Communication system and remote control terminal device

Abstract

To solve the problem of a shortage of the number of communication pairs of a control in a radio control by a remote controller, in addition, a cost and a work period because a radio engineer has to go to the site for performing an inspection of a radio frequency band before and after installation, determines a frequency and an installation location, and adjusts an antenna.SOLUTION: In a communication system 1 of the present invention, a communication pair 10 (P1 to P10) can share a communication channel #1. Since there is 16 communication channels, a pair of 160 communication channels can be used at the same location. A remote control terminal device 10 contained in each of the communication pairs P1 to P10 intermittently (0.8 ms) and periodically (20 ms) transmits a signal. Since a collision of the signal is avoided by a signal transmission for applying an off-set of the random number to a predetermined period, the signal is transmitted to a control device in a constant ratio while generating the signal collision between the communication pairs 10. The pair of 160 which is four times as compared with a conventional art can be used, and an adjustment by an engineer is not required.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present disclosure relates to a communication system and a remote control terminal device. [Background technology]

[0002] In recent years, wireless communication technologies such as wireless LANs (Local Area Networks) have been rapidly becoming widespread (see, for example, Patent Documents 1 to 4). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2006-222608 [Patent Document 2] Japanese Patent Application Laid-Open No. 2009-182644 [Patent Document 3] Japanese Patent Application Laid-Open No. 2012-147324 [Patent Document 4] Japanese Patent Publication No. 2020-129733 Summary of the Invention [Problem to be solved by the invention]

[0004] Conventionally, in factories and other places, remote control of equipment such as cranes has been commonplace. Because safety is a major concern, communication for this remote control has primarily been achieved via wired communication, which is considered to be highly reliable. Ensuring safety is particularly important when controlling powered devices. Wireless communication has the advantage of eliminating the need for communication and power lines connecting the equipment and the remote control, so it is conceivable to replace wired communication with wireless communication for remote control of equipment in factories and other places. When switching from wired to wireless remote control, ensuring safety is of the utmost importance. It is necessary to satisfy the demand for rapid and reliable response in the event of an abnormality. To achieve this, it is necessary to ensure reliable remote control communication. Therefore, it is considered best to assign a dedicated communication channel (specific frequency band) to each pair of remote control and the equipment to be operated, and to occupy that communication channel exclusively for communication for remote control of that equipment. On the other hand, with the system that assigns a dedicated communication channel to each pair of remote controller and target device, the conventional specified low-power wireless communication system (wireless equipment in the 400 MHz band with an occupied frequency bandwidth of 8.5 kHz or less) has 46 communication channels, limiting the system to 46 devices. The conventional specified low-power wireless communication system (wireless equipment in the 1200 MHz band with an occupied frequency bandwidth of 16 kHz or less) has 40 communication channels, limiting the system to 40 devices. This finite number of channels raises concerns about a shortage of communication channels. Furthermore, there are safety risks, such as malfunctions due to interference with other communications on the same frequency or adjacent channels, or spurious signals. Furthermore, to prevent interference and jamming that threaten safety, wireless engineers must survey the available wireless frequency bands during installation, determine the number of devices that can be installed, determine installation locations, and adjust antennas on-site. In conventional specified low-power wireless communication systems, a channel cannot be used if it is already in use, and even if it is not the same channel, interference can occur if an adjacent channel is already in use, so on-site investigation is essential.The amount of work required for this, including investigating any problems that may arise after installation, cannot be ignored.

[0005] The present invention aims to ensure safety in wireless communication control and achieve rapid system operation, and provides a technology that enables rapid response to abnormalities, avoids system malfunctions due to interference with other communications, and eliminates the need for engineers to make on-site adjustments during installation, thereby achieving wireless communication that allows remote operation of equipment using a remote controller without monopolizing the communication channel. [Means for solving the problem]

[0006] A communication system according to a first aspect of the present disclosure includes: N pairs of remote control terminal devices and control devices (N is an integer of 1 or more) are provided; Each of the plurality of remote control terminal devices a wireless communication unit that transmits data to a control device paired with the device itself by wireless communication on a predetermined communication channel; The wireless communication device is characterized by having a control unit that adjusts the timing of execution of the wireless communication by the wireless communication unit by adding an offset corresponding to a random number to a timing determined according to a predetermined period.

[0007] A more preferable communication system according to a second aspect is the communication system according to the first aspect, The wireless communication unit included in each of the plurality of remote control terminal devices is performing intermittent periodic transmission (hereinafter referred to as burst transmission) on the communication channel over a predetermined period of time; It is characterized by:

[0008] A more preferable communication system according to a third aspect is the communication system according to the second aspect, further comprising: When the N control devices detect interference or obstruction in wireless communication with a remote control terminal device paired with the own device, the N control devices transmit a change instruction to the remote control terminal device paired with the own device, instructing the change of the communication channel; the control unit included in each of the N remote control terminal devices changes the communication channel used for transmitting data to the control device paired with the respective device in response to the change instruction; It may be characterized by the fact that

[0009] A more preferable communication system according to a fourth aspect is the communication system of the third aspect, When the N control devices detect interference or disturbance in a communication channel used for wireless communication with a remote control terminal device paired with the device itself, the N control devices determine a communication channel that is less susceptible to interference or disturbance by searching for the presence or absence of interference or disturbance in each of a plurality of communication channels different from the communication channel, and transmit a change instruction to the remote control terminal paired with the device itself to instruct the device to change to the determined communication channel. It may be characterized by the fact that

[0010] A more preferable communication system according to a fifth aspect is the communication system according to the fourth aspect, The control device that transmitted the change instruction returns a response when it receives data from a remote control terminal paired with the control device through wireless communication on the communication channel that instructed the change, completing the change of the communication channel when the remote control terminal that has changed the communication channel and transmitted the data in response to the change instruction receives the response; It may be characterized by the fact that

[0011] A more preferable communication system according to a sixth aspect is the fifth communication system, When the control device that transmitted the change instruction fails to receive data from the remote control terminal device paired with itself a predetermined number of times by wireless communication on the communication channel for which the change instruction has been instructed, or fails to receive data from the remote control terminal device paired with itself within a predetermined time period since the transmission of the change instruction, the control device returns to the original communication channel and repeats the process of transmitting the communication channel change instruction again a predetermined number of times, and when the communication channel change is not successful even after repeating the process a predetermined number of times, the control device returns to the original communication channel or searches the multiple communication channels again and transmits the change instruction to a different communication channel. It may be characterized by the fact that

[0012] In addition, a communication system according to another preferred seventh aspect is the communication system according to the second aspect, When the N control devices detect interference or disturbance in a communication channel used for wireless communication with a remote control terminal device paired with the own device, the N control devices transmit a change instruction to the remote control terminal device paired with the own device, instructing the change of the communication channel; the control unit included in each of the N remote control terminal devices changes the communication channel used for transmitting data to the control device paired with the respective device in response to the change instruction; It is characterized by:

