Belt protection device and control method based on CAN bus

Abstract

The present invention provides a belt protection device and a control method based on CAN bus. The belt protection device based on CAN bus comprises: a main control device, which is arranged at the head of a belt machine and is used to obtain status information sent by each node device along the belt line reported by a gateway, and alarm information obtained by monitoring or detection by the gateway; the main control device is electrically connected to the gateway; the gateway is arranged at the head of the belt machine and is used to obtain and summarize status information sent by each node device, monitor or detect a CAN bus to obtain alarm information, and send it to the main control device; the gateway is connected to each node device and a terminal through a line; the line comprises a power supply line and a CAN bus; a node device, a plurality of node devices are distributed at intervals along the belt line, and the status information of the belt at each distribution position is collected and sent to the gateway; the terminal is arranged at the tail of the belt machine and is used to send inspection commands to the node device and the gateway through the CAN bus; the present invention can reduce CAN bus conflicts.

Description

Technical Field

[0001] The invention relates to the technical field of belt conveyors, and in particular to a belt protection device and a control method based on a CAN bus. Background Art

[0002] At present, belt conveyors have become the main equipment for continuous transportation of bulk materials in various industries, and they also occupy a dominant position in underground transportation of coal mines. The quality of their operating conditions directly affects the transportation of materials in the entire coal mine, and plays a very important role in coal mine production. During the operation of the belt conveyor, problems such as slippage, emergency stop (manual switch emergency trigger shutdown), deviation, tearing, temperature, etc. have always been common faults studied and solved by manufacturers and users. In order to ensure safe production, the "Coal Mine Safety Regulations" also clearly stipulates that belt conveyors used underground in coal mines must be equipped with corresponding protective devices according to on-site conditions.

[0003] The existing belt protection device always has a high occupancy rate for the CAN bus, which often causes conflicts in the communication on the bus. In case of emergency, it is impossible to achieve real-time protection, which not only affects the normal transportation efficiency, but also has certain safety hazards. Summary of the invention

[0004] In order to solve at least one technical problem in the prior art, the embodiment of the present invention provides a belt protection device and control method based on CAN bus, which can effectively improve the hidden dangers of the device in use and is more conducive to the safety management of coal mines. In order to achieve the above technical objectives, the technical solution adopted by the embodiment of the present invention is:

[0005] In a first aspect, an embodiment of the present invention provides a belt protection device based on a CAN bus, comprising:

[0006] The main control device is arranged at the head of the belt conveyor, and is used to obtain the status information sent by each node device along the belt and the alarm information monitored or detected by the gateway, and execute the start / stop action accordingly; the main control device is electrically connected to the gateway;

[0007] The gateway is arranged at the head of the belt conveyor, and is used to obtain and summarize the status information sent by each node device, monitor or detect the CAN bus to obtain alarm information, and send it to the main control device; the gateway connects each node device and the terminal through a line; the line includes a power supply line and a CAN bus;

[0008] Node devices: multiple node devices are distributed along the belt at intervals, collecting the status information of the belts at each distribution location and sending it to the gateway;

[0009] The terminal is set at the tail of the belt conveyor and is used to send inspection commands to node devices and gateways through the CAN bus.

[0010] Furthermore, the alarm information includes trigger alarm information and disconnection alarm information; the gateway obtains the trigger alarm information by monitoring the alarm command sent by the node device on the CAN bus, and the gateway obtains the disconnection alarm information by detecting that the inspection command timeout on the CAN bus does not exist.

[0011] In a second aspect, an embodiment of the present invention provides a control method for a belt protection device based on a CAN bus, comprising:

[0012] The control methods of the sorting stage include:

[0013] Step S101, from the belt conveyor head to the belt conveyor tail, firstly the first node device is powered on and started;

[0014] Step S102, when the nth node device is powered on and started, it sends a search command;

[0015] Step S103, for each previous node device of the node device currently sending the search command, the previous node device has obtained its own number m, and when receiving the search command, it performs interval delay according to its own number m, and immediately sends a search response when the delay time of the interval delay is reached;

[0016] Step S104, the nth node device receives all search responses. When no search response is received after a preset search response delay, the largest number k among all search responses is obtained, k+1 is used as the nth node device's own number, and the power of the subsequent device is turned on;

