Patent Description:
<CIT> discloses an industrial wireless communication system including a computer and a plurality of communication networks. The computer manages and controls a plurality of robots and the like. Each communication network includes a single base wireless device and a plurality of remote wireless devices. The base wireless device is connected to the computer. Meanwhile, each remote wireless device is connected to a sensor and an actuator. The sensor and the actuator are provided for a robot or the like. For example, the base wireless device transmits a signal for instructing the operation of the actuator to each remote wireless device. In contrast, each remote wireless device transmits a signal indicating a detection result of the sensor or the like to the base wireless device. In the wireless communication system disclosed in <CIT>, the base wireless device and the plurality of remote wireless devices carry out frequency hopping at predetermined periods. This prevents radio wave interference between the base wireless device and the surrounding wireless devices. Similarly, radio wave interference between each remote wireless device and the surrounding wireless devices is prevented. The period for frequency hopping is referred to as a transmission/reception period.

<CIT> discloses a network for connecting a plurality of network nodes comprising a leader node and a plurality of follower nodes. The leader node and the plurality of follower nodes transmit information during a transmission period of the network interval and do not transmit information during a sleep period of the network interval.

The base wireless device, while transmitting signals to the remote wireless devices, is unable to receive signals transmitted from the remote wireless devices. Thus, while the base wireless device is transmitting a signal, the remote wireless devices fail to transmit a signal. After the base wireless device has finished transmitting the signal, signal transmissions carried out by the remote wireless devices are made successfully. Then, it may take a long time to complete the signal transmissions from the remote wireless devices to the base wireless device. As a result, the communication speed of the wireless communication system decreases, and the processing capability of the robot or the like decreases.

An object of the present invention is to solve the aforementioned problem.

According to a first aspect of the present invention, a base wireless device that transmits and receives signals to and from at least one remote wireless device in a transmission/reception period, includes a selection unit configured to select either signal transmission or standby in the transmission/reception period, and a transmission processing unit configured to perform a transmission process of transmitting a signal to the at least one remote wireless device in the transmission/reception period in a case that the selection unit selects the signal transmission, and to stand by without performing the transmission process in the transmission/reception period in a case that the selection unit selects the standby, wherein the selection unit selects either the signal transmission or the standby in a current transmission/reception period in accordance with a predetermined rule in a case that the signal transmission was selected in a previous transmission/reception period, and selects the signal transmission in the current transmission/reception period in a case that the standby was selected in the previous transmission/reception period.

According to a second aspect of the present invention, a communication method of a base wireless device that transmits and receives signals to and from at least one remote wireless device in a transmission/reception period, is provided. The communication method includes a selection step of selecting either signal transmission or standby in the transmission/reception period, and a transmission processing step of performing a transmission process of transmitting a signal to the at least one remote wireless device in the transmission/reception period in a case that the signal transmission is selected in the selection step, and standing by without performing the transmission process in the transmission/reception period in a case that the standby is selected in the selection step, wherein in the selection step, either the signal transmission or the standby is selected in a current transmission/reception period in accordance with a predetermined rule in a case that the signal transmission was selected in a previous transmission/reception period, and the signal transmission is selected in the current transmission/reception period in a case that the standby was selected in the previous transmission/reception period.

According to the present invention, it is possible to shorten the time required for successful signal transmission of the remote wireless device.

<FIG> is a diagram illustrating a configuration of a wireless communication system <NUM>. <FIG> is a functional block diagram of the wireless communication system <NUM> according to the present embodiment. The industrial wireless communication system <NUM> includes a single computer <NUM> and at least one communication network <NUM>. The one communication network <NUM> includes a single base wireless device <NUM> and a plurality of remote wireless devices <NUM>. An industrial facility is provided with one or more robots (not shown).

The computer <NUM> monitors and controls one or a plurality of robots and the like. The computer <NUM> may include, for example, a programmable logic controller (PLC). The computer <NUM> includes an interface (not illustrated) for performing wired or wireless transmission and reception. The computer <NUM> transmits a signal to the base wireless device <NUM> via the interface. The computer <NUM> also receives a signal transmitted from the base wireless device <NUM> via the interface.

One or more robots or the like include one or more actuators and one or more sensors. The actuator operates in accordance with instructions from the computer <NUM>. The sensor detects an operation of the robot. The sensor and actuator are also collectively referred to herein as an S/A <NUM>. The actuator receives a control signal transmitted from the computer <NUM> via the base wireless device <NUM> and the remote wireless device <NUM>. The sensor transmits a sensor signal indicative of the detection result to the computer <NUM> via the base wireless device <NUM> and the remote wireless device <NUM>.

As illustrated in <FIG>, the base wireless device <NUM> includes a base computation unit <NUM>, a base storage unit <NUM>, a base communication unit <NUM>, and a base interface <NUM>.

