Sine Generator¶

A very simple example usage of the framework is to create a CBD model that implements the equation \(y = sin(t)\), where \(t\) is the simulation time and \(y\) an output signal we’re interested in.

Luckily, the standard library provides some functionalities to help us solve this problem. Let’s import three blocks:

from CBD.Core import *   # To prevent circular dependency
from CBD.lib.std import TimeBlock, GenericBlock

The CBD.lib.std.TimeBlock will output the current simulation time every delta timeunits. This block will be used to obtain the \(t\) variable. The CBD.lib.std.GenericBlock is a generic interface to Python’s math module. We will use this block to implement the sine function itself.

Next, we need a container to group these blocks in. This is done in the hierarchical CBD.Core.CBD class. Let’s call this “grouping” block SinGen and give it a single output port, named OUT1.

class SinGen(CBD):
    def __init__(self, name="SinGen"):
        CBD.__init__(self, name, input_ports=[], output_ports=["OUT1"])

        # Add the 't' parameter
        # Let's call it 'time'
        self.addBlock(TimeBlock("time"))

        # Add the block that computes the actual sine function
        # Let's call it 'sin'
        self.addBlock(GenericBlock("sin", block_operator="sin"))

        # Connect them together
        self.addConnection("time", "sin", output_port_name='OUT1',
                                            input_port_name='IN1')

        # Connect the output port
        self.addConnection("sin", "OUT1", output_port_name='OUT1')


sinGen = SinGen("SinGen")

Notice how this is semantically equivelent to:

from CBD.Core import CBD

sinGen = CBD("SinGen", [], ["OUT1"])

# Add the time, just like above
sinGen.addBlock(TimeBlock("time"))

sinGen.addBlock(GenericBlock("sin", block_operator="sin"))
sinGen.addConnection("time", "sin", output_port_name='OUT1',
                                    input_port_name='IN1')
sinGen.addConnection("sin", "OUT1", output_port_name='OUT1')

If we now want to simulate our model for 20 seconds (of simulation-time), we can simply do:

from CBD.simulator import Simulator

sim = Simulator(sinGen)
# The termination time can be set as argument to the run call
sim.run(20.0)

Next, we would like to obtain the accumulated simulation data on the OUT1 output port of the sinGen block, which can be plotted against their iteration (which is equivalent to the time in this case).

data = sinGen.getSignalHistory('OUT1')
x, y = [x for x, _ in data], [y for _, y in data]

Now, this is obviously not the sine wave we know and love. This is because our simulator only computes at 0, 1, 2, 3… seconds, but not in-between. This can be changed by altering the time delta before the start of a simulation:

sim.setDeltaT(0.1)

Now, we interpolate the sine-wave every 10th of a second, which looks much better:

Sine Generator¶

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