An overhead crane fault self-diagnosis system and method

Abstract

The present invention relates to a self-diagnosis system and method for overhead crane faults, belonging to the technical field of overhead crane equipment and methods. The technical solution of the present invention is that the PLC is connected and communicates with each ET200 station and the inverter through the DP bus. The touch display screen is installed in the driver's cab, and the PLC and the touch display screen are also connected and communicate through the DP bus. The beneficial effect of the present invention is that it not only comprehensively reflects faults, but also can effectively filter out some invalid information, thereby improving the accuracy of its diagnostic information. Remarkable results have been achieved in aspects such as early detection and prevention of potential faults, reduction of fault impact time, and reduction of pouring stop accidents, and it has good popularization and application value.

Description

Technical Field

[0001] The present invention relates to a self-diagnosis system and method for overhead crane faults, belonging to the technical field of overhead crane equipment and methods. Background Art

[0002] With the expansion of the production scale and the improvement of the automation level in metallurgical enterprises, as a key equipment in metallurgical production, the requirements for foundry cranes are getting higher and higher. With the increase of the lifting weight and equipment capacity, its electric control system is becoming increasingly complex. The requirements that the equipment operation needs to meet and the requirements for its operation safety and reliability are also getting higher and higher. Advanced technologies such as variable frequency speed regulation and PLC control have been widely applied to overhead cranes. The application of PLC technology has laid a solid foundation for the intelligent and information development of overhead cranes.

[0003] The 450T overhead crane in Hanbao Steelmaking Plant is responsible for operations such as tapping and lifting molten steel and hot metal, and it is one of the most important equipment in the steelmaking plant. The operation rate during production is extremely high, and there is no standby vehicle. Once a fault occurs, it will affect production at least, and may even cause pouring stop and production suspension accidents, which has a significant impact on the entire production. Therefore, the rapid handling and prevention of faults are crucial for production. The production operation characteristics of the steelmaking plant determine that the requirements for the safety performance and reliability of the 450T overhead crane are very high. This crane is a large-scale foundry crane with advanced level today. The electrical control system adopts a whole vehicle PLC redundant control, full variable frequency speed regulation drive, and independent redundant control scheme for each mechanism. The design of the electric control system is complex, with numerous various controls and safety interlock protections. This makes it very difficult to troubleshoot and handle faults, thus prolonging the fault handling time. And the importance of the 450T overhead crane to production means that once a fault occurs in this crane, it will affect production. Sometimes, if the fault time exceeds 10 minutes, it can cause pouring stop and production suspension accidents, which has a serious impact on production and must be handled quickly. Therefore, the requirements for the quality of maintenance personnel are very high, and it will also cause great psychological pressure on maintenance personnel during the fault handling process, which is prone to cause unsafe factors. Thus, a fault information self-diagnosis system that can accurately and effectively provide fault information to help maintenance personnel quickly analyze and judge faults is very necessary. Summary of the Invention

[0004] The purpose of the present invention is to provide a self-diagnosis system for overhead crane faults. By reasonably setting up fault information variables expressing various fault causes and adopting the design idea of fault classification and grading, the developed logic control algorithm makes the diagnostic information of faults accurate and effective. It not only comprehensively reflects faults but also can effectively filter out some invalid information, thereby improving the accuracy rate of its diagnostic information. Remarkable results have been achieved in aspects such as early detection and prevention of potential faults, reduction of fault influence time, and reduction of pouring stop accidents, and it has good popularization and application value, effectively solving the above problems existing in the background art.

[0005] The technical solution of the present invention is: a self-diagnosis system for overhead crane faults, which includes a PLC, a touch display screen, an inverter, an ET200 station, and a DP bus. The number of the inverters and ET200 stations is more than one. The PLC is connected and communicates with each ET200 station and inverter through the DP bus. The touch display screen is installed in the driver's cab, and the PLC and the touch display screen are also connected and communicate through the DP bus.

[0006] A method for self-diagnosing overhead crane faults includes the following steps:

[0007] (1) Establish appropriate fault information variables that can express various fault causes;

[0008] (2) Real-time monitor the state changes of the fault information variables, and diagnose the fault causes based on the changes of relevant fault information;

[0009] (3) Trigger the corresponding fault alarm message on the touch display screen, and display the fault description information corresponding to the fault cause.

