c4dynamics.sensors.navigation.imu.measure

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c4dynamics.sensors.navigation.imu.measure#

imu.measure(rb: rigidbody, t: float = -1, store: bool = False)[source]#

Measures body rates and specific acceleration of a rigid body.

If store = True, the method stores the measured sample [ax, ay, az, p, q, r] along with a timestamp (t = -1 by default, if not provided otherwise).

Parameters:

  • rb (rigidbody) – A rigidbody object (or any 12-variable state object using the same [x, y, z, vx, vy, vz, phi, theta, psi, p, q, r] ordering) providing the true reference state for the sample.

  • t (float, optional) – Timestamp [seconds]. Defaults -1.

  • store (bool, optional) – A flag indicating whether to store the measured values. Defaults False.

Returns:

out (tuple) – Accelerations and rates, (ax, ay, az, p, q, r), [m/s², m/s², m/s², rad/s, rad/s, rad/s].

Note

The accelerometer’s inertial term requires a previous sample. As measure keeps that sample internally (there’s no x_true_prev argument to pass), the very first call after construction reports the gravity-projection term alone.

Example

measure in a program simulating an imu riding a rigid body through a short maneuver, storing the samples for later use:

>>> import c4dynamics as c4d
>>> import numpy as np
>>> np.random.seed(321)
>>> rb = c4d.rigidbody()
>>> imu_sensor = c4d.sensors.imu()
>>> dt = 0.005
>>> for t in np.arange(0, 1, dt):
...     rb.inteqm(np.zeros(3), np.zeros(3), dt) 
...     imu_sensor.measure(rb, t = t, store = True) 
...     rb.store(t)
>>> imu_sensor.data('p')[1].shape
(200,)
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