KR101058414B1 - Method and apparatus of locating slot in static segment for reliability in flexray communication - Google Patents

Abstract

The present invention discloses a method and apparatus for placing slots in static segments for improved reliability in FlexRay communication.

According to an embodiment of the present invention, a method of arranging slots in a static segment for improving reliability in FlexRay communication may include calculating a total transmission preparation time for a message to be transmitted in a cycle, and not overlapping the calculated total transmission preparation time. Allocating a message to an unused slot, and transmitting the message in the cycle.

Vehicle Network, FlexRay, Synchronization, Messages, CAN, Transmission Ready Time

Description

METHOD AND APPARATUS OF LOCATING SLOT IN STATIC SEGMENT FOR RELIABILITY IN FLEXRAY COMMUNICATION}

The present invention discloses a method and apparatus for placing slots in static segments for improved reliability in FlexRay communication.

In modern vehicles, various electronic devices such as microprocessors, sensors, and actuators are used, and they require reliable information exchange between each other for safe driving and driver's convenience.

The most widely used in-vehicle communication is the Control Area Network (CAN), which can transmit data at data rates up to 1 Mbps. However, due to the limitations of event-triggered communication methods and relatively low data rates, they are not suitable for applications requiring high reliability and safety, such as x-by-wire systems. As an alternative, FlexRay has been developed, which has the property of deterministic communication and allows periodic data exchange with little jitter. FlexRay is designed to provide the flexibility to use a combination of TDMA and event-based communication methods that provide determinism by time-triggered. However, FlexRay, which is operated by time synchronization, causes a delay in message transmission when the time to prepare for data transmission becomes long, and this delay may affect the transmission of other data.

The present invention proposes a method of arranging slots in a static segment in order to solve a delay occurring in preparing a message transmission in FlexRay communication.

In addition, in consideration of communication efficiency and importance of a message in a communication network, an important message is intended to not be affected by a delay of a transmission preparation time.

In particular, the present invention proposes a method for improving the 'message transmission delay' at the transmitting node which cannot be fundamentally solved through 'frame synchronization' in the protocol layer proposed in the FlexRay protocol specification.

In order to achieve the above object, a method for arranging slots in a static segment for improving reliability in FlexRay communication according to an embodiment of the present invention includes calculating a total transmission preparation time for a message to be transmitted in a cycle, the Allocating a message to a usage slot that does not overlap with the calculated total transmission preparation time, and transmitting the message in the cycle.

According to another embodiment of the present invention, an apparatus for arranging slots in a static segment for improving reliability in FlexRay communication includes a FlexRay controller for controlling transmission and reception of a message, and the FlexRay controller includes a total transmission for a message to be transmitted in a cycle. The preparation time is calculated, and a message is allocated to a usage slot that does not overlap with the calculated total transmission preparation time, so that the message is transmitted within the cycle.

In the present invention, in assigning a message to a slot, a dummy slot is placed in the first half of a FlexRay cycle, and a message transmitted by a high-priority task from a large slot ID (increased slot ID toward the second half of the cycle) is transmitted. As the slot ID is lower, the lower priority task is used so that the message can be transmitted within the intended time even if the preemption or interruption by the higher priority task is applied.

If the proposed method is applied to a situation in which messages of various periods are transmitted from multiple nodes, it is possible to maximize the real-time and determinism by minimizing the delay of the transmission time.

Hereinafter, some embodiments of the present invention will be described in detail with reference to the accompanying drawings. In adding reference numerals to the components of each drawing, it should be noted that the same reference numerals are assigned to the same components as much as possible even though they are shown in different drawings. In the following description of the present invention, a detailed description of known functions and configurations incorporated herein will be omitted when it may make the subject matter of the present invention rather unclear.

In addition, in describing the component of this invention, terms, such as 1st, 2nd, A, B, (a), (b), can be used. These terms are only for distinguishing the components from other components, and the nature, order or order of the components are not limited by the terms. If a component is described as being "connected", "coupled" or "connected" to another component, that component may be directly connected or connected to that other component, but between components It will be understood that may be "connected", "coupled" or "connected".

