for detecting the state of power supply to the module in the module, and when the power supply to the module is abnormal due to detection by the detection unit, the sequence control is independent and controlled by an operation by itself. A safety PLC provided with a control unit for operating the target to the safety side and communicating the operation state to the PLC main body.   The safety PLC according to claim 1, wherein the module is supplied with power from the PLC main body, and the detection unit detects a state of power supplied from the PLC main body.

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