[0010] In step (1), summarize and analyze the various fault records of this vehicle over the years, combine the experience of technical personnel, and establish a fault diagnosis information table corresponding to various fault causes; establish corresponding fault information variables in the PLC control program, use the PLC programming function to establish a shared data block DB601 for the state of the fault information variables, and store the current state value of the fault information variables in this data block; during the operation of the PLC program, the content of the data block is updated in real time according to the changes in the state of the fault information variables.

[0011] In step (2), the fault cause diagnosis adopts the design idea of classification and grading. According to the influence degree and severity of various faults in the established fault information diagnosis table on the normal operation of this overhead crane, the fault types are divided into four categories: one category is the faults that will cause the whole vehicle to lose power or fail to start, and the whole vehicle cannot run; the second category is the faults that will cause a certain mechanism to not work and affect normal operation; the third category is the faults that will cause partial function loss, and the overhead crane can run but affect the operation efficiency; the fourth category is the faults that do not affect the operation in the short term, but are not allowed to work with diseases for a long time; the grading is based on the number of changes in the state value of the fault information variables caused by a certain fault and the number of fault information variables required to judge a certain fault, which is conducive to clarifying the fault and is also relatively divided into four levels: the first level is that there are many fault information variables associated with this fault; the second level is that the number of fault information variables associated with this fault is less than that of the first level; the third level is for some interlock faults, and several fault information are required to determine this fault; the fourth level is that this fault is independent and only affects itself; the diagnosis program judges the true cause of the fault by logically comparing the priority levels of the fault variables.

[0012] The beneficial effects of the present invention are as follows: By reasonably setting up fault information variables expressing various fault causes, adopting the design concept of fault classification and grading, and developing a logic control algorithm based on this, the diagnostic information for faults is accurate and effective. It not only comprehensively reflects faults but also can effectively filter out some invalid information, thereby improving the accuracy rate of its diagnostic information. Remarkable results have been achieved in aspects such as early detection and prevention of potential faults, reduction of fault impact time, and decrease of pouring stop accidents, and it has good popularization and application value. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 is the hardware connection diagram of the present invention;

[0014] Figure 2 is the system function block diagram of the present invention;

[0015] Figure 3 is the working flowchart of the present invention;

[0016] In the figure: PLC1, touch display screen 2, inverter 3, ET200 station 4, DP bus 5. DETAILED DESCRIPTION OF THE INVENTION

[0017] In order to make the objectives, technical solutions, and advantages of the invention implementation cases clearer, the technical solutions in the implementation cases of the present invention will be clearly and completely described below in conjunction with the attached drawings in the implementation cases. Obviously, the described implementation cases are a small part of the implementation cases of the present invention, rather than all of them. Based on the implementation cases of the present invention, all other implementation cases obtained by those of ordinary skill in the art without creative work fall within the protection scope of the present invention.

[0018] A crane fault self-diagnosis system includes a PLC1, a touch display screen 2, an inverter 3, an ET200 station 4, and a DP bus 5. The number of the inverter 3 and the ET200 station 4 is more than one. The PLC1 is connected and communicates with each ET200 station 4 and the inverter 3 through the DP bus 5. The touch display screen 2 is installed in the driver's cab, and the PLC1 and the touch display screen 2 are also connected and communicate through the DP bus 5.

[0019] A crane fault self-diagnosis method includes the following steps:

[0020] (1) Establish appropriate fault information variables capable of expressing various fault causes;

[0021] (2) Real-time monitor the state changes of the fault information variables and make a fault cause diagnosis based on the changes of relevant fault information;

[0022] (3) Trigger the corresponding fault alarm message on the touch display screen and display the fault description information corresponding to the fault cause.

[0023] In step (1), summarize and analyze the various fault records of this vehicle over the years, and combine with the experience of technicians to establish a fault diagnosis information table corresponding to various fault causes; set up corresponding fault information variables in the PLC control program, and use the PLC programming function to establish a shared data block DB601 for the status of the fault information variables, and store the current status value of the fault information variables in this data block; during the operation of the PLC program, update the content of the data block in real time according to the change of the status of the fault information variables.

