(3) Configuring a Power Bus

Designing the Network

The Power Bus allows for a network of power nodes on an electrical power system (EPS) to be designed and connected. The power bus provides the backbone for a power network and can allow components to draw and provide power to and from the central battery unit. A power bus allows for simple circuitry designs, with both parallel and series power networks. For this tutorial, the four power components (2 solar panels, battery, and sink) will be connected in the following configuration:

WARNING

By default, the solar panels have a behavior (Is Forward Biased) set to be on which will enable a diode-like behavior on the solar panel. This prevents the current from flowing back into the solar panel by increasing the internal resistance to a large value when there is no power. This feature will be changed in future versions with the introduction of the diode component.

Here, the two solar panels provide power to the battery in series, but in parallel with the battery, each providing 12V of power to the sink node. The battery will be providing an additional 12V of power to the nodes on the right-hand side of the battery. These two components, the switch and the power load for the camera, will receive 24V of power when the circuit is closed and are configured in a series circuit. This is a simple circuit design and can be implemented with the power bus.

NOTE

For the power bus, the connection from the end of the component lines back to the positive end of the solar panels can be imagined and is assumed to be connected to the ground (by default, although this implementation can be configured).

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Adding the Power Bus

The Power Bus component must be created on the spacecraft. However, a power bus is a behavior. Behaviors are different to objects in the Zendir simulation architecture as they don’t have a position. Behaviors are commonly used for flight software and systems onboard spacecraft that can’t be represented in real life as a physical object. Instead, the Create Behaviour node can be used here.

NOTE

When unsure which object is available on Create Behaviour or Create Object, use one of the nodes and attempt to find the class. It is likely available on the other node if it does not exist on one of the options.

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Connecting the Nodes

The power bus contains a connect function for connecting the different power nodes. These nodes are defined by what kind of components are required to be connected. There are four general types of power components:

• Source: A power source that can provide a charge to the battery, such as solar panels.
• Storage: A battery that can contain the power in the system and both distribute it and charge from power sources.
• Sinks: A power sink can draw power by consuming current and/or voltage from the network based on the network diagram.
• Component: A power component that can draw current and voltage from the power network and includes switches and current limiters.

Each of the components can be attached in this way. The two solar panels need to be connected to the battery. To grab the solar panels, use the Get Children function with the solar panel class. This will return an array of solar panels (of which there are 2). Make sure to select Recurse to true, as this will ensure it checks the chassis for the solar panel objects. Then, assuming there are two solar panels. use the Connect function on the power bus to create a wire between the solar panel positive output and the other solar panel negative output.

NOTE

By default, the connect function will assume the positive terminal (output) will connect to the negative terminal (input) of the component. If the terminals should be different, use the Connect Terminals function.

Next, the second solar panel must be connected with a wire to the power sink. This can be done using the same function.

NOTE

A wire is a component that is modelled by a 0V voltage source with no resistance. Essentially, wires are built in such a way that they do not draw current or voltage across their nodes.

Finally, the battery must also be connected to the power sink, in parallel to the solar panels.

The full network on the power bus will look like the following:

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Testing the Network

Although the switch and sink should be doing nothing to the power network, the solar panels should be providing power to the battery. This can be tested and checked by printing out the charge of the battery to the screen and running the simulation, on the event tick.

The battery charge of the spacecraft should appear to increase over time by looking at the text printed in text on the left-hand side.

WARNING

If the battery is still not increasing in charge, ensure that the Configure Power Components function is connected to the Begin Play event.