[0013] A more preferable communication system according to an eighth aspect is the communication system according to any one of the first to seventh aspects, Each of the N remote control terminal devices is a remote controller for remotely operating N different operation target devices, and each of the N control devices is included in each of the N operation target devices; Each of the N control devices transmits a response in response to an instruction received from a maintenance terminal that performs remote maintenance of the operation target devices including the control device itself to a remote control terminal device paired with the control device itself; the control units in the N remote control terminal devices execute processing in accordance with the responses received via the wireless communication units. It may be characterized by the fact that

[0014] The remote control terminal device of the present disclosure includes: a wireless communication unit that transmits data to a control device paired with the device itself by wireless communication on a predetermined communication channel; The wireless communication device further includes a control unit that adjusts the timing of the wireless communication performed by the wireless communication unit by adding an offset corresponding to a random number to a timing determined according to a predetermined cycle. [Brief explanation of the drawings]

[0015] [Figure 1] FIG. 1 is a diagram illustrating an example configuration of a communication system 1 according to an embodiment of the present disclosure. [Figure 2] FIG. 2 is a diagram showing an example of communication channel allocation in the communication system 1. As shown in FIG. [Figure 3] FIG. 3 is a diagram showing an example of the configuration of the remote control terminal device 10. As shown in FIG. [Figure 4] FIG. 4 is a diagram showing an example of the format of a communication message transmitted from the remote control terminal device 10 to the control device 20. As shown in FIG. [Figure 5] FIG. 5 is a diagram for explaining burst transmission performed by the remote control terminal device 10. In FIG. [Figure 6] FIG. 6 is a diagram showing an example of an execution period of burst transmission by the remote control terminal device 10. In FIG. [Figure 7] FIG. 7 is a graph showing the relationship between the transmission interval T2 (ms) and the time (ms) required to clear the call loss rate standard. [Figure 8] FIG. 8 is a flowchart showing the flow of processing after burst transmission that is executed by the control unit 110 of the remote control terminal device 10 according to a control program. [Figure 9] FIG. 9 is a flowchart showing an example of the operation of the control device 20 when disturbance or interference is detected in a communication channel used for wireless communication with the remote control terminal device 10. [Figure 10] FIG. 10 is a diagram showing actual measurement values ​​of the D / U ratio and the call loss rate between terminals when collision occurs over the air in the communication system 1. In FIG. DETAILED DESCRIPTION OF THE INVENTION

[0016] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. Note that numerical values ​​and the like in the embodiments are examples and are not intended to limit the scope of the present disclosure.

[0017] <1. Embodiment> FIG. 1 is a diagram illustrating an example configuration of a communication system 1 according to an embodiment of the present disclosure. As shown in FIG. 1, the communication system 1 includes M communication pairs, namely, communication pairs P(1) to P(M) (M is an integer equal to or greater than 1, and M=160 in this embodiment). A communication pair refers to a pair of a remote control terminal device and a control device that perform wireless communication in accordance with a predetermined wireless communication standard such as the IEEE802.15 series. In this embodiment, the wireless communication standard adopted is IEEE802.15.4 MAC, which is one of the specified low-power wireless communication standards. In the previous method of assigning a dedicated communication channel to each pair of remote control and device to be operated, the specified low-power wireless communication method (wireless equipment in the 400 MHz band with an occupied frequency bandwidth of 8.5 kHz or less) had 46 communication channels, meaning the upper limit for the system was 46 devices, while the previous specified low-power wireless communication method (wireless equipment in the 1200 MHz band with an occupied frequency bandwidth of 16 kHz or less) had 40 communication channels, meaning the upper limit for the system was 40 devices.However, this method allows 160 devices to operate in the system without a controlling parent device, and is also more resistant to interference, so the ratio of the number of devices accommodated is more effective than the numerical ratio.

[0018] The communication pair P(1) includes a control device 20 and a plurality of remote control terminal devices, such as a remote control terminal device 10A, a remote control terminal device 10B, a remote control terminal device 10C, and a remote control terminal device 10D. FIG. 1 illustrates a case in which the communication pair P(1) includes two remote control terminal devices. As shown in FIG. 1, the communication pair P(1) in this embodiment includes the remote control terminal device 10A and the control device 20, and the remote control terminal device 10B and the remote control terminal device 10C are stored as spares in case of a failure of the remote control terminal device 10A, or are installed as multi-operation devices. Hereinafter, when it is not necessary to distinguish between the remote control terminal device 10A and the remote control terminal device 10B, each of the remote control terminal devices 10A, 10B, 10C, etc. will be referred to as a "remote control terminal device 10." 1, each of the communication pairs P(2) to P(M) includes one remote control terminal device 10 and one control device 20 that is paired with the remote control terminal device 10. The remote control terminal device 10 and the control device 20 included in one communication pair form one PAN (Personal Area Network).

[0019] The control device 20 is a communication module provided in a target device, such as a crane or shutter installed in a factory or indoors. The remote control terminal device 10 is a remote controller for remotely controlling the device in which the control device 20 is provided by wirelessly communicating with the control device 20 that forms a communication pair in accordance with a predetermined wireless communication standard. Hereinafter, the device including the control device 20 is referred to as the "target device." The control device 20 waits for a command transmitted from the remote control terminal device 10 and drives the target device according to the received command. In this embodiment, data may be transmitted from the control device 20 to the remote control terminal device 10. Specifically, the control device 20 transmits to the remote control terminal device 10 an instruction and response to change the communication frequency for the purpose of avoiding interference, and a response to an instruction from a maintenance terminal.

[0020] In the communication system 1, K (K is an integer equal to or greater than 1, K=16 in this embodiment) communication channels defined in the wireless communication standard mentioned above are available for use. FIG. 2 is a diagram showing an example of communication channel allocation in this embodiment. As shown in FIG. 2, in this embodiment, communication channels #1 to #16 are available for use, and N (N is an integer equal to or greater than 1 and equal to or less than M, N=10 in this embodiment) communication pairs are allocated to one communication channel, and the communication channel is shared by these N communication pairs. Hereinafter, the number of communication pairs sharing one communication channel is referred to as the "number of shared pairs." The number of shared pairs in this embodiment is N.