In terms of data rates, FlexRay can achieve up to 10 Mbps, which is much higher than CAN, and is designed to have dual channels to support fault-tolerant features, even if one communication channel fails. To send and receive.

1 is a diagram illustrating a configuration of a cycle of FlexRay. Static segments and dynamic segments are included in one FlexRay cycle, and static slots and dynamic slots are included in each segment.

2 is a diagram illustrating a condition in which a transmission delay occurs in preparation for transmission in FlexRay.

2 shows an example in which the number of slots used in a node, a transmission preparation time, and a transmission delay are generated accordingly.

In the conventional general methods for transmitting and receiving a message through FlexRay in FIG. 1, 'transmission preparation time (T _r2g )' for message transmission is not considered, but in actual transmission, this may cause an unintended delay Can be. In FIG. 2, a relationship between the number of slots used in a node and a transmission preparation time is shown. T _r2g _a denotes a transmission preparation time required to transmit a frame through an mth slot, and T _{r2g _b} denotes an nth slot. Transmission preparation time required for transmitting a frame through the terminal. The sum of T _r2g _a and T _{r2g _b} becomes 'total transfer preparation time (T _{r2g _ total} )'.

As the number of slots used in one node increases from one to two as shown in FIG. 2, 'total transmission preparation time' increases by an integer multiple, so that Tr2g_a overlaps with the m-th slot on the time axis. This means that the transmission request for the m-th slot is completed after the start of the m-th slot. Therefore, a message to be transmitted through the m-th slot will be delayed in the next cycle. This means that a time duration of a cycle is added to the message transmission time, which hinders the real-time of message transmission and is a factor to be considered when determining the configuration of slots in a cycle.

3 is a diagram illustrating a configuration of a node for FlexRay communication to which a message relocation process according to an embodiment of the present invention is applied.

Node configuration for FlexRay communication is that each node (301, 302) is connected to each other by the FlexRay bus (350) (350) and one node 302 is a host processor (310) and FlexRay internally The controller 330 is connected by a controller-host-interface 320. The FlexRay controller 330 operates independently of the host processor 310 and serves to implement FlexRay protocol service.

As shown in FIG. 2, in order to prevent a delay in message transmission by overlapping with a slot to be transmitted in the process of increasing total transmission preparation time, the total transmission preparation time required for message transmission is calculated as follows. Do not overlap slots during transmission. To this end, in an embodiment of the present invention, the FlexRay controller 330 allocates a dummy slot as follows.

4 is a diagram illustrating a process of allocating a dummy slot according to an embodiment of the present invention.

The first thing to do in order is to calculate the total ready time for the message to be sent in the cycle. To calculate this, first, a transmission preparation time for a message of a specific length is calculated (S410). The transmission preparation time T _r2g for a specific message can be obtained by the following equation.

[Equation 1]

T _r2g = T _ready + c * payload_length

Equation 1 is an embodiment in which the transmitting controller of the FlexRay communication calculates a 'transmission preparation time (T _r2g )' for transmitting a message of a specific length.

T _ready is the time to check the state of the FlexRay cycle and the state of the slot in preparation for transmission. payload_length is the 16-bit unit length of the frame payload to be transmitted, and c is a proportion used to express the memory access time proportional to the length of the payload to be written to the message buffer of the controller. As a factor, the faster the memory bus becomes, the smaller the slower the bus becomes. This is an experimentally determined coefficient since it depends on the system to be implemented.

In transmitting a message, the time required to check the cycle and the state of the slot and the time required to write the message to the message buffer are all necessary elements in the process of transmitting the message through the slot. Equation 1 described above is according to an embodiment of the present invention. When the present invention is applied to FlexRay, when the use of the message buffer or the process of checking the status of the slot / cycle is replaced with another process, transmission of a specific message of S410 The preparation time can be calculated by changing the time it takes to proceed with the replacement process.

