1
FORM 2
THE PATENTS ACT, 1970
(39 of 1970)
&
THE PATENTS RULES, 2003
COMPLETE SPECIFICATION
[See section 10, Rule 13]
EXPANSION BASE UNIT, CONTROL DEVICE, CONTROL SYSTEM, AND
CONTROL METHOD;
MITSUBISHI ELECTRIC CORPORATION, A CORPORATION ORGANISED AND
EXISTING UNDER THE LAWS OF JAPAN, WHOSE ADDRESS IS 7-3,
MARUNOUCHI 2-CHOME, CHIYODA-KU, TOKYO 100-8310, JAPAN
THE FOLLOWING SPECIFICATION PARTICULARLY DESCRIBES THE
INVENTION AND THE MANNER IN WHICH IT IS TO BE PERFORMED.
2
DESCRIPTION
EXPANSION BASE UNIT, CONTROL DEVICE, CONTROL SYSTEM, AND
CONTROL METHOD
5
Technical Field
[0001] The present disclosure relates to an expansion base unit, a control device, a
control system, and a control method.
Background Art
10 [0002] Known techniques for achieving central processing unit (CPU) module
multi-redundancy improve the reliability of programmable logic controllers (PLCs).
For example, Patent Literature 1 describes a technique for providing dual-redundancy
using two CPU modules each connected with a common tracking cable to identify the
state of the other CPU module, and an expansion base unit for CPU dual-redundancy
15 connectable to two main base units each connected with the corresponding CPU module.
Citation List
Patent Literature
[0003] Patent Literature 1: Unexamined Japanese Patent Application Publication
No. 2007-164722
20 Summary of Invention
Technical Problem
[0004] The expansion base unit may be connected with an additional expansion
base unit. In an example described in Patent Literature 1, an additional expansion base
unit is installed subsequent to the expansion base unit for CPU dual-redundancy, and the
25 expansion base unit for CPU dual-redundancy and the additional expansion base unit are
connected to each other using a single cable. For example, when the expansion base
unit for CPU dual-redundancy cannot receive a sufficient number of input/output (I/O)
3
modules, an additional expansion base unit is to be installed.
[0005] The terms "previous" and "subsequent" are used in relation to the main base
unit. In the example in Patent Literature 1, the expansion base unit for CPU dualredundancy
is "subsequent" to the main base unit and "previous" to the additional
expansion 5 base unit.
[0006] In Patent Literature 1, the expansion base unit for CPU dual-redundancy and
the additional expansion base unit are connected using a single cable. In this
architecture, when an abnormality such as a break or deterioration occurs in the cable, an
abnormality occurs in communication between the CPU modules and components
10 connected to the additional expansion base unit. Thus, the technique described in Patent
Literature 1 may be insufficient in providing the reliability of PLCs.
[0007] In response to the above issue, an objective of the present disclosure is to
provide an expansion base unit connectable to another expansion base unit with multiredundant
cables.
15 Solution to Problem
[0008] To achieve the above objective, an expansion base unit according to an
aspect of the present disclosure includes an input connector communicatively connectable
with a cable to a connector in a previous base unit to allow receipt of a signal from the
previous base unit, and a plurality of output connectors that each are communicatively
20 connectable with a cable to a connector of a plurality of connectors in a subsequent
expansion base unit to allow transmission of the signal received by the input connector to
the subsequent expansion base unit.
Advantageous Effects of Invention
[0009] The expansion base unit according to the above aspect of the present
25 disclosure is connectable to another expansion base unit with multi-redundant cables.
Brief Description of Drawings
[0010] FIG. 1 illustrates configuration of a control system according to
4
Embodiment 1 of the present disclosure;
FIG. 2 illustrates configuration of an expansion base unit according to
Embodiment 1 of the present disclosure;
FIG. 3 illustrates configuration of a main base unit according to Embodiment 1 of
the present 5 disclosure;
FIG. 4 illustrates configuration of a CPU module in Embodiment 1 of the present
disclosure;
FIG. 5 illustrates an example of hardware configuration of the expansion base unit
according to Embodiment 1 of the present disclosure;
10 FIG. 6 is a flowchart of an example operation of input switching performed by the
expansion base unit according to Embodiment 1 of the present disclosure;
FIG. 7 is a flowchart of an example operation of output switching performed by
the expansion base unit according to Embodiment 1 of the present disclosure;
FIG. 8 is a flowchart of an example operation of switch control performed by the
15 CPU module in Embodiment 1 of the present disclosure;
FIG. 9 illustrates configuration of an expansion base unit according to a
modification of Embodiment 1 of the present disclosure;
FIG. 10 illustrates configuration of an expansion base unit according to
Embodiment 2 of the present disclosure;
20 FIG. 11 illustrates configuration of an expansion base unit according to
Embodiment 3 of the present disclosure; and
FIG. 12 illustrates an example of a transfer destination table stored in a storage in
the expansion base unit according to Embodiment 3 of the present disclosure.
Description of Embodiments
25 [0011] A control system according to one or more embodiments of the present
disclosure is described with reference to the drawings. The same reference signs denote
the same or like components in the drawings.
