Page 125 - Mechatronic Systems Modelling and Simulation with HDLs

114 6 MECHANICS IN HARDWARE DESCRIPTION LANGUAGES

Mechatronics

In [254] Makki et al. describe an electronically controlled window winder mecha-
nism for cars. On the mechanical side a direct current motor, a gearbox, a rack for
the conversion of the rotational motion into a translational movement, a mechan-
ical load — the window pane — and a mechanical stop are envisaged. In addition
to this there is a force sensor that allows the drive to be switched off in the event
of large counterforces. This typically corresponds with a situation in which objects
are trapped by the window-pane whilst the window is raised. In this case move-
ment is restricted to a rotary — or after the rack a translational — dimension. For
this reason the system described can be simply assembled from basic models, each
of which corresponds with one of the named components.
Other examples can be found in Donnelly et al. [84], who describe an electroni-
cally controlled hydraulic braking system, or in Mikkola [269], who uses hardware
description languages to model and simulate diesel-electric ship drives.

Micromechatronics

For the class of so-called ‘suspended’ MEMS, Mukherjee and Fedder [282] have
developed an approach based upon multibody mechanics. Classical applications
for this approach are, for example, seismically suspended masses of acceleration
sensors and resonators, see Figure 6.6. The structure of interest is broken down
into individual parts such as springs, masses, dampers, etc., for which models
are available. Thus a micromechanical model can be assembled from the basic
models. This strategy is very well suited to the approach that is also selected
here of formulation in hardware description languages, because these continuously
support the hierarchical structure of models.
In the NODAS system in [103], Fedder and Jing go beyond multibody systems
made up of rigid bodies by including elastic components on the basis of hard-
ware description languages. The following components have been implemented
in NODAS as described in [103]: A bending beam, a rigid plate, an electrostatic

U

F
e
m

k b

Figure 6.6 Electrically excited resonator in the form of a multibody system