[0017] Step S105, after the last node device is powered on and its own number is set, the terminal power is turned on; after the terminal is powered on, the belt protection device is in the working stage;

[0018] Control methods for working phases include:

[0019] Step S201, after the terminal is powered on, an inspection command is sent according to a set inspection cycle;

[0020] Step S202, when each node device receives the inspection command, it performs interval delay according to its own number m, and sends an inspection response when the delay time of the interval delay is reached; the content of the inspection response at least includes the status information of the belt;

[0021] Step S203, after detecting the inspection command, the gateway monitors the CAN bus, summarizes the status information sent by all node devices according to the received inspection response, and sends it to the master device; the gateway forwards the inspection command to the master device;

[0022] The main control device determines whether the belt is in normal condition based on the received summary status information, and determines whether the line is complete based on the periodically received inspection commands.

[0023] Furthermore, the delay time of the interval delay is set to 10*m milliseconds.

[0024] Furthermore, the command ID of the search response is a series of continuous ID numbers, and the number of the series of continuous ID numbers is equal to the number of node devices; the content of the search response is the node device's own number.

[0025] Furthermore, during the sorting phase, all node devices are in a silent state except for responding to search commands.

[0026] Furthermore, the control method of the working stage also includes:

[0027] Step S204, when at least one node device in the belt protection device has a chain control relationship with devices in other belt protection devices, the gateway sends a control command to the node device in an idle time slot at the end of an inspection cycle to control the action of related relays of the node device.

[0028] Furthermore, the content of the control command includes the relay state of the node device and the self number of the node device;

[0029] The node device that receives the control command does not need to reply with a control response. The content of the inspection response also includes the relay status of the node device. The gateway will detect the content of the inspection response sent by the node device that receives the control command in the next inspection cycle to determine whether the control command is executed.

[0030] Furthermore, the control method of the belt protection device based on the CAN bus also includes an alarm control method, including:

[0031] The alarm control method is triggered, including:

[0032] Step S301, when a node device generates a trigger alarm, an alarm command is immediately sent according to a set alarm cycle; the priority of the alarm command is higher than the priority of the search response and the inspection response; the alarm cycle is shorter than the inspection cycle;

[0033] Step S302, after the terminal monitors the alarm command, it stops sending the inspection command; other node devices that have not sent the alarm command enter the silent state after receiving the alarm command;

[0034] Step S303, after the gateway monitors the alarm command, it determines that the alarm information is triggered and notifies the main control device through the switch quantity; at the same time, after the gateway monitors the alarm command, it sends a confirmation command to the CAN bus;

[0035] Step S304, after receiving the confirmation command, the node device that issued the alarm command changes to a silent state; after the terminal monitors the confirmation command, it monitors the CAN bus for a set idle time and then starts sending the inspection command again;

[0036] Step S305: The content of the inspection response also includes a received alarm confirmation status. The node device that issued the alarm command sets the received alarm confirmation status in the subsequent inspection response to mark that the confirmation command has been received;

[0037] After the alarm of the node device is released, the belt status information and the alarm confirmation status in the inspection response sent out are set to 0;

[0038] The disconnection alarm control method comprises:

[0039] Step S401, the gateway monitors the CAN bus in real time. When it detects that there is no inspection command for N consecutive inspection cycles, it determines that a disconnection alarm occurs and sends the disconnection alarm information to the main control device; N is 2-5.

[0040] Furthermore, the content of the alarm command includes the status information of the belt, the relay status of the node device, and the status of the alarm received confirmation;

[0041] The node device that sends the alarm command is distinguished according to the command ID number of the alarm command.

[0042] The technical solution provided by the embodiment of the present invention has the following beneficial effects: through the architecture of the belt protection device based on the CAN bus and the corresponding control method proposed in the present application, the CAN bus conflict can be reduced, the problems existing in the existing coal mine belt protection can be effectively solved, and the operation stability of the belt protection device can be greatly improved, and the normal operation of the belt conveyor can be ensured in the harsh coal mine environment. Compared with the existing technology, the advantages are as follows:

[0043] 1) The contents of commands / responses on the CAN bus are all 1 byte, which can significantly reduce bus utilization.