Meanwhile, in order to calculate the total transmission preparation time, the number of hypotheses of the message period is calculated (S420). According to an embodiment of the present invention, the number of periods of a message may be calculated by dividing all messages to be transmitted within a cycle by period. A total transmission preparation time (T _{r2g _ total} ) required to transmit one cycle is calculated by combining the value calculated in S420 and the transmission preparation time of S410 previously calculated (S430). The total transmission preparation time according to an embodiment of the present invention can be obtained through Equation 2.

[Equation 2]

T _{r2g _ total} = T _r2g * NumPeriod

Equation 2 multiplies the value of NumPeriod by the previously prepared time of transmission of each message, where NumPeriod is the number of pieces when all messages to be transmitted are divided by period.

Once the total transmission preparation time is calculated, it is necessary to calculate the number of dummy slots to prevent the message transmission preparation time and the message transmission slot from overlapping. Accordingly, the number NumDummy of the dummy slots is calculated using T _{r2g _ total} calculated in S430 (S440). An embodiment of the calculation formula is the same as Equation 3.

[Equation 3]

NumDummy = ceil (T _{r2g _ total} / gdStaticslot)

gdStaticSlot is the size of the static slot, and ceil () is a function that rounds up the decimal point to one unit so that the result is an integer.

According to the calculated number of dummy slots, a dummy slot is disposed in front of the FlexRelay cycle (S450), and a message is allocated to the slot in consideration of the priority of the message at the rear of the FlexRay cycle (S460). Then send and complete the message.

5 is a diagram illustrating an example of allocating a dummy slot according to an embodiment of the present invention. FIG. 5 is a diagram illustrating a case where two dummy slots calculated by the process of FIG. 4 and the number of messages are three.

The dummy slot 510 is set to the front slot of the FlexRay cycle. No message is assigned to the dummy slot. The message transmitted by the task having the highest priority is allocated to the slot 522 located at the rear of the used slot 520 except the dummy slot. Then, the message transmitted by the next highest priority task is allocated in front of one slot, so that the message 521 transmitted by the lowest priority task is placed in the immediately adjacent slot adjacent to the dummy slot. Assigned and sent. In FIG. 5, two dummy slots and three available slots are used to transmit a message. If the time to prepare to transmit a message in the cycle shown in FIG. 5 is the total length of the dummy slot (length of two slots) If larger than 1), one more dummy slot is inserted and the use slot 520 is pushed back by one slot. Thus, messages of all tasks can be transmitted without being affected by the transmission preparation time. However, if the number of slots in the FlexRay cycle is fixed by a certain number, there is a limit to inserting a dummy slot. In this case, messages from the lowest priority task can be sent in the next cycle. Thus, messages of high priority tasks, which are urgently sent, can be transmitted without being affected by the transmission preparation time.

Meanwhile, according to an exemplary embodiment of the present invention, when the number of dummy slots is not calculated every cycle, and no increase or decrease occurs in comparison with the size and number of previously transmitted messages, the dummy slots are set to the number set in the previous process. You can keep going. This is because the size and number of messages in a similar range do not change in preparation time for transmitting a message, so that the delay of the message does not occur even if the number of dummy slots is kept in the previously calculated number without separately calculating the number of dummy slots. Because.

According to another embodiment of the present invention, the message to be transmitted may be determined not only as the priority of the task but also by various criteria other than the priority. For example, if a message is delayed in the first cycle, which is the previous cycle, even if the message is a task of a lower priority, the cycle to be sent this time (the second cycle) is placed in the rearmost slot regardless of the priority. Can be adjusted to be assigned.

Which message is allocated according to the position of the slot in the used slot can be applied to various determination criteria such as the task priority of the message, the number of delays, the importance of the message itself, and the present invention is not limited to the specific criteria.

In an embodiment of the present invention, in assigning a message to a slot, a dummy slot is placed at the beginning of a FlexRay cycle, and the task having a high priority from a large slot ID (increasing the slot ID toward the second half of the cycle) The lower slot ID is used by lower priority tasks, so that messages can be transmitted within the intended time even if the preemption or interruption of the higher priority task is applied. Suggested.