5
[0012] Embodiment 1
A control system 1000 according to Embodiment 1 is described with reference to
FIG. 1. The control system 1000 acquires, for example, a sensor value from a sensor
and controls a machine tool based on the sensor value. The control system 1000
includes a control device 1a, a control device 1b, a control device 2a, and 5 a control device
2b. The control device 2a and the control device 2b are communicatively connected to
each other with a tracking cable TC. The control device 2a and the control device 1a are
communicatively connected to each other with a bus connection cable C11. Similarly,
the control device 2b and the control device 1a are communicatively connected to each
10 other with a bus connection cable C12. The control device 1a and the control device 1b
are communicatively connected to each other with a bus connection cable C21 and a bus
connection cable C22. Similarly, the control device 1b and another non-illustrated
control device are communicatively connected to each other with a bus connection cable
C31 and a bus connection cable C32. The other non-illustrated control device may be
15 communicatively connected to still another control device with bus connection cables.
The control system 1000 is an example of a control system in an aspect of the present
disclosure. The bus connection cables C are examples of cables in an aspect of the
present disclosure.
[0013] For simplicity, the control device 1a and the control device 1b may hereafter
20 be collectively referred to as control devices 1. Similarly, the control device 2a and the
control device 2b may hereafter be collectively referred to as control devices 2. The
same applies to the other components described later.
[0014] In the control system 1000, the control device 2a and the control device 2b
provide the dual-redundancy of the control devices 2. In the control system 1000, the
25 bus connection cable C21 and the bus connection cable C22 provide the dual-redundancy
of the bus connection cables that connect the control device 1a and the control device 1b.
In the control system 1000, the control devices 1 are connected in a row to the control
6
devices 2.
[0015] Each control device 1 includes an expansion base unit 10, an I/O module 11,
and a power supply 12. The I/O module 11 and the power supply 12 are connected to
non-illustrated slots in the expansion base unit 10. The I/O module 11 is
communicatively connected to a non-illustrated sensor and a non-5 illustrated machine
tool. The power supply 12 powers the expansion base unit 10 and the I/O module 11.
The expansion base unit 10 communicates with the components connected to the nonillustrated
slots and also communicates with other base units connected with the bus
connection cables. These components included in the control device 1 enable the
10 control devices 2 to communicate with the control device 1 and control the sensor and the
machine tool connected to the I/O module 11. The control device 1 may include
multiple I/O modules 11 or multiple power supplies 12. The control device 1 is an
example of a control device in an aspect of the present disclosure. The I/O module 11 is
an example of an input-output module in an aspect of the present disclosure. The sensor
15 and the machine tool are examples of external devices in an aspect of the present
disclosure.
[0016] Each expansion base unit 10 includes an input connector 101, an input
connector 102, an output connector 111, and an output connector 112. In FIG. 1, the
bus connection cable C11 is connected to an input connector 101a, the bus connection
20 cable C12 is connected to an input connector 102a, the bus connection cable C21 is
connected to an output connector 111a, and the bus connection cable C22 is connected to
an output connector 112a. Similarly, the bus connection cable C21 is connected to an
input connector 101b, the bus connection cable C22 is connected to an input connector
102b, the bus connection cable C31 is connected to an output connector 111b, and the
25 bus connection cable C32 is connected to an output connector 112b. In other words, the
expansion base units 10 are connected in series. An expansion base unit 10a is
connected to a main base unit 20a and a main base unit 20b described later, and thus the
7
expansion base units 10 are connected in a row to the main base units 20.
[0017] The two input connectors and the two output connectors included in each
expansion base unit 10 enable the expansion base units 10 to be connected to each other
with dual-redundant bus connection cables. The two input connectors included in the
expansion base unit 10 also enable the two control devices 2 with dual-5 redundancy, or in
other words, the control device 2a and the control device 2b, to be connected to the
expansion base unit 10a. The configuration of the expansion base unit 10 is described in
detail later. The expansion base unit 10 is an example of an expansion base unit in an
aspect of the present disclosure.
10 [0018] The expressions "input" and "output" are herein used based on a signal flow
from the previous base unit to the subsequent expansion base unit. Thus, the connectors
used for communication with the previous base unit are "input connectors", and the
connectors used for communication with the subsequent expansion base unit are "output
connectors". The "previous base unit" may be either a main base unit or an expansion
15 base unit.
[0019] Each control device 2 includes a main base unit 20, a CPU module 21, and a
power supply 22. The control system 1000 includes the control device 2a and the
control device 2b, with a CPU module 21a in the control device 2a and a CPU module
21b in the control device 2b connected to each other with the tracking cable TC, thus
20 providing the dual-redundancy of the control devices 2.
[0020] The CPU module 21 and the power supply 22 are connected to nonillustrated
slots in the main base unit 20. The CPU module 21 controls the sensor and
the machine tool connected to the I/O module 11 in the control device 1. The CPU
module 21 communicates with the other CPU module 21 connected with the tracking
25 cable TC. As described in detail later, the CPU module 21 transmits a switch control
signal to the expansion base unit 10 to switch the output connector used in the expansion
base unit 10. The power supply 22 powers the main base unit 20 and the CPU module
8
21. The control device 2 may include multiple power supplies 22. An I/O module
may be connected to a slot in the main base unit 20. The configuration of the CPU
module 21 is described in detail later.
