WO2024093668A1

WO2024093668A1 - Train operation control method and system

Info

Publication number: WO2024093668A1
Application number: PCT/CN2023/125028
Authority: WO
Inventors: 周延昕; 耿鹏; 孙晓光; 吴亮; 杨迪飞; 马新成; 曹学思; 赵悦彤; 徐之栋; 王海南
Original assignee: 中国铁路通信信号股份有限公司; 通号城市轨道交通技术有限公司
Priority date: 2022-10-31
Filing date: 2023-10-17
Publication date: 2024-05-10
Also published as: CN115782963A

Abstract

Provided in the present invention are a train operation control method and system. The method comprises: determining whether first data which is sent by a vehicle-mounted signal system within a preset number of continuous periods is invalid; and if so, determining that communication abnormality occurs in the vehicle-mounted signal system, and sending an emergency braking command to a train braking control unit by means of a vehicle control unit, wherein communication between the vehicle-mounted signal system and the vehicle control unit is performed on the basis of a real-time train data protocol and by means of a train Ethernet, and the emergency braking command is sent to the vehicle control unit by the vehicle-mounted signal system when the communication abnormality occurs in the vehicle-mounted signal system. The system executes the method. By means of the present invention, the defect of a hard wire interface being used between a vehicle-mounted signal system and a vehicle control unit is solved, and data exchange between the vehicle-mounted signal system and the vehicle control unit is realized on the basis of a real-time train data protocol and by means of a train Ethernet, thereby ensuring that a train control requirement for a train is met when communication abnormality occurs in a data exchange process.

Description

Train operation control method and system

Technical Field

The present invention relates to the field of rail transit technology, and in particular to a train operation control method and system.

Background technique

At present, there are two types of interfaces between urban rail transit onboard signal systems and vehicles: digital input and output hard-wired interfaces and communication interfaces. Among them, interface data with higher requirements for real-time or security are basically carried out in hard-wired mode.

The hard-wired interface between the vehicle signal system and the vehicle control unit has the following four main defects:

(1) It is necessary to purchase basic hardware such as cables, connectors, and relays separately, and to perform wiring, calibration, and debugging for each interface one by one, which increases equipment and labor costs.

(2) If a new interface is needed, rewiring may be required, which is time-consuming and labor-intensive.

(3) Safety input and output require separate safety design.

(4) If an interface fails, all devices connected to that interface need to be checked, which takes a long time.

Summary of the invention

The train operation control method and system provided by the present invention are used to solve the above-mentioned problems existing in the prior art. In order to solve the defect of using a hard-wire interface between the on-board signal system and the vehicle control unit, based on the train real-time data protocol, the train Ethernet is used to realize the data exchange between the on-board signal system and the vehicle control unit, ensuring that communication anomalies occur during the data exchange process. Meet the train control needs at the same time.

The present invention provides a train operation control method, comprising:

Determining whether the first data sent by the vehicle signal system within a continuous preset period are all invalid;

If yes, it is determined that a communication abnormality occurs in the onboard signal system, and an emergency braking command is sent to the train braking control unit through the vehicle control unit;

Wherein, the on-board signal system and the vehicle control unit communicate with each other based on the train real-time data protocol and through the train Ethernet;

The emergency braking command is sent by the vehicle signal system to the vehicle control unit when the communication abnormality occurs in the vehicle control unit.

According to a train operation control method provided by the present invention, the step of determining whether the first data sent by the on-board signal system within a continuous preset period are all invalid comprises:

If it is determined that a communication error occurs when the vehicle signal system sends the first data to the vehicle control unit, or if it is determined that the vehicle control unit does not receive the first data sent by the vehicle signal system, updating a first error count according to a first preset accumulated value;

If it is determined that no communication error occurs when the vehicle signal system sends the first data to the vehicle control unit, or if it is determined that the vehicle control unit receives the first data sent by the vehicle signal system, updating the first error count according to a first preset cumulative decrement value;

If the updated first error count is greater than or equal to the first preset value, it is determined that the first data sent by the vehicle signal system within a continuous preset period are all invalid.