[0024] In step (2), the fault cause diagnosis adopts the design idea of classification and grading. According to the influence degree and severity of various faults in the established fault information diagnosis table on the normal operation of this overhead crane, the fault types are divided into four categories: one category is the fault that will cause the whole vehicle to lose power or fail to start, and the whole vehicle cannot run; the second category is the fault that will cause a certain mechanism to fail to work and affect normal operation; the third category is the fault that will cause some functions to be missing, and the overhead crane can run but the operation efficiency is affected; the fourth category is the fault that does not affect the operation in the short term, but is not allowed to work with diseases for a long time; the grading is based on the number of changes in the status value of the fault information variables caused by a certain fault and the number of fault information variables required to judge a certain fault, so as to facilitate the identification of faults, and is also relatively divided into four levels: the first level is that there are many fault information variables associated with this fault; the second level is that the number of fault information variables associated with this fault is less than that of the first level; the third level is for some interlock faults, and several fault information are required to determine this fault; the fourth level is that this fault is independent and only affects itself; the diagnosis program judges the true cause of the fault by logically comparing the priority levels of the fault variables.

[0025] In practical applications, the technical solution adopted by the present invention is as follows:

[0026] I. System Hardware Composition

[0027] The 450T overhead crane adopts a full-frequency conversion drive and PLC control working mode. The PLC uses Siemens S7-400H redundant dual PLCs, and the frequency converters use Siemens 6SE70 series AFE and inverters. All input and output signals are collected through each distributed ET200 station. The PLC uses a DP bus to connect and communicate with each ET200 station and the inverter, as Figure 1 , and the PLC is the control center and data center of the whole vehicle; the PLC drives the inverter to operate through the DP bus. The hardware part of the present invention includes this PLC and a Siemens MP370T type touch display installed in the driver's cab. The PLC and the touch display are also connected and communicated through the DP bus.

[0028] II. System Software Design

[0029] The software part of this patent consists of two parts: the PLC400 program design and the MP370T touch display screen fault information monitoring and display design.

[0030] (1)PLC400 program design

[0031] This part completes the self-diagnosis function for various faults. The main problems to be solved for realizing this function are as follows: First, establish appropriate fault information variables that can express the causes of various faults. It is required that the fault information variables can reflect as comprehensive a range of faults as possible. At the same time, the fault information variables can accurately express the corresponding fault causes, and the number of fault information variables should be as small as possible. Second, the effective display problem of fault self-diagnosis information. In the system of this patent, by monitoring the state changes of fault information variables in real time, when a fault occurs, the corresponding fault alarm message is triggered to display the cause of the fault. Due to the correlation of the control device, one fault often causes the state changes of several related fault information variables, thus triggering the display of several fault cause information, which causes difficulties for maintenance personnel in judgment. This requires that the fault cause diagnosis display information be as little as possible and the information be efficient and accurate. Implementation plan:

[0032] Ⅰ. According to the working principle and control strategy of the 450T overhead crane electric control system, summarize and analyze the various fault records of this crane over the years. Combining with the experience of technical personnel, establish a fault diagnosis information table corresponding to various fault causes, set up corresponding fault information variables in the PLC control program, use the PLC programming function to establish a shared data block DB601 for the state of the fault information variables, store the current state values of the fault information variables in this data block, and update the content of the data block in real time according to the state changes of the fault information variables during the operation of the PLC program. This data block serves the fault information monitoring and display part and is the data center of the entire fault self-diagnosis system.