[0021] The main base unit 20 communicates with the components connected to the
non-illustrated slots and also communicates with the expansion base 5 unit 10 connected
with the bus connection cable. The main base unit 20 includes an output connector 201.
In FIG. 1, the main base unit 20a includes an output connector 201a connected with the
bus connection cable C11, and the main base unit 20b includes an output connector 201b
connected with the bus connection cable C12. The configuration of the main base unit
10 20 is described in detail later. The main base unit 20 is an example of a main base unit
in an aspect of the present disclosure.
[0022] These components included in the control device 2 enable the control device
2 to control the sensor and the machine tool connected to the I/O module 11 in the control
device 1.
15 [0023] The configuration of the expansion base unit 10 is described in detail with
reference to FIG. 2. Although the configuration of the expansion base unit 10a is
illustrated in FIG. 2 as a typical example, an expansion base unit 10b and another nonillustrated
base unit connected to the expansion base unit 10b also have the same
configuration.
20 [0024] The expansion base unit 10 includes the input connector 101, the input
connector 102, the output connector 111, the output connector 112, an input controller
121, an input switch 122, an output controller 131, an output switch 132, one or more
slots 190, and a bus B. The slots 190 are communicatively connected with the bus B.
As described in detail later, the input switch 122 communicatively connects the bus B to
25 either the input connector 101 or the input connector 102 under the control of the input
controller 121. Similarly, the output switch 132 communicatively connects the bus B to
either the output connector 111 or the output connector 112 under the control of the
9
output controller 131. The bus B is an internal bus connecting the input switch 122, the
output switch 132, and the slots 190 inside the expansion base unit 10. The bus B is an
example of an internal bus in an aspect of the present disclosure.
[0025] The input connector 101 and the input connector 102 are communicatively
connected to the output connectors of the previous base unit(s) with 5 the bus connection
cables. For the expansion base unit 10a, the input connector 101a is communicatively
connected to the output connector 201a of the previous main base unit 20a with the bus
connection cable C11, and the input connector 102a is communicatively connected to the
output connector 201b of the previous main base unit 20b with the bus connection cable
10 C12. The input connector 101 and the input connector 102 are examples of input
connectors in an aspect of the present disclosure.
[0026] The output connector 111 and the output connector 112 are
communicatively connected to the input connectors of the subsequent expansion base
unit with the bus connection cables. For the expansion base unit 10a, the output
15 connector 111a is communicatively connected to the input connector 101b of the
subsequent expansion base unit 10b with the bus connection cable C21, and the output
connector 112a is communicatively connected to the input connector 102b of the
subsequent expansion base unit 10b with the bus connection cable C22. The output
connector 111 and the output connector 112 are examples of output connectors in an
20 aspect of the present disclosure.
[0027] The input controller 121 monitors signals received by the input connector
101 and the input connector 102, identifies the input connector currently used for
communication between the previous base unit and the bus B, and connects the identified
input connector to the bus B by controlling the input switch 122 described later. The
25 input connector used for the communication and the input connector not used for the
communication receive different signals. Thus, the input controller 121 can identify the
input connector currently used for the communication between the previous base unit and
10
the bus B by monitoring signals received by the input connector 101 and the input
connector 102. For example, the input controller 121 can identify the input connector
used for the communication by determining whether clock signals received by the input
connectors change periodically or do not change.
[0028] As described in detail later, either the input connector 5 101 or the input
connector 102 is used for the communication between the previous base unit and the bus
B irrespective of whether the previous base unit corresponds to the single expansion base
unit 10 or the two main base units 20.
[0029] The input switch 122 communicatively connects, under the control of the
10 input controller 121, the bus B to the input connector currently used for communication
between the previous base unit and the bus B. Although FIG. 2 illustrates the input
switch 122 as a switch, the input switch 122 is, for example, a switch circuit including a
switching element such as a transistor or a relay. The input controller 121 and the input
switch 122 each are an example of first connection means in an aspect of the present
15 disclosure.
[0030] When receiving a switch control signal from the previous base unit through
the bus B, the output controller 131 controls the output switch 132 to switch the output
connector connected to the bus B. As described in detail later, when detecting an
abnormality in communication between two expansion base units 10, the CPU module 21
20 transmits a switch control signal to the previous expansion base unit 10 of the two
expansion base units 10. Thus, the output controller 131 can receive the switch control
signal from the previous base unit through the bus B. As a result, in the expansion base
unit 10b, either the input connector 101b or the input connector 102b is used for
communication between the expansion base unit 10a and the expansion base unit 10b.
25 [0031] For example, an abnormality may occur in the bus connection cable C21
connecting the output connector 111a of the expansion base unit 10a and the input
connector 101b of the expansion base unit 10b, causing a communication failure between
11
the output connector 111a and the input connector 101b. In this example, the output
switch 132 connects the output connector 111a and the bus B. In this state, the CPU
module 21 detects the abnormality between the output connector 111a and the input
connector 101b, and transmits a switch control signal to the expansion base unit 10a that
is the previous expansion base unit 10. When receiving the switch control 5 signal from
the CPU module 21 through the bus B, the output controller 131 controls the output
switch 132 to switch the output connector connected with the bus B from the output
connector 111a to the output connector 112a.
