-rootlocus

This is a Dash application to plot interactive root locus for a given open loop transfer function. Some code from (https://github.com/kevinzakka/root-locus) was reused.

How to use

Numerator and denominator of the transfer function can be parsed directly from string representation of polinomial expression with parse_polynomial(expression) function. This function converts string representations to 1D numpy array of polynomial coefficients which can be directy provided to transfer_function(numerator, denominator). Then root_locus() function plots the root locus and returns plotly figure. Example:

  num = parse_polynomial('(x^2 + 2)*(x)')
  denom = parse_polynomial('x**3 - 2 + 3*x')
  
  GH = transfer_function(num, denom)

  # create a list of evenly spaced gains
  gains = np.linspace(0.0, 100.0, num=1000)
  
  fig = root_locus(GH, gains)
  fig.write_html('tmp.html', auto_open=True)

App

App requires user to input some initial boundaries for axes but after plotting, the plot can be browsed without the boundaries. Maximum gain value and the spacing between gain values can also be specified. App

Considerations

1. for some expressions plotted traces can get mixed up into each other, although, roots are still correct. try for num = [1, 4, 0]; denom = [1, 2, 0, 4, 0].
2. currently, I can't find any easy, robust method for converting sympy polynomial ito a pretty string.