[0033] II. The fault information monitoring and display section of the present invention adopts a message trigger mechanism, that is, when the variable status value in the data block corresponding to the fault information variable changes compared with its normal status value, the fault information display for this variable will be triggered. To improve the effectiveness and accuracy of the fault information display, the number of irrelevant information displays needs to be reduced. This requires us to adopt an efficient control method for updating the variable status value in the data block that causes the message trigger. For this purpose, we have adopted the design ideas of classification and grading. According to the influence degree and severity of various faults in the established fault information diagnosis table on the normal operation of the overhead crane on that day, the fault types are divided into four categories: The first category is the faults that will cause the entire vehicle to lose power, unable to start, and the whole vehicle cannot operate; the second category is the faults that will cause a certain mechanism to not work, affecting normal operations; the third category is the faults that will cause partial function loss, and the overhead crane can operate but the operation efficiency is affected; the fourth category is the faults that do not affect the operation in the short term, but are not allowed to work with defects for a long time; grading is carried out according to the number of changes in the variable status value of the fault information variable caused by a certain fault and the number of fault information variables required to judge a certain fault, which is conducive to clarifying the fault and is also relatively divided into four levels: The first level is that there are many fault information variables associated with this fault. For example, when the control power supply F21 of the main hoisting mechanism trips, it will cause the entire vehicle to lose power, and the variable status of this mechanism and many other mechanisms will change; the second level is that the number of fault information variables associated with this fault is less than that of the first level. For example, when the control power supply F22 of the main trolley mechanism trips, it only affects some variable values related to this mechanism; the third level is for some interlock faults. To determine this fault, several fault information are required. For example, for the shaft break protection fault, its principle is realized by comparing the encoder values of the main hoisting motors 1# and 2#, the drums 1# and 2#. The encoder value of drum 1# is compared with the motor encoder value, the encoder value of drum 2# is compared with the motor encoder value, and the encoder values of drum 1# and drum 2# are compared. To quickly determine which encoder is faulty, 3 fault information variables are required; the fourth level is that this fault is independent and only affects itself, such as the limit switch fault. Through fault classification and grading, we have sorted out and clarified the faults expressed by the fault information variables and the mutual relationship between the fault information variables. Combining the analysis and summary of the causes of various faults of the 450T overhead crane over the years, and the fault handling experience of technical personnel for many years, the priority level of the fault information variables is determined, and the corresponding update rules are established for the assignment of the corresponding status values in the data block DB601 for storing fault information. Based on this, a set of fault diagnosis logic control algorithms is compiled. When a fault occurs, this control algorithm can make an "intelligent" judgment on its fault information variables, and thus selectively assign values to the status values of the fault information data block in sequence. In this way, some ineffective information displays are filtered out. Coupled with the fault time sorting and the setting of the display style of the fault information description text in the fault information monitoring section, the present patent achieves a very high accuracy rate in fault judgment and information display.

[0034] (2) Design of Fault Information Monitoring and Display

[0035] The MP370T touch display fault information monitoring program is configured by Protool software. This monitoring system adopts a message trigger mechanism, and the message trigger control source is the status value of the corresponding information variable in the data block established in the PLC program. That is, the monitoring program directly associates with the data block storing the fault information status value in the PLC, and monitors the fault information status value in the data block in real time. When a fault occurs, the corresponding fault information status value will change, triggering the corresponding message alarm, and displaying the alarm message record on the display screen. This record contains the message number, fault date, time, fault description text, etc. set by us. The alarm messages are displayed in chronological order, and each fault information variable corresponds to an information description text for this fault. Based on this, the fault cause can be quickly identified. To improve the effectiveness of this system, through summarizing and analyzing various types of faults of the 450T overhead crane over the years and combining personal fault handling experience, the display styles of some fault information description texts corresponding to faults are set as underlined, flashing, etc., further improving the accuracy of the fault display information. The displayed fault records are confirmed and eliminated by the inspection personnel so that they can understand some abnormal information of the overhead crane and take preventive measures in advance.

[0036] III. Description of the control flow of this fault self-diagnosis system

[0037] The working principle of the present invention is to monitor the change of the status value of the information variable representing various faults in the normal and fault states, make a "self" judgment on the fault cause according to the change of relevant fault information, and then trigger the display of the fault description information corresponding to this fault cause on the display screen, so that the operators and maintenance personnel can quickly identify the fault. The detailed description is as follows:

[0038] The operation of this system consists of a PLC control diagnosis program part and a touch display monitoring program part. The two parts operate independently and are connected through DP bus communication. The PLC control diagnosis part completes functions such as acquisition, assignment, fault diagnosis, and information storage of the status value of the fault information variable. The touch display monitoring program part completes functions such as reading the status value of the PLC fault information storage block, triggering the fault alarm information, and displaying the fault information.

