Page 44 - SAEINDIA Magazine December 2020

TECHNOLOGY

Trends

section controls the actuators on the vehicle that are architecture, wherein the distributed network nodes
used for steering, braking, suspension and ride control, monitor each other. If a single ECU fails, other ECUs
etc. For UI, customers are given the choice through react by adapting their mode of operation. Though the
Gesture Control or Voice or Haptic feedback, or plain number of ECUs is reduced, the complexity of individual
touch screen. The actuators and sensors are controlled ECUs will increase. For example, Brake-by-Wire (BBW)
and monitored by closely mounted decentralized systems typically benefit from a network-centric
Electronic Control Units (ECUs). Depending on the approach if each brake is set up as an independent unit,
level of safety being offered by a specific system in which is capable of coordinating with other brakes.
the vehicle, the redundancy of ECUs is determined, Similar redundancy strategies have to be applied
especially for safety-critical systems as no single unit for sensors, on the lines of ECUs, to ensure safe
can achieve the required failure rates. However, it is operation. Measurements are required with 3 sensors
important to keep the degree of hardware redundancy simultaneously to allow majority voting among the
minimal to optimize the costs.
measurements and thus to detect faults. To reduce HW
In general, two components for one task, in combination costs, one or two sensors could be replaced by SW
with a sufficiently powerful diagnostic and decision algorithms.
unit and a fail-safe behaviour of each component are A vehicle must have proper networking to connect all
assumed to be able to achieve the required failure the electronic components with at least one redundancy
rates. A combination of two or more units is regarded including physical separation in the wiring. The overall
as a Fault Tolerance Unit (FTU). In certain instances, network has to support a precise timing of messages to
an FTU can also be constructed based on only one ECU ensure that the lost or delayed messages are detected
if the ECU features a multi-core architecture and an and a maximal roundtrip time is guaranteed. Examples
appropriate board design in combination with special of such networks include TTCAN, TTP/C, FlexRay, and
mechanisms to allow the execution of multiple safety Ethernet in combination with time-triggered extension.
critical functions independently on this platform.
The safety-critical applications within the network
An alternate approach to reducing the number are synchronized using precise data timings to ensure
of redundant ECUs is to have a network-centric defined latencies which are enabled by operating

42 DECEMBER 2020 MOBILITY ENGINEERING