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https://github.com/AtsushiSakai/PythonRobotics.git
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139 lines
3.4 KiB
Python
139 lines
3.4 KiB
Python
"""
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Object shape recognition with rectangle fitting
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author: Atsushi Sakai (@Atsushi_twi)
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"""
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import matplotlib.pyplot as plt
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import math
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import random
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import numpy as np
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show_animation = True
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def circle_fitting(x, y):
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"""
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Circle Fitting with least squared
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input: point x-y positions
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output cxe x center position
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cye y center position
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re radius of circle
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error: prediction error
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"""
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sumx = sum(x)
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sumy = sum(y)
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sumx2 = sum([ix ** 2 for ix in x])
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sumy2 = sum([iy ** 2 for iy in y])
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sumxy = sum([ix * iy for (ix, iy) in zip(x, y)])
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F = np.array([[sumx2, sumxy, sumx],
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[sumxy, sumy2, sumy],
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[sumx, sumy, len(x)]])
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G = np.array([[-sum([ix ** 3 + ix * iy ** 2 for (ix, iy) in zip(x, y)])],
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[-sum([ix ** 2 * iy + iy ** 3 for (ix, iy) in zip(x, y)])],
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[-sum([ix ** 2 + iy ** 2 for (ix, iy) in zip(x, y)])]])
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T = np.linalg.inv(F).dot(G)
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cxe = float(T[0] / -2)
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cye = float(T[1] / -2)
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re = math.sqrt(cxe**2 + cye**2 - T[2])
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error = sum([np.hypot(cxe - ix, cye - iy) - re for (ix, iy) in zip(x, y)])
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return (cxe, cye, re, error)
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def get_sample_points(cx, cy, cr, angle_reso):
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x, y, angle, r = [], [], [], []
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# points sampling
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for theta in np.arange(0.0, 2.0 * math.pi, angle_reso):
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nx = cx + cr * math.cos(theta)
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ny = cy + cr * math.sin(theta)
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nangle = math.atan2(ny, nx)
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nr = math.hypot(nx, ny) * random.uniform(0.95, 1.05)
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x.append(nx)
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y.append(ny)
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angle.append(nangle)
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r.append(nr)
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# ray casting filter
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rx, ry = ray_casting_filter(x, y, angle, r, angle_reso)
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return rx, ry
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def ray_casting_filter(xl, yl, thetal, rangel, angle_reso):
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rx, ry = [], []
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rangedb = [float("inf") for _ in range(
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int(math.floor((math.pi * 2.0) / angle_reso)) + 1)]
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for i in range(len(thetal)):
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angleid = math.floor(thetal[i] / angle_reso)
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if rangedb[angleid] > rangel[i]:
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rangedb[angleid] = rangel[i]
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for i in range(len(rangedb)):
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t = i * angle_reso
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if rangedb[i] != float("inf"):
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rx.append(rangedb[i] * math.cos(t))
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ry.append(rangedb[i] * math.sin(t))
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return rx, ry
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def plot_circle(x, y, size, color="-b"):
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deg = list(range(0, 360, 5))
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deg.append(0)
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xl = [x + size * math.cos(np.deg2rad(d)) for d in deg]
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yl = [y + size * math.sin(np.deg2rad(d)) for d in deg]
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plt.plot(xl, yl, color)
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def main():
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# simulation parameters
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simtime = 15.0 # simulation time
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dt = 1.0 # time tick
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cx = -2.0 # initial x position of obstacle
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cy = -8.0 # initial y position of obstacle
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cr = 1.0 # obstacle radious
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theta = np.deg2rad(30.0) # obstacle moving direction
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angle_reso = np.deg2rad(3.0) # sensor angle resolution
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time = 0.0
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while time <= simtime:
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time += dt
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cx += math.cos(theta)
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cy += math.cos(theta)
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x, y = get_sample_points(cx, cy, cr, angle_reso)
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ex, ey, er, error = circle_fitting(x, y)
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print("Error:", error)
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if show_animation:
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plt.cla()
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plt.axis("equal")
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plt.plot(0.0, 0.0, "*r")
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plot_circle(cx, cy, cr)
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plt.plot(x, y, "xr")
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plot_circle(ex, ey, er, "-r")
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plt.pause(dt)
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print("Done")
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if __name__ == '__main__':
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main()
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