According to a train operation control method provided by the present invention, whether the communication abnormality occurs in the vehicle control unit is determined in the following manner:

If the second data sent by the vehicle control unit within the preset number of consecutive cycles are all invalid, it is determined that the communication abnormality occurs in the vehicle control unit.

According to a train operation control method provided by the present invention, if the Assuming that the second data sent by the vehicle control unit in a cycle are all invalid, determining that the vehicle control unit has the communication abnormality includes:

If it is determined that a communication error occurs when the vehicle control unit sends the second data to the on-board signal system, or if it is determined that the on-board signal system does not receive the second data sent by the vehicle control unit, updating the second error count according to a second preset accumulated value;

If it is determined that no communication error occurs when the vehicle control unit sends the second data to the on-board signal system, or if it is determined that the on-board signal system receives the second data sent by the vehicle control unit, updating the second error count according to a second preset cumulative decrement value;

If the updated second error count is greater than or equal to the second preset value, it is determined that a communication abnormality occurs in the vehicle control unit.

According to a train operation control method provided by the present invention, the safety integrity levels of the on-board signal system and the vehicle control unit are both SIL4.

According to a train operation control method provided by the present invention, a periodic communication mode is adopted between the on-board signal system and the vehicle control unit, and a redundant network design is adopted.

The present invention also provides a train operation control system, comprising: a judgment module and a control module;

The judging module is used to judge whether the first data sent by the vehicle signal system within a continuous preset period are all invalid;

The control module is used to determine that if so, a communication abnormality occurs in the on-board signal system, and send an emergency braking command to the train braking control unit through the vehicle control unit;

The present invention also provides an electronic device, comprising a processor and a computer program stored therein. The memory is configured to implement any of the above-mentioned train operation control methods when the processor executes the program.

The present invention also provides a non-transitory computer-readable storage medium on which a computer program is stored. When the computer program is executed by a processor, the train operation control method described in any one of the above is implemented.

The present invention also provides a computer program product, comprising a computer program, wherein when the computer program is executed by a processor, the train operation control method described above is implemented.

The train operation control method and system provided by the present invention, in order to solve the defect of using a hard-wired interface between the on-board signal system and the vehicle control unit, adopts train Ethernet to realize data exchange between the on-board signal system and the vehicle control unit based on the train real-time data protocol, and ensures that the train control requirements are met when communication abnormalities occur during the data exchange process.

BRIEF DESCRIPTION OF THE DRAWINGS

In order to more clearly illustrate the technical solutions in the present invention or the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

FIG1 is a schematic flow chart of a train operation control method provided by the present invention;

FIG2 is a schematic diagram of the vehicle signal system and vehicle communication topology provided by the present invention;

3 is a schematic diagram of a process flow of a vehicle control unit provided by the present invention for handling communication anomalies;

4 is a schematic diagram of a process flow for handling communication anomalies in a vehicle-mounted signal system provided by the present invention;

FIG5 is a schematic diagram of the structure of a train operation control system provided by the present invention;

FIG. 6 is a schematic diagram of the physical structure of the electronic device provided by the present invention.

Detailed ways

In order to make the purpose, technical solution and advantages of the present invention clearer, the technical solution of the present invention will be clearly and completely described below in conjunction with the drawings of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

FIG1 is a flow chart of a train operation control method provided by the present invention. As shown in FIG1 , the method includes:

Step 100, determining whether the first data sent by the vehicle signal system within a continuous preset period are all invalid;

Step 200: If yes, it is determined that a communication abnormality occurs in the vehicle signal system, and an emergency braking command is sent to the train braking control unit through the vehicle control unit;

The emergency brake command is sent to the vehicle control unit by the on-board signal system when a communication abnormality occurs in the vehicle control unit.

It should be noted that the execution subject of the above method may be a computer device.

Optionally, the onboard signal system and the vehicle control unit communicate using Ethernet based on the Train Real-time Data Protocol (TRDP) protocol that complies with the IEC61375-2-3 specification. The network topology diagram is shown in Figure 2. The onboard signal system at the front of the train and the onboard signal system at the rear of the train communicate with the vehicle control unit respectively. The main communication data content between the onboard signal system and the vehicle control unit is shown in Table 1.

