mirror of https://github.com/ArduPilot/ardupilot
150 lines
4.6 KiB
Python
Executable File
150 lines
4.6 KiB
Python
Executable File
#!/usr/bin/env python
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''' fit best estimate of magnetometer offsets from ArduCopter flashlog
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using the algorithm from Bill Premerlani
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'''
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import sys
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# command line option handling
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from optparse import OptionParser
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parser = OptionParser("magfit_flashlog.py [options]")
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parser.add_option("--verbose", action='store_true', default=False, help="verbose offset output")
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parser.add_option("--gain", type='float', default=0.01, help="algorithm gain")
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parser.add_option("--noise", type='float', default=0, help="noise to add")
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parser.add_option("--max-change", type='float', default=10, help="max step change")
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parser.add_option("--min-diff", type='float', default=50, help="min mag vector delta")
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parser.add_option("--history", type='int', default=20, help="how many points to keep")
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parser.add_option("--repeat", type='int', default=1, help="number of repeats through the data")
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(opts, args) = parser.parse_args()
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from pymavlink.rotmat import Vector3
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if len(args) < 1:
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print("Usage: magfit_flashlog.py [options] <LOGFILE...>")
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sys.exit(1)
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def noise():
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'''a noise vector'''
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from random import gauss
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v = Vector3(gauss(0, 1), gauss(0, 1), gauss(0, 1))
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v.normalize()
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return v * opts.noise
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def find_offsets(data, ofs):
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'''find mag offsets by applying Bills "offsets revisited" algorithm
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on the data
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This is an implementation of the algorithm from:
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http://gentlenav.googlecode.com/files/MagnetometerOffsetNullingRevisited.pdf
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'''
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# a limit on the maximum change in each step
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max_change = opts.max_change
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# the gain factor for the algorithm
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gain = opts.gain
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data2 = []
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for d in data:
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d = d.copy() + noise()
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d.x = float(int(d.x + 0.5))
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d.y = float(int(d.y + 0.5))
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d.z = float(int(d.z + 0.5))
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data2.append(d)
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data = data2
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history_idx = 0
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mag_history = data[0:opts.history]
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for i in range(opts.history, len(data)):
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B1 = mag_history[history_idx] + ofs
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B2 = data[i] + ofs
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diff = B2 - B1
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diff_length = diff.length()
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if diff_length <= opts.min_diff:
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# the mag vector hasn't changed enough - we don't get any
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# information from this
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history_idx = (history_idx+1) % opts.history
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continue
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mag_history[history_idx] = data[i]
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history_idx = (history_idx+1) % opts.history
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# equation 6 of Bills paper
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delta = diff * (gain * (B2.length() - B1.length()) / diff_length)
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# limit the change from any one reading. This is to prevent
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# single crazy readings from throwing off the offsets for a long
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# time
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delta_length = delta.length()
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if max_change != 0 and delta_length > max_change:
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delta *= max_change / delta_length
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# set the new offsets
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ofs = ofs - delta
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if opts.verbose:
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print(ofs)
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return ofs
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def plot_corrected_field(filename, data, offsets):
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f = open(filename, mode='w')
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for d in data:
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corrected = d + offsets
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f.write("%.1f\n" % corrected.length())
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f.close()
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def magfit(logfile):
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'''find best magnetometer offset fit to a log file'''
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print("Processing log %s" % filename)
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# open the log file
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flog = open(filename, mode='r')
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data = []
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data_no_motors = []
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mag = None
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offsets = None
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# now gather all the data
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for line in flog:
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if not line.startswith('COMPASS,'):
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continue
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line = line.rstrip()
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line = line.replace(' ', '')
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a = line.split(',')
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ofs = Vector3(float(a[4]), float(a[5]), float(a[6]))
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if offsets is None:
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initial_offsets = ofs
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offsets = ofs
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motor_ofs = Vector3(float(a[7]), float(a[8]), float(a[9]))
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mag = Vector3(float(a[1]), float(a[2]), float(a[3]))
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mag = mag - offsets
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data.append(mag)
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data_no_motors.append(mag - motor_ofs)
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print("Extracted %u data points" % len(data))
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print("Current offsets: %s" % initial_offsets)
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# run the fitting algorithm
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ofs = initial_offsets
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for r in range(opts.repeat):
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ofs = find_offsets(data, ofs)
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plot_corrected_field('plot.dat', data, ofs)
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plot_corrected_field('initial.dat', data, initial_offsets)
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plot_corrected_field('zero.dat', data, Vector3(0,0,0))
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plot_corrected_field('hand.dat', data, Vector3(-25,-8,-2))
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plot_corrected_field('zero-no-motors.dat', data_no_motors, Vector3(0,0,0))
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print('Loop %u offsets %s' % (r, ofs))
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sys.stdout.flush()
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print("New offsets: %s" % ofs)
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total = 0.0
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for filename in args:
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magfit(filename)
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