Page 72 - Mechatronic Systems Modelling and Simulation with HDLs

3.5 SIMULATOR COUPLING 61

Mechatronics

In [302] Olcoz et al. describe the coupling of the VHDL simulator VSS with
the mechanics simulator COMPAMM. Sensors and actuators are incorporated at
the interface between electronics and mechanics and these are characterised by a
pair of corresponding variables — one for each of the two simulator sides. The
correspondence of such pairs is achieved by an interface written in C and C ++.
The mechanics simulators can thus be operated using a fixed or variable time
interval. In the former case the synchronisation between electronics and mechanics
takes place at discrete, evenly distributed points in time that are specified by the
fixed interval of the mechanics. In the latter case the mechanics simulator proceeds
by a time interval and then informs the electronics simulator that it may proceed to
this point. After confirmation from the electronics simulator the sequence begins
again from the start.
A further approach for the coupling of simulators is mentioned by Scholliers in
[367]. This approach emphasises the coupling of multibody mechanics, analogue
electronics and control technology. ADAMS, PSpice and MATLAB/Simulink are
the simulators used. The simulation process is centrally controlled and a fixed
increment thereby specified. The application considered is a controlled drive and
the mechanical load is a mechanism described in ADAMS. The actuator is a direct
current motor described in the form of Spice components, whereas the PI controller
exists on a purely functional level in MATLAB/Simulink.
Le Marrec et al. [218] describe a coupling between C routines, the VHDL
simulator VSS and MATLAB/Simulink using a co-simulation bus that exchanges
data between the individual simulators. The simulation can take place on two
levels. Firstly, simulation can be purely functional, with electronics, mechanics,
and software being investigated for the application under consideration. In the
other case, the timing has to be taken into account too, necessitating a processor
model in VHDL for the software. In this case the problem is merely that of the
co-simulation of electronics and mechanics. The approach described is illustrated
on the basis of two examples, an electronic accelerator pedal for an electric car
and the control of a hydraulic suspension system for a car.
In [360] Scherber and M¨ uller-Schloer proposed a simulator backplane that rep-
resents a mechanism for the linking of very different simulators. The approach is
based upon a unified model for the heterogeneous components involved. These are
termed actuators; their interfaces are called ports; every two ports can be linked
by a channel. The access mechanisms are always the same. Thus the interfacing
of a component and its simulation is unified without having to make limitations
with regard to the nature or function of the actuators. A scheduler decides which
actuators shall be executed when and for how long by means of a priority anal-
ysis. In this manner a software simulator, a simulator for finite state machines, a
simulator for the Modelica language — see Section 3.4.3–and MATLAB/Simulink
were connected together.