[0044] 2) No manual coding is required, and each node device in the system can be sorted quickly and effectively.

[0045] 3) The integrity of the working line can be monitored in real time.

[0046] 4) Complete control and communication in time slots to avoid CAN bus conflicts to the greatest extent.

[0047] 5) Priorities can be flexibly adjusted according to actual conditions.

[0048] 6) The belt protection device has strong real-time alarm performance.

[0049] 7) Flexible control and easy to expand. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] Figure 1 Schematic diagram of the belt protection device structure in an embodiment of the present invention.

[0051] Figure 2 This is one of the schematic diagrams of the sorting stage in the embodiment of the present invention.

[0052] Figure 3 This is the second schematic diagram of the sorting stage in the embodiment of the present invention.

[0053] Figure 4 4 is a timing diagram of the sorting phase in an embodiment of the present invention.

[0054] Figure 5 2 is a timing diagram of the working stages in an embodiment of the present invention.

[0055] Figure 6 This is a timing diagram of triggering an alarm in an embodiment of the present invention.

[0056] Figure 7 This is a timing diagram of a disconnection alarm in an embodiment of the present invention. DETAILED DESCRIPTION

[0057] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0058] In the description of the embodiments of the present invention, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc., indicating the orientation or positional relationship, are based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first", "second", and "third" are used for descriptive purposes only and cannot be understood as indicating or implying relative importance.

[0059] In the description of the embodiments of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, it can also be the internal connection of two components, it can be a wireless connection, or it can be a wired connection. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0060] In addition, the technical features involved in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0061] like Figure 1 As shown, a belt protection device based on CAN bus proposed in an embodiment of the present invention includes:

[0062] The main control device is arranged at the head of the belt conveyor, and is used to obtain the status information sent by each node device along the belt and the alarm information monitored or detected by the gateway, and execute the start / stop action accordingly; the main control device is electrically connected to the gateway;

[0063] The gateway is arranged at the head of the belt conveyor, and is used to obtain and summarize the status information sent by each node device, monitor or detect the CAN bus to obtain alarm information, and send it to the main control device; the gateway connects each node device and the terminal through a line; the line includes a power supply line and a CAN bus;

[0064] Node devices: multiple node devices are distributed along the belt at intervals, collecting the status information of the belts at each distribution location and sending it to the gateway;

[0065] The terminal is set at the tail of the belt conveyor and is used to send inspection commands to node devices and gateways through the CAN bus.

[0066] Furthermore, the alarm information includes trigger alarm information and disconnection alarm information; the gateway obtains the trigger alarm information by monitoring the alarm command sent by the node device on the CAN bus, and the gateway obtains the disconnection alarm information by detecting that the inspection command timeout on the CAN bus does not exist.

[0067] In this embodiment, a total of 63 node devices are arranged along the belt of the belt conveyor; a single chip microcomputer and a sensor interface are arranged inside the node device, and connected with various sensor devices arranged along the belt; the sensor device may include a speed sensor, an emergency stop manual switch, a photoelectric sensor, an image sensor, a temperature sensor, etc. The node device may collect the status information of the belt at the distribution position through the sensor device, such as slippage, emergency stop (manual switch triggers emergency shutdown), deviation, tearing, temperature, etc.;

[0068] The embodiment of the present invention further provides a control method of a belt protection device, comprising:

[0069] 1. Control methods in the sorting phase, such as Figure 2 , Figure 3 As shown, including:

[0070] Step S101, from the belt conveyor head to the belt conveyor tail, firstly the first node device is powered on and started;

[0071] Step S102, when the nth node device is powered on and started, it sends a search command;

[0072] In this embodiment, the command ID of the search command is ID=0x180; that is, any node device sends the search command through ID=0x180; the content of the search command can be specified arbitrarily;

[0073] Step S103, for each previous node device of the node device currently sending the search command, the previous node device has obtained its own number m, and when receiving the search command, it performs interval delay according to its own number m, and immediately sends a search response when the delay time of the interval delay is reached; Figure 2 As shown;