[0021] Specifically, as shown in Fig. 2, communication pairs P(1) to P(10) are assigned to communication channel #1. Although detailed illustration is omitted in Fig. 2, communication pairs P(11) to P(20) are assigned to communication channel #2, communication pairs P(21) to P(30) are assigned to communication channel #3, communication pairs P(31) to P(40) are assigned to communication channel #4, communication pairs P(41) to P(50) are assigned to communication channel #5, communication pairs P(51) to P(60) are assigned to communication channel #6, and communication pairs P(61) to P(70) are assigned to communication channel #7. Communication pair P(71) to P(80) are assigned to communication channel #8, communication pair P(81) to P(90) to communication channel #9, communication pair P(91) to P(100) to communication channel #10, communication pair P(101) to P(110) to communication channel #11, communication pair P(111) to P(120) to communication channel #12, communication pair P(121) to P(130) to communication channel #13, communication pair P(131) to P(140) to communication channel #14, communication pair P(141) to P(150) to communication channel #15, and communication pair P(151) to P(160) to communication channel #16.

[0022] When a first communication pair and a second communication pair share a single communication channel, if the data transmission timing of the first communication pair and the data transmission timing of the second communication pair overlap, the respective communications may be successful or may fail due to collision of their respective communication radio waves. In other words, when a first communication pair and a second communication pair share a single communication channel, the communications of each communication pair may not always be successful. For this reason, when remotely controlling a target device via wireless communication, it has traditionally been considered best to assign a dedicated communication channel to each communication pair and allow that communication pair to occupy that communication channel. This is because collision of communication radio waves does not occur when a dedicated communication channel is assigned to each communication pair and that communication pair occupies that communication channel.

[0023] In contrast, in this embodiment, by devising a transmission method for the remote control terminal device 10, it is possible to realize remote control of the target device by wireless communication without allocating a dedicated communication channel for each communication pair (i.e., without occupying the communication channel for the communication pair), and without impeding safety assurance and quick response in the event of an abnormality. The following description will focus on the remote control terminal device 10, which prominently exhibits the features of the present disclosure.

[0024] Fig. 3 is a diagram showing an example of the configuration of the remote control terminal device 10. As shown in Fig. 3, the remote control terminal device 10 includes a control unit 110, an operation unit 120, a notification unit 130, a wireless communication unit 140, and a storage unit 150. Although not shown in detail in Fig. 3, the remote control terminal device 10 also includes a power supply unit that supplies operating power to each of the control unit 110, the operation unit 120, the notification unit 130, the wireless communication unit 140, and the storage unit 150. Specific examples of the power supply unit include a storage battery such as an alkaline battery or a secondary nickel-metal hydride battery.

[0025] The control unit 110 is, for example, a CPU (Central Processing Unit). The control unit 110 functions as the control center of the remote control terminal device 10 by operating in accordance with a control program PR stored in the storage unit 150. Details of the processing executed by the control unit 110 in accordance with the control program PR will be made clear later.

[0026] The operation unit 120 includes, for example, multiple operators. A user of the remote control terminal device 10 (a person in charge of remotely controlling the target device) operates the multiple operators included in the operation unit 120 to perform various inputs for remotely controlling the target device. The operation unit 120 outputs operation content data indicating the content of the operation input by the user to the control unit 110. As a result, the user's operation content is transmitted to the control unit 110. The notification unit 130 includes, for example, multiple light-emitting diodes (LEDs) each emitting a different light color, and causes these multiple LEDs to emit light under the control of the control unit 110. In this embodiment, the status of the remote control terminal device 10 is notified to the user by a combination of the multiple LEDs to be lit. The notification unit 130 may include a display device that displays characters or images, such as a liquid crystal display, in addition to or instead of the multiple LEDs. When the notification unit 130 includes a display device, a touch sensor may be used as the operation unit 120, and the touch sensor and the display device may form a so-called touch panel.

[0027] The wireless communication unit 140 is, for example, a wireless communication transceiver, and transmits a communication message conforming to, for example, IEEE802.154 MAC to the control device 20 by wireless communication. FIG. 4 is a diagram showing an example of a format of a communication message in this embodiment. As shown in FIG. 4, this communication message has a header and a payload following the header. Note that a communication message conforming to IEEE802.154 MAC includes a preamble preceding the header, but the preamble is not shown in FIG. 4.

[0028] As shown in FIG. 4, the header includes a sequence number, a PAN-ID, a destination address, and a source address. The sequence number is a serial number ranging from 0x00 to 0xFF that is incremented each time a communication message is sent. The PAN-ID is identification information that uniquely identifies the PAN (in other words, the communication pair) to which the remote control terminal device 10, which is the source of the communication message, belongs. This ensures uniqueness and enables the formation of a communication pair without confusion. The uniqueness is maintained by writing the PAN-ID to the storage unit 150 when the remote control terminal device 10 is shipped from the factory, or by writing it externally using a physical switch or data. The destination address is the communication address of the control device 20, which is the destination of the communication message, and the source address is the communication address of the remote control terminal device 10, which is the source of the communication message. In addition to the PAN-ID, the destination address and source address further ensure the uniqueness of the communication pair, enabling the formation of a communication pair without confusion. Note that any format is acceptable as long as it indicates the communication pair number and the source and destination addresses.

[0029] As shown in Fig. 4, the payload includes a message version number and preliminary information. The message version number is information indicating the version of the communication message, and the control device 20 can change the interpretation of the command information and preliminary information depending on the value of the message version number. In this embodiment, the preliminary information is not used, but it can be used to transmit information about the communication channel or the remaining battery level of the remote control terminal device 10 to the control device 20. For example, by transmitting the remaining battery level of the remote control terminal device 10 to the control device 20, it becomes possible to cause the control device 20 to issue a notification regarding, for example, battery replacement of the remote control terminal device 10.

[0030] The wireless communication unit 140 receives data representing a communication message from the control unit 110, and transmits the data by superimposing it on a carrier wave of a communication channel assigned to the remote control terminal device 10. This patent covers various superimposing methods. In this embodiment, either FM modulation or spread spectrum may be used, but spread spectrum, which is more resistant to demodulation during collisions, is used. When the control device 20 receives a communication message via the communication channel assigned to the control device 20, it reads the PAN-ID and destination address from the header of the communication message. If the former matches the PAN-ID of the PAN to which the control device 20 belongs and the latter matches the communication address of the control device 20, the control device 20 receives the communication message as a communication message addressed to the control device 20 and controls the operation of the target device according to the command written in the command information in the payload of the message.

[0031] The storage unit 150 includes a nonvolatile storage unit 152 and a volatile storage unit 154. The nonvolatile storage unit 152 is, for example, a flash ROM (Read Only Memory). The nonvolatile storage unit 152 stores a control program PR and a random number table TBL. The random number table TBL pre-stores a random number sequence in which a plurality of real numbers are arranged. Although not shown in detail in FIG. 3, the nonvolatile storage unit 152 also stores a PAN-ID, a communication address assigned to the device itself, and a communication address assigned to a control device 20 that forms a communication pair with the device itself. The volatile storage unit 154 is, for example, a RAM (Random Access Memory). The volatile storage unit 154 is used by the control unit 110 as a work area when executing the control program PR.