[0032] The output switch 132 switches, under the control of the output controller
10 131, the output connector connected to the bus B. More specifically, the output switch
132 communicatively connects the bus B and one of the output connector 111 or the
output connector 112 based on a switch control signal received from the previous base
unit. Although FIG. 2 illustrates the output switch 132 as a switch, the output switch
132 is, for example, a switch circuit including a switching element such as a transistor or
15 a relay. The output controller 131 and the output switch 132 each are an example of
second connection means in an aspect of the present disclosure.
[0033] The slots 190 are connected to the bus B and connectable to components
such as the I/O module 11 and the power supply 12. The slots 190 communicatively
connect the connected components and the bus B.
20 [0034] The configuration of the main base unit 20 is described in detail with
reference to FIG. 3. Although the configuration of the main base unit 20a is illustrated
in FIG. 3 as a typical example, the main base unit 20b also has the same configuration.
[0035] The main base unit 20 includes the output connector 201, one or more slots
202, and a bus BB. The output connector 201 and the slots 202 are communicatively
25 connected to the bus BB.
[0036] The output connector 201 is communicatively connected to an input
connector of the subsequent expansion base unit 10a with a bus connection cable. For
12
the main base unit 20a, the output connector 201a is communicatively connected to the
input connector 101a of the subsequent expansion base unit 10a with the bus connection
cable C11.
[0037] The slots 202 are connected to the bus BB and connectable to components
such as the CPU module 21 and the power supply 22. The slots 202 5 communicatively
connect the connected components and the bus BB.
[0038] The CPU module 21 connected to a slot 202 communicates with the
expansion base unit 10a through the bus BB, the output connector 201, and the bus
connection cable. The CPU module 21 also communicates with expansion base units
10 10 subsequent to the expansion base unit 10a through each expansion base unit 10
previous to those expansion base units 10.
[0039] The configuration of the CPU module 21 is described in detail with
reference to FIG. 4. The CPU module 21 includes a controller 210, a first
communicator 214, a second communicator 215, and a storage 216.
15 [0040] The first communicator 214 is, for example, a communication interface
insertable into the slot 202. The second communicator 215 is, for example, a
communication interface into which the tracking cable TC is insertable.
[0041] The storage 216 stores a control program executable by the controller 210.
The controller 210 functions as a working memory when the controller 210 executes the
20 control program. The storage 216 includes, for example, a read-only memory (ROM)
that stores the control program and a random-access memory (RAM) that functions as the
working memory.
[0042] The controller 210 reads and executes the control program stored in the
storage 216. The controller 210 includes a processor such as a microprocessing unit
25 (MPU) or a CPU. The controller 210 executes the control program to communicate
through the first communicator 214 with the components connected to the main base unit
20 and the expansion base unit 10. In particular, the controller 210 communicates with
13
the I/O module 11 connected to the expansion base unit 10 and controls the sensor and
the machine tool connected to the I/O module 11.
[0043] The controller 210 monitors the state of the other CPU module 21 through
the second communicator 215. When the controller 210 and the other CPU module 21
are both in a normal state, the controller 210 communicates with the 5 other CPU module
21 and determines either the controller 210 or the other CPU module 21 to communicate
with each module through the first communicator 214.
[0044] The controller 210 also executes the control program to function as an
abnormality determiner 211, an abnormality location detector 212, and a switch
10 controller 213.
[0045] The abnormality determiner 211 determines whether the communication
between the CPU module 21 and other components has any abnormality. The other
components include, in addition to the components connected to the main base unit 20,
the components connected to each expansion base unit 10 connected subsequent to the
15 main base unit 20. The determination as to whether the communication has any
abnormality is performed, for example, based on whether any target I/O module 11
returns a response to an access signal that the CPU module 21 has transmitted to the I/O
module 11.
[0046] When the abnormality determiner 211 determines an abnormality in the
20 communication between the CPU module 21 and another module, the abnormality
location detector 212 detects the location of the abnormality on the communication paths.
The manner in which the abnormality is located is described later in connection with the
operation of switch control.
[0047] When the abnormality location detector 212 locates the abnormality in any
25 one of the bus connection cables connecting subsequent expansion base units 10, the
switch controller 213 transmits a switch control signal to the previous expansion base unit
10 of the two expansion base units 10 connected with the bus connection cable having the
14
abnormality. This switches the output connector used in the expansion base unit 10 for
the communication between the expansion base units 10 to allow communication through
one of the dual-redundant bus connection cables that is free of abnormality.
[0048] When the abnormality location detector 212 locates the abnormality in
internal communication of the main base unit 20 or in the bus 5 connection cable
connecting the main base unit 20 to the expansion base unit 10, the switch controller 213
communicates with the other CPU module 21 and transmits a signal commanding the
other CPU module 21 to switch the control section. In this state, the controller 210 stops
communication with each module through the first communicator 214. When
10 receiving, from the other CPU module 21, a signal commanding the control section to be
switched, the switch controller 213 starts communication with each module through the
first communicator 214. These functions allow either the main base unit 20a or the
main base unit 20b to communicate with the expansion base unit 10a. More
specifically, these functions switch the control section that controls the sensor and the
15 machine tool. The two control sections are not enabled at the same time, and thus for
the expansion base unit 10a, either the input connector 101a or the input connector 102a
is used for communication between the main base unit 20 and the expansion base unit
10a.