Table 1

In order to ensure that the damage, repetition, disorder, delay and other communication errors occurring during data transmission are large, the safety output of the on-board signal system can smoothly reach the vehicle actuator (such as train brake control unit), and the present invention, on the basis of TRDP agreement, superimposes the railway signal safety communication protocol (RSSP-I) to realize the safe communication of data. In addition, when hard-wired safety input or safety output is realized, it is not necessary to consider the impact of communication delay on data transmission, only data need to be considered to be valid or invalid. Therefore, when using communication mode to realize safety input or safety output, in order to ensure that the safety output of the on-board signal system can smoothly reach the vehicle actuator, it is necessary to design as follows:

Referring to Figure 3, by checking whether the first data sent by the on-board signal system within a consecutive preset period (for example, 3 periods) are all invalid, and when it is determined that the first data sent by the on-board signal system within a consecutive preset period are all invalid, it is determined that a communication abnormality has occurred in the on-board signal system, and the emergency braking command sent by the on-board signal system when the communication abnormality occurs in the vehicle control unit is sent to the train actuator (train braking control unit) through the vehicle control unit to perform emergency braking on the train.

It should be noted that the first data sent by the vehicle signal system to the vehicle control unit may be Specifically including: on-board signal system life signal, maximum normal braking, traction cut-off, door permission, traction/braking command, traction/braking level, driving mode, return mode, door opening command, door closing command, zero speed indication and activation indication.

The train operation control method provided by the present invention, in order to solve the defect of using a hard-wire interface between the on-board signal system and the vehicle control unit, uses train Ethernet to realize data exchange between the on-board signal system and the vehicle control unit based on the train real-time data protocol, thereby ensuring that the train control requirements are met when communication abnormalities occur during the data exchange process.

Furthermore, in one embodiment, step 100 may specifically include:

Step 1001: if it is determined that a communication error occurs when the vehicle signal system sends first data to the vehicle control unit, or if it is determined that the vehicle control unit does not receive the first data sent by the vehicle signal system, then a first error count is updated according to a first preset accumulated value;

Step 1002: if it is determined that no communication error occurs when the vehicle signal system sends the first data to the vehicle control unit, or if it is determined that the vehicle control unit receives the first data sent by the vehicle signal system, then the first error count is updated according to the first preset cumulative decrement value;

Step 1003: If the updated first error count is greater than or equal to the first preset value, it is determined that the first data sent by the vehicle signal system within a continuous preset period are invalid.

Optionally, as shown in FIG3 , if data corruption, duplication, disorder, or long delay occurs when the vehicle signal system sends the first data to the vehicle control unit, it is determined that a communication error occurs when the vehicle signal system sends the first data to the vehicle control unit, and the data is considered to be wrong, and the first error count is updated according to the first preset accumulated value. Or,

When the vehicle control unit does not receive the first data sent by the vehicle signal system, it is also considered that the data is erroneous, and the first error count is updated according to the first preset accumulated value.

The first preset accumulated value and the initial value of the first error count may be freely set according to actual needs, and the present invention does not impose any specific limitation on this.

For example, in one embodiment, the first error count is set to 0, the first preset accumulated value is set to 1, and when it is determined that a communication error occurs when the vehicle signal system sends the first data to the vehicle control unit, or when it is determined that the vehicle control unit does not receive the first data sent by the vehicle signal system, When the first data is obtained, the first error count is updated after adding the first preset accumulated value to the first error count.

If it is determined that no communication errors such as data corruption, duplication, disorder, or large delay occur when the on-board signal system sends the first data to the vehicle control unit, or if it is determined that the vehicle control unit receives the first data sent by the on-board signal system, the first error count is updated according to the first preset cumulative decrement value.

The first preset cumulative reduction value can be freely set according to actual needs, and the present invention does not make any specific limitation on this.

For example, in one embodiment, the first preset cumulative decrement value is set to 1. When it is determined that the above-mentioned communication error does not occur when the on-board signal system sends the first data to the vehicle control unit, or when it is determined that the vehicle control unit receives the first data sent by the on-board signal system, the first error count is updated by subtracting the first preset cumulative decrement value.