[0032] When the remote control terminal device 10 is powered on, the control unit 110 reads the control program PR from the nonvolatile storage unit 152 to the volatile storage unit 154 and begins executing the control program PR. Operating in accordance with the control program PR, the control unit 110 performs burst transmission, preferably intermittently and periodically, over a predetermined command transmission time T1 on a communication channel. The burst transmission includes commands that instruct the controlled device, such as a crane, to operate. Thereafter, until the next command is input, the control unit 110 repeatedly executes burst transmission of the communication message while adjusting the execution timing based on a predetermined period (hereinafter referred to as the basic period T2) by adding an offset corresponding to a random number. The random number is converted so that the offset averages zero, and both positive and negative values ​​are used. During the period from the completion of a burst transmission to the start of processing for the next burst transmission (the period T2 + offset time - T1 - T3 in FIG. 6), the control unit 110 operates in a power-saving mode (sleep mode) to reduce power consumption. Assuming that the device wakes up from sleep mode at time t1, during the processing time T3 from time t1 to the start of command transmission and the command transmission time T1, the control unit 110 performs processing necessary for a wireless communication device equipped with a control unit, such as processing operation content data, detecting the device status and faults and processing them.

[0033] FIG. 5 shows an example of burst transmission performed by the remote control terminal device 10, and FIG. 6 shows an example of the execution period of burst transmission by the remote control terminal device 10. In this embodiment, the command transmission time T1 is 0.8 milliseconds, and the basic period T2 is 20 milliseconds. The processing time T3 until the start is 0.2 milliseconds, and the control unit enters sleep mode after performing the necessary processing for the total of T3 and T1, 1 millisecond. The offset in this embodiment may be a value ranging from -19 milliseconds to 19 milliseconds. For example, if the stability of the 20-millisecond monitoring period is emphasized, a value ranging from -2 milliseconds to 2 milliseconds may be used. For example, if the randomness of collision avoidance is emphasized, a value ranging from -19 milliseconds to 19 milliseconds may be used. The offset value may be a continuous analog value, a multiple of the T1 period (1 millisecond), or half that (0.5 milliseconds). The offset value is determined based on the importance of the requirements of the system to which it is applied, such as the probability of collision avoidance, period stability, and device cost. In this embodiment, the timing of burst transmission is not preset for each of the N remote control terminal devices 10 sharing a single communication channel. Instead, each remote control terminal device 10 immediately executes burst transmission in response to a user's operation (in other words, burst transmission is executed randomly). Strictly speaking, the communication system 1 according to an embodiment of the present disclosure employs an Aloha system that eliminates the ACK transmission function of the receiving control device from the Aloha system. Examples of a mode in which the timing of burst transmission in each remote control terminal device 10 is preset include a time division slotted Aloha system in which N equal slots of a basic cycle are assigned to each of the N remote control terminal devices 10 in a one-to-one relationship, and each remote control terminal device 10 executes burst transmission in its assigned slot. The slotted Aloha system reduces the collision probability by half compared to the Aloha system, thereby enabling collision avoidance, but requires the remote control terminal device 10 to have a function for reading the slot cycle timing. The slot cycle timing can be adjusted during or after power-on.When performed after startup, the slot synchronization time is adjusted by detecting signals from other communication pairs on the communication channel to which the device belongs. If multiple communication pairs exist, the slot synchronization time is adjusted to match the slot period timing of the communication pair with the strongest radio wave strength. When performed after startup, sleep is stopped periodically every few seconds, minutes, or hours to perform a search and adjust the slot period timing. Alternatively, in this embodiment, this is achieved by transmitting a slot timing signal of 1 millisecond or a frame timing signal of 20 milliseconds every regular period, such as 1 second, from the control device 20, and the remote control terminal device 10 then searches and adjusts the slot period timing.

[0034] In this embodiment, the control unit 110 reads a random number from the random number table TBL and generates an offset value from this random number. When the offset value is set in units of 1 millisecond, which is a multiple of the period of T1, and within the range of -4 milliseconds to 4 milliseconds, the random number is divided by 9 and 4 is subtracted from the remainder to generate offset values ​​of -4, -3, -2, -1, 0, 1, 2, 3, and 4. The random numbers may be read from the random number sequence stored in the random number table TBL in a manner such that they are read one by one from the beginning of the random number sequence, or may be read from a read position (address) that is converted by performing a predetermined calculation based on the current time.

[0035] In this embodiment, random numbers stored in the random number table TBL are used. However, pseudo-random numbers generated according to a well-known pseudo-random number generation algorithm may be used instead to generate an offset. In other words, the random numbers in this disclosure include pseudo-random numbers generated according to a pseudo-random number generation algorithm. Specific examples of pseudo-random number generation algorithms include a linear congruential generation algorithm and a Mersenne Twister generation algorithm. In an aspect in which an offset is generated using pseudo-random numbers, a device identifier unique to each remote control terminal device 10, such as a serial number such as a product number assigned by the manufacturer of the remote control terminal device 10, may be used as a seed in the pseudo-random number generation algorithm or as data from which the seed is generated.

[0036] The reason for adjusting the timing of burst transmission by adding an offset according to a random number is as follows: As described above, in the example of this embodiment, IEEE802.15.4 MAC is adopted as the wireless communication standard for the communication pairs, and the distance at which the remote control terminal device 10 and the control device 20 can communicate wirelessly without any problems in IEEE802.15.4 MAC is assumed to be L. Then, assume that the control device 20 of communication pair P(2) is located within a circle of radius L centered around the control device 20 of communication pair P(1), and that each of the remote control terminal devices 10 of communication pair P(1) and communication pair P(2) is located within the circle.

[0037] Under these circumstances, suppose that at time t0, the execution timing of burst transmission in communication pair P(1) and the execution timing of burst transmission in communication pair P(2) overlap, causing both pairs to fail to communicate wirelessly due to a collision of communication radio waves. In communication pair P(1), burst transmission is again performed at a timing adjusted 20 milliseconds after time t0 by adding an offset according to random number R1 read from the random number table TBL of the remote control terminal device 10 included in communication pair P(1). Meanwhile, in communication pair P(2), burst transmission is again performed at a timing adjusted 20 milliseconds after time t0 by adding an offset according to random number R2 read from the random number table TBL of the remote control terminal device 10 included in communication pair P(2).

[0038] The contents stored in the random number table of the remote control terminal device 10 included in the communication pair P(1) are different from the contents stored in the random number table TBL of the remote control terminal device 10 included in the communication pair P(2), and the random number R1 at time t0 is different from the random number R2. Therefore, the next burst transmission in the communication pair P(1) and the next burst transmission in the communication pair P(2) are executed at timings based on different random number generation values, and a second failure of both can be avoided with a probability of 7 / 9 (Aloha method). Even if there is another collision with a probability of 2 / 9, the next random number will result in a success rate of 1-(2 / 9). 2Two consecutive collisions can be avoided with a probability of T = 77 / 81. To make the calculation easier to understand, we will assume T2 = 20 ms, T1 = 0.8 ms, and a completely random transmission ALOHA system, and consider the probability when two communication pairs are in an interfering position. We will make the strict assumption that if the transmission times of the communication pairs overlap even slightly, a call will be lost.

