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EAST-ADL and automotive system modelling (Part 2)

Posted: 06 Jun 2013     Print Version  Bookmark and Share

Keywords:EAST-ADL  ABS  AUTOSAR  verification  validation 

Read Part 1 of this series here.

Behaviour description and analysis
With EAST-ADL, developers are able to capture and formalise various behaviour concerns, motivated by the needs of requirements engineering, quality predictions, design verification and validation, safety engineering. For the formalisation of behaviour descriptions, EAST-ADL provides a hybrid-system model that integrates both discrete-event and continuous-time behaviour models. All behaviour descriptions are managed seamlessly together with the specifications of requirements, system design and constraints, and verification and validation cases. Figure 1 shows an example where function type ABS is constrained by ABS_BehaviorConstraint.

Figure 1: Annotating behaviour constraints on the ABS function.

EAST-ADL captures formally three categories of behavioural constraints. It is up to the engineers, in their particular design and analysis contexts, to decide the exact types and degree of constraints to be applied. These categories of behavioural constraints are:

Attribute Quantification Constraint: relating to the declarations of value attributes and the related acausal quantifications (e.g., U=I*R).

Temporal Constraint: relating to the declarations of behaviour constraints where the history of behaviours on a timeline is taken into consideration.

Computation Constraint: relating to the declarations of cause-effect dependencies of data in terms of logical transformations (for data assignments) and logical paths.

Let's consider an example of the attribute quantification constraint to be met by the ABS function. In figure 2, the VehicleSpeedIn and WheelSpeedIn are two monitored variables received from the ports. These two external variables together with the constant WheelRadius decide the estimated SlipRate according to the quantification Condition[SlipRateQuantification].

Figure 2: Annotating attribute quantification constraint on the ABS function. (Click on image to enlarge.)

In figure 3, the behaviour constraint is further elaborated by capturing the ABS control logic in terms of a state machine. The state invariants and transition guards are precisely defined by some attribute quantification specifications, such as Conditon[VehicleSpeedIn > ABSVehicleSpeedThreshhold] and Conditon[SliprateThreshhold <= SlipRate <=1].

Figure 3: Annotating temporal constraint on the ABS function. (Click on image to enlarge.)

Figure 4 shows the related computation constraints on the ABS function. The specification declares two allowed invocations to the transformation Set_ABSBrakeTorqueOut() that calculates the ABS brake torque request.

Figure 4: Annotating computation constraint on the ABS function. (Click on image to enlarge.)

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