If the updated first error count is greater than or equal to the first preset value (for example, 3), it is determined that the first data sent by the on-board signal system within a continuous preset period are invalid, and it is considered that a communication abnormality has occurred in the on-board signal system. The vehicle control unit considers that the emergency braking command sent by the on-board signal system is valid, and outputs the emergency braking command to the vehicle actuator (such as the train braking control unit).

The train operation control method provided by the present invention adopts the RSSP-I protocol to realize safe communication on the basis of the TRDP protocol, and ensures driving safety when the communication of the on-board signal system is abnormal.

Further, in one embodiment, whether a communication abnormality occurs in the vehicle control unit is determined by:

Step 1: If the second data sent by the vehicle control unit within a continuous preset period are all invalid, it is determined that a communication abnormality occurs in the vehicle control unit.

Furthermore, in one embodiment, step 1 may specifically include:

Step 11: If it is determined that a communication error occurs when the vehicle control unit sends the second data to the vehicle signal system, or if it is determined that the vehicle signal system does not receive the second data sent by the vehicle control unit, The second error count is updated according to the second preset accumulated value when the second data is sent;

Step 12: if it is determined that no communication error occurs when the vehicle control unit sends the second data to the vehicle signal system, or if it is determined that the vehicle signal system receives the second data sent by the vehicle control unit, then the second error count is updated according to the second preset cumulative decrement value;

Step 13: If the updated second error count is greater than or equal to the second preset value, it is determined that a communication abnormality occurs in the vehicle control unit.

Optionally, referring to FIG4 , if data corruption, duplication, disorder, or long delay occurs when the vehicle control unit sends the second data to the vehicle signal system, it is determined that a communication error occurs when the vehicle control unit sends the second data to the vehicle signal system, and the data is considered to be erroneous, and the second error count is updated according to the second preset accumulated value. Or,

When the vehicle-mounted signal system does not receive the second data sent by the vehicle control unit, it also considers that the data is erroneous, and updates the second error count according to the second preset accumulated value.

The second preset accumulated value and the initial value of the second error count can be freely set according to actual needs, and the present invention does not make any specific limitation on this.

For example, in one embodiment, the second error count is set to 0, the second preset cumulative value is set to 1, and when it is determined that a communication error occurs when the vehicle control unit sends the second data to the on-board signal system, or when it is determined that the on-board signal system does not receive the second data sent by the vehicle control unit, the second error count is updated by adding the second preset cumulative value.

If it is determined that no communication errors such as data corruption, duplication, disorder, or long delay occur when the vehicle control unit sends the second data to the on-board signal system, or if it is determined that the on-board signal system receives the second data sent by the vehicle control unit, the second error count is updated according to the second preset cumulative decrement value.

The second preset cumulative reduction value can be freely set according to actual needs, and the present invention does not make any specific limitation on this.

For example, in one embodiment, the second preset cumulative decrement value is set to 1, when it is determined that the above communication error does not occur when the vehicle control unit sends the second data to the vehicle signal system, or When it is determined that the vehicle-mounted signal system receives the second data sent by the vehicle control unit, the second error count is updated after subtracting the second preset cumulative decrement value from the second error count.

If the updated second error count is greater than or equal to a second preset value (for example, 3), it is determined that the second data sent by the vehicle control unit within a continuous preset period are invalid, and it is considered that a communication abnormality has occurred in the vehicle control unit. It is determined that the vehicle control unit considers that the emergency braking command sent by the on-board signal system is valid, and outputs the emergency braking command to the vehicle control unit.

It should be noted that the second data may specifically include the vehicle control unit life signal, the vehicle emergency braking status, the vehicle integrity status, the door closing and locking status, the door bypass switch or button status, the cab activation status, the vehicle holding brake status, the vehicle traction cut-off status, the steering handle status, the traction/brake handle status, the door control mode selection switch status, the door opening button status and the closing button status.

The train operation control method provided by the present invention adopts the RSSP-I protocol to realize safe communication on the basis of the TRDP protocol, and ensures driving safety when the communication of the vehicle control unit is abnormal.

Furthermore, in one embodiment, the safety integrity levels of the on-board signal system and the vehicle control unit are both SIL4.