[0039] The probability that one communication pair will be dropped due to another communication pair per transmission, P 11 , and the probability of two consecutive call losses P 12 are as follows, respectively: P 11 =1.6ms / 20ms=0.08=8%. P 12 =(P 11 ) 2 =0.64%.

[0040] As a worst case scenario, consider a situation where there are 10 communication pairs on one communication channel. The probability that one communication pair will be dropped per transmission due to the other 9 communication pairs is P 91 , and the probability of two consecutive call losses P 92 are as follows, respectively: P 91 =1-(1-P 11 ) 9 ≒0.528=53%. P 92 =(P 91 ) 2 =28%.

[0041] Since transmissions are made every 20 milliseconds, the probability of six consecutive call losses, i.e., the probability of not being able to connect for 100 milliseconds, is P 96 , the probability of 11 consecutive call losses, i.e., the probability of not being able to connect for 200 milliseconds, P 911 , the probability of 21 consecutive call losses, i.e., the probability of not being able to connect for 400 milliseconds, P 921 , and the probability of 26 consecutive call losses, i.e., the probability of not being able to connect for 500 milliseconds, P 926 are as follows, respectively: P 96 =(P 91 ) 6≒0.0216=2.2%. P 911 =(P 91 ) 11 =0.08%. P 921 =(P 91 ) 21 =1.5 ppm. P 926 =(P 926 ) 11 =0.06 ppm. These can be interpreted as the probability of a signal delay due to a collision. In other words, the probability of a signal being delayed by 500 milliseconds or more is 0.06 ppm.

[0042] The above calculations are based on the worst-case conditions. In reality, 10 communication pairs on the same communication channel will interfere with each other when 160 communication pairs are concentrated within a radius of L. When L = 50 m, the interference rate is 49(7 2 )m 2 This is the density where there is one communication pair of remote control terminal devices on the same channel. This does not include the calculation of collision avoidance due to the difference in wireless reception level caused by the difference in distance, so in reality the installation density is even higher. 11 However, when using the spread spectrum method conforming to IEEE802.15.4 MAC, the actual value is P 11 = 2%. 91 =16.6%. Probability of not being able to connect for 100 milliseconds P 96 = 21 ppm, probability of not being able to connect for 140 ms P 98 = 0.6 ppm. 11 = 2%, the probability of not being able to connect for 140 ms is 0.6 ppm. 11 This is lower than the 1.5 ppm probability of not being able to connect for 400 milliseconds when the rate is 8%, and is a significantly better value.

[0043] P 11 = 2%, P 96 =(P 91 ) 6 = 21 ppm, the probability of a signal delay of 100 ms or more is 21 ppm, and P 911 =(P91 ) 11 = 0.0027 ppm, the probability of a signal delay of 200 milliseconds or more is 0.0027 ppm, which is a delay level that will not cause any problems in practical operation in terms of safety or immediacy.

[0044] If the system requires a shorter delay time, the P 11 The delay time is reduced by half, resulting in a significant reduction in delay time. 11 =2% to P 11 = 1%, so P 96 The probability of 21 ppm is reduced from 21 ppm to 0.4 ppm. The probability of 21 ppm is reduced from 100 ms to 68 ms. The time to reach a 0.1% call blocking rate is reduced from 57 ms to 36 ms.

[0045] There are various methods to reduce delay time. Examples (1) to (7) are shown below. Physical measures such as (1) reducing the number of units and (2) increasing the physical distance between communication pairs are effective. Other methods include (3) creating a unique, optimized protocol that eliminates unnecessary information elements and shortens the wireless signal output time, T1. Other methods include (4) setting T2 = 20 ms for only 1 second from the point of change when a button is pressed or released, and setting T2 = 100 ms if there is no change. (5) For important signals requesting power operation while a button is pressed, setting T2 = 20 ms for only 1 second from the point of change when the button is pressed and released, and setting T2 = 200 ms if there is no change after the button is released. (6) Although both the remote control terminal and the control device have wireless transmission and reception capabilities, which is costly, another method involves continuous transmission at intervals of, for example, T2 = 20 ms when a change occurs when a button is pressed or released. The control device returns an ACK signal when the remote control terminal receives the signal, and once the remote control terminal receives it, transmission from the remote control control device stops. From a safety perspective, a configuration in which the power is turned off if the signal is interrupted for more than 500 ms is also considered. In this embodiment, T2 is set to 20 milliseconds. However, this is not the optimal value for reducing the collision probability and minimizing the transmission delay time due to the number of communication pairs that may collide. For this reason, there is a method (7) for optimizing T2.

[0046] We will explain how to determine the optimum value of T2 to shorten the delay time. For example, if the time when the call loss rate becomes 0.1% is defined as t0.1%, the following function is obtained. Assume that N communication pairs in the Aloha system cause interference. t0.1%=T2*[-3 / log{1-(1-2*T1 / T2) N-1}-1]

[0047] When determining the shortest time, T1, N, and the call loss rate are fixed, and T2 is varied. In this embodiment, an example is given in which N≦10, T1=0.8 ms, and T2=20 ms. When N = 3, the shortest time for a call blocking rate of 0.01% is 64.1 ms, and this is the condition T2 = 7.7 ms. When T2 = 20 ms, the shortest time increases to 78.3 ms. When N = 3, the shortest time for a call blocking rate of 1% is 27.6 ms, and this is the condition T2 = 10.5 ms. When T2 = 20 ms, the shortest time increases to 29.2 ms. When N = 10, the shortest time for a call blocking rate of 0.1% is 189.59 ms, and this is the condition T2 = 28.5 ms. When T2 = 20 ms, the shortest time increases to 196.2 ms. FIG. 7 shows a graph of T2=transmission interval (ms) vs. clearing time (ms) based on the call loss rate. In Figure 7, the horizontal axis corresponds to the transmission interval (ms), which is T2, and the vertical axis corresponds to the time (ms) required to clear the call loss rate criterion. Curves G1, G2, and G3 in Figure 7 show the relationship between the transmission interval (ms) and the clearing time (ms) for the call loss rate criterion when N=5, T1=0.8 ms, and the call loss rate=1%, 0.1%, and 0.01%, respectively. Curves G4, G5, and G6 in Figure 7 show the relationship between the transmission interval (ms) and the clearing time (ms) for the call loss rate criterion when N=10, T1=0.8 ms, and the call loss rate=1%, 0.1%, and 0.01%, respectively. Curves G7, G8, and G9 in FIG. 7 show the relationship between the transmission interval (ms) and the clearing time (ms) based on the call loss rate when N=3, T1=0.8 ms, and call loss rates=1%, 0.1%, and 0.01%, respectively.

