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Newsletter EnginSoft Year 6 n°4 - 43
Development of Digital Mechatronic
Applications using Co-Simulation
The ever decreasing size and cost of embedded
microcontrollers have brought digital electronic equipment
to be used in almost every physical process or machine. In
the real world, the software that runs on the microcontrollers
actually implements the logic, the decision making and the
control functionality of industrial processes, transportation
SimNumerica s.r.l. and his FE partner
EnginSoft s.r.l. outline their approach to the
virtual prototyping of systems where an
embedded microcontroller controls a
multiphysical process or a machine.
systems, machine tools and electrical appliances in general.
Moreover, the availability of low-cost sensors and actuators
that provide a multitude of physical quantities in various
fields to the electrical pins of a microcontroller, has made
embedded electronics a crosswise pervasive ingredient to
many engineering applications.
In this context, a computer program (usually written in C
language) becomes effectively a component of the
engineering application. Therefore, it must be designed,
optimized and verified like any other physical component.
Moreover, these engineering steps have to be performed
taking into account also the fine scale interactions that this
running software develops with the physical components. In
fact, the validation of a system governed by microcontrollers
cannot be approached without taking into consideration the
embedded control firmware and, on the other hand, the
validation of the firmware cannot be performed without
considering its embedding physical system.
Therefore, the development of a digital mechatronics
application is a tricky mixture of physical and abstract
phenomena, since the physics of the software execution are
mostly unobservable in a physical experiment. In a computer
simulation, instead, the execution of the microcontroller
software can be replicated exactly. Moreover, by adding a
model for the simulation of the physical system (such as
those commonly used in the FE-based design), a detailed
evaluation of the interaction between the embedded software
and the physical system becomes possible.
SimNumerica s.r.l. is targeted at the exploitation of muLab,
the Microcontrolled Systems Simulation Laboratory, a
prototype of which has been developed and widely tested at
the University of Padua by a team of experts in numerical
mathematics, electronics and software. muLab has been
tested in a variety of pilot projects, which have already
clearly demonstrated the advantages offered by muLab
compared to general purpose platforms for the development
of numerical algorithms and the hardware-in-the-loop
approach.
muLab performs the co-simulation of the embedded software
directly in the binary format which is executable by the
microcontroller. In this way, the production software can be
designed and tested well before the hardware prototype is
available. Moreover, when the final product is available, a
much larger set of functional tests can be performed in the
co-simulation model, with respect to those feasible in a
physical laboratory.
With muLab, firmware people and mechanical engineers
become aware of their mutual responsibilities concerning the
final performance of their design activity. This is important
since, in principle, software components are not
understandable to mechanical engineers and, vice versa,
electronics engineers often are not adequately familiar with
mechanical components.
FEA and muLab
Finite Element Analysis and the co-simulation implemented
in muLab have the same DNA in common: they reveal the
details of physical phenomena occurring at various space and
time scales. In this way, they allow to observe the
interactions between a software running on a microcontroller
and its embedding physical system, with an approximation
level decided by the user.
In the same digital mechatronics application, the time-scales
involved may be quite distant from each other, e.g. firmware
instructions are executed in microseconds or less, digital
electronics signals present a milliseconds time base,
kinematic/dynamic variables evolve in centesimal fractions of
seconds and thermal variables evolve in several seconds.
For this reason, we use the term Computational Digital
Mechatronics when we refer to this type of co-simulation. It
inherits all the numerical engineering aspects of
computational mechanics, plus:
the co-simulation of a multiphysical engineering system
and of the digital embedded hardware/software that
interacts with this system;
the numerical analysis of the algorithms implemented in
the embedded microcontroller software (firmware), that
runs within the numerical simulation model of the whole
system.