Furthermore, in one embodiment, a periodic communication method is adopted between the vehicle signal system and the vehicle control unit, and a redundant network design is adopted.

Optionally, the communication mode between the vehicle-mounted signal system and the vehicle control unit is a periodic communication mode, and the communication period can be freely set according to actual conditions. In one embodiment, the communication period is set to be less than or equal to 100 ms.

The safety integrity level of the on-board signal system is SIL4.

The safety integrity level of the vehicle control unit is SIL4.

At the same time, in order to improve system availability, the on-board signal system and vehicle control unit adopt a redundant network design.

The train operation control method provided by the present invention, the on-board signal system and the vehicle control unit are developed and designed according to SIL4 level products to improve the on-board signal system and vehicle control The probability of the unit executing safety communications (such as emergency braking) is increased to ensure driving safety. The on-board signal system and the vehicle control unit adopt a redundant network design to improve the availability of the system, solve the defects of the on-board signal system and the vehicle control unit using a hard-wired interface, and improve the flexibility and convenience of the on-board signal system and vehicle interface, greatly saving equipment and labor costs.

The train operation control system provided by the present invention is described below. The train operation control system described below and the train operation control method described above can be referenced to each other.

FIG5 is a schematic diagram of the structure of a train operation control system provided by the present invention, as shown in FIG5 , comprising:

A determination module 510 and a control module 511;

The judging module 510 is used to judge whether the first data sent by the vehicle signal system within a continuous preset period are all invalid;

The control module 511 is used to determine that if yes, a communication abnormality occurs in the vehicle-mounted signal system, and send an emergency braking command to the train braking control unit through the vehicle control unit;

The train operation control system provided by the present invention, in order to solve the defect of using a hard-wire interface between the on-board signal system and the vehicle control unit, adopts train Ethernet to realize data exchange between the on-board signal system and the vehicle control unit based on the train real-time data protocol, thereby ensuring that the train control requirements are met when communication abnormalities occur during the data exchange process.

FIG6 is a schematic diagram of the physical structure of an electronic device provided by the present invention. As shown in FIG6, the electronic device may include: a processor 610, a communication interface 611, a memory 612 and a bus 613, wherein the processor 610, the communication interface 611 and the memory 612 communicate with each other through the bus 613. The processor 610 may call the logic instructions in the memory 612 to Execute the following method:

If so, it is determined that a communication anomaly has occurred in the onboard signal system, and an emergency braking command is sent to the train braking control unit through the vehicle control unit;

Among them, the on-board signal system and the vehicle control unit communicate based on the train real-time data protocol and through the train Ethernet;

In addition, the logic instructions in the above-mentioned memory can be implemented in the form of software functional units and can be stored in a computer-readable storage medium when sold or used as an independent product. Based on this understanding, the technical solution of the present invention can be essentially or partly embodied in the form of a software product that contributes to the prior art. The computer software product is stored in a storage medium, including several instructions to enable a computer power screen (which can be a personal computer, server, or network power screen, etc.) to perform all or part of the steps of the method described in each embodiment of the present invention. The aforementioned storage medium includes: U disk, mobile hard disk, read-only memory (ROM, Read-only Memory), random access memory (RAM, Random Access Memory), disk or optical disk and other media that can store program codes.

Furthermore, the present invention discloses a computer program product, the computer program product comprising a computer program stored on a non-transitory computer-readable storage medium, the computer program comprising program instructions, and when the program instructions are executed by a computer, the computer can execute the train operation control method provided by the above-mentioned method embodiments, for example, comprising:

On the other hand, the present invention further provides a non-transitory computer-readable storage medium having a computer program stored thereon, which is implemented when the computer program is executed by a processor to execute the train operation control method provided in the above embodiments, for example, including:

The system embodiment described above is merely illustrative, wherein the units described as separate components may or may not be physically separated, and the components shown as units may or may not be physical units, that is, they may be located in one place, or they may be distributed on multiple network units. Some or all of the modules may be selected according to actual needs to achieve the purpose of the solution of this embodiment. Those of ordinary skill in the art may understand and implement it without creative effort.