[0049] An example hardware configuration of the expansion base unit 10 is
20 described with reference to FIG. 5. The expansion base unit 10 illustrated in FIG. 5 is,
for example, implemented by a microcontroller. The main base unit 20 may also have a
similar hardware configuration.
[0050] The expansion base unit 10 includes a processor 2001, a memory 2002, and
an interface 2003 connected to one another with a bus 2000.
25 [0051] The processor 2001 is a processor such as an MPU or a CPU. The
processor 2001 executes a control program stored in the memory 2002 to implement the
functions of the input controller 121 and the output controller 131 in the expansion base
15
unit 10.
[0052] The memory 2002 is, for example, a main memory including a ROM and a
RAM. The memory 2002 stores the control program executable by the processor 2001.
The memory 2002 functions as a working memory when the processor 2001 executes the
5 control program.
[0053] The interface 2003 is an input-output interface for communicatively
connecting the expansion base unit 10 and another unit. The interface 2003 implements
the functions of the input connector 101, the input connector 102, the output connector
111, the output connector 112, and the slots 190.
10 [0054] An example operation of input switching performed by the expansion base
unit 10 is described with reference to FIG. 6. The operation illustrated in FIG. 6 is
started when, for example, the expansion base unit 10 is powered.
[0055] The input controller 121 in the expansion base unit 10 monitors signals
received by each input connector (step S101).
15 [0056] The input controller 121 identifies, based on the signals monitored in step
S101, the input connector currently used for communication with the previous base unit
(step S102).
[0057] The input controller 121 controls the input switch 122 in the expansion base
unit 10 to communicatively connect the bus B and the input connector identified in step
20 S102. When the identified input connector is already connected to the bus B, the input
switch 122 remains in that state. The input controller 121 then repeats the operation
from step S101.
[0058] An example operation of output switching performed by the expansion base
unit 10 is described with reference to FIG. 7. The operation illustrated in FIG. 7 is
25 started when, for example, the expansion base unit 10 is powered.
[0059] The output controller 131 in the expansion base unit 10 awaits a switch
control signal transmitted from the previous base unit through the bus B (step S201).
16
[0060] When the output controller 131 receives a switch control signal in step
S201, the output controller 131 controls the output switch 132 to switch the output
connector connected to the bus B (step S202). The output controller 131 then repeats
the operation from step S201.
[0061] An example operation of switch control performed by the 5 CPU module 21 is
described with reference to FIG. 8. The operation illustrated in FIG. 8 is started when
the abnormality determiner 211 in the controller 210 in the CPU module 21 determines
an abnormality in communication between the CPU module 21 and another module.
The operation illustrated in FIG. 8 is an operation performed by the CPU module 21a on
10 the main base unit 20a.
[0062] The abnormality location detector 212 in the controller 210 in the CPU
module 21a determines whether a component on the main base unit 20a connected with
the CPU module 21a is accessible (step S301).
[0063] When the module on the main base unit 20a is inaccessible (No in step
15 S301), the abnormality location detector 212 detects the main base unit 20a as the
location of the abnormality (step S302).
[0064] The switch controller 213 in the controller 210 communicates with the CPU
module 21b and switches the control section from the CPU module 21a to the CPU
module 21b on the main base unit 20b (step S303). The controller 210 then ends the
20 operation of switch control.
[0065] When the module on the main base unit 20a is accessible (Yes in step
S301), the abnormality location detector 212 determines whether a component on the
expansion base unit 10a connected to the main base unit 20a is accessible (step S304).
[0066] When the component on the expansion base unit 10a is inaccessible (No in
25 step S304), the abnormality location detector 212 detects the bus connection cable C11
connecting the main base unit 20a and the expansion base unit 10a as the location of the
abnormality (step S305).
17
[0067] Similarly to the above processing, the switch controller 213 communicates
with the CPU module 21b and switches the control section from the CPU module 21a to
the CPU module 21b on the main base unit 20b (step S303). The controller 210 then
ends the operation of switch control.
[0068] When the component on the expansion base unit 10a is 5 accessible (Yes in
step S304), the abnormality location detector 212 determines whether a component on the
expansion base unit 10b connected to the expansion base unit 10a is accessible (step
S306).
[0069] When the component on the expansion base unit 10b is inaccessible (No in
10 step S306), the abnormality location detector 212 detects the bus connection cable C21 or
the bus connection cable C22 connecting the expansion base unit 10a and the expansion
base unit 10b as the location of the abnormality (step S307).
[0070] The switch controller 213 transmits a switch control signal to the expansion
base unit 10a that is the previous one of the expansion base unit 10a or the expansion
15 base unit 10b, and switches the output connector used for communication between the
expansion base unit 10a and the expansion base unit 10b (step S308). The controller
210 then ends the operation of switch control.
[0071] When the component on the expansion base unit 10b is accessible (Yes in
step S306), the controller 210 performs the operation in steps S306 to S308 on the
20 subsequent expansion base unit 10. The switch controller 213 repeats the operation and
transmits a switch control signal to the appropriate expansion base unit 10, and then the
controller 210 ends the operation of switch control.
[0072] The control system 1000 according to Embodiment 1 has been described.
