3.9.2.3 Gear Shift

3.9.2.3 Gear Shift

As part of a demo from the MathWorks that uses Simulink to model an automotive drivetrain, its Stateflow diagram as displayed in the following enhances the Simulink model by capturing the transmission control logic. The diagram contains two parallel states, gear_state and selection_state. gear_state consists of four exclusive states that indicate the gear status respectively, and the transition between them is guarded by events UP and DOWN. selection_state determines the direct broadcast of events UP and DOWN, according to the speed value and thresholds down_th and up_th. In addition, the broadcast is also restricted by some real-time constraints; for example, the transition that broadcasts event DOWN to state gear (denoted by {gear.DOWN}) is constrained by the temporal constraint after(TWAIT, tick) that checks if state downshifting has been active for at least TWAIT (a constant) period.

Our translated PAT model of this Stateflow diagram is available here. We precisely and concisely capture several Stateflow modeling features possessed in this diagram, such as deterministic execution order between parallel states and between multiple outgoing transitions from the same source state, (direct) event broadcast, and temporal constraints.