[0074] Furthermore, the delay time of the interval delay is set to 10*m milliseconds; assuming that the current fifth node device is powered on and started, after the four preceding node devices receive the search command, the delay time for the first node device to send a search response is 10 milliseconds, the delay time for the second node device to send a search response is 20 milliseconds, the delay time for the third node device to send a search response is 30 milliseconds, and the delay time for the fourth node device to send a search response is 40 milliseconds; and so on, CAN bus conflicts are avoided;

[0075] Further, the command ID of the search response is a series of continuous ID numbers, and the number of the series of continuous ID numbers is equal to the number of node devices; the content of the search response is the node device's own number; in this embodiment, the ID segment of the command ID of the search response is 0x181 to 0x1BF; the node device's own number is 1 to 63; the command ID of the search response is a series of continuous ID numbers, and it is easier for the node device receiving the search response to distinguish which node device is sending the search response; in this embodiment, the content of the search response is 8 bits;

[0076] Step S104, the nth node device receives all search responses. When no search response is received after a preset search response delay, the largest number k among all search responses is obtained, and k+1 is used as the nth node device's own number, and the power of the subsequent device is turned on; Figure 3 As shown;

[0077] For the first node device, since no search response is received when all search responses are received, the largest number among all search responses is 0, and 0+1=1 is used as the first node device's own number;

[0078] In this embodiment, the preset search response delay is 50ms, that is, when the nth node device receives the last search response and does not receive any search response for more than 50ms, it is considered that there will be no subsequent search response, and the self number is set at this time;

[0079] See the timing diagram of the sorting phase for Figure 4 ;

[0080] Step S105, after the last node device is powered on and its own number is set, the terminal power is turned on;

[0081] Furthermore, during the sorting phase, all node devices are in a silent state except for responding to search commands;

[0082] When the terminal is powered on, the belt protection device can enter the working stage;

[0083] (ii) Control methods for working stages, such as Figure 5 As shown, including:

[0084] Step S201, after the terminal is powered on, an inspection command is sent according to a set inspection cycle;

[0085] In this embodiment, the inspection cycle is 1s; the command ID of the inspection command is ID=0x120; the content of the inspection command can be specified arbitrarily;

[0086] Step S202, when each node device receives the inspection command, it performs interval delay according to its own number m, and sends an inspection response when the delay time of the interval delay is reached; the content of the inspection response at least includes the status information of the belt;

[0087] In this step, the delay time of the interval delay is set to 10*m milliseconds; similar to sending a search response, each node device avoids CAN bus conflicts when sending a patrol response;

[0088] In this embodiment, the ID segment of the command ID of the inspection response is 0x181 to 0x1BF, which is the same as the ID segment of the command ID of the search response; the content of the inspection response includes the status information of the belt. In this embodiment, the status information of the belt is 5 bits, and the inspection response sent by the node device may include the status information collected by 5 sensor devices. For example, if the speed sensor does not detect slippage, then the corresponding status information bit is 0, and if slippage is detected, it is 1 (i.e., a trigger alarm is generated); in this embodiment, the content of the inspection response is 8 bits, in addition to 5 bits for indicating the status information of the belt, there are 2 bits for indicating the relay status of the node device, and 1 bit for indicating the alarm confirmation status received;

[0089] Step S203, after detecting the inspection command, the gateway monitors the CAN bus, summarizes the status information sent by all node devices according to the received inspection response, and sends it to the master device; the gateway forwards the inspection command to the master device;

[0090] Under normal circumstances, the master device uses the received summary status information to determine that the belt is in normal condition, and uses the periodically received inspection commands to determine that the line is complete (i.e., the gateway connects each node device and the terminal through the line), thus meeting the conditions for starting the belt;

[0091] The status information summarized by the gateway and the forwarded inspection commands can be sent to the main control device via RS-485;

[0092] Optionally, in step S204, when at least one node device in the belt protection device has an interlocking control relationship with devices in other belt protection devices, the gateway sends a control command to the node device in an idle time slot at the end of an inspection cycle to control the action of a related relay of the node device;

[0093] like Figure 5 As shown, in this embodiment, the capacity of the node device is 63, the inspection cycle is 1s, and the idle time slot at the end of a inspection cycle is about 300ms. The gateway can use this idle time slot to send additional control commands to the node device; the command ID of the control command is ID=0x110; the content of the control command includes the relay state of the node device (2 bits) and the node device's own number (6 bits);

