IEEE Electrification Magazine - December 2017 - 48

This model-based
design enables the
fast and costeffective generation
of dynamic control
systems, signal
processing,
communications
systems, and so on.

computations, such as arithmetic
calculations and algorithms. The
FPGA is basically a coprocessor
that runs real-time functions,
addresses the operating system,
provides the new functions, and
reduces the computational time
required by the digital core. The realtime fast tasks are executed by the
FPGA, while the tasks that require
slower responses are executed by
the digital core.
Major components inside the
digital core module include a CPU
that performs the arithmetic calculations, RAM and flash memory for
storing the data, transmitters, and
receivers. The FDAC system includes an
FPGA, ADCs, DACs, and analog multiplexers. As analyses
are completed by the digital core and FPGA, corresponding
signals that are in digital formats are transformed to analog by DACs and are sent back to the aircraft equipment to
command the valves, actuators, motors, and more.

Challenges for the Aerospace Industry
The proposed CCPS, which integrates digital-signal-processing functions by the digital core and FPGA, is a very
attractive approach, but it will increase the design complexity. The robustness of the design needs to be tested and
verified, and the implementation should meet safety
requirements of the aerospace DO-254 standard, Design
Assurance Guidance for Airborne Electronic Hardware,
enforced by the U.S. Federal Aviation Administration. These
standards are for compliance and guidance for the design
assurance of complex electronic hardware such as FPGAs
and digital cores in airborne systems. Therefore, very rigorous design and verification are needed to comply with safety codes and regulations. In the aerospace industry, an
FPGA design can cost up to CAD$1 million; in many cases,

roughly 70% of cost and effort is
spent on verification, while only
roughly 30% of the cost is spent on
design. Verification teams are often
almost twice as large as the FPGA
design teams, and, in many aerospace electronics manufacturers,
FPGA design verification is performed manually, which is time consuming, expensive, and inefficient.
To reduce the verification cost,
there has been a shift in the aerospace industry toward automated
processes and approaches. Our CCPS
system offers real-time simulations
coupled with ARM-based microprocessors and the use of an FPGA as a
coprocessor to run real-time functions, address the operating system, and provide the new
functions (like digital signal processing). Verification is the
most crucial phase to the DO-254 process, because this is
where the design is checked against the initial formal
requirements. Many challenges are encountered during
the hardware verification process of FPGA designs under
DO-254 guidelines. Using the CCPS, the verification is facilitated through improvements in debugging and code coverage. This process provides an automated environment to
design and test all FPGA-level requirements with full visibility in compliance with the DO-254 standard. This reduces the verification cost while improving the delivery time.
In many aircraft controller modules, microprocessors
are used as a core computational module, and individual
submodules such as ADCs, DACs, and SPIs are tied together and operate in series. This reduces the speed of computations and results in a distributed system design with
limited capability in terms of the number of control strategies. However, using a CCPS as a central unit allows all of
the computations to be performed in parallel within a single m o d u l e w i t h t h e a d d i t i o n o f a n FPGA. This

Aircraft Equipment

Vb
Vexc.

Actuator
System

Condition Monitoring

Va
RVDT

ADCs

SPI
FPGA

DACs

SPI

Microprocessor

SPI

EHSV
Figure 2. An example of aircraft equipment control with an EHSV using CCPS. Va, Vb: terminal voltages; Vexc.: excitation voltage.

I E E E E l e c t r i f i c ati o n M a gaz ine / DECEMBER 2017

Table of Contents for the Digital Edition of IEEE Electrification Magazine - December 2017