Transmission duration report and transmission target time allocation for controller area network synchronization

Patent metadata

Field	Value
Publication number	US-10855490-B2
Application number	US-201916354847-A
Country	US
Kind code	B2
Filing date	Mar 15, 2019
Priority date	Mar 15, 2019
Publication date	Dec 1, 2020
Grant date	Dec 1, 2020

Abstract

A CAN network synchronization method identifies a sync master node from a plurality of nodes, and designates each of the remaining nodes as a sync slave node. The method further designates a message from the sync master node as a sync message, and assigns a lowest number to the message ID of the sync message. The method further assigns a unique node ID to each sync slave node, and assigns a unique message ID to a transmission duration report message from a sync slave node. The method further assigns a unique message ID to a transmission target time allocation message from the sync master node. The method also performs a handshake operation between the sync slave nodes and the sync master node to exchange message burst transmission durations (T sst ), transmission target times (T TXtarget ), and a common time reference point, and conducts time adjustment on each sync slave node.

First claim

What is claimed is:

1. A computer-implemented method for synchronizing nodes on a controller area network (CAN) comprising:
identifying, via a processor, a node from a plurality of nodes as a sync master node, and designating, via the processor, each of the remaining nodes as a sync slave node;
designating, via the processor, a first message in a periodic message burst from the sync master node as a sync message;
assigning, via the processor, a lowest number, among a plurality of message identifiers (IDs) in the CAN network, to a message ID of the sync message;
subscribing to the sync message on each sync slave node;
assigning, via the processor, a unique slave node ID to each sync slave node;
assigning, via the processor, a unique message ID to each of a plurality of transmission duration report messages;
subscribing to the plurality of transmission duration report messages on the sync master node;
assigning, via the processor, a unique transmission target time allocation message ID to a transmission target time allocation message from the sync master node;
subscribing to the transmission target time allocation message on each sync slave node;
performing a handshake operation between the sync slave nodes and the sync master node to exchange message burst transmission durations (T sst ), transmission target times (T Txtarget ), and a common time reference point; and
performing a time adjustment on each sync slave node based on a slave node message burst transmission time (T TX ), a transmission target time (T TXtarget ), and a sync message receiving time (T syncMsgRx ) used as the common time reference point from which (T TX ) and (T TXtarget ) are measured.

2. The computer-implemented method of claim 1 , wherein performing the handshake operation further comprises:
transmitting a sync message from the sync master node;
triggering an interrupt to the processor of each sync slave node in response to receiving the sync message to retrieve the sync message receiving time (T syncMsgRx ) that is used as the common time reference point between (T TX ) and (T TXtarget );
transmitting, from each sync slave node among the plurality of sync slave nodes to the sync master node, a transmission duration report message that includes the assigned message ID, the slave node ID and its message burst transmission duration (T sst );
retrieving, via a sync master processor, the (T sst ) in a transmission duration report message from each sync slave node;
determining, via the sync master processor at the end of processing all received messages, a transmission target time (T TXtarget ) for each sync slave node;
transmitting, via the sync master processor, a transmission target time allocation message that includes the assigned transmission target time allocation message ID, an assigned slave node ID and its corresponding transmission target time (T TXtarget ) from the sync master node to each sync slave node; and
retrieving, via each sync slave processor, the (T TXtarget ) included in the transmission target time allocation message from the sync master node.

3. The computer-implemented method of claim 2 , wherein determining the transmission target time (T TXtarget ) comprises determining based at least in part on an optimal spacing time (T spacing ) between neighbor message bursts in an N node network.

4. The computer-implemented method of claim 3 , wherein the optimal spacing time duration is derived by:
T spacing =( T cycle −( T smt +T sst1 +T sst2 + . . . +T sstN-2 +T sstN-1 ))/ N ; wherein:

T cycle is a transmission cycle duration equal and tied to a predetermined CAN task cycle time;
T smt is a sync master node message burst duration;
T sst1 is a sync slave node 1 message burst duration, received from sync slave node 1;
T sst2 is a sync slave node 2 message burst duration, received from sync slave node 2;
T sstN-2 is a sync slave node N−2 message burst duration, received from sync slave node N−2;
T sstN-1 is a sync slave node N−1 message burst duration, received from sync slave node N−1; and
wherein a message burst transmission target time T TXtarget is derived by:
T TXtargetJ =( T smt- +T sst1 + . . . +T sstJ-1 )+ J*T spacing ; wherein:

T smt- represents (T smt −T st ), T st represents the sync message transmission duration, and
J is a sync slave node ID.

5. The computer-implemented method of claim 4 , wherein the sync message transmission duration (T st ) and the message burst transmission duration (T smt ) for the sync master node are predetermined measured durations and configured into the sync master node, and the message burst duration (T sst ) for a sync slave node is a predetermined measured duration and configured into the sync slave node.

6. The computer-implemented method of claim 4 , wherein performing the time adjustment on a sync slave node comprises:
using the retrieved sync message receiving time (T syncMsgRx ) as the time reference point for a slave node message burst transmission time (T TX );
comparing the slave node message burst transmission time (T TX ) to its message burst transmission target time (T TXtarget ) on the sync slave node; and
moving the message burst transmission time closer to its message burst transmission target time by increasing a CAN task current cycle time with a predefined time adjustment if the slave node message burst transmission time (T TX ) occurs before its message burst transmission target time (T TXtarget ) on the sync slave node or by decreasing the CAN task current cycle time with a predefined time adjustment if the slave node message burst transmission time (T TX ) occurs after its message burst transmission target time (T TXtarget ) on the sync slave node.

7. The computer-implemented method of claim 6 , wherein the slave node message burst transmission time (T TX ) is determined as (T cycle )−(T syncMsgRx ), wherein (T cycle ) is a transmission cycle duration equal and tied to the predetermined CAN task cycle time, and (T syncMsgRx ) is the sync message receiving time used as the common time reference point between (T TX ) and (T TXtarget ).

8. A controller area network (CAN) synchronization comprising:
a plurality of nodes, each node including a processor;
at least one of the processors in a respective node in signal communication with at least another processor among the plurality of nodes, the at least one processor configured to:
identify via the processor, a node as a sync master node from the plurality of nodes, and to designate each of the remaining nodes as a sync slave node;
designate a first message included in a periodic message burst from the sync master node as a sync message;
assign a lowest number, among a plurality of message IDs in the CAN network, to a message ID of the sync message;
subscribe to the sync message on each sync slave node;
assign a unique node ID to each sync slave node;
assign a unique message ID to each of a plurality of transmission duration report messages;
subscribe to the plurality of transmission duration report messages on the sync master node;
assign a unique transmission target time allocation message ID to a transmission target time allocation message from the sync master node;
subscribe to the transmission target time allocation message on each sync slave node;
wherein the system performs a handshake operation between the sync slave nodes and the sync master node to exchange message burst transmission durations (T sst ), transmission target times (T TXtarget ), and a common time reference point; and
performs a time adjustment on each sync slave node based on a slave node message burst transmission time (T TX ), the transmission target times (T TXtarget ), and a s

Assignees

• Hamilton Sundstrand Corp
• Hamilton Sunstrand Corp

Inventors

• Leng Qiuming

Classifications

• H04L12/403

  with centralised control, e.g. polling · CPC title

• H04L2012/40215

  Controller Area Network CAN · CPC title

• H04L12/40013

  Details regarding a bus controller · CPC title

• H04L2012/4028

  the transportation system being an aircraft · CPC title

• H04L12/40019 Primary

  Details regarding a bus master · CPC title