Usage of Filtered Orientation and Original Acceleration

[tiandaji]

Hello @arunvydhya
I am using xsens G710-2A8G4, and I would like to know if it is possible to obtain both filtered orientation and original acceleration using your python node. I was able to get rostopic echo /mti/sensor/imu with the output like this:

header:
seq: 3010
stamp:
secs: 1540801612
nsecs: 818232059
frame_id: "xsens"
orientation:
x: 0.0150714591146
y: -0.00283857248724
z: 0.968756854534
w: 0.247538030148
orientation_covariance: [0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0]
angular_velocity:
x: 0.0
y: 0.0
z: 0.0
angular_velocity_covariance: [0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0]
linear_acceleration:
x: 0.0
y: 0.0
z: 0.0
linear_acceleration_covariance: [0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0]

However, whichever parameter I chose (rosed xsens_driver xsens.yaml, to change the output mode among 1, 2, 3) in the xsens.yaml, the accelerations remained zeros. Will you please give me some indications?

[tiandaji]

Furthermore, there are no output in output mode 3 for topic /mti/sensor/imu, which means even if the topic has output, the result will not be processed by the filter and remain original, which is not what I want. Thanks very much for all kinds of help @StevenXsens @arunvydhya

[Steven-GH]

Hello Tiandaji,

The ROS driver is merely a starting point for your application. It currently has three output data modes, available through the yaml configuration file:

1. (sensor data): this configures your MTi to output e.g. dq, dv and magnetic field data.
2. (sensor data w/ rate quantities): this configures your MTi to output e.g. acceleration and rate of turn data.
3. (filter estimates): this configures your MTi to output e.g. Euler angles, position and velocity.

Next, there are several rostopic echo combinations available to visualize the data outputs. For example:

• /mti/sensor/imu will print quaternions, angular velocity and linear acceleration (if available)
• /mti/filter/orientation will print euler angles (if available)

In order to change the behaviour or add output modes, you can modify mtnode.py and mtdevice.py in the src folder to your needs.

[hittingray]

Hello @tiandaji

I know you asked a month ago, but I performed the modifications that Steven described above today. The modifications below should give you the outputs as if both modes 2 and 3 are enabled. If you have not been able to get it working, here is what you need:

The line numbers below assume you have unedited files thus far:

In mtnode.py, on line 73:

Change if output_mode not in [1, 2, 3]: to if output_mode not in [1, 2, 3, 4]:

In mtdevice.py, in the area of line 447, add the following lines under the section for your device:

elif mtiMode == 4:
    print "Custom"
    data = mStf+mImuGyr+mImuAcc+mImuMag+mSw+mOrientationQuat+mStf+mSw+mOrientation

If you are using a G710, this should be the first block.

---

Edit:

For my use case, I wanted to see the quaternions and Euler angles simultaneously. I realised the above modification will only show whichever of the two is on the end of the list. To show both:

In mtnode.spin_once(), under if orient_data:, change the elif to if.

In mtdevice.parsedata(), in the while data: loop, under elif group == XDIGroup.OrientationData: add

if 'Orientation Data' in output:
    o = output['Orientation Data']
else:
    o = {}

and change the function call to:

output['Orientation Data'] = parse_orientation_data(data_id, content, ffmt, o)

Consequently, redefine the first couple lines of parse_orientation_data() as:

def parse_orientation_data(data_id, content, ffmt, o):
	# o = {}

---

Edit 2:

I also neglected to mention in mtnode.spin_once(), the else: under if orient_data: needs to be changed to if not pub_ori and not pub_imu: to prevent an exception being raised when there is no roll/pitch/yaw data.