149 lines
4.7 KiB
Python
149 lines
4.7 KiB
Python
#!/usr/bin/env python
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'''
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fit best estimate of magnetometer offsets, trying to take into account motor interference
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'''
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from __future__ import print_function
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from builtins import range
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from argparse import ArgumentParser
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parser = ArgumentParser(description=__doc__)
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parser.add_argument("--no-timestamps",dest="notimestamps", action='store_true', help="Log doesn't have timestamps")
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parser.add_argument("--condition",dest="condition", default=None, help="select packets by condition")
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parser.add_argument("--noise", type=float, default=0, help="noise to add")
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parser.add_argument("logs", metavar="LOG", nargs="+")
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args = parser.parse_args()
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from pymavlink import mavutil
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from pymavlink.rotmat import Vector3
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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 * args.noise
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def select_data(data):
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ret = []
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counts = {}
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for d in data:
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(mag,motor) = d
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key = "%u:%u:%u" % (mag.x/20,mag.y/20,mag.z/20)
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if key in counts:
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counts[key] += 1
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else:
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counts[key] = 1
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if counts[key] < 3:
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ret.append(d)
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print(len(data), len(ret))
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return ret
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def radius(d, offsets, motor_ofs):
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'''return radius give data point and offsets'''
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(mag, motor) = d
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return (mag + offsets + motor*motor_ofs).length()
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def radius_cmp(a, b, offsets, motor_ofs):
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'''return radius give data point and offsets'''
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diff = radius(a, offsets, motor_ofs) - radius(b, offsets, motor_ofs)
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if diff > 0:
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return 1
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if diff < 0:
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return -1
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return 0
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def sphere_error(p, data):
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x,y,z,mx,my,mz,r = p
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ofs = Vector3(x,y,z)
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motor_ofs = Vector3(mx,my,mz)
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ret = []
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for d in data:
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(mag,motor) = d
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err = r - radius((mag,motor), ofs, motor_ofs)
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ret.append(err)
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return ret
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def fit_data(data):
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from scipy import optimize
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p0 = [0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0]
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p1, ier = optimize.leastsq(sphere_error, p0[:], args=(data))
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if not ier in [1, 2, 3, 4]:
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raise RuntimeError("Unable to find solution")
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return (Vector3(p1[0], p1[1], p1[2]), Vector3(p1[3], p1[4], p1[5]), p1[6])
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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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mlog = mavutil.mavlink_connection(filename, notimestamps=args.notimestamps)
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data = []
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last_t = 0
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offsets = Vector3(0,0,0)
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motor_ofs = Vector3(0,0,0)
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motor = 0.0
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# now gather all the data
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while True:
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m = mlog.recv_match(condition=args.condition)
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if m is None:
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break
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if m.get_type() == "PARAM_VALUE" and m.param_id == "RC3_MIN":
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rc3_min = float(m.param_value)
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if m.get_type() == "SENSOR_OFFSETS":
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# update current offsets
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offsets = Vector3(m.mag_ofs_x, m.mag_ofs_y, m.mag_ofs_z)
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if m.get_type() == "SERVO_OUTPUT_RAW":
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motor_pwm = m.servo1_raw + m.servo2_raw + m.servo3_raw + m.servo4_raw
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motor_pwm *= 0.25
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rc3_min = mlog.param('RC3_MIN', 1100)
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rc3_max = mlog.param('RC3_MAX', 1900)
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motor = (motor_pwm - rc3_min) / (rc3_max - rc3_min)
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if motor > 1.0:
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motor = 1.0
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if motor < 0.0:
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motor = 0.0
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if m.get_type() == "RAW_IMU":
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mag = Vector3(m.xmag, m.ymag, m.zmag)
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# add data point after subtracting the current offsets
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data.append((mag - offsets + noise(), motor))
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print("Extracted %u data points" % len(data))
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print("Current offsets: %s" % offsets)
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data = select_data(data)
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# do an initial fit with all data
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(offsets, motor_ofs, field_strength) = fit_data(data)
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for count in range(3):
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# sort the data by the radius
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data.sort(lambda a,b : radius_cmp(a,b,offsets,motor_ofs))
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print("Fit %u : %s %s field_strength=%6.1f to %6.1f" % (
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count, offsets, motor_ofs,
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radius(data[0], offsets, motor_ofs), radius(data[-1], offsets, motor_ofs)))
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# discard outliers, keep the middle 3/4
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data = data[len(data)/8:-len(data)/8]
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# fit again
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(offsets, motor_ofs, field_strength) = fit_data(data)
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print("Final : %s %s field_strength=%6.1f to %6.1f" % (
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offsets, motor_ofs,
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radius(data[0], offsets, motor_ofs), radius(data[-1], offsets, motor_ofs)))
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print("mavgraph.py '%s' 'mag_field(RAW_IMU)' 'mag_field_motors(RAW_IMU,SENSOR_OFFSETS,(%f,%f,%f),SERVO_OUTPUT_RAW,(%f,%f,%f))'" % (
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filename,
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offsets.x,offsets.y,offsets.z,
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motor_ofs.x, motor_ofs.y, motor_ofs.z))
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total = 0.0
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for filename in args.logs:
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magfit(filename)
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