[0094] The node device that receives the control command does not need to reply the control response. For this reason, the content of the inspection response also includes the relay status (2 bits) of the node device. The gateway will detect the content of the inspection response sent by the node device that receives the control command in the next inspection cycle to determine whether the control command is executed; if the control command is executed, the 2-bit relay status will change, for example, from 00 to 01 or 10 or 11;

[0095] In the idle time slot of 300ms at the end of a patrol cycle, the control command can be sent repeatedly for multiple times, for example, once every 20ms for 5 consecutive times;

[0096] (III) Alarm control methods, including:

[0097] Trigger alarm control method, such as Figure 6 As shown, including:

[0098] Step S301, when a node device generates a trigger alarm, an alarm command is immediately sent according to a set alarm cycle; the priority of the alarm command is higher than the priority of the search response and the inspection response; the alarm cycle is shorter than the inspection cycle;

[0099] In this embodiment, the alarm cycle is 0.1s, the ID segment of the command ID of the alarm command is 0x141-0x17F, and on the CAN bus, the smaller the ID number, the higher the priority; the content of the alarm command includes the status information of the belt (5 bits), the relay status of the node device (2 bits), and the alarm confirmation status (1 bit);

[0100] When sending an alarm command, the alarm confirmation status in the alarm command content is 0; the node device that sends the alarm command can be distinguished according to the command ID number of the alarm command;

[0101] Step S302, after the terminal monitors the alarm command, it stops sending the inspection command; other node devices that have not sent the alarm command enter the silent state after receiving the alarm command;

[0102] Step S303, after the gateway monitors the alarm command, it determines that the alarm information is triggered and notifies the main control device through the switch quantity; at the same time, after the gateway monitors the alarm command, it sends a confirmation command to the CAN bus;

[0103] The main control device can decide whether to execute the shutdown action according to the preset control logic;

[0104] In this embodiment, the command ID of the confirmation command is ID=0x100; the content of the confirmation command is arbitrarily specified;

[0105] Step S304, after receiving the confirmation command, the node device that issued the alarm command changes to a silent state; after the terminal monitors the confirmation command, it monitors the CAN bus for a set idle time and then starts sending the inspection command again;

[0106] The idle time can be set to 50ms;

[0107] Step S305: The content of the inspection response also includes a received alarm confirmation status (1 bit). The node device that issued the alarm command sets the received alarm confirmation status in the subsequent inspection response to mark that the confirmation command has been received;

[0108] After the alarm of the node device is released, the belt status information and the alarm confirmation status in the inspection response sent out are set to 0;

[0109] Disconnection alarm control method, such as Figure 7 As shown, including:

[0110] Step S401, the gateway monitors the CAN bus in real time. When it detects that there is no inspection command for N consecutive inspection cycles, it determines that a disconnection alarm occurs and sends the disconnection alarm information to the main control device; N is 2 to 5, and the typical value is 3;

[0111] In this embodiment, the disconnection alarm information can be sent to the main control device via RS-485;

[0112] During the disconnection period, other online node devices can still generate trigger alarms.

[0113] Finally, it should be noted that the above specific implementation methods are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the embodiments, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the spirit and scope of the technical solution of the present invention, which should be included in the scope of the claims of the present invention.

