SciPy-Simulator

For the last few weeks I have been working on a Simulink / Labview / Ptolemy II like program for modelling... all sorts of stuff!! I am interested in modeling with different systems of computation, and of course some engineering problems, mechanical and electrical control etc. Ptolemey II is an open source java based system which a whole lot of people from Berkley have been working on for a number of years - I am not trying to match what they have - or get anywhere near the breadth that the commercial products Simulink and Labview have. But I do think something useful is very achievable - and of course leveraging what I can from Ptolemy II and basing mine on Python - heavily using SciPy, NumPy and MatPlotLib.

So far I have been working on the semantics - in essence creating a new language for defining models by using blocks (or Actors) that carry out a very specific function. An example actor might be a Ramp Source or a Sin Function. Each of these actors run in their own thread and communicate via dedicated Channels - which are based on the thread safe fifo queue implementation in the Python standard library. These base level actors can be composed together to create models, which are also actors in their own right - running in their own thread with all communication occurring through input and output channels.

The final goal is to have a visual interface - drag and drop blocks around, then connect up the model with channels. For now the whole thing is code based, so one of the more complicated models I have made is a simple pulse width modulator generator.

Here is the full code that defines and runs the model:

'''
Created on 13/12/2009

@author: brian
'''


from models.actors import Plotter, Ramp, Summer, Copier, Sin, GreaterThan, Subtractor, Constant, PassThrough
from models import CTSinGenerator
import matplotlib.pyplot as plt
from models.actors.Actor import MakeChans

import logging
logging.basicConfig(level=logging.INFO)
logging.info("Logger enabled")


def run_multi_sum():
    '''
    This example connects 3 sources ( 2 ramps and a random) to a summer block
    The final output AND one of the ramps are dynamically plotted.
    
    The components are all generating the same sequence of tags so are always
    synchronised
    '''
    sim_time = 0.02
    sim_res = 10000
    
    wire_names = ('ramp',
                  'sin',
                  'const_offset',
                  'offset_sin',
                  'ramp_probe',
                  'ramp_plot',
                  'offset_sin_probe',
                  'sin_plot',
                  'diff',
                  'pwm_bool',
                  'on_value',
                  'off_value',
                  'pwm_value'
                  )
    raw_wires = MakeChans(len(wire_names))
    
    wires = dict(zip( wire_names, raw_wires ))
    
    ramp_src = Ramp(wires['ramp_probe'], freq=500, simulation_time=sim_time, resolution=sim_res)
    sin_src = CTSinGenerator(wires['sin'], amplitude=0.5, freq=50.0, phi=0.0, timestep=1.0/sim_res, simulation_time=sim_time)
    const_src = Constant(wires['const_offset'], 0.5, resolution=sim_res, simulation_time=sim_time)
    
    offset_sin_sum = Summer([wires['sin'], wires['const_offset'] ], wires['offset_sin_probe'])
    
    ramp_cloning_probe = Copier(wires['ramp_probe'], [wires['ramp'], wires['ramp_plot']])
    ramp_plotter = Plotter(wires['ramp_plot'])
    
    sin_cloning_probe = Copier(wires['offset_sin_probe'], [wires['offset_sin'], wires['sin_plot']])
    sin_plotter = Plotter(wires['sin_plot'])

    # Output = sin - ramp
    subtractor = Subtractor(wires['offset_sin'], wires['ramp'], wires['diff'])

    # Want to see when that is > 0
    comparison = GreaterThan(wires['diff'], wires['pwm_bool'], threshold=0.0, boolean_output=True)
    if_device = PassThrough(wires['pwm_bool'], wires['on_value'], wires['pwm_value'], else_data_input=wires['off_value'])
    output_value_on = Constant(wires['on_value'], 1.0, resolution=sim_res, simulation_time=sim_time)
    output_value_off = Constant(wires['off_value'], 0.0, resolution=sim_res, simulation_time=sim_time)
    
    pwm_plotter = Plotter(wires['pwm_value'])
    
    components = [ramp_src, 
                  sin_src,
                  const_src,
                  offset_sin_sum,
                  ramp_cloning_probe, 
                  ramp_plotter, 
                  sin_cloning_probe, 
                  sin_plotter, 
                  subtractor,
                  comparison,
                  if_device,
                  output_value_on,
                  output_value_off,
                  pwm_plotter
                  ]

    logging.info("Starting simulation")
    [component.start() for component in components]
        
    logging.debug("Finished starting actors")

    logging.info('The program will stay "running" while the plot is open')
    plt.show()   

    [component.join() for component in components]
        

    logging.debug("Finished running simulation")
    

if __name__ == '__main__':
    run_multi_sum()

And here is the output:

This relatively simple model has 15 threads, and takes no time at all to run. There is still a long way to go, but if you are interested check out the project homepage on google code: http://scipy-sim.googlecode.com
Or clone the source directly with: hg clone https://scipy-sim.googlecode.com/hg/ scipy-sim