modelEngineThrottleControl
Extends from Modelica.Icons.Example (Icon for runnable examples).
Information
This example shows how to model a non-periodic synchronous sampled data systems
with the Modelica_Synchronous library. This is demonstrated at hand
of a closed-loop throttle control synchronized to the crankshaft angle of an
internal combustion engine. This system has the following properties:
- Engine speed is regulated with a throttle actuator.
- Controller execution is synchronized with the engine crankshaft angle.
- The influence of disturbances, such as a change in load torque, is reduced.
The complete system is shown in figure below (diagram-layer):
Block speedControl is the discrete control system. The boundaries
of this controller are defined by sample1, sample2 and
hold1. The sampling is done via rotationalClock, an
event-based clock that ticks every 180° rotation of the crankshaft angle. The
speed controller therefore is automatically executed every half-rotation of the
engine's crankshaft. To produce respective clock ticks,
rotationalClock
bookeeps the angular of the last time a half-rotation of
the crankshaft has been recognized (angular_offset). Given
angular_offset, the event-condition for half-rotations is:
abs(angle - angular_offset) >= abs(trigger_interval)
with trigger_interval = 180°. The model of
rotationalClock therefore is (diagram-layer):
In the end, rotationalClock samples it's own input angle to bookeep
an offset used to decide when to tick; the clock's event condition depends on
the state present when the condition changed last time from beeing non-satisfied
to beeing satisfied, i.e., the state when the clock last ticked.