reilleya/openMotor

Automatic Motor Optimization

Opened this issue · 3 comments

mvccogo commented

It would be interesting to have an option in the "Tools" dropdown list to automatically find a suitable motor given the parameters proposed by the user. I've done a similar thing using scipy.optimize, and some of you may be familiar with Matlab's fminsearch/fmincon.

The parameters given as constraints are:

  • Mean Pressure: average pressure developed after a simulation
  • Port ratio: set minimum Port/Throat ratio to reduce effects of erosive burning
  • Peak Pressure: peak pressure developed after a simulation
  • Kn variation: maximum allowed Kn variation throughout the burn
  • Maximum Mass Flux: reduce effects of erosive burning

The parameters given as input/goals are:

  • Total impulse

The parameters given as bounds are:

  • Min and Max outer diameter (BATES)
  • Min and Max inner diameter (BATES)
  • Min and Max length (BATES)

The output design parameters are:

  • Number of grains
  • Length of grains
  • Inner and outer diameter of grains
  • Nozzle configuration

Python code as a concept:

def optimize_for_impulse():
    constraint = [{'type' : 'ineq', 'fun' : restraint_mean_pressure},              
                  {'type' : 'ineq', 'fun' : restraint_port_ratio},                    
                  {'type' : 'ineq', 'fun' : restraint_peak_pressure},               
                  {'type' : 'ineq', 'fun' : restraint_kn_variation},                  
                  {'type' : 'ineq', 'fun' : restraint_mass_flux}]                     
    bounds = ((0.005, 0.01), (0.05, 0.225), (0.003, 0.015))                    
    it = 0
    while (True):
        initial_guess = [random.uniform(0.005, 0.03664*0.6), random.uniform (0.1, 0.225), random.uniform(0.005, 0.015)]
        a = optimize.minimize(optimize_total_impulse, initial_guess, bounds=bounds, constraints=constraint ) 
        if a.success and a.fun < 10:
            return a.x, it
        elif it > 500:
            print("No suitable configuration was found in ", it, "iterations.")
            break
        it += 1
reilleya commented

This would be fun to play around with! I still use openMotor fairly often but I don't have too much time to work on it. I would be able to find time to review a PR for this if you/someone sent one in, or will keep it in mind for when I someday start on a v0.6.0 if not.

mvccogo commented

Sure, no problem. I'm also short on time, but I thought we should have an issue dedicated to this. I'll try building oM first, get familiar with the program then take a stab at it later on. Thanks, Andrew.

benrussell11 commented