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Spec_PowerPort.md

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Specification of Power Port

1. Overview

1. Functions

  • PowerPort class provides features of an electrical power connection.
  • Users can use the class to control the electrical power switching of components and calculate the component's consumed electrical current.

2. Related files

  • Main files: power_port.cpp, .hpp
  • Referenced files: component.cpp, .hpp and power_control_unit.cpp, .hpp

3. How to use

  • Example: The sample_components.hpp in the s2e-core/simulation_sample/spacecraft/ is helpful to know how to use the feature.
  • Make a component class that inherits the Component class.
    • The Component class has the PowerPort class as a member and controls the component's action according to the electrical power switches.
  • Make an instance of PowerControlUnit and connect the power port.
    • The PowerControlUnit base class has a member of the map of the PowerPort class and manages the port id and connection of the PowerPort.
    • Users can make their PCU by inheriting the PowerControlUnit base class and can control the power switching in the MainRoutine function.
    pcu_ = new PowerControlUnit(clock_gen);
pcu_->ConnectPort(0, 0.5, 3.3, 0.3);
  • Make an instance of the components with the connected PowerPort. 
    obc_ = new OnBoardComputer(1, clock_gen, pcu_->GetPowerPort(0));
  • Control the power switches by using the PowerControlUnit.
    • The default setting of the power switch is off, so users need to power on the port to execute the MainRoutine of the components.
    pcu_->GetPowerPort(0)->SetVoltage(3.3);
  • Note: The virtual power port is created when users make an instance of the Component class and its subclasses without the PowerPort information. The virtual port has a minus value port ID, and the switch state is originally ON, but the consumed power is zero.

2. Explanation of Algorithm

1. SetVoltage

1. overview

  • This function is a setter function of the supply voltage to the power port.
  • Users can control the power switch by using this function.

2. inputs and outputs

  • input: supply voltage to the port
  • output: switch state of the port

3. algorithm

  • After the voltage is set, the Update function is called to check that the supply voltage is enough to turn on the component.

4. note: N/A

1. Update

1. overview

  • This is an update function of the switch state and the consumed current.
  • This function also has an over-current protection feature.

2. inputs and outputs

  • input: N/A (members of the class)
  • output: switch state of the port

3. algorithm

  • When the supply voltage is larger than the kMinimumVoltage of the component, the switch state becomes true, and the consumed current is calculated as the following equation.
$$I = P/V$$
  • The P is the assumed_power_consumption, and users can set the value with the SetAssumedPowerConsumption function.
  • If the calculated current consumption is larger than the kCurrentLimit, the over-current protection feature is executed and turning the switch off.

4. note: N/A

3. Results of verifications

N/A

4. References

N/A