dnda.py

'''
Stanley Bak
F16 GCAS in Python
dnda function
'''

import numpy as np
from aerobench.util import fix, sign

def dnda(alpha, beta):
    'dnda function'

    a = np.array([[.001, -.027, -.017, -.013, -.012, -.016, .001, .017, .011, .017, .008, .016], \
        [.002, -.014, -.016, -.016, -.014, -.019, -.021, .002, .012, .016, .015, .011], \
        [-.006, -.008, -.006, -.006, -.005, -.008, -.005, .007, .004, .007, .006, .006], \
        [-.011, -.011, -.010, -.009, -.008, -.006, .000, .004, .007, .010, .004, .010], \
        [-.015, -.015, -.014, -.012, -.011, -.008, -.002, .002, .006, .012, .011, .011], \
        [-.024, -.010, -.004, -.002, -.001, .003, .014, .006, -.001, .004, .004, .006], \
        [-.022, .002, -.003, -.005, -.003, -.001, -.009, -.009, -.001, .003, -.002, .001]], dtype=float).T

    s = .2 * alpha
    k = fix(s)

    if k <= -2:
        k = -1

    if k >= 9:
        k = 8

    da = s - k
    l = k + fix(1.1 * sign(da))
    s = .1 * beta
    m = fix(s)
    if m <= -3:
        m = -2

    if m >= 3:
        m = 2

    db = s - m
    n = m + fix(1.1 * sign(db))
    l = l + 3
    k = k + 3
    m = m + 4
    n = n + 4
    t = a[k-1, m-1]
    u = a[k-1, n-1]
    v = t + abs(da) * (a[l-1, m-1] - t)
    w = u + abs(da) * (a[l-1, n-1] - u)

    return v + (w - v) * abs(db)