[0048] In the case of the slotted aloha system, the formula is as follows: t'0.1%=T2*[-3 / log{1-(1-T1 / T2) N-1}-1]

[0049] In this embodiment, the offset value is set in 1 millisecond increments, which is a multiple of the T1 cycle, and is set in 9 steps of ±4 milliseconds. The recollision probability is 21%. If the offset is set to 17 steps of ±8 milliseconds, the periodicity is lost, collisions with multiple cycles occur, and complexity increases, but the recollision probability decreases to 12%. If periodicity is important, a setting of 3 steps of ±1 millisecond is better, but the recollision probability increases to 56%.

[0050] For the above reasons, there is a method (8) of changing the width of the offset value. This section explains a method for changing the width of the offset value to shorten the delay time. In this embodiment, the offset value is set in 1 millisecond units, which are multiples of the T1 period, in the ALOHA method, and is set in the range of -4 milliseconds to 4 milliseconds. In this case, the probability that two communication pairs using the same channel will collide again after colliding once is calculated as 2 / 9. A detailed calculation shows that 1 / 9*2 / 9*8+1 / 9*2 / 9*1=17 / 81=0.210<0.222=2 / 9, and the call loss rate is slightly smaller. In this example, the range was ±4 milliseconds, but in the ±u millisecond range, the collision probability is (4u+1) / (2u+1) 2 However, T2 is 20 milliseconds and u<7. When u is 7 or more, the calculation formula changes because collisions during multiple cycles are calculated. When u=7~9, the collision probability is (4u+1) / (2u+1) 2 +{6*(u-6)*(3u-19)+1} / 2 / (2u+1) 3 is. When u=1, the probability of a re-collision after a collision is 0.556 When u=2, the probability of a re-collision is 0.360 When u=3, the probability of a re-collision is 0.265 When u=4, the probability of a re-collision is 0.210 When u=5, the probability of a re-collision is 0.174 The probability of a re-collision when u=6 is 0.148 The probability of a re-collision when u=7 is 0.131 The probability of a re-collision when u=8 is 0.120 The probability of a re-collision when u=9 is 0.113 When u=10, the probability of a re-collision is 0.107 For a call that occurs completely randomly 1 / 20 of the time, the probability is 2 / 20 = 0.100. By changing the offset value as described above, it is possible to reduce the probability of re-collision, the call loss rate, and the delay time. On the other hand, the fixed periodicity tends to be lost.

[0051] The method for reducing the delay time has been described above. On the other hand, if the importance of the requirements for the system to be applied increases and a demand arises for an increased number of devices to be accommodated in the system, the same considerations as for measures to reduce delay time should be carried out and the method should be changed.

[0052] The above is the configuration of the remote control terminal device 10.

[0053] Next, the operation of the remote control terminal device 10 will be described.

[0054] When a button for remotely operating a controlled device (for example, a crane) is operated on the operation unit 120, the control unit 110, operating according to the control program PR, burst-transmits a communication message including a command corresponding to the operation (hereinafter referred to as a first command) to the control device 20, and after the burst transmission is completed, executes the control method shown in Fig. 8. As shown in Fig. 8, this control method includes the processes of steps SA110 to SA150. The process contents of each process of steps SA110 to SA150 are as follows.

[0055] In step SA110, control unit 110 acquires a random number by referring to the random number table TBL of its own device. When the process of step SA110 is executed again, control unit 110 reads the random number from a read position different from that used in the previous execution of step SA110.

[0056] In step SA120 following step SA110, the control unit 110 converts the random number acquired in step SA110 into an offset, for example, in the range of -4 to 4, adds a time T2 corresponding to the period to the offset, and sets the value obtained by subtracting T1 and T3 as the sleep time.

[0057] Next, when control unit 110 receives a burst transmission completion notification from wireless communication unit 140 (step SA130), it executes a sleep for the sleep time set in step SA120 (step SA140). After the sleep time has elapsed, control unit 110 executes a start-up process (step SA150).

[0058] In the burst transmission after the flowchart in Figure 8 is completed, the control unit 110 checks the input value of the button state on the operation unit 120, and if there is no change in the button operation, it only needs to burst transmit the same communication message as last time.If there is a change in the button operation and the input value has changed, it only needs to reset the communication message in accordance with the operation on the operation unit 120 and perform burst transmission.

[0059] If the control device 20 determines that it is better to change the communication channel due to reasons such as the detection of an interference wave or jamming wave in a predetermined communication channel, the control device 20 executes the operation shown in the flowchart of FIG. 9. When an interference wave or jamming wave is detected in a predetermined communication channel, the control device 20 searches communication channels #1 to #16 as shown in FIG. 9 and determines a communication channel that is less susceptible to interference or jamming as the new communication channel (step SB110). Next, the control device 20 transmits an instruction to change the communication channel to the new communication channel to the remote control terminal device 10 (step SB120). When the control unit 110 of the remote control terminal device 10 receives an instruction to change the communication channel, i.e., an instruction to change the communication frequency, from the control device 20 paired with the control device 20, the control unit 110 changes the communication channel in accordance with the instruction and executes a burst using the new communication channel. The control device 20 waits for reception of data transmitted in a burst on the new communication channel (step SB130). If data is received on the new communication channel (step SB130: Yes), the control device 20 transmits a response to the new communication channel (step SB140). The change of the communication channel is completed when the remote control terminal device 10 receives the response. If the control device 20 does not receive data even after a predetermined time has elapsed since the transmission of the change instruction, the determination result of step SB130 is "No," and in the operation example shown in Fig. 9, the control device 20 executes the processing from step SB110 onwards again.

[0060] Alternatively, after changing the remote control terminal device 10 to the maintenance mode, a signal instructing the control device 20 to change from a predetermined communication channel to a different communication channel may be sent by operating a button or by setting it from a maintenance terminal. When the control device 20 receives the signal, it returns a response signal. Thereafter, the control device 20 and the remote control terminal device 10 change to the new communication channel, and the remote control terminal device 10 transmits a burst signal and returns a response, completing the change. The remote control terminal device 10 may be a dedicated maintenance device. Note that, in the maintenance mode of the remote control terminal device 10, a function may be provided to search communication channels #1 to #16 and display the degree of impact of interference or disturbance, or to transmit the degree of impact to the control device 20 or the maintenance terminal. If the control device 20 does not receive a response signal from the remote control terminal device 10 a predetermined number of times or after waiting a predetermined time since transmitting the change instruction, the control device 20 may return to the original channel and repeat the process of transmitting the change instruction again a certain number of times. If the channel change is not successful even after repeating this process a predetermined number of times, the algorithm may return to the original channel, or search communication channels #1 to #16 again and issue an instruction to change to a different channel.