[0039] 1. Reading and assignment of the fault information variable value

[0040] The working mode of the PLC is a cyclic program processing mode, and the operation mechanism of the present invention is as Figure 2 shown. In one cycle process, the CPU reads the input signal value of the input module and refreshes the input process image, executes the user control program. After executing this process, the status values of all fault information variables required by the fault information table are refreshed and assigned;

[0041] 2. Fault diagnosis

[0042] When a fault occurs, the determination of the cause of the fault is completed by this fault diagnosis program part (FC99). Classified by the faults of each mechanism of the overhead crane, the diagnostic program FC99 consists of six diagnostic parts: main hoist fault, auxiliary hoist fault, trolley fault, main crab fault, auxiliary crab fault, and other faults. The cause of the fault is judged by the fault information variable whose state value changes compared with the normal value. When a certain fault occurs, it often causes changes in the state values of several or more than a dozen related fault information variables. The fault diagnosis program has to accurately judge the cause of the fault as much as possible based on the "intelligence" we endow it. The criterion for judgment is the priority level of the fault information variable. The determination of this priority level is the difficulty and core of this patent, directly affecting the accuracy rate of this diagnostic system. The priority levels of all fault information variables are determined according to the classification and grading principles we formulated. For example, for the fault that the control power supply F21 of the main hoist mechanism trips, the fault classification belongs to category one, and the level classification belongs to level one, so the priority level of this fault variable is level one. For the fault that the control power supply F22 of the main crab mechanism trips, the fault classification belongs to category two, and the level classification belongs to level one, so the priority level of this fault variable is level two. When a certain fault occurs, the state values of the fault information variable that causes the fault and some fault variables related to this fault variable change. The diagnostic program judges the true cause of the fault by logically comparing the priority levels of these fault variables. In this way, only the fault state value of the true fault information variable needs to be stored in the fault information data block (DB601), and only the information of this fault variable is triggered for display, effectively filtering out the display of invalid information.Taking the tripping of the control power supply F21 of the main hoisting mechanism as an example, this fault will cause the vehicle to lose power and cannot start. At the same time, it will cause changes in multiple fault variable values such as the main hoisting limit switch, the main hoisting 1# and 2# overspeed, the main hoisting 1# and 2# brake contactors, the main hoisting emergency stop relay, and the vehicle total emergency stop relay. The tripping of the control power supply F21, the main hoisting limit switch, and the main hoisting emergency stop relay will all cause the vehicle to lose power. However, their control logics are different. The tripping of the control power supply F21 will cause changes in the state values of the main hoisting limit switch and the main hoisting emergency stop relay. The faults of the main hoisting limit switch and the main hoisting emergency stop relay will not cause changes in the variable state value of the control power supply F21. Similarly, the fault of the main hoisting limit switch will cause a change in the state value of the main hoisting emergency stop relay, while the fault of the main hoisting emergency stop relay will not cause a change in the state value of the main hoisting limit switch. In this way, the priority level of the control power supply F21 variable is higher than that of the main hoisting limit switch, and the priority level of the main hoisting limit switch variable is higher than that of the main hoisting emergency stop relay. That is, the priority level of the fault variable includes both the classification of the fault cause and the control logic, sequence, and correlation relationship between the relevant fault variables, and combines the summary of the fault handling experience of technicians for many years. The diagnostic program can determine that the priority level of the control power supply F21 variable is the highest by logically judging the priority level of the fault variable whose state value has changed, and thus determines that this fault is caused by the tripping of the control power supply F21. Only the state value corresponding to the variable determined by the diagnostic program as the real fault cause needs to be changed in the fault diagnosis information storage data block, while the state value corresponding to the variable determined as the non-real fault cause remains the normal value unchanged. In this way, the display of fault information is effectively reduced, and the accuracy of fault information is improved.

[0043] 3. Storage of Fault Diagnosis Information

[0044] The state values of all fault information variables representing various faults are saved in the fault diagnosis information data block DB601. This data block is the data source of the monitoring and display part. The monitoring program triggers the fault information corresponding to the changed state value to be displayed on the touch display screen according to the change of the state value in the data block. The change of the state value in the data block DB601 is controlled by the diagnostic program. When a certain fault occurs, it will cause some related fault information variables to become fault state values. Only the state value determined by the diagnostic program as a real fault variable is stored in the data block, while for the variable determined by the diagnostic program as a non-real fault, although its value has changed, its fault state value will not be stored in the data block, and the state value corresponding to it in the data block remains the normal value. In this way, the display of invalid fault information is filtered out.