In the control system 1000 according to Embodiment 1, each expansion base unit 10
25 includes two input connectors and two output connectors. The input controller 121 and
the input switch 122 connect one of the input connectors to the bus B, whereas the output
controller 131 and the output switch 132 connect one of the output connectors to the bus
18
B. Thus, the control system 1000 according to Embodiment 1 enables the expansion
base units 10 to be connected to each other with multi-redundant cables.
[0073] In the control system 1000 according to Embodiment 1, the I/O module 11,
the power supply 12, the main base unit 20, and the power supply 22 may have known
hardware configurations without any change. The CPU module 21 5 may also have the
same hardware configuration as a known CPU module, and the different appropriate
control program may simply be stored in the storage 216 and executed by the controller
210. Thus, the control system 1000 according to Embodiment 1 is not to include new
hardware as the components except the expansion base units 10. Thus, the control
10 system 1000 according to Embodiment 1 enables the expansion base units 10 to be
connected to each other with multi-redundant cables at low cost.
[0074] In the control system 1000 according to Embodiment 1, the multiple input
connectors and output connectors included in each expansion base unit 10 allow use of
the same expansion base units that can provide multi-redundancy of cables, thus reducing
15 cost.
[0075] Modification of Embodiment 1
In Embodiment 1, the input controller 121 identifies the input connector currently
used for communication between the previous base unit and the bus B by monitoring
signals received by the input connector 101 and the input connector 102, and connects the
20 identified input connector to the bus B by controlling the input switch 122. Instead, as
illustrated in FIG. 9, the input controller 121 may monitor signals transmitted to the bus
B. When detecting an abnormality in signals transmitted to the bus B from the input
connector currently connected to the bus B, the input controller 121 may control the input
switch 122 to switch the input connector connected to the bus B. For example, when
25 signals transmitted to the bus B remain unchanged for at least a predetermined period, the
input controller 121 detects an abnormality in the signals transmitted to the bus B and
switches the input connector connected to the bus B. In this modification, although
19
abnormality detection is to be performed, a single target is simply monitored.
[0076] In Embodiment 1, each expansion base unit 10 includes the two input
connectors and the two output connectors to provide the dual-redundancy of the bus
connection cables. However, each expansion base unit 10 may include three or more
input connectors and three or more output connectors to provide the multi-5 redundancy of
the bus connection cables. Of the expansion base units 10, the expansion base unit 10a
connected directly to the main base unit 20 may include different numbers of input
connectors and output connectors. This is because the degree of multi-redundancy of
the CPU modules 21 may not be the same as the degree of multi-redundancy of the bus
10 connection cables connecting the expansion base units 10. More specifically, the
number of bus connection cables connecting the expansion base units 10 may not be the
same as the number of main base units 20 connected to each expansion base unit 10.
[0077] In Embodiment 1, cable multi-redundancy is provided between all the
expansion base units 10. However, cable multi-redundancy between some expansion
15 base units 10 may be sufficient. In this case, each expansion base unit 10 in a cable
multi-redundancy section may include multiple input connectors and multiple output
connectors, and each expansion base unit 10 in a cable non-redundancy section may
include at least one input connector and at least one output connector. The expansion
base unit 10 between the non-redundancy section and the multi-redundancy section may
20 include at least one input connector and multiple output connectors, or multiple input
connectors and at least one output connector.
[0078] Embodiment 2
A control system 1000 according to Embodiment 2 is described. The control
system 1000 according to Embodiment 2 has the same overall configuration as in
25 Embodiment 1 illustrated in FIG. 1. As described in detail later, each expansion base
unit 10 in the control system 1000 according to Embodiment 2 includes an output
connector 111 and an output connector 112 connected constantly to the bus B, and a
20
selection signal indicating the selected output connector is output to at least one of the
output connector 111 or the output connector 112.
[0079] Referring to FIG. 10, the configuration of the expansion base unit 10
according to Embodiment 2 is described focusing on differences from the configuration
in Embodiment 1. Unlike in Embodiment 1, the expansion base unit 5 10 according to
Embodiment 2 includes no output switch 132, with the output connector 111 and the
output connector 112 communicatively connected constantly to the bus B. Unlike in
Embodiment 1, the output controller 131 outputs a selection signal (described later) to
one of the output connector 111 or the output connector 112. Unlike in Embodiment 1,
10 the input controller 121 connects the bus B to one of the input connector 101 or the input
connector 102 that has received a selection signal. In FIG. 10, dash-dot arrows indicate
input and output of selection signals. In Embodiment 2, the bus connection cables use
signal lines for transmitting selection signals.
[0080] The output controller 131 in Embodiment 2 is substantially the same as in
15 Embodiment 1. However, unlike in Embodiment 1, when receiving a switch control
signal from the previous base unit through the bus B, the output controller 131 (i) selects,
from among the output connectors, a different output connector that is different from a
currently-selected output connector and (ii) outputs a selection signal to the different
output connector, instead of controlling the output switch 132. In an initialization
20 process, the output controller 131 selects, immediately after the expansion base unit 10 is
powered, any one of the output connector 111 or the output connector 112 and outputs a
selection signal to the selected output connector. In Embodiment 2, the output
controller 131 is an example of selection signal output means in an aspect of the present
disclosure.