Claims

1. A belt protection device based on CAN bus, characterized in that: include: The main control device is arranged at the head of the belt conveyor, and is used to obtain the status information sent by each node device along the belt and the alarm information monitored or detected by the gateway, and execute the start / stop action accordingly; the main control device is electrically connected to the gateway; The gateway is set at the head of the belt conveyor to obtain and summarize the status information sent by each node device, monitor or detect the CAN bus to obtain alarm information, and send it to the main control device; The gateway connects each node device and the terminal through a line; the line includes a power supply line and a CAN bus; Node devices: multiple node devices are distributed along the belt at intervals, collecting the status information of the belts at each distribution location and sending it to the gateway; The terminal is set at the tail of the belt conveyor and is used to send inspection commands to the node devices and gateways through the CAN bus; The alarm information includes trigger alarm information and disconnection alarm information; the gateway obtains the trigger alarm information by monitoring the alarm command sent by the node device on the CAN bus, and the gateway obtains the disconnection alarm information by detecting that the inspection command on the CAN bus does not time out; The belt protection device also includes a control method of the belt protection device based on a CAN bus, comprising: The control methods of the sorting stage include: Step S101, from the belt conveyor head to the belt conveyor tail, firstly the first node device is powered on and started; Step S102, when the nth node device is powered on and started, it sends a search command; Step S103, for each previous node device of the node device currently sending the search command, the previous node device has obtained its own number m, and when receiving the search command, it performs interval delay according to its own number m, and immediately sends a search response when the delay time of the interval delay is reached; Step S104, the nth node device receives all search responses. When no search response is received after a preset search response delay, the largest number k among all search responses is obtained, k+1 is used as the nth node device's own number, and the power of the subsequent device is turned on; Step S105, after the last node device is powered on and its own number is set, the terminal power is turned on; after the terminal is powered on, the belt protection device is in the working stage; Control methods for working phases include: Step S201, after the terminal is powered on, an inspection command is sent according to a set inspection cycle; Step S202, when each node device receives the inspection command, it performs interval delay according to its own number m, and sends an inspection response when the delay time of the interval delay is reached; the content of the inspection response at least includes the status information of the belt; Step S203, after detecting the inspection command, the gateway monitors the CAN bus, summarizes the status information sent by all node devices according to the received inspection response, and sends it to the master device; the gateway forwards the inspection command to the master device; The main control device uses the received summary status information to determine whether the belt is in normal condition, and uses the periodically received inspection commands to determine whether the line is complete; The alarm control method includes: The alarm control method is triggered, including: Step S301, when a node device generates a trigger alarm, an alarm command is immediately sent according to a set alarm cycle; the priority of the alarm command is higher than the priority of the search response and the inspection response; the alarm cycle is shorter than the inspection cycle; Step S302, after the terminal monitors the alarm command, it stops sending the inspection command; other node devices that have not sent the alarm command enter the silent state after receiving the alarm command; Step S303, after the gateway monitors the alarm command, it determines that the alarm information is triggered and notifies the main control device through the switch quantity; at the same time, after the gateway monitors the alarm command, it sends a confirmation command to the CAN bus; Step S304, after receiving the confirmation command, the node device that issued the alarm command changes to a silent state; after the terminal monitors the confirmation command, it monitors the CAN bus for a set idle time and then restarts sending the inspection command; Step S305: The content of the inspection response also includes a received alarm confirmation status. The node device that issued the alarm command sets the received alarm confirmation status in the subsequent inspection response to mark that the confirmation command has been received; After the alarm of the node device is released, the belt status information and the alarm confirmation status in the inspection response sent out are set to 0; The disconnection alarm control method comprises: Step S401, the gateway monitors the CAN bus in real time. When it detects that there is no inspection command for N consecutive inspection cycles, it determines that a disconnection alarm occurs and sends the disconnection alarm information to the main control device; N is 2-5.

2. The CAN bus-based belt protection device according to claim 1, characterized in that: The delay time of the interval delay is set to 10*m milliseconds.

3. The CAN bus-based belt protection device according to claim 1, characterized in that: The command ID of the search response is a series of continuous ID numbers, the number of which is equal to the number of node devices; the content of the search response is the node device's own number.

4. The CAN bus-based belt protection device according to claim 1, characterized in that: During the sorting phase, all node devices are in a silent state except for responding to search commands.

5. The CAN bus-based belt protection device according to claim 1, characterized in that: The control method of the working stage also includes: Step S204, when at least one node device in the belt protection device has a chain control relationship with devices in other belt protection devices, the gateway sends a control command to the node device in an idle time slot at the end of an inspection cycle to control the action of related relays of the node device.

6. The CAN bus-based belt protection device according to claim 5, characterized in that: The content of the control command includes the relay state of the node device and the node device's own number; The node device that receives the control command does not need to reply with a control response. The content of the inspection response also includes the relay status of the node device. The gateway will detect the content of the inspection response sent by the node device that receives the control command in the next inspection cycle to determine whether the control command is executed.

7. The CAN bus-based belt protection device according to claim 1, characterized in that: The alarm command content includes the belt status information, the relay status of the node device, and the alarm confirmation status; The node device that sends the alarm command is distinguished according to the command ID number of the alarm command.

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