Through the description of the above implementation methods, those skilled in the art can clearly understand that each implementation method can be implemented by means of software plus a necessary general hardware platform, or of course by hardware. Based on this understanding, the above technical solution, in essence or in other words, the part that contributes to the prior art, can be embodied in the form of a software product, which can be stored in a computer-readable storage medium, such as ROM/RAM, a disk, an optical disk, etc., and includes a number of instructions for enabling a computer power screen (which can be a personal computer, Server, or network power screen, etc.) executes the methods described in various embodiments or certain parts of the embodiments.

Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

A train operation control method, characterized by comprising:

Determining whether the first data sent by the vehicle signal system within a continuous preset period are all invalid;

If yes, it is determined that a communication abnormality occurs in the onboard signal system, and an emergency braking command is sent to the train braking control unit through the vehicle control unit;

Wherein, the on-board signal system and the vehicle control unit communicate with each other based on the train real-time data protocol and through the train Ethernet;

The emergency braking command is sent by the vehicle signal system to the vehicle control unit when the communication abnormality occurs in the vehicle control unit.
The train operation control method according to claim 1 is characterized in that the step of judging whether the first data sent by the on-board signal system within a continuous preset period are all invalid comprises:

If it is determined that a communication error occurs when the vehicle signal system sends the first data to the vehicle control unit, or if it is determined that the vehicle control unit does not receive the first data sent by the vehicle signal system, updating a first error count according to a first preset accumulated value;

If it is determined that no communication error occurs when the vehicle signal system sends the first data to the vehicle control unit, or if it is determined that the vehicle control unit receives the first data sent by the vehicle signal system, updating the first error count according to a first preset cumulative decrement value;

If the updated first error count is greater than or equal to the first preset value, it is determined that the first data sent by the vehicle signal system within a continuous preset period are all invalid.
The train operation control method according to claim 1 is characterized in that whether the communication abnormality occurs in the vehicle control unit is determined in the following manner:

If the second data sent by the vehicle control unit within the preset number of consecutive cycles are all invalid, it is determined that the communication abnormality occurs in the vehicle control unit.
The train operation control method according to claim 3 is characterized in that if the second data sent by the vehicle control unit is invalid within the preset number of consecutive cycles, determining that the communication abnormality occurs in the vehicle control unit comprises:

If it is determined that a communication error occurs when the vehicle control unit sends the second data to the on-board signal system, or if it is determined that the on-board signal system does not receive the second data sent by the vehicle control unit, updating the second error count according to a second preset accumulated value;

If it is determined that no communication error occurs when the vehicle control unit sends the second data to the on-board signal system, or if it is determined that the on-board signal system receives the second data sent by the vehicle control unit, updating the second error count according to a second preset cumulative decrement value;

If the updated second error count is greater than or equal to the second preset value, it is determined that a communication abnormality occurs in the vehicle control unit.
The train operation control method according to any one of claims 1 to 4 is characterized in that the safety integrity levels of the on-board signal system and the vehicle control unit are both SIL4.
The train operation control method according to any one of claims 1 to 4 is characterized in that a periodic communication method is adopted between the on-board signal system and the vehicle control unit, and a redundant network design is adopted.
A train operation control system, characterized in that it comprises: a judgment module and a control module;

The judging module is used to judge whether the first data sent by the vehicle signal system within a continuous preset period are all invalid;

The control module is used to determine that if so, a communication abnormality occurs in the on-board signal system, and send an emergency braking command to the train braking control unit through the vehicle control unit;

Wherein, the on-board signal system and the vehicle control unit communicate with each other based on the train real-time data protocol and through the train Ethernet;

The emergency braking command is sent by the vehicle signal system to the vehicle control unit when the communication abnormality occurs in the vehicle control unit.
An electronic device comprises a processor and a memory storing a computer program, wherein the processor implements the train operation control method according to any one of claims 1 to 6 when executing the computer program.
A non-transitory computer-readable storage medium having a computer program stored thereon, characterized in that when the computer program is executed by a processor, the train operation control method as described in any one of claims 1 to 6 is implemented.
A computer program product, comprising a computer program, characterized in that when the computer program is executed by a processor, the train operation control method as claimed in any one of claims 1 to 6 is implemented.