[0061] In addition, a possible method is for a maintenance mode, a dedicated maintenance remote control terminal, or a maintenance terminal to indicate to the control device an identifier indicating that the signal is a maintenance signal with backup information set to FF or a source address set to FF. When a destination address is specified, only the control device of that address processes the maintenance signal, and when the destination address is FF, all control terminals recognize the identifier as a maintenance instruction, and all terminals receive the maintenance signal. When an operation target device including the control device 20 receives an instruction from a maintenance terminal that performs remote maintenance of the operation target device, executes processing according to the instruction, and returns a response to the maintenance terminal, the control device 20 transmits the response to the remote control terminal device 10 that is paired with the control device itself. When the control unit 110 in the remote control terminal device 10 receives the response, it executes processing according to the response, such as canceling any burst transmission currently being performed.

[0062] The specific effects of this embodiment are as follows. 10 is a diagram showing actual measurement values ​​of the D / U ratio and call loss rate between terminals when collision occurs over the air in the communication system 1. As mentioned above, in the communication system 1 according to an embodiment of the present disclosure, the calculated probability of collision between two communication pairs under the strict precondition that a call is always lost when the transmission times of the communication pairs overlap even slightly, with T2=20 ms, T1=0.8 ms, and the ALOHA method with completely random transmission, is P 11 = 1.6ms / 20ms = 0.08 = 8%. Comparing the actual measurements with the calculations, the call loss rate when the D / U ratio between terminals is -3dB or less is 7.2%, which is close to the calculated value.

[0063] The D / U ratio indicates the radio wave strength from the paired remote control terminal device 10 / the radio wave strength from the unpaired remote control terminal device 10 in the received radio wave level received by the control device 20. A D / U ratio of -3 dB between terminals indicates that the radio wave strength from the unpaired remote control terminal device 10 is 3 dB higher than the radio wave strength from the paired remote control terminal device 10, and indicates that when the distance from the paired remote control terminal device 10 to the control device 20 is 3 m, the unpaired remote control terminal device 10 is 2.1 m (√2) from the control device 20.

[0064] Generally, when radio waves collide in wireless communication, if the D / U ratio is 8dB or more, the signal can be regenerated even if there is a collision. In reality, the impact becomes significant when the D / U ratio is 6dB or less, and when it is 3dB or less, there is a complete collision, the signal cannot be regenerated, and a call loss rate calculated based on the collision occurs.

[0065] The communication system 1 according to an embodiment of the present disclosure uses small packets with a data volume of 0.8 milliseconds, including a preamble, and is resistant to collisions due to the effect of using a spread spectrum method, etc. When the D / U ratio is 3 dB or higher, the call loss rate upon collision is 27% of the calculated value, and even at 0 dB, the call loss rate upon collision is small, at around 40% of the calculated value, and when collision occurs at -3 dB or lower, the rate is 90%, close to the calculated value.

[0066] As described above, according to this embodiment, remote control of target devices using a remote controller can be achieved by wireless communication without occupying a communication channel and without interfering with ensuring safety or quickly dealing with an abnormality. Furthermore, in this embodiment, even if N communication pairs sharing one communication channel exist within a circle with a radius of L, which is the effective range of wireless communication, this does not interfere with ensuring safety or quickly dealing with an abnormality. Therefore, there is no need to visit the factory to perform investigations, measurements, and configuration work, such as ensuring that the same communication channel is not assigned to adjacent target devices in accordance with the layout of the target devices in the factory, and the introduction cost of the communication system 1 can be reduced compared to an embodiment that requires such work.

[0067] Specifically, 10 communication pairs (P1-P10) can share communication channel #1. With 16 communication channels, 160 pairs can be used in the same location. The remote control terminal device 10 included in each of the communication pairs P1-P10 transmits signals intermittently (0.8 ms) and periodically (20 ms). Signal collisions are avoided by transmitting signals with a predetermined period offset by a random number. Although signal collisions do occur among the 10 pairs, signals are transmitted to the control device with a certain probability. The collision probability and call loss rate, which are determined by the number of devices accommodated and the distance between the communication pairs, are further converted into functions of the control delay time. Because this system allows for the coexistence of 10 pairs even on the same channel, 160 pairs—approximately four times the number previously available—can be used, and no adjustments by a radio engineer are required. Operation is possible simply by installing equipment randomly configured in the factory. The number of pairs and period used here are merely examples; even more communication pairs can be accommodated. This method can be optimized to meet requirements such as control delay time constraints, the number of devices accommodated, and cost requirements by adjusting the transmission cycle time (T2) and the width of the transmission timing offset value.It can also be optimized to meet requirements by selecting between ALOHA and Slotted ALOHA methods, whether to enable or disable responses from control devices, and whether to enable or disable a channel change function.

[0068] <2. Transformation> The above description of the embodiments is for the purpose of explaining the present disclosure and should not be construed as limiting the invention described in the claims or narrowing its scope. Furthermore, the configurations of the various parts of the present disclosure are not limited to the above embodiments, and various modifications are possible within the technical scope described in the claims.

[0069] (1) In the above embodiment, the equipment to be operated was a crane installed in a factory, but it may also be a hoist, winch, or chain block. It may also be a fire shutter whose opening and closing is controlled by a remote control, control of a pump for medical use, control of agricultural equipment, or control of an air conditioner, a mobile cart, or a robot. Control includes not only start and stop, but also speed control, selection switch control, emergency stop control, etc. It may also be powered or unpowered control of a personal computer, display, television, lighting system, etc.

[0070] (2) In the above embodiment, the contents stored in the random number table TBL of each of the N communication pairs sharing one communication channel were different from one another. However, it is not necessary that the contents stored in these N random number tables TBL be different from one another; multiple (including N) of these tables may be identical. If the N random number tables TBL include identical tables, adjusting the read position for each remote control terminal device 10 based on a device identifier does not pose any particular problem. In other words, the communication system disclosed herein includes N pairs of remote control terminal devices and control devices (N is an integer greater than or equal to 1), each of which includes a wireless communication unit that transmits data to its paired control device via wireless communication on a predetermined communication channel, and a control unit that adjusts the timing of the wireless communication by the wireless communication unit by adding an offset corresponding to a random number to a timing determined according to a predetermined cycle. Furthermore, each of the multiple remote control terminal devices is assigned identification information for uniquely identifying it, and the control unit included in each of the multiple remote control terminal devices may generate the random number based on the identification information of its own device.

[0071] (3) The present disclosure may be defined as a program (the control program PR in the above embodiment) that causes a general computer such as a CPU to execute the control method shown in Fig. 8, and the program may be manufactured or provided as a standalone program. Specific ways of providing the program include writing the program to a computer-readable recording medium such as an SD memory card and distributing it, or distributing it by downloading it via a telecommunications line such as the Internet.

