Simcenter Madymo Simcenter Madymo - Control System example of a hole valve in a 2 chambered airbag
Summary
This Simcenter Madymo example is meant to demonstrate the usage of a CONTROL_SYSTEM within an airbag model. CONTROL_SYSTEMS can be applied to a large variety of usage case like belts, airbags and other vehicle components. The control modules enable to act based on events happing during the simulation that are not known on forehand. This KBA shows an airbag use case where venting acts based on sensing 2 airbag chamber pressures. Model setup: A simplified airbag with two chambers. Both chambers do have an inflator. A hole is located at the exchange area between the 2 chambers. Initially the hole is closed. Gas is supplied by the inflator of the first airbag chamber. The 2nd chamber also contains an inflator but is triggered later on in time. Once the pressure of the 2nd chamber get's higher than the pressure of the first chamber the hole opens and gas of the 2nd chamber starts flowing into the 1ste chamber.
Details
General:
CONTROL_SYSTEMs can act based on controllers, signals and operators. These input can make use of sensors, signal and other operator too, etc.. The outcome of a controller can be fed into FUNCTION.CONTROL_SIGNAL that resides under various XML elements. This approach enables to act based on events happing during the simulation that are not known on forehand. Control systems can be defined under MADYMO root element and SYSTEM.MODEL elements. FUNCTION.CONTROL_SIGNAL can be define e.g. under a SYSTEM.MODEL but also e.g. within a FE_MODEL.
Airbag two chamber model: The green and blue part form the exchange area. The blue part is a hole. The green part is of fabric material.
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Model description:
In the GROUP_DEFINE, with global scope, 2 DEFINES are specified to trigger the airbag inflators.
Within the airbag fe_model 2 sensors are specified that sense the absolute pressure within the airbag chambers.
Within the airbag system a control system is specified that calculates the pressure ratio P_ch2/P_ch1
The result of Multiply_opr is fed into the SWITCH.CONTROL_SYSTEM within the airbag fe_model. If P_ch2/P_ch1 is larger than 1 for 1ms the switch will become TRUE. In this case the switch can switch only ONCE.
This state change is detected by the following sensor:
The sensor signal is read via the FUNCTION.CONTROL_SIGNAL into the hole CDT_FUNC.
The various steps within the control process can be outputted e.g. by OUTPUT_CONTROL_SYSTEM, OUTPUT_SENSOR, OUTPUT_SWITCH and OUTPUT_AIRBAG_CHAMBER.
Some examples of output:
The used xml input deck for this example is attached as well.
Note: The pressure in an airbag chamber is typically also effected e.g. by contact interactions with the car-environment and the atd but these interaction are excluded in this example.
Please contact your local Simcenter Madymo support organization for further questions/details on using CONTROL_SYSTEMs.