I cannot get acceleration data from /hedge_imu_fusion topic

[kazu]

Hello,
We are trying to get acceleration data from /hedge_imu_fusion topic (using ros_marvelmind_package), but all acceleration data and velocity data we got were 0.
We could only get quarternion data and timestamp.

The result of

Code: Select all

rostopic echo /hedge_imu_fusion

is like

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timestamp_ms: 7952609
x_m: 0.0
y_m: 0.0
z_m: 0.0
qw: 0.526
qx: -0.0637
qy: 0.1364
qz: -0.837
vx: 0.0
vy: 0.0
vz: 0.0
ax: 0.0
ay: 0.0
az: 0.0

We did accelerometer calibration by Dashboard, enabled Processed IMU data, and enabled some other column seemed to be related with IMU,
but the results were the same.
I would appreciate it if you could tell me what to do or check nextly.

[smoker77]

Hello,
I current software version for Mini-Rx, Super-Beacons and Industrial Super-Beacons you can get raw IMU data, including acceleration. In IMU fusion data we currently provide quaternion (orientation) data. Fused acceleration, speed and location will be provided in future versions.

[kazu]

Thanks for your reply.
Do you mean that we can get acceleration data from /hedge_imu_raw topic?
/hedge_imu_raw topic has not been published yet, but do we need some setting from dashboard to publish the topic?

[smoker77]

Hello,

Yes, you should enable 'Raw inertial sensors data' option for mobile beacon in dashboard as shown on the screenshot.

[kazu]

Hello,

Thanks for your support.
We could get /hedge_imu_raw topic and acceleration data.
May I ask you another question about the unit?

When we did $rostopic echo /hedge_imu_raw ,
the outputs were like below.

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timestamp_ms: 63177
acc_x: -121
acc_y: -3
acc_z: 1216
gyro_x: 4325
gyro_y: -2248
gyro_z: 1664
compass_x: 0
compass_y: 0
compass_z: 0
---

I suppose the unit of acceleration z would be 12.16[m/s^2] in this case.
Using the same scale factor, I believe acc_x would be -1.21[m/s^2] and acc_y would be -0.03[m/s^2] but is this correct?
About gyros, I have no idea with the units but how is it like?
Maybe 43.25[degree/sec] for gyro_x?

[smoker77]

Hello,

The unit of accelerometer data in /hedge_imu_raw topic is mg, so value 1000 means 1 g.
Note the data not calibrated, so you can have raw gravity value more than 1 g.

Resolution of LSB for gyro data is 0.0175 dps, so value 1000 means 17.5 degrees per second.

You can find these units in the section 1.3 of the protocol:
https://marvelmind.com/pics/marvelmind_ ... rfaces.pdf