a
Corresponding author: Wang Yi, e-mail: wyigz@126.com
* National Natural Science Foundation(61462015), Guizhou Province International Science and Technology Cooperation
Project(Qian Branch of the G word [2014] No. 7007)
A FlexRay Dynamic Segment Message Scheduling Optimization
Algorithm*
Zhang Liangyu
1,2
, Wang Yi
1,2,a
1
Guizhou City Vocational College, 550025 Guiyang, China
2
School of Physics and Electronic Science, Guizhou Normal University, 550025 Guiyang, China
Abstract. In this paper, we present a new heuristic scheduling algorithm basing on DM algorithm, which makes up
for the deficiency of the currently very little collaborative design of FlexRay dynamic segment scheduling method
with the worst response time and bus utilization. The algorithm improves the comprehensive efficiency of message
worst-case response time and uses bus utilization as the optimization target, and the best FID allocation scheme is
obtained. The MATLAB simulation experiment of the scheduling scheme obtained good simulation results.
1 Introduction
As cars become more intelligent, automated, electronic,
and green, the number of electronic control units (ECUs)
and the number of signals that need to be transmitted
within the car increases rapidly. The number of ECUs
included in some high-end luxury cars already has
exceeded 100 [1] and the number of signals transmitted
inside the car has reached more than 2,500 [2-3].
Traditional CAN, LIN and other automotive buses, due to
their inherent limitations, cannot meet the communication
needs of future cars. FlexRay is well adapted to the future
internal communication needs of cars due to its high
bandwidth, high reliability and high fault tolerance [4-5].
In the automotive industry, FlexRay is the next-
generation automotive bus standard for critical signal
communications such as x-by-wire control systems.
The FlexRay dynamic segment uses a flexible time
division multiple access (FTDMA) media access
mechanism, which enhances bus communication
flexibility [6], but also increases the difficulty and
complexity of dynamic segment message scheduling. At
present, the research of FlexRay dynamic segment is
mostly aimed at improving bus utilization or reducing the
worst response time of messages. It is used as a constraint
to optimize the dynamic segment length and
communication cycle length and parameter configuration.
Based on the above research, this paper proposes a
heuristic scheduling optimization algorithm that takes
into account the bus utilization and worst response time.
2 Message bus utilization model
We assume that the FlexRay communication cycle length
is composed of several Macroticks (MTs). The length of
a MT is 1us. The number of the minimum dynamic slots
is N
ms
(2 or more, less than or equal to 7988) [7], and the
length is t
ms
(2MT). Then the dynamic segment length
T
DS
is:
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