25 [0081] Unlike in Embodiment 1, the input controller 121 in Embodiment 2 controls
the input switch 122 to communicatively connect the bus B to one of the input connector
101 or the input connector 102 that has received a selection signal. However, for the
21
previous base unit being a main base unit 20 that outputs no selection signal, neither the
input connector 101 nor the input connector 102 receives a selection signal. In this case,
the input controller 121 controls the input switch 122 in the same manner as in
Embodiment 1.
[0082] The control system 1000 according to Embodiment 2 has 5 been described.
The control system 1000 according to Embodiment 2 can produce the same advantageous
effects as the control system 1000 according to Embodiment 1 without the output switch
132.
[0083] Embodiment 3
10 A control system 1000 according to Embodiment 3 is described. The control
system 1000 according to Embodiment 3 has the same overall configuration as in
Embodiment 1 illustrated in FIG. 1. In Embodiment 3, each expansion base unit 10 has
a different configuration from the expansion base unit 10 in Embodiment 1. As
described in detail later, although the expansion base unit 10 has the different
15 configuration from the expansion base unit 10 in Embodiment 1, the input connectors and
the output connectors receive and output the same signals as in Embodiment 1, and the
bus connection cables used are the same as in Embodiment 1.
[0084] Referring to FIG. 11, the configuration of the expansion base unit 10
according to Embodiment 3 is described focusing on the differences from the
20 configuration in Embodiment 1. Unlike in Embodiment 1, the expansion base unit 10
according to Embodiment 3 does not include the input controller 121, the input switch
122, the output controller 131, or the output switch 132. Unlike in Embodiment 1, the
expansion base unit 10 includes a transferrer 150. The transferrer 150 includes multiple
ports such as ports P1 to P6, a transfer controller 151, and a storage 152. Unlike in
25 Embodiment 1, the input connector 101, the input connector 102, the output connector
111, and the output connector 112 are respectively connected to the ports P1 to P4, and
the multiple slots 190 are each connected to a corresponding port of multiple ports
22
including the ports P5 and P6. In the transferrer 150, the function of the transfer
controller 151 described later appropriately enables communicatively connecting the
input connector 101, the input connector 102, the output connector 111, the output
connector 112, and each slot 190. Thus, the transferrer 150 is an example of an internal
bus in an aspect of the present 5 disclosure.
[0085] The transferrer 150 is, for example, implemented by a microcontroller. In
this case, the transfer controller 151 is, for example, an MPU included in the
microcontroller. The storage 152 is, for example, a ROM and a RAM included in the
microcontroller. Each port is, for example, an I/O interface included in the
10 microcontroller. The function of the transfer controller 151 described later is, for
example, implemented by the MPU reading and executing the control program stored in
the ROM.
[0086] The storage 152 stores a transfer destination table used for a transfer process
performed by the transfer controller 151 described later. The transfer destination table
15 is, for example, a table illustrated in FIG. 12. The transfer destination table is described
in detail later.
[0087] The transfer controller 151 monitors signals received by the port P1 from the
input connector 101 and signals received by the port P2 from the input connector 102,
and identifies the port currently used for the communication between the previous base
20 unit and the transferrer 150 serving as a bus. In the transfer process described later, the
transfer controller 151 transfers the signals received by the identified port to the output
connector 111, the output connector 112, or each slot 190. The transfer controller 151
communicatively connects one input connector connected to one identified port and the
transferrer 150 serving as a bus. The transfer controller 151 functioning in such a
25 manner is an example of first connection means in an aspect of the present disclosure.
[0088] The transfer controller 151 refers to the transfer destination table stored in
the storage 152 and transfers a signal received by the identified port to the port
23
corresponding to the destination of the signal. When the transfer destination table is, for
example, the table illustrated in FIG. 12, the transfer controller 151 transfers signals
directed to an I/O module 11a to the port P6, and also transfers signals directed to a
component on the expansion base unit 10b, such as an I/O module 11b or a power supply
12b, to the port P3. The transfer process performed by the transfer 5 controller 151
communicatively connects the transferrer 150 serving as a bus and one output connector
connected to one port set as a transfer destination port. The transfer controller 151
functioning in such a manner is an example of second connection means in an aspect of
the present disclosure.
10 [0089] When receiving a switch control signal from the previous base unit through
the identified port, the transfer controller 151 rewrites the transfer destination table stored
in the storage 152 to change the transfer destination port for signals directed to each
component on the expansion base unit 10b from the port P3 connected to the output
connector 111 to the port P4 connected to the output connector 112. With this function,
15 the transfer controller 151 can switch the output connector connected to the transferrer
150 serving as a bus when receiving a switch control signal.
[0090] In this manner, the transferrer 150 implements the same functions as the
input controller 121, the input switch 122, the output controller 131, the output switch
132, and the bus B in Embodiment 1. Thus, the control system 1000 according to
20 Embodiment 3 produces the same advantageous effects as the control system 1000
according to Embodiment 1 with the transferrer 150 included in the expansion base unit
10. The transferrer 150 may be implemented by, for example, a microcontroller as
described above, thus allowing the expansion base unit 10 to be designed flexibly at low
cost in Embodiment 3. For example, in Embodiment 3, the transferrer 150 that is a
25 microcontroller including a sufficient number of ports can accommodate increased
numbers of input connectors and output connectors in the expansion base unit 10 by
rewriting the control program executed by the transfer controller 151.