The base computation unit <NUM> includes processing circuitry. The processing circuitry may be a processor such as a CPU. The processing circuitry may be an integrated circuit such as an ASIC, an FPGA, or the like. The processor has various functions by executing programs stored in the base storage unit <NUM>. The base computation unit <NUM> functions as a frequency switching unit <NUM>, a transmission/reception processing unit <NUM>, a selection unit <NUM>, and an input/output control unit <NUM>.

The frequency switching unit <NUM> switches the frequency of the channel used by the base communication unit <NUM> based on hopping information. The hopping information is stored in advance in the base storage unit <NUM>.

The transmission/reception processing unit (transmission processing unit) <NUM> uses the transmission circuit of the base communication unit <NUM> to perform a process of transmitting a signal to the remote wireless device <NUM>. This process is referred to as a transmission process. In addition, the transmission/reception processing unit <NUM> uses the reception circuit of the base communication unit <NUM> to perform a process of receiving a signal transmitted by the remote wireless device <NUM>. The transmission/reception processing unit <NUM> transmits a signal of one packet in one transmission/reception period. The transmission/reception processing unit <NUM> performs a series of transmission process when transmitting a signal of one packet. The transmission process includes a process of transmitting a signal and a process of receiving an acknowledgement (ACK) transmitted from the remote wireless device <NUM>.

The selection unit <NUM> selects either signal transmission or standby in each transmission/reception period. For example, when the signal transmission was selected in the previous transmission/reception period, the selection unit <NUM> selects either the signal transmission or the standby in the current transmission/reception period. At this time, the selection unit <NUM> makes a selection in accordance with a predetermined rule. The predetermined rule is stored in the base storage unit <NUM>. For example, the predetermined rule may be information that determines a selection order of signal transmission and standby. Further, the predetermined rule may be an algorithm etc. for making a selection at random, for example, an algorithm for generating a pseudo random number sequence. On the other hand, when standby was selected in the previous transmission/reception period, the selection unit <NUM> selects signal transmission in the current transmission/reception period.

The input/output control unit <NUM> uses the base interface <NUM> to perform a process of transmitting a sensor signal received from the remote wireless device <NUM> to the computer <NUM>. The input/output control unit <NUM> uses the base interface <NUM> to perform a process of receiving a control signal transmitted by the computer <NUM>.

The base storage unit <NUM> includes a volatile memory and a nonvolatile memory. Examples of the volatile memory include a RAM. Examples of the nonvolatile memory include a ROM, a flash memory, and the like. The volatile memory stores, for example, data acquired externally and data calculated by the base computation unit <NUM>. The nonvolatile memory stores, for example, a predetermined program and a predetermined numerical value. The base storage unit <NUM> stores hopping information that is common to the remote wireless devices <NUM>. The hopping information includes information of a hopping pattern and information of a transmission/reception period. At least a part of the base storage unit <NUM> may be included in a processor, an integrated circuit, or the like as described above.

The base communication unit <NUM> includes a communication circuit. The communication circuit includes a transmission circuit and a reception circuit. The base communication unit <NUM> transmits a signal to the remote wireless device <NUM>. The base communication unit <NUM> receives a signal transmitted by the remote wireless device <NUM>.

The base interface <NUM> includes an input/output interface for carrying out wired communication with the computer <NUM>.

As shown in <FIG>, the remote wireless device <NUM> includes a remote computation unit <NUM>, a remote storage unit <NUM>, a remote communication unit <NUM>, and a remote interface <NUM>.

The remote computation unit <NUM> includes processing circuitry. The processing circuitry may be a processor such as a CPU. The processing circuitry may be an integrated circuit such as an ASIC, an FPGA, or the like. The processor has various functions by executing programs stored in the remote storage unit <NUM>. For example, the remote computation unit <NUM> uses the remote interface <NUM> to perform a process of transmitting a control signal to the S/A <NUM>. In addition, the remote computation unit <NUM> uses the remote interface <NUM> to perform a process of receiving a sensor signal from the S/A <NUM>. The remote computation unit <NUM> uses the remote communication unit <NUM> to perform a process of receiving a signal from the base wireless device <NUM>. Further, the remote computation unit <NUM> uses the remote communication unit <NUM> to perform a process of transmitting a signal to the base wireless device <NUM>. Further, the remote computation unit <NUM> switches the frequency of a channel used for communication with each of the remote wireless devices <NUM> based on the hopping information.

The remote storage unit <NUM> includes a volatile memory and a nonvolatile memory. Examples of the volatile memory include a RAM. Examples of the nonvolatile memory include a ROM, a flash memory, and the like. The volatile memory stores, for example, data acquired externally and data calculated by the remote computation unit <NUM>. The nonvolatile memory stores, for example, a predetermined program and a predetermined numerical value. The remote storage unit <NUM> stores hopping information that is common to the base wireless device <NUM>. The hopping information includes information of a hopping pattern and information of a transmission/reception period. At least a part of the remote storage unit <NUM> may be included in a processor, an integrated circuit, or the like as described above.