[0045] 4. Monitoring and Display of Fault Information

[0046] The monitoring program of the touch display screen and the PLC control diagnosis program run in parallel independently and are connected through the DP bus. The monitoring program associates the data sources it needs to read with the fault diagnosis information data block DB601 in the PLC through configuration. The monitoring program reads the status values in the data block in real time according to the set acquisition period and compares them with their normal status values. When a fault occurs, the status value corresponding to the fault read by the monitoring program from the data block is different from its normal status value. At this time, a fault alarm will be triggered, and the fault cause description information corresponding to the fault, which has been configured and edited by us, will be displayed in the fault monitoring screen of the touch display screen in the required format and content to help operators and maintenance personnel quickly identify the fault and deal with it in a timely manner.

[0047] The remarkable advantages and application effects of the present invention:

[0048] 1. By reasonably setting up fault information variables expressing various fault causes and adopting the design concept of fault classification and grading, the logical control algorithm developed accordingly enables the fault diagnosis information to be accurate and effective. The design concept is advanced and reasonable, and the logical thinking is clear and definite, solving some difficult problems in fault diagnosis.

[0049] 2. Based on the summary and analysis of a large number of various fault cases of 450T overhead cranes over the years and combined with the fault handling experience of technical personnel for many years, the present invention develops and designs a set of intelligent self-diagnosis system for faults. Not only does the system reflect all faults comprehensively, but also it has a certain degree of "intelligence" in judging the fault causes, which can effectively filter out some invalid information, thereby improving the accuracy rate of its diagnosis information.

[0050] 3. Through continuous tracking and verification, the present invention has good practical effects in the fault troubleshooting of 450T overhead cranes, and has achieved remarkable results in aspects such as early detection and prevention of potential faults, reduction of fault influence time, and reduction of pouring stop accidents, and has good promotion and application value.

Claims

1. A self-diagnosis method for overhead crane faults, characterized in that It includes the following steps: (1) Establish appropriate fault information variables that can express various fault causes; (2) Monitor the status changes of the fault information variables in real time and diagnose the fault causes based on the changes of relevant fault information; (3) Trigger the corresponding fault alarm message on the touch display screen and display the fault description information corresponding to the fault cause; In step (1), summarize and analyze the various fault records of this vehicle over the years, and combine with the experience of technicians to establish a fault diagnosis information table corresponding to various fault causes; Set up corresponding fault information variables in the PLC control program, use the PLC programming function to establish a shared data block DB601 for the status of the fault information variables, and store the current status values of the fault information variables in this data block; during the operation of the PLC program, update the content of the data block in real time according to the status changes of the fault information variables; In step (2), the fault cause diagnosis adopts the design idea of classification and grading. According to the influence degree and severity of various faults in the established fault information diagnosis table on the normal operation of this overhead crane, the fault types are divided into four categories: one category is the fault that will cause the whole vehicle to lose power or fail to start, and the whole vehicle cannot run; the second category is the fault that will cause a certain mechanism to fail to work and affect normal operation; the third category is the fault that will cause partial function loss, and the overhead crane can run but affect the operation efficiency; the fourth category is the fault that does not affect the operation in the short term, but does not allow working with diseases for a long time; the grading is carried out according to the number of status value changes of the fault information variables caused by a certain fault and the number of fault information variables required to judge a certain fault, so as to facilitate the identification of faults, and it is also relatively divided into four levels: the first level is that there are many fault information variables associated with this fault; the second level is that the number of fault information variables associated with this fault is less than that of the first level; The third level is for some interlock faults, and several fault information are required to determine this fault; The fourth level is that this fault is independent and only affects itself; the diagnosis program judges the true cause of the fault by logically comparing the priority levels of the fault variables; The change of the status value in the data block DB601 is controlled by the diagnosis program. When a certain fault occurs, it will cause some relevant fault information variables to become fault status values. Only the status values of the fault variables determined by the diagnosis program to be real faults are stored in the data block, while the variables determined by the diagnosis program to be non-real faults, although their values have changed, their fault status values will not be stored in the data block, and the corresponding status values in the data block still remain normal values. In this way, the display of invalid fault information is filtered out.

2. The self-diagnosis system of a overhead crane fault self-diagnosis method according to claim 1, characterized in that: It includes a PLC (1), a touch display screen (2), an inverter (3), an ET200 station (4) and a DP bus (5). The number of the inverters (3) and the ET200 stations (4) is more than one. The PLC (1) is connected and communicates with each ET200 station (4) and the inverter (3) through the DP bus (5). The touch display screen (2) is installed in the driver's cab, and the PLC (1) and the touch display screen (2) are also connected and communicate through the DP bus (5).

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