If the proposed method is applied to a situation in which messages of various periods are transmitted from multiple nodes, it is possible to maximize the real-time and determinism by minimizing the delay of the transmission time.

The foregoing description is merely illustrative of the technical idea of the present invention, and various changes and modifications may be made by those skilled in the art without departing from the essential characteristics of the present invention. Therefore, the embodiments disclosed in the present invention are not intended to limit the technical idea of the present invention but to describe the present invention, and the scope of the technical idea of the present invention is not limited by these embodiments. The protection scope of the present invention should be interpreted by the following claims, and all technical ideas within the equivalent scope should be interpreted as being included in the scope of the present invention.

1 is a diagram illustrating a configuration of a cycle of FlexRay.

2 is a diagram illustrating a condition in which a transmission delay occurs in preparation for transmission in FlexRay.

3 is a diagram illustrating a configuration of a node for FlexRay communication to which a message relocation process according to an embodiment of the present invention is applied.

4 is a diagram illustrating a process of allocating a dummy slot according to an embodiment of the present invention.

5 is a diagram illustrating an example of allocating a dummy slot according to an embodiment of the present invention.

Claims (12)

Calculating a total transmission ready time for a message to transmit in a cycle; Allocating a message to a usage slot which will start transmission after completion of the calculated total transmission preparation time; Sending the message in the cycle, wherein the slot is placed in a static segment for improved reliability in FlexRay communication. The method of claim 1, Allocating the message Calculating the number of dummy slots required in the cycle using the total transmission preparation time and the number of messages; And wherein the dummy slot has the smallest slot ID in the cycle and no message is assigned. The method of claim 1, If the message is more than one, the slot having the highest priority is allocated to the slot having the largest slot ID in the cycle. . The method of claim 1, The calculating of the total transmission preparation time may include time required to check a state of a cycle, time required to check a state of a slot, or storing the message in a message buffer of a controller to transmit one of the messages. Calculating slot readiness time, including at least one of the time being. The method of claim 1, Wherein the total transmission ready time further comprises calculating the number of hypotheses of the message period, wherein slots are placed within static segments for improved reliability in FlexRay communication. The method of claim 1, In the case where there is more than one message, the slot having the largest slot ID in the cycle is assigned a message whose transmission is delayed in the cycle before the cycle. How to place it. FlexReay controller to control the sending and receiving of messages with FlexReay communication, The FlexRay controller Calculating a total transmission preparation time for a message to be transmitted in a cycle, and assigning the message to a use slot that starts transmission after completion of the calculated total transmission preparation time, thereby controlling the message to be transmitted within the cycle. And slots within static segments for improved reliability in FlexRay communications. The method of claim 7, wherein The FlexRay controller calculates the number of dummy slots required in the cycle by the total transmission preparation time and the number of messages to allocate the message, Wherein the dummy slot has the smallest slot ID in the cycle, and no message is assigned, wherein the slot is located in a static segment for improved reliability in FlexRay communication. The method of claim 7, wherein In case of more than one message, the device for arranging slots in a static segment for improving reliability in FlexRay communication, characterized in that the highest priority message is allocated to the slot having the largest slot ID in the cycle. . The method of claim 7, wherein The FlexRay controller takes time to check the state of a cycle, time spent to check the state of a slot, or sends the message to the controller's message buffer to calculate one of the messages to calculate the total transfer ready time. An apparatus for arranging slots within static segments for improved reliability in FlexRay communications, comprising calculating a transmission ready time including one or more of the time spent in storage. The method of claim 7, wherein And the FlexRay controller calculates the total transmission preparation time based on the number of provisions of the message period, wherein the slot is arranged in a static segment to improve reliability in FlexRay communication. The method of claim 7, wherein In the case where there is more than one message, the slot having the largest slot ID in the cycle is assigned a message whose transmission is delayed in the cycle before the cycle. Device for placing it.

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