The remote communication unit <NUM> includes a communication circuit. The communication circuit includes a transmission circuit and a reception circuit. The remote communication unit <NUM> transmits a signal to the base wireless device <NUM>. The remote communication unit <NUM> receives a signal transmitted by the base wireless device <NUM>.

The remote interface <NUM> includes an input/output interface for carrying out wired communication with each S/A <NUM>. The remote interface <NUM> may include a wireless interface for carrying out short-range wireless communication with each S/A <NUM>.

A process of the base wireless device <NUM> related to transmission will be described with reference to <FIG> is a flowchart illustrating a process according to the present embodiment. The base computation unit <NUM> performs the process shown in <FIG> for each transmission/reception period.

In step S1, the frequency switching unit <NUM> switches the channel frequency in accordance with the hopping pattern stored in the base storage unit <NUM>. Upon completion of step S1, the process proceeds to step S2.

In step S2, the transmission/reception processing unit <NUM> determines whether there is any information to be conveyed to the S/A <NUM>. The information to be conveyed is, for example, a control signal acquired from the computer <NUM>. If there is such information to be conveyed (step S2: YES), the process proceeds to step S4. On the other hand, when there is not any information to be conveyed (step S2: NO), the process proceeds to step S3.

In step S3, the selection unit <NUM> selects standby in the current transmission/reception period. Here, the selection unit <NUM> stores the selection result of standby in the base storage unit <NUM>. When step S3 ends, the process in the current transmission/reception period is completed.

In step S4, the selection unit <NUM> determines the selection result of the selection unit <NUM> in the previous transmission/reception period. The selection result is stored in the base storage unit <NUM>. If the selection result is standby (step S4: standby), the process proceeds to step S5. On the other hand, when the selection result is signal transmission (step S4: signal transmission), the process proceeds to step S6. When the selection result is not recorded in the base storage unit <NUM>, the selection unit <NUM> determines that the selection result is standby.

When the process proceeds from step S4 to step S5, the selection unit <NUM> selects to transmit a signal in the current transmission/reception period. The selection unit <NUM> stores the selection result of signal transmission in the base storage unit <NUM>. Upon completion of step S5, the process proceeds to step S8.

When the process proceeds from step S4 to step S6, the selection unit <NUM> selects whether to transmit a signal in the current transmission/reception period or to stand by in the current transmission/reception period, in accordance with a predetermined rule. The selection unit <NUM> causes the base storage unit <NUM> to store the selection result that is either signal transmission or standby. Upon completion of step S6, the process proceeds to step S7.

When the selection unit <NUM> selects signal transmission in step S6 (step S7: signal transmission), the process proceeds to step S8. On the other hand, when the selection unit <NUM> selects standby in step S6 (step S7: standby), the transmission/reception processing unit <NUM> stands by in the current transmission/reception period. That is, the base wireless device <NUM> creates an opportunity to receive a signal transmitted by the remote wireless device <NUM>. At this time, when any one of the remote wireless devices <NUM> transmits a signal to the base wireless device <NUM>, the transmission/reception processing unit <NUM> performs a process for receiving the signal. When step S7 ends, the process in the current transmission/reception period is completed.

When the process proceeds from step S5 or step S7 to step S8, the transmission/reception processing unit <NUM> performs a transmission process. At this time, the transmission/reception processing unit <NUM> uses the base communication unit <NUM> to perform a process of transmitting a signal indicating information to be conveyed, to the remote wireless device <NUM>. When step S8 ends, the process in the current transmission/reception period is completed.

According to the present embodiment, when signal transmission was selected in the previous transmission/reception period, the selection unit <NUM> selects whether to transmit a signal or to stand by in the current transmission/reception period. At this time, the selection unit <NUM> basically selects standby with a probability of <NUM>/<NUM>. Therefore, the base wireless device <NUM> is less likely to continue transmitting a signal for a long time. In other words, the base wireless device <NUM> has more opportunities to receive signals. Therefore, according to the present embodiment, it is possible to shorten the time taken until the signal transmission of the remote wireless device <NUM> is made successfully.

Claim 1:
A base wireless device (<NUM>) that transmits and receives signals to and from at least one remote wireless device (<NUM>) in a transmission/reception period, comprising:
a selection unit (<NUM>) configured to select either signal transmission or standby in the transmission/reception period; characterized in that the base wireless device (<NUM>) further comprises
a transmission processing unit (<NUM>) configured to perform a transmission process of transmitting a signal to the at least one remote wireless device in the transmission/reception period in a case that the selection unit selects the signal transmission, and to stand by without performing the transmission process in the transmission/reception period in a case that the selection unit selects the standby,
wherein the selection unit selects either the signal transmission or the standby in a current transmission/reception period in accordance with a predetermined rule in a case that the signal transmission was selected in a previous transmission/reception period, and selects the signal transmission in the current transmission/reception period in a case that the standby was selected in the previous transmission/reception period.