[0072] (4) The remote control terminal device 10 transmits bursts in communication with the control device 20, and when communication with the control device 20 is not possible, if a predetermined condition such as the passage of a certain time period is met, the control device 20 can stop the operation of some or all of the controlled devices, for example, stop motor control. Also, the remote control terminal device 10 has wireless communication (bidirectional) with the control device 20, and through this communication the control device 20 can stop the operation of some or all of the controlled devices, for example, stop motor control.

[0073] (5) The communication system 1 of the present invention can adjust the transmission cycle time (T2) to optimize the system to meet requirements such as call loss rate, control delay time, number of devices accommodated, and cost. It can also adjust the width of the transmission timing offset value to optimize the system to meet requirements. Furthermore, it can also adjust and optimize the transmission cycle time (T2) when control changes, when there is no change, or when the system is idle.

[0074] (6) In addition, it is possible to select functions such as the Aloha method or slotted Aloha method, whether or not to have a response from the control device, and the function of changing channels and searching for interference waves, thereby optimizing functionality, performance, and investment costs.

[0075] (7) The communication system 1 of the present invention can provide a highly safe method and system by having a function to automatically turn off the power of the control device or to raise an alarm when the signal from the remote control device is lost for a certain period of time or when interference waves are detected for a certain period of time or more.

[0076] (8) Furthermore, the communication system 1 of the present invention can provide a highly secure method and system by automatically or manually changing channels when it detects a signal interruption or interference from a remote control device for a certain period of time. It can also be equipped with a maintenance mode for forcibly executing investigations and instructions for safe operation. [Explanation of symbols]

[0077] 1. Communication systems 10, 10A, 10B, 10C, 10D...Remote control terminal device 20...Control device 110...Control unit 120...Operation unit 130…Notification department 140...Radio communication unit 150...Storage section 152...Nonvolatile memory unit 154...Volatile memory unit

Claims

1. a communication pair including a remote control terminal device and a control device that wirelessly communicates with the remote control terminal device; Each of the remote control terminal devices a wireless communication unit that transmits data to the control device paired with the device itself via a predetermined communication channel; a control unit that controls the wireless communication unit to transmit wireless communication at a basic transmission cycle T2; having An Aloha or Slotted Aloha communication system, By determining three values ​​from four parameters, namely, the command transmission time T1, the maximum number of communication pairs that can be accommodated N, the basic transmission cycle T2 of the wireless communication, and the probability k that a signal will be delayed for a predetermined time or more, the value of the remaining one can be determined at the time of design. Communication system.

2. The command transmission time T1 can be determined by determining the maximum number of accommodating devices N, the basic transmission cycle T2, and the probability k that the signal will be delayed for a predetermined time or more. The communication system of claim 1 .

3. The maximum number of accommodating vehicles N can be determined by determining the command transmission time T1, the transmission basic cycle T2, and the probability k that the signal will be delayed for a predetermined time or more. The communication system of claim 1 .

4. The basic transmission cycle T2 can be determined by determining the command transmission time T1, the maximum number of accommodating devices N, and the probability k that the signal will be delayed for a predetermined time or more. The communication system of claim 1 .

5. By determining the values ​​of the command transmission time T1, the maximum number of accommodating devices N, and the transmission basic cycle T2, it is possible to determine the probability k that the signal will be delayed for a predetermined time or more. The communication system of claim 1 .

6. the transmission timing of the wireless communication by the wireless communication unit is the transmission basic period T2 plus a random offset time of a maximum width ±u, By determining four values ​​from five parameters, namely, the command transmission time T1, the maximum number of devices that can be accommodated N, the basic transmission cycle T2, the probability k that the signal will be delayed for a predetermined time or more, and the maximum width ±u of the offset time, the value of the remaining one can be determined at the time of design. The communication system of claim 1 .

7. The maximum width ±u of the offset time can be determined by determining the command transmission time T1, the maximum number of accommodating devices N, the basic transmission cycle T2, and the probability k that the signal will be delayed for a predetermined time or more.

7. The communication system according to claim 6.

8. The command transmission time T1 can be determined by determining the maximum number of accommodating devices N, the transmission basic cycle T2, the probability k that the signal will be delayed for a predetermined time or more, and the maximum width ±u of the offset time.

7. The communication system according to claim 6.

9. The maximum number of accommodating vehicles N can be determined by determining the command transmission time T1, the transmission basic cycle T2, the value of the probability k that the signal will be delayed for a predetermined time or more, and the value of the maximum width ±u of the offset time.

7. The communication system according to claim 6.

10. The basic transmission cycle T2 can be determined by determining the command transmission time T1, the maximum number of accommodating devices N, the value of the probability k that the signal will be delayed for a predetermined time or more, and the value of the maximum width ±u of the offset time.

7. The communication system according to claim 6.

11. By determining the values ​​of the command transmission time T1, the maximum number of accommodating devices N, the basic transmission cycle T2, and the maximum width ±u of the offset time, it is possible to determine the probability k that the signal will be delayed for a predetermined time or more.

7. The communication system according to claim 6.

12. the remote control terminal device performs transmission in the Aloha system; The probability that the signal will be delayed for more than a predetermined time is k. ｋ teeth, t ｋ =T2*[log k / log{1-(1-2*T1 / T2) N-1 }-1] is expressed as A communication system according to any one of claims 1 to 11.

13. the remote control terminal device performs transmission in a slotted aloha system; The probability that the signal will be delayed for more than a predetermined time is k. ｋ teeth, t ｋ =T2*[log k / log{1-(1-T1 / T2) N-1 }-1] is expressed as A communication system according to any one of claims 1 to 11.

14. the remote control terminal device adds a random offset time of a maximum width ±u to the transmission basic period T2, A communication method in which the probability of re-collision can be reduced and the delay time can be shortened by changing the maximum width ±u of the offset time, The collision probability when transmitting using the Aloha method is When the maximum width u of the offset time is less than 7, (4u+1) / (2u+1) 2 It is expressed as When the offset time u is 7 or more and 9 or less, (4u+1)(2u+1) 2 +(6u-6)((3u-19)+1} / 2(2u+1) ３ is expressed as A communication system according to any one of claims 1 to 11.

15. the remote control terminal device performs transmission in a slotted aloha system; The slot period timing is adjusted at or after power-on. A communication system according to any one of claims 1 to 11.

16. The slot cycle timing is adjusted by detecting signals of different communication pairs and adjusting the slot synchronization time, by adjusting to the slot cycle timing of the communication pair with the strongest radio wave strength, by periodically stopping sleep and performing a search to adjust the slot cycle timing, or by transmitting a slot timing signal or a frame timing signal from the control device at regular intervals, and the remote control terminal device performing a search to adjust the slot cycle timing.

16. The communication system of claim 15.

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