24
[0091] The foregoing describes some example embodiments for explanatory
purposes. Although the foregoing discussion has presented specific embodiments,
persons skilled in the art will recognize that changes may be made in form and detail
without departing from the broader spirit and scope of the invention. Accordingly, the
specification and drawings are to be regarded in an illustrative rather 5 than a restrictive
sense. This detailed description, therefore, is not to be taken in a limiting sense, and the
scope of the invention is defined only by the included claims, along with the full range of
equivalents to which such claims are entitled.
Reference Signs List
10 [0092]
1, 1a, 1b, 2, 2a, 2b Control device
10, 10a, 10b Expansion base unit
11, 11a, 11b I/O module
12, 12a, 12b Power supply
15 20, 20a, 20b Main base unit
21, 21a, 21b CPU module
22, 22a, 22b Power supply
101, 101a, 101b, 102, 102a, 102b Input connector
111, 111a, 111b, 112, 112a, 112b Output connector
20 121 Input controller
122 Input switch
131 Output controller
132 Output switch
150 Transferrer
25 151 Transfer controller
152 Storage
190 Slot
25
201, 201a, 201b Output connector
202 Slot
210 Controller
211 Abnormality determiner
212 Abnormality 5 location detector
213 Switch controller
214 First communicator
215 Second communicator
216 Storage
10 1000 Control system
2000 Bus
2001 Processor
2002 Memory
2003 Interface
15 B, BB Bus
C11, C12, C21, C22, C31, C32 Bus connection cable
P1 to P6 Port
TC Tracking cable
We Claim :
1. An expansion base unit comprising:
an input connector communicatively connectable with a cable to a connector in a
previous base unit to allow receipt of a signal from the previous base unit; and
a plurality of output connectors that each are communicatively 5 connectable with a
cable to a connector of a plurality of connectors in a subsequent expansion base unit to
allow transmission of the signal received by the input connector to the subsequent
expansion base unit.
2. The expansion base unit according to claim 1, further comprising:
an internal bus;
first connection means for communicatively connecting the input connector to the
internal bus; and
second connection means for communicatively connecting one output connector of
the plurality of output connectors to the internal bus without communicatively connecting
another output connector to the internal bus.
3. The expansion base unit according to claim 2, wherein the second
connection means switches the output connector connected to the internal bus upon
receiving a switch control signal from the previous base unit through the input connector
and the internal bus connected to each other by the first connection means.
4. The expansion base unit according to claim 2 or 3, wherein
the input connector comprises a plurality of the input connectors, and
25 the first connection means identifies an input connector currently used for
communication between the previous base unit and the internal bus by monitoring a
signal received by each input connector of the plurality of input connectors, and
communicatively connects the identified input connector to the internal bus.
5. The expansion base unit according to claim 2 or 3, wherein
the input connector comprises a plurality of the input connectors,
the first connection means communicatively connects one input 5 connector of the
plurality of input connectors to the internal bus, and
the first connection means monitors a signal transmitted to the internal bus from
the input connector connected by the first connection means, and switches the input
connector connected to the internal bus upon detecting an abnormality in the signal.
6. The expansion base unit according to claim 1, further comprising:
selection signal output means for selecting one output connector of the plurality of
output connectors and outputting a selection signal to the selected output connector.
15 7. The expansion base unit according to claim 6, wherein, when the input
connector receives a switch control signal from the previous base unit, the selection
signal output means (i) selects, from among the plurality of output connectors, a different
output connector that is different from a currently-selected output connector and (ii)
outputs the selection signal to the selected different output connector.
8. The expansion base unit according to claim 6 or 7, wherein
the input connector comprises a plurality of the input connectors,
each of the plurality of input connectors is communicatively connectable with a
cable to a connector of a plurality of connectors in a previous expansion base unit to
25 allow receipt of a signal from the previous expansion base unit, and
the expansion base unit further comprises
an internal bus, and
first connection means for communicatively connecting the internal bus to,
among the plurality of input connectors, an input connector receiving a selection signal
output from the previous expansion base unit.
9. A control 5 device comprising:
the expansion base unit according to any one of claims 1 to 8; and
an input-output module communicatively connectable to the expansion base unit to
control an external device.
10. A control system comprising:
a plurality of the expansion base units according to any one of claims 1 to 8;
an input-output module to control an external device;
a main base unit; and
a central processing unit module communicatively connectable to the main base
15 unit, wherein
the input-output module is communicatively connectable to one expansion base
unit of the plurality of expansion base units,
the plurality of expansion base units are connected in a row to the main base unit,
and
the central processing unit module communicates with the input-output module
through the main base unit and the expansion base unit to control the external device.
11. A method for controlling an expansion base unit, the expansion base unit
including (i) an input connector communicatively connected with a cable to a connector
in a previous base unit and (ii) a plurality of output connectors that each are
communicatively connected with a cable to a connector of a plurality of connectors in a
subsequent expansion base unit, the method comprising:
transmitting a signal received by the input connector from the previous base unit to
the subsequent expansion base unit through the plurality of output connectors.