Create Parent and Child Operating Modes in State Transition Tables

Step 3 of 4 in Model Rechargeable Battery System by Using a State Transition Table

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You can create more complex logic in a state transition table by creating child states that can activate only when their parent state is active. In the States column, states are indented under their parent states.

Child states have their own default transitions. When the parent state becomes active, the child state connected to the default transition also becomes active. Then, the table transitions between the child states. When the parent state deactivates, the child states also deactivate.

In this example, you use child states to model the variable charging rates in a rechargeable battery system.

Open Model

The sfGetStartedBatteryTable model represents the control logic for a rechargeable battery system. To build the model, follow the instructions in the previous steps of the tutorial.

The State Transition Table block Battery Control contains the control logic for the system. To determine whether the battery charges or discharges, the table receives a Manual Switch block as an input.

To view the table, double-click the State Transition Table block.

The states Charge, Discharge, and Empty represent the operating modes of the battery system. The table uses these data:

• isCharging: An input that determines whether the battery should charge or discharge.

• chargePct: A local data that represents the charge level of the battery as a percent of total charge.

• sentPower: An output that determines how many watts of power the battery sends at any given time.

Add Child States to Model Hierarchy

Currently, the battery system continues charging when full. To prevent the battery from charging beyond full, add states representing fast, intermediate, and full charging modes.

1. Point to the Charge state and click Add child state. Name the child state FastCharge.

   

2. Add two additional child states named SlowCharge and Full.

   

   Note

   To hide child states, on the left side of the parent state, click the Hide child states button . To show hidden states, click the Show child states button .

Add transitions that allow the table to move between the charging modes.

1. Create a transition from FastCharge to SlowCharge that executes when the battery charge is greater than 80%.

2. Create a transition from SlowCharge to Full that executes when the battery charge is greater than or equal to 100%.

   

Add state actions that increase the battery charge.

1. In the Charge state, remove the existing during actions.

2. In the FastCharge state, add a during action that increases the battery charge by 4%. In the SlowCharge state, add a during action that increases the battery charge by 1%.

   

Simulate Model

Observe how the table transitions between child states.

1. To slow the pace of the simulation, in the Simulation tab, click Run > Simulation Pacing. Then, select Enable pacing to slow down simulation.

2. In the top model, confirm that the Manual Switch block connects to the Constant block with a value of 1.

3. In the Simulation tab, click Run to simulate the model. In the first step, the Charge and FastCharge states both activate. As charge increases, the table transitions to child states SlowCharge and Full.

The battery model now stops charging when the battery charge is 100%. In the next step of the tutorial, you add a non-rechargeable emergency battery that maintains essential functions if the main battery runs out of power. To model the simultaneous operation of the batteries, you use parallel states.